Device for demodulating a binary phase-shift keyed signal

Details Device for demodulating a binary phase-shift keyed signal Device for demodulating a binary phase-shift keyed signal

1999-01-20

2000-10-31

Grimm, Siegfried H.

Demodulators

Phase shift keying or quadrature amplitude demodulator

Input signal combined with local oscillator or carrier...

329310, 375327, 375328, H04L 2722

Patent

active

061408697

ABSTRACT:
A device for demodulating a binary signal having a predetermined carrier frequency and phase-modulated by encoded pulses. The device includes a phase-locked loop circuit having a phase comparator followed by a low-pass filter and a voltage-controlled oscillator, which is voltage-controlled by the output of the filter. The voltage-controlled oscillator outputs a binary signal that is synchronous with the modulated signal and at a frequency N times the carrier frequency. The phase-locked loop circuit also includes a divider that divides by N the output signal of the oscillator and supplies the divided signal to one input of the phase comparator. Thus, a binary signal synchronous with the modulated signal and having a frequency equal to the carrier frequency is supplied to one input of the phase comparator. The other input of the phase comparator receives the modulated signal. Further, the output of the oscillator is supplied as a clock signal to a first binary counter so as to measure the duration of high levels of the modulated signal, and to a second counter so as to measure the duration of low levels of the modulated signal. The counters are used to detect phase changes in the modulated signal at the two levels. The demodulation device of the present invention is particularly suited for use in the transmission of data between a contactless-type smart card and a system having a reader for such cards.

REFERENCES:
patent: 3852811 (1974-12-01), Aghazadeh

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