JPH07154351A - Am stereo receiver - Google Patents

Abstract

PURPOSE:To reduce noise due to electric field intensity drop and the fluctuation of sound image localization by mixing right and left stereo sound signals corresponding to the electric field intensity of a received radio wave. CONSTITUTION:When the electric field intensity of the input radio wave of an antenna 10 starts lowering, the voltage of an S meter output signal S0 is lowered, a control signal S1 from a comparator part 70 is turned to an H level, the electronic switch of a mixing part 60 is turned on, signal lines L and R are connected by mixing resistance, and the separation of left and right signals is lowered. When the electric field intensity is further lowered, output signals S2 and S3 of the comparator part 70 are succesisvely turned to the H level, the lines L and R are connected by the mixing resistance, an impedance between the lines L and R is lowered, a mixing amount is increased, the separation is further lowered. Thus, the generation of fluctuation in the sound image localization can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AM stereo receiver, and more particularly to an AM stereo receiver having a separation control function for controlling the degree of separation of demodulated outputs according to the electric field strength of radio waves.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing the structure of a conventional AM stereo receiver. In the figure, 10 is an antenna for inducing a high frequency signal from a radio wave. Reference numeral 20 denotes an AM tuner section that performs selection of a target high frequency signal, amplification of the selected high frequency signal, frequency conversion, and the like. 30 is AM
The stereo decoder unit performs detection and stereo demodulation of the intermediate frequency signal IF output from the tuner unit 20. 40 is a stereo decoder unit 3 when receiving a stereo broadcast
This is a switch for instructing 0 to perform monaural demodulation. Reference numerals 51 and 52 are amplifiers for amplifying the left and right signals output from the stereo decoder unit 30, respectively. Reference numerals 53 and 54 are speakers that output the signals amplified by the amplifiers 51 and 52 as sound waves. The user operates the switch 40 such that stereo demodulation is performed when the electric field strength of the radio wave is sufficiently high, and monaural demodulation is performed when the electric field strength is low and not sufficient for stereo demodulation. It was

FIG. 8 shows C described in Japanese Utility Model Publication 4-18270.
FIG. 4 is a circuit diagram showing a configuration of a main part of a QUAM-type AM stereo receiver, which is an example of a detailed configuration of the conventional AM stereo receiver described above. In this conventional example, a wide band filter 101 and a narrow band filter 102 having the characteristics shown in FIG. 9 are connected in series after the intermediate frequency transformer 100. An AM stereo decoder section 104 is connected to an output section of the broadband filter 101 via an intermediate frequency amplifier 103. On the other hand, an envelope detection circuit 105 is connected to the output section of the narrow band filter 102. Reference numeral 106 denotes a voltage conversion circuit that converts the signal level of the carrier wave detected by the envelope detection circuit 105 into a voltage value corresponding to this level. A level 107 compares the voltage value from the voltage conversion circuit 106 with a reference value, and outputs a selection signal for selecting the L + R signal and the L or R signal according to the signal level of the carrier wave detected by the envelope detection circuit 105. The detection circuit includes a comparator 108 and a plurality of light emitting diodes 109. Reference numeral 110 denotes a mode selection switch for manually selecting each mode of monaural and stereo. 111 passes the narrow band filter 102 in response to the selection signal output from the level detection circuit 107,
It is a signal switching circuit that switches and outputs the L + R signal subjected to envelope detection by the envelope detection circuit 105 and the L signal and the R signal separated by the AM stereo decoder unit 104. Note that 112 and 113 are output terminals on the left and right, respectively, and 114 is an indicator showing a stereo broadcast reception state provided between the drain of the FET 115 and the switch circuit 116 of the AM stereo decoder unit 104,
Reference numeral 117 is a matrix circuit of the AM stereo decoder unit 104.

Next, the operation will be described. The AM stereo signal converted to the intermediate frequency by the mixing circuit (not shown) is an intermediate frequency transformer 100 and a wide band filter 101.
It is branched into two through. One AM stereo signal passes through the narrow band filter 102 to the envelope detection circuit 105, and the other AM stereo signal receives the intermediate frequency amplifier 1.
03 to the AM stereo decoder unit 104. The AM stereo signal input to the envelope detection circuit 105 is envelope-detected here to extract the L + R signal, and the L + R signal is commonly applied to the switches 118 and 119 of the signal switching circuit 111. The signal level of the carrier wave detected by the envelope detection circuit 105 is converted into a voltage value by the voltage conversion circuit 106 and added to one of the comparators 108 of the level detection circuit 107. The comparator 108 compares the input voltage with the reference voltage and outputs a selection signal according to the difference between them.

