WO2006054576A1

WO2006054576A1 - Vhf band receiver

Info

Publication number: WO2006054576A1
Application number: PCT/JP2005/021006
Authority: WO
Inventors: Hiroshi Miyagi
Original assignee: Niigata Seimitsu Co., Ltd.
Priority date: 2004-11-18
Filing date: 2005-11-16
Publication date: 2006-05-26

Abstract

A VHF band receiver capable of providing a high flexibility of mounting an antenna, facilitating the reduction in size and improving the sensitivity. An FM receiver (100) comprises a tuner circuit for selectively passing signals, which have a tuning frequency and frequencies close thereto, of received signals; a local oscillator circuit (13) for generating a local oscillation signal; and a mixer circuit (12) for frequency mixing the local oscillation signal generated by the local oscillator circuit (13) with the high-frequency signals obtained by the tuning operation of the tuner circuit. The tuner circuit includes two antenna coils (1,9) wound around respective separate magnetic cores and is set to tuning frequencies of VHF band.

Description

Specification

VHF receiver

Technical field

The present invention relates to a VHF band receiver that receives a VHF band signal.

Background art

Conventionally, in a receiver that receives a VHF band signal such as an FM broadcast, a linear antenna using a rod antenna, a earphone cord, or the like has been used. However, this type of antenna needs to be exposed outside the receiver's housing, which can be easily damaged. As a conventional technique for avoiding such inconvenience, a receiver using a helical 'loop type surface field radiation antenna in which a metal conductor is spirally wound around a core made of a rectangular frame type conductive material is known (for example, , See Patent Document 1.) o By using this antenna, the entire receiver including the antenna can be made smaller than a rod antenna or a linear antenna.

Patent Document 1: Japanese Patent Laid-Open No. 9-93027 (Page 3-6, Fig. 1-11)

Disclosure of the invention

Problems to be solved by the invention

By the way, the helical 'loop type surface field radiation antenna disclosed in Patent Document 1 described above is smaller than a rod antenna or the like, but for example, a reception built in a portable device such as a cellular phone. When used in a machine, it was necessary to secure a relatively large occupied space, and there was a problem that miniaturization was insufficient. In addition, the directivity of the antenna is stronger than that of a rod antenna or the like, and there is a problem that the reception sensitivity is lowered depending on the installation position of the receiver.

[0004] The present invention was created in view of the above points, and the purpose of the present invention is a VHF band in which the degree of freedom of antenna installation is high, miniaturization is easy, and reception sensitivity can be improved. It is to provide a receiver.

Means for solving the problem

[0005] In order to solve the above-described problems, the VHF band receiver of the present invention And a tuning circuit that selectively passes a tuning frequency and a signal in the vicinity thereof, a local oscillation circuit that generates a local oscillation signal, a local oscillation signal generated by using the local oscillation circuit, and a tuning operation by the tuning circuit. The tuning circuit has a plurality of antenna coils wound around different magnetic cores, and a tuning frequency of the VHF band is set. In this way, a small antenna can be realized by using an antenna composed of a magnetic core and an antenna coil, so that the degree of freedom of antenna installation is increased and the entire VHF band receiver can be easily downsized. . For example, when an antenna having an impedance of 300 Ω for FM broadcast wave reception is realized, a magnetic core having a length of about 1 cm can be used, so that a conventional rod antenna, linear antenna, helical loop type Compared to surface field radiation antennas, it can be significantly reduced in size. In addition, by providing a plurality of such small antennas, it is possible to improve reception sensitivity by diversity reception.

[0006] Further, a selection unit that selects one of the plurality of antenna coils, a reception state detection unit that detects a reception state when the antenna coil selected by the selection unit is used, and a reception state Switching control means for switching the antenna coil selected by the selection means based on the reception state detected by the detection means. By switching antennas based on the reception status, it is possible to receive signals in a better reception status.

[0007] Further, the switching control means described above is configured so that when the reception information corresponding to the antenna coil before switching is better than the reception state corresponding to the antenna coil after switching, the antenna before switching It is desirable to instruct the selection means to return to the coil. As a result, it is possible to reliably select an antenna having a good reception state and perform signal reception.

[0008] In addition, a selection unit that selects one of a plurality of reception systems corresponding to each of the plurality of antenna coils, and a reception state detection unit that detects a reception state corresponding to each of the plurality of reception systems. And a switching control means for switching the reception system selected by the selection means based on the reception status detected by the reception status detection means. As a result, the reception status in each of a plurality of reception systems Can be detected in parallel, and good reception sensitivity can always be achieved using an appropriate reception system.

