Digitally implemented variable phase shifter and amplitude weighting

Abstract

A variable phase shifter and amplitude weighting (VPSAW) device capable of selectively varying the phase and amplitude of an incoming RF signal (RF.sub.IN) in such a manner as to produce an output RF signal (RF.sub.OUT) having a selected phase and amplitude, by means of splitting the RF.sub.IN signal into first and second signal components, selectively shifting the phase of each of these two components, and then combining the thusly selectively phase-shifted first and second signal components. In the presently contemplated best mode of the present invention, the VPSAW device includes digitally-implemented componentry, e.g., microprocessor-controlled direct, digital synthesizers, for generating first and second control signals, e.g., selectively phase-shifted sinusoidal signals, indicative of first and second phase shift increments, .phi..sub.a and .phi..sub.b, respectively, to be imparted to the first and second signal components, respectively. The VPSAW device of the best mode further includes first and second signal mixers for mixing together the first and second control signals with the corresponding first and second signal components, to thereby phase shift the first and second signal components by the first and second phase increments .phi..sub.a and .phi..sub. b, respectively. The first and second phase shift increments, .phi..sub.a and .phi..sub.b, satisfy a prescribed algorithm which results in the RF.sub.OUT signal having the selected phase (.phi..sub.c) and the selected amplitude (C), e.g., .phi..sub.a =.phi..sub.c +COS.sup.-1 (1/2 C) and .phi..sub.b =.phi..sub.c -COS.sup.-1 (1/2 C). Additionally, the first and second mixers may serve to downconvert the RF.sub.IN signal by subtracting the frequency of the first and second control signals from the frequency of the first and second signal components.