JPH03187622A - Signal identification receiver - Google Patents

Abstract

PURPOSE:To identify accurate modulation form by sampling the output signal of a demodulation circuit for each of AM and FM on a time axis and identifying the modulation form depending on the result of accumulation of the amplitude distribution of each sample. CONSTITUTION:The receiver is provided with sampling circuits 7, 8 sampling outputs of AM and FM demodulation circuits 5, 6 respectively on a time axis and an amplitude distribution detector 10 to accumulate the amplitude distribution of a demodulation signal component from the output of the sampling circuits 7, 8 and to identify the modulation from the result of accumulation. Then a switch 11 selects a proper demodulation circuit with a signal being the result of modulation identification of the amplitude distribution detector 10 and an audio amplifier 12 amplifies the output up to a required level to attain automatic reception and listening. Thus, the modulation form is identified with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal identification receiver, and particularly to a signal identification receiver that receives a communication wave of a desired arbitrary frequency, identifies the modulation format of the communication wave,
This invention relates to a signal identification receiver that automatically receives signals.

[Conventional technology]

Conventionally, this type of signal identification receiver has been tuned to any communication frequency and manually switched and demodulated the modulation format. In addition, when automatically identifying the modulation format, it has been done by integrating the output of a typical demodulation circuit such as AM or FM, and comparing the magnitude of the integration circuit output.

[Problem to be solved by the invention]

The conventional receiver described above demodulates by manually switching the modulation format of the received signal, so it is not possible to instantaneously perform tuning 1 demodulation, and when using a circuit that automatically identifies the modulation format, the reception If the device is not completely tuned to the communication wave, or if the level of the received signal is low and the signal-to-noise ratio is poor, the output of the AM/FM demodulation circuit, which is a typical demodulation circuit, will be
This method has the disadvantage that the noise component becomes large, making it impossible to accurately identify the modulation format.

[Means to solve the problem]

The signal identification receiver of the present invention analyzes the presence or absence of a communication signal and signal specifications in an arbitrary frequency band, and the signal identification receiver automatically identifies the modulation type of the communication signal.
The present invention has a configuration in which highly accurate modulation format identification is performed based on the cumulative results of samples and amplitude distributions of the samples on the time axis of the output signals of the M and FM demodulation circuits.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

The embodiment of FIG. 1 includes receiving antennas 1. High frequency amplifier 22 local oscillator 3. IF amplifier 4. AM demodulation circuit5. FM demodulation circuit6. A sampling circuit 7 for sampling the outputs of the AM and FM demodulation circuits 5 and 6 on the time axis, respectively.
, 8. An amplitude distribution detector 10 for accumulating the amplitude distribution of the signal component of the demodulated signal from the outputs of the sampling circuits 7 and 8 and identifying the modulation type from the result;
0, and an audio amplifier 12 that amplifies the AM or FM demodulated output output via the switch 11 to a required level and outputs demodulated audio. Note that FIG. 1 also shows a clock generator 9 for sampling.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

In the embodiment shown in FIG. 1, the portion indicated by the dashed line is directly related to the present invention. The received signal is converted into an IF by a high frequency amplifier 2 and a local oscillator 3 in the same manner as normal heterodyne reception, and after being amplified by an IF amplifier 4, it is input to an AM demodulation circuit 5 and an FM demodulation circuit 6. In each demodulation circuit, the input signal is demodulated, but in this case, the ideal modulated signal, that is, the ideal AM or FM signal in which the modulated signal is composed only of complete AM or FM acid components, is demodulated. When demodulating with an ideal AM or FM demodulator, only the AM demodulation circuit output is output for AM signals, and only the FM demodulation circuit output is output for FM signals.
The outputs of demodulation circuits that are not compatible with each other become 0, making it possible to easily identify the modulation type.

However, the actual received signal usually contains AM/FM components. Also, since the FM demodulation circuit has a non-linear circuit such as a limiter circuit, the AM and F
Phenomena such as M conversion occur. Furthermore, if the tuning □ is not perfect in the AM demodulation circuit, a phenomenon occurs in which FM is converted to AM due to the band edge of the IF filter. As described above, since an FM acid component is present in the AM signal and an AM acid component is present in the FM signal, the accuracy of modulation identification decreases if only the detection output is integrated.

In order to improve these problems, the present invention samples the detector outputs of the AM and FM demodulation circuits on the time axis, as shown in FIG. 1, and further obtains the sampled amplitude distribution. That is, as shown in Fig. 2, for example, when an AM wave is received, pulse-like noise is generated in the output of the FM demodulation circuit 6 for the above-mentioned reason.The amplitude distribution in this case is as shown in Fig. 2(a). As shown in FIG.
As shown in b), it is mostly distributed in zone ①. The output of the demodulation circuit adapted in this way has little distribution at extremely low levels, i.e., zone 1 in Figure 2, or extremely high levels, i.e., the level of zone 2 in Figure 2, and is mostly distributed near the center. Therefore, using this result, it is possible to easily and accurately identify the modulation. In the present invention, a demodulation circuit that is more suitable for the signal of this modulation identification result is connected to the switch 11.
The audio signal is selected by the audio amplifier 12, and then amplified to the required level, and automatically received and listened to.

〔Effect of the invention〕

As explained above, in order to automatically select a modulation format in a receiver that automatically receives any frequency band, the present invention includes sampling on the time axis in a circuit that automatically identifies a modulation format. By further observing the amplitude distribution characteristics, high-angle modulation types can be identified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the signal identification receiver of the present invention, and FIG. 2 is a block diagram of the FM demodulation circuit 6 (a) when receiving an AM signal in the embodiment of FIG. ) and AM demodulation circuit 5(b)
FIG. 3 is a diagram showing an example of demodulated signal and amplitude distribution characteristics of FIG. DESCRIPTION OF SYMBOLS 1... Antenna, 2... High frequency amplifier, 3... Local oscillator, 4... IF amplifier, 5... AM demodulation circuit,
6...FM demodulation circuit, 7...sampling circuit, 8
...Sampling circuit, 9...Clock generator, 1
0... Amplitude distribution detector, 11... Switch, 12.
...Audio amplifier.

Claims (1)

[Claims] In a signal identification receiver that analyzes the presence or absence of a communication signal and signal specifications in a given frequency band, in order to automatically identify the modulation type of the communication signal, a A signal identification receiver characterized in that it performs highly accurate modulation format identification based on the cumulative results of samples and amplitude distributions of each sample.