[0009] Further, it is desirable that the plurality of antenna coils described above are arranged at positions separated from each other by a predetermined distance. As a result, it is possible to improve the reception state by improving the relationship between the antenna position and the phase of the received signal.

[0010] Further, it is desirable that the distance between the plurality of antenna coils described above is a quarter wavelength of the carrier frequency included in the reception frequency band. As a result, signal reception using at least some of the antennas can be performed, and the reception sensitivity can be prevented from being extremely deteriorated.

[0011] Further, it is desirable that the plurality of antenna coils described above are arranged in different directions. This makes it possible to receive signals using other antennas even when one antenna is arranged in the direction that is most insensitive to received radio waves. Regardless of this, the reception sensitivity can be improved.

[0012] Further, the above-described tuning circuit forms a resonance circuit together with the antenna coil, has a variable capacitance circuit whose capacitance can be changed, and performs a setting operation for matching the tuning frequency to the frequency of the signal to be received. It is desirable to further include frequency setting control means for performing. As a result, a signal in the vicinity of the frequency of the signal desired to be received can be selectively passed by the tuning circuit. Therefore, when a fixed tuning frequency is set as in the case of using a conventional rod antenna or the like. In comparison, sensitivity and selectivity can be improved.

[0013] In addition, the local oscillation circuit described above can change the oscillation frequency, and the frequency setting control means preferably performs control to change the oscillation frequency of the local oscillation circuit in conjunction with the tuning frequency of the tuning circuit. . In this way, by linking the tuning frequency of the tuning circuit and the oscillation frequency of the local oscillation circuit, it becomes possible to realize a super heterodyne FM receiver with further improved sensitivity and selectivity. For example, the tuning frequency of the tuning circuit and the oscillation frequency of the local oscillation circuit are changed while maintaining a frequency difference corresponding to the intermediate frequency.

[0014] Further, the variable capacitance circuit described above has a plurality of capacitors that are selectively connected to the respective antenna coils, and the frequency setting control means determines a connection state of the plurality of capacitors. It is desirable to change the tuning frequency of the VHF band determined by the antenna coil and the capacitor that is selectively connected to this antenna coil. By switching the capacitor connected to the antenna coil, it is possible to selectively pass signals in the vicinity of the frequency of the signal desired to be received. Therefore, a fixed rod like a conventional rod antenna is used. Sensitivity and selectivity can be improved compared to when the tuning frequency is set!

[0015] In addition, a switch for intermittent connection is connected in series to at least some of the plurality of capacitors described above, and the frequency setting control means changes the intermittent state of the switch by changing the intermittent state of the switch. It is desirable to change the selection state. This makes it possible to easily switch the connection state of the capacitor.

[0016] Further, it is desirable that a plurality of series circuits each having one switch connected in series to the one capacitor described above are provided, and the plurality of series circuits are connected in parallel to the antenna coil. As a result, it is possible to switch the capacitor connected in parallel with the antenna coil, and the resonance frequency of the parallel resonance circuit, ie, the tuning frequency of the tuning circuit can be easily changed.

[0017] The variable capacitance circuit described above is preferably formed on a semiconductor substrate on which frequency setting control means is formed. As a result, almost all components except the antenna coil and speaker can be integrally formed on the semiconductor substrate, and the entire VHF band receiver can be reduced in size and cost. In addition, by forming the frequency setting control means on the same semiconductor substrate as the plurality of capacitors and the plurality of switches, the switching control of the switches by the frequency setting control means becomes easy and the number of external parts can be reduced. . Furthermore, the variation in the relative ratio of the plurality of capacitors can be reduced.

[0018] Further, it is desirable that the above-described antenna coil has one end grounded and the other end connected to the variable capacitance circuit. Since only one end of the antenna coil needs to be directly connected to the variable capacitance circuit, wiring can be simplified. In particular, when a variable capacitance circuit is formed on a semiconductor substrate, the number of dedicated pads used to directly connect the antenna coil and the variable capacitance circuit is the same as the number of antenna coils. The number of pads can be reduced. [0019] Further, it is desirable that the above-described antenna coil has a grounded center tap, and each of both ends is connected to both ends of the variable capacitance circuit. Alternatively, in the variable capacitance circuit described above, two capacitors having capacitance values set to approximately the same are connected in series, the connection point of the two capacitors is grounded, and both ends of the variable capacitance circuit are connected to the antenna coil. It is desirable to be directly connected to both ends. As a result, it is possible to increase the amplitude of the signal output from the tuning circuit constituted by the antenna coil and the variable capacitance circuit, and the sensitivity and selectivity can be improved.

