Tushar K. Thrivikraman

A Silicon-Germanium Receiver for X-Band Transmit/Receive Radar Modules

This work investigates the potential of commercially-available silicon-germanium (SiGe) BiCMOS technology for X-band transmit/receive (T/R) radar modules, focusing on the receiver section of the module. A 5-bit receiver operating from 8 to 10.7 GHz is presented, demonstrating a gain of 11 dB, and average noise figure of 4.1 dB, and an input-referred third-order intercept point (HP3) of -13 dBm, while only dissipating 33 mW of power. The receiver is capable of providing 32 distinct phase states from 0 to 360deg, with an rms phase error < 9deg and an rms gain error < 0.6 dB. This level of circuit performance and integration capability demonstrates the benefits of SiGe BiCMOS technology for emerging radar applications, making it an excellent candidate for integrated X-band phased-array radar transmit/receive modules.

On the Performance Limits of Cryogenically Operated SiGe HBTs and Its Relation to Scaling for Terahertz Speeds

The goal of achieving terahertz (THz) transistors within the silicon material system has generated significant recent interest. In this paper, we use operating temperature as an effective way of gaining a better understanding of the performance limits of SiGe HBTs and their ultimate capabilities for achieving THz speeds. Different approaches for vertical profile scaling and reduction of parasitics are addressed, and three prototype fourth-generation SiGe HBTs are compared and evaluated down to deep cryogenic temperatures, using both dc and ac measurements. A record peak fT/fmax of 463/618 GHz was achieved at 4.5 K using 130-nm lithography (309/343 GHz at 300 K), demonstrating the feasibility of reaching half-THz fT and fmax simultaneously in a silicon-based transistor. The BVCEO of this cooled SiGe HBT was 1.6 V at 4.5 K (BVCBO = 5.6 V), yielding a record fT times BVCEO product of 750 GHzldrV (510 GHzldrV at 300 K). These remarkable levels of transistor performance and the associated interesting device physics observed at cryogenic temperatures in these devices provide important insights into further device scaling for THz speeds at room temperature. It is predicted in a new scaling roadmap that fT/fmax of room-temperature SiGe HBTs could potentially achieve 782/910 GHz at a BVCEO of 1.1 V at the 32-nm lithographic node.

A 2 mW, Sub-2 dB Noise Figure, SiGe Low-Noise Amplifier For X-band High-Altitude or Space-based Radar Applications

This paper presents a low-power X-band low-noise amplifier (LNA) implemented in silicon-germanium (SiGe) technology targeting high-altitude or space-based low-power density phased-array radar systems. To our knowledge, this X-band LNA is the first in a Si-based technology to achieve less than 2 dB mean noise figure while dissipating only 2 mW from a 1.5 V power supply. The gain of the circuit is 10 dB at 10 GHz with an IIP 3 of 0 dBm. In addition to standard amplifier characterization, the LNAs total dose radiation response has been evaluated.

A Lightweight Organic X-Band Active Receiving Phased Array With Integrated SiGe Amplifiers and Phase Shifters

This paper presents for the first time an X-band antenna array with integrated silicon germanium low noise amplifiers (LNA) and 3-bit phase shifters (PS). LNAs and PSs were successfully integrated onto an 8 × 2 lightweight antenna utilizing a multilayer liquid crystal polymer (LCP) feed substrate laminated with a duroid antenna layer. A baseline passive 8×2 antenna is measured along with a SiGe integrated 8×2 receive antenna for comparison of results. The active antenna array weighs only 3.5 ounces and consumes 53 mW of dc power. Successful comparisons of the measured and simulated results verify a working phased array with a return loss better than 10 dB across the frequency band of 9.25 GHz-9.75 GHz. A comparison of radiation patterns for the 8×2 baseline antenna and the 8×2 SiGe integrated antenna show a 25 dB increase in gain (ΔG). The SiGe integrated antenna demonstrated a predictable beam steering capability of ±41°. Combined antenna and receiver performance yielded a merit G/T of -9.1 dB/K and noise figure of 5.6 dB.

An 850 mW X-Band SiGe power amplifier

An 850 mW SiGe power amplifier operating at X-Band (8.5-10.5 GHz) frequencies with over 11 dB of gain and 18% PAE is presented. This SiGe PA was implemented in a commercially-available, third-generation 130 nm 200 GHz SiGe BiCMOS platform using a hybrid high-breakdown / high-speed cascode pair to enhance voltage swing.

