JPH10262014A - Fm-broadcasting receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an FM-broadcasting receiver, capable of automatically switching and receiving stereo broadcasting by two different systems and the stereo broadcasting by the same system, corresponding to a reception frequency. SOLUTION: FM detection output, which is outputted from an IF amplification and FM detection stage 2 is supplied to a pilot stereo demodulator 3 and a polar stereo demodulator 4 and demodulated and specified band identification signals (d) corresponding to a broadcasting frequency band, including the reception frequency selected for broadcasting reception and stereo demodulation detection signals (e) for indicating that the polar stereo demodulator 4 performs stereo demodulation, are supplied to an AND gate circuit 17. Based on selection control signals (f) outputted from the AND gate circuit 17, one of demodulation outputs from the pilot stereo demodulator 3 and the demodulation output from the polar stereo demodulator 4 is selected by an output signal selection circuit 11 and is sent out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM broadcast receiver, and more particularly to an FM broadcast receiver that can be used for both a pilot tone system and a polar modulation system.

[0002]

2. Description of the Related Art Conventionally, FM stereo broadcasting is a pilot tone system. The pilot tone system is 19kHz
Of the maximum frequency shift (75 kHz)
z) at 10%. A 38 kHz subcarrier synchronized with this pilot tone signal is generated by a PLL circuit,
The composite signal is switched by the subcarrier and stereo-demodulated into an L signal and an R signal.

[0003] In Eastern European countries, the receivable band 65
The same broadcast system, i.e., pilot tone system, is adopted for all of the frequency bands of up to 74 MHz and 87.5 to 108 MHz. On the other hand, in the FM stereo broadcasting system in Russia, a polar modulation system is used in a receiving frequency band of 65 to 74 MHz, and a pilot tone system is used in a receiving frequency band of 87.5 to 108 MHz. Therefore, FM broadcasting receivers in Eastern Europe and Russia require a stereo demodulation circuit and a pilot stereo demodulation system using the polar modulation method for the reception band of 65 to 74 MHz, and an FM stereo demodulation circuit using the pilot tone method for the reception band of 87.5 to 108 MHz. Becomes

In the polar modulation method, a subcarrier of 31.25 kHz is suppressed at 20% of the maximum frequency shift (50 kHz) and transmitted. This is called a suppression filter (Q = 100)
, And the composite signal is switched to stereo-demodulate into an L signal and an R signal. In addition, a stereo state or a monaural state is set depending on the presence or absence of a subcarrier. FIGS. 3 and 4 show the difference between the pilot tone method and the polar modulation method, and FIGS. 4A and 4B show the respective modulation frequency arrangements. FIG. 4A shows the case of the polar modulation method, and FIG.
Indicates the case of the pilot tone system.

[0005]

As described above, the FM broadcast receivers for Eastern Europe and Russia have a problem that FM broadcast receivers corresponding to Eastern Europe and Russia are required. Further, even with one FM broadcast receiver for each region, there is a problem that a switch for manually switching between the pilot tone system and the polar modulation system is required.

An object of the present invention is to provide an FM broadcast receiver capable of automatically switching and receiving stereo broadcasts of two different systems.

[0007]

Means for Solving the Problems Claim 1 according to the present invention.
The FM broadcast receiver according to the present invention is characterized in that the first and second stereo demodulators each receiving an FM detection output as input and corresponding to two different modulation schemes, and that the second stereo demodulator performs stereo demodulation. An output signal selection circuit for selecting one of a demodulated output from the first stereo demodulator and a demodulated output from the second stereo demodulator based on the indicated signal.

According to the first aspect of the present invention, in the FM broadcast receiver, an output signal selection circuit outputs a signal from the first stereo demodulator based on a signal indicating that the second stereo demodulator performs stereo demodulation. One of the demodulated output and the demodulated output from the second stereo demodulator is automatically selected.

According to a second aspect of the present invention, there is provided an FM broadcast receiver having first and second stereo demodulators each having an FM detection output as input and corresponding to two different modulation schemes, and AND operation means for performing an AND operation on a signal corresponding to the first or second broadcast frequency band including the selected reception frequency and a signal indicating that the second stereo demodulator is performing stereo demodulation. And an output signal selection circuit for selecting one of a demodulated output from the first stereo demodulator and a demodulated output from the second stereo demodulator based on the logical product operation output.

