Square-law companding apparatus based on nonlinear operations on modulated bit-stream
AssigneeDjuro G. Zrilic
InventorDjuro George Zrilic
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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.
Claims4
A compressor apparatus comprising:
- a second-order or higher-order delta-sigma modulator;
- a comparator to convert bipolar delta modulated bit-stream D into unipolar bit-stream Xn;
- a rectifying encoder, which consists of a D flip-flop and XNOR gate, and accept bit-streams Xn and Xn-1 to produces rectified signal Yn;
- a feedback low-pass filter, for filtering (smoothening) a unipolar bit-stream Yn, and produces analog signal y(t);
- an analog inverter circuit to invert analog signal y(t), and produce −y(t) signal;
- an amplitude modulator whose inputs are high-frequency digital signal D, analog signals y(t), −y(t), and the output signal of the amplitude modulator is a(t), which goes to the negative input of the Δ-Σ modulator;
- and
- a low-pass filter for demodulation of a compressed bit-stream D.
An expander apparatus comprising:
- a second-order or higher-order delta-sigma modulator;
- a comparator to convert bipolar delta modulated bit-stream into unipolar bit-stream;
- a rectifying encoder, which consists of a D flip-flop and XNOR gate;
- a low-pass filter for smoothing unipolar digital signal Yn;
- an analog inverter circuit to invert analog signal y(t), and produce −y(t) signal;
- an amplitude modulator with inputs D, y(t), −y(t);
- and
- a low-pass filter to smooth the output of the amplitude modulator, and produce filter out expanded signal e(t).
Dependencies are inferred from the claim text.