When receiving the stereo broadcast, when the mode selection switch 110 is switched to the stereo mode, the mode selection switch 110 is turned on. Moreover, when the AM stereo signal is tuned and has a strong electric field, the output voltage of the voltage conversion circuit 106 becomes large.
The output level from the level detection circuit 107 also rises and each light emitting diode 109 is turned on according to the difference from the reference voltage. At the same time, this high-level selection signal is applied to the base of the switching transistor 120 of the signal switching circuit 111. Therefore, the switching transistor 1
20 turns on. Then, no current flows through the base of the switching transistor 121, and this transistor is cut off. As a result, the RS flip-flop 122 is set and a high level signal is output. Further, the RS flip-flop 123 is reset and a low level signal is output. As a result, the switches 124 and 125 are turned on, and the switches 118 and 119 are turned on.
Turns off. Therefore, the L signal and the R signal separated by the AM stereo decoder unit 104 through the wide band filter 101 are extracted from the left and right output terminals 112 and 113 via the switches 124 and 125. As a result, the L signal and the R signal are extracted from the AM stereo signal including the directional high frequency band, so that a sound with a stereo feeling can be obtained.

Further, when the tune is achieved, the FET4
A high level signal is added to the 0 gate, and AM
At this time, the terminal 116a of the switch circuit 116 of the stereo decoder unit 104 is at the low level, so that the indicator 114 indicating the reception of the stereo signal is turned on.

On the other hand, when the stereo signal becomes a weak electric field due to detuning, the output voltage of the voltage conversion circuit 106 becomes small, so that the output level from the level detection circuit 107 becomes low level. Therefore, the light emitting diode 109 is turned off, and the low-level selection signal is transmitted to the signal switching circuit 1.
11 to the base of the switching transistor 120. Therefore, the switching transistor 120 is in a cutoff state. Then, a current flows through the base of the switching transistor 121, and this transistor is turned on. As a result, the RS flip-flop 122 is reset, a low level signal is output, and R
The S flip-flop 123 is set and a high level signal is output. As a result, the switches 118, 119
Only the switches are turned on and the switches 124 and 125 are turned off. Therefore, the L + R signal detected by the envelope detection circuit 105 through the narrow band filter 102 is transmitted to the switch 1
Via left and right output terminals 112 and 113
Taken from. Further, in this case, in the AM stereo decoder unit 104, even if the noise due to the VCO lock loss occurs, the switches 124 and 125 are both turned off, so that the noise is prevented from mixing and the sound with less interference is obtained. To be Furthermore, since a low level signal is applied to the gate of the FET 115, the indicator 11
4 goes out.

When receiving the monaural broadcast, when the mode selection switch 110 is switched to the monaural mode, the mode selection switch is turned off, so that the switching transistor 120 of the signal switching circuit 111 is turned off and the switch 118 is turned on. , 119 are turned on so that only the detection output of the envelope detection circuit 105 is always obtained. Also, the indicator 114 does not light up.

[0009]

Since the conventional AM stereo receiver is constructed as described above, noise and fluctuation of sound image localization occur due to a decrease in electric field strength during reception of a stereo broadcast, which is excellent. There was a problem that it could not receive proper stereo reception. Further, when the demodulation output is switched from stereo to monaural with a weak electric field, the high frequency component of the demodulation output is reduced by switching from the wide band filter to the narrow band filter, which causes a sense of discomfort due to a sudden change in sound quality. Furthermore, there is a problem that the change in the sound field is uncomfortable due to the abrupt change in the separation (left / right separation).

The present invention has been made in order to solve the above problems, and reduces the feeling of strangeness such as noise and fluctuation of sound image localization when the electric field strength of broadcast radio waves is lowered during reception of an AM stereo broadcast. Can be AM
It is intended to provide a stereo receiver.

