M.J. Schindler

A high power 2-18 GHz T/R switch

A high-power 2-18-GHz T/R (transmit/receive) switch monolithic microwave IC (MMIC) has been developed for use in broadband T/R modules. This switch has a power handling of better than 35 dBm (3.2 W), 8-dB higher than any previously reported broadband switch. A combination of techniques was used to yield higher power handling while preserving low loss and high isolation. These circuit techniques include an asymmetrical design of the transmit and receive arms, the use of dual-gate FETs for handling large voltages, and the use of large FET peripheries for handling large currents. The use of dual-gate FETs in place of a stack of individual FETs reduces the device area, with a resulting reduction in parasitic series inductance through the FET and in shunt capacitance from the FET to ground. Power handling is somewhat lower for the dual-gate FET than for conventional stacked FETs, since RF voltage cannot be distributed as uniformly across the gates. Offstate capacitance is higher for a dual-gate FET than for a stacked FET, since the close proximity of the elements leads to additional parasitic capacitances.<<ETX>>

A highly linear MESFET

A highly linear GaAs MESFET has been developed. This device incorporates a spike profile in its active channel and was designed specifically for linearity. A third-order intercept (IP3) and a 1 dB compression power of 43 dBm and 19 dBm, respectively, have been measured on a 400 mu m device at 10 GHz. The difference between these two numbers, 24 dB, is the largest yet reported for a MESFET. This device also dissipates only 400 mW of DC power yielding a linearity figure-of-merit (IP3/P/sub DC/) of 50.<<ETX>>

A high power K/Ka-band monolithic T/R switch

A high-power K/Ka-band MESFET switch monolithic microwave integrated circuit (MMIC) has been developed for use in transmit/receive (T/R) modules. The switch demonstrates 0.2 dB insertion loss compression with 30 dBm input power, 12 dB higher than previously reported for K/Ka-band MESFET switches. Also, no isolation degradation was apparent with up to 28 dBm input power, a 13 dB improvement over the same previously demonstrated switches. A combination of techniques was used to yield higher power handling while preserving low loss and high isolation. These circuit techniques include the use of stacked MESFETs with large peripheries to improve power handling and transmission line transformers to minimize loss and maintain high isolation.<<ETX>>

A compact wideband balanced mixer

A compact wideband balun using a common-gate/common-source approach has been developed. Using this active balun on the LO port, a passive interdigital microstrip balun on the RF port, and a passive lumped element L-C balun on the IF port, a wideband balanced mixer was designed, fabricated and tested. This paper describes the mixer circuit design based on a new passive FET model. Test results of the active balun and the mixer including conversion loss, noise figure, and third order intercept point are presented for RF frequencies from 4 to 18 GHz.<<ETX>>

A novel 4-18 GHz monolithic matrix distributed amplifier

The authors describe the design, fabrication, and performance of a 4-18 GHz matrix distributed amplifier which incorporates a novel biasing scheme enabling the amplifier to run at higher voltages while drawing only half of the current of conventional multistage amplifiers having comparable gain levels. A voltage divider is used at the input of the FET pair to derive the gate bias, ensuring that both FETs are biased at the same point. This scheme enables the stages to be connected in cascade at RF frequencies and in cascode for DC biasing, thus conserving current. The amplifier shows >13 dB gain across the frequency band using a chip area of only 1.9 mm*2.1 mm.<<ETX>>The authors describe the design, fabrication, and performance of a 4-18-GHz matrix distributed amplifier. This amplifier incorporates a novel biasing scheme which enables the stages to be connected in cascade at RF frequencies and in cascode for DC biasing, thus conserving current. A gain of 14 dB+or-1.5 dB has been measured over the 4-18-GHz frequency band in a chip area of only 1.9 mm*2.1 mm.<<ETX>>

High linearity monolithic broadband pseudomorphic spike-doped MESFET amplifiers

A highly linear pseudomorphic spike-doped MESFET has been developed. This highly linear MESFET has been demonstrated at 10 GHz. Based on this device, two types of monolithic broadband amplifiers were designed and fabricated. Both the device and circuits achieved state-of-the-art linearity results while maintaining a low DC power consumption.<<ETX>>

An AlGaAs/InGaAs pseudomorphic high electron mobility transistor (PHEMT) for X- and Ku-band power applications

A PHEMT with record-high output power, gain and power-added efficiency at 10 and 18 GHz has been achieved due to the use of a novel method to improve the gate-drain reverse breakdown voltage. A critical surface problem was uncovered and resolved. Silicon nitride was deposited as surface passivation. The results of this work suggest that, in addition to superior low-noise performance, the PHEMT is also very promising for high-performance, power amplications in the X- to Ku-band frequency range.<<ETX>>

Ka-band GaAs HBT PIN diode switches and phase shifters

In this paper, we present results on millimeter-wave PIN diode switch arms and phase shifters fabricated in our HBT process line. The PIN diode is formed by the base-collector junction of the HBT and is therefore completely compatible with our conventional HBT process. A SPST switch arm exhibited 0.7 dB insertion loss and 21 dB isolation at 35 GHz. A high power version of this switch was capable of handling 29.5 dBm input power with less than 1 dB insertion loss at 17 V reverse bias. Low-pass/high-pass phase shifter bits with relative phase shifts of 45, 90, and 180/spl plusmn/10 degrees up to 36 GHz have also been demonstrated using HBT PIN diodes as switching elements. To our knowledge, this is the first demonstration of HBT PIN diode circuits at Ka-band. A detailed discussion of the circuit designs and measurements are given in the paper.<<ETX>>

A single chip 2.20 GHz T/R module

A single chip 2-20-GHz transmit/receive (T/R) module has been demonstrated. This MMIC (monolithic microwave integrated circuit) included a four-stage power amplifier chain, a four-stage low-noise amplifier chain, and two T/R switches. A selective ion implantation process was used. One implant profile was optimized for low-noise operation, and a second was optimized for power performance. All circuits were designed to be relatively insensitive to process variations to ensure adequate yield, despite the complexity of the chip. Distributed amplifiers were used throughout, and the T/R switches used a standard series-shunt FET configuration. All circuits were miniaturized to keep the total chip size small. The entire T/R is only 0.143 in*0.193 in (3.6 mm*4.9 mm).<<ETX>>

Modeling intermodulation distortion in GaAs MESFETs using pulsed I-V characteristics

A technique has been developed for modeling intermodulation distortion of GaAs MESFETs using pulsed I-V drain characteristics. The technique involves measuring the drain I-V characteristic using short drain and gate pulses from a DC operating point. This pulsed I-V characteristic is used to model the nonlinearity of the drain current source. In addition, S-parameters measured about the DC bias point are used to model the gate capacitance nonlinearity. These nonlinearities are combined into a single model, and the harmonic balance method is used to simulate intermodulation performance. This technique has been used to simulate the third-order intermodulation distortion of a spike-doped MESFET and to investigate sensitivities of source and load impedance and device nonlinearities on intermodulation performance.<<ETX>>