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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...

When the RF test system and the device-under-test (DUT) both have coaxial connectors, hooking them together to make a measurement is easy. However, as radio-frequency integrated circuits (RFIC) have shrunk in size, traditional coaxial connectors are no longer useful. With the multitude of RF component sizes and shapes found...

Precise device characterization is the starting point of any good circuit design. This task can be particularly challenging when the device is a high power transistor having low input and output impedances. For devices working only under pulse conditions, specific test benches exist 1 but are rather complicated and...

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...

A comb generator is a device with outputs that are multiple harmonics of an input signal. The output spectral tone lines are uniformly spaced at integer multiples of the input reference. A spectrum analyzer display of the output looks much like the teeth of a comb, which is how...

Wireless communications handsets are increasing in functionality through the addition of features such as GPS, color displays and PDA functions. At the same time the handset is maintaining a roughly constant price and size target. Because of this trend, handset manufacturers are requiring higher levels of integration from component...

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...

In multi-carrier power amplifiers, a feedforward technique is generally adopted due to its extremely linear and broadband characteristics. 1 However, the feedforward technique requires large circuits and is expensive because of its complexity. It uses two cancellation paths, and delay lines are inserted in each path to adjust the...

For the third-generation (3G) mobile radio standards, a very high linearity transmitter that can support high crest factor signals is necessary. High linearity and high efficiency are critical issues in amplifier design. In fact, as the power amplifier operates close to the saturation region where both high efficiency and...

PIN diodes have been widely used in a variety of microwave and RF applications, including antenna switches, phase shifters and attenuators. PIN diode attenuators are used extensively in automatic gain control (AGC) and RF leveling applications. Most PIN diode attenuators control the attenuation characteristics through the forward bias current....