CN2475231Y - FM broadcast receiver - Google Patents
FM broadcast receiver Download PDFInfo
- Publication number
- CN2475231Y CN2475231Y CN 01211149 CN01211149U CN2475231Y CN 2475231 Y CN2475231 Y CN 2475231Y CN 01211149 CN01211149 CN 01211149 CN 01211149 U CN01211149 U CN 01211149U CN 2475231 Y CN2475231 Y CN 2475231Y
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- China
- Prior art keywords
- circuit
- signal
- control circuit
- power amplifier
- squelch
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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- 239000002131 composite material Substances 0.000 claims abstract description 6
- 230000035945 sensitivity Effects 0.000 abstract description 3
- 230000007613 environmental effect Effects 0.000 abstract 1
- 238000007599 discharging Methods 0.000 description 5
- 230000030279 gene silencing Effects 0.000 description 5
- 239000003990 capacitor Substances 0.000 description 3
- 238000004891 communication Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000005236 sound signal Effects 0.000 description 3
- 230000008030 elimination Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
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- Stereo-Broadcasting Methods (AREA)
- Noise Elimination (AREA)
Abstract
The utility model discloses a frequency modulation broadcast receiver, including box, loudspeaker and receiving demodulation circuit, squelch control circuit and power amplifier circuit, receive demodulation circuit and squelch control circuit and be connected, squelch control circuit and power amplifier circuit are connected, and power amplifier circuit is connected with loudspeaker, receives demodulation circuit output composite signal and pilot frequency identification circuit and is connected, and pilot frequency identification circuit output identification signal controls squelch control circuit. The squelch circuit is controlled by identifying whether a 19KHz pilot signal exists or not, and the squelch circuit has the characteristics of small environmental influence, strong anti-interference performance, stable receiving, high sensitivity, reliable squelch function and the like.
Description
The utility model relates to a kind of broadcasting receiver, particularly a kind of fm broadcast receiver that receives fm broadcast signal.
Along with developing rapidly of cable TV cause, cable TV network has spread all over town and country, and the FM broadcasting of a kind of new broadcasting delivery form-transmit in cable TV network produces thereupon.When wired TV network when receiver user or audio amplifier are carried a fm broadcast signal, receiver user can be emitted sound automatically, after off-the-air is turned off fm broadcast signal, receiver user transfers the state of listening to of waiting for automatically to, do not emit sound, this just needs receiver to possess the automatic silencing function.The automatic silencing function of fm broadcast receiver in the market all is to rely on the squelch circuit that designs in the receiving integrate circuit to realize.Because the signal level in the cable TV network comprises that the fm broadcast signal level can change with variation of ambient temperature, and produce the intermodulation composition and make FM receiver automatic silencing functional failure, and indexs such as level fluctuation and intermodulation ratio become bad with the prolongation of cable TV main line.Though each producer updates, prevent the noise elimination functional failure by the unblocked level threshold values of regulating FM receiver, but brought the contradiction that FM receiver can not be opened.These contradictions have limited the scope of application of FM broadcasting in cable TV network, have restricted the development of radio and television services.
For overcoming the problem of above-mentioned existence, the purpose of this utility model is to provide that a kind of little, strong anti-interference performance affected by environment, reception are stable, automatic silencing reliable in function, receiving sensitivity height, does not hinder the fm broadcast receiver of the auxiliary communication broadcasting service of FM broadcasting again.
For achieving the above object, a kind of fm broadcast receiver of the present utility model, comprise casing, be fixed on loudspeaker and receiving demodulation circuit, mute control circuit and power amplifier on the casing, the output of receiving demodulation circuit audio frequency is connected with mute control circuit, the output of mute control circuit signal is connected with power amplifier, the power amplifier signal outputs to loudspeaker, described receiving demodulation circuit output composite signal is connected with the pilot tone identification circuit, pilot tone identification circuit output identification signal control mute control circuit.
Described pilot tone identification circuit is phase-locked loop identification circuit or frequency-selecting identification circuit.
The frequency of described pilot tone identification circuit identification is 19KHZ.
The utility model is owing to increased the pilot tone identification circuit of the 19KHZ pilot signal of identification FM broadcasting special use on original circuit, pilot tone identification circuit output identification signal is controlled mute control circuit, thereby make the fm broadcast receiver automatic silencing or claim reliable and stable, affected by environment little, the strong anti-interference performance of automatic switching, receiving sensitivity height, do not hinder carrying out of the auxiliary communication broadcasting service of FM broadcasting again.
Below in conjunction with the drawings and the specific embodiments the utility model is described in further detail.
Fig. 1 is the composite signal spectrum distribution schematic diagram of China's pilot tone system FM stereophonic broadcast.
Fig. 2 is a schematic block circuit diagram of the present utility model.
Fig. 3 is embodiment circuit theory diagrams of the present utility model.
Shown in Figure 1, the baseband signal of pilot tone system FM stereophonic broadcast signal comprises 4 parts, and first is that main channel is and signal, represents that with M=L+R it occupies the 15KHZ bandwidth; Second portion is that subchannel is the carrier-suppressed double sideband modulation signal of difference signal, represents that with S=L-R it occupies the 30KHZ bandwidth, and the frequency deviation of this two part signal is 60KHZ; Third part is the 19KHZ pilot signal, its frequency deviation be 7.5KHZ account for maximum frequency deviation 75KHZ 10%; The 4th part is the subsidiary communications broadcast singal, is called for short SCA broadcasting, and it occupies the 16KHZ bandwidth between the 59KHZ to 75KHZ, and frequency deviation is defined as 7.5KHZ.In these signals, the 19KHZ pilot signal is originally and is used for recovering the usefulness that the 38KHZ subcarrier is made stereo demodulation, it account for total frequency deviation 10% and amplitude highly stable, and along with the signal that start produces, shutdown disappears of head-end modulator.Whether being different from the demodulation result of other signals in numerous radio signals, is the characteristic signal of FM stereophonic broadcast, exist by 19KHZ pilot signal behind the detection frequency discrimination to can be used as whether the signal that is received is unique foundation of FM stereophonic broadcast.