[0011]

According to a first aspect of the present invention, an AM stereo receiver includes an electric field strength signal output means for outputting an electric field strength signal corresponding to the electric field strength of a received radio wave, and the electric field strength signal output means. Based on the above, the left and right stereo audio signals are mixed with each other to control the left and right separation degree.

An AM stereo receiver according to a second aspect of the present invention is the AM stereo receiver according to the first aspect, which performs monaural demodulation on a received radio wave and outputs a monaural audio signal. Means for reproducing a monaural audio signal when the electric field strength signal from the electric field strength signal output means is below a predetermined value, and when the electric field strength signal from the electric field strength signal output means is above a predetermined value. Is for reproducing a stereo audio signal whose left-right separation degree is controlled by the left-right signal mixing means.

Further, in the AM stereo receiver according to the invention described in claim 3, the AM stereo receiver according to claim 1 or 2 is provided.
In the stereo receiver, the left and right signal mixing means is
As the electric field strength of the received radio wave becomes weaker, a high-pass filter whose frequency characteristic changes so as to pass a signal of a lower frequency is provided, and the left and right stereo audio signals that have passed through this high-pass filter are mixed. Then, the left / right separation degree is controlled.

Further, in the AM stereo receiver according to the invention described in claim 4, in the AM stereo receiver according to claims 1 to 3, the electric field strength signal output means discriminates the electric field strength of the received radio wave step by step. Then, the left / right separation degree is controlled stepwise according to the determined level.

[0015]

The left and right signal mixing means of the AM stereo receiver according to the first aspect of the present invention mixes the left and right stereo audio signals with each other based on the electric field strength of the received radio waves to control the left and right separation degree. Even in the weak case, the reverse phase noise and the fluctuation of the sound image localization can be reduced.

According to another aspect of the invention, the AM stereo receiver demodulates by the monaural demodulating means when the electric field strength of the received radio wave is less than a predetermined value, and when the electric field strength of the radio wave is more than the predetermined value. The left and right signal mixing means mix the left and right stereo audio signals with each other based on the electric field strength of the received radio waves to control the left and right separation degree. Therefore, when the radio wave is weak, monaural demodulation is performed and the S / N can be increased.

In the left and right signal mixing means of the AM stereo receiver according to the third aspect of the present invention, as the electric field strength of the received radio wave becomes weaker, the high frequency range in which the frequency characteristic changes so as to pass a signal of a lower frequency as well. A pass filter is provided, and the left and right stereo audio signals that have passed through the high pass filter are mixed to control the left and right separation degree. Therefore, it is possible to reduce the reverse phase noise and the fluctuation of the sound image localization when the radio wave is weak without unnecessarily lowering the left-right separation in the low frequency range.

In the AM stereo receiver according to the present invention as defined in claim 4, the electric field strength signal output means determines the electric field strength of the received radio wave stepwise, and the left-right separation degree is stepwise changed according to the judged level. Since the control is performed, it is possible to reduce the reverse phase noise and the fluctuation of the sound image localization even when the radio wave is weak.

[0019]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an AM stereo receiver according to an embodiment of the present invention. The same parts as those of the conventional example shown in FIG. 7 are designated by the same reference numerals, and the duplicated description will be omitted. Reference numeral 60 denotes a mixing unit as left and right signal mixing means, which mixes the left signal and the right signal output from the stereo decoder unit 30 with each other and outputs them to the low frequency amplifiers 51 and 52. Reference numeral 70 denotes a comparator unit serving as an electric field intensity signal output means, and a control signal S1 for controlling the mixing amount of the mixing unit 60 based on the electric field intensity of the received radio wave by the S meter output signal S0 from the AM tuner unit 20. S2, S3 and stereo decoder section (stereo demodulation means, monaural demodulation means) 30
A monaural switching signal S4 for instructing to perform monaural demodulation is output. Therefore, the stereo decoder unit 30 operates as a stereo demodulation unit when there is no instruction by the monaural switching signal S4 and as a monaural demodulation unit when there is an instruction.