Brief Description of Drawings

FIG. 1 is a diagram illustrating a configuration of an FM receiver according to an embodiment.

FIG. 2 is a diagram showing an arrangement example of two antenna coils.

FIG. 3 is a diagram showing an arrangement example of two antenna coils.

FIG. 4 is a flowchart showing an operation procedure for switching a switch by a control unit.

FIG. 5 is a view showing a modification of the FM receiver having two systems up to the detection circuit.

FIG. 6 is a flowchart showing an operation procedure for switching a switch by a control unit.

FIG. 7 is a diagram showing a partial configuration of an FM receiver using a balanced antenna coil.

FIG. 8 is a diagram showing a partial configuration of a modification of the FM receiver.

FIG. 9 is a diagram showing a partial configuration of a modification of the FM receiver.

FIG. 10 is a diagram showing an arrangement example of three antennas.

Explanation of symbols

[0021] 1, 9 antenna coinore

2 Variable capacitance circuit

3, 4 pads

5, 6 switches

7 Inverter circuit

10 1 chip parts

11 High frequency amplifier circuit

12 Mixing circuit 13 Local oscillator circuit

14, 16 Intermediate frequency filter

15 Intermediate frequency amplifier

18 FM detector circuit

19 Stereo demodulation circuit

20 Control unit

21 Detection circuit

22 Selection circuit

40 Operation unit

42 Display

100 FM receiver

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an FM receiver according to an embodiment to which the present invention is applied will be described in detail. FIG. 1 is a diagram illustrating a configuration of an FM receiver according to an embodiment. FM receiver 100 shown in FIG. 1 includes antenna coils 1 and 9, variable capacitance circuit 2, switches 5 and 6, inverter circuit 7, high-frequency amplifier circuit 11, mixing circuit 12, local oscillation circuit 13, intermediate frequency filter 14, 16, an intermediate frequency amplifier circuit 15, an FM detection circuit 18, a stereo demodulation circuit 19, a control unit 20, a detection circuit 21, and a selection circuit 22. These components are formed as a one-chip component 10 on a semiconductor substrate using each component force SCMOS process except the antenna coils 1 and 9. 1 The chip component 10 and the antenna coils 1 and 9 are connected via pads 3 and 4 formed on the semiconductor substrate.

Each of the antenna coils 1 and 9 is wound around a ferrite-based magnetic core. For example, a ferrite magnetic core having a diameter of 2 to 3 mm and a length of about 1 cm is used, and an antenna coil 1 having an impedance of about several kΩ is formed by winding a conducting wire around the core. .

FIG. 2 and FIG. 3 are diagrams showing an arrangement example of two antenna coils 1 and 9. As shown in FIG. 2, the antenna coils 1 and 9 are arranged in the same direction and spatially at a predetermined distance (for example, λ Ζ4 when the wavelength of the carrier frequency of the received signal is estimated), or Shown in 3 In such a case, it may be arranged in different directions (for example, 90 °).

The switches 5 and 6 selectively connect one of the antenna coils 1 and 9 to the variable capacitance circuit 2. The connection is switched by a switching signal input from the control unit 20. One switch 5 is inputted via a switching signal force inverter circuit 7 and the other switch 6 is inputted a switching signal directly. When a low-level switching signal is output from the control unit 20, this signal is inverted by the inverter circuit 7 and input to the switch 5, and the switch 5 is closed (ON). At this time, the switch 6 is opened (turned off) by receiving a low-level control signal. Therefore, the variable capacitance circuit 2 is connected only to the antenna coil 1. On the contrary, when a high-level switching signal is output from the control unit 20, this signal is inverted by the inverter circuit 7 and input to the switch 5, and the switch 5 is opened. At this time, the switch 5 is closed by inputting a high-level control signal. Therefore, the variable capacitance circuit 2 is connected only to the antenna coil 9.

