Abstract: A quadrature device 1 for a communication device, receiver, transmitter, transceiver, telephone, mixer, modulator or demodulator comprises I and Q signal paths and corresponding signal paths components 2I, 2Q; 4I, 4Q; 9I, 9Q showing a mismatch. The device 1 comprises switching circuitry 3, 3?, 6, 3?, 3?? for data dependently exchanging the I and Q signals in the I and Q paths in order to improve adverse effects, such as reduction of leakage of quantisation noise from the image band to the signal band in a quadrature modulator. Even mismatch effects between digital to analog converters (DAC's) in a feedback path of a sigma delta (??) modulator are compensated.

Abstract: A receiver with an integrated mixer/Sigma-Delta Modulator configuration for digitizing a relatively low-bandwidth signal modulated on a high-frequency carrier, for example in a radio receiver. The Sigma-Delta Modulator has an continuous-time loop filter (F1, F2) with anti-aliasing characteristics which eliminate the need for a separate lowpass filter between the mixer (MX) and the Sigma-Delta Modulator.

Abstract: Sigma-delta modulator in which the gain stage (20) of the input network and the gain stage (22) of the feedback network are regularly interchanged (“chopped”). This averages out the difference between the two gain stages, thus defining the gain of the system accurately. The difference in gain between the two gain stages is modulated on the chopping frequency, which may be outside the frequency band of interest. Furthermore, by using fully differential circuitry the chopping can be effected in such a manner that the offset and flicker noise of the two gain stages are modulated to the chopping frequency.

Abstract: Sigma-delta analog-to-digital converter topology with an error signal branch including a subtractor (10), a loop filter (4), and a quantizer (6), and a feedback branch including a digital-to-analog converter (8). The gain error caused by a return-to-zero switch in the feedback branch is cancelled by moving the return-to-zero switch (20) to the signal error branch.