Semiconductors / Integrated Circuits

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The basic principle of operation of a MESFET multiplier is that the device is biased for a particular conduction angle, based on the harmonic frequency to be generated. A generalized circuit schematic of a MESFET frequency multiplier is shown in Figure 1 . It can be seen that the...

One of the greatest challenges in characterizing new coaxial interfaces is to determine an accurate test configuration. When precision airlines are not available it is very difficult to obtain a true measurement of the device under test. It becomes necessary to design and implement calibration standards to eliminate the...

High frequency, voltage-controlled oscillators (VCO) are important components of modern RF systems. They are characterized by a set of parameters, which must be analyzed and optimized (for example, phase noise, frequency tuning range, tuning linearity and output power). Many studies are dedicated to the research of VCO characteristics. 1-8...

Enhanced performance is needed from antennas, radomes and other microwave components to support ever-increasing functionality for military communications and electronic warfare (EW) applications. There is a continuing demand for antennas with broader bandwidth, higher power handling and better controlled radiation patterns, while at the same time reducing size and...

In recent years, GSM systems have been deployed using many base transceiver stations (BTS). However, in some areas, such as basements of buildings, tunnels and valleys, there may be no signal, and in some regions fading may occur. These problems can be solved cheaply by implementing repeaters. Figure 1...

When designing dielectric rod antennas for maximum bandwidth, maximum gain, minimum beamwidth and/or low side lobes, design parameters reported in the literature are provided in terms of free-space wavelength. While this methodology lends itself well to other antenna types, it is not as useful when used to describe dielectric...

As is well known, there are two general types of altimeter systems - a pulse radar altimeter and a frequency modulated, continuous wave (FM-CW) radio altimeter. Aircraft radio altimeters typically operate at altitudes from 0 to 8000 feet utilizing separate antennas for transmit and receive. Such radio altimeters have...

This article is intended to provide insight into the effective operation of variable gain amplifiers (VGA) in automatic gain control (AGC) applications. Figure 1 is a general block diagram for an AGC loop. The input signal passes through the VGA to produce the output level to be stabilized. The...

Upcoming generations of cellular radio systems such as GSM EDGE or UMTS require increasing power levels to meet linearity requirements of transmitted signals. To reduce overall costs, equipment manufacturers aim at reducing the number of transistors in their RF power amplifiers. The consequence is a constant demand for bigger...

As wireless systems evolve from second- to third- or fourth-generation, the linearity, efficiency and bandwidth requirements for power amplifiers become more stringent. Many techniques, including feedforward, envelope feedback and manifold types of predistorters, have been employed to effectively satisfy these performance requirements and to reduce the production costs for...