Low Cost Microstrip Filters and Mixers at 43GHz--IEEE paper

Low Cost Microstrip Filters and Mixers at 43GHz
Steve Williamson and Andy Dearn*

Introduction
Microwave Integrated Circuits (MICs), using discrete devices assembled onto a printed microstrip substrates were
originally used at low microwave frequencies. They proved extremely successful, offering reduced size, weight and cost
coupled with improved electrical performance, production uniformity and reliability [1]. However, many problems were
encountered when the first attempts were made, to use this technique at mm-wave frequencies [2]. Microstrip circuits
suffered from increased radiation losses, dispersion, unwanted coupling and discontinuity effects. The parasitic effects
associated with the circuit assembly also caused problems and increased the production spread of performance.
These problems have been addressed over time; thinner substrates can be used to allow operation at mm-wave
frequencies with reduced dispersion and radiation losses. Parasitics can be minimised and unnecessary discontinuities
avoided. For unavoidable discontinuities, more accurate models are now available and accurate simulation of their
effects is possible. MIC technology is now a proven technique for the fabrication of mm-wave circuits [3, 4].
This paper details the design, fabrication and measurement of MIC based mixers and microstrip filters operating at
43GHz.