One of the questions we get asked regularly is:
‘why not just integrate a filter in the board stack?’
Our answer to this comes in two parts: First there are manufacturing tolerances to consider, and second there is size.
Manufacturing tolerance for any filter will contribute to a filters performance and can make for some interesting discussions about what was planned for vs the realized filter performance. At mmWave tolerance impacts can become significant and can potentially impact the total cost of an implementation.
Tolerance is a cost to implement driver if one considers the cost of rejection no-conforming boards, and the physical size of the filter implementation is another potential cost consideration
An example of a Stripline, 7th order hairpin filter design, at 26GHz
To look at these factors we examined different 26GHz filter manufacturing approaches in our whitepaper Tolerance and Size Analysis for mmWave Filter Manufacturing