Four-bit Phase Research Articles

Application of GaAs Discrete p-HEMTs in Low Cost Phase Shifters and QPSK Modulators

The application of a discrete pseudomorphic high electron mobility transistor (p-HEMT) as a grounded switch allows for the development of low cost phase shifters and phase modulators operating in a Ku band. This fills the gap in the development of phase control devices comprising p-i-n diodes and microwave monolithic integrated circuits (MMICs). This paper describes a discrete p-HEMT characterization and modeling in switching mode as well as the development of a low-cost four-bit phase shifter and direct quadrature phase shift keying (QPSK) modulator. The developed devices operate in a Ku band with parameters comparable to commercially available MMIC counterparts. Both of them are CMOS compatible and have no power consumption. The parameters of the QPSK modulator are very close to the requirements of available standards for satellite earth stations.

Phase control of pulsed broadband microwave amplifiers

A phase shifter for pulsed broadband amplifiers is described. The phases of the input and output signals are compared in a polar discriminator, and an error signal is derived which steers a voltage-controlled phase shifter at the amplifier input. Applications are for smoothing out within-pulse and pulse-to-pulse phase shift in amplifiers and for providing a relatively accurate phase shifter for active phased arrays using amplifiers. A four-bit phase shifter has been built and measured in the 3-3.5 GHz band. The paper reports steady-state and transient performance.