Monolithically integrable frequency demodulator device
AssigneeThomson Broadcast Systems
InventorsClaude Claverie, Xavier Guitton
Life of this patent
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Abstract
Frequency modulated signals are demodulated through a limiter circuit that chops the signal to give pulses whose occurrence frequency is proportional to the instant frequency of the received signal. The invention is devoted to a new processing of those pulses. The leading edges of the pulses are time integrated. The obtained signal is then as usual, low pass filtered to give the demodulated signal. The main advantage of this new processing is that the circuit that makes this processing does not implement delay lines and can then be made as a single chips.
Claims26
Circuit of a demodulator of a frequency-modulated signal, the instantaneous frequency of the signal varying between a minimum frequency fmin and a maximum frequency fmax, the circuit having at least one input receiving an input signal formed by a train of pulses, each pulse having a rising edge and a falling edge, the height of a pulse of the input signal being equal to the difference between the level of the signal before a rising or falling edge and its level after this rising or falling edge, the circuit producing on an output of the circuit a signal whose instantaneous integral over time has a value proportional to the instantaneous frequency of the pulses making up the input signal, the circuit being characterized in that it carries out integration over time of the height of at least one of the edges of each pulse of the input signal of the circuit, the time of integration of the height of each integrated edge being a time .tau. at most equal to 1/(2 fmax).
Circuit which comprises two differential structures, according to claim, 3 each of the two structures having the same elements as the other, wired up in the same fashion, each structure having an input and the outputs of each of the structures being linked to one another.
Dependencies are inferred from the claim text.