FIG. 2 is a circuit diagram showing a detailed configuration of the mixing section 60 and the comparator section 70. In the mixing section 60, mixing resistors 61, 62 and 63 are connected between the left signal line L and the right signal line R via electronic switches 64, 65 and 66, respectively. The comparator unit 70 includes four comparators 71, 72, 73,
74, and the negative terminal of each comparator is S
The meter output signal is being input. The voltage of the DC power supply P is divided by the resistors R1, R2, R3, R4, and R5, and the divided voltages are input to the positive terminals of the respective comparators. Comparators 71, 72, 73
Output signals S1, S2, S3 of the electronic switches 64, 6
It is adapted to be supplied to the ON / OFF control terminals of 5, 66, respectively. The output of the comparator 74 is supplied to the stereo decoder unit 30 as a monaural switching signal S4.

Next, the operation will be described. First, a case where the electric field strength of the radio wave input to the antenna 10 is sufficiently high for stereo demodulation will be described. Since the level of the S meter output signal S0 output from the AM tuner unit 20 is high, the output signals S1 to S1 of the comparators 71 to 74 are
All of S4 becomes "L" level. Therefore, the stereo decoder unit 30 executes stereo demodulation. Also, the electronic switches 64, 65, 66 are turned off, and the mixing unit 6
The separation (left and right separation) of the left signal and the right signal output from 0 is maximized, and a stereo broadcast with a sense of stereo and a small amount of noise is reproduced.

When the electric field strength of the radio wave input to the antenna 10 starts to decrease, the voltage of the S meter output signal S0 decreases, and the control signal S1 output from the comparator 71 becomes "H" level. Therefore, the electronic switch 64 is turned on, the signal lines L and R are connected by the mixing resistor 61, and the separation of the left signal and the right signal is reduced.

Further, as the electric field strength of the radio wave input to the antenna 10 decreases, the output signals of the comparators 72 and 73 sequentially become "H" level, and the electronic switches 65 and 66 are turned on. The signal lines L and R are connected by the mixing resistors 62 and 63. As a result, the impedance between the signal lines L and R decreases, the mixing amount increases, and the separation further decreases.

In the AM stereo, due to its nature, the anti-phase noise component increases in the left signal and the right signal under a medium and weak electric field. Therefore, under a medium and weak electric field, the S / N ratio deteriorates about 3 dB in stereo demodulation with respect to monaural, but the amount of noise on the auditory sense increases considerably. Further, under such a condition, a fluctuation in sound image localization peculiar to AM stereo occurs. Therefore, at the time of stereo demodulation, the impedance between the signal lines L and R is decreased according to the decrease of the electric field strength, and the mixing amount is controlled to cancel the anti-phase noise component appearing in the demodulated output of the left signal and the right signal, It is possible to prevent an increase in audible noise without lowering the high frequency component of the demodulation output. Further, by reducing the separation of the L signal and the R signal, it is possible to reduce the occurrence of fluctuation in sound image localization.

When the electric field strength of the radio wave input to the antenna 10 further decreases, the monaural switching signal S4 output from the comparator 74 also becomes "H" level, and the demodulation mode of the stereo decoder section 30 is changed to monaural demodulation. Switch. In this way, when switching to monaural demodulation, the S / N ratio can be made higher than that of stereo demodulation, and sound image localization does not fluctuate.

FIG. 3 shows a change characteristic of the separation of the left signal and the right signal of the demodulated output with respect to the level of the S meter output signal S0 during the above-mentioned operation. When the electric field strength decreases and the S meter output signal S0 decreases, the control signals S1, S2, S3 of the comparators 71, 72, 73 sequentially become “H” according to the S meter output signal, respectively,
The electronic switches 64, 65, 66 are turned on. Therefore, the mixing resistors 61, 62, 63 are sequentially connected between the signal lines L, R, and the left signal and the right signal are mixed through these resistors, and as shown in FIG. Separation gradually decreases. When the electric field strength further decreases, the comparator 7
By 4, the demodulation mode of the stereo decoder unit 30 becomes the monaural demodulation mode, and the separation becomes 0 dB.

As described above, the separation of the left signal and the right signal is controlled based on the voltage of the S meter output signal S0 indicating the electric field strength of the radio wave input to the antenna 10, and S
When the voltage of the meter output is extremely low, the demodulation mode is switched to monaural so that stereo reception can be performed with an increase in the amount of noise on the perceptual sensation and less fluctuation in sound image localization depending on the electric field strength. It is possible to reduce the discomfort caused by the change in the separation characteristic and the change in the sound field that occurs when switching between the stereo and monaural modes.

