JP2005210382A - Am radio receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve sound quality which is offensive to ears, by preventing pulsing noise from being undetected. <P>SOLUTION: When a 1st pulsing noise detector 12 detects pulsing noise at the input of a 1st mixer 3, the 1st pulsing noise detector 12 stops a 2nd mixer 6, so no pulsing noise appears at the output of the 2nd mixer 6 and a 2nd pulsing noise detector 13 does not operate, so that the pulsing noise is removed, by only the 1st pulsing noise detector 12. When the pulsing noise is influenced by a disturbing station signal and the 1st pulsing noise detector 12 does not detect it at the input of the 1st mixer 3, the pulsing noise appears at the output of the 2nd mixer 6, but a 1st band-pass filter 5 limits the band of a received signal, and then the disturbing station signal is attenuated to enable the 2nd pulsing noise detector 13 to perform proper pulsing noise detection without the detection sensitivity becoming reduced, thereby stopping a switching control type intermediate-frequency amplifier 14 for a certain time, only when pulsing noise is generated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an AM radio receiver that detects pulse noise mixed in an AM receiver.

    Conventionally, pulse noise (pulse noise) in an AM radio receiver has been a major problem (see Patent Document 1).

  The pulse noise is mainly generated when a disturbance pulse is superimposed on the antenna. In an AM radio receiver that performs envelope detection, the superimposed disturbance pulse is detected as speech, so that the sound quality is very disturbing. Become.

  In particular, in an in-vehicle AM radio, ignition noise generated from an ignition plug of an engine and disturbance pulses generated by other mechanical operation of the electrical system are superimposed on the antenna, so that the sound is significantly affected.

  Hereinafter, an AM radio receiver that detects pulse noise mixed in a conventional AM receiver will be described with reference to FIG.

  In FIG. 10, the AM radio receiver includes an antenna 1, an RF amplifier 2, a first mixer 3, a local oscillator 4, a first band pass filter 5, a second mixer 6, a crystal oscillator 7, and a second band pass filter 8. , An intermediate frequency amplifier 9, an AM detector 10, an AM detection output terminal 11, and a pulse noise detector 12.

  The operation of the conventional AM radio receiver configured as described above will be described.

  In FIG. 10, a broadcast station signal received by an antenna 1 is amplified by an RF amplifier 2, mixed with a local oscillation signal from a local oscillator 4 by a first mixer 3, and converted into a first intermediate frequency signal. The first intermediate frequency signal is band-limited by the first band pass filter 5, mixed with the crystal oscillation signal from the crystal oscillator 7 by the second mixer 6, and converted into the second intermediate frequency signal. The second intermediate frequency signal is band-limited by the second band pass filter 8, amplified by the intermediate frequency amplifier 9, AM demodulated by the AM detector 10, and output.

On the other hand, the pulse noise detector 12 detects the pulse noise superimposed on the antenna 1 at the input of the first mixer 3 and generates a blank pulse for a certain period of time. The second mixer 6 is stopped. During the period when the second mixer 6 is stopped, there is no pulse noise in the broadcast station signal, so that harsh sound quality is improved.
JP-A-52-27207

  However, in the conventional AM radio receiver configured as shown in FIG. 10, since the pulse noise detection terminal is input to the first mixer 3 which is not subject to band limitation, the interference with intensity is desired together with the desired station signal. When the station signal is input to the antenna 1, there is a problem that the detection sensitivity of the pulse noise is lowered.

  FIG. 11 shows the relationship between the desired station signal, the disturbing station signal, and the pulse noise.

  When the detection sensitivity of the pulse noise is lowered, the audio signal detected by the influence of the pulse noise that has not been detected by the pulse noise detector 12 becomes harsh.

  The present invention solves the above-mentioned conventional problems, and an object thereof is to provide an AM receiver that can improve unpleasant sound quality by preventing undetected pulse noise and performing appropriate detection. .

  In order to solve the conventional problem, the invention according to claim 1 is a first pulse noise detector for detecting pulse noise from an RF signal and removing pulse noise included in the first intermediate frequency signal; A second pulse noise detector is provided for detecting the pulse noise from the second intermediate frequency signal and removing the pulse noise contained in the second intermediate frequency signal.

