JPS5919494B2 - fm radio receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an FM radio receiver having a tuner for receiving FM radio broadcast waves.

If the tuner of an FM radio receiver having a tuner for receiving FM broadcast waves is receiving desired FM radio broadcast waves (hereinafter referred to as desired FM radio broadcast waves), the desired FM radio broadcast. If there is another FM radio broadcast wave (hereinafter referred to as undesired FM radio broadcast wave) having a carrier frequency close to the carrier frequency of the wave, the output obtained from the demodulation system will be based on the undesired FM radio broadcast wave. It is affected by the output and has a sag that results in deterioration of quality.

However, if the output obtained from the demodulation system is affected by undesired FM radio broadcast waves and the quality is degraded,
The output obtained from the demodulation system includes, in addition to the components of the desired band based on the desired FM radio broadcast waves, the difference between the carrier intermediate frequencies of the desired FM radio broadcast waves and the undesired FM radio broadcast waves, and the respective components of both FM radio broadcast waves. The unwanted band components determined by the shift frequency are accompanied by interference waves.

For example, the difference in the carrier center frequencies of the desired FM radio broadcast wave and the undesired FM radio broadcast wave is 300 KHz, and
The maximum deviation frequency for each M radio broadcast wave is 75KH
Z, then the minimum fundamental frequency of the output obtained from the demodulation system is 150KHz (=(300-2×75)
KHZ), and the maximum fundamental frequency is 450KHZ (1 (3
00+2×75)KHZ) is accompanied as an interference wave by an undesired band component. Traditionally, based on the
The above-mentioned undesired band component is obtained from the output obtained from the demodulation system, and if the undesired band component exhibits a level higher than the expected level based on this undesired band component, an output representing this is obtained as the interference wave detection output, and A method has been proposed in which an intermediate frequency transmission system is controlled so that its transmission bandwidth is narrowed based on the interference wave detection output of the lever.

However, in the case of such a method, the relationship that an undesired FM radio broadcast wave exists in the vicinity of a desired FM radio broadcast wave means that other FM radio broadcast waves other than the desired FM radio broadcast wave are treated as new desired FM radio broadcast waves. In this case, as long as there is no new undesired FM radio broadcast wave in the vicinity of the new desired FM radio broadcast wave, reception will continue, so based on the interference wave detection output, the intermediate frequency If the transmission bandwidth of the transmission system is controlled to be narrowed, the interference wave detection output disappears, the transmission bandwidth of the intermediate frequency transmission system returns to the original transmission bandwidth, and when it returns like this, the interference wave detection output If this is obtained, the transmission bandwidth of the intermediate frequency transmission system is controlled to be narrowed again, and the same operation is repeated as long as there are undesired FM radio broadcast waves in the vicinity of the desired FM radio broadcast waves.

On the other hand, it cannot be denied that there is a time delay until the interference wave detection output is obtained from the output obtained from the demodulation system and until the transmission bandwidth of the intermediate frequency transmission system is controlled based on the interference wave detection output. In the case of the method described above, the output obtained from the time-length demodulation system according to the delay time described above is affected by the undesired FM radio broadcast waves for each repetition described above,
Therefore, although it is possible to obtain the effect that the output obtained from the demodulation system is not affected by undesired FM radio broadcast waves and deteriorate in quality, the effect is not sufficiently satisfactory. What you get is indescribable.

For this purpose, conventionally, a cascade connection circuit is provided for an interfering wave intermediate frequency transmission system to which the output obtained from the tuner is supplied and an interfering wave demodulation system to which the output obtained from the interfering wave demodulation system is supplied. There is also a method in which the undesired band components are obtained, the interference wave detection output described above is obtained based on this, and the transmission bandwidth of the originally existing intermediate frequency transmission system is controlled by the interference wave detection output as described above. Proposed. However, although such a method can avoid the disadvantages of the above-mentioned method, it requires special installation of an intermediate frequency transmission system for interfering waves and a demodulation system for interfering waves, and the receiver as a whole becomes complicated, large, and It has the disadvantage of being expensive.

In addition, in any of the above-mentioned methods, since the shift frequencies of the desired FM radio broadcast waves and the undesired FM radio broadcast waves change from time to time irrespective of each other, the level of the above-mentioned undesired band components sometimes changes. Therefore, depending on the change in the level of the undesired band component, the above-mentioned interference wave detection output may or may not be obtained, and the transmission bandwidth of the intermediate frequency transmission system may not be controlled. It is something that is repeated.