According to a second aspect of the present invention, when the reception frequency is included in the first broadcast frequency band and stereo demodulated by the second stereo demodulator, an output signal selection circuit is provided. When the stereo demodulated output from the second stereo demodulator is selected, and the reception frequency is included in the first or second broadcast frequency band, when the second demodulator does not perform stereo demodulation, A first stereo demodulated output is selected.
Therefore, only when the stereo demodulation is performed by the second stereo demodulation and the reception frequency is included in the first broadcast frequency band, the stereo demodulation output from the second stereo demodulator is selected. When stereo demodulation is not performed by the second stereo demodulator, that is, when the modulation method does not correspond to the second stereo demodulator, the output from the first stereo demodulator is selected and this selection is automatically performed. This eliminates the need for the user to switch manually.

According to a third aspect of the present invention, there is provided an FM broadcast receiver according to the first or second aspect, wherein one modulation system is a pilot tone system and the other is a polar modulation system. , The first stereo demodulator is a stereo demodulator corresponding to the pilot tone system, and the second stereo demodulator is a stereo demodulator corresponding to the polar modulation system.

The FM broadcast receiver according to the third aspect of the present invention can be applied to Eastern European and Russian broadcast systems, and is suitable for the case of destinations for both.

According to a fourth aspect of the present invention, in the FM broadcast receiver, the second stereo demodulator is forcibly activated based on the signal corresponding to the first broadcast frequency band transmitted to the AND circuit. And a forced monaural demodulation means for controlling to a monaural demodulation state.

According to a fourth aspect of the present invention, when the first or second stereo demodulator performs stereo display based on a signal on which stereo demodulation is performed, an output signal selection circuit is provided. When the output from the first stereo demodulator is selected, the second stereo demodulator is forcibly controlled to the monaural demodulation state, and the second stereo demodulator at this time performs stereo demodulation. The stereo display based on the present signal is prevented.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An FM broadcast receiver according to the present invention will be described below with reference to an embodiment. FIG. 1 is a block diagram showing a configuration of an FM receiver according to one embodiment of the present invention.

In the FM broadcast receiver 20 according to one embodiment of the present invention, a signal received by an antenna is supplied to an FM front end 1. Based on the desired broadcast station information given to the system controller 6 via the keyboard 8, a control signal for selecting the broadcast frequency of the desired broadcast station is transmitted to the FM front end 1 by the PLL circuit 7, and the FM front end 1 In the reception, the broadcast of the FM broadcast station is received, converted into an intermediate frequency signal, and transmitted.

The intermediate frequency signal transmitted from the FM front end 1 is supplied to an intermediate frequency (IF) amplification and FM detection stage 2, where it is amplified and FM detected. The FM detection output signal a is supplied to a pilot stereo demodulator 3 which is a first stereo demodulator and a polar stereo demodulator 4 which is a second stereo demodulator, where it is stereo-demodulated and separated into an L signal and an R signal. Is done.

An output signal (L signal and R signal, monaural demodulated signal) from pilot stereo demodulator 3 and an output signal (L signal and R signal, monaural demodulated signal) from polar stereo demodulator 4 are output signal selection circuits. 1
The output signal from the pilot stereo demodulator 3 or the output signal from the polar stereo demodulator 4 is selected and transmitted by the selection of the output signal selection circuit 11.

The detection output from the IF amplification and FM detection stage 2 is also supplied to a tuning detection circuit 5 to extract a signal based on the DC component in the FM detection output a and send a tuning detection signal to a system controller 6. Under the control of the system controller 6, the display unit 9 performs tuning display based on the tuning detection signal.

The pilot stereo demodulator 3 sends out a low-potential demodulation identification signal from a terminal s1 when the FM detection output signal a includes a pilot signal of 19 kHz.
The polar stereo demodulator 4 sends out a low-potential demodulation identification signal from the terminal s3 when the FM detection output signal a includes a subcarrier.

