Radio demodulation circuit

Abstract

The radio demodulation circuit of the present invention demodulates a multi-valued FSK signal with a digital demodulator, performs threshold value judgment on the demodulated output of the digital demodulator with a data judging device, and keeps the threshold value obtained by the data judging device in a threshold value holding device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects of the present invention will become clear from the following description of the preferred embodiments and the appended claims. Those skilled in the art will appreciate that there are many other advantages of the present invention possible by embodying the present invention.

FIG. 1 is a block diagram showing a schematic structure of an FSK radio device that uses a radio demodulation circuit according to a first embodiment of the present invention;

FIG. 2 is a block diagram showing a schematic structure of an FSK radio device that uses a radio demodulation circuit according to a second embodiment of the present invention;

FIG. 3 is a block diagram showing a schematic structure of an FSK radio device that uses a radio demodulation circuit according to a third embodiment of the present invention;

FIG. 4 is a timing chart of judging a threshold value of a demodulation base band signal according to the second embodiment of the present invention;

FIG. 5 is an illustration showing code transitions and detection change points in four-valued FSK radio communication according to the second embodiment of the present invention;

FIG. 6 is a timing chart of judging the code in the four-valued FSK radio communication according to the second embodiment of the present invention;

FIG. 7 is a block diagram showing a schematic structure of an FSK radio device that uses a radio demodulation circuit according to a fourth embodiment of the present invention;

FIG. 8 is an illustration showing code transitions and synchronizing point monitoring range in the four-valued FSK radio communication according to the fourth embodiment of the present invention; and

FIG. 9 is a block diagram showing a schematic structure of a remote controller according to a fifth embodiment of the present invention.

Claims

1. A radio demodulation circuit, comprising: a digital demodulator for demodulating a multi-valued FSK signal;a data judging device for judging a threshold value of a demodulated output of said digital demodulator; anda threshold value holding device for keeping said threshold value obtained by said data judging device.

2. The radio demodulation circuit according to claim 1, further comprising: a synchronizing point detecting device that detects changing points in said demodulated output, and then detects synchronizing points of said multi-valued FSK signal based on said changing points that have been detected; anda demodulation signal synchronizing output device that outputs a threshold value judgment result through said data judging device at said synchronizing points, and a synchronizing clock that synchronizes with transmission speed of said demodulated output.

3. The radio demodulation circuit according to claim 2, further comprising a synchronizing point holding device for keeping said synchronizing points.

4. The radio demodulation circuit according to claim 2, further comprising a multi-valued synchronizing point judging device, wherein: said multi-valued FSK signal has a plurality of frequency components whose modulation degrees are set in accordance with each code that is superimposed on said signal;said demodulated output has a plurality of voltage components that correspond to said plurality of frequency components; andsaid multi-valued synchronizing point judging device selectively judges said synchronizing points, as synchronizing points, at which a voltage transition is generated between said voltage components that correspond to said frequency components whose said modulation degrees are deviated equally to one another from a center frequency of said multi-valued FSK signal in said threshold value judgment result.

5. The radio demodulation circuit according to claim 2, further comprising a multi-valued synchronizing point judging device, wherein: said multi-valued FSK signal has a plurality of frequency components whose modulation degrees are set in accordance with each code that is superimposed on said signal;said demodulated output has a plurality of voltage components that correspond to said plurality of frequency components; andsaid multi-valued synchronizing point judging device extracts said synchronizing point from a synchronizing point group that is detected by said synchronizing point detecting device in said threshold value judgment result, at which a voltage transition is generated between said voltage components that correspond to said frequency components whose said modulation degrees are largest to a center frequency of said multi-valued FSK signal, and judges said extracted synchronizing point as a synchronizing point.

6. The radio demodulation circuit according to claim 5, wherein: said threshold value holding device sets threshold values that is apparently differentiable into binary, as said threshold values in multi-valued modulation; andsaid multi-valued synchronizing point judging device extracts said synchronizing point at which a change to binary is generated apparently in said threshold value judgment result, and judges said extracted synchronizing points as synchronizing points.

7. The radio demodulation circuit according to claim 1, comprising: a maximum value holding device for keeping a maximum value of said demodulated output;a minimum value holding device for keeping a minimum value of said demodulated output; andan optimum threshold value calculator for calculating an optimum value of said threshold values from an output of said maximum value holding device and an output of said minimum value holding device, whereinsaid threshold value holding device keeps said threshold value calculated by said optimum threshold value calculator.

8. The radio demodulation circuit according to claim 3, further comprising a synchronizing point monitoring device wherein said synchronizing point monitoring device determines a synchronizing point based on a counted number of said synchronizing points held in said synchronizing point holding device; after determining said synchronizing point, extracts synchronizing points that said synchronizing point detector detects within an arbitrary range on a time axis with a central focus on said determined synchronizing point; and judges said extracted synchronizing points as synchronizing points.

9. A remote controller, comprising: a radio communication LSI to which the radio demodulation circuit according to claim 1 is mounted for performing radio transmission and reception;an antenna for transmitting and receiving a radio signal of said radio communication LSI;a microcontroller for performing a control of said radio communication LSI;a key input device for performing input to said microcontroller; anda display device for performing an arbitrary display through a control from said microcontroller.