Millimeter-Wave Amplifier Gain Control Without Waveform Distortion
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Solution Overview
Problem
Millimeter-wave communication systems with phased-array antenna systems require fine gain control to maintain amplifier linearity and alignment among antenna elements, especially at maximum power conditions, but existing methods distort output voltage waveforms by altering differential mode impedance without affecting common mode impedance.
Innovation Solution
A variable gain control system is implemented using an amplifier coupled with a matching network, featuring a transconductance amplifier and a variable gain control circuit with adjustable resistance segments and a center node coupled to AC ground, allowing independent resistance variation to provide linear gain control without distorting the output voltage waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If differential mode impedance is altered for gain control, then amplifier gain is adjusted, but output voltage waveform is distorted
Solution Approach 1:
The load impedance control is segmented into independent differential mode and common mode components. The differential mode load impedance is controlled through a first control signal to adjust gain, while the common mode load impedance is controlled through a second control signal to maintain waveform integrity. This segmentation allows independent optimization of each mode's function.
Solution Approach 2:
The patent changes the impedance parameters by controlling both differential mode and common mode load impedances separately. By adjusting the common mode load impedance in response to changes in differential mode load impedance, the system maintains optimal operating conditions and prevents waveform distortion while achieving gain control.
2Ease of operation
If gain control is implemented in traditional methods, then amplifier output is adjusted, but amplifier linearity is degraded
Solution Approach 1:
The patent implements gain control by changing the differential mode load impedance parameter while simultaneously adjusting the common mode load impedance parameter to compensate for linearity degradation. This dual-parameter control approach maintains amplifier linearity even as gain is adjusted, resolving the contradiction between ease of gain adjustment and maintenance of amplifier linearity.
3Manufacturing precision
If fine gain control is provided, then amplifier alignment is improved, but system complexity increases
Solution Approach 1:
The matching network is designed to perform multiple functions simultaneously: it provides differential mode load impedance control for gain adjustment, common mode load impedance control for waveform maintenance, and automatic alignment of amplifier elements. By making the matching network universal and multi-functional, the patent achieves fine gain control and amplifier alignment without proportionally increasing system complexity.
Data Source
AI summary
An amplifier circuit for a millimeter wave (mmW) communication system includes an amplifier coupled to a matching network, and a variable gain control circuit in the matching network, the variable gain control circuit having an adjustable gain control resistance, the adjustable gain control resistance having adjustable segments and a center node therebetween, the center node coupled to an alternating current (AC) ground.