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This article presents a design for implementing an ultrawideband (UWB) software-defined radar (SDRadar) using a bandwidth reconstruction technique, called frequency stacking, for a stepped frequency signal to create a synthetic wideband waveform (SWW). Practical methods of overcoming traditional limitations of SDRadar and stepped chirp radar are introduced, and the performance is demonstrated using a commercial battery-powered universal software radio peripheral (USRP) software-defined radio (SDR). Application-specific considerations are made and performance tradeoffs are demonstrated. Furthermore, the method is shown to be the coherence solution for otherwise noncoherent low-cost communications’ SDR systems. The proposed design has multiple applications in low-cost, reconfigurable ground-penetrating radar (GPR) and small unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) platforms.

This paper presents a design for implementing an ultra-wideband (UWB) Software Defined Radar (SDRadar) using a bandwidth reconstruction technique for a stepped frequency signal called frequency stacking to create a synthetic wideband waveform (SWW). Practical methods of overcoming traditional limitations of SDRadar and stepped chirp radar are introduced and performance is demonstrated using a commercial battery-powered Universal Software Radio Peripheral (USRP) Software Defined Radio (SDR). Application-specific considerations are made and performance trade-offs are demonstrated. The pro­posed design has multiple applications in low-cost, reconfigurable Ground Penetrating Radar (GPR) and small unmanned aerial vehicle (UAV) Synthetic Aperture Radar (SAR) platforms.

The impact of single event transients (SETs) on single-pole double-throw (SPDT) RF switch circuits designed in a commercially-available, 180 nm second-generation SiGe BiCMOS (IBM 7HP) technology is investigated. The intended application for these SPDT RF switches requires a 1 GHz to 20 GHz band of operation, relatively low insertion loss ( 15 dB at 20 GHz). Two-photon absorption experiment results reveal that the SPDT switches are vulnerable to SETs due to biasing effects as well as the triple-well (TW) nFETs, which are found to be more sensitive to SETs than bulk nFETs. From these results, potential implications are discussed and mitigation strategies are proposed. To verify one of the proposed mitigation techniques, SPDT switches were also designed in a 180 nm twin-well SOI CMOS (IBM 7RF-SOI) technology. A different biasing technique is implemented to help improve the SET response. The fabricated SOI SPDT switches achieve an insertion loss of 21 dB isolation at 20 GHz. For this circuit, no transients were observed even at very high laser energies (≈ 5 nJ).

To the author's knowledge, this work represents the first demonstration of an X-band integrated 64-element active phased-array receiver using SiGe and organic multilayer (LCP + Duroid) technologies. The design and measurement of the antenna, SiGe T/R module, and integrated subarray antenna were presented. In addition, the design of the FPGA digital control board was also presented, which enabled beam steering and control of the phase shifters. This receive subarray was designed for use in SCLP applications and meets performance, cost, and size requirements for use with compact platforms, such as UAVs.

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.

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.

We investigate the applicability of current total ionizing dose (TID) test protocols in the context of advanced transistor technologies such as Silicon-Germanium heterojunction bipolar transistors(SiGe HBTs). In SiGe HBTs, an unexpected shift in collector current is observed during total dose irradiation. Using both device and circuit measurements, we investigate this phenomenon and assess its potential importance in hardness assurance of SiGe components. TCAD simulations were performed to explain the observed current shifts.

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.

We report the first irradiation results on high-frequency SiGe HBT and CMOS phase shifters for space-based, phased-array antennas used in radar or wireless communication systems. Both phase shifter circuits remain functional with acceptable dc and RF performance up to multi-Mrad proton exposure, and are thus suitable for many orbital applications. In addition, simulation results probing the limits of phase shifter performance in a radiation environment are presented. These results show that both CMOS and SiGe HBT based phase shifters can be used for space-based applications without any specific radiation hardening techniques.

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.

