The design, analysis, implementation and measurement of an integrated V-band receiver front-end based on $0.15~\mu \text{m}$ GaAs pHEMT process are presented in this paper. The front-end chip uses the super-heterodyne topology which consists of a low noise amplifier, an image reject mixer, and a multiply-by-four ( $\times 4$ ) LO chain. In order to minimize the power consumed by LO chain, an active single-ended mixer is designed which requires extremely low LO power of −5 dBm. Meanwhile, the effect of signal coupling in the integrated chip is analyzed and solutions are proposed. By introducing appropriate filters into the circuit and optimizing the overall layout, the imbalance of in-phase and quadrature signals caused by unwanted coupling can be effectively mitigated, thus enhancing the image rejection of the chip. Probe and module tests are applied to the receiver front-end, and the measurement results reveal that the chip achieves −3 ± 0.7 dB conversion gain, 7 dB noise figure and more than 25 dB image rejection ratio in the RF frequency range of 52–56 GHz. Only one supply voltage of 3 V is required for the chip, and total power consumption is 312 mW. Moreover, with a continuously adjustable phase control of 360° and very broadband IF characteristics, the front-end chip is very suitable for passive millimeter-wave imaging application.

In this paper, a novel broadband lumped-element quadrature hybrid MMIC for interferometric correlation radiometer is proposed. First, the cause of the bandwidth limitation in the lumped-element branch-line coupler is analyzed, which is the two identical parallel branches have the same frequency response leading to reinforced resonance and narrow band. In order to reduce such unfavorable superposition effect, parallel branches with opposite frequency responses are used, which exhibits the characteristic similar to rat-race coupler. To realize a quadrature hybrid, a phase-shifting network is cascaded to the rat-race coupler, and the bandwidth is further extended by compensating the passband phase trend and optimizing the inter-stage matching of the two parts. Finally, to facilitate the application, the quadrature hybrid is combined with a variable gain amplifier to implement an integrated MMIC based upon 0.15 um GaAs pHEMT process, and the size of the hybrid part is 1.2×1.4 mm². Within the frequency range of 3.8~8.5 GHz (75% fractional bandwidth), the amplitude and phase imbalance are less than 0.5 dB and 2.6°. All reflections and isolations are better than 16.4 dB. The measured results verify the design theory and illustrate that the lumped-element quadrature hybrid is suitable for compact broadband circuit applications.