JP2010068118A - Tuning type antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tuning type antenna for reducing substrate noise and improving reception sensitivity. <P>SOLUTION: The tuning type antenna 1 includes a wave receiving element 4 comprising a conductor 3 formed on a substrate 2 and receiving external radio waves, a wave reception tuning circuit 5 connected to one end of the wave receiving element 4 for adjusting the electric length of the wave receiving element 4 in accordance with the radio waves, and a reception circuit 6 for extracting power appearing in the wave receiving element 4 as reception signals. The tuning type antenna also includes a transmission line 8 comprising a conductor 7 formed on the substrate 2 and transmitting electric noise, and a power combining circuit 9 for combining the power appearing in the transmission line 8 with the power appearing in the wave receiving element 4 with opposite phases and outputting it to the reception circuit 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tuning antenna that reduces substrate noise and improves reception sensitivity.

  In order to receive radio waves of terrestrial digital broadcasting with a portable terminal such as a notebook computer or a cellular phone, a small antenna that can be stored in the portable terminal is required. A tuned antenna is used for this purpose.

  As shown in FIG. 3, a conventional tunable antenna 101 includes a wave receiving element 102 made of a conductor (not shown) formed on a substrate (not shown) and receiving external radio waves, and a wave receiving element. A receiving tuning circuit 103 that is connected to one end of 102 and adjusts the electrical length of the receiving element 102 in accordance with the radio wave, and a receiving circuit 104 that extracts power appearing in the receiving element 102 as a received signal.

  Although not shown, the substrate is accommodated in a housing of a device such as a portable terminal.

  The wave receiving element 102 is formed by providing a conductor with a predetermined length. The receiving element 102 is branched into two branches at one end opposite to one end to which the receiving tuning circuit 103 is connected, and the end of one of the branches is grounded to the other branch. Is connected to the input of the receiving circuit 104.

  In the reception tuning circuit 103, a variable capacitance element 105 is used as an element for adjusting the electrical length. There is a variable capacitance diode as the variable capacitance element 105. A variable capacitor 105 and a DC blocking capacitor 106 are inserted in series between one end of the wave receiving element 102 and the ground, and a high frequency blocking resistor 107 is connected to the connection point between the variable capacitor 105 and the DC blocking capacitor 106. The control voltage from the frequency control voltage source 108 is applied via the.

  As described above, the receiving circuit 104 is connected to the end of the branch of the wave receiving element 102 and is configured by an amplifier.

  When the control voltage from the frequency control voltage source 108 is changed in the reception tuning circuit 103, the capacitance of the variable capacitance element 105 changes, so that the electrical length of the reception element 102 changes. As a result, when the power appearing in the wave receiving element 102 is extracted by the receiving circuit 104 and used as a received signal, the frequency of the received signal changes, so that the frequency of the received broadcast radio wave can be changed.

Japanese Patent No. 3307248 JP 2003-298341 A JP 2000-151448 A JP 2006-345042 A JP 2006-61455 A JP 2004-260428 A JP 2004-236171 A Japanese Patent Laid-Open No. 11-27160

  In a conventional tuning antenna 101, a receiving tuning circuit 103 including a variable capacitance element 105 is connected to one end of a receiving element 102 formed on a substrate. In this configuration, electrical noise generated inside the device is likely to be mixed into the wave receiving element 102 via the substrate housed in the same device housing and the wave receiving tuning circuit 103. For this reason, electrical noise generated inside the device is superimposed on the external signal received by the wave receiving element 102 in the reception signal output from the receiving circuit 104. Such electrical noise generated inside the mobile terminal device is called substrate noise.

  The place where the substrate noise occurs is any electronic circuit inside the device. For example, a CPU (Central Processing Unit) circuit, a memory circuit, a liquid crystal display driving circuit, an image sensor driving circuit, an infrared communication circuit, a telephone band transmission / reception circuit, a voice amplification circuit, a mechanical vibration circuit, a keyboard circuit, an external semiconductor memory interface circuit, A wired communication interface circuit, a television image reproduction circuit, a power supply stabilization circuit, and the like.

