Chapter 11 – Phase Shifters

Publisher Summary RF and microwave phase shifters have many applications in various equipments. Changing the phase of each array element allows the main antenna beam to be steered. Phase shifters utilize diodes, FETs, ferrites, transmission-line segments, and hybrids. The final choice of a phase shifter network depends on the required bandwidth, insertion loss, switching speed, power handling accuracy, and resolution. A choice between analog and digital control must also be made. Varactor continuous phase shifters can achieve a large amount of phase shift and high speed, and require fewer diodes than digital phase shifters, but at the cost of decreased accuracy, relatively narrow band, and low-input power levels. Because the phase shift in the switched-line configuration is well defined by differences in the line length only, this phase shifter is useful in devices without adjustments, and it is very stable over time and temperature. Switched-line digital phase shifters providing a certain phase increment can be made by a series connection of individual switched-line phase shifters. Switched bit phase shifters are generally used where there are requirements for very high switching speeds and moderate-to-high power handling capability. The problem with multibit phase shifters is a large variation in the return loss across the phase states. Also, more bits add insertion loss and accumulate phase error. The mismatch effect limits the phase resolution and accuracy of the phase shifter. The only solution is to provide good return loss of each individual bit.