Alina Moussessian

Modeling and performance of a 100-element pHEMT grid amplifier

A 100-element hybrid grid amplifier has been fabricated, The active devices in the grid are custom-made pseudomorphic high electron mobility transistor (pHEMT) differential-pair chips. We present a model for gain analysis and compare measurements with theory. The grid includes stabilizing resistors in the gate. Measurements show the grid has a peak gain of 10 db when tuned for 10 GHz and a gain of 12 dB when tuned for 9 GHz. The maximum 3-dB bandwidth is 15% at 9 GHz. The minimum noise figure is 3 dB. The maximum saturated output power is 3.7 W, with a peak power-added efficiency of 12%. These results area significant improvement over previous grid amplifiers based on heterojunction bipolar transistors (HBTs).

Flexible Electronics: Thin Silicon Die on Flexible Substrates

Silicon thinned to 50 mum and less is flexible allowing the fabrication of flexible and conformable electronics. Two techniques have been developed to achieve this goal using thinned die: die flip chip bonded onto flexible substrates [polyimide and liquid crystal polymer (LCP)] and die flip chip laminated onto LCP films. A key to achieving each of these techniques is the thinning of die to a thickness of 50 mum or thinner. Conventional grinding and polishing can be used to thin to 50 mum. At 50 mum, the active die becomes flexible and must be handled by temporarily bonding it to a holder die for assembly. Both reflow solder and thermocompression assembly methods are used. In the case of solder assembly, underfill is used to reinforce the solder joints. With thermocompression bonding of the die to an LCP substrate, the LCP adheres to the die surface, eliminating the need for underfill.

System concepts and technologies for high orbit SAR

This paper discusses large aperture, high orbit radar concepts for measuring sub-centimeter-level surface displacements from space. These measurements will enable applications such as earthquake simulation, modeling and forecasting. We explain the need for large aperture, high orbit arrays and discuss the technologies required to achieve these missions.

A resonant switch for LNA protection in watt-level CMOS transceivers

An integrated resonant switch designed to protect low-noise amplifier (LNA) circuits in CMOS transceivers is reported. The design implements the receive-path portion of a transmit/receive switch protecting 3-V-process transistors from 5 W (22-V peak) transmit signals while simultaneously helping to achieve a good LNA noise figure on receive and low power loss on transmit. Since the approach is to combine an LNAs matching network and switch functions, the design has no traditional insertion loss on receive. The effective loss to the transmitted signal is less than 0.5 dB using moderate quality inductors (Q>6) and 0.1 dB using Q=12 inductors achievable in most RF-aware CMOS silicon-on-insulator foundries at UHF through S-band frequencies.

Gain and stability models for HBT grid amplifiers

A 16-element heterojunction bipolar transistor (HBT) grid amplifier has been fabricated with a peak gain of 11 dB at 9.9 GHz with a 3-dB bandwidth of 350 MHz. We report a gain analysis model for the grid and give a comparison of the measurement and theory. The measured patterns show the evidence of a common-mode oscillation. A stability model for the common-mode oscillation is developed. Based on the stability model, a lumped capacitor gives suitable phase shift of the circular function, thus stabilizing the grid. A second 18-element grid was fabricated, using this theory, with improved stability.

An active membrane phased array radar

We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane-compatible transmit/receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We discuss the T/R module design and integration with the membrane. We also present transmit and receive beam-steering results for the array.

MEO SAR System Concepts and Technologies for Earth Remote Sensing

Next-generation interferometric synthetic aperture radar (InSAR) systems may provide the basis for establishing an earthquake-forecasting capability within a twenty-year time frame. Such systems would need to provide data with fine temporal resolution, so the system architecture would need to allow for wide-area coverage in order to minimize the effective interferometric repeat time. This paper discusses the coverage advantages associated with medium-Earth orbit (MEO) InSAR systems for observing geophysical phenomena. As MEO architectures dictate the need for large radar antennas, this paper also presents a discussion of advanced antenna technologies—and associated challenges—that might provide revolutionary decreases in the mass densities of large radar aperture antennas.

A terahertz grid frequency doubler

We present a 144-element terahertz quasi-optical grid frequency doubler. The grid is a planar structure with bow-tie antennas as a unit cell each loaded with a planar Schottky diode. The grid has an output power of 5.5 mW at 1 THz for 3.1-/spl mu/s, 500-GHz input pulses with a peak power of 36 W. This is the largest recorded output power for a multiplier at terahertz frequencies.

Stability of grid amplifiers

We present a stability model for quasi-optical grid amplifiers. This model is useful for predicting and suppressing the common-mode oscillations that often occur in amplifier grids. Three stabilization techniques will be discussed. The first technique uses a capacitor to stabilize the grid. The second approach employs resistance to suppress the oscillations. The final technique stabilizes the grid by reducing the on-chip common-mode resistance, allowing greatly increased amplifier efficiencies. Experimental evidence will be presented to confirm the validity of our stability model.

Jupiter ICY moon explorer (JUICE): Advances in the design of the radar for Icy Moons (RIME)

This paper presents the Radar for Icy Moon Exploration (RIME) that is a fundamental payload in the Jupiter Icy Moon Explorer (JUICE) mission of the European Space Agency (ESA). RIME is a radar sounder aimed to study the subsurface of Jupiters icy moons Ganymede, Europa and Callisto. The paper illustrates the main goals of RIME, its architecture and parameters and some recent advances in its design.