WO2012002025A1 - Tunable antenna device - Google Patents

Tunable antenna device Download PDF

Info

Publication number
WO2012002025A1
WO2012002025A1 PCT/JP2011/059341 JP2011059341W WO2012002025A1 WO 2012002025 A1 WO2012002025 A1 WO 2012002025A1 JP 2011059341 W JP2011059341 W JP 2011059341W WO 2012002025 A1 WO2012002025 A1 WO 2012002025A1
Authority
WO
WIPO (PCT)
Prior art keywords
antenna device
tunable antenna
gain
frequency
loading coil
Prior art date
Application number
PCT/JP2011/059341
Other languages
French (fr)
Japanese (ja)
Inventor
常夫 江原
隆英 中島
Original Assignee
日本アンテナ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 日本アンテナ株式会社 filed Critical 日本アンテナ株式会社
Publication of WO2012002025A1 publication Critical patent/WO2012002025A1/en

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
    • H01Q5/50—Feeding or matching arrangements for broad-band or multi-band operation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/06—Details
    • H01Q9/14—Length of element or elements adjustable
    • H01Q9/145—Length of element or elements adjustable by varying the electrical length
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/30—Resonant antennas with feed to end of elongated active element, e.g. unipole

Definitions

  • the present invention relates to a tunable antenna device capable of securing antenna gain while being a miniaturized and narrowed antenna.
  • FIG. 39 shows a general equivalent circuit diagram of the miniaturized and low-profile antenna and the glass antenna whose layout is narrowed.
  • the antenna 39 includes an antenna 110 composed of a rod antenna with a reduced size and a reduced profile and a glass antenna with a narrowed layout, and the received signal received by the antenna 110 is output It is output from the terminal OUT.
  • the frequency characteristic of the impedance of the antenna device 100 is shown in the Smith chart shown in FIG. Referring to the Smith chart shown in FIG. 40, high impedance is shown in the 76 MHz-83 MHz-90 MHz band, which is the FM radio broadcast band shown by markers 1, 2 and 3, and it is difficult to extract sufficient performance. It is understood that This is because the size of the antenna device 100 and the shape such as the vehicle design, the visibility and the mounting position are limited.
  • an antenna device for a vehicle has conventionally been proposed in which an antenna substrate on which an antenna pattern is formed is erected and disposed inside an antenna case projecting at a height of 70 mm or less from the vehicle.
  • an amplifier substrate for amplifying a received signal output from the antenna substrate is accommodated in the antenna case, and the antenna pattern is provided in the broadcasting band of the FM radio between the antenna pattern and the feeding point on the antenna substrate.
  • An antenna coil for resonance is inserted.
  • the low-profile antenna pattern which is about 1/20 the length of the FM broadcast wavelength, resonates in the FM radio broadcast band.
  • the frequency characteristic of the impedance of the antenna device 101 is shown in the Smith chart shown in FIG. Referring to the Smith chart shown in FIG. 42, high impedance is shown in the vicinity of 76 MHz and 90 MHz which are considered as band edges of the broadcast band of FM radio, but low impedance is shown in the vicinity of 83 MHz of the center frequency. . Also, the antenna device 101 resonates in the vicinity of 83 MHz. Thus, although the antenna 110 alone does not resonate in the frequency band of the FM broadcast as shown in FIG. 40, by connecting the loading coil 111 in series with the antenna 110, it is possible to resonate in the frequency band of the FM broadcast become.
  • FIG. 43 shows an equivalent circuit diagram of a conventional tunable antenna device 102 that can be tuned to a frequency within the frequency band of FM broadcasting.
  • a tunable antenna device 102 shown in FIG. 43 includes a small antenna 110 and a loading coil 111-1 connected in series to the antenna 110 and having a different number of turns, and includes a loading coil 111-1 and an output terminal OUT.
  • the tuning circuit 112 is connected between them. The received signal received by the antenna 110 is output from the output terminal OUT through the tuning circuit 112.
  • the tuning circuit 112 includes two varicap diodes BD101 and BD102 connected in series in reverse polarity to the tuning coil 112a, and the positive terminal is connected to the junction of the varicap diodes BD101 and BD102 whose cathodes are connected via a resistor R100. A voltage Vt is applied. Further, a choke coil CH100 is connected between the output terminal OUT and the ground to block a high frequency (RF) signal and to ground the output terminal OUT in a DC manner. The anodes of the varicap diodes BD101 and BD102 are DC-grounded by the choke coil CH100.
  • the reverse voltage applied between the cathode and the anode of the varicap diodes BD101 and BD102 is increased, and the capacitance value of the varicap diodes BD101 and BD102 is obtained.
  • the positive voltage Vt in the tuning circuit 112 is lowered, the reverse voltage applied between the cathode and the anode of the varicap diodes BD101 and BD102 is reduced, and the capacitance value of the varicap diodes BD101 and BD102 is increased.
  • FIG. 44 a Smith chart showing the frequency characteristics of the impedance of the tunable antenna device 102 when adjusting the positive voltage Vt to make the resonant frequency of the tunable antenna device 102 about 76 MHz is shown in FIG.
  • the impedance is low in resonance approximately at 76 MHz which is the low band edge of the broadcast band of the FM radio indicated by the marker 1.
  • FIG. 46 shows a Smith chart showing the frequency characteristics of the impedance of the tunable antenna device 102 when the resonant frequency of the tunable antenna device 102 is adjusted to about 83 MHz by adjusting the positive voltage Vt.
  • the impedance is low in resonance approximately at 83 MHz, which is the center frequency of the broadcast band of the FM radio indicated by the marker 2.
  • FIG. 46 shows a Smith chart showing the frequency characteristics of the impedance of the tunable antenna device 102 when adjusting the positive voltage Vt to make the resonant frequency of the tunable antenna device 102 about 90 MHz.
  • the impedance is low in resonance approximately at 90 MHz, which is the high band edge of the broadcast band of the FM radio indicated by the marker 3.
  • the resonant frequency of the tunable antenna device 102 is increased to about 76 MHz, which is the low band edge of the broadcast band of FM radio, and about 83 MHz, which is the center frequency. 47 to 49 by comparing the frequency characteristics of the gain of the tunable antenna device 102 when the band edge is about 90 MHz with the frequency characteristics of the gain of the antenna device 101 shown in FIG. 41 where the tuning circuit 112 is omitted. Shown in.
  • FIG. 47 shows the case where the resonant frequency of the tunable antenna device 102 is about 76 MHz, and the gain of the tunable antenna device 102 shown by the marker 1 is about 2.5 dB as compared to the gain of the antenna device 101 not provided with the tuning circuit 112. It turns out that it becomes high.
  • FIG. 48 shows the case where the resonant frequency of the tunable antenna device 102 is about 83 MHz, and the gain of the tunable antenna device 102 indicated by the marker 2 is almost equal to the gain of the antenna device 101 not provided with the tuning circuit 112. It turns out that it becomes.
  • FIG. 49 shows the case where the resonant frequency of the tunable antenna device 102 is about 90 MHz, and the gain of the tunable antenna device 102 indicated by the marker 3 is about 4 as compared with the gain of the antenna device 101 not provided with the tuning circuit 112. It turns out that it is 2 dB higher.
  • the tuning circuit 112 and adjusting the positive voltage Vt applied to the tuning circuit 112 it is possible to obtain peak gain in the entire band of the FM broadcast, and gain in the broadcast band of the FM radio Can be flattened.
  • the tunable antenna device including the tuning circuit can improve the frequency characteristics of the gain, but the varicap diode forming the tuning circuit is distorted in the received signal under a strong electric field. There was a problem of causing Therefore, it is an object of the present invention to provide a tunable antenna device which secures a gain while being a miniaturized and narrowed area antenna and in which distortion does not occur under a strong electric field.
  • the tunable antenna device comprises a small antenna that does not resonate in a used frequency band alone, a loading coil connected in series to the antenna, and A tuning circuit capable of varying impedance connected between the loading coil and the output terminal; and an AGC circuit provided between a connection point between the loading coil and the tuning circuit and the ground.
  • the antenna in which the loading coil is connected in series can be resonated at a specific frequency in a used frequency band by varying the impedance of the tuning circuit, and the impedance viewed from the AGC circuit from the AGC circuit is The most important feature is that it is within about 4% of the impedance of the AGC circuit.
  • a loading coil and a tuning circuit capable of varying tuning can be provided as a miniaturized / narrowed antenna which does not resonate in the used frequency band alone, and the antenna side is viewed from the AGC circuit Since the impedance is within about 4% of the impedance of the AGC circuit, a sufficient gain can be secured. Further, by providing the AGC circuit, it is possible to prevent the occurrence of distortion under a strong electric field.
  • FIG. 1 A circuit diagram of the configuration of the tunable antenna device of the first embodiment of the present invention is shown in FIG.
  • the tunable antenna device 1 according to the first embodiment shown in FIG. 1 is connected in series in order to resonate the antenna 10 with the frequency of the FM broadcast and the small antenna 10 which does not resonate in the broadcast band of the FM radio when the antenna alone is used.
  • a loading coil 11 and a tuning circuit 12 connected between the loading coil 11 and the output terminal OUT are provided.
  • an AGC circuit 13 is connected between the connection point of the loading coil 11 and the tuning circuit 12 and the ground. The received signal received by the tunable antenna device 1 is output from the output terminal OUT.
  • the tuning circuit 12 includes two varicap diodes BD1 and BD2 connected in series in reverse polarity to the tuning coil 12a, and the junction between the varicap diodes BD1 and BD2 whose cathodes are connected is positive via a resistor R1. A voltage Vt is applied. Further, a choke coil CH1 is connected between the output terminal OUT and the ground to block a high frequency (RF) signal and to ground the output terminal OUT in a DC manner. The anodes of the varicap diodes BD1 and BD2 are DC-grounded by the choke coil CH1. Thus, the capacitance of the varicap diodes BD1 and BD2 can be varied by changing the value of the positive voltage Vt.
  • the inductance value of the tuning coil 12a in the tuning circuit 12 and the variable capacitance range of the varicap diodes BD1 and BD2 are selected such that the tunable antenna device 1 resonates at least in the 76 MHz to 90 MHz broadcast band of FM radio. ing.
  • the positive voltage Vt is increased in the tuning circuit 12
  • the reverse voltage applied between the cathode and the anode of the varicap diodes BD1 and BD2 is increased, and the capacitance value of the varicap diodes BD1 and BD2 is reduced.
  • the resonant frequency of the tunable antenna device 1 as a whole becomes high.
  • the positive voltage Vt in the tuning circuit 12 when the positive voltage Vt in the tuning circuit 12 is lowered, the reverse voltage applied between the cathode and the anode of the varicap diodes BD1 and BD2 is reduced, and the capacitance value of the varicap diodes BD1 and BD2 is increased. Thus, the resonant frequency of the tunable antenna device 1 as a whole is lowered. In this manner, by adjusting the value of the positive voltage Vt in the tuning circuit 12, the impedance of the tuning circuit 12 is varied, so that the resonant frequency of the entire tunable antenna device 1 becomes a specific frequency within the broadcast band of the FM radio. Become tuned.
  • the AGC circuit 13 connected between the connection point of the loading coil 11 and the tuning circuit 12 and the ground does not generate distortion in the received signal due to non-linearity of the varicap diodes BD1 and BD2 under a strong electric field. Control is performed to attenuate the reception signal input to the varicap diodes BD1 and BD2 under a strong electric field.
  • a circuit example of this AGC circuit 13 is shown in FIG. 2, but the AGC circuit 13 shown in FIG. 2 comprises a control circuit 13a and two pin diodes PIN1 and PIN2 connected in series so as to be in the forward direction.
  • the cathode of the pin diode PIN2 is grounded, and the anode of the pin diode PIN1 is grounded at a high frequency by the bypass capacitor C2.
  • a connection point between the cathode of the pin diode PIN1 and the anode of the PIN diode PIN2 connected in series is connected to the connection point between the loading coil 11 and the tuning circuit 12 via the capacitor C1.
  • the AGC circuit 13 performs level control so that the level of the reception signal output to the output terminal OUT does not exceed a predetermined value. That is, the reception signal from the output terminal OUT is input to the control circuit 13a, and the control circuit 13a outputs a control signal of a DC voltage value corresponding to the level of the input reception signal.
  • the control signal is applied between the series circuit of the pin diodes PIN1 and PIN2 and the ground, and the resistance value of the pin diodes PIN1 and PIN2 connected in series can be varied according to the DC voltage value of the control signal.
  • the DC voltage value output from control circuit 13a is increased under a strong electric field, and the resistance values of pin diodes PIN1 and PIN2 are reduced. Therefore, the received signal is a capacitor C1-pin diode PIN1-bypass capacitor C2. Attenuation occurs in the path of ground and in the path of capacitor C1-pin diode PIN2-ground. Thereby, the AGC circuit 13 performs level control so that the level of the reception signal input to the varicap diodes BD1 and BD2 does not exceed a predetermined value.
  • the DC voltage value output from the control circuit 13a decreases, and the resistance values of the pin diodes PIN1 and PIN2 increase, so that the received signal is not substantially attenuated in the above path.
  • the varicap diodes BD1 and BD2 it is possible to prevent the varicap diodes BD1 and BD2 from giving distortion to the reception signal under a strong electric field by providing the AGC circuit 13. Become.
  • the resonance frequency of the tunable antenna device 1 is adjusted to about 76 MHz which is the low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12
  • the frequency characteristic of the gain of the tunable antenna device 1 of the first embodiment when the frequency is about 83 MHz and the high band edge is about 90 MHz, and the conventional antenna device 101 shown in FIG. 41 without the tuning circuit 12 3 to 5 in comparison with the frequency characteristic of the gain of.
  • FIG. 3 shows the case where the resonance frequency of the tunable antenna device 1 is about 76 MHz by adjusting the positive voltage Vt.
  • the gain of the tunable antenna device 1 of the first embodiment shown by the marker 1 is It can be seen that the gain of the conventional antenna device 101 is about 2.4 dB higher.
  • FIG. 4 is a case where the resonance frequency of the tunable antenna device 1 is adjusted to about 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 4, the gain of the tunable antenna device 1 at 83 MHz indicated by the marker 2 is It can be seen that the gain is about 1.0 dB lower than the gain of the conventional antenna device 101.
  • FIG. 5 shows the case where the resonant frequency of the tunable antenna device 1 is adjusted to about 90 MHz by adjusting the positive voltage Vt.
  • the tunable antenna device of the first embodiment at 90 MHz indicated by the marker 3 It can be seen that the gain of 1 is about 1.3 dB higher than the gain of the conventional antenna device 101.
  • “Ref 1” in FIGS. 3 to 5 is a fixed first reference value, and the same applies to the subsequent figures.
  • the impedance of the measurement system is 75 ⁇ , and the same applies to the subsequent drawings.
  • the tunable antenna device 1 of the first embodiment is provided with the AGC circuit 13 to prevent the occurrence of distortion
  • the gain is slightly reduced in the broadcast band of the FM radio because the AGC circuit 13 is provided. You will come to However, the frequency characteristic of the gain in the broadcast band of FM radio is flattened.
  • FIG. 6 is a circuit diagram showing a configuration of a tunable antenna device 2 according to a second embodiment of the present invention provided with an AGC circuit 13 'modified to minimize a decrease in gain in the AGC circuit 13.
  • the tunable antenna device 2 of the second embodiment shown in FIG. 6 is different only in the configuration of the AGC circuit 13 ', and the other configuration is the same. Therefore, only the AGC circuit 13' will be described.
  • the reception signal supplied from the antenna 10 to the tuning circuit 12 is the reception signal generated at both ends of the AGC circuit 13. This reception signal is divided by the impedance of the AGC circuit 13 and the impedance seen from the AGC circuit 13 to the antenna 10 side.
  • the impedance of the AGC circuit 13 is low, the reception signal divided by that amount will be lost.
  • the impedance of the two pin diodes PIN1 and PIN2 at the off time was about 2.5 k ⁇ .
  • the AGC circuit 13 'in the tunable antenna device 2 of the second embodiment is changed to use a pin diode that exhibits a high impedance of about 5 k ⁇ when it is off. doing.
  • the resonance frequency of the tunable antenna device 2 is adjusted to about 76 MHz, which is the low band edge of the FM radio broadcast band, by adjusting the positive voltage Vt applied to the tuning circuit 12
  • the frequency characteristic of the gain of the tunable antenna device 2 of the second embodiment when the frequency is about 83 MHz and the high band edge is about 90 MHz, and the conventional antenna device 101 shown in FIG. 41 without the tuning circuit 12 7 to 9 in comparison with the frequency characteristic of the gain of.
  • FIG. 7 shows the case where the resonance frequency of the tunable antenna device 2 is adjusted to about 76 MHz by adjusting the positive voltage Vt.
  • FIG. 7 shows a case where the resonant frequency of the tunable antenna device 2 is adjusted to about 83 MHz by adjusting the positive voltage Vt.
  • the gain of the tunable antenna device 2 at 83 MHz indicated by the marker 2 is It can be seen that the gain of the conventional antenna device 101 is about 0.5 dB lower.
  • FIG. 9 shows the case where the resonant frequency of the tunable antenna device 2 is adjusted to about 90 MHz by adjusting the positive voltage Vt.
  • the tunable antenna device of the second embodiment at 90 MHz indicated by the marker 3 It can be seen that the gain of 2 is about 2.6 dB higher than the gain of the conventional antenna device 101.
  • the tunable antenna device 2 of the second embodiment can prevent the occurrence of distortion by providing the AGC circuit 13 ', and can reduce the gain in the broadcast band of the FM radio by the AGC circuit 13'. It will be possible to suppress. Also, the frequency characteristic of the gain in the broadcast band of the FM radio is flattened.
  • the degree of improvement of the gain is low from the mid band to the high band in the broadcasting band of the FM radio. Therefore, in order to investigate this cause, as shown in FIG. 10, the tuning circuit 12 and subsequent sections are separated, and the frequency characteristics of the impedance at the separated point A are examined.
  • the frequency characteristics of the impedance viewed from the point A are shown in FIG. 11.
  • the antenna impedance at 83 MHz indicated by the marker 2 is about 157 ⁇ .
  • the impedance of the AGC circuit 13 ' is about 5 k ⁇ as described above, and the antenna impedance of about 157 ⁇ is about 3.14% of about 5 k ⁇ .
  • the fact that the antenna impedance is 3% or more of the impedance of the AGC circuit 13 ' is considered to cause about 0.5 dB of gain attenuation at 83 MHz.
  • the reason for this gain attenuation is that the reception signal supplied to the tuning circuit 12 is a reception signal generated at both ends of the AGC circuit 13 ′, and this reception signal is the impedance of the AGC circuit 13 ′ and the antenna circuit 10 from the AGC circuit 13 ′. This is because the received signal is divided by the impedance viewed from the side.
  • FIG. 12 shows frequency characteristics of impedance as viewed from point A in FIG. 10 when the number of turns is reduced so as to lower the inductance value of the loading coil 11 and the inductance value of the loading coil 11 is slightly reduced.
  • the maximum impedance in the band from 76 MHz indicated by marker 1 to 90 MHz indicated by marker 3 is about 120 ⁇ .
  • the antenna impedance (120 ⁇ ) in the broadcast band of the FM radio with respect to the impedance (about 5 k ⁇ ) of the AGC circuit 13 ′ becomes 2.4% and 3% at maximum, and from the middle band of the tunable antenna device It is possible to improve the gain in the high region.
  • FIG. 1 A circuit diagram showing a configuration of a tunable antenna device 3 according to a third embodiment of the present invention for improving the gain in the middle to high frequencies based on the above result is shown in FIG.
  • the number of turns of the first loading coil 11-1 connected to the antenna 10 is reduced to reduce the inductance value so that the gain can be improved in the middle to high regions.
  • the second loading coil 11-2 is connected in series to the first loading coil 11-1 in order to compensate for the reduction in the inductance value of the first loading coil 11-1.
  • the antenna 10 resonates in the broadcast band of the FM radio by the action of the second loading coil 11-2.
  • an AGC circuit 13 ' having an impedance of about 5 k ⁇ is connected between the connection point of the first loading coil 11-1 and the second loading coil 11-2 and the ground.
  • the tuning circuit 12 is connected between the second loading coil 11-2 and the output terminal OUT, and the reception signal of the tunable antenna device 3 is output from the output terminal OUT.
  • FIG. 14 shows the frequency characteristic of the impedance of the tunable antenna device 3 of the third embodiment when the resonant frequency of the tunable antenna device 3 is set to about 76 MHz by adjusting the positive voltage Vt applied to the tuning circuit 12 .
  • the Smith chart shown in FIG. 14 it can be seen that, as indicated by the marker 1, it has a low impedance by resonating approximately at 76 MHz which is the low band edge of the broadcast band of the FM radio.
  • FIG. 15 shows the frequency characteristics of the impedance of the tunable antenna device 3 of the third embodiment when the resonant frequency of the tunable antenna device 3 is adjusted to about 83 MHz by adjusting the positive voltage Vt.
  • the Smith chart shown in FIG. 15 it can be seen that, as shown by the marker 2, it has a low impedance by resonating approximately at 83 MHz which is the center frequency of the broadcast band of the FM radio.
  • FIG. 16 is a frequency characteristic of the impedance of the tunable antenna device 3 of the third embodiment when the resonant frequency of the tunable antenna device 3 is adjusted to about 90 MHz by adjusting the positive voltage Vt.
  • the impedance is low resonance by resonating substantially at 90 MHz, which is the high band edge of the broadcast band of the FM radio.
  • the resonant voltage of the tunable antenna device 3 is adjusted to a low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12.
  • the frequency characteristics of the gain of the antenna device 101 are shown in contrast in FIGS. 17 to 19.
  • FIG. 17 shows the case where the resonant frequency of the tunable antenna device 3 is 76 MHz by adjusting the positive voltage Vt.
  • the tunable antenna device 3 of the third embodiment at 76 MHz indicated by the marker 1 is shown. It can be seen that the gain is about 2.2 dB higher than the gain of the conventional antenna device 101.
  • 18 shows the case where the resonant frequency of the tunable antenna device 3 is 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 18, the tunable antenna device 3 of the third embodiment at 83 MHz indicated by the marker 2 is shown. It can be seen that the gain of V is approximately equal to the gain of the conventional antenna device 101.
  • FIG. 19 shows the case where the resonance frequency of the tunable antenna device 3 is 90 MHz by adjusting the positive voltage Vt.
  • the tunable antenna device 3 of the third embodiment at 90 MHz indicated by the marker 3 is shown. It can be seen that the gain of is approximately 3.9 dB higher than the gain of the conventional antenna device 101.
  • the tunable antenna device 3 of the third embodiment can prevent the occurrence of distortion by providing the AGC circuit 13 '.
  • the loading coil is divided into two loading coils 11-1 and 11-2, and an AGC circuit 13 'is connected between the connection point of the two loading coils 11-1 and 11-2 and the ground.
  • the mid-to-high band gain in the FM radio broadcast band can be improved to further flatten the frequency characteristic of the gain in the FM radio broadcast band.
  • the positive voltage Vt applied to the tuning circuit 12 is adjusted to set the resonance frequency of the tuning circuit 12 to about 76 MHz, which is the low band edge of the FM radio broadcast band.
  • the AGC circuit 13 ' is operating when the center frequency is about 83 MHz and the high band edge is about 90 MHz, and when the AGC circuit 13' is not operating (the pin diodes PIN1 and PIN2 are off and non-operating)
  • FIGS. FIG. 20 shows the case where the resonance frequency of the tunable antenna device 3 is 76 MHz by adjusting the positive voltage Vt.
  • FIG. 21 shows the case where the resonance frequency of the tunable antenna device 3 is 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 21, the tunable antenna device 3 of the third embodiment at 83 MHz indicated by the marker 2. The gain during the operation of the AGC circuit 13 'is attenuated by only about 15 dB as compared to when the AGC circuit 13' is not in operation.
  • FIG. 22 shows the case where the resonance frequency of the tunable antenna device 3 is adjusted to 90 MHz by adjusting the positive voltage Vt.
  • the gain at the time of operation of the AGC circuit 13 ' is attenuated by 40 dB or more compared to when the AGC circuit 13' is not at operation.
  • “Ref 2” in FIG. 20 to FIG. 22 is a fixed second reference value, and the same applies to the subsequent figures.
  • a sufficient amount of attenuation can not be obtained in the vicinity of 83 MHz when the AGC circuit 13 'operates, and distortion may occur under a strong electric field. .
  • the peak of the gain appears at about 83 MHz when the AGC circuit 13 'is operating, which is considered to be because the resonance frequency of the antenna 10 and the first loading coil 11-1 is near 83 MHz. Therefore, in the tunable antenna device 3 of the third embodiment, the point a1 and the point a2 shown in FIG. 23 are disconnected, and the frequency characteristic of the impedance viewed from the point a1 is examined. Then, it was confirmed that the resonant frequency of the antenna 10 and the first loading coil 11-1 was near 83 MHz. From this, the inductance value of the first loading coil 11-1 was decreased so that this resonance frequency would be outside the broadcast band of the FM radio. FIG.
  • the resonance frequency of the antenna 10 and the first loading coil 11-1 is 91.5 MHz indicated by the marker 4 and outside the broadcast band of the FM radio.
  • the configuration of the tunable antenna device 4 according to the fourth embodiment of the present invention provided with the third loading coil 11-3 in which the inductance value of the first loading coil 11-1 is adjusted to be outside the broadcast band of FM radio.
  • the tunable antenna device 4 according to the fourth embodiment shown in FIG. 25 includes a third loading coil 11-3 connected to the antenna 10 and a fourth loading coil 11 connected in series to the third loading coil 11-3. It has -4.
  • the number of turns of the third loading coil 11-3 is smaller than that of the first loading coil 11-1 and the inductance value is lowered.
  • the number of turns of the fourth loading coil 11-4 is the second loading coil 11 so as to compensate for this.
  • the inductance value is higher than -2.
  • the resonance frequency of the antenna 10 and the third loading coil 11-3 can be set outside the broadcast band of the FM radio, and the antenna 10 is in the broadcast band of the FM radio by the action of the fourth loading coil 11-4.
  • an AGC circuit 13 'having an impedance of about 5 k ⁇ is connected between the connection point of the third loading coil 11-3 and the fourth loading coil 11-4 and the ground.
  • the tuning circuit 12 is connected between the fourth loading coil 11-4 and the output terminal OUT. The received signal received by the antenna 10 is output from the output terminal OUT through the tuning circuit 12.
  • the resonant voltage of the tunable antenna device 4 is adjusted to a low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12.
  • the frequency characteristics of the gain of the antenna device 101 are shown in contrast in FIGS. 26 shows the case where the resonance frequency of the tunable antenna device 4 is 76 MHz by adjusting the positive voltage Vt.
  • the tunable antenna device 4 of the fourth embodiment at 76 MHz indicated by the marker 1 is shown. It can be seen that the gain is about 1.4 dB higher than the gain of the conventional antenna device 101.
  • 27 shows the case where the resonance frequency of the tunable antenna device 4 is 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 27, the tunable antenna device 4 of the fourth embodiment at 83 MHz indicated by the marker 2 is shown. It can be seen that the gain of is approximately 0.3 dB lower than the gain of the conventional antenna device 101.
  • FIG. 28 shows the case where the resonance frequency of the tunable antenna device 4 is 90 MHz by adjusting the positive voltage Vt.
  • the tunable antenna device 4 of the fourth embodiment at 90 MHz indicated by the marker 3. It can be seen that the gain of is approximately 4.2 dB higher than the gain of the conventional antenna device 101.
  • the gain in the lower band (near 76 MHz) of the tunable antenna device 3 of the third embodiment is reduced by about 0.8 dB.
  • the cause of this is that when the inductance value of the third loading coil 11-3 is reduced, the impedance at 76 MHz shown by the marker 1 in FIG.
  • the occurrence of distortion can be prevented by the AGC circuit 13 '.
  • the inductance value of the third loading coil 11-3 and the fourth loading coil 11-4 divided into two is adjusted as described above, and the connection point between the two loading coils 11-3 and 11-4.
  • the resonant voltage of the tunable antenna device 4 is adjusted to a low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12.
  • AGC circuit 13 ' is operating at 76 MHz
  • center frequency is about 83 MHz
  • high band edge is about 90 MHz
  • FIG. 29 shows the case where the resonance frequency of the tunable antenna device 4 is adjusted to about 76 MHz by adjusting the positive voltage Vt.
  • FIG. 30 shows the case where the resonance frequency of the tunable antenna device 4 is adjusted to about 83 MHz by adjusting the positive voltage Vt.
  • the tunable of the fourth embodiment at 83 MHz.
  • the gain at the time of operation of the AGC circuit 13 ' is attenuated by about 40 dB or more as compared with the time of the non-operation of the AGC circuit 13'.
  • FIG. 31 shows the case where the resonance frequency of the tunable antenna device 4 is adjusted to about 90 MHz by adjusting the positive voltage Vt.
  • the tunable antenna device of the fourth embodiment at 90 MHz as shown by the marker 3
  • the gain at the time of operation of the AGC circuit 13 ' is attenuated by 30 dB or more at 4 compared with the time of non-operation of the AGC circuit 13'.
  • the inductance values of the third loading coil 11-3 and the fourth loading coil 11-4 divided into two are adjusted as described above.
  • a sufficient attenuation amount of at least 30 dB can be obtained in the entire band of the FM broadcast, and the occurrence of distortion under a strong electric field can be prevented.
  • FIG. 32 is a circuit diagram showing a configuration of a tunable antenna device 5 according to a fifth embodiment of the present invention.
  • the tunable antenna device 5 of the fifth embodiment shown in FIG. 32 has a configuration in which a matching circuit is added to the tunable antenna device 4 of the fourth embodiment. That is, the tunable antenna device 5 of the fifth embodiment includes a third loading coil 11-3 connected to the antenna 10 and a fourth loading coil 11-4 connected in series to the third loading coil 11-3. And have.
  • the resonance frequency of the antenna 10 and the third loading coil 11-3 can be set outside the broadcast band of the FM radio, and the antenna 10 is in the broadcast band of the FM radio by the action of the fourth loading coil 11-4. To resonate.
  • an AGC circuit 13 ' having an impedance of about 5 k ⁇ is connected between the connection point of the third loading coil 11-3 and the fourth loading coil 11-4 and the ground.
  • the tuning circuit 12 is connected between the fourth loading coil 11-4 and the output terminal OUT.
  • a matching circuit 14 composed of a matching coil is connected between the output terminal OUT and the ground, and the reception signal of the tunable antenna device 5 is output from the output terminal OUT.
  • FIG. 33 shows the frequency characteristics of the impedance of the tunable antenna device 5 of the fifth embodiment when the resonant frequency of the tunable antenna device 5 is set to about 76 MHz by adjusting the positive voltage Vt applied to the tuning circuit 12 .
  • Vt the positive voltage
  • FIG. 33 it can be seen that, as indicated by the marker 1, it resonates at 76 MHz, which is the low band edge of the broadcast band of the FM radio, and is substantially ideally impedance matched.
  • the voltage standing wave ratio (VSWR) in this case is about 1.1.
  • FIG. 34 shows the frequency characteristic of the impedance of the tunable antenna device 5 of the fifth embodiment when the resonant frequency of the tunable antenna device 5 is adjusted to about 83 MHz by adjusting the positive voltage Vt.
  • the Smith chart shown in FIG. 34 it can be seen that, as indicated by the marker 2, it resonates substantially at 83 MHz, which is the center frequency of the broadcast band of the FM radio, and is substantially impedance matched.
  • the voltage standing wave ratio (VSWR) in this case is about 1.8.
  • FIG. 35 shows the frequency characteristics of the impedance of the tunable antenna device 5 of the fifth embodiment when the resonant frequency of the tunable antenna device 5 is adjusted to about 90 MHz by adjusting the positive voltage Vt.
  • VSWR voltage standing wave ratio
  • the resonant voltage of the tunable antenna device 5 is adjusted to a low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12.
  • the frequency characteristics of the gain of the antenna device 101 are shown in FIGS. 36 to 38 in comparison. 36 shows the case where the resonance frequency of the tunable antenna device 5 is adjusted to about 76 MHz by adjusting the positive voltage Vt. Referring to FIG.
  • FIG. 37 shows the case where the resonance frequency of the tunable antenna device 5 is adjusted to 83 MHz by adjusting the positive voltage Vt.
  • the tunable antenna device 5 of the fifth example at 83 MHz shown by the marker 2 It can be seen that the gain of V is approximately 3.2 dB higher than the gain of the conventional antenna device 101.
  • FIG. 38 shows the case where the resonance frequency of the tunable antenna device 5 is 90 MHz by adjusting the positive voltage Vt.
  • the tunable antenna device 5 of the fifth embodiment at 90 MHz indicated by the marker 3
  • the gain of is approximately 6.9 dB higher than the gain of the conventional antenna device 101.
  • the tunable antenna device 5 of the fifth embodiment can achieve a gain improvement of up to 6.9 dB.
  • the gain deviation in the broadcast band of FM radio is about 2.5 dB which is the difference between the gain when tuned to 76 MHz and the gain of 90 MHz, which further flattens the frequency characteristics of the gain in the broadcast band of FM radio can do.
  • the loading coil is divided into two loading coils 11-3 and 11-4 whose inductance value is adjusted, and an AGC circuit 13 'is connected between the connection point of the two loading coils 11-3 and 11-4 and the ground.
  • the gain from the mid band to the high band in the broadcast band of the FM radio is improved.
  • the output terminal OUT can be grounded in a direct current manner by the matching circuit 14, the choke coil CH1 can be omitted.
  • the impedance of the tuning circuit is varied by adjusting the value of the positive voltage Vt applied to the tuning circuit.
  • the resonant frequency of the entire tunable antenna device in the embodiment comes to be tuned to a specific frequency within the broadcast band of the FM radio.
  • the impedance seen from the AGC circuit to the antenna side is within about 3% of the impedance of the AGC circuit. Although it is considered ideal, sufficient gain can be secured even if it is within about 4% as described above.
  • the impedance of the AGC circuit is approximately 5 k ⁇ , but the impedance is not limited to this. If it satisfies about 4% or less of the impedance of the AGC circuit, it may be less than 5 k ⁇ .
  • the AGC circuit is a circuit using two pin diodes, it is not limited to this and may be an AGC circuit using one or more pin diodes.
  • the tuning circuit is a circuit using two varicap diodes, it is not limited to this and may be a tuning circuit using one or more varicap diodes.
  • the matching circuit may be provided in the tunable antenna device of the first to fourth embodiments. When the matching circuit is provided, the choke coil CH1 that grounds the output terminal OUT in a direct current manner can be omitted. The value of the choke coil CH1 is set to a value that does not affect the resonant frequency of the tunable antenna device according to the present invention.

