Subramaniam Shankar

An 8–16 GHz SiGe Low Noise Amplifier With Performance Tuning Capability for Mitigation of Radiation-Induced Performance Loss

We present a wideband, low noise amplifier (LNA) implemented in a Silicon-Germanium Heterojunction Bipolar Transistor (SiGe HBT) technology. This SiGe LNA covers a frequency range of 8-16 GHz and achieves a peak gain of 17.5 dB at nominal bias and a peak OIP3 of 15.8 dBm at 10 GHz at nominal bias. The noise figure (NF) of the LNA is 4.5-8.1 dB across band, and it nominally consumes 4 mA from a 4 V supply. Samples were irradiated with 63.3 MeV protons to proton-equivalent doses ranging from 200 krad(Si) to 2 Mrad(Si). This LNA incorporates bias control “tuning-knobs” to enable bias tuning to mitigate for RF performance loss due to total dose exposure and process variation in performance metrics. The effectiveness of the tuning “knobs” to compensate for lost post-irradiated performance was investigated. It was found that the LNA performance can be restored with the use of the tuning knobs with a performance tuning algorithm.

A 6–20 GHz Adaptive SiGe Image Reject Mixer for a Self-Healing Receiver

A wideband (6-20 GHz) Silicon-Germanium (SiGe) adaptive image-reject mixer with an intermediate frequency (IF) of 1.8 GHz is presented. The mixer can be “self-healed” to deliver consistent performance by nullifying the effects of process variations, environmental changes, or aging. Various performance metrics of the mixer can also be adapted to different specifications across multiple frequency bands. A conversion gain greater than 15 dB, an image rejection ratio (IRR) exceeding 35 dB, and an output 1-dB compression point greater than 10 dBm, were obtained in measurement. An automated self-healing procedure is developed and shown to be effective for improving the measured performance of the mixer. The mixer was fabricated in a 150 GHz peak fT, 200 nm SiGe BiCMOS process technology and consumes 215 mA of current operating off a 4 V rail.

Analysis and design of a 3–26 GHz low-noise amplifier in SiGe HBT technology

The analysis and design of a wideband silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) low noise amplifier (LNA) is presented. Resistive shunt-shunt feedback is employed to achieve wideband gain and matching characteristics and it is shown that the addition of small reactive elements can extend the bandwidth of the amplifier significantly. Measured data for the LNA, implemented in a 130-nm SiGe BiCMOS technology, show 9 dB gain with less than 1.0 dB variation across 3-26 GHz, and input and output return losses better than -10 dB over the entire bandwidth. The measured noise figure (NF) is less than 5 dB from 3-18 GHz and rises to only 6.5 dB at 24 GHz. In addition, the amplifier exhibits excellent linearity performance, with a input-referred third-order intercept point (IIP3) of 5.8 dBm and input-referred 1 dB compression point (P1dB) of -5.6 dBm. This SiGe amplifier occupies 0.48 mm2 (including pads) and consumes 33 mW of power while operating off a 3.3 V supply.

Best practices to ensure the stability of sige HBT cascode low noise amplifiers

This work provides a detailed examination of the stability of SiGe cascode low noise amplifiers (LNAs). The upper base is identified as a problematic node for stability. S-probe simulations are used to extract reflection coefficients internal to the circuit and provide insight on how to improve the stability of a cascode amplifier and thereby establish “best practices” for designers. These techniques are incorporated into a cascode LNA design fabricated on a 180 nm, 150 GHz fT SiGe BiCMOS technology. The measured SiGe LNA has a gain of 16.5 dB and a noise figure of 2.1 dB at a center frequency of 9.2 GHz. A series of measurements using tuners at both the input and output confirm the LNA is stable for all impedances covered by the tuners (|Γ| <; 0.8).

