Patent ID: 8781031
Filing Date: 2014-07-15
Classification: H04L

Abstract:
1. A low rate radio frequency signal receiver for frequency shift key (FSK) modulation, said low rate receiver including: an antenna to receive FSK radio frequency signals, a low noise amplifier to amplify and filter the signals picked up by the antenna, a local oscillator to supply oscillating signals having a substantially identical frequency to the carrier frequency of the incoming FSK radio frequency signals, a phase shift circuit to perform a 0° to 90° phase shift and vice versa in the oscillating signals or the incoming FSK radio frequency signals, in each semi-period of a phase switching cycle, so as to generate, alternately and successively, in-phase and quadrature oscillating signals, or in-phase and quadrature incoming FSK radio frequency signals, a mixer to successively mix the in-phase and quadrature oscillating signals with the amplified and filtered incoming FSK radio frequency signals, or the oscillating signals with the in-phase and quadrature FSK radio frequency signals, so as to generate alternately intermediate in-phase and quadrature baseband signals, at least one low-pass filter to filter the intermediate in-phase and quadrature baseband signals, and a demodulation stage to demodulate data from the filtered intermediate in-phase and quadrature baseband signals, wherein the receiver is arranged such that the phase shift circuit is switched by a phase selection signal to a phase switching cycle frequency which is lower than a frequency deviation of the modulated data in the FSK radio frequency signals and higher than a frequency of a modulated data rate, and wherein the demodulation stage input includes a demultiplexer to receive the filtered intermediate in-phase and quadrature signals, said demultiplexer being controlled by the phase selection signal so as to supply cyclically the filtered intermediate in-phase signals at a first output and the filtered intermediate quadrature signals at a second output, and a data demodulator receiving the filtered intermediate in-phase and quadrature signals from the demultiplexer, to supply data signals.