Suspended Stripline Filter

Suspended Stripline Filter: How They Perform Their Tasks

Electronic filters come in a wide array of shapes and sizes, and perform a wide assortment of functions, from filtering noise and hissing sounds in musical instruments and music players, to filtering signals and frequencies in satellite and wireless transmissions, and more. And while filters are generally categorized as either high pass, low pass, band pass or band stop, these four main categories are also divided into different subcategories and sub-specialties, among which include electronic stripline filters. Let’s find out what suspended stripline filters are, and what they do.

Who Coined The Term “Stripline”?

Before we delve into the design, and functions of suspended stripline filters, let’s first find out who created, or invented, the term “stripline”. Electronics experts and historians say that a Long Island, New York-based Airborne Instruments Labs engineer named R. Barrett coined the term, which is referred to as “a conductor that’s sandwiched by dielectric, in between ground plane pairs, just like coaxial cables”.

The standard stripline is made by engraving or placing circuitry on a substrate on the ground plane, and by adhesively attaching a second substrate on top to achieve the second ground plane.

The Ups And Downs Of Striplines

Constructing conductors or filters using the stripline design offers a couple of advantages. For starters, stripline looks, and works, just like coaxial cables, because it’s a TEM, or transverse electromagnetic transmission line media, indicating that it is non-dispersive, in all types of frequencies.

According to electronics and communications experts, stripline filters also offer much better, or more-improved, bandwidth as compared to their microstrip counterparts. And they have no lower cut-off frequency too.

Stripline filters can also be utilized to route radio-frequency signals across each other much easily, especially when an “offset” stripline is utilized. However, stripline is a bit harder and more costly to design and fabricate as compared to microstrip, because the lumped-element and active components may need to be attached, or installed, in the middle of the groundplanes.

And since a stripline is a bit complex to construct, there’ll be a chance that the designer could end up with a stripline board thickness that’s 4 times thicker than a microstrip board, just to attain the equivalent (or required) transmission line loss.