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This paper presents a wideband, low insertion loss, high attenuation range digital step attenuator (DSA) implemented using SiGe HBTs. In a switched-type topology, the off-state capacitances (COFF) in both reference and attenuation states cause different poles and zeros, which trigger amplitude and phase errors and limit the operating bandwidth. To achieve wide bandwidth, methods to relocate poles and zeros to the highest possible frequencies in both states are investigated. In the reference state, minimizing the size of the shunt switching transistors extends the bandwidth. In the attenuation state, switching in a capacitor at the base of an anti-parallel (AP) SiGe HBT pair series switch reduces the effective COFF, enhancing the bandwidth. The proposed techniques facilitate the realization of a 16-dB attenuator cell to support wide bandwidth and offer lower insertion loss than conventional cascaded 8-dB cell designs. Fabricated in 130-nm SiGe BiCMOS technology, the proposed DSA with an attenuation range of 31.5 dB in 0.5 dB steps operates from DC to 67 GHz and achieves an insertion loss lower than 7.8 dB. The RMS amplitude error is less than 0.4 dB above 1 GHz, while the RMS phase variation is less than 13.1∘.

This letter presents new wideband single-pole double-throw (SPDT) RF switches utilizing SiGe heterojunction bipolar transistors (HBTs) for both series and shunt switches. SiGe HBT, when used as a series switch, exhibits small parasitic components compared to bulk CMOS, which improves insertion loss at high frequency and supports wider bandwidth. For a series switch, three configurations are proposed: using the collector as an input (CI), using the emitter as an input (EI), and using a combination of the two in an antiparallel (AP) fashion. While all three configurations exhibit similar performance, the SPDT switch with the EI SiGe HBT exhibits the best insertion loss and isolation achieving dc-to-above 110-GHz bandwidth, 2.5 dB of insertion loss, and 27.3 dB of isolation at 60 GHz. The SPDT switch with AP SiGe HBT pair exhibits the highest linearity, with 15.6 dBm of input 1-dB compression point (IP 1 dB) at 10 GHz. With 0.61 mW of power dissipation, these new SPDT switches using SiGe HBTs exhibit similar performance to silicon-on-insulator (SOI) CMOS while obtaining higher power capability among conventional series-shunt SPDT designs.

The cryogenic performance of radiation-hardened radio-frequency (RF) low-noise amplifiers (LNAs) is presented. The LNA, which was originally proposed for the mitigation of single-event transients (SETs) in a radiation environment, uses inverse-mode silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) in its core cascode stages. In this prototype, the upper common-base SiGe HBT is configured in inverse mode for balanced RF performance and reduced SET sensitivity. In order to better exploit the inverse-mode LNAs in a variety of extreme-environment applications, the RF performance of the LNA was characterized using liquid nitrogen to evaluate cryogenic operation down to 78 K. While the SiGe LNA exhibits acceptable RF performance for all temperature conditions, there is a noticeable gain drop observed at 78 K compared to the conventional forward-mode design. This is attributed to the limited high-frequency performance of an inverse-mode SiGe HBT. As a guideline, compensation techniques, including layout modifications and profile optimization, are discussed for the mitigation of the observed gain degradation.

This paper presents a new, wideband digital step attenuator (DSA) implemented using SiGe HBTs. The vertical profile of the SiGe HBT presents small parasitic shunt capacitance and, thus, the loss from the switches in a switched-type attenuator is significantly reduced. For a 6-bit DSA covering a maximum attenuation of 31.5 dB with 0.5 dB steps, reduced T-type cells with reverse-saturated SiGe HBTs are used for low attenuation cells and switched pi-type cells with novel anti-parallel (AP) SiGe HBT pair series switches are used for high attenuation cells. In addition to the symmetry of the AP SiGe HBT pair, reduced T-type and switched pi-type cells are placed alternately to distribute parasitic components and to achieve better overall symmetry. As a result, state-of-the-art performance is achieved over a wide bandwidth, from DC-to-60 GHz, with an insertion loss of 7.5 dB at 50 GHz, 31.5 dB of attenuation range and less than 2.8 mW of power consumption.