The variable capacitance circuit 2 is a capacitive circuit, and includes a plurality of capacitors 31 and a plurality of switches 32. A variable capacitance circuit 2 is configured by including a plurality of series circuits of one capacitor 31 and one switch 32, and each of the plurality of series circuits is connected in parallel to one of the antenna coils 1 and 9. The Each switch 32 can set an intermittent state independently of each other, and a capacitor 31 connected to the closed switch 32 is selectively connected to one of the antenna coils 1 and 9. The For example, the switch 32 is realized by using an analog switch in which the source and drain of the p-channel FET and the n-channel FET are connected in parallel.

[0027] As described above, the antenna coil 1 or 9 and the variable capacitance circuit 2 are connected in parallel to form an LC resonance circuit, and a tuning frequency corresponding to the resonance frequency of the resonance circuit and a broadcast wave in the vicinity thereof are formed. The antenna coil 1 or 9 and the variable capacitance circuit 2 operate as a tuning circuit that selectively passes.

The high frequency amplifier circuit 11 performs high frequency amplification on the signal output from the variable capacitance circuit 2. The local oscillation circuit 13 generates a local oscillation signal shifted by an intermediate frequency with respect to the frequency of the broadcast wave desired to be received.

[0029] The control unit 20 controls the overall operation of the FM receiver 100, and is controlled by the local oscillation circuit 13. By selecting the frequency of the local oscillation signal to be generated, the channel selection operation is performed to determine the broadcast wave to be received. Further, the control unit 20 outputs a switching signal for selectively turning on one of the switches 5 and 6 based on the detection result by the detection circuit 21. Detailed operations for switching between switches 5 and 6 will be described later. The control unit 20 includes a CPU and a memory, and performs a control operation by executing a predetermined program.

[0030] The detection circuit 21 is for detecting a reception state. For example, the detection is performed by paying attention to the electric field strength and the presence / absence of multipath as the reception state. In the present embodiment, the received electric field strength and the force that detects the presence / absence of multipath are detected as long as the reception sensitivity and noise level are changed when the antenna coils 1 and 9 are switched. The reception state may be detected. For example, it may be possible to detect the degree of error when demodulating multiplexed data included in FM multiplex broadcasting. In some cases, the amount of noise may be detected as the reception state. In addition, in the configuration shown in FIG. 1, which configuration and the detection circuit 21 should be connected depends on the characteristics of the force detection target in which the detection circuit 21 is connected after the intermediate frequency filter 16. Alternatively, the detection circuit 21 may be connected to each other, or the detection circuit 21 may be connected to a plurality of configurations.

The selection circuit 22 performs a predetermined decoding process on the setting data input from the control unit 20 to generate a switching signal that controls the intermittent state of each switch 32 in the variable capacitance circuit 2. If the number of switches 32 is m, the number of switching signals is also m. Each switching signal is set to a voltage level of either low level or high level. For example, when a switching signal having a low voltage level is input, the switch 32 is opened, and when a switching signal having a high voltage level is input, the switch 32 is closed. In addition, only one switching signal can be selectively set to the high level, and two or more switching signals can be selectively combined to be set to the high level.

[0032] The mixing circuit 12 mixes the signal output from the high-frequency amplifier circuit 11 and the local oscillation signal output from the local oscillation circuit 13, and outputs a signal corresponding to the difference (or sum) component. . The intermediate frequency filters 14 and 16 are provided before and after the intermediate frequency amplifier circuit 15 and extract only a predetermined band component of the input intermediate frequency signal force. The intermediate frequency amplifier circuit 15 converts some intermediate frequency signals that pass through the intermediate frequency filters 14 and 16. Amplify. The FM detection circuit 18 performs FM detection processing on a signal having a constant amplitude after being output from the intermediate frequency filter 16 at the subsequent stage and passing through a limit circuit (not shown). The stereo demodulation circuit 19 performs stereo demodulation processing on the composite signal after FM detection output from the FM detection circuit 18 to generate an L signal and an R signal.

[0033] The operation unit 40 is for performing channel selection operation, volume setting operation, and the like by a user, and includes various operation keys and operation knobs necessary for these operations. The display unit 42 is for notifying the user of various types of information, and displays the frequency of the broadcast wave being received, the name of the broadcast station corresponding to this broadcast wave, and the volume level, etc. .

The above-described switches 5 and 6 and the inverter circuit 7 correspond to selection means, the detection circuit 21 corresponds to reception state detection means, and the control unit 20 corresponds to switching control means and frequency setting control means, respectively.