This work presents the design and measured results of a fully integrated switched power two-stage GaN HEMT high-power amplifier (HPA) achieving 60% power-added efficiency at over 120Woutput power. This high-efficiency GaN HEMT HPA is an enabling technology for L-band SweepSAR interferometric instruments that enable frequent repeat intervals and high-resolution imagery. The L-band HPA was designed using space-qualified state-of-the-art GaN HEMT technology. The amplifier exhibits over 34 dB of power gain at 51 dBm of output power across an 80 MHz bandwidth. The HPA is divided into two stages, an 8 W driver stage and 120 W output stage. The amplifier is designed for pulsed operation, with a high-speed DC drain switch operating at the pulsed-repetition interval and settles within 200 ns. In addition to the electrical design, a thermally optimized package was designed, that allows for direct thermal radiation to maintain low-junction temperatures for the GaN parts maximizing long-term reliability. Lastly, real radar waveforms are characterized and analysis of amplitude and phase stability over temperature demonstrate ultra-stable operation over temperature using integrated bias compensation circuitry allowing less than 0.2 dB amplitude variation and 2° phase variation over a 70°C range.

We report results on the cryogenic operation of two different monolithic X-band silicon-germanium (SiGe) heterojunction bipolar transistor low noise amplifiers (LNAs) implemented in a commercially-available 130 nm SiGe BiCMOS platform. These SiGe LNAs exhibit a dramatic reduction in noise temperature with cooling, yielding Teff of less than 21 K (0.3 dB noise figure) across X-band at a 15 K operating temperature. To the authors’ knowledge, these SiGe LNAs exhibit the lowest broadband noise of any Si-based LNA reported to date.

This work describes the development of a high-power amplifier for use with a remote sensing SAR system. The amplifier is intended to meet the requirements for the SweepSAR technique for use in the proposed DESDynI SAR instrument. In order to optimize the amplifier design, active load-pull technique is employed to provide harmonic tuning to provide efficiency improvements. In addition, some of the techniques to overcome the challenges of load-pulling high power devices are presented. The design amplifier was measured to have 49 dBm of output power with 75% PAE, which is suitable to meet the proposed system requirements.

This work presents a measurement system to characterize the pulsed response of high-power GaN amplifiers for use in space-based SAR platforms that require very strict amplitude and phase stability. The measurement system is able to record and analyze data on three different time scales: fast, slow, and long, which allows for greater detail of the mechanisms that impact amplitude and phase stability. The system is fully automated through MATLAB, which offers both instrument control capability and in-situ data processing. To validate this system, a high-power GaN HEMT amplifier operated in saturation was characterized. The fast time results show that variations to the amplitude and phase are correlated to DC supply transients, while long time characteristics are correlated to temperature changes.

The higher output power densities required of modern radar architectures, such as the proposed DESDynI [Deformation, Ecosystem Structure, and Dynamics of Ice] SAR [Synthetic Aperture Radar] Instrument (or DSI) require increasingly dense high power electronics. To enable these higher power densities, while maintaining or even improving hardware reliability, requires improvements in integrating advanced thermal packaging technologies into radar transmit/receive (TR) modules. New materials and techniques have been studied and are now being implemented side-by-side with more standard technology typically used in flight hardware.

This work presents a new measurement technique, mixed-signal active harmonic load-pull (MSALP) developed by Anterverta-mw in partnership with Maury Microwave, that allows for wide-band ultra-high efficiency amplifiers to be designed using GaN technology. An overview of the theory behind active load-pull is presented and why load-pull is important for high-power device characterization. In addition, an example procedure is presented that outlines a methodology for amplifier design using this measurement system. Lastly, measured results of a 10W GaN amplifier are presented. This work aims to highlight the benefit of using this sophisticated measurement systems for to optimize amplifier design for real radar waveforms that in turn will simplify implementation of space-based radar systems

The SweepSAR architecture for space-borne remote sensing applications is an enabling technology for reducing the temporal baseline of repeat-pass interferometers while maintaining near-global coverage. As part of this architecture, real-time digital beam-forming would be performed on the radar return signals across multiple channels. Preserving the accuracy of the combined return data requires real-time calibration of the transmit and receive RF paths on each channel. This paper covers several of the design considerations necessary to produce a practical implementation of this concept. (6 pages)

An ultra-low voltage, monolithic 9 GHz (X-band) low noise amplifier has been implemented in 0.13 µm SiGe BiCMOS technology. The SiGe HBTs were intentionally biased in weak saturation (V CE at 0.5 V). This allows the LNA to operate at 300 K using only 2.4 mW of dc power from a 1 V supply, while delivering 16.7 dB gain and 3.5 dB noise figure at 9 GHz. At 90 K, this SiGe LNA achieves 17.5 dB of gain at only 600 µW of power, record performance for any known X-band LNA operating at sub-ambient temperatures.