Terminals s1 of the pilot stereo demodulator 3 and a terminal s3 of the polar stereo demodulator 4 are respectively connected to the cathodes of diodes 12 and 13 whose anodes are commonly connected.
3 constitutes an OR circuit, and a diode 1 connected in common
The outputs from the anodes of 2 and 13 are supplied to the system controller 6, and the system controller 6 recognizes that the stereo demodulation is being performed when the anode potential becomes low. The anode potential is shown as stereo identification signal b.

The pilot stereo demodulator 3 and the polar stereo demodulator 4 are respectively provided with forced monaural terminals s2 and s4, and forced monaural terminals s2 and s4 are forcibly applied to the monaural terminals by applying a low potential. It is configured to be controllable to the demodulation state. The forcible monaural terminals s2 and s4 are respectively connected to the anodes of diodes 14 and 15 whose cathodes are connected in common. The forcible monaural signal e output from the system controller 6 is supplied to the cathodes of the diodes 14 and 15. , The pilot stereo demodulator 3 and the polar stereo demodulator 4 are forcibly controlled to a monaural demodulation state.

The output of the terminal s3 of the polar stereo demodulator 4 is supplied to a detection circuit 10 for stereo demodulation detection, and the detection circuit 10 inverts the polarity of the input signal to output a stereo demodulation detection signal c. To output the signal as one input signal to an AND gate circuit 17 for switching the output signal selection circuit 11.

The output signal selection circuit 11 receives the output signal from the AND gate circuit 17 as a selection control signal f. When the selection control signal f is at a low potential, it is switched to the contact position shown in FIG. Is selected when the selection control signal f is at a high potential.
And the output signal from the polar stereo demodulator 3 is selected.

The system controller 6 includes a keyboard 8
, And transmits a control signal for selecting a broadcast frequency of the desired broadcast station to the PLL circuit 7 and identifies a receive frequency band from the broadcast frequency of the desired broadcast station to identify a designated band. The signal d is sent to the AND gate circuit 17 as the other input signal, and a forced monaural signal e is sent out in response to a forced monaural instruction from the keyboard 8 to force the pilot stereo demodulator 3 and the polar stereo demodulator 4. Control to the monaural demodulation state. The designated band identification signal d is output at a high potential only when the reception frequency band is 65 to 74 MHz.

Here, the designated band identification signal d output from the system controller 6 corresponds to a signal corresponding to the first or second broadcast frequency band including the reception frequency selected for broadcast reception, The stereo identification signal c output from the detection circuit 10 corresponds to a signal indicating that the second stereo demodulator performs stereo demodulation, and the AND gate circuit 17 includes the reception frequency selected for broadcast reception. And a signal indicating that the second stereo demodulator performs stereo demodulation and a signal corresponding to the first or second broadcast frequency band.

The system controller 6 receives the tuning detection signal from the tuning detecting circuit 5 and causes the display 9 to perform tuning display, and also receives the stereo identification signal b and performs stereo demodulation on the display 9 at the time of stereo demodulation. Display that there is something. Note that the anode of the diode 16 is connected to the forced monaural terminal s4 of the polar stereo demodulator 4, and the cathode of the diode 16 is connected to the designated band identification signal terminal of the system controller 6, so that the designated band identification signal d is low. Polar stereo demodulator 4 at potential
Is forcibly controlled to a monaural demodulation state.

Here, the diode 16 is a forced monaural for forcibly controlling the second stereo demodulator to a monaural demodulation state based on a signal corresponding to the first broadcast frequency band sent to the AND operation circuit. It corresponds to demodulation means.

The operation of the FM broadcast receiver 20 according to the embodiment of the present invention configured as described above will be described.

In response to an instruction from the keyboard 8, the FM front end 1 receives the broadcast frequency of the desired broadcast station, converts it into an intermediate frequency signal, amplifies it in the IF amplification and FM detection stage 2, and performs FM detection. You. FM
The detection output signal a is supplied to the pilot stereo demodulator 3 and the polar stereo demodulator 4 to be subjected to stereo demodulation. The demodulated output signal is output through the output signal selection circuit 11. Further, the tuning detection signal detected by the tuning detection circuit 5 is supplied to the system controller 6, and the tuning is displayed on the display 9.