Landscapes

  • Details Of Aerials (AREA)
  • Input Circuits Of Receivers And Coupling Of Receivers And Audio Equipment (AREA)

Abstract

Disclosed is a tunable antenna device which secures gain while being a miniaturized antenna of a narrow area for which distortion never occurs under high fields. The tunable antenna device (3) of the third embodiment is provided with a first loading coil (11-1) connected to an antenna (10) and a second loading coil (11-2) which are serially connected. As a result, even if the impedance value of the first loading coil (11-1) is lowered, the antenna (10) resonates in a broadcast band of FM radio by way of the effect of the second loading coil (11-2). In addition, an AGC circuit (13') is connected from between the loading coils (11-1 and 11-2) to a ground. Furthermore, a tuned circuit (12) is connected between the second loading coil (11-2) and an output terminal (OUT), whereupon a received signal from the tunable antenna device (3) is output from the output terminal (OUT).

Description

チューナブルアンテナ装置Tunable antenna device
　本発明は、小型化・狭面積化されたアンテナでありながらアンテナ利得を確保することのできるチューナブルアンテナ装置に関する。 The present invention relates to a tunable antenna device capable of securing antenna gain while being a miniaturized and narrowed antenna.
　従来、一般的な車載用のアンテナ装置として、ルーフ後方に配置された２００ｍｍ程度の棒状アンテナや窓ガラス表面にアンテナを形成したガラスアンテナが用いられている。将来の車載用のアンテナ装置として小型化・低姿勢化されたアンテナや、車両の窓ガラスを狭面積化するよう狭小化されたレイアウトのガラスアンテナが求められている。これらの小型化・低姿勢化されたアンテナやレイアウトが狭小化されたガラスアンテナの一般的な等価回路図を図３９に示す。図３９に示す等価回路図で示すアンテナ装置１００は、小型化・低姿勢化された棒状アンテナやレイアウトが狭小化されたガラスアンテナからなるアンテナ１１０を備え、アンテナ１１０により受信された受信信号が出力端子ＯＵＴから出力されている。このアンテナ装置１００のインピーダンスの周波数特性が図４０に示すスミスチャートに示されている。図４０に示すスミスチャートを参照すると、マーカ１，２，３で示されるＦＭラジオの放送帯域とされる７６ＭＨｚ－８３ＭＨｚ－９０ＭＨｚの帯域において、高いインピーダンスを示しており十分な性能を引き出す事が困難であることが分かる。これは、アンテナ装置１００の大きさや車両デザイン・視認性・取り付け位置といった形状の制約を受けているからである。 Conventionally, as a general vehicle-mounted antenna device, a rod-like antenna of about 200 mm disposed at the rear of a roof or a glass antenna in which the antenna is formed on the surface of a window glass is used. As a future vehicle antenna device, a miniaturized and low-profile antenna, and a glass antenna having a narrowed layout so as to narrow a window glass of a vehicle are required. FIG. 39 shows a general equivalent circuit diagram of the miniaturized and low-profile antenna and the glass antenna whose layout is narrowed. The antenna device 100 shown in the equivalent circuit diagram shown in FIG. 39 includes an antenna 110 composed of a rod antenna with a reduced size and a reduced profile and a glass antenna with a narrowed layout, and the received signal received by the antenna 110 is output It is output from the terminal OUT. The frequency characteristic of the impedance of the antenna device 100 is shown in the Smith chart shown in FIG. Referring to the Smith chart shown in FIG. 40, high impedance is shown in the 76 MHz-83 MHz-90 MHz band, which is the FM radio broadcast band shown by markers 1, 2 and 3, and it is difficult to extract sufficient performance. It is understood that This is because the size of the antenna device 100 and the shape such as the vehicle design, the visibility and the mounting position are limited.
　また、車両から７０ｍｍ以下の高さで突出するアンテナケースの内部に、アンテナパターンを形成したアンテナ基板を立設して配設した車両用のアンテナ装置が、従来提案されている。このアンテナ装置においては、アンテナ基板から出力される受信信号を増幅するアンプ基板がアンテナケース内に収納されており、アンテナ基板において、アンテナパターンと給電点の間にＦＭラジオの放送帯域にアンテナパターンを共振させるためのアンテナコイルが挿入されている。これにより、ＦＭ放送の波長に対して約１／２０の長さとされた低姿勢のアンテナパターンがＦＭラジオの放送帯域に共振するようになる。
　このような小型のアンテナにアンテナコイルを備えさせたアンテナ装置１０１の等価回路図を図４１に示す。図４１に示すアンテナ装置１０１は、小型のアンテナ１１０と、アンテナ１１０に直列に接続されたローディングコイル１１１とを備え、アンテナ１１０により受信された受信信号が出力端子ＯＵＴから出力されている。このアンテナ装置１０１のインピーダンスの周波数特性が図４２に示すスミスチャートに示されている。図４２に示すスミスチャートを参照すると、ＦＭラジオの放送帯域のバンドエッジとされる７６ＭＨｚおよび９０ＭＨｚの近傍においては高いインピーダンスを示しているが、中心周波数の８３ＭＨｚの近傍においては低いインピーダンスを示している。また、８３ＭＨｚの近傍においてアンテナ装置１０１は共振するようになる。このように、アンテナ１１０単体では図４０に示すようにＦＭ放送の周波数帯に共振しないが、ローディングコイル１１１をアンテナ１１０と直列に接続することにより、ＦＭ放送の周波数帯域に共振させることができるようになる。 In addition, an antenna device for a vehicle has conventionally been proposed in which an antenna substrate on which an antenna pattern is formed is erected and disposed inside an antenna case projecting at a height of 70 mm or less from the vehicle. In this antenna device, an amplifier substrate for amplifying a received signal output from the antenna substrate is accommodated in the antenna case, and the antenna pattern is provided in the broadcasting band of the FM radio between the antenna pattern and the feeding point on the antenna substrate. An antenna coil for resonance is inserted. As a result, the low-profile antenna pattern, which is about 1/20 the length of the FM broadcast wavelength, resonates in the FM radio broadcast band.
An equivalent circuit diagram of an antenna apparatus 101 in which such a small antenna is provided with an antenna coil is shown in FIG. The antenna device 101 shown in FIG. 41 includes a small antenna 110 and a loading coil 111 connected in series to the antenna 110, and a reception signal received by the antenna 110 is output from the output terminal OUT. The frequency characteristic of the impedance of the antenna device 101 is shown in the Smith chart shown in FIG. Referring to the Smith chart shown in FIG. 42, high impedance is shown in the vicinity of 76 MHz and 90 MHz which are considered as band edges of the broadcast band of FM radio, but low impedance is shown in the vicinity of 83 MHz of the center frequency. . Also, the antenna device 101 resonates in the vicinity of 83 MHz. Thus, although the antenna 110 alone does not resonate in the frequency band of the FM broadcast as shown in FIG. 40, by connecting the loading coil 111 in series with the antenna 110, it is possible to resonate in the frequency band of the FM broadcast become.
ＷＯ２００８／０６２７４６号公報WO 2008/062746
　また、ＦＭ放送の周波数帯域内の周波数に同調することのできる従来のチューナブルアンテナ装置１０２を等価回路図を図４３に示す。
　図４３に示すチューナブルアンテナ装置１０２は、小型のアンテナ１１０と、アンテナ１１０に直列に接続された巻き数が変更されたローディングコイル１１１－１とを備え、ローディングコイル１１１－１と出力端子ＯＵＴとの間に同調回路１１２が接続されている。アンテナ１１０により受信された受信信号は同調回路１１２を介して出力端子ＯＵＴから出力される。同調回路１１２は、同調コイル１１２ａと逆極性で直列接続された２本のバリキャップダイオードＢＤ１０１，ＢＤ１０２からなり、カソード同士が接続されたバリキャップダイオードＢＤ１０１，ＢＤ１０２の接続点に抵抗Ｒ１００を介して正電圧Ｖｔが印加されている。また、出力端子ＯＵＴとアース間に高周波（ＲＦ）信号を阻止して、出力端子ＯＵＴを直流的にアースするチョークコイルＣＨ１００が接続されている。このチョークコイルＣＨ１００により、バリキャップダイオードＢＤ１０１，ＢＤ１０２のアノードが直流的にアースされることになる。 Also, FIG. 43 shows an equivalent circuit diagram of a conventional tunable antenna device 102 that can be tuned to a frequency within the frequency band of FM broadcasting.
A tunable antenna device 102 shown in FIG. 43 includes a small antenna 110 and a loading coil 111-1 connected in series to the antenna 110 and having a different number of turns, and includes a loading coil 111-1 and an output terminal OUT. The tuning circuit 112 is connected between them. The received signal received by the antenna 110 is output from the output terminal OUT through the tuning circuit 112. The tuning circuit 112 includes two varicap diodes BD101 and BD102 connected in series in reverse polarity to the tuning coil 112a, and the positive terminal is connected to the junction of the varicap diodes BD101 and BD102 whose cathodes are connected via a resistor R100. A voltage Vt is applied. Further, a choke coil CH100 is connected between the output terminal OUT and the ground to block a high frequency (RF) signal and to ground the output terminal OUT in a DC manner. The anodes of the varicap diodes BD101 and BD102 are DC-grounded by the choke coil CH100.
　ここで、同調回路１１２に印加される正電圧Ｖｔを高くしていくと、バリキャップダイオードＢＤ１０１，ＢＤ１０２のカソード－アノード間に印加される逆電圧が高くなってバリキャップダイオードＢＤ１０１，ＢＤ１０２の容量値が小さくなることから、チューナブルアンテナ装置１０２全体の共振周波数は高くなる。逆に、同調回路１１２における正電圧Ｖｔを低くしていくと、バリキャップダイオードＢＤ１０１，ＢＤ１０２のカソード－アノード間に印加される逆電圧が低くなってバリキャップダイオードＢＤ１０１，ＢＤ１０２の容量値が大きくなることから、チューナブルアンテナ装置１０２全体の共振周波数は低くなる。ここで、正電圧Ｖｔを調整してチューナブルアンテナ装置１０２の共振周波数を約７６ＭＨｚにした際のチューナブルアンテナ装置１０２のインピーダンスの周波数特性を示すスミスチャートを図４４に示す。図４４に示すスミスチャートを参照すると、マーカ１で示されるＦＭラジオの放送帯域の低いバンドエッジである７６ＭＨｚにほぼ共振して低いインピーダンスとなっていることが分かる。 Here, when the positive voltage Vt applied to the tuning circuit 112 is increased, the reverse voltage applied between the cathode and the anode of the varicap diodes BD101 and BD102 is increased, and the capacitance value of the varicap diodes BD101 and BD102 is obtained. Becomes smaller, the resonant frequency of the tunable antenna device 102 as a whole becomes higher. Conversely, as the positive voltage Vt in the tuning circuit 112 is lowered, the reverse voltage applied between the cathode and the anode of the varicap diodes BD101 and BD102 is reduced, and the capacitance value of the varicap diodes BD101 and BD102 is increased. Thus, the resonant frequency of the entire tunable antenna device 102 is lowered. Here, a Smith chart showing the frequency characteristics of the impedance of the tunable antenna device 102 when adjusting the positive voltage Vt to make the resonant frequency of the tunable antenna device 102 about 76 MHz is shown in FIG. Referring to the Smith chart shown in FIG. 44, it can be seen that the impedance is low in resonance approximately at 76 MHz which is the low band edge of the broadcast band of the FM radio indicated by the marker 1.
　また、正電圧Ｖｔを調整してチューナブルアンテナ装置１０２の共振周波数を約８３ＭＨｚにした際のチューナブルアンテナ装置１０２のインピーダンスの周波数特性を示すスミスチャートを図４５に示す。図４５に示すスミスチャートを参照すると、マーカ２で示されるＦＭラジオの放送帯域の中心周波数とされる８３ＭＨｚにほぼ共振して低いインピーダンスとなっていることが分かる。さらに、正電圧Ｖｔを調整してチューナブルアンテナ装置１０２の共振周波数を約９０ＭＨｚにした際のチューナブルアンテナ装置１０２のインピーダンスの周波数特性を示すスミスチャートを図４６に示す。図４６に示すスミスチャートを参照すると、マーカ３で示されるＦＭラジオの放送帯域の高いバンドエッジである９０ＭＨｚにほぼ共振して低いインピーダンスとなっていることが分かる。 Further, a Smith chart showing the frequency characteristics of the impedance of the tunable antenna device 102 when the resonant frequency of the tunable antenna device 102 is adjusted to about 83 MHz by adjusting the positive voltage Vt is shown in FIG. Referring to the Smith chart shown in FIG. 45, it can be seen that the impedance is low in resonance approximately at 83 MHz, which is the center frequency of the broadcast band of the FM radio indicated by the marker 2. Furthermore, FIG. 46 shows a Smith chart showing the frequency characteristics of the impedance of the tunable antenna device 102 when adjusting the positive voltage Vt to make the resonant frequency of the tunable antenna device 102 about 90 MHz. Referring to the Smith chart shown in FIG. 46, it can be seen that the impedance is low in resonance approximately at 90 MHz, which is the high band edge of the broadcast band of the FM radio indicated by the marker 3.
　次に、同調回路１１２に印加される正電圧Ｖｔを調整することにより、チューナブルアンテナ装置１０２の共振周波数をＦＭラジオの放送帯域の低いバンドエッジである約７６ＭＨｚ、中心周波数である約８３ＭＨｚ、高いバンドエッジである約９０ＭＨｚとした際のチューナブルアンテナ装置１０２の利得の周波数特性と、同調回路１１２を省略した図４１に示すアンテナ装置１０１の利得の周波数特性とを対比させて図４７ないし図４９に示す。図４７はチューナブルアンテナ装置１０２の共振周波数を約７６ＭＨｚとした場合であり、マーカ１で示すチューナブルアンテナ装置１０２の利得は、同調回路１１２を備えていないアンテナ装置１０１の利得より約２．５ｄＢ高くなることが分かる。また、図４８はチューナブルアンテナ装置１０２の共振周波数を約８３ＭＨｚとした場合であり、マーカ２で示すチューナブルアンテナ装置１０２の利得は、同調回路１１２を備えていないアンテナ装置１０１の利得とほぼ同等となることが分かる。 Next, by adjusting the positive voltage Vt applied to the tuning circuit 112, the resonant frequency of the tunable antenna device 102 is increased to about 76 MHz, which is the low band edge of the broadcast band of FM radio, and about 83 MHz, which is the center frequency. 47 to 49 by comparing the frequency characteristics of the gain of the tunable antenna device 102 when the band edge is about 90 MHz with the frequency characteristics of the gain of the antenna device 101 shown in FIG. 41 where the tuning circuit 112 is omitted. Shown in. 47 shows the case where the resonant frequency of the tunable antenna device 102 is about 76 MHz, and the gain of the tunable antenna device 102 shown by the marker 1 is about 2.5 dB as compared to the gain of the antenna device 101 not provided with the tuning circuit 112. It turns out that it becomes high. FIG. 48 shows the case where the resonant frequency of the tunable antenna device 102 is about 83 MHz, and the gain of the tunable antenna device 102 indicated by the marker 2 is almost equal to the gain of the antenna device 101 not provided with the tuning circuit 112. It turns out that it becomes.
　さらに、図４９はチューナブルアンテナ装置１０２の共振周波数を約９０ＭＨｚとした場合であり、マーカ３で示すチューナブルアンテナ装置１０２の利得は、同調回路１１２を備えていないアンテナ装置１０１の利得より約４．２ｄＢ高くなることが分かる。
　このように同調回路１１２を設けて、同調回路１１２に印加される正電圧Ｖｔを調整することにより、ＦＭ放送の全帯域においてピーク利得を得ることができるようになり、ＦＭラジオの放送帯域における利得の周波数特性をフラット化することができるようになる。 Further, FIG. 49 shows the case where the resonant frequency of the tunable antenna device 102 is about 90 MHz, and the gain of the tunable antenna device 102 indicated by the marker 3 is about 4 as compared with the gain of the antenna device 101 not provided with the tuning circuit 112. It turns out that it is 2 dB higher.
Thus, by providing the tuning circuit 112 and adjusting the positive voltage Vt applied to the tuning circuit 112, it is possible to obtain peak gain in the entire band of the FM broadcast, and gain in the broadcast band of the FM radio Can be flattened.
　上記したように同調回路を備えるチューナブルアンテナ装置とすることにより、利得の周波数特性を向上することができるが、同調回路を構成しているバリキャップダイオードは、強電界下においては受信信号に歪を発生させるという問題点があった。
　そこで、本発明は小型化・狭面積化されたアンテナでありながら利得を確保し、強電界下において歪が発生することのないチューナブルアンテナ装置を提供することを目的としている。 As described above, the tunable antenna device including the tuning circuit can improve the frequency characteristics of the gain, but the varicap diode forming the tuning circuit is distorted in the received signal under a strong electric field. There was a problem of causing
Therefore, it is an object of the present invention to provide a tunable antenna device which secures a gain while being a miniaturized and narrowed area antenna and in which distortion does not occur under a strong electric field.
　本発明のチューナブルアンテナ装置は、単体では使用周波数帯域に共振しない小型のアンテナと、該アンテナに直列に接続されているローディングコイルと、
　該ローディングコイルと出力端子との間に接続されたインピーダンスを可変することのできる同調回路と、前記ローディングコイルと前記同調回路との接続点とアースとの間に設けられたＡＧＣ回路とを備え、前記ローディングコイルが直列接続された前記アンテナを、前記同調回路のインピーダンスを可変することにより使用周波数帯域内の特定の周波数に共振させることができると共に、前記ＡＧＣ回路から前記アンテナ側を見たインピーダンスが、前記ＡＧＣ回路のインピーダンスに対して約４％以内とされていることを最も主要な特徴としている。 The tunable antenna device according to the present invention comprises a small antenna that does not resonate in a used frequency band alone, a loading coil connected in series to the antenna, and
A tuning circuit capable of varying impedance connected between the loading coil and the output terminal; and an AGC circuit provided between a connection point between the loading coil and the tuning circuit and the ground. The antenna in which the loading coil is connected in series can be resonated at a specific frequency in a used frequency band by varying the impedance of the tuning circuit, and the impedance viewed from the AGC circuit from the AGC circuit is The most important feature is that it is within about 4% of the impedance of the AGC circuit.
　本発明によれば、単体では使用周波数帯域に共振しない小型化・狭面積化されたアンテナとしても、ローディングコイルおよび同調を可変することのできる同調回路を設けると共に、ＡＧＣ回路からアンテナ側を見たインピーダンスが、ＡＧＣ回路のインピーダンスに対して約４％以内としたことから，十分な利得を確保することができる。また、ＡＧＣ回路を設けたことにより強電界下において歪が発生することを防止することができる。 According to the present invention, a loading coil and a tuning circuit capable of varying tuning can be provided as a miniaturized / narrowed antenna which does not resonate in the used frequency band alone, and the antenna side is viewed from the AGC circuit Since the impedance is within about 4% of the impedance of the AGC circuit, a sufficient gain can be secured. Further, by providing the AGC circuit, it is possible to prevent the occurrence of distortion under a strong electric field.
