We keep reading about the complexity and cost of analog and RF/wireless ASICs. It seems to us that this is not an entirely true picture. Analog and RF /wireless ASICs do not necessarily have to be complex or expensive ( in fact is many cases they are deliberately kept simple ( e.g a LNA ). A matched pair of transistors for high frequency or high accuracy service can be an analog or RF/wireless ASIC. A high frequency LC filter or a high frequency monolithic microwave filter can be a RF/wireless ASIC. A simple 32 bit analog EEROM for trimming references and other circuits can be an ASIC. Customized low noise transistors with a small amount of circuitry can be an analog or rf/wireless ASIC. Fabrication can also be relatively low cost. Please visit the Signal Processing Group Inc., website or contact us to discuss your needs. We are sure we can come up with a relatively low cost solution to your analog and Rf/wireless ASIC or module needs.
The mapping between the symbol constellation points for various values of I and Q is described by a set of waveforms. In QPSK there are 4 symbols, labeled 11, 01, 10, 00. So each symbol conveys two bits. These symbols may be coded in a number of ways. A set of graphical displays show one way of doing this. The symbols themselves are also composed of waveforms with differing phases. These waveforms are used to build the composite QPSK signal. This document should be read in conjunction with an earlier brief paper on QPSK. (http://www.signalpro.biz/wordpress/?p=707)
This paper is an attempt to explain how the last line of the graphical QPSK signal waveform was constructed. In that construct two cycles of each symbol waveform were used. Note that negative values are simply drawn by inverting the symbol waveform.
Please visit the Signal Processing Group Inc., website and choose the complimentary items link. The files can be accessed from there.
In a significant number of cases in RF and MW design, signals need to be combined or split ( depending on the application). There are a number of techniques to do this. One of the popular ones is the use of the Wilkinson divider. Invented in 1960, when Wilkinson described a device that separated one signal into n equal signals of equal phase and amplitude. The Wilkinson divider has become a popular way to split or combine signals.The device is bilateral and can be used as a splitter or a combiner.
A brief paper that describes the basics of a 2 way Wilkinson divider/combiner, its basic design equations for a starting design ( that may need to be fine tuned further, depending on the application) and its layout are described in a brief paper released by Signal Processing Group Inc. Please visit our website and check under the “Complimentary Items” link.
In many communication systems, the CCDF ( or complementary cumulative distribution function is used as a mathematical tool to calculate many parameters of the system. The CCDF is simply defined as the plot of relative power levels against their probability of occurrence. As such it is a statistical construct.
A recent post that described a set of RF power amplifier specifications has been updated to include two other specifications related to the linearity of the RFPA. These are the AM – AM conversion and AM-PM conversion specifications. Please access the specifications from the complementary items link on the Signal Processing Group Inc., website.