[0035] The FM receiver 100 of the present embodiment has such a configuration. Next, an operation of switching the antenna coils 1 and 9 will be described. FIG. 4 is a flowchart showing an operation procedure for switching the switches 5 and 6 by the control unit 20. When the FM receiver 100 is turned on and a desired broadcast wave reception operation is started (step 100), the control unit 20 determines whether the electric field strength is below the reference value based on the detection result of the detection circuit 21. Is determined (step 101). If it is not less than the reference value, a negative determination is made, and the control unit 20 determines whether multipath has occurred based on the detection result of the detection circuit 21 (step 102). If no multipath has occurred, a negative determination is made, and the process returns to step 101 and the determination operation is repeated. If the electric field strength is a weak electric field that is less than or equal to the reference value, an affirmative determination is made in the determination of step 101. Alternatively, when multipath has occurred, an affirmative determination is made in the determination of step 102. If an affirmative determination is made in either step 101 or 102, the control unit 20 next stores the state (the electric field strength and the degree of multipath generation) at that time (step 103), and then the antenna. Is switched (step 104). For example, to switch to antenna coil 9 when antenna coil 1 is currently in use, control unit 20 switches the low-level switching signal output so far to the noise level and turns on switch 6. Turn off switch 5. Next, the control unit 20 determines whether or not the reception state after switching is better (step 105) If it is satisfactory, an affirmative determination is made, and a series of antenna switching operations are terminated. If the reception state after switching is worse, a negative determination is made in the determination of step 105, the antenna is returned to its original state (step 106), and the series of antenna switching operations ends. In the above-described example, the control unit 20 switches to the switch signal of “NO” and “Y” level, turns on the switch 5 and turns off the switch 6, and returns the connection to the antenna coil 1 side.

[0036] As described above, in the FM receiver 100 of the present embodiment, a small antenna can be realized by using the antenna composed of the magnetic core and the antenna coils 1 and 9, so that the antenna can be installed freely. The size of the FM receiver 100 as a whole can be easily reduced. For example, when realizing an antenna with an impedance of 300 Ω for FM broadcast wave reception, a magnetic core with a length of about 1 cm can be used, so a conventional rod antenna, linear antenna, helical loop Compared to a type field radiation antenna, the size can be greatly reduced. In addition, by providing a plurality of such small antennas, it is possible to improve reception sensitivity by diversity reception.

[0037] In particular, the control unit 20 gives an instruction to switch the antenna coils 1 and 9 using the switches 5 and 6 based on the reception state detected by the detection circuit 21, and the antenna switching is performed based on the reception state. By doing so, it becomes possible to receive signals in a better reception state. When the reception information corresponding to the antenna coil before switching is better than the reception state corresponding to the antenna coil after switching, the control unit 20 instructs to return to the antenna coil before switching. Signals can be received by reliably selecting antennas with good reception conditions.

[0038] Further, by arranging the two antenna coils 1 and 9 at positions separated from each other by a predetermined distance, it is possible to improve the reception state by improving the relationship between the antenna position and the phase of the received signal. Become. In particular, it is possible to receive signals using at least one antenna by setting the distance between the two antenna coils 1 and 9 to a length corresponding to a quarter wavelength of the carrier frequency included in the reception frequency band. Therefore, it is possible to prevent the reception sensitivity from becoming extremely bad.

[0039] In addition, by arranging the two antenna coils 1 and 9 in different directions, one antenna Even when the antenna is placed in the direction where the sensitivity is most deteriorated with respect to the received radio wave, it is possible to receive signals using other antennas, improving reception sensitivity regardless of the orientation of the receiver housing. Can be made.

[0040] Further, the control unit 20 performs a setting operation to make the tuning frequency coincide with the frequency of the broadcast wave to be received, so that a signal in the vicinity of the frequency of the broadcast wave desired to be received can be selectively passed. Therefore, compared to the case where a fixed tuning frequency is set as in the case where a conventional rod antenna or the like is used, sensitivity and selectivity can be improved over the entire FM frequency band. . Further, the control unit 20 performs control to change the oscillation frequency of the local oscillation circuit 13 in conjunction with the tuning frequency of the tuning circuit, and links the tuning frequency of the tuning circuit and the oscillation frequency of the local oscillation circuit 13. This makes it possible to realize a superheterodyne FM receiver 100 with further improved sensitivity and selectivity.