  The invention described in claim 2 is characterized in that the intermediate frequency amplifier is provided with means for removing the pulse noise included in the intermediate frequency signal in accordance with the output signal from the pulse noise detector.

  According to a third aspect of the present invention, there is provided a first pulse noise detector for detecting pulse noise from an RF signal and removing pulse noise contained in the first intermediate frequency signal, and the pulse characteristic from the second intermediate frequency signal. A second pulse noise detector for detecting noise and removing pulse noise included in the audio signal is provided.

  The invention described in claim 4 is characterized in that the AM detector is provided with means for removing pulse noise contained in the voice signal in accordance with the output signal from the pulse noise detector.

  According to a fifth aspect of the present invention, there is provided a pulse noise detector that detects pulse noise from the first intermediate frequency signal and removes the pulse noise included in the second intermediate frequency signal.

  The invention described in claim 6 is characterized in that the pulse noise detector is provided with a band-pass filter that limits the band of the input signal.

  According to the present invention, the pulse noise included in the second intermediate frequency signal is detected, and the pulse noise detector that stops the intermediate frequency amplifier for a certain period of time prevents undetected pulse noise and performs appropriate detection. By doing so, it is possible to configure an AM receiver that can improve annoying sound quality.

  According to the present invention, the pulse noise included in the second intermediate frequency signal is detected, and the AM noise detector is stopped for a certain period of time, thereby preventing undetected pulse noise and performing appropriate detection. By doing so, it is possible to configure an AM receiver that can improve annoying sound quality.

  According to the present invention, the pulsed noise detector that detects the pulsed noise included in the first intermediate frequency signal and stops the second mixer for a certain period of time prevents undetected pulsed noise and performs appropriate detection. By performing the above, it is possible to configure an AM receiver that can improve annoying sound quality.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same parts as those of the conventional example described with reference to FIG.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an AM radio receiver according to Embodiment 1 of the present invention.

  1, the AM radio receiver according to the first embodiment includes an antenna 1, an RF amplifier 2, a first mixer 3, a local oscillator 4, a first bandpass filter 5, a second mixer 6, a crystal oscillator 7, a first oscillator It comprises a two-band pass filter 8, a switch-controlled intermediate frequency amplifier 14, an AM detector 10, an AM detection output terminal 11, a first pulse noise detector 12, and a second pulse noise detector 13.

  FIG. 2 shows a configuration example of the first pulse noise detector 12 and the second pulse noise detector 13 according to the first embodiment. The resistors R1 to R4, the capacitor C1, the transistors Q1 to Q15, and the constant voltage source V1. , And constant current sources I1 to I4.

  FIG. 3 shows a configuration example of the switch-controlled intermediate frequency amplifier 14 according to the first embodiment, which includes a resistor R5, transistors Q16 to Q27, constant voltage sources V2 and V3, and constant current sources I5 to I6.

  The operation of the AM radio receiver of the first embodiment configured as described above will be described.

  In FIG. 1, a broadcast station signal received by an antenna 1 is amplified by an RF amplifier 2, mixed with a local oscillation signal from a local oscillator 4 by a first mixer 3, and converted into a first intermediate frequency signal. The first intermediate frequency signal is band-limited by the first band pass filter 5, mixed with the crystal oscillation signal from the crystal oscillator 7 by the second mixer 6, and converted into the second intermediate frequency signal. The second intermediate frequency signal is band-limited by the second band pass filter 8, amplified by the switch control type intermediate frequency amplifier 14, AM demodulated by the AM detector 10, and output.

  On the other hand, the first pulse noise detector 12 detects pulse noise at the input of the first mixer 3 and stops the second mixer 6 for a certain time. The second pulse noise detector 13 detects pulse noise from the output of the second mixer 6 and stops the switch-controlled intermediate frequency amplifier 14 for a predetermined time.