Commercially available devices fabricated from GaN are beginning to appear from a number of different suppliers. In this initial study of the radiation tolerance of commercial GaN devices, several device types from several suppliers were chosen. Three different studies were performed: 1) a preliminary DDD/TID test of a variety of part types was performed by irradiating with 55 MeV protons, 2) a detailed DDD/TID study of one particular part type was performed by irradiating with 55 MeV protons, and 3) a SEB/SEGR test was performed on a variety of part types by irradiating with heavy ions. No significant degradation was observed in any of the tests performed in this study.

For the first time, a transmit-receive (TR), 64-element phased array fully driven by Silicon Germanium (SiGe) integrated circuits and implemented on organic substrates is demonstrated at 9.5GHz. The array was realized on a duroid and liquid crystal polymer substrate stack-up. The radiating elements are driven by SiGe-based TR modules and power amplifiers. Additionally, radio-frequency micro-electromechanical switches allow the toggled operation between transmit and receive modes. Measurements showed an average TR operation bandwidth of 2.55GHz, an azimuthal TR beam-steering range of ±26°, a receive gain of 27.28dB and an estimated output power of 41.33dBm.

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.

We report heavy-ion microbeam and total dose data for a new complementary (npn + pnp) SiGe on thick-film SOI technology. Measured transient waveforms from heavy-ion strikes indicate a significantly shortened single-event-induced transient current, while maintaining the total dose robustness associated with SiGe devices. Heavy-ion broad-beam data confirm a reduced single event upset (SEU) cross-section in a high-speed shift register circuit.

For the first time, a large-signal RF stress study of complementary (npn + pnp) SiGe HBTs on thick-film SOI is performed, and analyses based on device physics are presented, shedding light on the observed failure mechanisms of these C-SiGe HBTs at very high RF input power. Two types of npn SiGe HBTs, low-breakdown voltage (LVNPN) and high-breakdown voltage (HVNPN) devices, as well as a high-breakdown voltage pnp SiGe HBT (HVPNP) in a 250 nm C-SiGe on SOI process are investigated. It is shown that the HVPNP can withstand aggressive RF stress for longer periods of time, compared with the LVNPN and the HVNPN, which succumb to several interesting modes of catastrophic device failure. A case is made for the use of pnp SiGe HBTs in sensitive RF front-ends that may be exposed to non-limited high RF power due to leakages in the transmit/receive (T/R) path or RF reflections.

We present measured results and analysis from high-power testing of three different X-band SiGe HBT LNAs. The custom measurement setup allowed high RF power (up to 32 dBm) to be applied to the input of the LNAs for 400 sec. During the stressing, the bias current was monitored and the pre/post-stress dc and ac characteristics were measured. The results indicate that, in the three LNAs tested, catastrophic failures can occur at these high powers, while at lower input power (less than 30 dBm), the LNA gain is degraded. Analysis shows that during the stressing, the collector current density inside the transistors increases enough to damage the device, in a manner similar to that experienced during mixed-mode reliability stress.

This paper presents a novel test setup for characterizing intermodulation distortion in advanced devices and circuits. The setup uses a network analyzer to measure power levels of the fundamental and IM3 products for a two-tone input. It is shown that if the power calibration is correctly performed, the intermodulation distortion terms from a power sweep give the correct value of the input-referred third-order intercept point (IIP3). MOSFETs in a commercially-available 0.13 µm SiGe BiCMOS technology were measured across bias to validate the measurement approach. The results were subsequently validated using harmonic balance simulations based on design-kit compact models.

This paper presents an L-band silicon-germanium (SiGe) low-noise amplifier (LNA) for use in Global Positioning System (GPS) receivers. Implemented in a 200 GHz SiGe BiCMOS technology, the LNA occupies 1 × 1 mm2 (including the bondpads). The SiGe LNA exhibits a gain greater than 23 dB from 1.1 to 2.0 GHz, and a noise figure of 2.7 to 3.3 dB from 1.2 to 2.4 GHz. At 1.575 GHz, the 1-dB compression point (P 1dB ) is 1.73 dBm, with an input third-order intercept point (IIP3) of −3.98 dBm.

