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US 5,444,416 AGranted
Digital FM demodulation apparatus demodulating sampled digital FM modulated wave
AssigneeSharp Kabushiki Kaisha
InventorsYutaka Ishikawa, Shingo Nomura
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Abstract
The digital FM demodulation apparatus includes a sampling unit, a frequency specifying unit, and a demodulated value specifying unit. The sampling unit samples an FM modulated wave at predetermined intervals. The frequency specifying unit specifies a frequency of the FM modulated wave at the time of sampling based on a plurality of sampled values. The demodulated value specifying unit specifies a demodulated value corresponding to the frequency to provide the demodulated value.
Claims29
A digital FM demodulation apparatus demodulating an FM modulated wave, comprising:
- sampling means for sampling said FM modulated wave at prescribed intervals;
- frequency specifying means for specifying a frequency at the time of sampling based on a plurality of sample values obtained by said sampling means;
- demodulated value specifying means for specifying a demodulated value based on the specified frequency by said frequency specifying means;
- and
- correction means for correcting said demodulated value, when a sample value presently obtained by said sampling means does not satisfy a prescribed condition.
2 more elements
A digital FM demodulation apparatus demodulating an FM modulated wave, comprising:
- sampling means for sampling said FM modulated wave at prescribed intervals;
- frequency specifying means for specifying a frequency at the time of sampling based on a plurality of sample values obtained by said sampling means;
- demodulated value specifying means for specifying a demodulated value based on the specified frequency by said frequency specifying means;
- and
- correction means for correcting said sample values, when said sample values obtained by said sampling means do not satisfy a prescribed condition.
2 more elements
A digital FM demodulation apparatus demodulating an FM modulated wave, comprising:
- sampling means for sampling said FM modulated wave at a prescribed sampling interval T to obtain at least three sample values y.sub.t-T, y.sub.t, y.sub.t+T at times t-T, t, and t+T;
- storage means for storing demodulated values to be specified based on said sample values, each demodulated value being specified by a first address and a second address;
- and
- demodulated value output means for reading a demodulated value from said storage means based on said sample values, said demodulated value output means employing (y.sub.t-T +y.sub.t+T)/2 as said first address and y.sub.t as said second address when .vertline.y.sub.t-T +y.sub.t+T .vertline..ltoreq..vertline.y.sub.t .vertline..
1 more element
A digital FM demodulation apparatus demodulating an FM modulated wave, comprising:
- sampling means for sampling said FM modulated wave at a prescribed sampling interval T to obtain at least three sample values y.sub.t-T, y.sub.t, y.sub.t+T at times t-T, t, and t+T;
- and
- storage means for storing demodulated values to be specified based on said sample values, each demodulated value being specified by a first address and a second address;
- and
- demodulated value output means for reading a demodulated value from said storage means based on said sample values, said demodulated value output means employing (y.sub.t-T +y.sub.t+T)/2 as said second address and y.sub.t as said first address when .vertline.y.sub.t-T +y.sub.t+T .vertline.>.vertline.y.sub.t .vertline..
2 more elements
A digital FM demodulation apparatus demodulating an FM modulated wave, comprising:
- sampling means for sampling said FM modulated wave at a prescribed sampling interval T to obtain at least three sample values y.sub.t-T, y.sub.t, y.sub.t+T at times t-T, t, and t+T;
- frequency specifying means for specifying said frequency based on an expression f.sub.t =[cos.sup.-1 {(y.sub.t-T +y.sub.t+T)/2y.sub.t }]/2.sub..pi. T, and specifying said frequency f.sub.t with (y.sub.t-T +y.sub.t+T)/2 as y.sub.t and y.sub.t as (y.sub.t-T +y.sub.t+T) when .vertline.y.sub.t-T +y.sub.t+T .vertline. >.vertline.2Y.sub.t .vertline.;
- and
- demodulated value specifying means for specifying a demodulated value based on the specified frequency by said frequency specifying means.
1 more element
A method of demodulating an FM modulated wave, comprising:
- a) sampling said FM modulated wave at a prescribed sampling interval T to obtain at least three sample values y.sub.t-T, y.sub.t, y.sub.t+T at times t-T, t, and t+T;
- b) storing, in a storage means, demodulated values to be specified based on said sample values, each demodulated value being specified by a first address and a second address;
- and
- c) reading demodulated values from said storage means based on said sample value, step c) employing (y.sub.t-T +y.sub.t+T)/2 as said first address and y.sub.t as said second address when .vertline.y.sub.t-T +y.sub.t+T .vertline..ltoreq..vertline.y.sub.t .vertline..
1 more element
A method of demodulating an FM modulated wave, comprising:
- a) sampling said FM modulated wave at prescribed intervals;
- b) specifying a demodulated value based on a plurality of sample values obtained in step a);
- c) correcting said demodulated value, when a sample value presently obtained in step a) does not satisfy a prescribed condition.
A method of demodulating an FM modulated wave, comprising:
- a) sampling said FM modulated wave at prescribed intervals;
- b) specifying a demodulated value based on a plurality of sample values obtained in step a);
- and
- c) correcting said sample values, when said sample values obtained in step a) do not satisfy a prescribed condition.
1 more element
A method of demodulating an FM modulated wave, comprising:
- a) sampling said FM modulated wave at a prescribed sampling interval T to obtain at least three sample values Y.sub.t-T, Y.sub.t, y.sub.t+T at times t-T, t, and t+T;
- b) specifying a frequency at the time of sampling based on an expression f.sub.t =[cos .sup.-1 {(y.sub.t-T +y.sub.t+T)/2y.sub.t }]/2.sub..pi. T, and specifying said frequency f.sub.t with (y.sub.t-T +y.sub.t+T)/2 as y.sub.t and y.sub.t as (y.sub.t-T +y.sub.t+T) when .vertline.y.sub.t-T +y.sub.t+T .vertline.>2Y.sub.t .vertline.;
- and
- c) specifying a demodulated value based on said specified frequency.
1 more element
Dependencies are inferred from the claim text.