本発明の第１実施例のチューナブルアンテナ装置の構成を示す回路図である。It is a circuit diagram showing composition of a tunable antenna device of a 1st example of the present invention. 本発明にかかるチューナブルアンテナ装置におけるＡＧＣ回路の一例を示す図である。It is a figure which shows an example of the AGC circuit in the tunable antenna apparatus concerning this invention. 本発明の第１実施例の第１周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 1st frequency of a 1st example of the present invention, and the conventional antenna device. 本発明の第１実施例の第２周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 2nd frequency of a 1st example of the present invention, and the conventional antenna device. 本発明の第１実施例の第３周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 3rd frequency of a 1st example of the present invention, and the conventional antenna device. 本発明の第２実施例のチューナブルアンテナ装置の構成を示す回路図である。It is a circuit diagram showing composition of a tunable antenna device of a 2nd example of the present invention. 本発明の第２実施例の第１周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 1st frequency of a 2nd example of the present invention, and the conventional antenna device. 本発明の第２実施例の第２周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 2nd frequency of a 2nd example of the present invention, and the conventional antenna device. 本発明の第２実施例の第３周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 3rd frequency of a 2nd example of the present invention, and the conventional antenna device. 本発明の第２実施例のチューナブルアンテナ装置におけるＡＧＣ回路からアンテナ側の構成を示す回路図である。It is a circuit diagram which shows the structure by the side of an antenna from the AGC circuit in the tunable antenna apparatus of 2nd Example of this invention. 本発明の第２実施例のチューナブルアンテナ装置におけるＡＧＣ回路からみたアンテナ側のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance by the side of the antenna seen from the AGC circuit in the tunable antenna apparatus of 2nd Example of this invention. 本発明の第２実施例のチューナブルアンテナ装置においてローディングコイルの巻き数を減少させた際のＡＧＣ回路からみたアンテナ側のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance by the side of the antenna seen from the AGC circuit at the time of reducing the winding number of a loading coil in the tunable antenna apparatus of 2nd Example of this invention. 本発明の第３実施例のチューナブルアンテナ装置の構成を示す回路図である。It is a circuit diagram showing composition of a tunable antenna device of a 3rd example of the present invention. 本発明の第３実施例の第１周波数に同調したチューナブルアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus tuned to 1st frequency of 3rd Example of this invention. 本発明の第３実施例の第２周波数に同調したチューナブルアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus tuned to 2nd frequency of 3rd Example of this invention. 本発明の第３実施例の第３周波数に同調したチューナブルアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus tuned to the 3rd frequency of 3rd Example of this invention. 本発明の第３実施例の第１周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 1st frequency of a 3rd example of the present invention, and the conventional antenna device. 本発明の第３実施例の第２周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 2nd frequency of a 3rd example of the present invention, and the conventional antenna device. 本発明の第３実施例の第３周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 3rd frequency of a 3rd example of the present invention, and the conventional antenna device. 本発明の第３実施例の第１周波数に同調したチューナブルアンテナ装置におけるＡＧＣ動作時とＡＧＣ非動作時との利得の周波数特性を対比して示す図である。It is a figure which contrasts and shows the frequency characteristic of the gain at the time of AGC operation in the tunable antenna device tuned to the 1st frequency of a 3rd example of the present invention at the time of AGC non-operation. 本発明の第３実施例の第２周波数に同調したチューナブルアンテナ装置におけるＡＧＣ動作時とＡＧＣ非動作時との利得の周波数特性を対比して示す図である。It is a figure which contrasts and shows the frequency characteristic of the gain at the time of AGC operation in the tunable antenna device tuned to the 2nd frequency of a 3rd example of the present invention at the time of AGC non-operation. 本発明の第３実施例の第３周波数に同調したチューナブルアンテナ装置におけるＡＧＣ動作時とＡＧＣ非動作時との利得の周波数特性を対比して示す図である。It is a figure which contrasts and shows the frequency characteristic of the gain at the time of AGC operation in the tunable antenna device tuned to the 3rd frequency of a 3rd example of the present invention at the time of AGC non-operation. 本発明の第３実施例におけるローディングコイルのインダクタンスを調整したチューナブルアンテナ装置の構成を示す回路図である。It is a circuit diagram showing the composition of the tunable antenna device which adjusted the inductance of the loading coil in a 3rd example of the present invention. 図２３に示すチューナブルアンテナ装置のａ１部からみたアンテナ側のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance by the side of the antenna seen from a1 part of the tunable antenna apparatus shown in FIG. 本発明の第４実施例のチューナブルアンテナ装置の構成を示す回路図である。It is a circuit diagram showing composition of a tunable antenna device of a 4th example of the present invention. 本発明の第４実施例の第１周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 1st frequency of a 4th example of the present invention, and the conventional antenna device. 本発明の第４実施例の第２周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 2nd frequency of a 4th example of the present invention, and the conventional antenna device. 本発明の第４実施例の第３周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 3rd frequency of a 4th example of the present invention, and the conventional antenna device. 本発明の第４実施例の第１周波数に同調したチューナブルアンテナ装置におけるＡＧＣ動作時とＡＧＣ非動作時との利得の周波数特性を対比して示す図である。It is a figure which contrasts and shows the frequency characteristic of the gain at the time of AGC operation in the tunable antenna device tuned to the 1st frequency of a 4th example of the present invention at the time of AGC non-operation. 本発明の第４実施例の第２周波数に同調したチューナブルアンテナ装置におけるＡＧＣ動作時とＡＧＣ非動作時との利得の周波数特性を対比して示す図である。It is a figure which contrasts and shows the frequency characteristic of the gain at the time of AGC operation in the tunable antenna device tuned to the 2nd frequency of a 4th example of the present invention, and the time of AGC non-operation. 本発明の第４実施例の第３周波数に同調したチューナブルアンテナ装置におけるＡＧＣ動作時とＡＧＣ非動作時との利得の周波数特性を対比して示す図である。It is a figure which contrasts and shows the frequency characteristic of the gain at the time of AGC operation in the tunable antenna device tuned to the 3rd frequency of a 4th example of the present invention at the time of AGC non-operation. 本発明の第５実施例のチューナブルアンテナ装置の構成を示す回路図である。It is a circuit diagram showing composition of a tunable antenna device of a 5th example of the present invention. 本発明の第５実施例の第１周波数に同調したチューナブルアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus tuned to 1st frequency of 5th Example of this invention. 本発明の第５実施例の第２周波数に同調したチューナブルアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus tuned to 2nd frequency of 5th Example of this invention. 本発明の第５実施例の第３周波数に同調したチューナブルアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus tuned to the 3rd frequency of 5th Example of this invention. 本発明の第５実施例の第１周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 1st frequency of a 5th example of the present invention, and the conventional antenna device. 本発明の第５実施例の第２周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which contrasts and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 2nd frequency of a 5th example of the present invention, and the conventional antenna device. 本発明の第５実施例の第３周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the tunable antenna device tuned to the 3rd frequency of a 5th example of the present invention, and the conventional antenna device. 従来のアンテナ装置の構成を示す回路図である。It is a circuit diagram showing the composition of the conventional antenna device. 従来のアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the conventional antenna device. 従来の他のアンテナ装置の構成を示す回路図である。It is a circuit diagram showing composition of other conventional antenna devices. 従来の他のアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the other conventional antenna device. 従来のチューナブルアンテナ装置の構成を示す回路図である。It is a circuit diagram which shows the structure of the conventional tunable antenna apparatus. 従来の第１周波数に同調したチューナブルアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus tuned to the conventional 1st frequency conventionally. 従来の第２周波数に同調したチューナブルアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus tuned to the conventional 2nd frequency. 従来の第３周波数に同調したチューナブルアンテナ装置のインピーダンスの周波数特性を示すスミスチャートである。It is a Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus tuned to the conventional 3rd frequency. 従来の第１周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of the conventional tunable antenna device and conventional antenna device which were tuned to the conventional 1st frequency. 従来の第２周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which compares and shows the frequency characteristic of the gain of a conventional tunable antenna device and a conventional antenna device tuned to the 2nd conventional frequency. 従来の第３周波数に同調したチューナブルアンテナ装置と従来のアンテナ装置の利得の周波数特性を対比して示す図である。It is a figure which contrasts and shows the frequency characteristic of the gain of the conventional tunable antenna device and the conventional antenna device which were tuned to the conventional 3rd frequency.
１　チューナブルアンテナ装置、２　チューナブルアンテナ装置、３　チューナブルアンテナ装置、４　チューナブルアンテナ装置、５　チューナブルアンテナ装置、１０　アンテナ、１１　ローディングコイル、１１－１　第１ローディングコイル、１１－２　第２ローディングコイル、１１－３　第３ローディングコイル、１１－４　第４ローディングコイル、１２　同調回路、１２ａ　同調コイル、１３　ＡＧＣ回路、１３ａ　制御回路、１４　整合回路、１００　アンテナ装置、１０１　アンテナ装置、１０２　チューナブルアンテナ装置、１１０　アンテナ、１１１　ローディングコイル、１１１－１　ローディングコイル、１１２　同調回路、１１２ａ　同調コイル、ＢＤ１，ＢＤ２　バリキャップダイオード、ＰＩＮ１，ＰＩＮ２　ピンダイオード 1 Tunable antenna device, 2 Tunable antenna device, 3 Tunable antenna device, 4 Tunable antenna device, 5 Tunable antenna device, 10 antenna, 11 loading coil, 11-1 first loading coil, 11-2 second Loading coil, 11-3 third loading coil, 11-4 fourth loading coil, 12 tuning circuit, 12a tuning coil, 13 AGC circuit, 13a control circuit, 14 matching circuit, 100 antenna device, 101 antenna device, 102 tunable Antenna device, 110 antenna, 111 loading coil, 111-1 loading coil, 112 tuning circuit, 112a tuning coil, BD1, BD2 varicap diode, PIN1, PI 2-pin diode
　本発明の第１実施例のチューナブルアンテナ装置の構成の回路図を図１に示す。
　図１に示す第１実施例のチューナブルアンテナ装置１は、アンテナ単体ではＦＭラジオの放送帯域に共振しない小型のアンテナ１０と、アンテナ１０をＦＭ放送の周波数に共振させるために直列に接続されたローディングコイル１１と、ローディングコイル１１と出力端子ＯＵＴとの間に接続されている同調回路１２とを備えている。また、ローディングコイル１１と同調回路１２との接続点とアース間にＡＧＣ回路１３が接続されている。チューナブルアンテナ装置１により受信された受信信号は出力端子ＯＵＴから出力される。同調回路１２は、同調コイル１２ａと逆極性で直列接続された２本のバリキャップダイオードＢＤ１，ＢＤ２からなり、カソード同士が接続されたバリキャップダイオードＢＤ１，ＢＤ２の接続点に抵抗Ｒ１を介して正電圧Ｖｔが印加されている。また、出力端子ＯＵＴとアース間に高周波（ＲＦ）信号を阻止して、出力端子ＯＵＴを直流的にアースするチョークコイルＣＨ１が接続されている。このチョークコイルＣＨ１により、バリキャップダイオードＢＤ１，ＢＤ２のアノードが直流的にアースされることになる。これにより、正電圧Ｖｔの値を変化させることによりバリキャップダイオードＢＤ１，ＢＤ２の容量を可変することができる。 A circuit diagram of the configuration of the tunable antenna device of the first embodiment of the present invention is shown in FIG.
The tunable antenna device 1 according to the first embodiment shown in FIG. 1 is connected in series in order to resonate the antenna 10 with the frequency of the FM broadcast and the small antenna 10 which does not resonate in the broadcast band of the FM radio when the antenna alone is used. A loading coil 11 and a tuning circuit 12 connected between the loading coil 11 and the output terminal OUT are provided. Further, an AGC circuit 13 is connected between the connection point of the loading coil 11 and the tuning circuit 12 and the ground. The received signal received by the tunable antenna device 1 is output from the output terminal OUT. The tuning circuit 12 includes two varicap diodes BD1 and BD2 connected in series in reverse polarity to the tuning coil 12a, and the junction between the varicap diodes BD1 and BD2 whose cathodes are connected is positive via a resistor R1. A voltage Vt is applied. Further, a choke coil CH1 is connected between the output terminal OUT and the ground to block a high frequency (RF) signal and to ground the output terminal OUT in a DC manner. The anodes of the varicap diodes BD1 and BD2 are DC-grounded by the choke coil CH1. Thus, the capacitance of the varicap diodes BD1 and BD2 can be varied by changing the value of the positive voltage Vt.
　ここで、チューナブルアンテナ装置１がＦＭラジオの放送帯域である７６ＭＨｚないし９０ＭＨｚに少なくとも共振するように、同調回路１２における同調コイル１２ａのインダクタンス値とバリキャップダイオードＢＤ１，ＢＤ２の可変容量範囲が選択されている。この同調回路１２において正電圧Ｖｔを高くしていくと、バリキャップダイオードＢＤ１，ＢＤ２のカソード－アノード間に印加される逆電圧が高くなってバリキャップダイオードＢＤ１，ＢＤ２の容量値が小さくなることから、チューナブルアンテナ装置１全体の共振周波数は高くなる。逆に、同調回路１２における正電圧Ｖｔを低くしていくと、バリキャップダイオードＢＤ１，ＢＤ２のカソード－アノード間に印加される逆電圧が低くなってバリキャップダイオードＢＤ１，ＢＤ２の容量値が大きくなることから、チューナブルアンテナ装置１全体の共振周波数は低くなる。このように、同調回路１２において正電圧Ｖｔの値を調整することにより、同調回路１２のインピーダンスが可変されて、チューナブルアンテナ装置１全体の共振周波数がＦＭラジオの放送帯域内の特定の周波数に同調されるようになる。なお、ローディングコイル１１と同調回路１２との接続点とアース間に接続されているＡＧＣ回路１３は、強電界下においてバリキャップダイオードＢＤ１，ＢＤ２の非直線性により受信信号に歪が発生しないように、強電界下にバリキャップダイオードＢＤ１，ＢＤ２に入力される受信信号を減衰させる制御を行っている。 Here, the inductance value of the tuning coil 12a in the tuning circuit 12 and the variable capacitance range of the varicap diodes BD1 and BD2 are selected such that the tunable antenna device 1 resonates at least in the 76 MHz to 90 MHz broadcast band of FM radio. ing. As the positive voltage Vt is increased in the tuning circuit 12, the reverse voltage applied between the cathode and the anode of the varicap diodes BD1 and BD2 is increased, and the capacitance value of the varicap diodes BD1 and BD2 is reduced. The resonant frequency of the tunable antenna device 1 as a whole becomes high. Conversely, when the positive voltage Vt in the tuning circuit 12 is lowered, the reverse voltage applied between the cathode and the anode of the varicap diodes BD1 and BD2 is reduced, and the capacitance value of the varicap diodes BD1 and BD2 is increased. Thus, the resonant frequency of the tunable antenna device 1 as a whole is lowered. In this manner, by adjusting the value of the positive voltage Vt in the tuning circuit 12, the impedance of the tuning circuit 12 is varied, so that the resonant frequency of the entire tunable antenna device 1 becomes a specific frequency within the broadcast band of the FM radio. Become tuned. The AGC circuit 13 connected between the connection point of the loading coil 11 and the tuning circuit 12 and the ground does not generate distortion in the received signal due to non-linearity of the varicap diodes BD1 and BD2 under a strong electric field. Control is performed to attenuate the reception signal input to the varicap diodes BD1 and BD2 under a strong electric field.
