Design Considerations for Octave-Band Phase Shifters Using Discrete Components

A new method for octave-band phase-shifter design based on high-pass, low-pass, bandpass, and all-pass networks (APNs) using discrete components is presented. First, the general synthesis method is provided to find the optimum return loss and phase error of a high-pass/low-pass phase shifter. It is also shown that the conventional design method is a special case of the method presented here. The proposed method facilitates tradeoffs between the bandwidth, phase error, and return loss, which is not possible in the conventional method. Phase bits of 22.5 degrees, 45 degrees, and 90 degrees are designed using this method. For the phase bit of 180 degrees, a new topology using a third-order bandpass network and an APN is proposed. The phase error is reduced from 25 degrees to 7.4 degrees and the return loss is improved from 5 to 22 dB over the whole octave band compared to the conventional method. For the cascaded 4-bit phase shifter, the return loss is improved from 5 to 19 dB and the rms phase error is reduced from 13.5 degrees to 4.3 degrees in theory. The experimental results of the 4-bit phase shifter show an rms phase error of 5.9 degrees and a return loss of 13 dB from 530 to 1090 MHz. The maximum amplitude imbalance is 0.6 dB for all 16 phase states.