This paper presents an X/Ku dual-band switch-free reconfigurable GaAs low-noise amplifier (LNA) realized by inter-stage and output-stage coupled lines. This paper is the first switch-free reconfigurable LNA design in the coupled lines structure. After amplified by the broadband drive stage, the input signal is divided into two parallel single-band stages (consists of a high-band stage and a low-band stage) by the proposed inter-stage coupled line. Two split-band signals are combined by the proposed output-stage coupled line into the output port after amplified by the single-band stages. The proposed coupled lines are also included in LNA matching networks. Dual-band operation of the proposed reconfigurable LNA is achieved by turning off drain voltages of the unused single-band transistors. The reconfigurable LNA is designed in a 0.15-μm E-mode GaAs pHEMT process. The fabricated LNA features small-signal gains of 25-25.2/20.1-28 dB, noise figure (NF) of 1.28-1.41/1.23-1.51 dB, and output 1-dB compression point of 0.5-1.7/2.2-5 dBm over 8-10/12-20 GHz, while consuming 76/91 mA of dc current, with a size of 2.0×1.8 mm 2. INDEX TERMS coupled line, gallium arsenide (GaAs), low-noise amplifier (LNA), monolithic microwave integrated circuit (MMIC), multi-band.

The proposed 6-bit switched phase shifter is implemented in 0.15-μm GaAs pHEMT process. The measured root-mean-square (rms) phase error is less than 2.8°at 12-18 GHz, and the average insertion loss (IL) is 6.5-6.9 dB. The chip size of the proposed 6-bit digital phase shifter is 3.1 × 1 mm 2 , including all RF and dc pads, which is very suitable for radar systems.