An apparatus includes a controller having differential modulation control outputs and is configured to provide differential modulation signals having a particular frequency at the differential modulation control outputs. A differential modulator circuit is coupled between first differential terminals and second differential terminals. The differential modulator circuit has differential modulation control inputs coupled to the differential modulation control outputs. The differential modulator circuit is configured to: modulate first differential signals at the first differential terminals with the differential modulation signals having the particular frequency, provide the modulated first differential signals at the second differential terminals, modulate second differential signals at the second differential terminals with the differential modulation signals having the particular frequency, and provide the modulated second differential signals at the first differential terminals.

A method and system are disclosed for communicating using both analog and digital transmissions on the same bandwidth. The method may include receiving a digital transmission and an analog transmission using a same/shared bandwidth. The method may include playing a digital audio of the digital transmission and an analog audio of the analog transmission using a same audio output. The digital transmission may include an identification code. The playing of the digital audio may include selectively playing the digital audio based on a match of the identification code with a stored identification code of the system and selectively squelching the digital audio based on a mismatch of the identification code with the stored identification code.

An apparatus includes a controller and a circuit. The controller has control outputs and including a programmable delay circuit. The circuit is coupled between first terminals and second terminals, the modulator circuit having control inputs coupled to the control outputs, the circuit configurable to: receive modulation signals at the control inputs; modulate first signals at the first terminals with the modulation signals; provide the modulated first signals at the second terminals. modulate second signals at the second terminals with the modulation signals; and provide the modulated second signals at the first terminals.

A demodulation method of differential phase shift keying (DPSK) signals includes receiving a modulation signal using a phase extraction circuitry. A plurality of signal points is acquired, which is constructed by phase values of point positions of the modulation signal. A demodulation value of the current signal point is acquired according to the current signal point, the previous signal point, and a predefined demodulation algorithm. A demodulation signal is acquired according to the demodulation values corresponding to the signal points. A demodulation system and a communication device are also provided.

A signal transfer architecture can include a transmit-side device configured to provide first and second signals from an original signal, and to transmit a combined signal including signals representative of the first and second signals. The architecture can further include a receive-side device configured to receive the combined signal and provide a reconstructed signal based on the received combined signal, such that the reconstructed signal is representative of the original signal. In some applications, the original signal can include a plurality of data frames each containing respective information, the first signal can include a compressed signal, and the second signal can include a delta signal representative of a difference between the original signal and the compressed signal.

Systems and methods are disclosed for transmission and reception of backscattering signals using 2K Phase Shift Keying (PSK) (2K-PSK) modulation and/or multiple access techniques.

A rail communication system supporting higher data rate in wireless data communications in 20 kHz channels in the 44 MHz band for railroad applications using any one or more of the following: higher data rate modulations, robust demodulations, and more efficient over-the-air protocols.