On the other hand, the reception frequency band is identified based on the broadcast frequency of the desired broadcast station indicated by the keyboard 8, and the designated band identification signal d is sent to the AND gate circuit 17. The broadcast frequency of the desired broadcast station is 6
When the frequency is within the range of 5 to 74 MHz, the designated band identification signal d is set to a high potential, and the gate of the AND gate circuit 17 is opened.

Next, the operation in each broadcast reception state will be described based on the state of the stereo demodulation detection signal c, the designated band identification signal d, and the selection control signal f shown in FIG.

(A) In this state, the reception frequency band is 6
When the stereo broadcast of the polar modulation method is received at 5 to 74 MHz, the sub-carrier 31.25 kHz is included in the FM detection output signal a and is stereo-demodulated by the polar stereo demodulator 4. The terminal s3 is at a low potential, and the stereo identification signal b is at a low potential. This is detected by the system controller 6 and stereo display is performed on the display 9. The pilot stereo demodulator 3 does not function as a stereo demodulator because the pilot signal 19 kHz is not input. On the other hand, the stereo demodulation detection signal c output from the detection circuit 10 has a high potential, the selection control signal f output from the AND gate circuit 17 has a high potential, and the output signal selection circuit 11 switches from the position shown in FIG. Then, the stereo demodulated output from the polar stereo demodulator 4 is transmitted from the output signal selection circuit 11.

(B) The receiving frequency band is 65 to 74 MHz.
In the case of receiving a monaural broadcast with the polar modulation method, the terminal s3 of the polar stereo demodulator 4 does not become low potential because the subcarrier 31.25 kHz is not transmitted,
This is detected by the system controller 6 by the stereo identification signal b, and the stereo display on the display 9 is extinguished. Since the terminal s3 does not become low potential, the detection circuit 1
The stereo identification signal c output from 0 has a low potential,
The selection control signal f, which is the output of the AND gate circuit 17, has a low potential, and the output signal selection circuit 11 is switched to the position shown in FIG. 1 so that the demodulated output from the pilot stereo demodulator 3 is transmitted from the output signal selection circuit 11. Is done. In this case, a monaural output is transmitted from the pilot stereo demodulator 3, and the monaural output is transmitted from the output signal selection circuit 11.

(C) The reception frequency band is 65 to 74 MHz, but when a pilot type stereo broadcast is received, the pilot signal 19 kHz is included in the FM detection output signal a.
z is included, and is demodulated in stereo by the pilot stereo demodulator 3. The terminal s1 is at a low potential, and the stereo identification signal b is at a low potential. This is detected by the system controller 6 and displayed on the display 9 in stereo. Is made. Polar stereo demodulator 4 does not operate because subcarrier 31.25 kHz is not input. Therefore, the stereo demodulation detection signal c output from the detection circuit 10 has a low potential, the selection control signal f output from the AND gate circuit 17 has a low potential, and the output signal selection circuit 11 moves to the position shown in FIG. The output is switched and the stereo demodulated output from pilot stereo demodulator 3 is transmitted from output signal selection circuit 11.

(D) The receiving frequency band is 65 to 74 MHz.
When a monaural broadcast is received while the pilot tone method is used, the pilot signal 19 is included in the FM detection output signal a.
Since no kHz is included, the terminal s1 of the pilot stereo demodulator 3 does not have a low potential. This is detected by the system controller 6 by the stereo identification signal b, and the stereo display on the display 9 is extinguished. Since the terminal s3 of the polar stereo demodulator 4 does not have a low potential, the stereo identification signal c output from the detection circuit 10 has a low potential and the selection control signal f output from the AND gate circuit 17
Is a low potential, the output signal selection circuit 11 is switched to the position shown in FIG. 1, and the demodulated output from the pilot stereo demodulator 3 is transmitted from the output signal selection circuit 11. In this case, a monaural output is transmitted from the pilot stereo demodulator 3, and the monaural output is transmitted from the output signal selection circuit 11.

The receiving frequency band is 87.5-108M.
In Hz, since only the pilot tone stereo broadcast is used, the designated band identification signal d output from the system controller 6 has a low potential, the gate of the AND gate circuit 17 is closed, and the selection output from the AND gate circuit 17 is selected. The control signal f has a low potential and is always controlled by the output signal selection circuit 11 to the position shown in FIG. 1 where the demodulated output from the pilot stereo demodulator 3 is selected.
Therefore, it becomes the same as the above (c) and (d).

