Sunday, January 5, 2014

RSSI: Received signal strength indicator

Recently we received the first silicon of an IF chip designed in 0.6um BiCMOS process. Among other functional blocks is a RSSI circuit. It is composed of three logamps that provide the gain for the IF signal and three RSSI blocks that provide the RSSI signal current output. This current is subsequently converted to voltage through the addition of a resistive/capacitive load ( external) and an optional buffer. The frequency of operation that has been used in tests is 70 Mhz and 280 Mhz. The supply voltage for the chip varies from 3.3V to 6.0V. The IP can be used in other applications if desired. It is also available for purchase and porting as needed. Interested parties can contact Signal Processing Group Inc, through the website or directly at

Sunday, October 27, 2013

RF Power Amplifier Design: Maximum Available Gain.

When designing RF power amplifiers with active devices, it is always good to ask what the device is capable of in terms of power gain when everything is matched. i.e If I matched everything what is the maximum gain / performance I could get out of the device. The answer to this question lies in determining the MAG or Maximum Available Gain of the device. Of course, this is a theoretical quantity because it is not possible to get this performance in practice. The MAG then,is the theoretical power gain of a device when its reverse transfer characteristic or admittance/impedance is set to be non existent. In addition, its input and output ports must be conjugate matched with the source and load impedance respectively.Contact Signal Processing Group Inc., for all your RF Power Amplifier questons or needs. Please review RF power amplifier fundamental concepts at

Tuesday, October 22, 2013

Balun tutorial article

Baluns are used quite extensively in electronic design specially in higher frequency or differential circuits. The term "Balun" is an abbreviation for Balanced - Unbalanced. The implication is that a balun converts an unbalanced signal to balanced signals. In some ways Balun operation is not intuitive. An article describing the basics of baluns is presented by Signal Processing Group Inc.'s technical team and can be accessed at

Saturday, October 19, 2013

Frequency modulation tutorial and simulations

FM signals are everywhere in the RF/Wireless world. Their resistance to noise and clean reception within their range of operation is exploited by many systems. It is useful sometimes to take a look at the theory behind these signals, at least to the point that an intuitive understanding can become beneficial. A recent paper by Signal Processing Group Inc., has been published that provides a description of the mathematics behind FM signals. A set of simulation results are provided that back up the theory. The paper can be accessed at the SPG website, under " free stuff...".

Wednesday, October 2, 2013

Five good reasons to use ASICs and custom modules.

Here are a number of reasons why you would want to develop your own ASIC or custom module, analog, RF or mixed signal. (1) You have developed a product using standard off the shelf components. When you did this your suppliers and their salepersons were all over you. Then the salesperson you knew left, or some other event took place. You no longer have the support from your supplier or distributor. Your project is stalled. Or even worse you have your product in the market and your supplier decides to discontinue the product you are using. The product is selling well. At this point you must have your own ASIC or module if you are to be independent of your supplier and their vicissitudes. It may take time and money but if market and product can support it, you must consider your own custom devices. (2) You have developed your product using off the shelf components. It is selling well. If the market is there and your product addresses the market, be assured your product will be copied and released to your market. You then have a number of choices. (A) Sue 'em. (B) Enhance your product. (C) Protect your IP (D) Exit the market. Only (C) is a palatable choice. You can do this by (E) Patents and trademarks (F) Hide your IP using full custom ASICs and modules (G) Enclose your product in a strong coating of some substance that is difficult to penetrate. Of these options we advocate full custom devices, ASICs or modules. You own the IP here, not your suppliers; It is very expensive to reverse engineer an ASIC and with the proper IP protection techniques ( coatings and other processes) it can be very difficult for a copycat to steal the IP. In addition if a portion of the IP is in firmware then this is an additional layer of protection. (3) Your product has been developed to the point of a demo model and it works. The boards and boxes are large and ungainly. You now have to fit it all in a really small area or enclosure. Again this is a really good reason to make your own custom ASIC or module. (4) Your product has been developed to the point of a demo model. It works fine except that it dissipates a lot of power. Perhaps it is a mobile unit and the batteries are running down. Whatever the case, this again is a really good rationale to get your own custom device. Custom devices can be designed to dissipate very little power using good low power techniques. (5) You have developed a product using discrete off the shelf devices. There are a lot of components on the board. This is causing a size increase and a manufacturing headache. Again use of a custom device is strongly recommended. Not only will the size and power come down but the overall product will be more reliable and easy to manufacture. If you want to learn more or develop your custom devices, please contact Signal Processing Group Inc, at for a no obligation discussion or quotation. SPG uses state of the art semiconductor, PCB and assembly techniques to provide highly cost effective devices that belong to you.

Tuesday, September 24, 2013

Cable models for USB3

A set of measured data were evaluated to establish some design targets for a USB3 front end circuit. This type of cable data is difficult to come by on the web so a TDR was used to measure two different length USB3 cables for only the loss characteristics. The measured data was bolstered by measured data from a USB3 cable manufacturer. The results are: 1 Meter long USB3 cable has a -3dB point at 5 Ghz. A 3 meter cable has its -3 dB point at 2.0 Ghz. A 2 meter USb3 cable has its -3 dB point at 1.6 Ghz.

Small loop antenna design

PCB small loop antenna design is required when designing with RF transmitter and receiver chips available as standard parts from a number of semiconductor manufacturers. A web survey turned up a small number of interesting and instructive articles on this topic. Of these articles only a very few met our purpose. Among these latter we found the most useful to be the one presented by Microchip Technology, Chandler, Arizona. ( Jan Van Niekirk, AN831). We generated an EXCEL spreadsheet using this article as a template for designing these types of antennas. It must be mentioned that this spreadsheet ( as well as the information in the article was found to be a starting point for the design. Some tweaking is still required using measurements.)This spreadsheet is available for download by interested parties from the SPG website located at under Free Stuff.