JP4627094B2 - Diversity receiver - Google Patents

Description

  The present invention relates to a diversity receiver that employs a phase diversity scheme.

  Conventionally, the diversity method was developed for the purpose of improving chopping noise and the like generated by the Doppler effect peculiar to mobile receivers. However, since it is also effective against multipath noise, in recent years, as a countermeasure against multipath, 1 Improvements are made by adopting diversity methods such as tuner diversity and two-tuner diversity. Basically, it is a system that selects antennas by detecting noise (multipath noise, etc.) coming to each antenna and sudden electric field fluctuations, but digital technology has been used in response to the digitization of tuners in recent years. A phase diversity method using an algorithm has been proposed (see, for example, Patent Document 1).

As an advantage of this phase diversity method,
(1) The maximum ratio of the phases input from the two antennas can be combined to improve noise such as multipath.
(2) Since the signals received by the two antennas are combined, the power is doubled and the weak electric field sensitivity can be improved.
Etc.
Japanese Patent Laid-Open No. 10-322255 (page 4-9, FIG. 1-19)

  By the way, a phase diversity receiver is effective as a countermeasure against multipath and chopping noise, but on the other hand, the capture ratio for the same frequency station is lowered and the desired broadcast wave cannot be received satisfactorily. was there. In other words, since the antenna of a broadcasting station is not installed for a mobile receiver, if the weak electric field sensitivity of the receiver is improved, the area in which broadcast waves of different contents can be received at the same frequency is expanded. In other words, the capture ratio decreases when a receiver is present in this area. In particular, when an FM receiver is considered, either one of two broadcast waves is selectively received. In the case of a mobile receiver, this selected state is relative to the antenna and the broadcast station. Depending on the position or the like, it may be frequently switched, which makes it very difficult to hear.

  The present invention was created in view of the above points, and an object of the present invention is to provide a diversity receiver that can receive a desired broadcast wave satisfactorily when a phase diversity method is used. is there.

In order to solve the above-described problem, the diversity receiver according to the present invention includes a plurality of tuner units to which different antennas are connected and a synthesizing unit that adjusts and combines the phases of output signals of at least one of the plurality of tuner units. And a demodulating means for demodulating the input signal and a signal output from the synthesizing means when the audio signal levels of the plurality of signals output from each of the plurality of tuner units are the same. Switching means that is set as a target of demodulation processing by the demodulation processing means and sets a signal output from any of the plurality of tuner units as a target of demodulation processing by the demodulation processing means when the audio signal levels of the plurality of signals are different And. When phase diversity reception is performed and the audio signal level of the signal received by each tuner unit is different, phase diversity reception is stopped and switching to single tuner reception using any one of the tuner units. It is possible to prevent different tuners from receiving different signals separately, and to receive only desired broadcast waves satisfactorily.

Further, it is desirable that the above-described combining means adjusts the phase so that the amplitude of the combined signal is maximized. As a result, when signals of the same audio signal level are received by the respective tuner units, it is possible to realize good reception sensitivity by combining these signals.

The signal processing apparatus further includes detection means for performing detection processing on signals output from each of the plurality of tuner units described above to detect audio signal levels corresponding to these signals, and the switching means is detected by the detection means. based on the audio signal level, it is desirable that the audio signal level of a plurality of signals outputted from each of the plurality of tuner units to determine whether the same. As a result, it is possible to determine the identity of a signal containing audio sound.

  In addition, it is preferable to further include multipath determination means for determining the presence or absence of multipath occurrence with a predetermined detection sensitivity and changing the detection sensitivity for determining the presence or absence of multipath generation according to the setting content by the switching means. In addition, it is desirable to increase the detection sensitivity when the switching unit sets the signal output from any of the plurality of tuner units described above as a target of demodulation processing by the demodulation processing unit. Further, the demodulation processing by the above-described demodulation processing means includes FM stereo demodulation processing, and when the multipath determination means determines that multipath has occurred, it sends an instruction to the demodulation processing means, It is desirable to reduce the channel separation of the signal obtained by the FM stereo demodulation process. Alternatively, the demodulation processing by the demodulation processing means described above includes FM stereo demodulation processing, and when the multipath determination means determines that multipath has occurred, it sends an instruction to the demodulation processing means, It is desirable that the signal obtained by the FM stereo demodulation process is monaural. Thereby, multipath detection sensitivity suitable for each of diversity reception and single tuner reception can be set, and an effective countermeasure against multipath can be realized.