A Novel Device Architecture for SEU Mitigation: The Inverse-Mode Cascode SiGe HBT

We investigate, for the first time, the potential for SEE mitigation of a newly-developed device architecture in a 3rd generation high-speed SiGe platform. This new device architecture is termed the ¿inverse-mode cascode SiGe HBT¿ and is comprised of two standard devices sharing a buried subcollector and operated in a cascode configuration. Verification of the TID immunity is demonstrated using 10 keV X-rays, while an investigation of the SEE susceptibility is performed using a 36 MeV 16O ion. IBICC results show strong sensitivities to device bias with only marginal improvement when compared to a standard device; however, by providing a conductive path from the buried subcollector (C-Tap) to a voltage potential, almost all collected charge is induced on the C-Tap terminal instead of the collector terminal. These results are confirmed using full 3-D TCAD simulations which also provides insight into the physics of this new RHBD device architecture. The implications of biasing the C-Tap terminal in a circuit context are also addressed.

Design of Digital Circuits Using Inverse-Mode Cascode SiGe HBTs for Single Event Upset Mitigation

We report on the design and measured results of a new SiGe HBT radiation hardening by design technique called the “inverse-mode cascode” (IMC). A third-generation SiGe HBT IMC device was tested in a time resolved ion beam induced charge collection (TRIBICC) system, and was found to have over a 75% reduction in peak current transients with the use of an n-Tiedown on the IMC sub-collector node. Digital shift registers in a 1st-generation SiGe HBT technology were designed and measured under a heavy-ion beam, and shown to increase the LET threshold over standard npn only shift registers. Using the CREME96 tool, the expected orbital bit-errors/day were simulated to be approximately 70% lower with the IMC shift register. These measured results help demonstrate the efficacy of using the IMC device as a low-cost means for improving the SEE radiation hardness of SiGe HBT technology without increasing area or power.

A two-channel, ultra-low-power, SiGe BiCMOS receiver front-end for X-band phased array radars

We present an ultra-low-power SiGe BiCMOS receiver front-end for X-band phased-array radar systems. The receiver, which consists of two LNAs and a 3-bit phase shifter, consumes only 4 mW of dc power while achieving over 10 dB of gain, less than 5 dB noise figure, and an OTOI of over 10 dBm. In addition, the RMS gain and phase errors were less than 0.5 dB and 2∘, respectively. This design demonstrates possible applications of SiGe HBT technology for use in ultra-low-power radar systems.

A Monolithic 5-Bit SiGe BiCMOS Receiver for X-Band Phased-Array Radar Systems

This work presents a 5-bit receiver for X-band phased-array radar applications based on a commercially-available silicon-germanium (SiGe) BiCMOS technology. The receiver achieves a gain of 11 dB, an operational bandwidth from 8.0 to 10.7 GHz, an average noise figure of 4.1 dB, and an input-referred third-order intercept point (IIP3) of-13 dBm, while only dissipating 33 mW of power. The receiver also provides 32 distinct phase states from 0 to 360deg, with an rms phase error < 9deg. This level of circuit performance and integration capability demonstrates the benefits of SiGe BiCMOS technology for emerging radar applications, making it an excellent candidate for integrated X-band phased-array radar transmit/receive modules.

A New Analytical Method for Robust Extraction of the Small-Signal Equivalent Circuit for SiGe HBTs Operating at Cryogenic Temperatures

We present a new analytical direct parameter-extraction methodology for obtaining the small-signal equivalent circuit of HBTs. It is applied to cryogenically operated SiGe HBTs as a means to allow circuit design of SiGe HBT low-noise amplifiers for cooled radio astronomy applications. We split the transistor into an intrinsic transistor (IT) piece modeled as a Pi-topology, and the quasi-intrinsic transistor (QIT), obtained from the IT after that the base resistance (Rb) has been removed. The relations between Z-Y-parameters of the IT and QIT are then established, allowing us to propose a new methodology for determining Rb. The present extraction method differs from previous studies in that each of the model elements are obtained from exact equations that do not require any approximations, numerical optimization, or post-processing. The validity of this new extraction methodology is demonstrated by applying it to third-generation SiGe HBTs operating at liquid-nitrogen temperature (77 K) across the frequency range of 2-22 GHz.