A 40 –45 GHz MONOLITHIC GILBERT CELL MIXER

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  • Author: Andrew Dearn and Liam Devlin
Millimetre-wave mixers are commonly realised using hybrid fabrication techniques, with diodes as the nonlinear mixing elements. The main reasons for this are that the modelling issues for the passive hybrids/baluns and the relatively simple diode structures are well characterised and understood. The cost of such mixers can also be very low (Ref. 1). The major disadvantage of diode mixers is the relatively high conversion loss. At microwave frequencies active mixers utilising FET devices are now commonplace, and offer greatly reduced conversion loss, or even gain (Ref. 2). For mm-wave frequencies the Pseudomorphic HEMT Transistor allows similar active circuits to be fabricated, particularly in GaAs Monolithic Microwave Integrated Circuit (MMIC) form.