  When the gain of the receiving circuit 104 is increased in order to improve the reception sensitivity with respect to external radio waves, the conventional tuned antenna 101 also increases the substrate noise, and the substrate noise included in the received signal output from the receiving circuit 104 is increased. Becomes larger. As a result, there is a problem that reception sensitivity is not improved.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a tuned antenna that solves the above-described problems and reduces substrate noise to improve reception sensitivity.

  In order to achieve the above object, the present invention provides a receiving element for receiving a radio wave formed on a substrate, and an electrical length of the receiving element connected to one end of the receiving element in accordance with the frequency of the radio wave. A transmission line for transmitting electrical noise formed on the ground, in a tuning antenna including a reception tuning circuit for adjusting the power and a reception circuit for extracting power appearing in the reception element as a reception signal; A power combining circuit that combines the power appearing on the transmission line and the power appearing on the receiving element to output a true received signal obtained by removing the electrical noise from the received signal to the receiving circuit; Is.

  A noise tuning circuit may be provided that is connected to one end of the transmission line and adjusts the electrical length of the transmission line according to the frequency of the radio wave.

  You may provide the phase shifter which adjusts the phase of the electric power which appears in the said transmission line, and outputs it to the said electric power synthesis circuit.

  The present invention exhibits the following excellent effects.

  (1) Receiving sensitivity can be improved by reducing substrate noise.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, a tunable antenna 1 according to the present invention includes a wave receiving element 4 made of a conductor 3 (see FIG. 2) formed on a substrate 2 (see FIG. 2) and receiving external radio waves. A receiving tuning circuit 5 connected to one end of the receiving element 4 for adjusting the electrical length of the receiving element 4 in accordance with the radio wave, and a receiving circuit 6 for extracting the power appearing in the receiving element 4 as a received signal. In the tuned antenna 1 provided, a transmission line 8 composed of a conductor 7 (see FIG. 2) formed on the substrate 2 and transmits electrical noise, power appearing in the transmission line 8 and power appearing in the receiving element 4 And a power combining circuit 9 composed of a differential amplifier that outputs the signal to the receiving circuit 6.

  The configuration of the receiving element 4, the configuration of the receiving tuning circuit 5, and the configuration of the receiving circuit 6 are the same as those of the conventional tuning antenna 101. That is, the wave receiving element 4 is formed by providing the conductor 3 with a predetermined length, and the end opposite to one end to which the wave receiving tuning circuit 5 is connected is branched into two branches. Section 20) is grounded to the ground 19, and the other branch end (received signal output terminal 21) is connected to the power combining circuit 9. A variable capacitance element 10 is used in the wave receiving tuning circuit 5, and the variable capacitance element 10 and the DC blocking capacitor 11 are inserted in series between one end of the wave receiving element 4 and the ground 19. The control voltage from the frequency control voltage source 13 is applied to the connection point of the DC blocking capacitor 11 via the high frequency blocking resistor 12. The receiving circuit 6 is composed of an amplifier, and the output of the power combining circuit 9 is connected to the input of the receiving circuit 6.

  In the present invention, a variable capacitance diode may be used as the DC blocking capacitor 11. When the DC blocking capacitor 11 is a variable capacitance diode, the variable width of the DC blocking capacitor 11 can be increased by adding the variable width of the DC blocking capacitor 11 to the variable width of the capacitance of the variable capacitor 10. The adjustment range of the electrical length of the element 4 is widened.

  Similar to the wave receiving element 4, the transmission line 8 is formed by providing a conductor 7 with a predetermined length. However, the transmission line 8 is not branched.

  The power combining circuit 9 is composed of a differential amplifier. A signal from the opposite end of the transmission line 8 and a signal from the end of the branch on the opposite end side of the wave receiving element 4 are input to the two inputs of the differential amplifier.

