Air stripline

Many useful circuits can be constructed with air stripline and it is also easier to achieve strong coupling between components in this technology than with other planar formats.

The purpose of the solid dielectric is mechanical support for the conductor,[3] but it is made as thin as possible to minimise its electrical effect.

[5] The other method of construction uses a more substantial solid metal bar as the strip, supported on periodically spaced insulators.

In such applications the corners of the conductor cross-section may be rounded to prevent high field intensities and arcing occurring at those points.

[6] The insulators are electrically undesirable; they detract from the goal of having a purely air dielectric, add discontinuities to the line, and are potentially a point at which tracking can occur.

[11] Air stripline can achieve strong indirect coupling in these components more easily than other planar formats.

This limit is governed by the maximum resolution of the printing process and, in power applications, by the electric field strength between the lines.

[12] Stripline was invented by Robert M Barrett of the US Air Force Cambridge Research Center in the early 1950s.

Early on, stripline was the planar technology of choice, but has now been superseded by microstrip for most general purpose applications, especially mass-produced items.