Total ionizing dose (TID) effects are evaluated for a high-voltage (>30 V) complementary SiGe on SOI technology. Devices are irradiated with 10-keV X-rays at doses up to 5 Mrad(SiO2). The results depend strongly on collector-to-emitter bias, in both forward- and inverse-mode. An anomalous reduction in current gain at high injection in forward-mode operation is observed at doses >500 krad(SiO2). Calibrated 2-D TCAD simulations suggest that this high injection phenomenon is primarily due to interface traps near the STI/Si interface, which is exhibited as a collector resistance increase in the forward Gummel characteristics. Additionally, a strong collector doping dependence is observed, which indicates that this is primarily driven by the thick and lightly doped collector used in this technology. These results illustrate, that high concentrations of interface traps at the STI can have a strong impact on the forward-mode TID response of SiGe HBTs.

The single-event transient (SET) response of the pre-amplification stage of two latched comparators designed using either npn or pnp silicon-germanium heterojunction bipolar transistors (SiGe HBTs) is investigated via two-photon absorption (TPA) carrier injection and mixed-mode TCAD simulations. Experimental data and TCAD simulations showed an improved SET response for the pnp comparator circuit. 2-D raster scans revealed that the devices in the pnp circuit exhibit a reduction in sensitive area of up to 80% compared to their npn counterparts. In addition, by sweeping the input voltage, the sensitive operating region with respect to SETs was determined. By establishing a figure-of-merit, relating the transient peaks and input voltage polarities, the pnp device was determined to have a 21.4% improved response with respect to input voltage. This study has shown that using pnp devices is an effective way to mitigate SETs, and could enable further radiation-hardening-by-design techniques.

The development of a multi-channel, high-power C-band (4.5 - 6.5 GHz) transmit/receive (T/R) module line replaceable unit (LRU) that leverages innovative multifunction monolithic microwave integrated circuits (MMICs) and commercial-off-the-shelf (COTS) components is presented here. These multifunction MMICs provide core RF functionality for the purpose of reducing design complexity, form-factor/area, and cost per channel. A wideband Vivaldi antenna was designed, fabricated, and tested to enable the demonstration of an integrated multi-channel (8), high-power RF personality. The integrated RF personality includes a 12-element linear array (only 8 of the 12 elements are excited), the T/R modules, all supporting bias circuitry, digital control, and thermal management. In transmit mode, each channel has the capability to output up to 25 W in continuous wave (CW) operation.

This paper investigates single-event effects in a W-Band (75-110 GHz) SiGe HBT down-conversion mixer intended for use in a space-based remote sensing radar system. Transient pulse propagation to the output of the mixer as a linear time variant system is analyzed theoretically. This study facilitates the understanding of transient propagation in RF receivers. Device- and circuit-level simulations were conducted to verify the results of the proposed theory. A two photon absorption laser was used to induce transients on different SiGe HBTs within the circuit to assess the impact of SETs on performance. This study shows that significant transients can be produced at the output of the mixer, which can potentially corrupt the received data or received pulse of the radar. It is shown that a differential double-balanced structure can effectively eliminate some of the transients at the output of the mixer. To the authors' best knowledge this is the first study of single event transients conducted on a millimeter-wave SiGe circuit.

The single event effect (SEE) response of devices and differential pairs in a 32-nm SOI CMOS technology is explored using laser-induced carrier injection and TCAD simulations. Both nFETs and pFETs in this technology exhibit similar sensitive area to laser-induced SEE and are strongly dependent on the drain bias condition. TCAD simulations were conducted in order to confirm results and utilize a 3-D mixed-mode simulation approach to more accurately model testing conditions. The differential pair (diff. pair) circuit SEE response extends the discussion to include the use of these devices in a core analog/RF circuit block. The analysis includes the use of floating body (FB) and body-connected (BC) devices. Body-connected FETs tend to exhibit a transient response that is much shorter in duration when compared directly to its floating body counterpart.

Large-signal ( $P_{\rm 1\,dB}$ ) and small-signal (OIP3) radio frequency (RF) linearities of silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) fabricated in a new fourth-generation 90-nm SiGe BiCMOS technology operating at cryogenic temperatures are investigated. The SiGe BiCMOS process technology has an $f_{T}$ / $f_{\rm max}$ of 300/350 GHz. SiGe HBTs with two different layout configurations, collector-base-emitter (CBE) and CBE-base-collector (CBEBC), were characterized over temperature. Both dc and ac figures-of-merit are presented to aid in understanding the linearity, and to provide an overall performance comparison between the two layout configurations. The extracted peak $f_{T}$ / $f_{\rm max}$ for CBE and CBEBC at 78 K are 387/350 and 420/410 GHz, respectively. The $P_{\rm 1\,dB}$ and OIP3 linearity metrics for both configurations are comparable. Source- and load-pull measurements were performed at each temperature at 8 and 18 GHz, with the devices biased at a $J_{C}$ of 18 mA/ $\mu \text{m}^{2}$ . Two-tone measurements over bias were also performed at 300 and 78 K with 50- $\Omega $ terminations for the source and load impedances. The 50 $\Omega $ results follow a similar response to the source- and load-pull measurements at 300 and 78 K, and demonstrate that the small-signal linearity of the SiGe HBTs is not adversely impacted by operation at cryogenic temperatures. The CBEBC configuration demonstrated the most consistent RF linearity performance at cryogenic temperature out of the two layout options.

