Injection locking in transmitter chips

An interesting titbit of knowledge about direct conversion transmitters is the phenomenon of injection locking. If the transmitter is such that right after the modulation the signal goes to the driver/PA ( i.e there is no up-conversion or filtering of any kind between the PA and the modulator and its associated LO, then feedback from the output can cause ( in a number of cases) the LO frequency to shift and lock to another harmonic of a feedback signal. A number of techniques to alleviate this have been investigated because the direct conversion technique is considered by some to be simple and easy to handle ( keep chip size small). For more information or articles visit our website at http://www.signalpro.biz.

High voltage IC design considerations

High voltage IC design is, in our opinion, an art. In terms of the implementation of the functions, simulations and layout it is a taxing endeavor. A number of fabrication vendors who offer high voltage technology try to make it as easy as they can, sometimes by providing some IP. In spite of this there are number of issues and challenges that come up, which the designer only learns through experience. When you are designing at voltages in the range of 500V to 700V and at high currents as well, it becomes a real challenge. It helps if the designer understands some of the parameters of the high voltage device, related to its operation. A white paper on this subject is available in the Signal Processing Group Inc., website located at http://www.signalpro.biz in the engineer's corner. An old adage says " when you are working with high voltage and specially on the bench, keep your left hand in your pocket!"

IC design: The 2-s complement number and DSP

More and more DSP ( digital signal processing) techniques are being used in most complex circuit designs including IC design. In general dsp requires the use of binary numbers. After all dsp is akin to a set of computations yielding a result which may or may not be converted into an analog signal. Both ways. At the input using an A/D and at the output using a D/A. In fact this is the way many recent designs in wireless are being implemented. The number system most often used is the 2-s complement number system. To refresh our memories, a 2-s complement number is formed by taking the binary representation of a decimal number, inverting the bits and then adding a "1" to it. This generates the 2-s complement. A wealth of articles exist on this in the literature and the web. The nice thing about the 2-s complement number is that addition and subtraction becomes very easy. An example is a dual modulus frequency divider. In this circuit we have two counters that start with a loaded number, an initial seed, and then this number is counted down. When the loaded number goes to zero a reset occurs. This is almost the very basic operation required in a dual modulus frequency divider. Note how easy the countdown becomes when implemented with 2-s complement numbers. Have the initial storage in a set of FFs, at each clock invert the contents of the FFs, use a simple adder, add 1 and at the falling edge of the clock recapture the results back into the storage FFs. Each time the clock occurs the FFs count down by '1'. Please visit the Signal Processing Group Inc., website located at http:/www.signalpro.biz for more information on our unique services, technology and technical articles. Contact us on this or other blog posts or articles as needed.

IC Design primitive components available in semiconductor processes

When an engineer is in the process of designing a board level product, he or she instinctively starts a search for off the shelf components that are required to implement the architecture that the engineer has chosen to satisfy the requirements of the product. Yet in some cases a particular function in the architecture cannot be realized using an off - the - shelf component. At this point the engineer may decide that he/she needs a custom part, sometimes an ASIC. The question is what kinds of typical primitive devices can a semiconductor process provide so that the required ASIC can be implemented. A reasonable list of such components is given in http://www.signalpro.biz/asictools.html for the interested reader. Please visit http://www.signalpro.biz for more information.

ICdesign: Integrated chip antennas

As the RF/wireless boards get smaller and smaller, as the active and passive device sizes shrink challenges of the antenna loom larger. Antennas may take up a large percentage of space. Even a few years ago PCB antennas were a solution but that is now no longer a very acceptable solution. The migration path for really small size antennas is the chip or integrated antenna. This tiny device becomes a practical solution when space is at a premium. A number of vendors have started offering this device and depending on the system parameters could be a pragmatic solution. Contact SPG at http://www.signalpro.biz for further details or discussions.

IC Design: Level of simulation for an IC to estimate first pass success

What does the level of simulation have to be to predict the level of success of an IC? What does "level" imply? In the context of simulation of an IC, level implies how much of the IC was included in, perhaps a circuit simulation in a "SPICE-like" simulator. The reason this is so important is that in many cases it is not possible to simulate a full chip, specially if the chip contains mixed signal elements or large and small time constants, etc. Therefore the level of simulation for first pass success should be 100%. i.e the full chip was simulated under operating conditions that are a 100% identical to actual. It is of course not really possible to do this. It usually takes a combination of CAD tools to do this starting from MATLAB-SIMULINK, through circuit simulation and perhaps IBIS type modeling and simulation. In a few cases even more extensive simulation may be performed using Thermal Simulators. So the question remains:what is the level of simulation required for a high degree of confidence in the success of the chip? The answer must surely be that when all the CAD~tools have been used to their ultimate capacity, add a large measure of engineering judgment. This is the only way currently known! Please visit Signal Processing Group Inc.'s website at http://www.signalpro.biz for more technical papers and information.

IC design: ASIC versus analog and mixed signal or RF/wireless ASICs

The term ASIC may be a misnomer for an analog or RF/wireless/MMIC device. When we think ASIC we seem to equate the term to a large digital chip done in very fine line technology costing many millions of dollars, taking a long time, fraught with risk and fear. That is an apt description of the large digital ASIC in our view. However, an analog or mixed signal or RF/Wireless/MMIC custom chip does not play in the same ball park or even in the same neighborhood. For starters these types of devices tend to be smaller and in terms of number of active devices less complex. Sometimes an analog or mixed signal or RF/wireless/MMIC device may only be a couple of devices! Perhaps its time to come up with a new buzzword for these types of devices. Please check out Signal Processing Group Inc website at http://www.signalpro.biz for more information on these helpful devices. If you register you can get a userid and a password for protected areas of the site that contain much valuable information.