Published September 6, 2007

Harlan has selected one question from his "Ask Harlan" column to be featured in the September issue. Harlan will be monitoring the responses and will ultimately choose the best answer to the question. All of the responses to the featured question will be posted on our web site.

You be the expert: Please take a few moments and provide an answer to this month's featured question. Good luck and we look forward to reviewing your answer.

All responses must be submitted by October 9, 2007, to be eligible for the participation of the September question.

Turki Aommran, Student, has submitted this month's question:

Dear Harlan,

I have designed microwave filters with Agilent ADS and the simulation results were perfect, but I have run into a problem with the measured results, which displayed huge differences. What are the effects from this huge impact in my measured results? What caused the mismatching in the reciprocity? S11, s22 should be equal, but in reality s11 is not equal to s22, whereas they have the same shift. What caused the resonance frequency shifting and what causes the drastic insertion losses between the measured and the results? Notice that my microwave filters are a parallel-coupled filter and planar lumped-element filters.

The winning response will win a free book from Artech House, along with an "I Asked Harlan!" t-shirt. In addition, everyone who submits a legitimate response will be sent an "I Asked Harlan!" t-shirt.

If your response is selected as the winner, you'll receive a free book of your choice from Artech House. Visit the Artech House on-line bookstore at www.artechhouse.com for details on hundreds of professional-level books in microwave engineering and related areas (maximum prize retail value $150).

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