Abstract: Disclosed is a digital stereo multiplexing-demultiplexing system based on the use of delta-sigma modulation. Creation of left (L?R) and right (L+R) channels is achieved using a binary delta adder IC circuit. Delta adder is an ordinary binary adder with an interchanged role of the Sum and Carry-Out terminals. Two channel multiplexer and demultiplexer are implemented with ordinary binary logic gates. Output of the multiplexer is modulated and transmitted to the receiver where demultiplexing is performed. The proposed method can combine two or more digital stereo channels. This method is not application limited, and can be used in acoustic, video, or photo applications.

Abstract: Disclosed are four independent circuits for compression, expansion, companding, and post-processing of a compressed delta-sigma bit-stream. Compression and expansion are based on the use of a second-order (or higher-order) delta-sigma modulator, and a nonlinear operation on a delta-sigma modulated bit-stream. Depending on application, the disclosed circuits can operate as a stand-alone integrated circuit, or as compandor apparatus as proposed. Inherited low-pass filter can be digital or analog. Thus, the only external analog component to the IC chip could be a capacitor C, when low-frequency analog signal is compressed or expanded.

Abstract: Disclosed is the delta-sigma amplitude modulation system. Operation of amplitude modulator is based on the use of the second-order delta-sigma modulator. Polar delta-sigma bit-stream is nonlinearly processed in the negative feedback of delta-sigma modulator to produce an amplitude modulated signal. All information about modulating signal is contained in both envelope and carrier of the modulated signal. Thus, because of a dual nature of modulated signal, one can detect zero-crossings of a carrier, using sign detector, to obtain a polar delta-sigma bit stream. By demodulation (low-pass filtering) this polar bit-stream modulating signal is obtained. The main advantages of a proposed system are: simple digital amplitude modulator and simple demodulator which can be integrated in one IC chip. Because of non-positional nature of delta-sigma bit stream, proposed system is robust to channel errors.