A low-loss reflection-type analog phase shifter circuit is described and experimental results are presented. The circuit incorporates several design features to produce nearly 360' of phase shift at X-band while achieving an insertion loss of only 4.8 dB with kQ.5 dB of variation over all phase states. improve upon previously reported X-band performance by demonstrating a large phase shift range together with low attenuation and low amplitude variation with phase state. These results INTRODUCl'IONThe MIC analog phase shifter described here is part of a larger task, the goal of which is the development of a fully monolithic GaAs unit. These circuits are intended for applications to phased array antennas, where insertion loss should be small and, ideally, constant over all phase states to achieve high system performance without the need for additional compensating circuitry. Unlike digital phase shifter approaches, the available phase resolution of the analog phase shifter depends primarily on the number of bits in the D/A converter. Therefore, higher levels of resolution do not result in significant increases in circuit complexity or insertion loss. The analog phase shifter may also be made smaller than the digital phase shifter resulting in higher circuit yield and lower cost. X-band have not simultaneously demonstrated a full 360' phase shift and low insertion loss variation with phase. Results of Reference (1) report an x-band microstrip circulator-coupled phase shifter with about 270' of phase shift and a total insertion loss modulation of 1.7 dB. Reference (2) reports X-band results with a 2.5 dB insertion loss with f0.5 dB of insertion loss variation but only about 105' of phase shift. The circuit approach used here is based on the well known reflection phase shifter, in which the through and coupled ports of a 90' hybrid are terminated in low-loss reactive networks. The other two ports of the hybrid form the circuit input and output. In this work we have used Lange couplers to realize the 90' hybrids and Previously reported phase shifter results at 487 CH2848-0/90/0000-0487$01 .OO 0 1990 IEEE hyperabrupt varactor diode circuits for the terminating impedances.The hyperabrupt active layer of the varactor can be controlled to achieve a capacitance versus voltage characteristic that offers the potential of large phase shifts with approximately linear phase versus voltage behavior.The hyperabrupt varactor diodes are generally characterized by a capacitance versus voltage dependence of the form C = Cjo/(l + V/Vo)y, where y > 1. Cjo is the zero bias capacitance of the device and Vo is the built-in potential of the Schottky junction. The fact that y > 1 in this equation indicates that the depletion layer capacitance decreases rapidly with applied reverse bias. This property is characteristic of hyperabrupt diodes, and sets them apart from the capacitance versus voltage properties of abrupt ( y = 1/21 or linearly graded ( y = 1/31 type doping profiles. This allows large tuning ratios, defined as Cp/Cjmin, to be achi...

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Terrestrial and satellite wireless systems require multicarrier operation of solid-state power amplifiers within specific linearity specifications. This paper evaluates candidate linearity measurement techniques that can be used for linearity characterization, including digital and analog noisepower ratio methods, and three-carrier intermodulation measurements. A correlation between these techniques is made for a specific power amplifier under accelerated life test conditions.

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