A multifunction MMIC, containing the core components required for an EHF satellite communications receiver, operating over 43.5 to 45.5GHz, has been designed and tested. The circuit has been fabricated using a high yield, commercially available, 0.25pm PHEMT GaAs -InGaAs -AlGaAs foundry process at GEC Marconi Materials Technology Ltd. The multifunction MMIC integrates a low noise amplifier, downconvertor, local oscillator dopbler and buffer amplifier onto a single chip occupying an area of 3.0 x 3.8mm2. Successful performance was achieved for a first pass iteration, namely 4.3dB noise figure and 5 to 8dB conversion gain with a low local oscillator (LO) drive level of OdBm.
IntroductionThere is an increasing demand for more sophisticated military satellite communication systems, (a) to ensure secure communications in times of tension or war and (b) due to more demanding end user requirements. eg large numbers of computers exchanging digital information as part of Command, Control, Communications and Intelligence (C'I) networks.Exploitation of EHF fiequency bands for next generation military satellite communications offers a number of advantages over UHF and SHF solutions including improved protection against jamming, low probability of intercept and minimal disruption to earth-space propagation in the presence of high altitude nuclear explosions"). Moving to EHF operating frequencies means that antenna size is reduced allowing compact phased arrays to be deployed on satellites. Phased array antennas offer the potential for beam nulling or the deployment of spot beams to provide further immunity from jamming.MMICs are a key enabling technology for EHF phased arrays due to their small size, improved reliability, high repeatability and the potential for low cost. Multifunction MMICs, integrating several functions onto a single chip, are particularly attractive at mmwave frequencies since they allow considerable Size and weight reduction along with improved reliability from having fewer components. In addition, circuit performance is less compromised by interface , parasitics of multiple tape bonds used to connect together many individual building block functions.The level of integration that can be accommodated is a function of the manufacturing process yield, testing requirements and the accuracy of CAD design tools. A careful balance has to be made between the level of integration that is practical without compromising circuit yield. This paper addresses the design, fabrication and assessment of a high yield multifunction MMIC integrating the core elements required in an EHF receiver; low noise amplifier, downconvertor, local oscillator doubler and buffer amplifier.
Circuit design and measured performanceA high level of gain (> 1OOdB) is required in an EHF receiver to boost the low power signals at the receive antenna to an acceptable level. The majority of amplification is usually performed at IF, since gain blocks at these frequencies are relatively inexpensive. For our application, 25dB of RF gain was desired in...
