High Frequency Design
PASSIVE EQUALIZER
Broadband Amplifier Gain
Slope Equalization with a
Single Passive Component
By Alen Fejzuli, EMC Technology; Ray Kaarsberg, M/A-COM Tyco;
and Nelson Roldan, EMC Technology
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W ith the new and腊猪脚
i n c r e a s i n g
demand of the
I nternet and multimedia
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on the commercial side,
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and the broadband high
data rate communications
links on the aerospace and military side,RF and microwave amplifiers are being ud in many broadband applications in the 2 to 20 GHz range.
Gallium Arnide (GaAs) monolithic microwave integrated circuit (MMI C) ampli-fiers lo gain with increasing temperature and increa in gain with decreasing temper-ature.The ratio of gain change/ºC tends to increa with frequency,making it difficult to compensate the amplifiers in a chain and causing unwanted equalization effects.There are three variables which must be considered when designing GaAs amplifier lineups:gain, gain slope versus frequency,and gain varia-tion versus temperature.
Gain Slope Compensation Versus Frequency and Temperature
Specifications for multifunction asmblies often require positive gain slopes versus fre-quency,within a narrow gain window.The change in gain slope over temperature makes it difficult to fi
t the gain windows at all tem-peratures.An equalizer creates a positive slope over frequency,which only works within a lim-ited temperature range.On the other hand,a microprocessor can t an attenuator gain con-trol level over temperature,which works best over a limited range of frequencies.The fac-tors define the need for a new component to help bridge this gap.
A temperature and frequency variable equalizer is a passive microwave component with an attenuation characteristic that varies as a function of frequency and temperature. The equalizer consists of a temperature vari-able attenuator [1] and a temperature variable filter network where resistance and compo-nent values are changed to generate different respons that vary over temperature and fre-quency.This absorptive temperature variable microwave gain equalizer is produced utilizing at least three different thick film thermistors, with two of the ud on the attenuator and a third one ud on the filter network.The tem-perature coefficients of the thermistors are dif-ferent and are lected so that the attenuator and filter network attenuation change at a controlled rate with changes in temperature while the impedance of the gain equalizer remains significantly constant.Almost any temperature coefficient of resistance can be created for each resistor by properly lecting and mixing different inks when forming the thick film thermistors.Furthermore,the gain equalizer’s characteristic respons can have either a negative or positive temperature coef-ficient of attenuation.
Temperature and Frequency
Variable Equalizer
The equalizer prented here is a variable microwave attenuator,wherein the attenua-tion changes at a controlled rate with changes in temperature and frequency,while the impedance remains significantly constant.
Gain equalizers are ud in applications that require signal level control.Level control can be accomplished by either reflecting a por-tion of the input signal back to its source or by
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This article describes the performance of a newly-
developed component intended for amplifier gain slope equalization over fre-quency and temperature From June 2006 High Frequency Electronics Copyright © 2006 Summit Technical Media
22High Frequency Electronics
absorbing some of the signal in the equalizer itlf.The latter ca is often preferred becau the mis-
match that results from using a reflective equalizer can create prob-lems for other devices in the system such as nonsymmetrical two-port amplifiers.I t is for this reason that I
恐怖组织Figure 1 · Gain for a TWA from 2
GHz to 20 GHz without compensa-
关于离别的句子tion.
Figure 2 · Temperature and fre-Figure 3 · Gain over frequency for
24High Frequency Electronics
Gain (attenuation) versus frequency for the five example equalizers.
Reference
忠实是什么意思George D.Vendelin,Anthony M.Pavio,Ulrich L.Rohde,Microwave
Circuit Design Using Linear and Nonlinear Techniques,John Wiley & 26High Frequency Electronics
