Microwave Design
The microwave frequency range can be loosely defined as 3 to 30GHz. As operating frequencies extend into this range components become electrically larger and their parastics more significant. Specialist microwave design techniques must be adopted to properly simulate the distributed nature of components, and to account for the effects of discontinuities, parasitics and proximity. 
Plextek’s engineers have many years of experience in the design of microwave components, modules and systems and have an in-depth understanding of the techniques that must be adopted. Our microwave design skills complement our RF design and mm-wave design services, and encompass a wide range of technologies including:
With careful modelling and simulation it is possible to use discrete SMT components to realise microwave circuit functions at frequencies up to around 20GHz. The photograph above right shows the microwave PCB for a dual output, fast switching, low noise, 12GHz synthesiser. The synthesiser uses a dual loop architecture and the PCB contains the VCO, frequency multipliers, amplifiers, filters and sub-harmonic mixer. All of these circuit functions have been realised with low-cost conventional SMT components. The application for this synthesiser was a broadband wireless access system and the ability to manufacture it for a low cost in high volumes was imperative.
Plextek has extensive experience in the design of microwave synthesisers such as this, to download a case study detailing the design of an 8 to 18GHz synthesiser please click here.
Microwave MMIC building blocks (amplifiers, mixers, oscillators, frequency multipliers etc) are becoming increasingly available in surface mount packages. This allows highly functional microwave modules to be designed in short timescales with comparatively low risk. Modules designed in this way can often be manufactured using conventional SMT assembly lines, so easing their introduction into production. The photograph below left shows a Ku-band radar transceiver module designed using this approach.
Plextek also has experience of designing microwave sub-systems using conventional microwave components such as beam-lead packaged PIN diodes. The photograph above right shows a Single Pole 4-Throw (SP4T) microwave switch covering 12 to 19GHz. The design is realised on a low cost Rogers RO4003 substrate and uses beam-lead PIN diodes, SMT capacitors and resistors (0402 and 0201) and printed components. It offers the advantage of covering the entire of Ku-band without using bare die components.
Multi-Chip Modules (MCMs) offer the advantages of high functionality, small size and low parasitics. The photograph below shows a dual channel 2-18GHz MCM front-end module. It was designed for Electronic Support Measures (ESM) applications but is also suitable for use with monopulse or interferometry systems. The module takes two input signals in the 2-18GHz frequency range, received from two external antennas, and converts them to an IF of 500MHz for digitisation. In order to allow this frequency conversion across such a wide operating band, it is realised by first upconverting to an intermediate frequency of 22GHz before filtering and then downconverting to the 500MHz output frequency. Several stages of filtering are realised on the microwave PCB using coupled line and mixed distributed/lumped element designs. The MCM contains a total of 12 GaAs MMICs, including 5 different designs, 4 of which are full custom parts designed by Plextek. The receiver exhibits a gain of 10dB, a noise figure of 7dB and an output referred 1dB compression point of ‑10dBm.
Please contact us if you would like to discuss how you could make use of Plextek’s microwave design services.