We investigate the effects of total ionizing dose (TID) on a Gaussian pulse generator implemented in IBM's new 9HP SiGe BiCMOS platform, which combines 300 GHz fT SiGe HBTs and 90 nm CMOS. Total dose effects were examined using a 10-keV X-ray source. The effects of TID on the performance of the pulse generator were investigated with the pulse generator exhibiting a tpw variation of less than 7% for total dose of up to 3.0 Mrad. This circuit is intended for low-power autonomous high-altitude and space-based imaging radars.

The single-event transient (SET) response of a third-generation bulk C-SiGe ( npn + pnp) BiCMOS platform is investigated for the first time. Pulsed-laser, two-photon absorption experiments show that the pnp SiGe heterojunction bipolar transistor (SiGe HBT) exhibits a significant reduction in sensitive area as well as an improved transient response compared with the npn SiGe HBT. Ion-strike simulations on 3-D TCAD, C-SiGe HBT models agree with experimental findings, showing a reduction in overall transient duration and collected charge for the pnp SiGe HBT. These improvements in device-level SETs are attributed to the n-well isolation layer present in the vertical material stack of the pnp HBT. These results suggest that precision analog, RF/mm-wave, and high-speed digital applications utilizing unhardened, high-performance bulk pnp SiGe HBTs should benefit from an inherently improved SEE response.

The total ionizing dose response of 4th-generation SiGe HBTs is assessed at both low and high dose rates to evaluate enhanced low dose rate sensitivity (ELDRS) in a new SiGe BiCMOS technology. Both device and circuit results are presented. A bandgap reference circuit topology is chosen to monitor for ELDRS in TID-induced collector current shifts, which have previously been reported in low dose rate studies of SiGe HBTs. The results in this paper also cover previous technology generations from this foundry in order to incorporate a broader view of dose rate effects in SiGe HBTs. No indication of ELDRS was found in any technology generation.

An 8-18 GHz receiver implemented in silicon-germanium (SiGe) BiCMOS technology is presented. The receiver is designed to enable built-in test (BIT) and consists of a low noise amplifier (LNA), an image-reject mixer, on-chip, automatic gain control (AGC), ring oscillator (RO) sources (used to provide test signals of a predefined amplitude), and digital-to-analog converters (DACs), used for DC bias control of the blocks. The voltage and current biases of both the LNA and the mixer circuit blocks are used as tuning knobs for radio frequency (RF) performance metrics to mitigate the negative effects of total ionizing dose (TID) radiation damage present in extreme environments such as space. Samples of the receiver die were exposed to 10 keV X-rays at 1, 3, and 6 Mrad( SiO2) doses. The BIT system was able to mitigate for TID damage in most cases, with improvements in the key RF metrics of gain, output third-order intercept point (OIP3), and noise figure (NF). The receiver was fabricated in an 0.18 μm SiGe BiCMOS process technology with a peak fT of 150 GHz and nominally consumes 241-243 mA from a 4 V supply.

This paper presents an investigation of the impact of single-event transients (SETs) and total ionization dose (TID) on precision voltage reference circuits designed in a fourth-generation, 90-nm SiGe BiCMOS technology. A first-order uncompensated bandgap reference (BGR) circuit is used to benchmark the SET and TID responses of these voltage reference circuits (VRCs). Based on the first-order BGR radiation response, new circuit-level radiation-hardening-by-design (RHBD) techniques are proposed. An RHBD technique using inverse-mode (IM) transistors is demonstrated in a BGR circuit. In addition, a PIN diode VRC is presented as a potential SET and TID tolerant, circuit-level RHBD alternative.

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).

This paper uses charge deposition by two-photon absorption to present the first investigation of the physical mechanisms underlying the single event transient (SET) response of cascode structures in a 45-nm RF-CMOS/SOI technology, provides the first experimental comparison of SET between 45-nm and 32-nm RF-CMOS/SOI devices, and presents implications for circuit design in both technologies. This work leverages a number of different device types and is supported by calibrated TCAD simulations.

