Gilbert cell

Abstract: This paper demonstrates the low voltage operation of a doubly balanced Gilbert mixer fabricated in a 0.8-/spl mu/m CMOS process and operating as both a down-converter and an up-converter. As a down-converter with an RF input of 1.9 GHz, the mixer has a single sideband noise figure as low as 7.8 dB and achieved down-conversion gain for supply voltages as low as 1.8 V. As an up-converter, the mixer demonstrates 10 dB of conversion gain at an RF frequency of 2.4 GHz with an applied local oscillator (LO) power of -7 dBm and LO-RF/LO-IF isolation of at least 30 dB. Up-conversion gain was achieved over a 5-GHz bandwidth and at supply voltages as low as 1.5 V. The mixer presented demonstrates the lowest single side band noise figure for a CMOS doubly balanced down-converting mixer and the highest frequency of operation for a mixer fabricated in CMOS technology to date.

Abstract: In this paper, a miniaturized D-band frequency-modulated continuous-wave (FMCW) radar sensor with 48-GHz bandwidth (32.8%, 122-170 GHz) and a high measurement rate of > 1 kHz for multi-target vibration measurements is presented. The sensor is based on a SiGe transceiver monolithic microwave integrated circuit manufactured via Infineon's B7HF200 bipolar production technology with an fT of 170 GHz and fmax of 250 GHz. Gilbert cell, push-pull, and varactor-based doubler concepts on manufactured chips are compared, and the most promising signal source is embedded into a transceiver chip, which forms the main component of the presented radar sensor. The maximum output power of the system is ≈ -10 dBm and a phase noise of ≈ -80 dBc/Hz is achieved. Measurements are provided to demonstrate the sensor characteristics and show the promising results of FMCW radar in highest precision distance and multi-target vibration measurement applications. Due to the covered wide bandwidth, a range resolution of 5.88 mm is achieved ( -6-dB width, Tukey window). The sensor's distance measurement repeatability is 290 nm (65 nm with 10 × averaging and 0.5-m target distance), and the distance measurement accuracy is m for a target in 65-cm distance moving 1 cm. Additionally, vibration measurement results and range-Doppler plots for advanced multi-target applications are presented.

Abstract: Monolithically integrated 220- and 320-GHz receiver front-ends manufactured in an engineering version of anfT/fmax=280/435-GHz SiGe technology are presented. Subharmonic mixing is provided by a Gilbert cell with stacked switching quads fed by quadrature 110/160-GHz local oscillator (LO) signals. The 220-GHz version of the front-end is equipped with an integrated LNA with a measured 15-dB gain and 28-GHz bandwidth. This front-end yields a conversion gain of 16 dB, an 18-dB single-sideband (SSB) noise figure (NF), and a 30-GHz bandwidth when pumped with a 0-dBm 110-GHz LO signal. The 320-GHz version of the front-end omits the low-noise amplifier and features an integrated × 9 LO multiplier chain to facilitate operation and characterization. A conversion gain of -14 dB and a 36-dB SSB NF is obtained over the 313-to-328-GHz frequency range. The presented circuits demonstrate that a fully integrated receiver front-end can be implemented up to submillimeter-wave frequencies in an SiGe HBT technology.

Abstract: A CMOS Gilbert cell mixer biasing topology is presented. The new biasing technique offers several key advantages over the traditional biasing arrangement. First, the new topology allows the designer to easily adjust the bias current present in the Gilbert cell input transistors, while maintaining bias currents in other portions of the circuit. Second, the mixer linearity can be improved using this biasing method by accurate adjustment of the input MOSFET operating point. Third, the biasing method reduces the "voltage headroom" difficulties inherent to the Gilbert cell, which uses a stacked arrangement of transistors. The importance of these adjustments with regard to the mixer conversion gain and IP3 is examined.