Moon-Kyu Cho

An Investigation of the Use of Inverse-Mode SiGe HBTs as Switching Pairs for SET-Mitigated RF Mixers

The capability of inverse-mode (IM) silicon- germanium (SiGe) heterojunction bipolar transistors (HBTs) for the mitigation of single-event transients (SETs) under large-signal operation was investigated in an RF down-conversion single- balanced mixer using a through-wafer, two-photon absorption pulsed-laser beam experiment and TCAD heavy-ion simulations. The IM SiGe HBTs replace conventional forward-mode (FM) SiGe HBTs in the differential pair, which provides full current steering for frequency mixing operation. Under steady-state conditions, the IM SiGe HBT differential pair exhibits smaller transient peaks with shorter durations compared to the FM SiGe HBTs. In addition, under the injection of a local oscillator (LO) signal with large swing, the IM SiGe HBTs show faster recovery (50% reduction in the best case) from the impact of SETs. In the frequency domain, it is observed that IM SiGe HBTs produce less distortion at the output for an intermediate frequency below 1 GHz. Based on the performance comparison between FM and IM SiGe HBT down-conversion mixers, system design guidelines to compensate the noise figure degradation associated with using IM SiGe HBTs are discussed.

Optimization of SiGe HBT RF Switches for Single-Event Transient Mitigation

Single-event transient (SET)-hardened SiGe HBT RF single-pole single-throw (SPST) switches were designed and fabricated for the first time. TCAD-based heavy-ion simulations and two-photon absorption (TPA) laser-induced beam experiments were used to optimize the switch core configuration for SET mitigation. Among different configurations, the reverse-connected series and shunt device core, where both emitter terminals are connected to the output, exhibits the smallest transient peaks and shortest durations at the output terminal of the switch. Based on this finding, the design considerations for maximizing the RF performance of SiGe HBT SPST RF switches are discussed. In addition, a comparison of the SET response and RF performance of CMOS (nFET) SPST and SiGe HBT SPST switches provides additional information on the trade-offs in the SET mitigation strategy and potential RF capabilities.

A SiGe-BiCMOS Wideband (2–22 GHz) Active Power Divider/Combiner Circuit Supporting Bidirectional Operation

A power divider/combiner circuit, which simultaneously achieves wide bandwidth, flat gain characteristics, and bidirectional operation, is proposed for multichannel broadband system applications. The proposed circuit utilizes cascode-based bidirectional amplifier cores, which steer the operation modes between a divider and a combiner depending on the control input, and a two-stage distributed-amplifier topology with artificial transmission lines. Implemented in a 130-nm silicon-germanium BiCMOS technology platform, the proposed divider/combiner provides the advantage of seamless integration with digital control blocks. The power divider/combiner exhibits the flat in-band gain of 9 dB and the operational bandwidth of 2-22 GHz, which covers S-, C-, X-, and Ku-bands. In addition, it shows the amplitude imbalance of 0.8 dB, the phase imbalance of 3.5°, the port-to-port isolation of 22 dB, the output 1-dB compression point of 3 dBm, and good impedance matching under 100-mW dc power consumption.

The Use of Inverse-Mode SiGe HBTs as Active Gain Stages in Low-Noise Amplifiers for the Mitigation of Single-Event Transients

A cascode configuration with inverse-mode (IM) common-emitter silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) is proposed for the mitigation of single-event transients (SETs) in low-noise amplifiers (LNAs). Conventionally, despite their SET-mitigation capability, IM SiGe HBTs have been considered to be unsuitable for active gain stages due to severe degradation in RF performance. However, with the benefits of aggressive technology scaling, the high frequency performance of IM SiGe HBTs has been significantly improved, thereby enabling them to be utilized in active gain stages with acceptable RF performance. The cascode with IM common-emitter and common-base SiGe HBTs is used for a 2.4 GHz prototype LNA and it achieves adequate RF gain (10 dB) and noise figure (1.9 dB). With regard to SET mitigation, a through-wafer two-photon absorption pulsed-laser experiment is conducted to test the efficacy of this radiation-hardening approach in an advanced 90 nm SiGe BiCMOS platform. The proposed IM-SiGe-HBT-based LNA exhibits 85% reduction in transient peaks compared to the conventional forward-mode cascode LNA.