On the other hand, as mentioned above, it is undeniable that there is a time delay until the interference wave detection output is obtained from the output obtained from the demodulation system and until the transmission bandwidth of the intermediate frequency transmission system is controlled based on the interference wave detection output. It is something. Therefore, in any of the above-mentioned methods, the output obtained from the time-length demodulation system corresponding to the above-mentioned delay time for each repetition is undesired FM.
As mentioned above, the output obtained from the demodulation system is not influenced by undesired FM radio broadcast waves and the quality of the output is not deteriorated. However, the effects cannot be said to be fully satisfactory.

Therefore, an example of the present invention can be sufficiently satisfied without the above-mentioned drawbacks, in that the output obtained from the demodulation system is not affected by undesired FM radio broadcast waves and is not obtained as a result of quality deterioration. The purpose is to propose a new FM radio receiver that can be used as a practical product.
It will become clear from the following detailed description of an example of the present invention with reference to the drawings.

1 in the figure shows a normal tuner that receives FM radio broadcast waves, and the output S1 from this tuner is a wideband intermediate frequency transmission system 2A having a relatively wide transmission bandwidth and a narrowband intermediate frequency transmission system 2A having a relatively narrow transmission bandwidth. The signal is supplied to the transmission system 2B.

In this case, transmission systems 2A and 2B are connected to their respective power supply terminals 3A.
It is assumed that the operating state is obtained only when the required power supplies VA and VB are supplied to 3B and 3B, as described later. Also, the intermediate frequency outputs SA and SB obtained from the transmission systems 2A and 2B are selectively supplied to a common demodulation system 4 as described below, while the audio output SS obtained from the demodulation system 4 is supplied to the speaker 5. The signal is supplied to the interference wave transmission system 6.

In this case, the demodulation system 4 obtains an output depending on whether the FM radio broadcast waves received internally by the tuner 1 are in stereo mode or monaural mode as usual, so the tuner 1 receives the waves based on the output. If the FM radio broadcast wave is in stereo mode, the output will be "1" in binary display, and if it is in monaural mode, it will be "O".Whether the output is when the FM radio broadcast wave is received in stereo mode or is received in monaural mode. The output G is obtained as an output G when the output voltage is 0. In addition, the transmission system 6 is configured to transmit undesired band components in the audio output SS as interference waves, so that the undesired FM radio broadcasts are added to the desired FM radio broadcast waves being received by the tuner 1. It is assumed that there may be a relationship in which the waves exist close to each other with a difference in carrier center frequency of both broadcast waves of, for example, a minimum of 300 KHz,
Also, if the maximum deviation frequency of both broadcast waves is 75KHZ, then 150KHZ (= (300-2X75)KH
Z) ~450KHZ (=(300+2X75)KHZ)
For example, a filter 8 of such a band is used to transmit components of a band of
The output G obtained from the terminal 7 of the demodulation system 4 mentioned above is supplied via the terminal 9, and when the output G is "1", the transmission gain of this transmission system 6 is the output G. For example, it is configured to include a voltage control cape amplifier 10 in order to increase the voltage compared to the case where the voltage is "O". Further, an output N as an interference wave obtained from the transmission system 6 is supplied to an interference wave detection circuit 11.

This detection circuit 11 has a rectifier circuit 12 that converts the output N into a direct current, and a threshold circuit 13 to which the output E is supplied. "O" in binary display, "1" if not displayed
An output is obtained, which is derived as the output Q of the interference wave detection circuit 11. Also, the detection circuit 11
The interference wave detection output Q obtained from the above is supplied to the control holding means 14.

