A Broadband Digital Diode Phase Shifter Using a Matrix Interconnection of Quadrature Hybrid Couplers.

An analysis of 2-bit digital diode phase shifter using four PIN diodes and a matrix arrangement of four 3-dB quadrature hybrids has been performed. The 0 degrees, 90 degrees, 180 degrees, and 270 degrees differential phase states were achieved by using the 90 degrees phase relationship of the hybrid coupler outputs and proper combinations of open circuits and short circuits provided by the diodes with the appropriate bias. The phase state determined at which of two ports of the hybrid matrix the output occurred thus an additional SPDT or transfer switch was needed to complete the phase shifter. Broad bandwidths can be achieved, since the bandwidth of the phaser is limited by the hybrid bandwidth and the band over which the diode open and short can be made to track, plus the bandwidth of the single transfer switch. With the addition of a second transfer switch in conjunction with a 45 degrees Schiffman constant phase shift section, a 3-bit, or 45 degrees resolution, phase shifter can be obtained. The effects of certain component errors and imperfections on the performance of the phaser have been presented a generalized method for an exact error analysis has been derived.