  In the present embodiment, the tuning antenna 1 includes a noise tuning circuit 14 that is connected to one end of the transmission line 8 and adjusts the electrical length of the transmission line 8 according to the frequency of the radio wave received by the wave receiving element 4. The noise tuning circuit 14 is configured by using the variable capacitance element 15 similarly to the reception tuning circuit 5. A control voltage from the frequency control voltage source 13 is applied to a connection point between one end of the transmission line 8 and the variable capacitance element 15 via a high frequency cutoff resistor 16. As described above, the variable capacitance element 15 of the noise tuning circuit 14 is controlled by the same frequency control voltage source 13 as that of the variable capacitance element 10 of the reception tuning circuit 5. That is, when the electrical length of the wave receiving element 4 is adjusted, the electrical length of the transmission line 8 can be adjusted in conjunction with this. A method for determining the capacitance values of the variable capacitance elements 10 and 15 will be described later.

  The transmission line 8 and the noise tuning circuit 14 constitute a substrate noise detection circuit 17 indicated by a broken line. The substrate noise detection circuit 17 is formed on the ground 19 through an insulating film, and one end of the variable capacitance element 15 and the ground 19 are electrically connected. As described above, since the substrate noise detection circuit 17 is formed near the ground, it can receive only electric noise generated inside the device without receiving radio waves flying from the outside.

  In the present embodiment, the tuned antenna 1 includes a phase shifter 18 that adjusts the phase of the power appearing in the transmission line 8 and outputs it to the power combining circuit 9. That is, the opposite end of the transmission line 8 is connected to the input of the phase shifter 18, and the output of the phase shifter 18 is connected to one input of the power combining circuit 9. The phase shifter 18 may be composed of a variable capacitance diode, particularly a MEMS variable capacitance. This is because phase adjustment is possible even with a variable capacitance diode, so that the configuration of the phase shifter is simple, and in particular, the MEMS variable capacitance has low loss.

  As shown in FIG. 2, the substrate 2 on which the tuning antenna 1 according to the present invention is mounted is a substrate using only one dielectric (insulator) substrate material or a laminate of two or more. Conductors can be provided on both the front and back sides of the substrate 2 or between each substrate material. In the figure, a conductor 3 including a portion to be a wave receiving element 4, a conductor 7 including a portion to be a transmission line 8, and other conductors (hatched portions) are shown. In this figure, which surface of the substrate 2 each conductor is formed is ignored.

  The variable capacitor 10, the DC blocking capacitor 11, the high frequency blocking resistor 12, the variable capacitor 15, and the high frequency blocking resistor 16 are surface mount components. A circuit shown in the circuit diagram of FIG. 1 is realized on the substrate 2 by mounting these surface mount components between the conductors.

  The wave receiving element 4 is connected to the ground 19 through a narrow portion 20 made of a conductor at the upper right end of the ground 19 that is a conductor occupying a large area of the substrate 2 and is separated from the ground 19 by a predetermined distance. It extends parallel to the ground 19. The reception signal output end 21 of the reception element 4 extends toward the ground 19 from a position spaced apart from the narrow portion 20 by a predetermined distance. The received signal output terminal 21 and the power combining circuit 9 are connected by another conductor 23. The conductor 23 is formed on the ground 19 via an insulating film.

  The transmission line 8 made of the conductor 7 is connected to the power combining circuit 9 and is provided along the ground 19 via an insulating film (not shown). This is to prevent electromagnetic waves (broadcast radio waves to be received) coming from outside the equipment that accommodates the substrate 2 from generating a voltage in the transmission line 8. If it is desired to detect an external electromagnetic wave, the transmission line 8 is provided at a location distant from the ground 19 like the wave receiving element 4. Since the purpose is to detect noise (substrate noise), the transmission line 8 is provided near the ground 19 (on the ground 19) so that no external electromagnetic wave is detected.

  The transmission line 8 extends to the vicinity of the reception signal output end 21 of the reception element 4. This is because it is desired to transmit the substrate noise to the vicinity of the reception signal output terminal 21 of the reception element 4.

  Specifically, the variable capacitance diode (variable capacitance element) 10, the DC cut capacitor (DC blocking capacitor) 11, and the variable capacitance diode 15 are arranged so as to be aligned substantially in a straight line. Since the wave receiving element 4 is grounded to the substrate via the DC cut capacitor 11 and the variable capacitance diode 10, the substrate noise is likely to be mixed from the place 22 where the wave receiving tuning circuit 5 is grounded. In order to take out the substrate noise picked up by the reception tuning circuit 5, the variable capacitance diode 15 of the noise tuning circuit 14 is also arranged in the vicinity of the place 22 where the reception tuning circuit 5 is grounded. Thereby, the substrate noise (intensity and phase) picked up by the reception tuning circuit 5 and the substrate noise (intensity and phase) picked up by the noise tuning circuit 14 can be matched.

