Published January 19, 2007

In an effort to better combine the editorial content of our magazine with our newly developed and retooled on-line presence, we have decided to expand Harlan's RF and microwave engineering advice into a monthly feature that appears in Microwave Journal.

Harlan has selected one question from his "Ask Harlan" column to be featured in the January issue. Harlan will be monitoring the responses and will ultimately choose the best answer to the question. Although all of the responses to the featured question will be posted on our web site, we plan to publish the winning answer in the March issue.

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 February 7, 2007, to be eligible for the participation of the January question.

John McFarland from SNC has submitted this month's question:

Dear Harlan,

Can you explain why the polarization sense of a circularly polarized plane wave changes when it bounces off a reflecting surface? For instance, Right Hand Circular Polarization (RHCP) turns into Left Hand Circular Polarization (LHCP) when undergoing a single bounce off a reflector. The sense of the polarization is defined by the sense (CW/CCW) of rotation of the composite wave (vector sum of the H and V waves) as viewed in the direction of its propagation. When the incident wave undergoes two bounces-say off a dihedral corner reflector, it changes back to the originally incident sense, e.g., RHCP undergoing two bounces will propagate back to the transmitter as RHCP. I know this is what happens from experience, but I have never been able to explain why.

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 for details on hundreds of professional-level books in microwave engineering and related areas (maximum prize retail value $150).


If you experience any difficulty submitting a response to the current Ask Harlan question, please let us know by emailing

Disclaimers: Microwave Journal reserves the right to determine the legitimacy of all responses. The determination of the winning response is not based on any set criteria and is based only on the opinions of the editors of Microwave Journal.

Questions and answers submitted to Ask Harlan are collected for sole use by Microwave Journal and Names and company affiliations will be published with questions and answers that qualify according to our editorial policies. Email addresses are collected in case we need to contact you.

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