The single-event effect sensitivity of fourth-generation, 90 nm SiGe HBTs is investigated. Inverse-mode, ≥1.0 Gbps SiGe digital logic using standard, unoptimized, fourth-generation SiGe HBTs is demonstrated and the inverse-mode shift register exhibited a reduction in bit-error cross section across all ion-strike LETs. Ion-strike simulations on dc calibrated, 3-D TCAD SiGe HBT models show a reduction in peak current transient magnitude and a reduction in overall transient duration for bulk SiGe HBTs operating in inverse mode. These improvements in device-level SETs are attributed to the electrical isolation of the physical emitter from the subcollector-substrate junction and the high doping in the SiGe HBT base and emitter, suggesting that SiGe BiCMOS technology scaling will drive further improvements in inverse-mode device and circuit-level SEE. Two-photon absorption experiments at NRL support the transient mechanisms described in the device-level TCAD simulations. Fully-coupled mixed-mode simulations predict large improvements in circuit-level SEU for inverse-mode SiGe HBTs in multi-Gbps, inverse-mode digital logic.

The effects of 63 MeV proton irradiation on the RF performance (insertion loss, isolation, and linearity) of triple-well nFET-based RF switches designed in a 130 nm SiGe BiCMOS technology are investigated. The switches were designed for wide-band operation (1 to 40 GHz) and were required by the application to achieve high isolation (> 35 dB at 40 GHz) with moderate insertion loss (dB at 40 GHz). The RF switch IL improves (S21 increases) at 100 and 500 krad(SiO2), but degrades (S21 decreases) at 2 Mrad(SiO2). P1dB and IIP3 (switch linearity) shows a similar TID response, at 100 and 500 krad(SiO2) dose an increase of ~ 0.4 dBm and ~0.2 dBm, respectively. However, at 2 Mrad(SiO2) both sharply decrease. Standalone RF and dc structures were also irradiated to better understand the underlying mechanisms affecting the switch RF performance. The bias dependence of the radiation-induced change on the measured RF performance of a SPST switch is also analyzed. 10 keV X-ray radiation experiments were conducted on separate dc transistor structures to provide additional insight into the measured impact of total ionization dose on the performance of RF switches.

We demonstrate record ac performance (0.8 THz) for a silicon-germanium heterojunction bipolar transistor (SiGe HBT) operating at cryogenic temperatures. An extracted peak fMAX of 798 GHz (peak fT of 479 GHz) at 4.3 K was measured for a device with a BVCEO of 1.67 V. This scaled SiGe HBT also exhibits excellent thermal properties, as required from an electro-thermal reliability perspective. Taken together, these results strongly suggest that at the limits of scaling, robust, and manufacturable SiGe HBTs designed for room temperature operation are likely to achieve THz speeds.

Low-loss, wideband (DC to 40 GHz) single-pole double-throw (SPDT) RF switches implemented in a 180 nm SOI CMOS technology are presented. A π-matching network is implemented to improve the insertion loss (IL) at high frequencies. The differences between the conventional inductive peaking and the matching network utilized here are discussed. Under nominal conditions, the IL of the 1.5 V switch is less than 0.5 dB from DC to 20 GHz; and less than 2.0 dB at 40 GHz. The input matching of the switch is better than 10 dB, the isolation (ISO) is greater than 15 dB, and the P 1dB of the 1.5 V switch is 11 dBm. A higher voltage (2.5 V) switch implemented with high-breakdown devices increases the P 1dB to 15 dBm at the cost of a small increase in IL. A switched-line one-bit 180° phase shifter (PS) is demonstrated using the 1.5 V low-loss switch. The PS exhibits an IL better than 3 dB at 18 GHz. The advantages of implementing a low-loss switch in a 180 nm technology are discussed.

An integrated wideband (6–20 GHz) image-reject mixer and test signal source for "self-healing" of image-rejection ratio (IRR) is demonstrated for the first time. The mixer can be adapted to deliver consistent performance over process variations, environmental changes, and/or aging effects. An IRR of over 36 dB is obtained in measurement for a wide range of IF frequencies. The healing is achieved by means of an automated procedure controlled by MATLAB algorithms. The test signal source consists of an on-die wideband differential ring oscillator with an amplitude-control mechanism to provide a 20 dB range of adjustable power at the input of the mixer. The circuits were fabricated in a commercially-available 180 nm SiGe BiCMOS platform.