  In FIG. 4, when pulse noise higher than the reference voltage V1 is input to the pulse noise detection terminal, the potential at the terminal A is instantaneously lowered due to the pulse noise, and the terminal B has a capacitance C1, resistors R1, R2, and R4. Since the electric potential is lowered due to the time constant determined by (1), a period occurs in which the potential difference between the terminal A and the terminal B is reversed. During this period, the transistor Q15 is turned on, and the constant current source to which Q15 is connected is shut off. Then, the circuit of the next stage is stopped. Normally, the pulse noise is delayed by the second bandpass filter 8 and the pulse noise itself is also expanded. Therefore, the period for stopping the next-stage circuit needs a sufficiently long time without affecting the sound quality. And

  FIG. 4 shows the above relationship in the second pulse noise detector 13.

  In FIG. 3, the received signal applied to the input is amplified with a gain determined by (R5 · I5) / Vt (≈26 mV) and output through the buffer circuit. A transistor switch is added to the current source of the buffer circuit, and the reception signal is not output only when the transistor switch is ON.

  Next, the operation of the AM radio receiver according to Embodiment 1 in a state where pulse noise is superimposed on the antenna will be described.

  When pulsed noise superimposed on the antenna 1 is detected by the first pulsed noise detector 12 at the input of the first mixer 3, the first pulsed noise detector 12 stops the second mixer 6. Therefore, there is no pulse noise in the output of the second mixer 6, the second pulse noise detector 13 does not operate, and the pulse noise is removed only by the first pulse noise detector 12.

  On the other hand, if the pulse noise superimposed on the antenna 1 is affected by the disturbing station signal and is not detected by the first pulse noise detector 12 at the input of the first mixer 3, the output of the second mixer 6 is output. There is pulse noise. However, since the band limitation is applied to the received signal by the first band-pass filter 5, the jamming station signal is attenuated, and the second pulse noise detector 13 performs appropriate pulse noise detection without lowering the detection sensitivity. Since the switch-controlled intermediate frequency amplifier 14 is stopped for a certain time only when pulse noise is generated, annoying sound due to the pulse noise is not output to the audio signal output terminal.

  In the AM radio receiver according to the first embodiment, the pulse noise is detected by the pulse noise detector that detects the pulse noise included in the second intermediate frequency signal using the above characteristics and stops the intermediate frequency amplifier for a predetermined time. By preventing undetection and performing appropriate detection, an AM receiver that can improve annoying sound quality can be realized.

(Embodiment 2)
FIG. 5 is a block diagram showing a configuration of an AM radio receiver according to Embodiment 2 of the present invention.

  In FIG. 5, the AM radio receiver according to the second embodiment includes an antenna 1, an RF amplifier 2, a first mixer 3, a local oscillator 4, a first bandpass filter 5, a second mixer 6, a crystal oscillator 7, and a first oscillator. It comprises a two-band pass filter 8, an intermediate frequency amplifier 9, a switch control type AM detector 15, an AM detection output terminal 11, a first pulse noise detector 12 and a second pulse noise detector 13.

  FIG. 6 shows a configuration example of the switch control type AM detector 15 according to the second embodiment, which includes resistors R6 to R10, transistors Q28 to Q38, a constant voltage source V5, and constant current sources I7 to I10.

  The operation of the AM radio receiver configured as described above according to the second embodiment will be described.

  In FIG. 5, a broadcast station signal received by an antenna 1 is amplified by an RF amplifier 2, mixed with a local oscillation signal from a local oscillator 4 by a first mixer 3, and converted into a first intermediate frequency signal. The first intermediate frequency signal is band-limited by the first band pass filter 5, mixed with the crystal oscillation signal from the crystal oscillator 7 by the second mixer 6, and converted into the second intermediate frequency signal. The second intermediate frequency signal is band-limited by the second band pass filter 8, amplified by the intermediate frequency amplifier 9, AM demodulated by the switch control type AM detector 15, and output.

  On the other hand, the first pulse noise detector 12 detects pulse noise at the input of the first mixer 3 and stops the second mixer 6 for a certain time. The second pulse noise detector 13 detects pulse noise from the output of the second mixer 6 and stops the switch-controlled AM detector 15 for a certain time. Since the operations of the first pulse noise detector 12 and the second pulse noise detector 13 are the same as those in the first embodiment, a description thereof will be omitted.

  In FIG. 6, when the transistor switch of the pulse noise detection circuit is in an OFF state, and there is a relationship of resistors R8> R6, R7 = R9, and the potential of the terminal C is set higher than the potential of the terminal D. The intermediate frequency signal applied to the intermediate frequency signal input terminal is envelope-detected by the capacitor C2, and is output to the audio signal output terminal through the buffer circuit.