This control holding means 14 is required only at the terminal 3A of the transmission system 2A in order to keep the above-mentioned wideband intermediate frequency transmission system 2A in the operating state and the narrowband intermediate frequency transmission system 2B in the inactive state when the output Q is "1". However, if the output Q becomes "0" from this state, the required power supply VB is applied only to the terminal 3B of the transmission system 2B in order to make the transmission system 2A inactive and the transmission system 2B in the active state. The power supply circuit 15A connected between the power supply terminal VO and the terminal 3A of the transmission system 2A, and the power supply terminal A power supply circuit 15B connected between the VO and the terminal 3B of the transmission system 2B, and a power supply circuit 15C connected between its output terminal, that is, the terminal 3B, and the output terminal of the rectifier circuit 12 of the interference wave detection circuit 11 described above. It becomes more. In this case, the power supply circuit 15B has, for example, a collector connected to the terminal VO, an emitter connected to the terminal 3B, a base connected to the terminal 0 via the bias resistor 16, and a charging capacitor 17.
NPN for switching connected to ground through
type transistor M1, a switching NPN type transistor whose collector is connected to the side opposite to the ground side of the capacitor 17, whose emitter is connected to the ground, and whose base receives the output Q from the above-mentioned interference wave detection circuit 11. M2
For example, the power supply circuit 15A has a collector connected to the terminal VO, an emitter connected to the terminal 3A, and a base connected to the terminal VO via the bias resistor 18.
and a switching NPN transistor M3 connected to the ground through the charging capacitor 19.
and the collector is on the side opposite to the ground side of the capacitor 19,
The emitter is grounded, and the base is the power supply circuit 15 described above.
For example, the power supply circuit 15C has an anode and a cathode connected to the output end of the power supply circuit 15B, that is, the terminal 3B. It is constructed with a diode 21 as a unidirectional element connected to the output terminal of the rectifier circuit 12 of the interference wave detection circuit 11 via a resistor 20 as necessary.
When the output Q of is "1", the transistor M2 of the power supply circuit 15B is turned on, and therefore the transistor M1 is turned off.Therefore, the output terminal of the circuit 15B cannot receive power based on the power obtained from the power supply terminal VO. , therefore, the power supply V is connected to terminal 3B.
Since B is not supplied and the power supply B cannot be obtained to the circuit 15B, the transistor M4 of the power supply circuit 15A is turned off, and therefore the transistor M3 is turned on, so that the output terminal of the circuit 15A receives the power obtained from the power supply terminal VO. Therefore, the power supply VA is supplied to the terminal 3A. However, if the output Q becomes "0" from this state, the transistor M2 is turned off, so the transistor M1 is turned on, and the power supply VB is supplied to the terminal 3B. Since the power source VB is obtained, the transistor M4 is turned on, and therefore the transistor M3 is turned off, so that the power source VA is not supplied to the terminal 3A.On the other hand, since the power source VB is obtained, the transistor M4 is turned on, and the transistor M3 is turned off. is supplied to the output terminal of the rectifier circuit 12 of the interference wave detection circuit 11 through the output terminal, and therefore, if the output Q becomes "0", the output Q will remain "0" even if the output N of the interference wave transmission system 6 disappears.
In other words, the power supply VA is not supplied to the terminal 3A, but the state in which the power supply VB is supplied to the terminal 3B is maintained. Furthermore, the audio output SS obtained from the demodulation system 4 mentioned above is supplied to the canceling means 25.

This release means 25 is configured to release the above-mentioned control holding means 14 from controlling and holding the transmission system 2A in an inoperable state and the transmission system 2B in an operating state. A delay circuit 26 configured with a time constant circuit having a relatively large time constant but a relatively small discharge time constant, and a binary display when the output is supplied and the level exceeds the expected level. A threshold circuit 27 configured to obtain an output that is "0" and "1" otherwise, and the output terminal of the rectifier circuit 12 of the above-mentioned interference wave detection circuit 11 that is turned on when the output is "1" and grounded. It is configured with a switching transistor 29 connected via a resistor 28 as necessary between the two FM radio broadcast waves. Based on the fact that the output SS of the demodulation system 4 is substantially eliminated when the operation is performed for reception, the input to the threshold circuit 13 of the interference wave detection circuit 11 is eliminated, and therefore the output Q is obtained as "1", As a result, the control holding circuit 14 obtains the power supply VA instead of the power supply VB to release the above-mentioned control holding state. The above is an example of the configuration of the FM radio receiver according to the present invention. According to this configuration, as is clear from the above, when the tuner 1 is operating to select a desired FM radio broadcast wave, The output Q of the interference wave detection circuit 11 is "1", and therefore only the power supply VA is obtained from the control holding circuit 14, and the wideband intermediate frequency transmission system 2At) 3 is in the operating state, and the narrowband intermediate frequency transmission system 2B is disabled. In this state, the tuner 1 is in a state where it can receive the desired FM radio broadcast wave, and in this case, if there is an undesired FM radio broadcast wave that is close to the desired FM radio broadcast wave, then The output SS obtained by the demodulation system 4 through the wideband intermediate frequency transmission system 2A is obtained as accompanied by an undesired band component, and therefore the output N is obtained from the interference wave transmission system 6, and the output N is the expected one. If the level is higher than the level of , the output SS obtained by the demodulation system 4 will be obtained with undesired band components to such an extent that they cannot be ignored.