Shown in Figure 2, a kind of fm broadcast receiver of the present utility model, comprise casing, be fixed on loudspeaker and receiving demodulation circuit 1, mute control circuit 2 and power amplifier 3 on the casing, the output of receiving demodulation circuit 1 audio frequency is connected with mute control circuit 2, the output of mute control circuit 2 signals is connected with power amplifier 3, power amplifier signal 3 outputs to loudspeaker RL, receiving demodulation circuit 1 output composite signal is connected with pilot tone identification circuit 4, pilot tone identification circuit 4 output identification signal control mute control circuits 2.Pilot tone identification circuit 4 is phase-locked loop identification circuit or frequency-selecting identification circuit.The frequency of pilot tone identification circuit (4) identification is 19KHZ.
Shown in Figure 3, be a kind of specific embodiment of the utility model, fm broadcast signal is handled the output composite signal to stereo demodulation circuit 6 through receiving frequency-discriminating circuit 5, stereo demodulation circuit 6 is sent audio signal and pilot tone identification signal, audio signal is delivered to power discharging integrated block 9 through volume control circuit 8 and is carried out power amplification, drives sound horn through coupling capacitance C2; The pilot tone identification signal is delivered to stereo indicating circuit 7, and stereo indicating circuit 7 output electronegative potentials are through resistance R 1, the stable power discharging integrated block 9 of delivering to of capacitor C 1 time-delay, control power amplifier noise elimination.
Reception frequency-discriminating circuit 5 shown in Figure 3, stereo demodulation circuit 6 and stereo indicating circuit 7 realize that by integrated package CXA1238 it is the LM386 integrated package that power discharging integrated block 9 is selected model for use.Its operation principle is as follows: after integrated package CXA1238 receives the FM stereophonic broadcast signal, demodulate audio signal and export from 5 pin, through volume control circuit to LM386 integrated package 3 pin; The pilot tone identification circuit that comprises in the stereo demodulation circuit is discerned the 19KHZ pilot signal, drive stereo indicating circuit from 4 pin output electronegative potential, after 1 time-delay of resistance R 1 and capacitor C is stable, deliver to LM386 integrated package 2 pin, mute control circuit in the LM386 integrated package is opened, LM386 integrated package operate as normal drives sound horn.Behind the FM stereophonic broadcast blackout, the 19KHZ pilot signal also disappears thereupon, the 19KHZ pilot signal identification of pilot tone identification circuit among the integrated package CXA1238 to disappearing, driving stereo indicating circuit makes 4 pin current potentials become high potential by electronegative potential, after 1 time-delay of resistance R 1 and capacitor C is stable, LM386 integrated package 2 pin also become high potential, and the squelch circuit of LM386 integrated package inside quits work the power amplifying part in the integrated package, and the utility model is in noise-limited condition.The signal that receives as integrated package CXA1238 does not have the 19KHZ pilot signal after demodulation, the utility model is in noise-limited condition.
Receiving demodulation circuit 1 among Fig. 2 is made up of reception frequency-discriminating circuit 5 among Fig. 3 and stereo demodulation circuit 6; Pilot tone identification circuit 4 among Fig. 2 is made up of stereo carrier recovery circuit of phase-locked loop and stereo indicating circuit 7 that the stereo demodulation circuit 6 among Fig. 3 comprises; Mute control circuit 2 among Fig. 2 is the mute control circuit in the power discharging integrated block 9 among Fig. 3; Power amplifier 3 among Fig. 2 is the power amplifier in the power discharging integrated block 9 among Fig. 3.
Claims (3)
1, a kind of fm broadcast receiver, comprise casing, be fixed on loudspeaker and receiving demodulation circuit, mute control circuit and power amplifier on the casing, the output of receiving demodulation circuit audio frequency is connected with mute control circuit, the output of mute control circuit signal is connected with power amplifier, the power amplifier signal outputs to loudspeaker, it is characterized in that: described receiving demodulation circuit (1) output composite signal is connected with pilot tone identification circuit (4), pilot tone identification circuit (4) output identification signal control mute control circuit (2).
2, fm broadcast receiver according to claim 1 is characterized in that: described pilot tone identification circuit (4) is phase-locked loop circuit or frequency selection circuit.
3, fm broadcast receiver according to claim 1 and 2 is characterized in that: the frequency of described pilot tone identification circuit (4) identification is 19KHZ.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 01211149 CN2475231Y (en) | 2001-03-16 | 2001-03-16 | FM broadcast receiver |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 01211149 CN2475231Y (en) | 2001-03-16 | 2001-03-16 | FM broadcast receiver |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN2475231Y true CN2475231Y (en) | 2002-01-30 |
Family
ID=33630592
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 01211149 Expired - Fee Related CN2475231Y (en) | 2001-03-16 | 2001-03-16 | FM broadcast receiver |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN2475231Y (en) |
-
2001
- 2001-03-16 CN CN 01211149 patent/CN2475231Y/en not_active Expired - Fee Related
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C19 | Lapse of patent right due to non-payment of the annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |