Neelanjan Sarmah

A Fully Integrated 240-GHz Direct-Conversion Quadrature Transmitter and Receiver Chipset in SiGe Technology

This paper presents a fully integrated direct-conversion quadrature transmitter and receiver chipset at 240 GHz. It is implemented in a 0.13-μm SiGe bipolar-CMOS technology. A wideband frequency multiplier (×16) based local-oscillator (LO) signal source and a wideband on-chip antenna designed to be used with an external replaceable silicon lens makes this chipset suited for applications requiring fixed and tunable LO. The chipset is packaged in a low-cost FR4 printed circuit board resulting in a complete solution with compact form-factor. At 236 GHz, the effective-isotropic-radiated-power is 21.86 dBm and the minimum single-sideband noise figure is 15 dB. The usable RF bandwidth for this chipset is 65 GHz and the 6-dB bandwidth is 17 GHz. At the system level, we demonstrate a high data-rate communication system where an external modem is operated in its two IF-bandwidth modes (250 MHz and 1 GHz). For the quadrature phase-shift keying modulation scheme, the measured data rate is 2.73 Gb/s (modem 1-GHz IF) with bit-error rate of 10-9 for a 15-cm link. The estimated data rate over the 17-GHz RF bandwidth is, hence, 23.025 Gb/s. Also, higher order modulation schemes like 16 quadrature amplitude modulation (QAM) with a data rate of 0.677 Gb/s and 64-QAM with a data rate of 1.0154 Gb/s (modem 250-MHz IF) is demonstrated. A second application demonstrator is presented where the wide tunable RF bandwidth of the chipset is used for material characterization. It is used to characterize an FR4 material (DE104) over the 215-260-GHz range.

A 0.53 THz Reconfigurable Source Module With Up to 1 mW Radiated Power for Diffuse Illumination in Terahertz Imaging Applications

This paper presents a high-power 0.53 THz source module with programmable diversity to adjust the brightness and the direction of light to obtain the desired diffuse lighting conditions in THz imaging applications. The source module consists of a single SiGe BiCMOS chip which operates an array of 16 source-pixel incoherently. Each source pixel consists of a primary on-chip ring-antenna and two triple-push oscillators locked 180° out-of-phase. The module provides a total radiated power of up to 1 mW (0 dBm) with 62.5 μW (-12 dBm) per source pixel on average and an EIRP per pixel of 25 dBm. The circuit layout is scalable in size and output power. The chip consumes up to 2.5 W from a 2.4 V supply and 3.2 mW from a digital 1.2 V supply respectively. The module includes a secondary silicon lens, is programmable through a CPLD, and supplied from a USB port. The THz radiation can be recorded with a CMOS 1 k-pixel THz video camera and represent an all silicon solution for real-time active THz imaging.

14.5 A 0.53THz reconfigurable source array with up to 1mW radiated power for terahertz imaging applications in 0.13μm SiGe BiCMOS

Recently, silicon-based THz video cameras have been demonstrated for industrial, surveillance, scientific, and medical applications in the THz range (300GHz to 3THz) [1]. Such camera implementations favor pixels with antenna-coupled direct detectors for a low power dissipation and a high pixel count. Despite this progress, they lack the required sensitivity for passive imaging and imagers are in the need of artificial illumination to provide the required image quality. The choice has been to use expensive high-power focused illumination with a single direction for the incoming beam, which seriously limits the image quality due to its specular nature. Additionally, detectors in a focal-plane array configuration share the available source power and the image SNR further drops with the camera resolution. Like imaging at visible light, where shades or reflectors are commonly used, active THz imaging would greatly benefit from incoherent artificial light sources to adjust brightness, phase/frequency, and the direction of light to obtain the desired lighting conditions.

160-GHz Power Amplifier Design in Advanced SiGe HBT Technologies With

Power amplifier (PA) design for 160-GHz applications in an advanced SiGe heterojunction bipolar transistor (HBT) technology with saturated output power (Psat) in excess of 10 dBm is presented. The architecture is based on a three-stage pseudodifferential configuration that was implemented in SiGe HBT evaluation technology with fmax of 400 GHz. At saturation, a PA breakout circuit delivers 10 dBm with 20-dB gain. From 150 to 170 GHz, the small-signal gain is within 20-32 dB and the output referred 1-dB compression point (P1 dB) is 8.5 dBm at 160 GHz. High output power was possible due to optimum device sizing, efficient layout, and accurate EM modeling. To our best knowledge, this is the highest output power reported for silicon PAs operating beyond 120 GHz.

{P}_{\rm sat}

Wideband x16 multiplier chains targeted for high speed communication and radar applications above 200 GHz are presented in this paper. The x16 topology is based on 4 cascaded Gilbert-cell-based frequency doublers without any hybrids and intermediate drive amplifiers. The low external input frequency (14-17.5 GHz), enables the use of very low-power frequency dividers and also interfacing with commercial synthesisers below 20 GHz. Two versions of the circuit were implemented. Version 1 is a standalone x16 chain and Version 2 is Version 1 plus wideband 3-stage PA. For Version 1, the measured peak output power is -8.5 dBm at 255 GHz with 40 GHz bandwidth (3 dB) and dc power consumption of 0.3 W. For Version 2, the peak output power is 0 dBm at 245 GHz with 30 GHz bandwidth (3 dB) and 0.7 W dc power consumption. These results are single ended on-wafer measurements without dembeding the 2.5 dB loss due to the output pad and balun. The available differential output power, to drive on-chip components like mixers, antennas etc, is -6 dBm for Version 1 and 2.5 dBm for Version 2. Additionally, break out sructures for wideband PAs operating at 240 GHz were characterised. The peak power gain at 240 GHz was 7 and 10 dB for the 3 and 4 stages respectively over a 30 GHz bandwidth. The measured Psat was 5 dBm at 240 GHz.