We present a novel device structure using an inverse-mode, cascoded (IMC) SiGe HBT for improved tolerance of heavy ion irradiation. The cascoded SiGe device consists of a forward-mode, common-emitter SiGe HBT cascoded with a common-base inverse-mode SiGe HBT, with the subcollector region of the two devices shared. The device was fabricated in both first and third-generation, commercially-available SiGe HBT technologies. The third-generation IMC device was measured to have over 20 dB of current gain and over 30 dB of power gain at 10 GHz. In addition, the measured total dose radiation response and simulated current transients are presented. These results demonstrate the potential use of these devices in high-speed circuits intended for operation in space or other extreme environments.

The RF safe-operating-area of a variety of both bulk and thick-film SOI SiGe HBTs SiGe has been investigated using DC and pulsed-mode output characteristics, as well as RF gain and linearity measurements. SOI SiGe HBTs are found to suffer more from self-heating than bulk devices under DC operating conditions, as expected, due to their naturally higher thermal resistance. However, in terms of RF performance, operation of SiGe HBTs on SOI beyond the traditionally-defined safe-operating-area showed only minor degradation in RF metrics, and improved RF linearity. High-injection phenomena are suggested as possible explanations for the observed suppression of self-heating-induced degradation and thermal runaway in these SiGe HBTs on SOI operating under RF operating conditions.

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 novel PNM textile with extremely small thickness on the order of a few micron was characterized at millimeter wave frequencies (26.5 – 40 GHz), and the impedance analysis of the material was presented. The results show that the PNM is an excellent absorber for wideband applications; the highly polarized materials can be utilized for polarization detection and sensing applications. The impedance results of the PNM textile show that CNTs can function as resonators at microwave frequencies due to the long nanotubes, hence, paving ways for further theoretical and experimental studies on these behaviors. In future research efforts, the PNM will be characterized in gas to establish a foundation for wireless gas sensor designs in the microwave frequency range.

We investigate the reliability of RF switches for high-power, high dynamic range RF applications. Switches in two different CMOS technology platforms (180 nm and 130 nm) were observed to fail catastrophically beyond 33 dBm RF input power. The switches were single-pole double-throw with series-shunt topology. The reliability of a standalone switching series transistor from a single-pole double-throw switch was analyzed to investigate the failure mechanisms involved. Gate dielectric breakdown at high RF input power is demonstrated to lead to the failure of RF switches. Finally, the effect of transistor failure on switch operation is discussed.

We present a high-dynamic range (HDR) X-band LNA implemented in silicon-germanium (SiGe) technology tar- geting high-performance radar and wireless communications applications. To our knowledge, this is the first Si-based LNA to achieve over 30 dB gain, 30 dBm of OTOI, and 2 dB noise figure at X-band. System-level performance simulations clearly show the benefits of using HDR LNAs in the receive chain. The performance of this SiGe HDR LNA compares very favorably with other state-of-the-art LNAs, highlighting the capabilities of SiGe technology for these types of applications. and less than 2 dB noise figure. Due to these demanding requirements, both a small-signal and large-signal amplifier design methodology was used to design this high-dynamic range (HDR) LNA. The LNA was fabricated in a SiGe BiCMOS platform (IBM 8HP) utilizing SiGe HBTs with an fT/fmax of 200/280 GHz (3). In this paper, we present the results from the first-ever reported SiGe X-band LNA to achieve 30 dBm of OTOI, 30 dB of gain, with 2 dB of noise figure. Section II highlights the hybrid LNA design approach. Section III reports the measured results, while Section IV analyzes these results in the context of a radar system and benchmarks these results against other LNAs, followed by a summary.

This work presents a comparison of three single-pole double-throw (SPDT) nMOS RF switches implemented in commercially available Si-based 180, 130, and 90 nm technologies. In addition, a new series-shunt switch is presented that offers a means to improve switch isolation. Measured results of these RF switches demonstrates how technology node scaling impacts RF switch design and provides insight into the complicated trade-offs between insertion loss, isolation, and linearity.

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.

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.

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 LNA's total dose radiation response has been evaluated.