A SiGe 8–18-GHz Receiver With Built-In-Testing Capability for Self-Healing Applications

A wideband (8-18 GHz) built-in test receiver in silicon-germanium technology is presented. The receiver chain consists of a low-noise amplifier (LNA), an image-reject mixer, on-chip automatic gain control ring oscillator sources that are used to provide test signals of a predefined amplitude, and control circuitry in the form of digital-to-analog converters and data registers. Both the LNA and the mixer circuit blocks incorporate tuning knobs to enable tuning of RF metrics to ensure consistent performance and mitigate the negative effects of process, voltage, and temperature variations, aging, and damage from extreme environments such as ionizing radiation. A maximum post-healed gain greater than 30 dB, an image rejection ratio exceeding 30 dB, output third-order intercept point greater than 8 dBm, and noise figure less than 9 dB are obtained in measurement. An automated healing algorithm was developed and shown to be effective at improving the overall performance of the receiver. The receiver was fabricated in an 0.18- μm SiGe BiCMOS process with a peak fT of 150 GHz, and consumes 240-260 mA from a 4-V supply.

A UWB SiGe LNA for multi-band applications with self-healing based on DC extraction of device characteristics

We present an ultra-wideband, Low Noise Amplifier (LNA) implemented in a Silicon-Germanium Heterojunction Bipolar Transistor (SiGe HBT) technology. This SiGe LNA covers a frequency range of 8–18 GHz and achieves a peak gain of 15.6 dB at nominal bias and a nominal OIP3 of 3 dBm at 13 GHz. The Noise Figure (NF) of the LNA is 3.6–7.9 dB across band, and it consumes 7 mA from a 3.3 V supply. This LNA incorporates bias control knobs for circuit ‘self-healing’ to compensate for process-induced (or other) variations in performance metrics. Process variations are detected using a companion source measure unit (SMU) test circuit that gathers DC device information to determine the healing to be applied.

Frequency- and amplitude-tunable X-to-Ku band SiGe ring oscillators for multiband BIST applications

An 8–17 GHz SiGe ring oscillator covering the X- and Ku-bands for built-in-self-test of multiband system-on-chip solutions is demonstrated. The oscillator features highly linear frequency control over the bandwidth, with 72% tuning range in a small form factor of 0.652 mm2. To the authors knowledge, this is the widest tuning range/smallest form factor combination achieved by a ring oscillator that spans both X and Ku bands. A second ring oscillator with band selectivity and output power control is also presented, covering the 9–11 GHz and 17–21 GHz bands. This second oscillator features an ultra-small form factor of only 0.036 mm2. Both oscillator designs are based on a 3.3 V supply and were implemented in a commercially-available 180 nm SiGe BiCMOS platform.

An adaptive, wideband SiGe image reject mixer for a self-healing receiver

A wideband (6–20 GHz) SiGe adaptive image reject mixer with an IF bandwidth of more than 1.8 GHz is presented. The mixer can be “self-healed” to deliver consistent performance across band by nullifying the effects of process variations, environmental changes or aging and can be adapted to different specifications. A conversion gain greater than 15 dB, an image rejection ratio (IRR) exceeding 35 dB and an output 1-dB compression point greater than 10 dBm were obtained in measurement. An automated self-healing procedure is shown to be effective for improving the measured performance of the mixer. The mixer was fabricated in a 150 GHz peak fT 200 nm SiGe BiCMOS process and consumes 215 mA of current operating off a 4 V rail.

Mitigation of Total Dose Performance Degradation in an 8–18 GHz SiGe Reconfigurable Receiver

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.

Predicting large-signal CML gate delay using Y-Parameters for fast process optimization

A Y-Parameter based Figure-of-Merit (FoM) is proposed that can accurately predict large-signal Current-Mode Logic (CML) gate delay from small-signal S-parameter simulations/measurements. A differential-mode (DM) half circuit of an emitter-coupled differential pair with resistive load is used as the small-signal building block. The FoM is applied to various collector current (IC) and load resistor (RL) combinations obtained from the power-delay curve of a prototype SiGe technology platform. Results of the FoM delay predictions are compared with ring oscillator gate delays. A small-signal model parameter based equation is also proposed that provides physical insight into the components that contribute to the overall CML delay.