　このＡＧＣ回路１３の回路例を図２に示すが、図２に示すＡＧＣ回路１３は制御回路１３ａと、順方向になるよう直列接続された２本のピンダイオードＰＩＮ１，ＰＩＮ２とを備えている。ピンダイオードＰＩＮ２のカソードはアースされ、ピンダイオードＰＩＮ１のアノードはバイパスコンデンサＣ２により高周波的にアースされている。また、直列接続されたピンダイオードＰＩＮ１のカソードとＰＩＮダイオードＰＩＮ２のアノードとの接続点が、コンデンサＣ１を介してローディングコイル１１と同調回路１２との接続点に接続されている。ＡＧＣ回路１３は、出力端子ＯＵＴに出力される受信信号のレベルが所定値を超えないようにレベル制御している。すなわち、出力端子ＯＵＴからの受信号が制御回路１３ａに入力され、制御回路１３ａは入力された受信信号のレベルに応じた直流電圧値の制御信号を出力する。この制御信号はピンダイオードＰＩＮ１，ＰＩＮ２の直列回路とアース間に印加され、制御信号の直流電圧値に応じて直列接続されたピンダイオードＰＩＮ１，ＰＩＮ２の抵抗値が可変されるようになる。 A circuit example of this AGC circuit 13 is shown in FIG. 2, but the AGC circuit 13 shown in FIG. 2 comprises a control circuit 13a and two pin diodes PIN1 and PIN2 connected in series so as to be in the forward direction. The cathode of the pin diode PIN2 is grounded, and the anode of the pin diode PIN1 is grounded at a high frequency by the bypass capacitor C2. Further, a connection point between the cathode of the pin diode PIN1 and the anode of the PIN diode PIN2 connected in series is connected to the connection point between the loading coil 11 and the tuning circuit 12 via the capacitor C1. The AGC circuit 13 performs level control so that the level of the reception signal output to the output terminal OUT does not exceed a predetermined value. That is, the reception signal from the output terminal OUT is input to the control circuit 13a, and the control circuit 13a outputs a control signal of a DC voltage value corresponding to the level of the input reception signal. The control signal is applied between the series circuit of the pin diodes PIN1 and PIN2 and the ground, and the resistance value of the pin diodes PIN1 and PIN2 connected in series can be varied according to the DC voltage value of the control signal.
　これにより、強電界下においては制御回路１３ａから出力される直流電圧値が高くなって、ピンダイオードＰＩＮ１，ＰＩＮ２の抵抗値が小さくなることから、受信信号はコンデンサＣ１－ピンダイオードＰＩＮ１－バイパスコンデンサＣ２－アースの経路と、コンデンサＣ１－ピンダイオードＰＩＮ２－アースの経路とで減衰するようになる。これにより、ＡＧＣ回路１３により、バリキャップダイオードＢＤ１，ＢＤ２に入力される受信信号のレベルが所定値を超えないようにレベル制御される。また、弱電界下においては制御回路１３ａから出力される直流電圧値が低くなって、ピンダイオードＰＩＮ１，ＰＩＮ２の抵抗値が大きくなることから、受信信号は上記の経路ではほぼ減衰しないようになる。このように第１実施例のチューナブルアンテナ装置１では、強電界下においてバリキャップダイオードＢＤ１，ＢＤ２が受信信号に歪を与えることを、ＡＧＣ回路１３を設けたことにより防止することができるようになる。 As a result, the DC voltage value output from control circuit 13a is increased under a strong electric field, and the resistance values of pin diodes PIN1 and PIN2 are reduced. Therefore, the received signal is a capacitor C1-pin diode PIN1-bypass capacitor C2. Attenuation occurs in the path of ground and in the path of capacitor C1-pin diode PIN2-ground. Thereby, the AGC circuit 13 performs level control so that the level of the reception signal input to the varicap diodes BD1 and BD2 does not exceed a predetermined value. Further, under a weak electric field, the DC voltage value output from the control circuit 13a decreases, and the resistance values of the pin diodes PIN1 and PIN2 increase, so that the received signal is not substantially attenuated in the above path. As described above, in the tunable antenna device 1 of the first embodiment, it is possible to prevent the varicap diodes BD1 and BD2 from giving distortion to the reception signal under a strong electric field by providing the AGC circuit 13. Become.
　第１実施例のチューナブルアンテナ装置１において、同調回路１２に印加される正電圧Ｖｔを調整してチューナブルアンテナ装置１の共振周波数をＦＭラジオの放送帯域の低いバンドエッジである約７６ＭＨｚ、中心周波数である約８３ＭＨｚ、高いバンドエッジである約９０ＭＨｚとした際の第１実施例のチューナブルアンテナ装置１の利得の周波数特性と、同調回路１２を備えていない図４１に示す従来のアンテナ装置１０１の利得の周波数特性とを対比させて図３ないし図５に示す。図３は、正電圧Ｖｔを調整してチューナブルアンテナ装置１の共振周波数を約７６ＭＨｚとした場合であり、図３を参照するとマーカ１で示す第１実施例のチューナブルアンテナ装置１の利得は、従来のアンテナ装置１０１の利得より約２．４ｄＢ高くなることが分かる。また、図４は正電圧Ｖｔを調整してチューナブルアンテナ装置１の共振周波数を約８３ＭＨｚとした場合であり、図４を参照すると、マーカ２で示す８３ＭＨｚにおけるチューナブルアンテナ装置１の利得は、従来のアンテナ装置１０１の利得より約１．０ｄＢ低くなることが分かる。 In the tunable antenna device 1 of the first embodiment, the resonance frequency of the tunable antenna device 1 is adjusted to about 76 MHz which is the low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12 The frequency characteristic of the gain of the tunable antenna device 1 of the first embodiment when the frequency is about 83 MHz and the high band edge is about 90 MHz, and the conventional antenna device 101 shown in FIG. 41 without the tuning circuit 12 3 to 5 in comparison with the frequency characteristic of the gain of. FIG. 3 shows the case where the resonance frequency of the tunable antenna device 1 is about 76 MHz by adjusting the positive voltage Vt. Referring to FIG. 3, the gain of the tunable antenna device 1 of the first embodiment shown by the marker 1 is It can be seen that the gain of the conventional antenna device 101 is about 2.4 dB higher. Further, FIG. 4 is a case where the resonance frequency of the tunable antenna device 1 is adjusted to about 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 4, the gain of the tunable antenna device 1 at 83 MHz indicated by the marker 2 is It can be seen that the gain is about 1.0 dB lower than the gain of the conventional antenna device 101.
　さらに、図５は正電圧Ｖｔを調整してチューナブルアンテナ装置１の共振周波数を約９０ＭＨｚとした場合であり、図５を参照すると、マーカ３で示す９０ＭＨｚにおける第１実施例のチューナブルアンテナ装置１の利得は、従来のアンテナ装置１０１の利得より約１．３ｄＢ高くなることが分かる。なお、図３ないし図５における「Ｒｅｆ１」は固定の第１レファレンス値であり、以降の図においても同様とされる。また、測定系のインピーダンスは７５Ωとされており、以降の図においても同様とされる。
　このように、第１実施例のチューナブルアンテナ装置１は、歪の発生を防止するようにＡＧＣ回路１３を設けているが、ＡＧＣ回路１３を設けたためにＦＭラジオの放送帯域において利得が若干減少するようになる。ただし、ＦＭラジオの放送帯域における利得の周波数特性はフラット化されている。 Further, FIG. 5 shows the case where the resonant frequency of the tunable antenna device 1 is adjusted to about 90 MHz by adjusting the positive voltage Vt. Referring to FIG. 5, the tunable antenna device of the first embodiment at 90 MHz indicated by the marker 3 It can be seen that the gain of 1 is about 1.3 dB higher than the gain of the conventional antenna device 101. Note that “Ref 1” in FIGS. 3 to 5 is a fixed first reference value, and the same applies to the subsequent figures. Further, the impedance of the measurement system is 75Ω, and the same applies to the subsequent drawings.
Thus, although the tunable antenna device 1 of the first embodiment is provided with the AGC circuit 13 to prevent the occurrence of distortion, the gain is slightly reduced in the broadcast band of the FM radio because the AGC circuit 13 is provided. You will come to However, the frequency characteristic of the gain in the broadcast band of FM radio is flattened.
　次に、ＡＧＣ回路１３における利得の減少を極力抑制するように改良したＡＧＣ回路１３’を備える本発明の第２実施例のチューナブルアンテナ装置２の構成を示す回路図を図６に示す。
　図６に示す第２実施例のチューナブルアンテナ装置２はＡＧＣ回路１３’の構成が異なるだけであり、他の構成は同様とされているのでＡＧＣ回路１３’についてだけ説明するものとする。第１実施例のチューナブルアンテナ装置１において、アンテナ１０から同調回路１２に供給される受信信号はＡＧＣ回路１３の両端に生じた受信信号となる。この受信信号はＡＧＣ回路１３のインピーダンスと、ＡＧＣ回路１３からアンテナ１０側を見たインピーダンスとで分圧された受信信号となる。すなわち、ＡＧＣ回路１３のインピーダンスが低いと、その分だけ分圧された受信信号がロスすることになる。具体的には、第１実施例のチューナブルアンテナ装置１におけるＡＧＣ回路１３においては、２本のピンダイオードＰＩＮ１，ＰＩＮ２のオフ時のインピーダンスが約２．５ｋΩであった。上記のようにこのインピーダンスが低いと利得が減衰することから、第２実施例のチューナブルアンテナ装置２におけるＡＧＣ回路１３’においては、オフ時に約５ｋΩの高インピーダンスを呈するピンダイオードを用いるように変更している。 Next, FIG. 6 is a circuit diagram showing a configuration of a tunable antenna device 2 according to a second embodiment of the present invention provided with an AGC circuit 13 'modified to minimize a decrease in gain in the AGC circuit 13.
The tunable antenna device 2 of the second embodiment shown in FIG. 6 is different only in the configuration of the AGC circuit 13 ', and the other configuration is the same. Therefore, only the AGC circuit 13' will be described. In the tunable antenna device 1 of the first embodiment, the reception signal supplied from the antenna 10 to the tuning circuit 12 is the reception signal generated at both ends of the AGC circuit 13. This reception signal is divided by the impedance of the AGC circuit 13 and the impedance seen from the AGC circuit 13 to the antenna 10 side. That is, if the impedance of the AGC circuit 13 is low, the reception signal divided by that amount will be lost. Specifically, in the AGC circuit 13 in the tunable antenna device 1 of the first embodiment, the impedance of the two pin diodes PIN1 and PIN2 at the off time was about 2.5 kΩ. As described above, since the gain is attenuated if this impedance is low, the AGC circuit 13 'in the tunable antenna device 2 of the second embodiment is changed to use a pin diode that exhibits a high impedance of about 5 kΩ when it is off. doing.
　第２実施例のチューナブルアンテナ装置２において、同調回路１２に印加される正電圧Ｖｔを調整してチューナブルアンテナ装置２の共振周波数をＦＭラジオの放送帯域の低いバンドエッジである約７６ＭＨｚ、中心周波数である約８３ＭＨｚ、高いバンドエッジである約９０ＭＨｚとした際の第２実施例のチューナブルアンテナ装置２の利得の周波数特性と、同調回路１２を備えていない図４１に示す従来のアンテナ装置１０１の利得の周波数特性とを対比させて図７ないし図９に示す。図７は、正電圧Ｖｔを調整してチューナブルアンテナ装置２の共振周波数を約７６ＭＨｚとした場合であり、図７を参照すると、マーカ１で示す７６ＭＨｚにおける第２実施例のチューナブルアンテナ装置２の利得は、従来のアンテナ装置１０１の利得より約２．５ｄＢ高くなることが分かる。また、図８は正電圧Ｖｔを調整してチューナブルアンテナ装置２の共振周波数を約８３ＭＨｚとした場合であり、図８を参照すると、マーカ２で示す８３ＭＨｚにおけるチューナブルアンテナ装置２の利得は、従来のアンテナ装置１０１の利得より約０．５ｄＢ低くなることが分かる。 In the tunable antenna device 2 of the second embodiment, the resonance frequency of the tunable antenna device 2 is adjusted to about 76 MHz, which is the low band edge of the FM radio broadcast band, by adjusting the positive voltage Vt applied to the tuning circuit 12 The frequency characteristic of the gain of the tunable antenna device 2 of the second embodiment when the frequency is about 83 MHz and the high band edge is about 90 MHz, and the conventional antenna device 101 shown in FIG. 41 without the tuning circuit 12 7 to 9 in comparison with the frequency characteristic of the gain of. FIG. 7 shows the case where the resonance frequency of the tunable antenna device 2 is adjusted to about 76 MHz by adjusting the positive voltage Vt. Referring to FIG. 7, the tunable antenna device 2 of the second embodiment at 76 MHz indicated by the marker 1 is shown. It can be seen that the gain of V is approximately 2.5 dB higher than the gain of the conventional antenna device 101. Further, FIG. 8 shows a case where the resonant frequency of the tunable antenna device 2 is adjusted to about 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 8, the gain of the tunable antenna device 2 at 83 MHz indicated by the marker 2 is It can be seen that the gain of the conventional antenna device 101 is about 0.5 dB lower.
　さらに、図９は正電圧Ｖｔを調整してチューナブルアンテナ装置２の共振周波数を約９０ＭＨｚとした場合であり、図９を参照すると、マーカ３で示す９０ＭＨｚにおける第２実施例のチューナブルアンテナ装置２の利得は、従来のアンテナ装置１０１の利得より約２．６ｄＢ高くなることが分かる。
　このように、第２実施例のチューナブルアンテナ装置２は、ＡＧＣ回路１３’を設けることにより歪の発生を防止することができると共に、ＡＧＣ回路１３’によるＦＭラジオの放送帯域における利得の減少を抑制することができるようになる。また、ＦＭラジオの放送帯域における利得の周波数特性はフラット化されている。 Further, FIG. 9 shows the case where the resonant frequency of the tunable antenna device 2 is adjusted to about 90 MHz by adjusting the positive voltage Vt. Referring to FIG. 9, the tunable antenna device of the second embodiment at 90 MHz indicated by the marker 3 It can be seen that the gain of 2 is about 2.6 dB higher than the gain of the conventional antenna device 101.
As described above, the tunable antenna device 2 of the second embodiment can prevent the occurrence of distortion by providing the AGC circuit 13 ', and can reduce the gain in the broadcast band of the FM radio by the AGC circuit 13'. It will be possible to suppress. Also, the frequency characteristic of the gain in the broadcast band of the FM radio is flattened.
　上記した第２実施例のチューナブルアンテナ装置２においては、ＦＭラジオの放送帯域における中域から高域にかけて利得の改善度が低くなっている。そこで、この原因を探るために図１０に示すように同調回路１２以降を切り離して、切り離した点Ａにおけるインピーダンスの周波数特性をみてみる。点Ａからみたインピーダンスの周波数特性を図１１に示すが、図１１を参照するとマーカ２で示す８３ＭＨｚにおけるアンテナインピーダンスは約１５７Ωとなっている。ＡＧＣ回路１３’のインピーダンスは上記したように約５ｋΩであり、約１５７Ωのアンテナインピーダンスは約５ｋΩの約３．１４％になる。このように、アンテナインピーダンスがＡＧＣ回路１３’のインピーダンスの３％以上となったことが、８３ＭＨｚにおいて約０．５ｄＢの利得の減衰を招くものと考えられる。
　この利得の減衰の理由は、同調回路１２に供給される受信信号はＡＧＣ回路１３’の両端に生じた受信信号となり、この受信信号はＡＧＣ回路１３’のインピーダンスと、ＡＧＣ回路１３’からアンテナ１０側を見たインピーダンスとで分圧された受信信号となるからである。 In the tunable antenna device 2 of the second embodiment described above, the degree of improvement of the gain is low from the mid band to the high band in the broadcasting band of the FM radio. Therefore, in order to investigate this cause, as shown in FIG. 10, the tuning circuit 12 and subsequent sections are separated, and the frequency characteristics of the impedance at the separated point A are examined. The frequency characteristics of the impedance viewed from the point A are shown in FIG. 11. Referring to FIG. 11, the antenna impedance at 83 MHz indicated by the marker 2 is about 157 Ω. The impedance of the AGC circuit 13 'is about 5 kΩ as described above, and the antenna impedance of about 157 Ω is about 3.14% of about 5 kΩ. Thus, the fact that the antenna impedance is 3% or more of the impedance of the AGC circuit 13 'is considered to cause about 0.5 dB of gain attenuation at 83 MHz.
The reason for this gain attenuation is that the reception signal supplied to the tuning circuit 12 is a reception signal generated at both ends of the AGC circuit 13 ′, and this reception signal is the impedance of the AGC circuit 13 ′ and the antenna circuit 10 from the AGC circuit 13 ′. This is because the received signal is divided by the impedance viewed from the side.
　そこで、ローディングコイル１１のインダクタンス値を下げるように巻き数を減らし、ローディングコイル１１のインダクタンス値を若干下げた際の図１０の点Ａからみたインピーダンスの周波数特性を図１２に示す。図１２を参照するとマーカ１で示す７６ＭＨｚからマーカ３で示す９０ＭＨｚまでの帯域内における最大インピーダンスが約１２０Ωとなっている。これにより、ＡＧＣ回路１３’のインピーダンス（約５ｋΩ）に対するＦＭラジオの放送帯域内におけるアンテナインピーダンス（１２０Ω）は最大２．４％と３％未満となり、本発明にかかるチューナブルアンテナ装置の中域から高域にかけて利得を改善することが可能となる。 Therefore, FIG. 12 shows frequency characteristics of impedance as viewed from point A in FIG. 10 when the number of turns is reduced so as to lower the inductance value of the loading coil 11 and the inductance value of the loading coil 11 is slightly reduced. Referring to FIG. 12, the maximum impedance in the band from 76 MHz indicated by marker 1 to 90 MHz indicated by marker 3 is about 120 Ω. As a result, the antenna impedance (120Ω) in the broadcast band of the FM radio with respect to the impedance (about 5 kΩ) of the AGC circuit 13 ′ becomes 2.4% and 3% at maximum, and from the middle band of the tunable antenna device It is possible to improve the gain in the high region.
　上記の結果に基づいて中域から高域にかけての利得を改善する本発明の第３実施例のチューナブルアンテナ装置３の構成を示す回路図を図１３に示す。第３実施例のチューナブルアンテナ装置３は、中域から高域にかけて利得を改善できるように、アンテナ１０に接続されている第１ローディングコイル１１－１の巻き数を減らしてインダクタンス値を下げている。そして、第１ローディングコイル１１－１のインダクタンス値を下げたことを補うために、第２ローディングコイル１１－２を第１ローディングコイル１１－１に直列に接続している。これにより、第１ローディングコイル１１－１のインダクタンス値を下げても、第２ローディングコイル１１－２の作用によりアンテナ１０はＦＭラジオの放送帯域に共振するようになる。また、約５ｋΩのインピーダンスとされたＡＧＣ回路１３’は第１ローディングコイル１１－１と第２ローディングコイル１１－２との接続点とアース間に接続されている。そして、第２ローディングコイル１１－２と出力端子ＯＵＴとの間に同調回路１２が接続されており、チューナブルアンテナ装置３の受信信号は出力端子ＯＵＴから出力される。 A circuit diagram showing a configuration of a tunable antenna device 3 according to a third embodiment of the present invention for improving the gain in the middle to high frequencies based on the above result is shown in FIG. In the tunable antenna device 3 of the third embodiment, the number of turns of the first loading coil 11-1 connected to the antenna 10 is reduced to reduce the inductance value so that the gain can be improved in the middle to high regions. There is. The second loading coil 11-2 is connected in series to the first loading coil 11-1 in order to compensate for the reduction in the inductance value of the first loading coil 11-1. Thus, even if the inductance value of the first loading coil 11-1 is lowered, the antenna 10 resonates in the broadcast band of the FM radio by the action of the second loading coil 11-2. Further, an AGC circuit 13 'having an impedance of about 5 kΩ is connected between the connection point of the first loading coil 11-1 and the second loading coil 11-2 and the ground. The tuning circuit 12 is connected between the second loading coil 11-2 and the output terminal OUT, and the reception signal of the tunable antenna device 3 is output from the output terminal OUT.
