Researchers at Cardiff University have simulated a novel package for RF MMICs that offers high performance at low cost.

Currently high performance RF applications use low-temperature co-fired ceramic (LTCC) substrates, but these are expensive. Plastic SMT alternatives are cheaper but their RF behaviour is not as good.

In a paper given at the IEEE’s International Microwave Symposium in San Francisco, PhD student Zaid Emmanuel Aboush described a liquid crystal polymer (LCP) package that sustained 20dB of return loss and 0.3dB insertion loss up to 50GHz.

The via allowing contact from one side of the package to the other was tweaked to make the package look like a 50Ohm transmission line.

“Any non-50Ohm behaviour of the package will produce either a low-pass of high-pass characteristic, which will distort the performance of the MMIC,” said one of the researchers, Professor Paul Tasker.

“If we can arrange for the capacitor-inductor-capacitor [structure] to act like a network… that will synthesise our transmission line, retaining a really good return match.”

Tasker said the paper attracted a lot of interest at the conference. “We were surprised,” he said.

Cardiff School of Engineering