K. Buisman

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

Active Harmonic Load–Pull With Realistic Wideband Communications Signals

A new wideband open-loop active harmonic load-pull measurement approach is presented. The proposed method is based on wideband data-acquisition and wideband signal-injection of the incident and device generated power waves at the frequencies of interest. The system provides full, user defined, in-band control of the source and load reflection coefficients presented to the device-under-test at baseband, fundamental and harmonic frequencies. The system capability to completely eliminate electrical delay allows to mimic realistic matching networks using their measured or simulated frequency response. This feature enables active devices to be evaluated for their actual in-circuit behavior, even on wafer. Moreover the proposed setup provides the unique feature of handling realistic wideband communication signals like multicarrier wideband code division multiple access (W-CDMA), making the setup perfectly suited for studying device performance in terms of efficiency, linearity and memory effects.

Low-distortion, low-loss varactor-based adaptive matching networks, implemented in a silicon-on-glass technology

A low-loss, low-distortion continuously tunable matching network, is demonstrated at 2 GHz in a silicon-on-glass varactor IC technology. The tuner uses an optimized varactor configuration to minimize distortion, and exhibits less than 0.5 dB loss and IM3<-50 dBc at 27 dBm output power, and tunes with a VSWR>250:1 to 1:1.

Ultra Linear Low-Loss Varactor Diode Configurations for Adaptive RF Systems

Two linear low-loss varactor configurations for tunable RF applications are compared. The wide tone-spacing varactor stack provides the best linearity for signals with relative large tone spacing like receiver jammer situations. The narrow tone-spacing varactor stack offers the highest linearity for in-band-modulated signals, and is better suited to adaptive transmitters. Both structures make use of a varactor with an exponential C(VR) relation, and so the different requirements of transmit and receive chains can be addressed in one technology. Both configurations have been realized in a silicon-on-glass technology. The measured Q at 1.95 GHz is from ~ 40 to 200 over a capacitance tuning range of 3.5 with the maximum control voltage of 12 V. The measured OIP3 of both structures are roughly 60 dBm.

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.

Improved RF Devices for Future Adaptive Wireless Systems Using Two-Sided Contacting and AlN Cooling

This paper reviews special RF/microwave silicon device implementations in a process that allows two-sided contacting of the devices: the back-wafer contacted silicon-on-glass (SOG) substrate-transfer technology (STT) developed at DIMES. In this technology, metal transmission lines can be placed on the low-loss glass substrate, while the resistive/capacitive parasitics of the silicon devices can be minimized by a direct two-sided contacting. Focus is placed here on the improved device performance that can be achieved. In particular, high-quality SOG varactors have been developed and an overview is given of a number of innovative highly-linear circuit configurations that have successfully made use of the special device properties. A high flexibility in device design is achieved by two-sided contacting because it eliminates the need for buried layers. This aspect has enabled the implementation of varactors with special Ndx -2 doping profiles and a straightforward integration of complementary bipolar devices. For the latter, the integration of AlN heatspreaders has been essential for achieving effective circuit cooling. Moreover, the use of Schottky collector contacts is highlighted also with respect to the potential benefits for the speed of SiGe heterojunction bipolar transistors (HBTs).

High-performance varactor diodes integrated in a silicon-on-glass technology

High-performance low-loss boron-passivated Schottky varactor diodes have been fabricated in a silicon-on-glass substrate transfer technology, using laser-annealed back-wafer contacts and copper-plated aluminum. The diodes have well-defined doping profiles predetermined by the circuit application and high quality factors ranging typically from 100 till 300 at 2 GHz.

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

Pure-boron chemical-vapor-deposited layers: A new material for silicon device processing

This paper places focus on the special properties of pure boron chemical-vapor deposition (CVD) thin-film layers that, in several device applications, have recently been shown to augment the potentials of silicon device integration. Besides forming a reliable an efficient dopant source for both ultrashallow and deep p+n junctions, the deposited amorphous boron (α-B) layer itself, even for sub-nm thicknesses, is instrumental in suppressing minority electron injection from the n-region into the p+ contact. Therefore, even for nm-shallow junctions where the current levels mainly will approach high Schottky-like values, the diodes exhibit saturation current levels that can become as low as that of conventional deep junctions. Moreover, the α-B layer has chemical etch properties that make it particularly suitable for integration as the front-entrance window in photodiodes for detecting nm-low-penetration-depth radiation and charged particles.

A GaAs Junction Varactor With a Continuously Tunable Range of 9 : 1 and an

In this letter, a junction varactor is presented with a large capacitance tuning range, while providing very high linearity. Such varactors are extremely useful in adaptive RF applications, which directly benefit from passive components with high tuning range and high linearity. Using a preproduction GaAs process technology and third-order intermodulation (IM 3) cancellation techniques, a very linear device is created with a capacitance tuning range as large as 9 : 1 over a control voltage range from 0 to 15 V. Its third-order output intercept point is 57 dBm; the average quality factor is ~ 50, and the breakdown voltage is 28 V. These measured results represent the current state-of-the-art in tuning range, linearity, and quality factor among all existing continuously tunable elements.