  In addition, it is preferable to further include an adjacent interference determination unit that determines whether or not adjacent interference has occurred with a predetermined detection sensitivity, and changes detection sensitivity for determining whether or not adjacent interference has occurred according to the setting content of the switching unit. In addition, it is desirable to increase the detection sensitivity when the switching unit sets the signal output from any of the plurality of tuner units described above as a target of demodulation processing by the demodulation processing unit. Further, the apparatus further includes a band varying unit that varies a band of a signal to be demodulated by the above-described demodulation processing unit, and the adjacent disturbance determining unit determines whether the adjacent disturbance has occurred, It is desirable to send instructions to narrow the bandwidth. Accordingly, it is possible to set the adjacent interference detection sensitivity suitable for each of the diversity reception and the single tuner reception, and to realize an effective measure against the adjacent interference.

  Further, the apparatus further includes a strong electric field determining unit that determines whether or not the strong electric field state is present, and the switching unit is a signal output from the combining unit when the strong electric field determining unit determines that the strong electric field state is not present. Is set as the target of demodulation processing by the demodulation processing means, and when it is determined that the electric field is strong, the signal output from one of the plurality of tuner units is set as the target of demodulation processing by the demodulation processing means. It is desirable to do. Thus, it is possible to prevent the occurrence of intermodulation by stopping diversity reception and switching to single tuner reception in a strong electric field state where intermodulation is likely to occur.

  The tuner unit described above includes a tuning circuit that passes a frequency component in the vicinity of the tuning frequency among signals input through the antenna, and an automatic control that controls the gain of the signal input to the tuning circuit by varying the control voltage. It is preferable that the strong electric field determination means determines whether or not the strong electric field state is in accordance with the value of the control voltage. By monitoring the control voltage of the automatic gain control circuit that operates according to the electric field strength, it is possible to easily detect the strong electric field state.

  It is also desirable to reproduce the audio signal by receiving FM broadcast waves and performing FM demodulation and stereo demodulation by the demodulation processing means. When receiving FM broadcast waves, when there are a plurality of broadcast waves reaching the antenna, any one of the broadcast waves is selectively received and demodulated. Depending on the situation, the demodulated contents of the signals obtained by synthesizing the output signals of each tuner section may change frequently. In such a case, the diversity reception is stopped and the reception is performed by switching to the single tuner reception. It becomes possible to stabilize the state.

  Moreover, it is desirable to mount in the vehicle. In particular, when mounted on a vehicle, the direction of multiple antennas is frequently changed, so the broadcast wave that can be received best at each antenna is not constant, and the reception state tends to be unstable, Even in such a case, the reception state can be stabilized by stopping the diversity reception and switching to the single tuner reception.

  Hereinafter, a diversity receiver according to an embodiment to which the present invention is applied will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram illustrating a detailed configuration of the diversity receiver according to the first embodiment. The diversity receiver shown in FIG. 1 is mounted on a vehicle, and includes tuner units 10 and 20, analog-digital converters (ADC) 12 and 22, phase shifters 14 and 24, an adder 30, a phase control circuit 32, a band. A path filter (BPF) 40, detection circuits 42 and 60, a soft mute circuit 44, a noise canceller (NC) 46, a stereo demodulation circuit 48, a multipath detection circuit 62, an adjacent disturbance detection circuit 64, and a control unit 70 are configured. Yes. Among these components, each component other than the tuner units 10 and 20, the analog-digital converters 12 and 22, and the control unit 70 is realized by a digital signal processing device (DSP) 90.

