As frequencies increase in filters, lumped elements no longer satisfy the requirements for various reasons ( parasitics, accuracy etc). At this point the designer may choose to convert the lumped element filter to a distributed element filter. One of the techniques used is transmission line stubs in the conversion. This technique is described in a white paper released from Signal Processing Group Inc. recently. The paper may be found at http://www.signalpro.biz >> engineer’s corner by interested readers.