Touchstone file

A touchstone file is a composite file composed of s parameters of a device in a particular format. It allows certain CAD tools ( or the engineer) a way to analyze the device using s parameters for various operating modes and extract valuable information about the performance of the device. Please visit the Signal Processing Group Inc. website and access more details about the touchstone file under the complementary menu.

S – parameters

S – parameters are the most popular parameters used in the design, development, test, measurement and related tasks for RF, microwave and mmWave . This post deals with the very basics of s parameters. It can be used by newcomers to the field or seasoned engineers who may just want to refresh themselves about these parameters. Please visit the Signal Processing Group Inc. website and the complementary page to access the details.

K band RFPA size reductions

I find it interesting that as I progress through RF/Microwave design how sizes of the circuits shrink continuously with operating frequency ( medium power). The attached image ( blurred a trifle for proprietary reasons) shows a completed board for a 26.5 Ghz, 2 watt power amplifier. The active device design is done in GAN technology and the board substrate is a RO4350 with gold plating and impedance control ( read $$$ cost). Be that as it may, notice the comparative size in the image. Everything about this board is minute. The SMA connectors are minute, the thickness of the substrate is minute, etc. The design was done using Keysight ADS and (interestingly), QUCS and Octave ( as the math engine). The input and output impedances are 50 Ohm. Anyone interested in more details may contact me on One interesting facet of the module design was the time spent in identifying the SMA connectors for 26.5 Ghz. I find it interesting that most suppliers seem to stop at 18 Ghz for component frequency performance. So 26.5 Ghz is a novelty now I suppose. It may not be for long though. Please visit the Signal Processing Group Inc. website for more interesting technical and business information.

A 26.5 Ghz power amplifier

Directional coupler measures loss of a microstrip line + load easily

Recently we had to find a method to measure the loss of microstrip line connected to a socket pin. We could not access the load end of the line so with some help from a friendly supplier we found a way to measure the loss using the input of the line, a directional coupler and assorted test equipment. The brief paper describing this technique may be found on the Signal Processing Group Inc. website along with other interesting articles under the complementary menu.

K band sma RF connectors

Its interesting how difficult it turned out to be when we were looking for sma connectors for 25 Ghz – 26.5 Ghz. It turns out that sma connectors in this range of frequency are not very common. We finally ended up finding a connector sourced by Amphenol which fits the bill. Please visit our website at for details on how to connect to us for any questions or comments or to check out some free items ( “complementary “) or other technical or service information.