  The tuner unit 10 is a front end unit (F / E) that receives a broadcast wave using the antenna 11 and converts it to an intermediate frequency signal by mixing the local oscillation signal. For example, the tuner unit 10 receives FM broadcast waves included in a predetermined broadcast band and converts them into an intermediate frequency signal of 10.7 MHz. The tuner unit 20 basically has the same configuration as that of the tuner unit 10, and receives FM broadcast waves included in a predetermined broadcast band via the antenna 21 and converts them into an intermediate frequency signal of 10.7 MHz. However, the antennas 11 and 21 corresponding to the tuner units 10 and 20 are installed at positions separated from each other and in different directions.

  The analog-digital converter 12 converts the analog intermediate frequency signal output from the one tuner unit 10 into a digital intermediate frequency signal. The phase shifter 14 shifts the phase with respect to the intermediate frequency signal output from the analog-digital converter 12. Similarly, the analog-digital converter 22 converts an analog intermediate frequency signal output from the other tuner unit 20 into a digital intermediate frequency signal. The phase shifter 24 shifts the phase with respect to the intermediate frequency signal output from the analog-digital converter 22.

  The adder 30 adds (synthesizes) the two types of intermediate frequency signals that have passed through the phase shifters 14 and 24. The phase control circuit 32 sets the phase shift amount of at least one of the phase shifters 14 and 24 so that the amplitude of the synthesized intermediate frequency signal output from the adder 30 is maximized. In the present embodiment, the two phase shifters 14 and 24 are provided. However, since these are used to adjust the relative phase difference between the two types of intermediate frequency signals, either one is used. If the phase difference can be adjusted, the other may be omitted.

  The bandpass filter 40 can change the passband width, and is used for band limitation of the input intermediate frequency signal. By narrowing the passband width of the bandpass filter 40 when adjacent interference occurs, it is possible to remove the broadcast wave that causes the adjacent interference. The detection circuit 42 performs FM detection processing on the intermediate frequency signal after passing through the bandpass filter 40 and outputs a stereo composite signal. The soft mute circuit 44 performs soft mute processing on the stereo composite signal as necessary. The noise canceller 46 removes a noise component included in the stereo composite signal. The stereo demodulation circuit 48 performs stereo demodulation processing on the stereo composite signal to separate the L signal and the R signal. Actually, a configuration (digital-analog converter, amplifier, or the like) for outputting these L and R signals from the speaker is connected to the subsequent stage of the stereo demodulation circuit 48, but these configurations are shown in FIG. It is omitted.

  The detection circuit 60 performs FM detection on the intermediate frequency signal output from the analog-digital converters 12 and 22, and extracts the audio signal level. This FM detection processing is performed in parallel for each of the two types of intermediate frequency signals output from the analog-digital converters 12 and 22.

  The multipath detection circuit 62 is for detecting a multipath based on the intermediate frequency signals output from the analog-digital converters 12 and 22. For example, as shown in FIG. 2, a bandpass filter (BPF) ) 62A and a peak detection circuit 62B. When multipath occurs, the 19 kHz pilot signal component included in the intermediate frequency signal is distorted, and the signal level around it increases. The band pass filter 62A extracts the peripheral frequency components (for example, frequency components of 15 to 18 kHz). The peak detection circuit 62B performs peak detection on the frequency component extracted by the bandpass filter 62A. Thereby, the peak value of the frequency component of 15-18 kHz is detected.

  The adjacent interference detection circuit 64 is for detecting adjacent interference based on the intermediate frequency signal output from the analog-digital converters 12 and 22, and for example, as shown in FIG. 3, a high-pass filter (HPF). 64A and a peak detection circuit 64B. Adjacent interference occurs when the frequency of the broadcast wave that you want to receive is close to the frequency of other broadcast waves, etc., and it varies depending on the country, but usually it is the frequency you want to receive. This occurs when there is a broadcast wave with a difference of 50, 100, 200 kHz. The high pass filter 64A extracts a frequency component of 50 kHz or higher corresponding to these broadcast waves. The peak detection circuit 64B performs peak detection on the frequency component extracted by the high pass filter 64A. As a result, peak values of frequency components such as 50, 100, and 200 kHz included when adjacent interference occurs are detected.