[0041] Since the variable capacitance circuit 2 and other circuits are formed on the semiconductor substrate on which the control unit 20 is formed, only the antenna coils 1 and 9 wound around the magnetic core are tuned as external components. The tuning circuit and the FM receiver 100 that can change the frequency can be configured, and the entire FM receiver 100 can be downsized. In addition, by forming the control unit 20 on the same semiconductor substrate as the plurality of capacitors 31 and the plurality of switches 32, switching control of the switch 32 by the control unit 20 becomes easy and the number of external parts is reduced. Can do. Further, variation in the relative ratio of the plurality of capacitors 31 can be reduced.

[0042] In addition, by using an unbalanced configuration in which one end of the antenna coils 1 and 9 is grounded and the other end is directly connected to the variable capacitance circuit 2, wiring can be simplified. In particular, when the variable capacitance circuit 2 is formed on a semiconductor substrate, only two dedicated nodes 3 and 4 can be used to directly connect the antenna coils 1 and 9 and the variable capacitance circuit 2. Therefore, the number of nodes on the semiconductor substrate can be reduced.

[0043] In addition, the variable capacitance circuit 2 includes a plurality of capacitors 31 and a plurality of switches 32, and the switching state of these switches 32 is switched by the control unit 20, thereby easily switching the connection state of the capacitors 31. Thus, the entire capacitance of the variable capacitance circuit 2 can be easily changed. By the way, in the above description, it is determined whether or not to switch the antenna coil by detecting the reception state when the reception operation is performed using one antenna coil. If there are two reception system configurations up to the reception status detection circuit, the reception status when antenna coils 1 and 9 are used can be detected in parallel. It is possible to determine which antenna coil will be used for good reception before performing.

[0045] FIG. 5 is a diagram illustrating a modification of the FM receiver including two systems of reception systems up to the detection circuit. In FIG. 5, the main differences from the FM receiver 100 shown in FIG. 1 are shown.

[0046] FM receiver 100A shown in FIG. 5 includes two circuits of each receiving system from variable capacitance circuit 2 to intermediate frequency filter 16 and detection circuit 21 included in FM receiver 100 shown in FIG. Yes. In FM receiver 100, switches 5 and 6 and inverter circuit 7 provided between variable capacitance circuit 2 and pads 3 and 4 are connected between intermediate frequency filter 16 and FM detection circuit 18 in FM receiver 100A. Is provided. Based on the detection result by the detection circuit 21, the control unit 20 outputs a switching signal for selectively turning on one of the switches 5 and 6. In the following explanation, one receiving system corresponding to pad 3 and switch 5 is referred to as A system, and the other receiving system corresponding to node 4 and switch 5 is referred to as B system.

FIG. 6 is a flowchart showing an operation procedure for switching the switches 5 and 6 by the control unit 20. The FM receiver 100A is turned on to start receiving a desired broadcast wave (step 200). This reception operation is performed using, for example, each circuit of system A with switch 5 turned on. Next, the control unit 20 detects the reception state (the electric field strength and the degree of multipath) for the A system (step 201), and detects the reception state for the B system (step 202). These reception status detection orders may be performed at the same time, whichever comes first. Next, the control unit 20 determines whether or not the reception state of the system A is better (step 203). If the system A is better, the control unit 20 makes an affirmative judgment and turns on the switch 5 to turn on the A The connection is switched to the system side (step 204). Note that if reception using the A-system circuit has been performed so far, switch 5 is already in the ON state, so the connection state of switch 5 is maintained. Also, when the reception status is better for system B In step 203, a negative determination is made, and then the control unit 20 turns on the switch 6 and switches the connection to the B system side (step 205). In this way, after switching to a circuit of a system with a good reception state, the process returns to step 201 and the processing after the detection operation of the reception state is repeated again.

[0048] As described above, by providing two reception systems, it becomes possible to detect the reception status in each reception system in parallel, and always achieve good reception sensitivity using an appropriate reception system. can do.

[0049] Further, in the above-described FM receivers 100 and 100A, a force balance type antenna coil using unbalanced antenna coils 1 and 9 with one end grounded may be used. Fig. 7 is a diagram showing a partial configuration of an FM receiver using a balanced antenna coil. The FM receiver shown in Fig. 7 includes a balanced antenna coil 1A, 9A, a variable capacitance circuit 2A that forms a tuning circuit in combination with one of these antenna coils 1A, 9A, and a differential circuit. And a high frequency amplifier circuit 11A constituted by an amplifier circuit. The other configurations are basically the same as those of the FM receiver 100 shown in FIG. 1, and the illustration and detailed description in FIG. 7 are omitted.

