Patent
Radio receiver circuit with tuning feedback control for a tunable bandpass filter
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TLDR
A zero-IF radio receiver circuit comprises an input filter (3), quadrature mixers (9,10), d.c.-blocking capacitors (24,26), and a demodulator (22).Abstract:
A zero-IF radio receiver circuit comprises an input filter (3), quadrature mixers (9,10), d.c.-blocking capacitors (24,26) and a demodulator (22). The circuit is partly integrated on a semiconductor chip and an inductive component of the input filter comprises one or more of the chip bond-wires. In order to compensate for the inevitable variation of the inductance of these bond-wires from circuit to circuit part of the signal from the local oscillator (12) is added to the input signal before its application to the input filter and the d.c. component of the resulting output from one mixer (10), which component is representative of the phase shift of the local oscillator signal produced by the input filter and hence of any tuning error of this filter, is applied to a tuning control input (30) of the filter to reduce the error. Alternatively the tuning control signal may be adjusted to maximize the sum of the squares of the d.c. components of the signals in the two IF channels and hence minimize the attenuation produced by the input filter.read more
Citations
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References
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