Stripline

Updated June 29, 2004

Check out other types of microwave transmission lines here!

Stripline was, according to David Pozar's fine textbook "Microwave Engineering" was invented at by R. Barrett in the 1950s. Airborne Instruments Labs (Long Island New York, gone but spawned present day companies such as MITEQ) coined the term "stripline", while others such as Sanders (Nashua, NH, now part of British Aerospace Engineering) applied the tradename "Tri-plate".

Stripline is a conductor sandwiched by dielectric between a pair of groundplanes, much like a coax cable would look after you ran it over with your small-manhood indicating SUV (don't get me started on that subject, I am a closet tree hugger).

Other variants of the stripline are offset strip line and suspended stripline.

For stripline and offset stripline, because all of the fields are constrained to the same dielectric, the effective dielectric constant is equal to the relative dielectric constant of the chosen dielectric material. For suspended stripline, you will have to calculate .

The major advantage of stripline is fantastic isolation between adjacent traces (as opposed to microstrip). Stripline can be used to route RF signals across each other, especially when offset stripline is used. The disadvantage of stripline is that lumped-element and active components either have to be buried between the groundplanes (generally a tricky proposition), or transitions to microstrip must be employed as needed to get the components onto the top of the board.

A simplified equation for line impedance of stripline is given as:

We will put in a more accurate calculator one of these days, along with some calculators for offset stripline and suspended stripline.