Comparison of Microstrip with CPW for implementation in ku-band region

Hi guys,

We have implemented circuits operating at KU-band in 10 mil alumina substrate ( microstrip based ), all the active circuits used packaged devices, instead of die can we use CPW instead of microstrip ?, Why generally MMIC techniques used CPW INSTEAD OF MICROSTRIP ?

Can we say CPW is better option than that of microstrip at ku-band ?, In case of MIC whether CPW is a good option over microstrip ? We have used 10 mil alumina substrate ( microstrip based) for thr design of LNA and other amplifiers , can we use CPW as alternative ? What is the advantage we may get!

Plz guide.

Hi abhijitrc,

both options have advantages and disadvantages: For example, I work in X/Ku-band region and prefer microstrip because it's easier for me to handle it. I make the pcbs on myself and it is not possible for me to get good results with cpw.
Maybe the attached pdf helps you a little bit:

Sir,
But generally what is thumb rule to select microstrip/ CPW ? I do want a specific application related article .

Thanks

Just some general things that came into my mind:

A CPW has less radiation loss than a Microstrip, but a CPW has more heat loss due to higher current density at the edges. With suitable components, you don't need vias, all microwave signals are on one layer.
CPW has higher risk on undesired propagation modes in case of bends or when using components that don't have well balanced ground connections. This is frequently mitigated by using air bridges at critical locations, but you probably know this already.

In our front end design ( operated at ku-band) we have used 10 mil alumina substrate( microstrip) for the fabrication of LNA, mixer and driver amplifier circuits, since these circuits consume less current can 10 mil alumina substrate( microstrip) is a good alternative? Effective dielectric constant of CPW is less than microstrip and in this case of 10 mil alumina, microstrip we are not using vias( that is also a point of advantage for CPW ), can CPW will further miniaturize the rf frontend package?, generally MMICs are implemented in CPW technology,reason behind that?

Grounding issues can be easily handled by CPW OR microstrip?

Plz do reply if any had experience in this way !

Waiting for a good start!



Plz do reply if any had experience in this way !

Waiting for a good start!