JP3019423B2 - Receiver - Google Patents

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 schemes.

[0002]

2. Description of the Related Art FIG. 2 shows an example of a receiving apparatus for receiving radio waves of different modulation systems, for example, a conventional receiving apparatus for receiving 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 into an IF signal by a mixer 3 by a local oscillation signal from a local oscillation circuit 4, and further controlled by an AGC circuit 5 in signal level. . This signal is bisected, 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 switched and selected by the switch 8 and output from the speaker 9 as an audio signal. At this time, the listener performs switching by the switch 8 while listening to the sound from the speaker 9, and selects the clearer AM or FM sound.

[0003]

In this conventional receiving apparatus, the listener (human) identifies the modulation method of the received signal, and switches the switch 8 manually to select the corresponding detector. take time. In addition, there is a problem that identification may be performed erroneously and it is difficult to perform suitable reception.
SUMMARY OF THE INVENTION An object of the present invention is to provide a receiving apparatus that automatically switches a modulation method and always enables reception in a suitable state.

[0004]

A receiving apparatus according to the present invention includes a plurality of detectors for detecting received signals by different detection methods, and a switch for selecting a signal detected by each detector. The receiving device is provided with a means for extracting a temporal amplitude fluctuation of the received signal, and a means for identifying the modulation method by differentiating and integrating the extracted temporal amplitude fluctuation, and a switching device is provided by an output of the identifying means. Are switched to select a detector. For example, the detector is constituted by an AM detector and an FM detector, and the switch is switched to the FM detector when the amplitude output obtained by the identification means is large.

[0005]

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

[0006]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of one embodiment of the present invention. 2, the same parts as those of the conventional structure of FIG. 2 are denoted by the same reference numerals. In addition to the configuration of FIG.
A temporal amplitude fluctuation extraction (hereinafter, referred to as FFT) unit 10 for detecting a temporal amplitude fluctuation of the IF-converted signal in a subsequent stage, and an output of the FFT unit 10 is differentiated and integrated to perform AM and FM. Is connected, and the switch 6 is switched by the output of the identification processor 11.

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

Next, the operation of the FFT unit 10 and the discrimination processor 11 will be described. FIG. 3A shows the case of the AM wave.
(B) shows a frequency spectrum in the case of an FM wave. When the temporal amplitude fluctuation of these AM and FM is extracted by the FFT unit 10, the temporal amplitude of the AM wave carrier signal AM becomes constant as shown by the broken line in FIG. Also, in the case of FM waves, the magnitude of the modulation index of the input received wave as shown by the solid line in the figure (normally, the modulation index constantly fluctuates in the case of voice modulation)
, The amplitude of the carrier signal FM varies. 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 as shown by the solid line FM in FIG. 5, and the amount of change in the amplitude of the AM wave is shown in FIG. 0 like the broken line AM
Becomes Further, when this signal is integrated by the identification processor 11, the amplitude of the FM wave increases with time as shown by the solid line FM in FIG. 6, and the amplitude of the AM wave becomes 0 as shown by the broken line AM in FIG.
By comparing the amplitude values of the two, the FM modulation method is identified when the value is large, the AM modulation method is identified when the value is small, and the modulation method is identified. The FM detector 7 or the AM detector 6 will be selected.

[0009]

As described above, according to the present invention, the temporal amplitude fluctuation is extracted by the FFT unit, the modulation system is identified from the extracted signal by the identification processor, and the corresponding detection is performed based on the identification result. Since it is possible to select a detector of the modulation method, there is an effect that reception by the detection method corresponding to the modulation method can always be automatically performed.

[Brief description of the drawings]

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. 3A and 3B are spectrum diagrams of an AM signal and an FM signal, respectively.

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

FIG. 5 is a characteristic diagram of each signal of AM and FM differentiated in the identification processor.

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

[Explanation of symbols]

 2 RF circuit 3 Mixer 4 Local oscillation circuit 6 AM detector 7 FM detector 8 Switching device 10 FFT device 11 Discrimination processor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/06-1/16 H03D 5/00

Claims (2)

(57) [Claims] 1. A receiving apparatus comprising: a plurality of detectors for detecting a received signal using different modulation schemes; and a switch for selecting a signal detected by each detector. And a means for identifying the modulation method by differentiating and integrating the extracted temporal amplitude fluctuation, and the switching means is configured to perform the switching operation by the output of the identification means. Characteristic receiving device. 2. The detector according to claim 1, wherein the detector comprises an AM detector and an FM detector, and switches the switch to the FM detector when the amplitude output obtained by the identification means is large. Receiver.