The high free-space loss and the limited performance of CMOS active and passive components at high frequencies impose the application of beamforming to enable wireless communication in the mm-wave band. At the receiver side, beamforming improves the SNR and increases immunity against interfering signals. However, broadband implementation of beamforming at mm-wave frequencies in CMOS requires extensive routing of high-frequency signals over the CMOS substrate, yielding loss and matching problems. In order to minimize these problems, in combination with low area and power consumption, phase shifting in the LO path is an appealing candidate [1]. In this paper, a CMOS implementation of this technique, based on a widely tunable QVCO is presented. Each path achieves 30dB of gain and a minimum NF of 7.1dB, yielding a system NF of 4.1dB. The overall current draw is 54mA from a 1.2V supply. Additionally, a calibration procedure to mitigate the analog impairments imposed by the proposed implementation is demonstrated.The architecture of the integrated 2-path receiver front-end section is depicted in Fig. 9.3.1. Each path consists of an LNA, a direct-downconversion mixer and a phase selector. The QVCO provides quadrature phases of the LO signal, routed to the phase selectors in both paths. Digital control of the phase selectors determines the phase of the LO signal at the input of each mixer.The single-stage common-source inductively degenerated cascode LNA ( Fig. 9.3.1) features frequency tuning, provided by a small digitally controlled load varactor C D . This feature allows in situ detection of the frequency where the LNA gain peaks, by performing an RF frequency sweep for both settings. The center frequency can be identified as the frequency where both receiver gain characteristics intersect. A 4-bit digital control on the size of the cascode transistor M 2 implements the gain selection in the LNA. A single-balanced Gilbert mixer with resistive load realizes the downconversion. It uses an inductor to tune out the capacitance at the drain of the RF input transistor [2]. The mixer is followed by a two-stage buffer, from which the last stage drives the 50Ω input impedance of the measurement equipment. The QVCO consists of two cross-coupled LC-VCOs, locked in quadrature by parallel coupling [3]. The 4 phases of the QVCO are applied to the 4 branches in the phase selector ( Fig. 9.3.1) that share a resonant load. The biasing of each branch is controlled separately, allowing phase manipulation of the signal that drives the LO input of the mixer. Our test-bench allows continuous beamsteering resolution, but in practice this resolution will be limited by the resolution of the integrated DAC.Implementation of broadband mm-wave multiple antenna systems in CMOS is complicated due to the high frequency signal loss and matching issues. Our layout approach to mitigate these problems is shown in Fig. 9.3.7. Most inductive components have been implemented as lumped components to optimize their area and boost their quality factor. Caref...