  Here, a method for determining the capacitance value of the variable capacitance element 10 used in the wave receiving tuning circuit 5, the capacitance value of the variable capacitance element 15 used in the noise tuning circuit 14, and the capacitance value of the variable capacitance diode used as the phase shifter 18. Will be described.

  First, the capacitance value C11 of the variable capacitance element 10 is determined by the same method as that of a normal antenna so as to resonate at a desired reception frequency f1. Similarly, the capacitance value C21 of the variable capacitance element 15 used in the noise tuning circuit 14 is also determined by the same method as that of a normal antenna so as to resonate at the same frequency f1. Next, the antenna circuit shown in FIG. 1 is configured using these capacitance values C11 and C21. Then, the reception signal output when the reception tuning circuit 5 and the noise tuning circuit 14 resonate at the reception frequency f1 is taken out from the power combining circuit 9, and the relationship between the frequency and the power as shown in FIG. 4 is measured. To do. While observing the measurement result, the capacitance value of the variable capacitance diode used as the phase shifter 18 is appropriately adjusted, and the capacitance value C31 of the variable capacitance diode used as the phase shifter 18 so that the peak of the received signal becomes sharp. Decide. By repeating this, the relationship between the desired reception frequency fn and the capacitance values C1n, C2n, C3n of the capacitive elements is determined, and the applied voltage Vn of the frequency control voltage source 13 is obtained so that each capacitance value is obtained. The resistance values of the high-frequency cutoff resistors 12 and 16 are also determined in advance. Finally, the relation between the desired reception frequency fn and the capacitance values C1n, C2n, and C3n of the capacitance element is stored in advance in a microcomputer or the like of the device on which the antenna is mounted, and frequency control is performed according to the reception frequency of the device. The applied voltage of the voltage source 13 is changed, and the capacitance value of each capacitive element is changed to function as an antenna.

  The operation of the tuning antenna 1 according to the present invention will be described.

  In the wave receiving element 4, the capacitance of the variable capacitance element 10 in the wave receiving tuning circuit 5 is changed by the control voltage from the frequency control voltage source 13. As a result, the electrical length of the wave receiving element 4 to which the variable capacitance element 10 is connected at one end changes. An external radio wave having a frequency corresponding to the electrical length is received. The received signal is input from the received signal output terminal 21 to a differential amplifier as the power combining circuit 9.

  Inside the device, electrical noise is generated from the electronic circuit, and this is superimposed on the external radio wave received by the wave receiving element 4 as substrate noise.

  However, in the present invention, as described above, since the substrate noise detection circuit 17 is formed on the ground 19 through the insulating film, it does not receive radio waves flying from the outside, and electrical noise generated inside the device. The substrate noise transmitted from the transmission line 8 is input to the differential amplifier as the power combining circuit 9 from the vicinity of the reception signal output end 21 of the reception element 4 through the phase shifter 18. . At this time, the capacitance of the variable capacitance element 15 in the noise tuning circuit 14 is changed by the control voltage from the frequency control voltage source 13. Thereby, the electrical length of the transmission line 8 to which the variable capacitance element 15 is connected to one end changes. Substrate noise having a frequency corresponding to the electrical length (the same frequency as the external radio wave received by the reception tuning circuit 5) is transmitted.

  Since the phase shifter 18 adjusts the phase of the power of the substrate noise that appears on the transmission line 8, it is possible to adjust the degree of combination of the two powers in the power combining circuit 9 (the amount that the substrate noise is canceled).

  4A is a relationship diagram between the frequency and power of the signal received by the wave receiving element 4 before noise removal, and FIG. 4B is the relationship between the frequency and power of the signal output from the substrate noise output circuit. FIG. 4 (c) shows an external radio wave (true received wave) in which the signal shown in FIG. 4 (a) and the signal shown in FIG. Signal).

