Abstract: A method for transmitting and receiving digitally modulated wireless signals using an analog FM transceiver is provided. The analog FM transceiver has a transmit speech audio frequency band, a receive speech audio frequency band substantially equal to the transmit speech audio frequency band, a subaudible frequency band, a direct microphone audio input, and a direct speaker audio output. The method includes generating, in a baseband digital spectrum translator external to the analog FM transceiver, a baseband transmit signal occupying frequencies substantially within the transmit speech audio frequency band of the analog FM transceiver. The method also includes applying the generated baseband transmit signal to the direct microphone audio input to thereby transmit a digitally encoded RF TX signal having a constant envelope and using the analog FM transceiver to receive a digitally encoded RF RX signal with a constant envelope and to generate a baseband receive signal using the digitally encoded RF RX signal.

Abstract: A method and system is provided for improving bit error rate (BER) performance in delay spread fading conditions, such as the fading associated with simulcast systems. BER is improved through novel symbol synchronization that comprises oversampling an input signal and filtering the samples to determine a composite symbol sample point that converges toward the center of the signal's effective eye pattern. The composite symbol sample point may be an average of previous composite symbol sample points and an instantaneous sample point determined based on samples from a synchronization field of the signal. The updated composite symbol sample point may be utilized for future sampling of the incoming signal.

Abstract: A method for generating a modulated carrier signal with reduced bit error rates based on a plurality of data symbols. A plurality of data symbols are received, and a digital input signal is generated based on the plurality of data symbols. The digital input signal are filtered to produce a digital output signal including a phase characteristic. The phase characteristic of the digital output signal remains close to the desired symbol phase for substantial portion of the symbol period. A carrier signal is modulated using the digital output signal to produce the modulated carrier signal.

Abstract: A method and system is provided for improving bit error rate (BER) performance in delay spread fading conditions, such as the fading associated with simulcast systems. BER is improved through novel symbol synchronization that comprises oversampling an input signal and filtering the samples to determine a composite symbol sample point that converges toward the center of the signal's effective eye pattern. The composite symbol sample point may be an average of previous composite symbol sample points and an instantaneous sample point determined based on samples from a synchronization field of the signal. The updated composite symbol sample point may be utilized for future sampling of the incoming signal.

Abstract: A method for transmitting and receiving digitally modulated wireless signals using an analog FM transceiver is provided. The analog FM transceiver has a transmit speech audio frequency band, a receive speech audio frequency band substantially equal to the transmit speech audio frequency band, a subaudible frequency band, a direct microphone audio input, and a direct speaker audio output. The method includes generating, in a baseband digital spectrum translator external to the analog FM transceiver, a baseband transmit signal occupying frequencies substantially within the transmit speech audio frequency band of the analog FM transceiver. The method also includes applying the generated baseband transmit signal to the direct microphone audio input to thereby transmit a digitally encoded RF TX signal having a constant envelope and using the analog FM transceiver to receive a digitally encoded RF RX signal with a constant envelope and to generate a baseband receive signal using the digitally encoded RF RX signal.

Abstract: A method for generating a modulated carrier signal with reduced bit error rates based on a plurality of data symbols. A plurality of data symbols are received, and a digital input signal is generated based on the plurality of data symbols. The digital input signal are filtered to produce a digital output signal including a phase characteristic. The phase characteristic of the digital output signal remains close to the desired symbol phase for substantial portion of the symbol period. A carrier signal is modulated using the digital output signal to produce the modulated carrier signal.

Abstract: A method for generating a modulated carrier signal with reduced bit error rates based on a plurality of data symbols. A plurality of data symbols are received, and a digital input signal is generated based on the plurality of data symbols. The digital input signal are filtered to produce a digital output signal including a phase characteristic. The phase characteristic of the digital output signal remains close to the desired symbol phase for substantial portion of the symbol period. A carrier signal is modulated using the digital output signal to produce the modulated carrier signal.

Abstract: Squelch circuit and method useful in frequency-scanned radio receivers are provided. Generally, the squelch circuit includes an audio-removal filter coupled to receive an audio signal. The passband of the audio-removal filter is selected sufficiently high relative to frequency components of the audio signal. An absolute value detector is coupled to the audio-removal filter to supply an output signal having a positive polarity regardless of the polarity of the signal supplied by the audio-removal filter. An integrating filter is coupled to receive the output signal from the absolute value detector and supply an integrated signal. The integrating filter has at least one selectable filter coefficient indicative of the response time of the integrating filter.

Abstract: Squelch circuit and method useful in frequency-scanned radio receivers are provided. Generally, the squelch circuit includes an audio-removal filter coupled to receive an audio signal. The passband of the audio-removal filter is selected sufficiently high relative to frequency components of the audio signal. An absolute value detector is coupled to the audio-removal filter to supply an output signal having a positive polarity regardless of the polarity of the signal supplied by the audio-removal filter. An integrating filter is coupled to receive the output signal from the absolute value detector and supply an integrated signal. The integrating filter has at least one selectable filter coefficient indicative of the response time of the integrating filter.