  The control unit 70 is for controlling the diversity receiver as a whole, and performs operations such as channel selection and volume adjustment corresponding to user operation instructions. In the present embodiment, when the same broadcast wave can be received via the two antennas 11 and 21, diversity reception using the two tuner units 10 and 20 is performed, and the two antennas 11 and 21 are respectively used. In the case of receiving separate broadcast waves, the broadcast wave is received using only one of these two tuner units 10 and 20, and in order to switch such a tuner unit, the control unit 70 , A diversity switching determination unit 72, a multipath determination unit 74, and an adjacent disturbance determination unit 76 are provided.

  The diversity switching determination unit 72 can compare the audio signal levels corresponding to the two types of intermediate frequency signals obtained by the detection processing by the detection circuit 60, and can receive the same broadcast wave via the two antennas 11 and 21. It is determined whether or not.

  Since the diversity receiver of this embodiment employs the diversity reception method, the reception sensitivity is improved. However, the arrangement of broadcast stations and frequency allocation are not set only for receivers with good reception sensitivity, but are set for single tuner receivers, which account for the majority. ing. FIG. 4 is a diagram showing an outline of the broadcast wave and the reception range. As shown in FIG. 4, a range in which a broadcast wave transmitted from the antenna of the broadcasting station A can be received using a single tuner receiver is a. Also, let b be a range in which a broadcast wave transmitted from the antenna of the broadcasting station B can be received using a single tuner receiver. When the frequencies of broadcast waves transmitted from the broadcasting stations A and B are the same, these ranges a and b are set so as not to overlap. However, a receiver that employs the diversity reception system as in this embodiment has improved reception sensitivity, so that the ranges a and b that can be received by the same output broadcast wave are expanded. Respective ranges after enlargement are set as a 'and b'. As a result, as shown in FIG. 4, when these ranges a ′ and b ′ overlap, it becomes possible to receive two broadcast waves having the same frequency in the overlapping region c. When receiving FM broadcast waves, if there are two broadcast waves of the same frequency, only broadcast waves with a good reception state are selectively received. However, in the case of an on-vehicle diversity receiver Since the direction of the two antennas 11 and 21 changes depending on the direction of the vehicle, a broadcast wave with a good reception state may be frequently switched depending on the direction of the vehicle and the reception state becomes unstable and output. It is very difficult for the user who is listening to the sound.

  The diversity switching determination unit 72 compares the audio signal levels corresponding to the two types of intermediate frequency signals obtained by the detection processing by the detection circuit 60, and maintains diversity reception when the audio signal levels are the same. Control is performed, and when these audio signal levels are different, control for stopping diversity reception is performed.

  FIG. 5 is an explanatory diagram when the audio signal levels corresponding to two types of intermediate frequency signals are the same. When the installation location of the diversity receiver is included in the range a or range b shown in FIG. 4, the audio signal level corresponding to one intermediate frequency signal output from one tuner unit 10 (FIG. 5A) And the audio signal level (FIG. 5B) corresponding to the other intermediate frequency signal output from the other tuner section 20 is the same.

  FIG. 6 is an explanatory diagram when the audio signal levels corresponding to the two types of intermediate frequency signals are different. Since the directions of the two antennas 11 and 21 are different, when the installation location of the diversity receiver is included in the range c shown in FIG. 4, the audio corresponding to one intermediate frequency signal output from one tuner unit 10 There is a case where the signal level (FIG. 6A) and the audio signal level (FIG. 6B) corresponding to the other intermediate frequency signal output from the other tuner unit 20 are different. Diversity switching determination unit 72, when detecting a state where the audio signal levels corresponding to the two types of intermediate frequency signals are different as shown in FIG. 6, sends an instruction to adder 30 to add the two intermediate frequency signals Is switched, and instead, only one of the intermediate signals is output as it is. For example, the adder 30 selectively outputs only the intermediate frequency signal output from one tuner unit 10 by this switching operation.