In this case, if the reception frequency band is 8
Since there is only stereo broadcast of the pilot tone system at 7.5 to 108 MHz, no demodulation operation in the polar stereo modulator should be performed at all, but external noise (31.
(E.g., 25 kHz component), the terminal s3 of the polar stereo demodulator 4 has a low potential, and the stereo identification signal b has a low potential, even though the demodulation output of monaural broadcasting is selected. It is also conceivable that the stereo display is erroneously lit on the display 9.

Then, using the designated band identification signal d controlled by the desired reception frequency of the system controller 6, the forced monaural signal e is transmitted from the system controller 6 via the diode 16 to the polar stereo demodulator 4.
To force the polar stereo demodulator 4 into a monaural demodulation state. As a result, the terminal s3 does not become low in this case, and erroneous stereo display on the display 9 is prevented.

In the FM broadcast receiver according to the embodiment of the present invention described above, the AND operation of the signal c and the signal d is performed by the AND gate circuit 17, and the output signal selection circuit is operated by the AND operation output. Although the switching control of the output signal selecting circuit 11 has been described as an example, the switching control of the output signal selecting circuit 11 may be performed based on only the signal c without the AND gate circuit 17. In this case, when the signal c has a high potential, the output signal selection circuit 11 is switched from the position shown in FIG. 1 and the stereo demodulated output from the polar stereo demodulator 4 is transmitted.

[0041]

According to the FM broadcast receiver of the present invention, a stereo demodulator corresponding to each of the different modulation schemes is mounted in one FM broadcast receiver in the FM broadcast receiver. There is an effect that the output signal is automatically selected and output without providing a switch for the user to switch to the device.

For this reason, the switching is performed manually regardless of whether the first broadcasting frequency band uses one modulation scheme or the same broadcasting frequency band in the other modulation scheme. It is convenient because it can be used without any trouble.

There is also an effect that a stable demodulated output can be obtained in the second broadcast frequency band irrespective of the region in which it is used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an FM broadcast receiver according to one embodiment of the present invention.

FIG. 2 is a diagram showing signal states for explaining the operation of the FM broadcast receiver according to one embodiment of the present invention.

FIG. 3 is a diagram for explaining a difference between a polar modulation method and a pilot tone method.

FIG. 4 is a diagram showing modulation frequency arrays of a polar modulation method and a pilot tone method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 FM front end 2 IF amplification and FM detection stage 3 Pilot stereo demodulator 4 Polar stereo demodulator 5 Tuning detection circuit 6 System controller 7 PLL circuit 8 Keyboard 9 Display 10 Detection circuit 11 Output signal selection circuit 17 AND gate circuit

Claims (4)

[Claims] In an FM broadcast receiver, first and second stereo demodulators each having an FM detection output as an input and corresponding to two different modulation systems, and a second stereo demodulator perform stereo demodulation. Characterized by comprising an output signal selection circuit for selecting one of a demodulated output from the first stereo demodulator and a demodulated output from the second stereo demodulator based on a signal indicating that the signal is present. Receiving machine. 2. An FM broadcast receiver comprising: first and second stereo demodulators each having an FM detection output as input and corresponding to two different modulation schemes; and a reception frequency selected for broadcast reception. First or second included
AND operation means for performing an AND operation on a signal corresponding to the broadcast frequency band and a signal indicating that the second stereo demodulator performs stereo demodulation, and first stereo demodulation based on the AND operation output An FM broadcast receiver comprising: an output signal selection circuit that selects one of a demodulated output from a demodulator and a demodulated output from a second stereo demodulator. 3. The FM broadcast receiver according to claim 1, wherein one of the modulation systems is a pilot tone system, the other is a polar modulation system, and the first stereo demodulator corresponds to the pilot tone system. A FM demodulator, wherein the second demodulator is a stereo demodulator corresponding to a polar modulation scheme. 4. The FM broadcast receiver according to claim 2, wherein the second stereo demodulator is forcibly activated based on a signal corresponding to the first broadcast frequency band transmitted to the AND circuit. Characterized by further comprising a forced monaural demodulation means for controlling to a monaural demodulation state.