  Here, when the transistor switch of the pulse noise detection circuit is turned on, the buffer circuit does not operate and the terminal E becomes high impedance, so that the signal held by the capacitor C3 is output to the audio signal output terminal.

  Next, the operation of the AM radio receiver according to the second embodiment in a state where pulse noise is superimposed on the antenna will be described.

  When the pulsed noise superimposed on the antenna is detected by the first pulsed noise detector 12 at the input of the first mixer 3, the first pulsed noise detector 12 stops the second mixer 6. The pulse noise is not present in the output of the second mixer 6, the second pulse noise detector 13 does not operate, and the pulse noise is removed only by the first pulse noise detector 12.

  On the other hand, if the pulse noise superimposed on the antenna 1 is affected by the disturbing station signal and is not detected by the first pulse noise detector 12 at the input of the first mixer 3, the output of the second mixer 6 is output. There is pulse noise. However, since the band limitation is applied to the received signal by the first band-pass filter 5, the jamming station signal is attenuated, and the second pulse noise detector 13 performs appropriate pulse noise detection without lowering the detection sensitivity. Only when pulse noise occurs, the switch-controlled AM detector 15 holds the signal for a certain period of time, so that annoying sound due to the pulse noise is not output to the audio signal output terminal.

  In the AM radio receiver according to the second embodiment, the pulse characteristic is detected by the pulse noise detector that detects the pulse noise included in the second intermediate frequency signal using the above characteristics and holds the AM detector output signal for a certain period of time. By preventing undetected noise and performing appropriate detection, an AM receiver that can improve annoying sound quality can be realized.

(Embodiment 3)
FIG. 7 is a block diagram showing a configuration of an AM radio receiver according to Embodiment 3 of the present invention.

  In FIG. 7, the AM radio receiver according to the third embodiment includes an antenna 1, an RF amplifier 2, a first mixer 3, a local oscillator 4, a first bandpass filter 5, a second mixer 6, a crystal oscillator 7, a first oscillator. It comprises a two-band pass filter 8, an intermediate frequency amplifier 9, an AM detector 10, an AM detection output terminal 11, and a band-limited pulse noise detector 16.

  FIG. 8 shows a configuration example of the band-limited pulse noise detector 16, which is composed of resistors R11 to R12, capacitors C4 and C5, buffer circuits B1 and B2, and the pulse noise detector shown in FIG. The

  The operation of the AM radio receiver of the third embodiment configured as above will be described.

  In FIG. 7, a broadcast station signal received by an antenna 1 is amplified by an RF amplifier 2, mixed with a local oscillation signal from a local oscillator 4 by a first mixer 3, and converted into a first intermediate frequency signal. The first intermediate frequency signal is band-limited by the first band pass filter 5, mixed with the crystal oscillation signal from the crystal oscillator 7 by the second mixer 6, and converted into the second intermediate frequency signal. The second intermediate frequency signal is band-limited by the second band pass filter 8, amplified by the intermediate frequency amplifier 9, AM demodulated by the AM detector 10, and output.

  On the other hand, the band-limited pulse noise detector 16 detects pulse noise from the output of the first mixer 3 and stops the second mixer 6 for a certain time.

  In FIG. 8, at the band-limited pulse noise detector input, the pulse noise superimposed on the first intermediate frequency signal is detected. Here, a band-pass filter that passes only frequencies near the first intermediate frequency signal determined by cutoff frequencies 1 / (2π · C4 · R11) and 1 / (2π · C5 · R12) is shown in FIG. The signal is transmitted to the pulsed noise detector shown.

  FIG. 9 shows frequency characteristics at the terminal F of the band-limited pulse noise detector shown in FIG. Since the operation of the pulse noise detector shown in FIG. 2 is the same as that of the first embodiment, the description thereof is omitted.

  Next, the operation of the AM radio receiver according to the third embodiment in a state where pulse noise is superimposed on the antenna will be described.