　本発明の第３実施例にかかるチューナブルアンテナ装置３のインピーダンスの周波数特性を示すスミスチャートを図１４ないし図１６に示す。図１４は、同調回路１２に印加される正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数を約７６ＭＨｚにした際の第３実施例のチューナブルアンテナ装置３のインピーダンスの周波数特性である。図１４に示すスミスチャートを参照すると、マーカ１で示すようにＦＭラジオの放送帯域の低いバンドエッジである７６ＭＨｚにほぼ共振して低いインピーダンスとなっていることが分かる。図１５は、正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数を約８３ＭＨｚにした際の第３実施例のチューナブルアンテナ装置３のインピーダンスの周波数特性である。図１５に示すスミスチャートを参照すると、マーカ２で示すようにＦＭラジオの放送帯域の中心周波数とされる８３ＭＨｚにほぼ共振して低いインピーダンスとなっていることが分かる。図１６は、正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数を約９０ＭＨｚにした際の第３実施例のチューナブルアンテナ装置３のインピーダンスの周波数特性である。図１６に示すスミスチャートを参照すると、マーカ３で示すようにＦＭラジオの放送帯域の高いバンドエッジである９０ＭＨｚにほぼ共振して低いインピーダンスとなっていることが分かる。 The Smith chart which shows the frequency characteristic of the impedance of the tunable antenna apparatus 3 concerning 3rd Example of this invention is shown in FIG. 14 thru | or FIG. FIG. 14 shows the frequency characteristic of the impedance of the tunable antenna device 3 of the third embodiment when the resonant frequency of the tunable antenna device 3 is set to about 76 MHz by adjusting the positive voltage Vt applied to the tuning circuit 12 . Referring to the Smith chart shown in FIG. 14, it can be seen that, as indicated by the marker 1, it has a low impedance by resonating approximately at 76 MHz which is the low band edge of the broadcast band of the FM radio. FIG. 15 shows the frequency characteristics of the impedance of the tunable antenna device 3 of the third embodiment when the resonant frequency of the tunable antenna device 3 is adjusted to about 83 MHz by adjusting the positive voltage Vt. Referring to the Smith chart shown in FIG. 15, it can be seen that, as shown by the marker 2, it has a low impedance by resonating approximately at 83 MHz which is the center frequency of the broadcast band of the FM radio. FIG. 16 is a frequency characteristic of the impedance of the tunable antenna device 3 of the third embodiment when the resonant frequency of the tunable antenna device 3 is adjusted to about 90 MHz by adjusting the positive voltage Vt. Referring to the Smith chart shown in FIG. 16, it can be seen that, as indicated by the marker 3, the impedance is low resonance by resonating substantially at 90 MHz, which is the high band edge of the broadcast band of the FM radio.
　次に、第３実施例のチューナブルアンテナ装置３において、同調回路１２に印加される正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数をＦＭラジオの放送帯域の低いバンドエッジである約７６ＭＨｚ、中心周波数である約８３ＭＨｚ、高いバンドエッジである約９０ＭＨｚとした際の第３実施例のチューナブルアンテナ装置３の利得の周波数特性と、同調回路１２を備えていない図４１に示す従来のアンテナ装置１０１の利得の周波数特性とを対比させて図１７ないし図１９に示す。図１７は、正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数を７６ＭＨｚとした場合であり、図１７を参照すると、マーカ１で示す７６ＭＨｚにおける第３実施例のチューナブルアンテナ装置３の利得は、従来のアンテナ装置１０１の利得より約２．２ｄＢ高くなることが分かる。また、図１８は正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数を８３ＭＨｚとした場合であり、図１８を参照すると、マーカ２で示す８３ＭＨｚにおける第３実施例のチューナブルアンテナ装置３の利得は、従来のアンテナ装置１０１の利得とほぼ同等となることが分かる。 Next, in the tunable antenna device 3 of the third embodiment, the resonant voltage of the tunable antenna device 3 is adjusted to a low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12. The frequency characteristic of the gain of the tunable antenna device 3 of the third embodiment when 76 MHz, center frequency is about 83 MHz, and high band edge is about 90 MHz, and the prior art shown in FIG. 41 without the tuning circuit 12 The frequency characteristics of the gain of the antenna device 101 are shown in contrast in FIGS. 17 to 19. FIG. 17 shows the case where the resonant frequency of the tunable antenna device 3 is 76 MHz by adjusting the positive voltage Vt. Referring to FIG. 17, the tunable antenna device 3 of the third embodiment at 76 MHz indicated by the marker 1 is shown. It can be seen that the gain is about 2.2 dB higher than the gain of the conventional antenna device 101. 18 shows the case where the resonant frequency of the tunable antenna device 3 is 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 18, the tunable antenna device 3 of the third embodiment at 83 MHz indicated by the marker 2 is shown. It can be seen that the gain of V is approximately equal to the gain of the conventional antenna device 101.
　さらに、図１９は正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数を９０ＭＨｚとした場合であり、図１９を参照すると、マーカ３で示す９０ＭＨｚにおける第３実施例のチューナブルアンテナ装置３の利得は、従来のアンテナ装置１０１の利得より約３．９ｄＢ高くなることが分かる。
　このように、第３実施例のチューナブルアンテナ装置３は、ＡＧＣ回路１３’を設けることにより歪の発生を防止することができる。また、ローディングコイルをローディングコイル１１－１，１１－２の２つに分割して、２つのローディングコイル１１－１，１１－２の接続点とアース間にＡＧＣ回路１３’を接続することにより、ＦＭラジオの放送帯域における中域から高域にかけての利得を向上して、ＦＭラジオの放送帯域における利得の周波数特性をよりフラット化することができる。 Further, FIG. 19 shows the case where the resonance frequency of the tunable antenna device 3 is 90 MHz by adjusting the positive voltage Vt. Referring to FIG. 19, the tunable antenna device 3 of the third embodiment at 90 MHz indicated by the marker 3 is shown. It can be seen that the gain of is approximately 3.9 dB higher than the gain of the conventional antenna device 101.
Thus, the tunable antenna device 3 of the third embodiment can prevent the occurrence of distortion by providing the AGC circuit 13 '. Further, the loading coil is divided into two loading coils 11-1 and 11-2, and an AGC circuit 13 'is connected between the connection point of the two loading coils 11-1 and 11-2 and the ground. The mid-to-high band gain in the FM radio broadcast band can be improved to further flatten the frequency characteristic of the gain in the FM radio broadcast band.
　次に、第３実施例のチューナブルアンテナ装置３において、同調回路１２に印加される正電圧Ｖｔを調整して同調回路１２の共振周波数をＦＭラジオの放送帯域の低いバンドエッジである約７６ＭＨｚ、中心周波数である約８３ＭＨｚ、高いバンドエッジである約９０ＭＨｚとした際のＡＧＣ回路１３’が動作している時とＡＧＣ回路１３’が動作していない（ピンダイオードＰＩＮ１，ＰＩＮ２がオフして非動作）時の第３実施例のチューナブルアンテナ装置３の利得の周波数特性を図２０ないし図２２に示す。図２０は、正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数を７６ＭＨｚとした場合であり、図２０を参照すると、マーカ１で示す７６ＭＨｚにおける第３実施例のチューナブルアンテナ装置３において、ＡＧＣ回路１３’非動作時に比べてＡＧＣ回路１３’動作時の利得は４０ｄＢ以上減衰していることが分かる。また、図２１は正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数を８３ＭＨｚとした場合であり、図２１を参照すると、マーカ２で示す８３ＭＨｚにおける第３実施例のチューナブルアンテナ装置３において、ＡＧＣ回路１３’非動作時に比べてＡＧＣ回路１３’動作時の利得は約１５ｄＢしか減衰していないことが分かる。図２２は正電圧Ｖｔを調整してチューナブルアンテナ装置３の共振周波数を９０ＭＨｚとした場合であり、図２２を参照すると、マーカ３で示す９０ＭＨｚにおける第３実施例のチューナブルアンテナ装置３において、ＡＧＣ回路１３’非動作時に比べてＡＧＣ回路１３’動作時の利得は４０ｄＢ以上減衰していることが分かる。なお、図２０ないし図２２における「Ｒｅｆ２」は固定の第２レファレンス値であり、以降の図においても同様とされる。このように、第３実施例のチューナブルアンテナ装置３においては、ＡＧＣ回路１３’が動作した際に８３ＭＨｚ近傍においては十分な減衰量が得られず、強電界下において歪が発生する恐れがある。 Next, in the tunable antenna device 3 of the third embodiment, the positive voltage Vt applied to the tuning circuit 12 is adjusted to set the resonance frequency of the tuning circuit 12 to about 76 MHz, which is the low band edge of the FM radio broadcast band. When the AGC circuit 13 'is operating when the center frequency is about 83 MHz and the high band edge is about 90 MHz, and when the AGC circuit 13' is not operating (the pin diodes PIN1 and PIN2 are off and non-operating) The frequency characteristics of the gain of the tunable antenna device 3 according to the third embodiment are shown in FIGS. FIG. 20 shows the case where the resonance frequency of the tunable antenna device 3 is 76 MHz by adjusting the positive voltage Vt. Referring to FIG. 20, in the tunable antenna device 3 of the third embodiment at 76 MHz indicated by the marker 1 It can be seen that the gain at the time of the operation of the AGC circuit 13 'is attenuated by 40 dB or more as compared with the time of the non-operation of the AGC circuit 13'. Further, FIG. 21 shows the case where the resonance frequency of the tunable antenna device 3 is 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 21, the tunable antenna device 3 of the third embodiment at 83 MHz indicated by the marker 2. The gain during the operation of the AGC circuit 13 'is attenuated by only about 15 dB as compared to when the AGC circuit 13' is not in operation. FIG. 22 shows the case where the resonance frequency of the tunable antenna device 3 is adjusted to 90 MHz by adjusting the positive voltage Vt. Referring to FIG. 22, in the tunable antenna device 3 of the third embodiment at 90 MHz indicated by the marker 3 It can be seen that the gain at the time of operation of the AGC circuit 13 'is attenuated by 40 dB or more compared to when the AGC circuit 13' is not at operation. Note that “Ref 2” in FIG. 20 to FIG. 22 is a fixed second reference value, and the same applies to the subsequent figures. As described above, in the tunable antenna device 3 of the third embodiment, a sufficient amount of attenuation can not be obtained in the vicinity of 83 MHz when the AGC circuit 13 'operates, and distortion may occur under a strong electric field. .
　このように、ＡＧＣ回路１３’が動作している時に約８３ＭＨｚに利得のピークが現れるのはアンテナ１０と第１ローディングコイル１１－１との共振周波数が８３ＭＨｚの近傍にあるからと考えられる。そこで、第３実施例のチューナブルアンテナ装置３において図２３に示すａ１点とａ２点との間を切断し、ａ１点から見たインピーダンスの周波数特性をみてみる。すると、アンテナ１０と第１ローディングコイル１１－１との共振周波数が８３ＭＨｚの近傍にあることが確かめられた。このことから、この共振周波数がＦＭラジオの放送帯域外になるように第１ローディングコイル１１－１のインダクタンス値を減少させた。第１ローディングコイル１１－１のインダクタンス値を減少させた場合に、ａ１点からみた第１ローディングコイル１１－１のインピーダンスの周波数特性を図２４に示す。図２４を参照すると、アンテナ１０と第１ローディングコイル１１－１との共振周波数がマーカ４で示す９１．５ＭＨｚとＦＭラジオの放送帯域外になっていることが分かる。 As described above, the peak of the gain appears at about 83 MHz when the AGC circuit 13 'is operating, which is considered to be because the resonance frequency of the antenna 10 and the first loading coil 11-1 is near 83 MHz. Therefore, in the tunable antenna device 3 of the third embodiment, the point a1 and the point a2 shown in FIG. 23 are disconnected, and the frequency characteristic of the impedance viewed from the point a1 is examined. Then, it was confirmed that the resonant frequency of the antenna 10 and the first loading coil 11-1 was near 83 MHz. From this, the inductance value of the first loading coil 11-1 was decreased so that this resonance frequency would be outside the broadcast band of the FM radio. FIG. 24 shows the frequency characteristics of the impedance of the first loading coil 11-1 as viewed from the point a1 when the inductance value of the first loading coil 11-1 is decreased. Referring to FIG. 24, it can be seen that the resonance frequency of the antenna 10 and the first loading coil 11-1 is 91.5 MHz indicated by the marker 4 and outside the broadcast band of the FM radio.
　このように、ＦＭラジオの放送帯域外になるよう第１ローディングコイル１１－１のインダクタンス値を調整した第３ローディングコイル１１－３を備える本発明の第４実施例のチューナブルアンテナ装置４の構成を示す回路図を図２５に示す。
　図２５に示す第４実施例のチューナブルアンテナ装置４は、アンテナ１０に接続されている第３ローディングコイル１１－３と、第３ローディングコイル１１－３に直列に接続された第４ローディングコイル１１－４とを備えている。第３ローディングコイル１１－３の巻き数は第１ローディングコイル１１－１より少なくされインダクタンス値が下がっており、これを補償するように第４ローディングコイル１１－４の巻き数は第２ローディングコイル１１－２より多くされインダクタンス値が上がっている。これにより、アンテナ１０と第３ローディングコイル１１－３とによる共振周波数をＦＭラジオの放送帯域外とすることができ、また、第４ローディングコイル１１－４の作用によりアンテナ１０はＦＭラジオの放送帯域に共振するようになる。また、約５ｋΩのインピーダンスとされたＡＧＣ回路１３’は第３ローディングコイル１１－３と第４ローディングコイル１１－４との接続点とアース間に接続されている。そして、第４ローディングコイル１１－４と出力端子ＯＵＴとの間に同調回路１２が接続されている。アンテナ１０により受信された受信信号は同調回路１２を介して出力端子ＯＵＴから出力される。 Thus, the configuration of the tunable antenna device 4 according to the fourth embodiment of the present invention provided with the third loading coil 11-3 in which the inductance value of the first loading coil 11-1 is adjusted to be outside the broadcast band of FM radio. Is a circuit diagram showing FIG.
The tunable antenna device 4 according to the fourth embodiment shown in FIG. 25 includes a third loading coil 11-3 connected to the antenna 10 and a fourth loading coil 11 connected in series to the third loading coil 11-3. It has -4. The number of turns of the third loading coil 11-3 is smaller than that of the first loading coil 11-1 and the inductance value is lowered. The number of turns of the fourth loading coil 11-4 is the second loading coil 11 so as to compensate for this. The inductance value is higher than -2. As a result, the resonance frequency of the antenna 10 and the third loading coil 11-3 can be set outside the broadcast band of the FM radio, and the antenna 10 is in the broadcast band of the FM radio by the action of the fourth loading coil 11-4. To resonate. Further, an AGC circuit 13 'having an impedance of about 5 kΩ is connected between the connection point of the third loading coil 11-3 and the fourth loading coil 11-4 and the ground. The tuning circuit 12 is connected between the fourth loading coil 11-4 and the output terminal OUT. The received signal received by the antenna 10 is output from the output terminal OUT through the tuning circuit 12.
　ここで、第４実施例のチューナブルアンテナ装置４において、同調回路１２に印加される正電圧Ｖｔを調整してチューナブルアンテナ装置４の共振周波数をＦＭラジオの放送帯域の低いバンドエッジである約７６ＭＨｚ、中心周波数である約８３ＭＨｚ、高いバンドエッジである約９０ＭＨｚとした際の第４実施例のチューナブルアンテナ装置４の利得の周波数特性と、同調回路１２を備えていない図４１に示す従来のアンテナ装置１０１の利得の周波数特性とを対比させて図２６ないし図２８に示す。図２６は、正電圧Ｖｔを調整してチューナブルアンテナ装置４の共振周波数を７６ＭＨｚとした場合であり、図２６を参照すると、マーカ１で示す７６ＭＨｚにおける第４実施例のチューナブルアンテナ装置４の利得は、従来のアンテナ装置１０１の利得より約１．４ｄＢ高くなることが分かる。また、図２７は正電圧Ｖｔを調整してチューナブルアンテナ装置４の共振周波数を８３ＭＨｚとした場合であり、図２７を参照すると、マーカ２で示す８３ＭＨｚにおける第４実施例のチューナブルアンテナ装置４の利得は、従来のアンテナ装置１０１の利得より約０．３ｄＢ低くなることが分かる。 Here, in the tunable antenna device 4 of the fourth embodiment, the resonant voltage of the tunable antenna device 4 is adjusted to a low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12. The frequency characteristic of the gain of the tunable antenna device 4 of the fourth embodiment when 76 MHz, center frequency is about 83 MHz, and high band edge is about 90 MHz, and the conventional circuit shown in FIG. 41 without the tuning circuit 12 The frequency characteristics of the gain of the antenna device 101 are shown in contrast in FIGS. 26 shows the case where the resonance frequency of the tunable antenna device 4 is 76 MHz by adjusting the positive voltage Vt. Referring to FIG. 26, the tunable antenna device 4 of the fourth embodiment at 76 MHz indicated by the marker 1 is shown. It can be seen that the gain is about 1.4 dB higher than the gain of the conventional antenna device 101. 27 shows the case where the resonance frequency of the tunable antenna device 4 is 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 27, the tunable antenna device 4 of the fourth embodiment at 83 MHz indicated by the marker 2 is shown. It can be seen that the gain of is approximately 0.3 dB lower than the gain of the conventional antenna device 101.
　さらに、図２８は正電圧Ｖｔを調整してチューナブルアンテナ装置４の共振周波数を９０ＭＨｚとした場合であり、図２８を参照すると、マーカ３で示す９０ＭＨｚにおける第４実施例のチューナブルアンテナ装置４の利得は、従来のアンテナ装置１０１の利得より約４．２ｄＢ高くなることが分かる。
　このように、第４実施例のチューナブルアンテナ装置４は、第３実施例のチューナブルアンテナ装置３より低域（７６ＭＨｚ近傍）における利得が約０．８ｄＢ減少している。この原因は第３ローディングコイル１１－３のインダクタンス値を少なくした際に、図２４にマーカ１で示されている７６ＭＨｚにおけるインピーダンスが約２００オームになって、ＡＧＣ回路１３’のインピーダンスの３％を超えて４％になるからと考えられる。なお、第４実施例のチューナブルアンテナ装置４は、ＡＧＣ回路１３’により歪の発生を防止することができる。また、２つに分割された第３ローディングコイル１１－３と第４ローディングコイル１１－４とのインダクタンス値を上記のように調整すると共に、２つのローディングコイル１１－３，１１－４の接続点とアース間にＡＧＣ回路１３’を接続することにより、ＦＭラジオの放送帯域における中域から高域にかけての利得が向上するようになり、ＦＭラジオの放送帯域における利得の周波数特性をフラット化することができる。 Further, FIG. 28 shows the case where the resonance frequency of the tunable antenna device 4 is 90 MHz by adjusting the positive voltage Vt. Referring to FIG. 28, the tunable antenna device 4 of the fourth embodiment at 90 MHz indicated by the marker 3. It can be seen that the gain of is approximately 4.2 dB higher than the gain of the conventional antenna device 101.
