Timothy Boles

AlGaAs PIN diode multi-octave, mmW switches

The novel use of an AlGaAs/GaAs heterojunction to form a PIN diode, with reduced RF resistance (RS) and no change in junction capacitance (CT)[1]–[3], has been analyzed and employed in the development of several different PIN diode switches of various circuit topologies. Series designs demonstrate improved insertion loss, shunt designs improved isolation, and series-shunt designs improvements in both parameters. These switches demonstrate superior broadband performance, with low insertion loss and high isolation from 50MHz to almost 80GHz, and series-shunt switches exhibit 50% increased input power capability over equivalent homojunction GaAs PIN diode switches.

Heterojunction PIN diode switch

This paper describes the development of a heterojunction AlGaAs/GaAs PIN diode as a replacement for the homojunction GaAs PIN diodes commonly used in microwave systems as a control element for commercial and military switch applications up through millimeter wave frequencies. In particular, a single heterojunction PIN diode, when simulated at a bias of 10 mA in a 50 ohm series configuration, indicates a potential reduction in insertion loss of 37% (Rs) with no degradation in isolation (Cj). This paper describes a switch topology of choice which uses a series-shunt element at the main junction, since it offers the widest bandwidth due to the low zero bias capacitance of the series diode. This simple structure has an upper frequency limitation that is dependent on the electrical distance due to the physical location of the series diode relative to the center of the actual device junction and the maximum isolation achievable by the Cj of a discrete diode. PIN switch circuits and RF probable test structures were processed through our GaAs wafer fab and later tested on-wafer for broadband RF performance from 50 MHz through 40 GHz. A comparison between simulated and empirical results for insertion loss, return loss and isolation demonstrates excellent agreement for isolation and a 10% offset for insertion loss and return loss.

A monolithic, 1000 watt SPDT switch

A monolithic high power, high linearity, broadband, PIN diode switch capable of handling greater than 1000 watts of pulsed peak RF power has been designed and developed using a patented glass/silicon technology. This technology designated HMIC, Heterolithic Microwave Integrated Circuit, has been developed for various mixed signal and control circuit function applications ranging from HF through microwave frequencies. The unique design and fabrication techniques required for the needed improvements in thermal resistance and peak-to-peak voltage handling of this high power switch are discussed in detail. In addition, the results of this development effort in terms of standard switch parameters; insertion loss, isolation, return loss, and power handling are presented in the following paper.

HMIC the ultimate SOI microwave integrated circuit technology

HMIC is a microwave and mmW integrated circuit topology that can create three dimensional structures based upon a inimitable marriage of silicon and glass at a waferscale level which enable high performance, low loss, lower cost realizations of many of the classic hybrid MMICs. In addition, the unique nature of the bonding together of these two dissimilar materials into common substrate allows the monolithic insertion of active elements in combination with low loss, high Q, lumped element passive components to produce microwave circuits that can be realized no other way or at as low a cost. Silicon has a high thermal conductivity and can be doped over a very wide range of resistivities, while glass is a true insulator and has a very low high frequency loss tangent. Thus HMIC based circuits are able to be produced that have frequency responses as high as 110 GHz while still being able to handle tens of watts of power. This capability is truly unique in the world of MMICs as well as SOI based integrated circuits. This paper will illustrate the distinctive aspects of the HMIC technology as well as providing detailed descriptions of high Q component construction, and several single function integrated circuits, both passive and active, that can be realized. These descriptions will include electrical schematics, actual circuit topologies, and the resultant high frequency performance.

Ka band high power AlGaAs PIN diode switches

In this paper we present the design and performance of millimeter wave MMIC switches in the patented MA-COM AlGaAs heterojunction PIN Diode process that allow us to produce high power and low insertion loss devices. The design process from a reflective SPDT switch to a non-reflective version of the switch, with intense use of HFSS and ADS software, is presented. These switches were designed to meet demanding requirements: low insertion loss less than 0.8 dB, 40dBm peak power and 37dBm CW power, and 30dB isolation.

Commercial manufacturing practices applied to phased array radars

Transmit/Receive Modules for Phased Array Radar are often identified as a key cost driver for the system. The cost structure of the module is driven by both the performance specifications and the choices made in design and manufacturing of the module. Seeking a path to dramtically lower the cost of T/R modules for phased array systems, commercial processes and practices have been adopted for the MMIC design, MMIC packaging and module construction. These new manufacturing approaches offer a path to cost reduction while maintaining a high level of performance.

Advanced Components for Applications in S-Band and X-Band Radars

Performance issues in S-Band and X-Band radar applications, have been investigated in parallel paths. The first approach continued with the basic GaAs based MESFET and pHEMT devices with the addition of field plate structures to enhance the transistor source-to-drain breakdown, enabling operation at higher voltages and producing significant improvements in device operation. The second direction questioned the basic material properties underlying the device structures. This methodology has led to the investigation of a number of pHEMT and HEMT designs based on SiC, GaN on SiC, and GaN on silicon devices for both S-Band and X-Band radar applications.

An HMIC I/Q modulator/demodulator for RFID applications

HMIC is a microwave and mmW integrated circuit topology that can create three dimensional structures based upon an intimate marriage of silicon and glass at a wafer scale level which enable high performance, low loss, lower cost realizations of many of the classic hybrid MMICs. In addition, the unique nature of the bonding together of these two dissimilar materials into common substrate allows the monolithic insertion of active elements in combination with low loss, high Q, lumped element passive components to produce microwave circuits that can be realized no other way or at as low a cost. This paper will illustrate the results of the development of an integrated I/Q modulator/demodulator MMIC for RFID reader applications using HMIC technology as an integration medium. The resultant RF performance improvements and advantages of the modulator and the overall effect on RFID wireless systems operation will be presented.

A fully monolithic HMIC low noise amplifier

A two/three stage monolithic silicon low noise amplifier has been designed utilizing SPICE modeling techniques. The circuit design architecture is based on high frequency, small signal BJTs, consisting of an grounded emitter stage at the input and a Darlington configured pair at the device output. A resistor network, with a bypass capacitor, is utilized not only to provide proper DC biasing for each stage, but also obtain impedance matching to 50 ohms at the circuit input and output and to provide RF feedback for the desired broad band gain response. A patented HMIC (Heterolithic Microwave Integrated Circuit) glass process is employed to provide both the required collector isolation between active device stages and as an extremely low loss dielectric medium for minimum parasitic, high Q passive, reactive elements.

HMIC 3-D chipscale, surface mount devices

Broadband components continue have the basic issues of fundamental high frequency performance and unit-to-unit reproducibility. While possible solutions to these two basic problems exist, it is universally acknowledged that both the basic semiconductor performance at frequencies above 10 GHz and the unit variation are severely limited by packaging, die attach, and chip and wire assembly techniques. The purpose of this paper is to present a unique, fundamentally different approach to the packaging and monolithic integration of ultra wideband switches which not only includes the electrical input/output but also device thermal heat sinking. This method is based upon a technology, HMIC, which utilizes standard semiconductor wafer scale processes to realize the final monolithic, surface mountable element, in this case a single pole four throw multi octave switch.