  The multipath determination unit 74 compares the output level of the multipath detection circuit 62 with a predetermined reference level to determine whether or not multipath has occurred, and is output from one tuner unit 10 by the diversity switching determination unit 72. The sensitivity of multipath detection is changed when only intermediate frequency signals are selected. The effect of multipath can be reduced by performing diversity reception. When diversity reception is performed, the intermediate frequency signal output from the adder 30 is input to the multipath detection circuit 62. However, when receiving by a single tuner, the influence of multipath is strong, so it is necessary to increase the detection sensitivity and take measures when multipath occurs. Specifically, the detection sensitivity is improved by lowering the reference level compared with the output level of the multipath detection circuit 62. If it is determined that multipath has occurred, an instruction is sent from the multipath determination unit 74 to the stereo demodulation circuit 48, and the value of channel separation at the time of stereo demodulation is lowered (closed to monaural) or changed to monaural. Control is performed. For example, if the degree of multipath is determined by setting a plurality of reference levels, the value of channel separation can be set or set to monaural depending on the degree. In addition, when one type of reference level is used, it is only necessary to forcibly change to monaural or to reduce the channel separation to a predetermined value when multipath occurs.

  The adjacent interference determination unit 76 compares the output level of the adjacent interference detection circuit 64 with a predetermined reference level to determine whether adjacent interference has occurred, and is output from one tuner unit 10 by the diversity switching determination unit 72. When only intermediate frequency signals are selected, the sensitivity of adjacent interference detection is changed. By performing diversity reception, it is possible to reduce the influence of adjacent interference. When diversity reception is being performed, the adjacent interference detection circuit 64 receives the intermediate frequency signal output from the adder 30. However, when receiving by a single tuner, the influence of adjacent interference is strong, so it is necessary to increase the detection sensitivity and take countermeasures when adjacent interference occurs. Specifically, the detection sensitivity is improved by lowering the reference level compared with the output level of the adjacent disturbance detection circuit 64. If it is determined that the adjacent interference has occurred, an instruction is sent from the adjacent interference determination unit 76 to the bandpass filter 40, and control to narrow the passband width is performed. At the same time as performing the band limitation, an instruction may be sent to the stereo demodulation circuit 48 to switch the stereo demodulation processing to monaural.

  The phase shifters 14 and 24, the adder 30, and the phase control circuit 32 described above are used as combining means, the detection circuit 42 and the stereo demodulation circuit 48 are used as demodulation processing means, the diversity switching determination unit 72 is used as switching means, and the detection circuit 60 is detected. The multipath determination unit 74 corresponds to the multipath determination unit, the adjacent interference determination unit 76 corresponds to the adjacent interference determination unit, and the bandpass filter 40 corresponds to the band variable unit.

  The diversity receiver according to the present embodiment has such a configuration. Next, an operation of switching between diversity reception and reception by a single tuner will be mainly described. FIG. 7 is a flowchart illustrating an operation procedure for switching between diversity reception and reception by a single tuner in the diversity receiver according to the first embodiment. When the diversity receiver according to the present embodiment is turned on, the diversity switching determination unit 72 sends an instruction to the adder 30 to add and output two input signals and output the two tuner units 10 and 20. Enable diversity reception (phase diversity on) (step 100).

Next, the detection circuit 60 detects the respective intermediate frequency signals output from the two tuner units 10 and 20 to detect their audio signal levels (step 101), and the diversity switching determination unit 72 It is determined whether or not the types of audio signal levels match (step 102). If they match, an affirmative determination is made, and this audio signal level detection and matching determination are repeated. On the other hand, in the case of mismatch, a negative determination is made in the determination of step 102, and the diversity switching determination unit 72 sends an instruction to output one input signal as it is to the adder 30 to disable diversity reception (phase diversity off). (Step 103). Since the adder 30 is realized by the DSP 90, in the addition process by the adder 30, the intermediate frequency signal input from the tuner unit 20 side is replaced with data in which all bits are “0”, and one tuner unit If an addition process is performed with the intermediate frequency signal input from the 10 side, only the intermediate frequency signal output from one tuner unit 10 is selected as a result, and only this intermediate frequency signal is used. The received operation is performed (step 104).