Example 2. In the above-described embodiment, a plurality of mixing resistors are prepared to gradually reduce the separation between the left signal and the right signal. However, instead of the plurality of mixing resistors, an electronic potentiometer is used to output the S meter output signal. It is also possible to change the resistance value of the electronic volume to continuously reduce the separation.

Example 3. In the above-described embodiment, the mixing resistors are used to reduce the separation of the left signal and the right signal, but capacitors may be used instead of the mixing resistors 61, 62, 63 of the mixing section 60 shown in FIG. FIG. 4 shows a mixing section (left and right signal mixing means) 80 using a capacitor for mixing.
3 is a circuit diagram showing the configuration of FIG. Capacitors (Takashiro pass filters) 81, 82, 83 are connected between the left and right signal lines L, R via electronic switches 64, 65, 66. The electronic switches 64, 65, 66 are the comparator unit 7
It is turned on / off by signals S1, S2, S3 from 0. By mixing using a plurality of capacitors, the frequency band to be mixed is changed and the left and right signals are mixed.

FIG. 5 shows a separation change characteristic of the demodulation output with respect to the voltage of the S meter output signal SO in the third embodiment. FIG. 5A shows the separation change characteristic when the demodulation output frequency is 1 kHz, and FIG. 5B shows the separation change characteristic when the demodulation output frequency is 400 Hz.

The impedance of the capacitor differs depending on the frequency. The impedance is low at high frequencies and high at low frequencies. Therefore, as shown in FIGS. 5A and 5B, the separation characteristics differ depending on the frequency, and the separation change of the high frequency component is large and the separation change of the low frequency component is large with respect to the electric field strength of the radio wave input to the antenna 10. Is few. That is, the capacitors 81, 82 and 83 form a high-pass filter, and as these capacitors are connected by the electronic switches 64, 65 and 66, the separation in the lower frequency band also decreases. It is the antiphase noise of the high frequency component that is generated in the middle and weak electric fields and becomes unpleasant to the sense of hearing, and the low frequency component does not cause a feeling of strangeness. Therefore, in this embodiment, the low-frequency components that have little influence are controlled so that the separation does not change so much, and the high-frequency components that have a large influence change more. Therefore, it is possible to perform reproduction with less negative phase noise and less discomfort in hearing without unnecessarily lowering the low-frequency component separation.

Example 4. In Example 1 and Example 2,
A resistor is used for mixing the left signal and the right signal, and a capacitor is used in the third embodiment, but both a capacitor and a resistor may be used for mixing.

FIG. 6 shows a mixing section (left and right signal mixing means) 9 which uses both a capacitor and a resistor for mixing.
It is a circuit diagram which shows the structure of 0. As shown in the figure, capacitors 91 and 92 are connected between the left and right signal lines L and R via electronic switches 64 and 65. When the level of the S meter output signal S0 is high, the signal lines L and R are in a separated state, and the separation of the left and right signals is maximized. Further, as the electric field strength of the radio wave becomes lower, the electronic switches 64, 6 will be operated as in the above-described embodiment.
5, 66 are sequentially turned on. That is, the capacitors 91 and 92 and the resistor 93 are sequentially connected between the signal lines L and R. Further, when the electric field strength further decreases, the control signal S
4 becomes "H", and the stereo decoder unit 30 performs monaural demodulation. In this way, the separation is reduced by the capacitor in the initial stage, and the separation is reduced over the entire frequency band by the resistor immediately before switching to monaural demodulation, so that the transition to monaural demodulation becomes more natural. .

[0034]

As described above, A of the invention of claim 1
According to the M stereo receiver, the left and right signal mixing means is configured to mix the left and right stereo audio signals with each other based on the electric field strength of the received radio waves to control the left and right separation degree. Even in this case, there is an effect that it is possible to reduce the reverse phase noise and the fluctuation of the sound image localization.

According to the AM stereo receiver of the second aspect of the present invention, when the electric field strength of the received radio wave is less than or equal to the predetermined value, demodulation is performed by the monaural demodulating means, and the electric field strength of the radio wave is greater than or equal to the predetermined value. In the case of, by the left and right signal mixing means, based on the electric field strength of the received radio wave,
Since the left and right stereo audio signals are mixed with each other to control the left and right separation degree, anti-phase noise and fluctuation of sound image localization are reduced, and when the radio wave is weak, monaural demodulation is used and the S / N ratio is increased. There is an effect that can be.

