Patent ID: 6029053
Filing Date: 2000-02-22
Classification: H04B

Abstract:
A method for reducing interference between multiple frequency modulated, FM, voice transmissions present in the same frequency bandwidth, comprising the steps of:receiving a radio signal which includes a first FM voice signal to be demodulated along with one or more additional, interfering FM voice signals which are present within a modulation bandwidth of the first FM voice signal;detecting the presence of a carrier frequency signal of the first FM signal, including differentiating strongest carrier frequency signal as the carrier frequency signal of the first FM signal and tracking the frequency of the carrier frequency signal of the first FM signal;determining a lack of modulation of the detected carrier frequency signal by a voice signal during portions of the first FM voice signal;squelching the received signal during the portions of the first FM voice signal when the carrier signal is unmodulated.detecting the presence of additional carrier frequency signals in the same frequency bandwidth as the first FM signal;demodulating the received signal to a baseband signal in response to the tracked carrier frequency signal of the first FM signal;filtering detected additional carrier frequency signals from the baseband signal prior to squelching;detecting the modulation of the first FM signal carrier frequency by a vowel sound;determining frequency characteristics of the detected vowel sound; andadaptively filtering the baseband signal to enhance the determined frequency characteristics of the detected vowel sound.