tuning resolution was found to be 1 pm, due to the limitation of the OSA and TLS, which exhibited the best resolution of 1 pm. The tuning repeatability was found to be 0.4% over the entire tuning range of 2 nm. The range can be improved by optimizing the package design of the carbon-fiber composite.
INTRODUCTIONMillimetre-wave operation is of growing importance to the distribution of broadband telecommunication services and to wireless, local-area networks [1,2]. Millimetre-wave transceivers based on GaAs and InP MMICs are key components of these wideband systems [3,4]. In particular, InP-based high electron mobility transistors (HEMTs) have demonstrated the highest gain, lowest noise figure, and highest frequency capability of any three terminal transistor [5]. This paper describes a high-performance downconverting receiver module, based on InP and GaAs MMICs, that has been developed for point-to-point telecommunications links operating in the frequency range of 82-104 GHz. The amplifiers, designed and tested at CSIRO, were made by Northrup Grumman Space Technologies (NGST, formerly TRW) using standard 0.1-m InP HEMT [6] and 0.15-m GaAs pHEMT processes [7].
THE MMICsThe receiver chip-set comprises a pair of W-band InP amplifiers connected in cascade, with output signal connected to a subharmonically pumped image-reject mixer (SHPIRM), configured as a down-converter. The local oscillator drive to the mixer is provided by a medium-power V-band amplifier. The amplifiers were fabricated by NGST (see above), whereas the mixers were fabricated at CSIRO.The MMICs were designed using device-and circuit-modelling techniques that have yielded first-pass design success for many mm-wave ICs designed at CSIRO. Small-signal InP HEMT models were developed by TRW using carefully designed on-wafer calibration and device embedding circuits. The models have been verified and optimized to frequencies above 120 GHz, through the design and evaluation of a range of amplifier circuits [8]. In addition, standard Agilent-EESOF simulator models for the thinfilm capacitors, open-circuit stubs, Lange couplers, and the spiral IF hybrid were invalid because either the dimensions of the element, or the operating frequency, were outside the specified limits. Therefore, S-parameter matrices describing these elements were derived using electromagnetic simulator software. The four-stage W-band InP HEMT amplifier has been described in a previous paper [9]. The gain is 15.5 dB Ϯ 1.5 dB over the 82-112-GHz range. The input and output return loss is better than 10 dB over the same range. Each stage of the amplifier was biased at 1.2-V drain-supply voltage and with drain current in the range 4 -6 mA, optimized to give the best frequency response. The V-band pHEMT amplifier is also a four-stage microstrip design. The GaAs pHEMT devices have a gate length of 0.15 m and a four-finger, interdigitated geometry with a total width of 200 m. The performance of the amplifier, measured on-wafer, is shown in Figure 1. The gain is 25 dB Ϯ 2 dB over the 40 -55-GH...