Furthermore, according to the left and right signal mixing means of the AM stereo receiver of the third aspect of the present invention, the frequency characteristic is changed so that the lower frequency signal is passed as the electric field strength of the received radio wave is weakened. It is equipped with a high pass filter that controls the left and right stereo audio signals that have passed through this high pass filter to control the left and right separation degree. There is an effect that it is possible to reduce the reverse phase noise and the fluctuation of the sound image localization when the radio wave is weak without lowering.

According to the AM stereo receiver of the fourth aspect of the invention, the electric field strength signal output means discriminates the electric field strength of the received radio wave stepwise, and the left-right separation degree is determined according to the judged level. Since the control is performed stepwise, it is possible to reduce the anti-phase noise and the fluctuation of the sound image localization even when the radio wave is weak.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an AM stereo receiver according to an embodiment of the present invention.

2 is a circuit diagram showing a detailed configuration of a mixing unit and a comparator unit of the AM stereo receiver shown in FIG.

FIG. 3 is a diagram showing a separation change characteristic of a left signal and a right signal of a demodulation output with respect to an S meter output signal in the embodiment shown in FIGS. 1 and 2.

FIG. 4 is a circuit diagram showing a configuration of a mixing unit using a capacitor for mixing.

FIG. 5 is a diagram showing a separation change characteristic of a demodulation output with respect to a voltage of an S meter output signal in the third embodiment. FIG. 5A shows the separation change characteristic when the demodulation output frequency is 1 KHz, and FIG. 5B is the diagram showing the separation change characteristic when the demodulation output frequency is 400 Hz.

FIG. 6 is a circuit diagram showing a configuration of a mixing unit using both a capacitor and a resistor for mixing.

FIG. 7 is a block diagram showing a configuration of a conventional AM stereo receiver.

8 is a circuit diagram showing a configuration of a main part of a conventional C-QUAM AM stereo receiver, and is an example of a detailed configuration of the conventional AM stereo receiver shown in FIG.

FIG. 9 is a schematic diagram of 2 used in the AM stereo receiver of FIG.
It is a figure which shows the characteristic of one bandpass filter.

[Explanation of symbols]

20 AM tuner section 30 Stereo decoder section (stereo demodulation means, monaural demodulation means) 60, 80, 90 Mixing section (left and right signal mixing means) 70 Comparator section (electric field intensity signal output means) 81, 82, 83, 91, 92 Capacitors (High pass filter) S0 S meter output signal

Claims (4)

[Claims] 1. An AM stereo receiver having stereo demodulation means for demodulating a stereo signal from a received radio wave to output left and right stereo audio signals, and outputting an electric field strength signal corresponding to the electric field strength of the received radio wave. An AM stereo receiver comprising: an electric field strength signal output means; and a left and right signal mixing means for controlling the left and right separation degree by mixing the left and right stereo audio signals with each other based on the electric field strength signal. 2. An AM stereo receiver having stereo demodulation means for demodulating a stereo signal from a received radio wave to output left and right stereo audio signals, and outputting an electric field strength signal corresponding to the electric field strength of the received radio wave. An electric field strength signal output means, a left and right signal mixing means for mixing the left and right stereo audio signals with each other based on the electric field strength signal to control the left and right separation degree, and monaural demodulation for the received radio wave. A monaural demodulation means for reproducing a monaural audio signal, and when the electric field strength signal from the electric field strength signal output means is below a predetermined value, reproduces the monaural sound signal and outputs from the electric field strength signal output means. When the electric field strength signal is larger than the predetermined value, the left / right signal mixing means controls the left / right separation degree. An AM stereo receiver characterized by reproducing a Leo audio signal. 3. The left and right signal mixing means is provided with a high-pass filter whose frequency characteristic changes so that signals of lower frequencies are also passed as the electric field strength of the received radio wave is weakened. 3. The AM according to claim 1, wherein the left and right stereo audio signals that have passed through the pass filter are mixed to control the left and right separation degree.
Stereo receiver. 4. The electric field intensity signal output means discriminates the electric field intensity of the received radio wave stepwise, and controls the left / right separation degree stepwise according to the discriminated level. The AM stereo receiver according to any one of 1 to 3.