[0050] The antenna coil 1A is wound around a ferrite-based magnetic core, and a center position force center one tap is drawn out. This center tap is grounded. Both ends of the antenna coil 1A are connected to the variable capacitance circuit 2A via pads 3A and 3B and switches 5A and 5B formed on the semiconductor substrate. Similarly, the antenna coil 9A is wound around a ferrite-based magnetic core, and the center position force is also pulled out from the center tap. This center tap is grounded. Both ends of the antenna coil 9A are connected to the variable capacitance circuit 2A via pads 4A and 4B and switches 6A and 6B formed on the semiconductor substrate.

The variable capacitance circuit 2A has substantially the same configuration as the variable capacitance circuit 2 shown in FIG. 1, and includes a plurality of capacitors 31 and a plurality of switches 32. However, in the variable capacitance circuit 2, one end of the series circuit composed of the capacitor 31 and the switch 32 is grounded, but in the variable capacitance circuit 2A, both ends of the series circuit composed of the capacitor 31 and the switch 32 are connected to the pads 3A, 3B or The difference is that it is connected to either pad 4A or 4B and not grounded. [0052] By using the balanced antenna coil 1A (or 9A) in this way, the amplitudes on the opposite sides of the grounded center tap can be summed, so that the high frequency from the tuning circuit can be increased. The gain of the broadcast wave signal input to the amplifier circuit 11A can be increased by about 6 dB. The high-frequency amplifier circuit 11A differentially amplifies the broadcast wave signal output from the variable capacitance circuit 2A and inputs the amplified signal to the subsequent mixing circuit 12. By doing so, the dynamic range can be increased.

FIG. 8 is a diagram showing a partial configuration of a modification of the FM receiver. The FM receiver shown in Fig. 7 is a force that realizes a non-type configuration by providing center taps on the antenna coils 1A and 9A and grounding them. A similar balanced configuration can also be realized by providing a center tap and grounding.

[0054] The FM receiver shown in FIG. 8 includes antenna coils 1B and 9B, a variable capacitance circuit 2B that forms a tuning circuit in combination with one of these antenna coils 1B and 9B, and a differential amplifier circuit. And a high-frequency amplifier circuit 11A constituted by: The other configurations are the same as those of the FM receiver 100 shown in FIG. 1, and the illustration and detailed description in FIG. 8 are omitted.

The antenna coil 1B is wound around a flight-type magnetic core. Both ends of the antenna coil 1B are connected to the variable capacitance circuit 2B via pads 3A and 3B and switches 5A and 5B formed on the semiconductor substrate. Similarly, the antenna coil 9B is wound around a ferrite-based magnetic core. Both ends of the antenna coil 9B are connected to the variable capacitance circuit 2B via pads 4A and 4B and switches 6A and 6B formed on the semiconductor substrate.

The variable capacitance circuit 2B includes a plurality of capacitors 33 and a plurality of switches 34 in addition to the plurality of capacitors 31 and the plurality of switches 32. Multiple series circuits consisting of capacitor 31, switches 32, 34, and capacitor 33 are connected between pads 3A and 3B (or between pads 4A and 4B). In this series circuit, a center tap is provided at the connection point of the switches 32 and 34, and the center tap is grounded. Capacitors 31 and 33 as capacitive elements included in one series circuit are set to the same capacitance, and the two switches 32 and 34 connected to these capacitors 31 and 33 are the same. By controlling the timing intermittently, it is possible to output a broadcast wave signal with a large amplitude similar to the configuration shown in Fig. 7 from both ends of this series circuit.

Furthermore, the configuration shown in FIG. 7 and the configuration shown in FIG. 8 may be combined. That is, as shown in FIG. 9, the antenna coils 1A and 9A shown in FIG. 7 and the variable capacitance circuit 2B shown in FIG. 8 may be combined to form a balanced tuning circuit. In addition, the FM receiver using the balance type tuning circuit shown in FIGS. 7 to 9 has been described as having a configuration corresponding to the FM receiver 100 shown in FIG. An FM receiver having two circuits as shown in Fig. 5 may be provided with the balanced tuning circuit shown in Figs.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist of the present invention. For example, in the above-described embodiment, the FM receiver has been described. However, the present invention can be applied to a VHF receiver that receives other signals included in the VHF band. In this case, the demodulation method of the VHF receiver is not limited to the FM demodulation method, and an AM demodulation method or a digital demodulation method may be adopted.