  For single tuner reception, the multipath determination unit 74 lowers the reference level for multipath detection (multipath detection level) (step 105), and the adjacent interference determination unit 76 detects the reference level for adjacent interference detection (adjacent interference). The detection level is lowered (step 106). This improves the detection sensitivity of multipath and adjacent interference, and measures to reduce the channel separation, switch to monaural, or narrow the passband width of the bandpass filter 40 when each phenomenon is detected. Taken.

Thereafter, the detection circuit 60 detects the respective intermediate frequency signals output from the two tuner units 10 and 20 and detects their audio signal levels (step 107), and the diversity switching determination unit 72 uses these two types. It is determined whether or not the audio signal levels match (step 108). If they do not match, a negative determination is made, and this audio signal level detection and matching determination are repeated. If they match, an affirmative determination is made in the determination in step 108, and the process returns to step 100 to enable diversity reception. At this time, the detection level lowered in steps 105 and 106 is returned to the original level for diversity reception.

As described above, in the diversity receiver according to the present embodiment, when phase diversity reception is performed and the audio signal levels of the signals received by the respective tuner units 10 and 20 are different, the phase diversity reception is stopped. Since switching to single tuner reception using one tuner unit 10, it is possible to prevent different signals from being received separately by the respective tuner units 10 and 20, and to receive only desired broadcast waves satisfactorily. become able to.

  In addition, when switching to single tuner reception, the multipath detection sensitivity can be increased by setting multipath detection sensitivity suitable for both diversity reception and single tuner reception. Can be realized.

  In addition, by increasing the detection sensitivity of adjacent interference when switching to single tuner reception, it is possible to set adjacent interference detection sensitivity suitable for both diversity reception and single tuner reception, and effective measures against adjacent interference can be taken. Can be realized.

[Second Embodiment]
FIG. 8 is a diagram illustrating a partial configuration of the diversity receiver according to the second embodiment. The diversity receiver shown in FIG. 8 is an analog-to-digital converter that converts the AGC voltage output from the AGC circuits 10F and 20F in the tuner units 10 and 20 into digital data with respect to the diversity receiver shown in FIG. The difference is that (ADC) 80 and 82 are added, and the control unit 70 is replaced with a control unit 70A. Hereinafter, the description will be given focusing on these changes.

  As shown in FIG. 8, one tuner unit 10 includes a tuning circuit 10A, a local oscillation circuit (LO) 10B, a mixer 10C, a bandpass filter 10D, an intermediate frequency amplifier circuit (IFA) 10E, and an AGC (automatic gain control) circuit. 10F and a PIN diode 10G. By changing the oscillation frequency of the local oscillation circuit 10B, the frequency of the broadcast wave to be selected can be changed. The band pass filter 10D extracts an intermediate frequency signal that is a frequency component in the vicinity of 10.7 MHz (for example, a band of ± 75 kHz) from the signal output from the mixer 10C. The AGC circuit 10F is for performing gain control according to the amplitude level of the intermediate frequency signal output from the bandpass filter 10D, and by applying an AGC voltage according to this amplitude level to the PIN diode 10G, The attenuation amount of the reception signal input from the antenna 11 to the tuning circuit 10A is varied. When a vehicle equipped with the diversity receiver of the present embodiment travels in a strong electric field area near the broadcast wave transmitting antenna, the AGC voltage becomes high. In such a situation, since intermodulation (IM, intermodulation) is likely to occur, in the present embodiment, in order to cancel diversity reception in a strong electric field region and switch to reception by a single tuner, the control unit 70A This AGC voltage is monitored. The other tuner unit 20 has the same configuration, and includes a tuning circuit 20A, a local oscillation circuit (LO) 20B, a mixer 20C, a bandpass filter 20D, an intermediate frequency amplifier circuit (IFA) 20E, and an AGC (automatic gain control). ) The circuit 20F and the PIN diode 20G are included.

