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.
In many calculators dBs and Nepers are used as (for example) units of attenuation. Here is the conversion between the two of them. 1 Neper= 8.6860000037 db and, 1 dB = 0.1151277918 Np. Please visit the Signal Processing Group Inc. website for more interesting information and services delivered.
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 spg@signalpro.biz. 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.
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.
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 www.signalpro.biz 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.
An antenna test is described for testing an antenna quickly for sorting good from bad antennas. It can be done relatively quickly and the results obtained can be post – processed to yield many other parameters that can help in specifying the antenna. Please visit the “complementary” section of the Signal Processing Group Inc.’s website for more detailed information.
CIC ( Cascaded Integrator Comb) filters are a popular way to do decimation ( as one of a chain of filters). Usage is in delta – sigma ADC’s and similar circuits. A recent paper by Signal Processing Group Inc. describes the design process of such a filter. This paper is available on the Signal Processing Group Inc. website under the “Complementary” menu item.
There are at least three fundamental parameters we need to know when designing a modulator for a delta sigma ADC. These are: The ENOB or equivalent number of bits, the modulator order and the rank of the quantizer. These are the inputs to the modulator design algorithm. Signal Processing Group Inc., provides a calculator to evaluate what the SNR will be and the oversampling ratio. Please visit www.signalpro.biz/calc_delsig1.htm
to invoke the calculator.
As the frequencies of operation get higher and higher, we find that the component manufacturers are switching to chip level devices rather than packaged parts. The reasons for this are many and varied, but suffice it to say that it is happening. Thus if you are developing a module level product for high frequencies then you should be prepared for this and find appropriate assembly facilities or vendors who will not only fabricate a board for you but also be able to do COB ( chip on board) assembly. Please visit the Signal Processing Group Inc. website for other interesting articles and information on our services and products.
Many electronic circuits such as amplifiers are subject to instability or oscillation under certain conditions. usually these boil down to input and output terminations. There are some favorable or type b terminations which do not cause oscillation while the unfavorable terminations or type a terminations cause oscillation. The stability circle is tool that allows designers to evaluate the effect terminations have on their design using a graphical technique with the help of the Smith Chart. To learn more and understand the process, please visit and read the article in the Signal Processing Group Inc. website that explains the technique.