  In the power combiner circuit 9, the received signal from the wave receiving element 4 that is the two input powers and the substrate noise that is received by the substrate noise detection circuit 17 and then phase-adjusted by the phase shifter 18 are combined. The The received signal from the receiving element 4 has substrate noise superimposed on the external radio wave, but the synthesized signal is a received signal of only the external radio wave (received signal that is originally desired to be received; true received wave) Signal).

  In the receiving circuit 6, a received signal of only external radio waves is input, and substrate noise is removed. When the gain of the receiving circuit 6 is increased, the received signal of only the external radio wave is greatly amplified. Therefore, the reception sensitivity with respect to the external radio wave is improved. The output of the receiving circuit 6 is input to a tuner (not shown).

  Since the tuning antenna 1 according to the present invention has improved reception sensitivity, the sensitivity equivalent to the conventional one can be obtained even if the tuning antenna 1 is made smaller than the conventional one. Therefore, the tuning antenna 1 can be miniaturized. .

  In addition, the conventional tuning antenna 101 could not be placed in a place where it is susceptible to electrical noise from the inside of the device. However, the tuning antenna 1 according to the present invention can also be placed in a location where electrical noise is likely to be received from inside the device. Can be arranged. Thereby, since the freedom degree of arrangement | positioning increases, the restriction which comes from antenna arrangement | positioning in an apparatus design is eliminated, and a design becomes easy.

  As described above, the tuning antenna 1 according to the present invention includes the substrate noise detection circuit 17 including the transmission line 8 and the noise tuning circuit 14 in addition to the wave receiving element 4 and the wave receiving tuning circuit 5 having the same structure as the conventional one. The board noise is detected and the power combining circuit 9 is provided to synthesize the detected board noise and the received signal, so that the board noise superimposed on the external radio wave is canceled out. Can do.

  In the tuning antenna 1 according to the present invention, since the noise tuning circuit 14 and the phase shifter 18 are connected to the substrate noise detection circuit 17, the tuning antenna 1 is interlocked with the tuning operation in the wave receiving element 4 and the wave receiving tuning circuit 5. By adjusting the noise tuning circuit 14 and the phase shifter 18, the tuning antenna 1 can be adjusted so as to have an optimum reception sensitivity.

  The tunable antenna 1 according to the present invention can be used as a built-in antenna for receiving terrestrial digital broadcasts in portable terminals, a built-in antenna for receiving terrestrial digital broadcasts in notebook computers, and other tunable receiving antennas. In addition, when the MEMS variable capacitor is used, since the power can be increased, it can also be used for a transmission / reception antenna.

It is a circuit diagram of a tuning antenna showing an embodiment of the present invention. It is a substance wiring diagram of the tuning antenna of FIG. It is a circuit diagram of the conventional tuning antenna. (A)-(c) is a frequency versus power characteristic figure of the signal in each part of the tuning type antenna of the present invention.

Explanation of symbols

1 Tunable Antenna 2 Substrate 3 Conductor 4 Receiving Element (Inverted F Antenna)
DESCRIPTION OF SYMBOLS 5 Reception tuning circuit 6 Reception circuit 7 Conductor 8 Transmission line 9 Power synthesis circuit 13 Frequency control voltage source 14 Noise tuning circuit 17 Substrate noise detection circuit 18 Phase shifter

Claims (3)

A receiving element for receiving a radio wave formed on the substrate; a receiving tuning circuit connected to one end of the receiving element for adjusting the electrical length of the receiving element in accordance with the frequency of the radio wave; In a tunable antenna including a receiving circuit that extracts power appearing in a wave element as a received signal,
A transmission line formed on the ground for transmitting electrical noise, the power appearing on the transmission line and the power appearing on the receiving element are combined to remove the electrical noise from the received signal. A tuning antenna comprising: a power combining circuit that outputs a wave signal to the receiving circuit.   The tuned antenna according to claim 1, further comprising a noise tuning circuit connected to one end of the transmission line and adjusting an electrical length of the transmission line in accordance with a frequency of the radio wave.   The tuned antenna according to claim 1, further comprising a phase shifter that adjusts a phase of electric power appearing on the transmission line and outputs the phase-adjusted electric power to the power combining circuit.

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