A. Akhnoukh

Adaptive Multi-Band Multi-Mode Power Amplifier Using Integrated Varactor-Based Tunable Matching Networks

This paper presents a multi-band multi-mode class-AB power amplifier, which utilizes continuously tunable input and output matching networks integrated in a low-loss silicon-on-glass technology. The tunable matching networks make use of very high Q varactor diodes (Q>100 @ 2 GHz) in a low distortion anti-series configuration to achieve the desired source and load impedance tunability. A QUBIC4G (SiGe, ft=50 GHz) high voltage breakdown transistor (VCBO=14 V, VCEO>3.6 V) is used as active device. The realized adaptive amplifier provides 13 dB gain, 27-28 dBm output power at the 900, 1800, 1900 and 2100 MHz bands. For the communication bands above 1 GHz optimum load adaptation is facilitated resulting in efficiencies between 30%-55% over a 10 dB output power control range. The total chip area (including matching networks) of the amplifier is 8 mm2

Varactor Topologies for RF Adaptivity with Improved Power Handling and Linearity

Ultra linear silicon-on-glass varactor topologies with improved power handling and linearity have been realized. The resulting components include integrated bias networks and provide excellent low-loss performance for large capacitances (e.g. C=20pF Q>100 at 2 GHz with Vcont=2 V). Using a novel center tap circuit the linearity has been improved for narrowband two-tone signals yielding measured IIP3V values above 75 V for tone spacings >10 kHz. By implementing two varactor stacks in series with integrated bias networks the power handing improves 4x, while the IIP3V doubles. The resulting devices can be used as flip-chip components enabling linear adaptive wireless applications.

A Monolithic Low-Distortion Low-Loss Silicon-on-Glass Varactor-Tuned Filter With Optimized Biasing

A low-distortion varactor-tuned bandpass filter is demonstrated on a high-Q silicon-on-glass technology. The dc bias network is optimized to achieve high linearity, the center frequency of the filter tunes from 2.4 to 3.5 GHz, and the measured loss of the filter is 2-3 dB at 2 GHz, with a stopband rejection of 25 dB. The measured IIP3 of the filter was +46 dBm

Thermal effects in suspended RF spiral inductors

Self-heating effects on integrated suspended and bulk spiral inductors are explored. A dc current is fed through the inductors during measurement to emulate dc and radio frequency power loss on the inductor. A considerable drop in Q by /spl sim/18% at 36.5 mW is observed for suspended coils with 3-/spl mu/m aluminum metallization compared to reference inductors on bulk-Si. Simulations in Ansofts ePhysics indicate that, due to the thermal isolation of the suspended coil, the power loss from resistive self-heating in the metal has to be transferred outwards through the metal turns. This also results in a thermal time constant. This time constant is measured to be /spl sim/10 ms, meaning that it can affect power circuits operating in pulsed mode.

A 2-GHz digital I/Q modulator in 65-nm CMOS

We propose a novel digital I/Q modulator implemented in 65 nm CMOS technology. Using in-phase (I) and quadrature-phase (Q) clock signals with a 25% duty cycle, the modulator can directly construct the RF output signal using four transistor switch banks with a power combiner. The circuit achieves 12.6 dBm peak output power and 20% peak drain efficiency at 2 GHz. While providing 6 dBm output power, the error vector magnitude (EVM) is 3.7% and could be used as pre-driver or final transmit stage. The first ever all-digital I/Q RF-DAC prototype is thus experimentally demonstrated.

Improved hybrid SiGe HBT class-AB power amplifier efficiency using varactor-based tunable matching networks

This paper presents a 1.8GHz prototype class-AB power amplifier using a QUBIC4G (SiGe, f/sub t/ = 40GHz) handset device with adaptive in- and output matching networks. The realized amplifier provides: 13dB gain, 28 dBm output power, with an efficiency greater than 33-51% over a 10dB output power control range.

A Low-Loss Compact Linear Varactor Based Phase-Shifter

Design trade-offs are presented for varactor-based variable phase-shifters in terms of size, tuning range, bandwidth/phase linearity and large-signal performance. Based on this study, a compact, low-loss (0.6dB/90deg @ 1.0 GHz), wideband and extremely linear varactor-based phase shifter is presented.

A 120µW fully-integrated BPSK receiver in 90nm CMOS

In this work a highly integrated, ultra-low-power BPSK receiver for short-range wireless communications is presented. The receiver consists of a power divider, two injection-locked RC oscillators with limiting buffers and an XOR output stage. The demodulation principle is based on the dynamic phase response of the two BPSK signal injected oscillators. As proof of concept, a 300 MHz receiver was implemented in a 90nm CMOS technology. The whole receiver has an active die area of 0.04 mm2, a sensitivity of −34 dBm at 1Mbps and consumes only 120 µW from 1V supply, which relates to an energy per bit of only 0.12 nJ/bit, a value which is among the best reported up-to-date for low-transmission rate systems.

Effect of a Local Ground and Probe Radiation on the Microwave Characterization of Integrated Inductors

Microwave characterization of an integrated inductor is often carried out with respect to a local ground reference. The measurement outcome, however, does not necessarily reproduce the behavior of the device in an actual circuit where a ground reference does not exist. Furthermore, inductor measurements can be affected by the unequal currents on the inner and outer conductors of the coaxial lines internal to the RF probes. Such currents tend to radiate the microwave energy into the surroundings and manifest themselves as unexpected ripple and resonance features in measurement results. In this study, a measurement model is developed including both effects and is used to analyze experimental data obtained from integrated spiral inductors. A novel deembedding technique is then proposed and applied to eliminate the local ground and unequal coaxial current effects.

A +18dBm, 79–87.5GHz bandwidth power amplifier in 0.13µm SiGe-BiCMOS

A three-stage, 77/79GHz transformer-coupled differential power amplifier is implemented in 130nm SiGe-BiCMOS. Common-base stages maximize output voltage swing and power, while a cascode first stage enhances gain for greater power-added efficiency (PAE). A frequency-scalable, parasitic-compensated balun combines power from the output stages to the 50Ω load with <1.2dB loss and 70×70µm2 area on-chip. The measured peak small-signal gain is 27dB at 83GHz, and −3dB bandwidth is >8GHz. Maximum output power and peak-PAE are 18dBm and 9%, respectively, at 84GHz. The 0.23mm2 active area PA consumes 395mW from a 2.5V supply.