However, in this case, the output of the interference wave detection circuit 11 becomes "1", and the power supply VB is obtained in place of the power supply VA in the control cape holding circuit 14, so that the wideband intermediate frequency transmission system 2A becomes inoperable and the narrowband intermediate frequency transmission system 2B is in the operating state, and therefore the output SS of the demodulation system 4 is obtained as having no undesired band components, or even if it is accompanied by them, only to a negligible extent, and such a state is when control is maintained. By means of the means 14, even if the level of the undesired band component changes afterwards, it is maintained and the follow-up signal is maintained as long as the tuner 1 is not operated to transmit or receive other desired FM radio broadcast waves. Therefore, the effect that the output SS obtained from the demodulation system 4 is not deteriorated in quality due to the influence of undesired FM radio broadcast waves can be obtained satisfactorily, and such excellent effects can be obtained, for example. It has the great feature that it can be obtained with a simple structure as a whole, such as being able to obtain it without special installation of a demodulation system for interference waves. Furthermore, when the desired FM radio broadcast waves are received in stereo mode, the output SS obtained from the demodulation system 4 has a wider bandwidth than when the FM radio broadcast waves are received in monaural mode, so that undesired FM Although it is easily influenced by radio broadcast waves, in the case of the FM radio receiver according to the present invention described above, when the tuner 1 receives the FM radio broadcast waves in stereo mode, the output G obtained from the demodulation system 4 The transmission gain of the base interference wave transmission system 6 is improved, and as a result, the interference wave output N and therefore the output Q "O" can be obtained with high sensitivity, so even when receiving FM radio broadcast waves in stereo mode, the above-mentioned It also has the characteristics of being able to satisfactorily obtain excellent effects.

The above description is merely an example of the present invention, and for example, the wideband intermediate frequency transmission system 2A and the narrowband intermediate frequency transmission system 2A.
The output of B is selectively supplied to the demodulation system 4 via a changeover switch, and the changeover switch in this case is connected to either or both of the power sources VA and VB selectively obtained from the control holding means 14. In this case, in terms of the configuration of the wideband intermediate frequency transmission system 2A and the narrowband intermediate frequency transmission system 2B, including the changeover switch, the system should be configured to be in the above-mentioned operating or inoperable state. It is also possible to make various other modifications without departing from the spirit of the invention.

[Brief explanation of the drawing]

The figure is a system diagram showing an example of an FM radio receiver to which the present invention is applied. In the figure, 1 is a tuner, 2A is a broadband intermediate frequency transmission system, and 2B
is a narrowband intermediate frequency transmission system, 4 is a demodulation system, 5 is a speaker,
Reference numeral 6 indicates an interference wave transmission system, 11 an interference wave detection circuit, 14 a suppression holding means, and 25 a release means.

Claims (1)

[Claims] 1. In a receiver having a tuner for receiving FM radio broadcast waves, a wideband intermediate frequency transmission system and a narrowband intermediate frequency transmission system to which the output is supplied from the tuner, and the broadband intermediate frequency transmission system and the narrowband intermediate frequency A common demodulation system for the broadband intermediate frequency transmission system and the narrowband intermediate frequency transmission system to which the output from the transmission system is supplied, and when the output from the demodulation system is supplied and it contains undesired band components. An interference wave transmission system that transmits the interference wave as an interference wave, and an output from the interference wave transmission system is supplied, and when the output from the interference wave transmission system exhibits a level higher than a predetermined level, an output indicating this is obtained as an interference wave detection output. an interference wave detection circuit, and the interference wave detection output obtained from the interference wave detection circuit is supplied, and based on the interference wave detection output, the wideband intermediate frequency transmission system is controlled to be inactive, the narrowband intermediate frequency transmission system is controlled to be in operation; control holding means for maintaining the control state even if the disturbance wave detection output disappears after cocooning; means for releasing the control state by the control holding means; and means for controlling the FM according to whether the FM is being received in stereo mode or in monaural mode.
radio receiver.