In addition, the control unit 70A includes a diversity switching determination unit 72A, a multipath determination unit 74, an adjacent disturbance determination unit 76, and a strong electric field determination unit 78. The strong electric field determination unit 78 monitors the AGC voltage as the control voltage output from each of the AGC circuits 10F and 20F, and is in a strong electric field state when at least one of the AGC voltages exceeds the strong electric field reference value. Is determined. The diversity switching determination unit 72A is in addition to the operation of the diversity switching determination unit 72 shown in FIG. 1 (operation for switching between diversity reception and reception by a single tuner based on the audio signal level obtained by the detection processing by the detection circuit 60). The same switching operation is performed based on the determination result by the strong electric field determination unit 78. Specifically, the diversity switching determination unit 72A performs an operation of canceling diversity reception and switching to reception by a single tuner when the strong electric field determination unit 78 determines that the state is a strong electric field state. In this switching operation, the tuner unit with the lower value of the AGC voltage output from each of the AGC circuits 10F and 20F is selected. The strong electric field determination unit 78 described above corresponds to a strong electric field determination unit.

  FIG. 9 is a flowchart illustrating an operation procedure for switching between diversity reception and reception by a single tuner in the diversity receiver according to the second embodiment. The flowchart shown in FIG. 9 is obtained by adding steps 109 and 110 to the flowchart shown in FIG. In the following, these added steps 109 and 110 will be described.

Diversity switching determination unit 72A determines whether or not the two types of audio signal levels match in step 102, and if they match, makes an affirmative determination and then determines whether or not a strong electric field state exists. (Step 109). If it is not a strong electric field state, a negative determination is made, and the process returns to step 101 to repeat audio signal level detection and coincidence determination. In the case of a strong electric field state, an affirmative determination is made in the determination in step 109, and an operation for shifting to reception of a single tuner in step 103 and subsequent steps is performed.

In addition, the diversity switching determination unit 72A determines whether or not the two types of audio signal levels match in step 108, and in the case of a mismatch, makes a negative determination to maintain reception by the single tuner and in step 107. Return and repeat audio signal level detection and coincidence determination. If the two types of audio signal levels match, an affirmative determination is made in the determination of step 108, and then the diversity switching determination unit 72A determines whether or not the strong electric field state is present (step 110). . In the case of a strong electric field state, an affirmative determination is made, and reception by a single tuner is maintained, and the process returns to step 107 to repeat audio signal level detection and coincidence determination. On the other hand, if it is not a strong electric field state, a negative determination is made in step 110, and the process returns to step 100 to enable diversity reception. At this time, the detection level lowered in steps 105 and 106 is returned to the original level for diversity reception.

  As described above, in the diversity receiver according to the present embodiment, it is possible to prevent the occurrence of intermodulation by canceling diversity reception and switching to single tuner reception in a strong electric field state where intermodulation is likely to occur. In particular, a strong electric field state can be easily detected by monitoring the control voltages of the AGC circuits 10F and 20F that operate according to the electric field strength.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention. For example, in the above-described embodiment, the diversity receiver including the two tuner units 10 and 20 has been described. However, the present invention may be applied to a diversity receiver including three or more tuner units.

It is a figure which shows the detailed structure of the diversity receiver of 1st Embodiment. It is a figure which shows the specific structure of a multipath detection circuit. It is a figure which shows the specific structure of an adjacent disturbance detection circuit. It is a figure which shows the outline | summary of a broadcast wave and a receiving range. It is explanatory drawing in case the audio signal level corresponding to two types of intermediate frequency signals is the same. It is explanatory drawing when the audio signal level corresponding to two types of intermediate frequency signals differs. It is a flowchart which shows the operation | movement procedure which switches diversity reception and reception by a single tuner in the diversity receiver of 1st Embodiment. It is a figure which shows the partial structure of the diversity receiver of 2nd Embodiment. It is a flowchart which shows the operation | movement procedure which switches diversity reception and reception by a single tuner in the diversity receiver of 2nd Embodiment.