Thus, in the tunable antenna device 4 of the fourth embodiment, the gain in the lower band (near 76 MHz) of the tunable antenna device 3 of the third embodiment is reduced by about 0.8 dB. The cause of this is that when the inductance value of the third loading coil 11-3 is reduced, the impedance at 76 MHz shown by the marker 1 in FIG. 24 becomes about 200 ohms and 3% of the impedance of the AGC circuit 13 ' It is considered to be beyond 4%. In the tunable antenna device 4 of the fourth embodiment, the occurrence of distortion can be prevented by the AGC circuit 13 '. Further, the inductance value of the third loading coil 11-3 and the fourth loading coil 11-4 divided into two is adjusted as described above, and the connection point between the two loading coils 11-3 and 11-4. By connecting the AGC circuit 13 'between the ground and the ground, the gain from mid to high in the broadcast band of the FM radio is improved, and the frequency characteristic of the gain in the broadcast band of the FM radio is flattened. Can.
　次に、第４実施例のチューナブルアンテナ装置４において、同調回路１２に印加される正電圧Ｖｔを調整してチューナブルアンテナ装置４の共振周波数をＦＭラジオの放送帯域の低いバンドエッジである約７６ＭＨｚ、中心周波数である約８３ＭＨｚ、高いバンドエッジである約９０ＭＨｚとした際のＡＧＣ回路１３’が動作している時とＡＧＣ回路１３’が動作していない（非動作）時の第４実施例のチューナブルアンテナ装置４の利得の周波数特性を図２９ないし図３１に示す。図２９は、正電圧Ｖｔを調整してチューナブルアンテナ装置４の共振周波数を約７６ＭＨｚとした場合であり、図２９を参照すると、マーカ１で示すように７６ＭＨｚにおける第４実施例のチューナブルアンテナ装置４において、ＡＧＣ回路１３’非動作時に比べてＡＧＣ回路１３’動作時の利得は４０ｄＢ以上減衰していることが分かる。また、図３０は正電圧Ｖｔを調整してチューナブルアンテナ装置４の共振周波数を約８３ＭＨｚとした場合であり、図３０を参照すると、マーカ２で示すように８３ＭＨｚにおける第４実施例のチューナブルアンテナ装置４において、ＡＧＣ回路１３’非動作時に比べてＡＧＣ回路１３’動作時の利得は約４０ｄＢ以上減衰していることが分かる。図３１は正電圧Ｖｔを調整してチューナブルアンテナ装置４の共振周波数を約９０ＭＨｚとした場合であり、図３１を参照すると、マーカ３で示すように９０ＭＨｚにおける第４実施例のチューナブルアンテナ装置４において、ＡＧＣ回路１３’非動作時に比べてＡＧＣ回路１３’動作時の利得は３０ｄＢ以上減衰していることが分かる。このように、第４実施例のチューナブルアンテナ装置３においては、２つに分割された第３ローディングコイル１１－３と第４ローディングコイル１１－４とのインダクタンス値を上記のように調整することにより、ＡＧＣ回路１３’が動作した際にＦＭ放送の全帯域内において少なくとも３０ｄＢ以上の十分な減衰量を得ることができ、強電界下において歪が発生することを防止することができる。 Next, in the tunable antenna device 4 of the fourth embodiment, the resonant voltage of the tunable antenna device 4 is adjusted to a low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12. Fourth embodiment when AGC circuit 13 'is operating at 76 MHz, center frequency is about 83 MHz, and high band edge is about 90 MHz, and when AGC circuit 13' is not operating (not operating) The frequency characteristics of the gain of the tunable antenna device 4 are shown in FIGS. FIG. 29 shows the case where the resonance frequency of the tunable antenna device 4 is adjusted to about 76 MHz by adjusting the positive voltage Vt. Referring to FIG. 29, the tunable antenna of the fourth embodiment at 76 MHz as shown by the marker 1 In the device 4, it can be seen that the gain at the time of operation of the AGC circuit 13 'is attenuated by 40 dB or more as compared with the time of non-operation of the AGC circuit 13'. FIG. 30 shows the case where the resonance frequency of the tunable antenna device 4 is adjusted to about 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 30, as shown by the marker 2, the tunable of the fourth embodiment at 83 MHz. In the antenna device 4, it is understood that the gain at the time of operation of the AGC circuit 13 'is attenuated by about 40 dB or more as compared with the time of the non-operation of the AGC circuit 13'. FIG. 31 shows the case where the resonance frequency of the tunable antenna device 4 is adjusted to about 90 MHz by adjusting the positive voltage Vt. Referring to FIG. 31, the tunable antenna device of the fourth embodiment at 90 MHz as shown by the marker 3 It can be understood that the gain at the time of operation of the AGC circuit 13 'is attenuated by 30 dB or more at 4 compared with the time of non-operation of the AGC circuit 13'. Thus, in the tunable antenna device 3 of the fourth embodiment, the inductance values of the third loading coil 11-3 and the fourth loading coil 11-4 divided into two are adjusted as described above. Thus, when the AGC circuit 13 'is operated, a sufficient attenuation amount of at least 30 dB can be obtained in the entire band of the FM broadcast, and the occurrence of distortion under a strong electric field can be prevented.
　次に、本発明の第５実施例のチューナブルアンテナ装置５の構成を示す回路図を図３２に示す。
　図３２に示す第５実施例のチューナブルアンテナ装置５は、第４実施例のチューナブルアンテナ装置４に整合回路を付加した構成とされている。すなわち、第５実施例のチューナブルアンテナ装置５は、アンテナ１０に接続されている第３ローディングコイル１１－３と、第３ローディングコイル１１－３に直列に接続された第４ローディングコイル１１－４とを備えている。これにより、アンテナ１０と第３ローディングコイル１１－３とによる共振周波数をＦＭラジオの放送帯域外とすることができ、また、第４ローディングコイル１１－４の作用によりアンテナ１０はＦＭラジオの放送帯域に共振するようになる。また、約５ｋΩのインピーダンスとされたＡＧＣ回路１３’は第３ローディングコイル１１－３と第４ローディングコイル１１－４との接続点とアース間に接続されている。そして、第４ローディングコイル１１－４と出力端子ＯＵＴとの間に同調回路１２が接続されている。出力端子ＯＵＴとアースとの間には、整合コイルからなる整合回路１４が接続され、チューナブルアンテナ装置５の受信信号は出力端子ＯＵＴから出力される。 Next, FIG. 32 is a circuit diagram showing a configuration of a tunable antenna device 5 according to a fifth embodiment of the present invention.
The tunable antenna device 5 of the fifth embodiment shown in FIG. 32 has a configuration in which a matching circuit is added to the tunable antenna device 4 of the fourth embodiment. That is, the tunable antenna device 5 of the fifth embodiment includes a third loading coil 11-3 connected to the antenna 10 and a fourth loading coil 11-4 connected in series to the third loading coil 11-3. And have. As a result, the resonance frequency of the antenna 10 and the third loading coil 11-3 can be set outside the broadcast band of the FM radio, and the antenna 10 is in the broadcast band of the FM radio by the action of the fourth loading coil 11-4. To resonate. Further, an AGC circuit 13 'having an impedance of about 5 kΩ is connected between the connection point of the third loading coil 11-3 and the fourth loading coil 11-4 and the ground. The tuning circuit 12 is connected between the fourth loading coil 11-4 and the output terminal OUT. A matching circuit 14 composed of a matching coil is connected between the output terminal OUT and the ground, and the reception signal of the tunable antenna device 5 is output from the output terminal OUT.
　本発明の第５実施例にかかるチューナブルアンテナ装置５のインピーダンスの周波数特性を示すスミスチャートを図３３ないし図３５に示す。図３３は、同調回路１２に印加される正電圧Ｖｔを調整してチューナブルアンテナ装置５の共振周波数を約７６ＭＨｚにした際の第５実施例のチューナブルアンテナ装置５のインピーダンスの周波数特性である。図３３に示すスミスチャートを参照すると、マーカ１で示すようにＦＭラジオの放送帯域の低いバンドエッジである７６ＭＨｚに共振していると共に、ほぼ理想的にインピーダンス整合されていることが分かる。この場合の電圧定在波比（ＶＳＷＲ）は約１．１となる。
　図３４は、正電圧Ｖｔを調整してチューナブルアンテナ装置５の共振周波数を約８３ＭＨｚにした際の第５実施例のチューナブルアンテナ装置５のインピーダンスの周波数特性である。図３４に示すスミスチャートを参照すると、マーカ２で示すようにＦＭラジオの放送帯域の中心周波数とされる８３ＭＨｚにほぼ共振し、ほぼインピーダンス整合されていることが分かる。この場合の電圧定在波比（ＶＳＷＲ）は約１．８となる。
　図３５は、正電圧Ｖｔを調整してチューナブルアンテナ装置５の共振周波数を約９０ＭＨｚにした際の第５実施例のチューナブルアンテナ装置５のインピーダンスの周波数特性である。図３５に示すスミスチャートを参照すると、マーカ３で示すようにＦＭラジオの放送帯域の高いバンドエッジである９０ＭＨｚにほぼ共振し、ほぼインピーダンス整合されていることが分かる。この場合の電圧定在波比（ＶＳＷＲ）は約２．３となる。 Smith charts showing the frequency characteristics of the impedance of the tunable antenna device 5 according to the fifth embodiment of the present invention are shown in FIG. 33 to FIG. FIG. 33 shows the frequency characteristics of the impedance of the tunable antenna device 5 of the fifth embodiment when the resonant frequency of the tunable antenna device 5 is set to about 76 MHz by adjusting the positive voltage Vt applied to the tuning circuit 12 . Referring to the Smith chart shown in FIG. 33, it can be seen that, as indicated by the marker 1, it resonates at 76 MHz, which is the low band edge of the broadcast band of the FM radio, and is substantially ideally impedance matched. The voltage standing wave ratio (VSWR) in this case is about 1.1.
FIG. 34 shows the frequency characteristic of the impedance of the tunable antenna device 5 of the fifth embodiment when the resonant frequency of the tunable antenna device 5 is adjusted to about 83 MHz by adjusting the positive voltage Vt. Referring to the Smith chart shown in FIG. 34, it can be seen that, as indicated by the marker 2, it resonates substantially at 83 MHz, which is the center frequency of the broadcast band of the FM radio, and is substantially impedance matched. The voltage standing wave ratio (VSWR) in this case is about 1.8.
FIG. 35 shows the frequency characteristics of the impedance of the tunable antenna device 5 of the fifth embodiment when the resonant frequency of the tunable antenna device 5 is adjusted to about 90 MHz by adjusting the positive voltage Vt. Referring to the Smith chart shown in FIG. 35, it can be seen that, as indicated by the marker 3, it resonates substantially at 90 MHz which is the high band edge of the broadcast band of the FM radio and is substantially impedance matched. The voltage standing wave ratio (VSWR) in this case is about 2.3.
　次に、第５実施例のチューナブルアンテナ装置５において、同調回路１２に印加される正電圧Ｖｔを調整してチューナブルアンテナ装置５の共振周波数をＦＭラジオの放送帯域の低いバンドエッジである約７６ＭＨｚ、中心周波数である約８３ＭＨｚ、高いバンドエッジである約９０ＭＨｚとした際の第５実施例のチューナブルアンテナ装置５の利得の周波数特性と、同調回路１２を備えていない図４１に示す従来のアンテナ装置１０１の利得の周波数特性とを対比させて図３６ないし図３８に示す。図３６は、正電圧Ｖｔを調整してチューナブルアンテナ装置５の共振周波数を約７６ＭＨｚとした場合であり、図３６を参照すると、マーカ１で示す７６ＭＨｚにおける第５実施例のチューナブルアンテナ装置５の利得は、従来のアンテナ装置１０１の利得より約３．９ｄＢ高くなることが分かる。また、図３７は正電圧Ｖｔを調整してチューナブルアンテナ装置５の共振周波数を８３ＭＨｚとした場合であり、図３７を参照すると、マーカ２で示す８３ＭＨｚにおける第５実施例のチューナブルアンテナ装置５の利得は、従来のアンテナ装置１０１の利得より約３．２ｄＢ高くなることが分かる。 Next, in the tunable antenna device 5 of the fifth embodiment, the resonant voltage of the tunable antenna device 5 is adjusted to a low band edge of the broadcast band of the FM radio by adjusting the positive voltage Vt applied to the tuning circuit 12. The frequency characteristic of the gain of the tunable antenna device 5 of the fifth embodiment when 76 MHz, center frequency is about 83 MHz, and high band edge is about 90 MHz, and the prior art shown in FIG. 41 without the tuning circuit 12 The frequency characteristics of the gain of the antenna device 101 are shown in FIGS. 36 to 38 in comparison. 36 shows the case where the resonance frequency of the tunable antenna device 5 is adjusted to about 76 MHz by adjusting the positive voltage Vt. Referring to FIG. 36, the tunable antenna device 5 of the fifth embodiment at 76 MHz indicated by the marker 1 is shown. It can be seen that the gain of is approximately 3.9 dB higher than the gain of the conventional antenna device 101. Further, FIG. 37 shows the case where the resonance frequency of the tunable antenna device 5 is adjusted to 83 MHz by adjusting the positive voltage Vt. Referring to FIG. 37, the tunable antenna device 5 of the fifth example at 83 MHz shown by the marker 2 It can be seen that the gain of V is approximately 3.2 dB higher than the gain of the conventional antenna device 101.
　さらに、図３８は正電圧Ｖｔを調整してチューナブルアンテナ装置５の共振周波数を９０ＭＨｚとした場合であり、図３８を参照すると、マーカ３で示す９０ＭＨｚにおける第５実施例のチューナブルアンテナ装置５の利得は、従来のアンテナ装置１０１の利得より約６．９ｄＢ高くなることが分かる。
　このように、第５実施例のチューナブルアンテナ装置５は、同調回路１２および整合回路１４を設けることにより、最大６．９ｄＢの利得改善をすることができる。また、ＦＭラジオの放送帯域内における利得偏差は、７６ＭＨｚに同調させた際の利得と９０ＭＨｚの利得との差である約２．５ｄＢとなり、ＦＭラジオの放送帯域における利得の周波数特性をよりフラット化することができる。なお、ＡＧＣ回路１３’を設けることにより歪の発生を防止することができる。また、ローディングコイルをインダクタンス値を調整したローディングコイル１１－３，１１－４の２つに分割して、２つのローディングコイル１１－３，１１－４の接続点とアース間にＡＧＣ回路１３’を接続することにより、ＦＭラジオの放送帯域における中域から高域にかけての利得が向上されている。さらに、整合回路１４により出力端子ＯＵＴを直流的にアースすることができることから、チョークコイルＣＨ１を省略することができる。 Further, FIG. 38 shows the case where the resonance frequency of the tunable antenna device 5 is 90 MHz by adjusting the positive voltage Vt. Referring to FIG. 38, the tunable antenna device 5 of the fifth embodiment at 90 MHz indicated by the marker 3 It can be seen that the gain of is approximately 6.9 dB higher than the gain of the conventional antenna device 101.
Thus, by providing the tuning circuit 12 and the matching circuit 14, the tunable antenna device 5 of the fifth embodiment can achieve a gain improvement of up to 6.9 dB. In addition, the gain deviation in the broadcast band of FM radio is about 2.5 dB which is the difference between the gain when tuned to 76 MHz and the gain of 90 MHz, which further flattens the frequency characteristics of the gain in the broadcast band of FM radio can do. Note that the occurrence of distortion can be prevented by providing the AGC circuit 13 '. Also, the loading coil is divided into two loading coils 11-3 and 11-4 whose inductance value is adjusted, and an AGC circuit 13 'is connected between the connection point of the two loading coils 11-3 and 11-4 and the ground. By the connection, the gain from the mid band to the high band in the broadcast band of the FM radio is improved. Furthermore, since the output terminal OUT can be grounded in a direct current manner by the matching circuit 14, the choke coil CH1 can be omitted.
　以上説明した本発明の第１実施例ないし第５実施例のチューナブルアンテナ装置においては、同調回路に印加される正電圧Ｖｔの値を調整することにより、同調回路のインピーダンスが可変されて、各実施例におけるチューナブルアンテナ装置全体の共振周波数がＦＭラジオの放送帯域内の特定の周波数に同調されるようになる。また、本発明の第１実施例ないし第５実施例のチューナブルアンテナ装置においては、ＡＧＣ回路からアンテナ側を見たインピーダンスが、ＡＧＣ回路のインピーダンスに対して約３％以内とされているのが理想的とされるが、上記したように約４％以内とされていても十分な利得を確保することができる。さらに、本発明の第３実施例ないし第５実施例のチューナブルアンテナ装置においては、ＡＧＣ回路のインピーダンスを約５ｋΩとしたが、これに限ることはなく、ＡＧＣ回路からアンテナ側を見たインピーダンスが、ＡＧＣ回路のインピーダンスに対して約４％以内を満足していれば５ｋΩ未満であっても良い。 In the tunable antenna devices according to the first to fifth embodiments of the present invention described above, the impedance of the tuning circuit is varied by adjusting the value of the positive voltage Vt applied to the tuning circuit. The resonant frequency of the entire tunable antenna device in the embodiment comes to be tuned to a specific frequency within the broadcast band of the FM radio. In the tunable antenna devices according to the first to fifth embodiments of the present invention, the impedance seen from the AGC circuit to the antenna side is within about 3% of the impedance of the AGC circuit. Although it is considered ideal, sufficient gain can be secured even if it is within about 4% as described above. Furthermore, in the tunable antenna devices according to the third to fifth embodiments of the present invention, the impedance of the AGC circuit is approximately 5 kΩ, but the impedance is not limited to this. If it satisfies about 4% or less of the impedance of the AGC circuit, it may be less than 5 kΩ.
　さらにまた、ＡＧＣ回路では２つのピンダイオードを使用した回路としたが、これに限ることはなく１つあるいは３つ以上のピンダイオードを使用するＡＧＣ回路としても良い。さらにまた、同調回路では２つのバリキャップダイオードを使用した回路としたが、これに限ることはなく１つあるいは３つ以上のバリキャップダイオードを使用する同調回路としても良い。
　また、整合回路を第１実施例ないし第４実施例のチューナブルアンテナ装置に設けるようにしても良い。整合回路を設けた場合は、出力端子ＯＵＴを直流的にアースするチョークコイルＣＨ１を省略することができる。なお、このチョークコイルＣＨ１の値は、本発明にかかるチューナブルアンテナ装置の共振周波数に影響を与えない値とされている。 Furthermore, although the AGC circuit is a circuit using two pin diodes, it is not limited to this and may be an AGC circuit using one or more pin diodes. Furthermore, although the tuning circuit is a circuit using two varicap diodes, it is not limited to this and may be a tuning circuit using one or more varicap diodes.
Further, the matching circuit may be provided in the tunable antenna device of the first to fourth embodiments. When the matching circuit is provided, the choke coil CH1 that grounds the output terminal OUT in a direct current manner can be omitted. The value of the choke coil CH1 is set to a value that does not affect the resonant frequency of the tunable antenna device according to the present invention.