  When the pulse noise superimposed on the antenna 1 is input to the band limited pulse noise detector 16 together with the received signal, the band limitation is applied by the band pass filter of the band limited pulse noise detector 16, so that the disturbing station The signal is attenuated, and the band-limited pulse noise detector 16 can perform appropriate pulse noise detection without lowering the detection sensitivity due to the influence of the interfering station signal, and only when pulse noise occurs. Since the second mixer is stopped for a certain period of time, annoying sound due to pulse noise is not output to the audio signal output terminal.

  In the AM radio receiver according to the third embodiment, the pulse noise is detected by the pulse noise detector that detects the pulse noise included in the first intermediate frequency signal using the above characteristics and stops the second mixer for a predetermined time. An AM receiver that can improve an unpleasant sound quality can be realized by preventing undetected noise and performing appropriate detection.

  The present invention is applied to an AM radio receiver that detects pulsed noise mixed in an AM receiver, and in particular, prevents undetected pulsed noise and performs appropriate detection, thereby harsh sound quality. It is effective for use in an AM radio receiver that improves the frequency.

FIG. 1 is a block diagram showing a configuration of an AM radio receiver according to Embodiment 1 of the present invention. The circuit diagram which shows the structural example of the pulse noise detector in Embodiment 1 and Embodiment 2 FIG. 2 is a circuit diagram showing a configuration example of a switch control type intermediate frequency amplifier according to the first embodiment. The figure which shows the relationship of the electric potential of the terminal A and the terminal B of the pulse noise detector shown in FIG. Block diagram showing a configuration of an AM radio receiver according to Embodiment 2 of the present invention Circuit diagram showing a configuration example of a switch control type AM detector in the second embodiment Block diagram showing a configuration of an AM radio receiver according to Embodiment 3 of the present invention Circuit diagram showing a configuration example of a band-limited pulse noise detector in the third embodiment The figure which shows the frequency characteristic of the bandpass filter of the band-limited type pulse noise detector shown in FIG. Block diagram showing the configuration of a conventional AM radio receiver Diagram showing relationship between desired station signal, jamming station signal and pulse noise

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 RF amplifier 3 1st mixer 4 Local oscillator 5 1st band pass filter 6 2nd mixer 7 Crystal oscillator 8 2nd band pass filter 9 Intermediate frequency amplifier 10 AM detector 11 AM detector output terminal 12 1st One-pulse noise detector 13 Second pulse-noise detector 14 Switch-controlled intermediate frequency amplifier 15 Switch-controlled AM detector 16 Band-limited pulse-noise detector

Claims (6)

An AM radio receiver that performs band limitation on a first intermediate frequency signal and a second intermediate frequency signal in an AM receiving circuit that receives a broadcast station signal, demodulates and outputs the AM signal,
A first pulse noise detector that detects pulse noise from an RF signal and removes the pulse noise included in the first intermediate frequency signal; detects the pulse noise from the second intermediate frequency signal; An AM radio receiver comprising: a second pulse noise detector for removing pulse noise included in the second intermediate frequency signal.   2. An AM radio receiver according to claim 1, wherein said intermediate frequency amplifier comprises means for removing pulse noise contained in said intermediate frequency signal in accordance with an output signal from said pulse noise detector. . An AM radio receiver that performs band limitation on a first intermediate frequency signal and a second intermediate frequency signal in an AM receiving circuit that receives a broadcast station signal, demodulates and outputs the AM signal,
A first pulse noise detector that detects pulse noise from the RF signal and removes the pulse noise included in the first intermediate frequency signal; detects the pulse noise from the second intermediate frequency signal; An AM radio receiver comprising a second pulse noise detector for removing pulse noise contained in a signal.   4. The AM radio receiver according to claim 3, wherein the AM detector is provided with means for removing pulse noise contained in a voice signal in accordance with an output signal from the pulse noise detector. An AM radio receiver that performs band limitation on a first intermediate frequency signal and a second intermediate frequency signal in an AM receiving circuit that receives a broadcast station signal, demodulates and outputs the AM signal,
An AM radio receiver comprising a pulse noise detector that detects pulse noise from the first intermediate frequency signal and removes pulse noise contained in the second intermediate frequency signal.   6. The AM radio receiver according to claim 5, wherein the pulse noise detector is provided with a band-pass filter that limits a band on an input signal.

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