A 2–22 GHz wideband active bi-directional power divider/combiner in 130 nm SiGe BiCMOS technology

An active bi-directional power dividier/combiner circuit based on a distributed topology is proposed. The use of bi-directional amplifiers (BDAs) provides both dividing and combining functions within the same circuit. By utilizing a distributed topology composed of BDAs and artificial transmission lines, a wide operational bandwidth (2-22 GHz) and a large, flat power gain (9 dB) were achieved under DC power consumption of 100 mW. The maximum amplitude and phase imbalances were 0.7 dB and 3°, respectively.

A Compact, Active SiGe Power Divider With Multi-Octave Bandwidth

This letter proposes a wideband active power divider, which realizes multi-octave bandwidth with positive, flat gain, and good isolation. By combining a single stage amplifier with artificial transmission lines and emitter-follower (EF) output stages, a broadband operational bandwidth (2.5-23.0 GHz) and flat gain response (8.8-11.8 dB) with a small chip size are achieved while maintaining good isolation (>25 dB) between the output ports. The measured noise figures (NFs) of the two forward paths are lower than 9 dB, the output P1dB (OP1dB) is greater than -9 dBm and the output IP3 (OIP3) is greater than 0 dBm over the 3 dB bandwidth. The maximum amplitude and phase imbalances of the two output ports are 0.2 dB and 1.6 degrees, respectively. The core area of the active power divider is 0.62 × 0.50 mm2. The active power divider consumes 20 mA from a 3.3 V DC supply.

A bi-directional, X-band 6-Bit phase shifter for phased array antennas using an active DPDT switch

This paper presents an X-band 6-bit phase shifter using active bi-directional double-pole, double-throw (DPDT) switches. The phase shifter is implemented in a 130-nm SiGe BiCMOS technology. Three additional tuning bits are included in the design to achieve accurate phase shifting performance. The phase shifter demonstrates a > 11.5-dB gain in both directions of operation over the 8–12 GHz frequency range, with an RMS amplitude error < 0.9 dB, an RMS phase error < 2.2°, a return loss > 10 dB and an input-referred 1 dB compression point of −15 dBm. The circuit has dimensions of 2.6 × 1.5 mm2, including pads.

On the Application of Inverse-Mode SiGe HBTs in RF Receivers for the Mitigation of Single-Event Transients

Best practice in mitigation strategies for single-event transients (SETs) in radio-frequency (RF) receiver modules is investigated using a variety of integrated receivers utilizing inverse-mode silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs). The receivers were designed and implemented in a 130-nm SiGe BiCMOS technology platform. In general, RF switches, low-noise amplifiers (LNAs), and downconversion mixers utilizing inverse-mode SiGe HBTs exhibit less susceptibility to SETs than conventional RF designs, in terms of transient peaks and duration, at the cost of RF performance. Under normal RF operation, the SET-hardened switch is mainly effective in peak reduction, while the LNA and the mixer exhibit reductions in transient peaks as well as transient duration.

Wideband active bi-directional SiGe digital step attenuator using an active DPDT switch

A 6-bit active bi-directional silicon-germanium (SiGe) digital step attenuator (DSA) with multi-octave bandwidth using an active double-pole double-throw (DPDT) switch is demonstrated. To compensate the insertion loss (IL) and frequency dependent loss characteristics of conventional passive attenuators without using any additional amplifier and equalizer, the proposed attenuator employs active DPDT switches, which provide 4-way switching and bi-directional operation. The measured gain is 7.0-9.6 dB and the input and output return loss is better than 9 dB for 2-20 GHz. The measured root mean square (RMS) amplitude and phase errors in the major state are less than 0.4 dB and 3.0 degree, respectively. The chip size is 1.43 × 1.23 mm2, including pads. The proposed active bi-directional DSA consumes 30 mA from a 2.5 V supply.