Claims (4)

  1. 　単体では使用周波数帯域に共振しない小型のアンテナと、
    　該アンテナに直列に接続されているローディングコイルと、
    　該ローディングコイルと出力端子との間に接続されたインピーダンスを可変することのできる同調回路と、
    　前記ローディングコイルと前記同調回路との接続点とアースとの間に設けられたＡＧＣ回路とを備え、
    　前記ローディングコイルが直列接続された前記アンテナを、前記同調回路のインピーダンスを可変することにより使用周波数帯域内の特定の周波数に共振させることができると共に、前記ＡＧＣ回路から前記アンテナ側を見たインピーダンスが、前記ＡＧＣ回路のインピーダンスに対して約４％以内とされていることを特徴とするチューナブルアンテナ装置。     A small antenna that does not resonate in the operating frequency band alone
    A loading coil connected in series to the antenna;
    A tuning circuit capable of varying the impedance connected between the loading coil and the output terminal;
    An AGC circuit provided between a connection point between the loading coil and the tuning circuit and the ground;
    The antenna in which the loading coil is connected in series can be resonated at a specific frequency in a used frequency band by varying the impedance of the tuning circuit, and the impedance viewed from the AGC circuit from the AGC circuit is A tunable antenna device characterized in that it is within about 4% of the impedance of the AGC circuit.
  2. 　単体では使用周波数帯域に共振しないアンテナと、
    　該アンテナに直列に接続されている第１ローディングコイルと第２ローディングコイルとの２つに分割されたローディングコイルと、
    　該ローディングコイルと出力端子との間に接続された同調を可変することのできる同調回路と、
    　前記第１ローディングコイルと前記第２ローディングコイルとの接続点と、アースとの間に設けられたＡＧＣ回路とを備え、
    　前記第１ローディングコイルおよび前記第２ローディングコイルが直列接続された前記アンテナを、前記同調回路の同調を可変することにより使用周波数帯域内の特定の周波数に共振させることができると共に、前記ＡＧＣ回路から前記アンテナ側を見たインピーダンスが、前記ＡＧＣ回路のインピーダンスに対して約４％以内とされていることを特徴とするチューナブルアンテナ装置。     An antenna that does not resonate in the operating frequency band alone
    A loading coil divided in two of a first loading coil and a second loading coil connected in series to the antenna;
    A tuning circuit connected between the loading coil and the output terminal capable of varying tuning;
    An AGC circuit provided between a connection point of the first loading coil and the second loading coil, and the ground;
    The antenna in which the first loading coil and the second loading coil are connected in series can be resonated at a specific frequency within a working frequency band by varying the tuning of the tuning circuit, and from the AGC circuit The tunable antenna device according to claim 1, wherein the impedance viewed from the antenna side is within about 4% of the impedance of the AGC circuit.
  3. 　前記第１ローディングコイルと前記アンテナとの共振周波数が、使用周波数帯域の帯域外に設定されていることを特徴とする請求項２記載のチューナブルアンテナ装置。 The tunable antenna device according to claim 2, wherein a resonant frequency of the first loading coil and the antenna is set outside a band of a working frequency band.
  4. 　前記出力端子とアース間にコイルからなる整合回路が設けられていることを特徴とする請求項１ないし３のいずれかに記載のチューナブルアンテナ装置。 The tunable antenna device according to any one of claims 1 to 3, wherein a matching circuit composed of a coil is provided between the output terminal and the ground.
PCT/JP2011/059341 2010-06-30 2011-04-15 Tunable antenna device WO2012002025A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2010149611A JP5714248B2 (en) 2010-06-30 2010-06-30 Tunable antenna device
JP2010-149611 2010-06-30

