JPH04227125A - Reception equipment - Google Patents

Abstract

PURPOSE:To perform the reception of signals of different modulation systems satisfactorily by automatically switching a detection system. CONSTITUTION:A temporal amplitude fluctuation extractor 10 which extracts the temporal fluctuation of amplitude of a reception signal as a means which selects detectors 6. 7 of different detecting systems by switching a switch 8 and an identification processor 11 which identifies the modulation system by processing an extracted signal are provided, and the modulation system is identified by comparing amplitude values obtained at the identification processor 11, and a correspondent detector is selected by the switch 8 based on an identified result.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus, and more particularly to a receiving apparatus capable of receiving received signals of different modulation methods.

0002

2. Description of the Related Art FIG. 2 shows an example of a conventional receiving apparatus that receives radio waves of different modulation methods, for example, an AM modulated wave and an FM modulated wave. In the figure, a signal received by a receiving antenna 1 is amplified by an RF circuit 2, converted to an IF signal by a mixer 3 using a local oscillation signal from a local oscillation circuit 4, and further the signal level is controlled by an AGC circuit 5. . This signal is divided into two parts, one of which is amplitude detected by an AM detector 6, and the other is frequency detected by an FM detector 7. Then, each detected signal is selected by a switch 8 and outputted from a speaker 9 as an audio signal. At this time, the listener switches the switch 8 while listening to the sound from the speaker 9, and selects the clearer AM or FM sound.

0003

[Problems to be Solved by the Invention] In this conventional receiving device, the listener (human) identifies the modulation method of the received signal and manually switches the switch 8 to select the corresponding detector. it takes time. Further, there is a problem that erroneous identification may occur, making it difficult to perform appropriate reception. SUMMARY OF THE INVENTION An object of the present invention is to provide a receiving device that can automatically switch modulation methods and always receive signals in a suitable state.

0004

[Means for Solving the Problems] A receiving device of the present invention includes a plurality of detectors that detect received signals using different detection methods, and a switch that selects the signal detected by each detector. The receiver is provided with means for extracting temporal amplitude fluctuations of the received signal, and means for identifying the modulation method by differentiating and integrating the extracted temporal amplitude fluctuations. The configuration is such that the detector is selected by switching and operating the detector. For example, the detector is configured to include an AM detector and an FM detector, and the switch is configured to switch to the FM detector when the amplitude output obtained by the identification means is large.

[0005]

[Operation] According to the present invention, the modulation method can be identified by the identification means, and based on the identification result, the switching device is switched to the detector of the detection method corresponding to the modulation method, thereby automatically following the modulation method. It becomes possible to select a suitable detection method.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a system diagram of one embodiment of the present invention. In the figure, the same parts as in the conventional structure of FIG. 2 are given the same reference numerals. In addition to the configuration of FIG. 2, here the AGC circuit 5
In the subsequent stage, there is a temporal amplitude fluctuation extractor (hereinafter referred to as FFT) device 10 that detects the temporal amplitude fluctuation of the IF-converted signal, and the output of this FFT device 10 is subjected to differentiation and integration processing to obtain AM and FM. An identification processor 11 is connected to the terminal, and the output of the identification processor 11 is used to switch the switch 6.

According to this configuration, a received signal coming from the receiving antenna 1 is amplified by the RF circuit 2, converted to an IF signal by the mixer 3 using a local oscillation signal from the local oscillation circuit 4, and further amplified by the AGC circuit. 5 controls the signal level. This signal is divided into three parts, one being detected by the AM detector 6 and the other being detected by the FM detector 7. Furthermore, the remaining one performs FFT processing on the IF signal using the FFT unit 10 to extract temporal amplitude fluctuations of the carrier signal. Furthermore,
The discrimination processor 11 discriminates between AM and FM based on the temporal amplitude fluctuation of the extracted carrier signal, and the switch 8 is switched to AM or FM based on this. This results in
Switching between AM and FM is automatically realized, and the audio obtained by the selected detection method is output from the speaker 9.

The functions of the FFT unit 10 and the identification processor 11 will be explained next. In the case of AM waves, Figure 3(a) shows
) shows the frequency spectrum in the case of FM waves. When the temporal amplitude fluctuations of these AM and FM are extracted using the FFT unit 10, as shown by the broken line in FIG.
The temporal amplitude of M is constant. In addition, in the case of FM waves, the amplitude of the carrier signal FM changes depending on the magnitude of the modulation index of the input received wave (normally, in the case of audio modulation, the modulation index constantly changes), as shown by the solid line in the same figure. . Next, when the signal extracted by the identification processor 11 is differentiated with respect to time and squared,
The amount of change in the amplitude of the FM wave becomes 0 as shown by the solid line FM in FIG. 5, and the amount of change in the amplitude of the AM wave becomes 0 as shown by the broken line AM in the same figure. Furthermore, when this signal is integrated by the identification processor 11, FM
The amplitude of the wave increases with time as shown by the solid line FM in Figure 6, and A
The amplitude of the M wave becomes 0 as indicated by the broken line AM in the figure. By comparing the magnitudes of these two amplitude values, the modulation method can be identified, such as when the value is large, the FM modulation method is identified, and when the value is small, the AM modulation method is identified, and the corresponding detection method is identified. Either the FM detector 7 or the AM detector 6 will be selected.

[0009]

As explained above, the present invention extracts temporal amplitude fluctuations using an FFT device, identifies a modulation method from the extracted signal in an identification processor, and performs a corresponding detection based on the identification result. Since the type of detector can be selected, there is an effect that reception can always be automatically performed using a detection method corresponding to the modulation method.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an embodiment of a receiving device of the present invention.

FIG. 2 is a system diagram of an example of a conventional receiving device.

FIGS. 3(a) and 3(b) are spectrum diagrams of an AM signal and an FM signal.

FIG. 4 is a characteristic diagram of temporal amplitude fluctuations of AM and FM signals extracted by FFT.

FIG. 5 is a characteristic diagram of AM and FM signals differentiated by the identification processor.

FIG. 6 is a characteristic diagram of AM and FM signals integrated in the identification processor.

[Explanation of symbols]

2 RF circuit 3 Mixer 4 Local oscillation circuit 6 AM detector 7 FM detector 8 Switcher 10 FFT machine 11 Identification processor

Claims (2)

[Claims] Claim 1: In a receiving device comprising a plurality of detectors that detect received signals using different modulation methods, and a switch that selects the signal detected by each detector, the temporal amplitude fluctuation of the received signal is and a means for identifying the modulation method by performing differentiation and integration processing on the extracted temporal amplitude fluctuation, and the switching device is configured to switch according to the output of the identification means. Features of the receiving device. 2. The detector according to claim 1, wherein the detector is composed of an AM detector and an FM detector, and the switch is configured to switch to the FM detector when the amplitude output obtained by the identification means is large. Receiving device.