Methods and apparatus for downconverting signals from...

Details Methods and apparatus for downconverting signals from... Methods and apparatus for downconverting signals from...

2006-06-13

2006-06-13

Kumar, Pankaj (Department: 2631)

Pulse or digital communications

Receivers

Angle modulation

Reexamination Certificate

active

07061998

ABSTRACT:
A technique for down converting signals from an Intermediate Frequency (IF) input signal to Inphase (I) and Quadrature (Q) signal samples at baseband replaces power-consuming A/D converters and AGC circuits with a low-cost zero-crossing comparator. The comparator converts the IF signal to a hard-limited signal having one value when the IF signal is positive and another value when the IF signal is negative. I and Q samples are generated by performing the equivalent of multiplication of the hard-limited signal by cos(2πfo*t) and sin(2πfo*t). By sampling the hard-limited signal at a rate that is an integer multiple of the intermediate frequency and an even number greater than or equal to four, multiplication by cos(2πfo*t) and sin(2πfo*t) required to generate I and Q baseband signal components is greatly reduced. The I and Q samples are summed (or integrated) by binary up/down counters over one bit duration and then dumped. The dumped counter outputs are estimates of the lowpass filtered I and Q signal components.

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