In the above-described embodiment, the force described for switching two antennas according to the reception state may be switched between three or more antennas according to the reception state. FIG. 10 is a diagram illustrating an arrangement example of three antennas. As shown in Fig. 10, when using three (or more) antennas, each antenna can be arranged three-dimensionally so that it is not on the same plane. It is possible to receive the broadcast wave transmitted from the TV in good reception.

Industrial applicability

[0060] According to the present invention, a small antenna can be realized by using an antenna composed of a magnetic core and an antenna coil, so that the degree of freedom of antenna installation is increased and the entire V HF band receiver can be realized. Miniaturization becomes easy.

Claims

The scope of the claims

[1] A tuning circuit that selectively passes a tuning frequency and a signal in the vicinity thereof from a received signal, a local oscillation circuit that generates a local oscillation signal, and a local oscillation that is generated using the local oscillation circuit In a VHF band receiver having a mixing circuit for frequency-mixing a signal and a high-frequency signal obtained by a tuning operation by the tuning circuit,

The tuning circuit includes a plurality of antenna coils wound around different magnetic cores, and the tuning frequency of the VHF band is set.

[2] In claim 1,

Selecting means for selecting one of the plurality of antenna coils;

Receiving state detecting means for detecting a receiving state when using the antenna coil selected by the selecting means;

Switching control means for switching the antenna coil selected by the selection means based on the reception state detected by the reception state detection means;

Further equipped with a VHF receiver.

[3] In claim 2,

The switching control means returns to the antenna coil before switching when the reception information corresponding to the antenna coil before switching is better than the reception state corresponding to the antenna coil after switching. A VHF band receiver for instructing the selection means.

[4] In claim 1,

Selecting means for selecting one of a plurality of receiving systems corresponding to each of the plurality of antenna coils;

A reception state detecting means for detecting a reception state corresponding to each of the plurality of reception systems;

A switching control means for switching the reception system selected by the selection means based on the reception status detected by the reception status detection means;

Further equipped with a VHF receiver.

[5] In claim 1, The plurality of antenna coils are arranged at positions spaced apart from each other by a predetermined distance, and are a VHF band receiver.

[6] In claim 5,

The VHF band receiver in which the distance between the plurality of antenna coils is a quarter wavelength of the carrier frequency included in the reception frequency band.

[7] In claim 1,

The plurality of antenna coils are arranged in different directions from each other.

[8] In claim 1,

The tuning circuit constitutes a resonance circuit together with the antenna coil, and has a variable capacitance circuit whose capacitance can be changed.

A VHF band receiver further comprising frequency setting control means for performing a setting operation to match the tuning frequency with the frequency of a signal to be received.

[9] In claim 8,

The local oscillation circuit can change the oscillation frequency,

The frequency setting control means is a VHF band receiver that performs control to change the oscillation frequency of the local oscillation circuit in conjunction with the tuning frequency of the tuning circuit.

[10] In claim 8,

The variable capacitance circuit has a plurality of capacitors that are selectively connected to each of the antenna coils,

The frequency setting control means varies a tuning frequency of a VHF band determined by the antenna coil and the capacitor selectively connected to the antenna coil by changing a connection state of the plurality of capacitors. Band receiver.

[11] In claim 10,

A switch for intermittent connection is connected in series to at least some of the plurality of capacitors,

The frequency setting control means is a VHF band receiver that changes a selection state of the capacitor by changing an intermittent state of the switch.

[12] In claim 11,

A VHF band receiver in which a plurality of series circuits in which one switch is connected in series to one capacitor is provided, and the plurality of series circuits are connected in parallel to the antenna coil.

[13] In claim 8,

The variable capacitance circuit is a VHF band receiver formed on a semiconductor substrate on which the frequency setting control means is formed.

[14] In claim 8,

The antenna coil is a VHF band receiver in which one end is grounded and the other end is connected to the variable capacitance circuit.

[15] In claim 8,

The antenna coil has a grounded center tap, and both ends of the antenna coil are connected to both ends of the variable capacitance circuit.

[16] In claim 10,

In the variable capacitance circuit, two capacitors whose capacitance values are set to be substantially the same are connected in series,

A VHF band receiver in which a connection point of the two capacitors is grounded, and both ends of the variable capacitance circuit are directly connected to both ends of the antenna coil.