in Excess of 10 dBm

Summary form only given. High-power, broadband power amplifiers (PA) operating in the D-band (110-170 GHz) are essential towards implementation of broadband frequency multiplier chains at sub-mmWave frequencies. In this paper we present the design of a 3-stage power amplifier (PA) with 3-dB bandwidth of 35 GHz (135-170 GHz) and implemented in 130 nm SiGe BiCMOS technology. A staggered tuning approach where the peak gain of the individual or group of individual stages are tuned at offset frequencies is used for broadband operation. In the 135-170 GHz, the small signal gain for the PA is 14-17 dB and the saturated output power (Psat) varies from 5-8 dBm and the output referred 1 dB compression point (P1dB) varies from 1-6 dBm over this frequency range. The nominal dc power consumption of this PA is 320 mW with peak PAE of 1.6%. To our best knowledge, this is the highest bandwidth reported for silicon PAs in the D band.

235–275 GHz (x16) frequency multiplier chains with up to 0 dBm peak output power and low DC power consumption

This paper reports on the design of a broadband lens-integrated differentially-driven circularly polarized annular slot on-chip antenna for a 240 GHz homodyne monostatic FMCW transceiver in a SiGe HBT technology. A complete antenna layout consists of the main radiating annular slot fed by a wideband differential quadrature coupler. The slot is excited by 2 pairs of orthogonal sectorial patch probes located 90° apart along the slot circumference, whereby the mutual coupling between them is exploited to extend the antenna operation bandwidth. The circularly-polarized antenna was simulated to provide an input match superior to -25 dB for 180-310 GHz with consistent radiation patterns. The antenna allows a frequency-unlimited high-efficiency operation of the FMCW transceiver module with a Tx/Rx isolation below -22 dB for 180-310 GHz, a peak radiated power of 4 dBm and in excess of -10 dBm for 214-268 GHz.

A 135–170 GHz power amplifier in an advanced sige HBT technology

A 240-GHz monostatic circular polarized SiGe frequency-modulated continuous wave radar system based on a transceiver chip with a single on-chip antenna is presented. The radar transceiver front-end is implemented in a low-cost 0.13 µm SiGe HBT technology version with cut-off frequencies f T /f max of 300/450 GHz. The transmit block comprises a wideband ×16 frequency multiplier chain, a three-stage PA, while the receive block consists of a low-noise amplifier, a fundamental quadrature down-conversion mixer, and a three-stage PA to drive the mixer. A differential branch-line coupler and a differential dual-polarized on-chip antenna are added on-chip to realize a fully integrated radar transceiver. All building blocks are implemented fully differential. The use of a single antenna in the circular polarized radar transceiver leads to compact size and high sensitivity. The measured peak-radiated power from the Si-lens equipped radar module is +11 dBm (equivalent isotropically radiated power) at 246 GHz and noise figure is 21 dB. The characterization bandwidth of the radar transceiver is 60 GHz around the center frequency of 240 GHz, and the simulated Tx-to-Rx leakage is below −20 dB from 230 to 260 GHz. After system calibration the resolution of the system to distinguish between two targets at different distance of 3.65 mm is achieved, which is only 21% above the theoretical limit.

A wideband 240 GHz lens-integrated circularly polarized on-chip annular slot antenna for a FMCW radar transceiver module in SiGe technology

A complete circularly polarized 210-270-GHz frequency-modulated continuous-wave radar with a monostatic homodyne architecture is presented. It consists of a highly integrated radio-frequency transceiver module, an in-house developed linear-frequency chirp generator, and a data acquisition chain. The radar front end featuring a fundamentally operated ×16 multiplier-chain architecture is realized as a single chip in 0.13-μm SiGe heterojunction bipolar transistor technology with a lens-coupled circularly polarized on-chip antenna and wire-bonded on a low-cost printed circuit board. In combination with a 9-mm-diameter silicon lens, the module achieves an average in-band directivity of 26.6 dB. The measured peak radiated power from the packaged radar module is +5 dBm and the noise figure is 21 dB. For a 60-GHz frequency sweep, the radar achieves a range resolution of 2.57 mm after calibration, which is close to the theoretical bandwidth-limited resolution of 2.5 mm. With a simple scanning optical setup, this paper further demonstrates the 3-D imaging capability of the radar for detection of hidden objects with a remarkable dynamic range of around 50 dB.

A 240-GHz circularly polarized FMCW radar based on a SiGe transceiver with a lens-coupled on-chip antenna

A 200-225 GHz SiGe combiner Power Amplifier (PA) based on a wideband 4-way power combiner architecture is presented in this paper. The circuit is implemented in a 130 nm SiGe BiCMOS technology with fT/fmax of 250/370 GHz. A parallel power combining architecture based on the low-loss transmission line based zero-degree combiner is used to combine the power from 4 PA cores. At 215 GHz, the Psat is 9.6 dBm and from 200-225 GHz the average Psat is 9 dBm. From 200-225 GHz, the combiner enhances the Psat from the unit PA cores by 3.5-4 dB. For this circuit, the peak small signal gain is 25 dB at 213 GHz. To the best of the authors knowledge, this is the highest reported output power for silicon PAs above 200 GHz.