Publications (1)

Publication Number Publication Date
WO2012002025A1 true WO2012002025A1 (en) 2012-01-05

Family

ID=45401762

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2011/059341 WO2012002025A1 (en) 2010-06-30 2011-04-15 Tunable antenna device

Country Status (2)

Country Link
JP (1) JP5714248B2 (en)
WO (1) WO2012002025A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02111947U (en) * 1989-02-21 1990-09-07
JPH0548360A (en) * 1991-08-15 1993-02-26 Chiyuunaa Kk Radio receiver
JPH05259770A (en) * 1992-03-12 1993-10-08 Chiyuunaa Kk Radio receiver
JPH09148961A (en) * 1995-11-21 1997-06-06 Murata Mfg Co Ltd Radio transmitter
JPH10209897A (en) * 1997-01-20 1998-08-07 Harada Ind Co Ltd Variable tuning type antenna system

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02111947A (en) * 1988-10-21 1990-04-24 Konica Corp Negative photosensitive composition
JP4060746B2 (en) * 2003-04-18 2008-03-12 株式会社ヨコオ Variable tuning antenna and portable radio using the same

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02111947U (en) * 1989-02-21 1990-09-07
JPH0548360A (en) * 1991-08-15 1993-02-26 Chiyuunaa Kk Radio receiver
JPH05259770A (en) * 1992-03-12 1993-10-08 Chiyuunaa Kk Radio receiver
JPH09148961A (en) * 1995-11-21 1997-06-06 Murata Mfg Co Ltd Radio transmitter
JPH10209897A (en) * 1997-01-20 1998-08-07 Harada Ind Co Ltd Variable tuning type antenna system

Also Published As

Publication number Publication date
JP2012015741A (en) 2012-01-19
JP5714248B2 (en) 2015-05-07

Similar Documents

Publication Publication Date Title
JP4508190B2 (en) Antenna and wireless communication device
KR20010081072A (en) Half-loop antenna
KR19980070946A (en) Car glass antenna device
KR101803101B1 (en) Antenna Having Wideband Feeding Structure and Feeding Method
JP7221945B2 (en) Matching circuit and antenna device
JP2006135995A (en) Antenna module for receiving signal having broadcasting frequency band
US10033091B2 (en) Impedance matching circuit
JP2007538450A (en) 3-band TV-RF input circuit
US6933984B2 (en) Television tuner which maintains UHF band tuning circuit bandwidth constant in low to high band range
WO2012002025A1 (en) Tunable antenna device
US5151708A (en) Shortened mast antenna with compensating circuits
US6864924B2 (en) Television tuner input circuit having satisfactory selection properties at high band reception
EP2091104A1 (en) Antenna device
JPH10126220A (en) Antenna-tuning circuit
EP0387003B1 (en) A shortened mast antenna with compensated circuits
US7212167B2 (en) Integrated loop antenna for vehicular applications
JP5493727B2 (en) Filter device for glass antenna and window glass for vehicle
JP2009044561A (en) Antenna matching circuit
KR101805319B1 (en) A Multiband omni antenna using the diplexer matching network
WO2013183356A1 (en) Antenna system and antenna amplifier
JP3127711B2 (en) Electronic tuner
JP3102261B2 (en) Electronic tuner
US20180152154A1 (en) Radio frequency power amplifier and wireless communications device
JPH11191712A (en) Glass antenna system for automobile
JPH098527A (en) Glass antenna system for automobile

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 11800495

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 11800495

Country of ref document: EP

Kind code of ref document: A1