Explanation of symbols

10, 20 Tuner section 11, 21 Antenna 12, 22 Analog-digital converter (ADC)
14, 24 Phase shifter 30 Adder 32 Phase control circuit 40 Band pass filter (BPF)
42, 60 Detection circuit 44 Soft mute circuit 46 Noise canceller (NC)
48 Stereo demodulation circuit 62 Multipath detection circuit 64 Adjacent disturbance detection circuit 70 Control unit 72 Diversity switching determination unit 74 Multipath determination unit 76 Adjacent disturbance determination unit

Claims (14)

A plurality of tuners connected to different antennas;
Combining means for adjusting and combining the phases of the output signals of at least one of the plurality of tuner sections;
Demodulation processing means for performing demodulation processing on the input signal;
When the audio signal levels of the plurality of signals output from each of the plurality of tuner units are the same, the signal output from the synthesizing unit is set as a target of demodulation processing by the demodulation processing unit, Switching means for setting a signal output from any of the plurality of tuner sections as a target of demodulation processing by the demodulation processing means when the audio signal level of the signal is different;
A diversity receiver comprising: In claim 1,
The diversity receiver characterized in that the combining means adjusts the phase so that the amplitude of the combined signal is maximized. In claim 1 or 2,
Detection means for detecting signals output from each of the plurality of tuner units to detect an audio signal level corresponding to these signals is further provided.
The switching means determines whether or not the audio signal levels of the plurality of signals output from each of the plurality of tuner units are the same based on the audio signal level detected by the detection means. Diversity receiver. In any one of Claims 1-3,
Multipath determination means for determining the presence or absence of multipath occurrence with a predetermined detection sensitivity and changing the detection sensitivity for determining presence or absence of multipath generation according to the setting content by the switching means is further provided. Diversity receiver. In claim 4,
A diversity receiver characterized in that the detection sensitivity is increased when a setting for setting a signal output from any of the plurality of tuner units as a target of demodulation processing by the demodulation processing means is made by the switching means. In claim 4 or 5,
The demodulation processing by the demodulation processing means includes FM stereo demodulation processing,
The multipath determining means sends an instruction to the demodulation processing means when determining that multipath has occurred, and reduces the channel separation of the signal obtained by the FM stereo demodulation processing. Diversity receiver. In claim 4 or 5,
The demodulation processing by the demodulation processing means includes FM stereo demodulation processing,
The multipath determining means, when determining that multipath has occurred, sends an instruction to the demodulation processing means, and converts the signal obtained by the FM stereo demodulation processing to monaural. Machine. In any one of Claims 1-3,
The apparatus further comprises: adjacent interference determination means for determining presence / absence of adjacent interference occurrence with a predetermined detection sensitivity and changing the detection sensitivity for determining presence / absence of adjacent interference according to the setting content by the switching means. Diversity receiver. In claim 8,
A diversity receiver characterized in that the detection sensitivity is increased when a setting for setting a signal output from any of the plurality of tuner units as a target of demodulation processing by the demodulation processing means is made by the switching means. In claim 8 or 9,
Band variable means for changing the band of a signal to be demodulated by the demodulation processing means,
The diversity receiver according to claim 1, wherein when the adjacent interference determination unit determines that adjacent interference has occurred, the adjacent interference determination unit sends an instruction to the band variable unit to narrow the band. In any one of Claims 1-10,
A strong electric field determination means for determining whether or not the electric field is strong,
The switching means sets the signal output from the synthesizing means as a target for demodulation processing by the demodulation processing means when the strong electric field determination means determines that the strong electric field state is not present, A diversity receiver characterized by setting a signal output from one of the plurality of tuner units as a target of demodulation processing by the demodulation processing means when it is determined that there is a certain effect. In claim 11,
The tuner unit includes a tuning circuit that allows a frequency component in the vicinity of a tuning frequency to pass among signals input through the antenna, and an automatic gain that controls the gain of the signal input to the tuning circuit by varying a control voltage. Control circuit and
The diversity receiver according to claim 1, wherein the strong electric field determining means determines whether or not a strong electric field is present according to the value of the control voltage. In any one of Claims 1-12,
A diversity receiver for reproducing an audio signal by receiving FM broadcast waves and performing FM demodulation and stereo demodulation by the demodulation processing means. In any one of Claims 1-12,
A diversity receiver that is mounted on a vehicle.

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