Method and device for implementing tracking filters and RF front end of software defined radios

摘要

A tracking circuit has first and second filters controlled by clock signals and a combiner. Each filter has N paths in parallel between an input and an output, each path comprising a respective first/second sub-circuit and a switch (N is an integer >1). The clock signals selectively control each of the N switches of the first and second filters at a same frequency, and in variously described embodiments the first and second on-time durations may be different, the first and second sub-circuits may be different, or both first/second on-time durations and first/second sub-circuits may be different. Signals output from the first and second filter are added at a combiner. In certain examples each path in the first and second filter is controlled by same-phase clock signals, and every path on either filter are controlled with different-phase clock signals.

主权项

1. A circuit comprising:
a first filter comprising a plurality of N paths in parallel between an input and an output, each of-the N paths comprising a first sub-circuit and a switch; a second filter comprising a plurality of N paths in parallel between an input and an output, each of the N paths comprising a second sub-circuit and a switch; clock signals to selectively control switches of the first filter at a same frequency for a first on-time duration, and to selectively control switches of the second filter at the same frequency for a second on-time duration, in which at least one of a) the first and second on-time durations are different, and b) the first and second sub-circuits are different; and a combiner for adding signals from the output of the first filter and from the output of the second filter; where the first filter, the second filter and the combiner together form an N-path tunable filter wherein a center frequency of a response of the N-path tunable filter is controlled by the frequency of the clock signals by shifting an amplitude of a response at the center frequency of the first filter and the second filter, and where an output of the combiner represents a difference between the amplitude of the response of the first filter and the amplitude of the response of the second filter.