CMOS Digital Attenuator Phase Error Reduction
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Solution Overview
Problem
Existing attenuators face significant challenges in reducing phase variations between transmission and attenuation phases of signals without increasing insertion loss and design complexity, particularly in phased-array antennas and beam-forming systems.
Innovation Solution
A low phase variation attenuator design incorporating a combined attenuation path and phase network, utilizing a grounded parallel connection of a resistor and capacitor in series with an attenuation transistor, connected to a two-resistor voltage divider, which maintains minimal phase difference and insertion loss across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional attenuator designs are used to reduce phase variations, then phase accuracy improves, but insertion loss and design complexity increase significantly
Solution Approach 1:
The attenuator is divided into two independent paths: a reference path with a reference transistor and an attenuation path with an attenuation transistor. Each path is optimized independently, allowing phase accuracy to be improved in the attenuation path without compromising the simplicity of the overall design. The segmentation enables separate optimization of phase characteristics while maintaining manageable circuit complexity.
Solution Approach 2:
A compensation network consisting of a compensation transistor and associated resistors is introduced as an intermediary element to actively compensate for phase variations in the attenuation path. This intermediary structure corrects phase errors without requiring complete redesign of the entire attenuator, thus improving phase accuracy while adding only moderate complexity through a dedicated compensation mechanism.
2Measurement precision
If conventional attenuator designs are used to reduce phase variations, then phase accuracy improves, but insertion loss increases significantly
Solution Approach 1:
The invention employs parameter changes by adjusting the gate voltages of the reference transistor and attenuation transistor independently, and by optimizing the resistor values in the compensation network. These parameter adjustments enable precise control over the phase characteristics and insertion loss, allowing the system to achieve high phase accuracy while maintaining low insertion loss through optimized component values rather than complex structural changes.
Solution Approach 2:
The compensation network provides a feedback mechanism where the compensation transistor responds to voltage changes at its gate terminal to actively correct phase variations in the attenuation path. This feedback approach dynamically adjusts the phase characteristics to maintain accuracy across different attenuation levels and frequencies, improving phase accuracy without requiring excessive insertion loss to achieve the correction.
3Adaptability or versatility
If wide frequency range operation is achieved, then adaptability improves, but maintaining low phase variation and insertion loss becomes more difficult
Solution Approach 1:
The attenuator employs dynamic control through independently adjustable gate voltages on the reference transistor and attenuation transistor, allowing real-time adaptation to different frequency conditions. The compensation network also dynamically responds to changing operating conditions by adjusting its compensation action based on the instantaneous voltage states, enabling the circuit to maintain low phase variation across a wide frequency range through active adaptation rather than fixed design parameters.
Data Source
AI summary
A low phase variation attenuator uses a combined attenuation path and a phase network to significantly reduce a phase error between a reference signal and an attenuated signal without degrading the insertion loss. A grounded parallel connection of a resistor and a capacitor is employed in series with an attenuation transistor, which is connected to a middle of a two resistor voltage divider. The two resistor voltage divider includes two resistors of equal resistance that are connected in a series connection. The two resistor voltage divider is connected in a parallel connection with a reference transistor, which functions as a main switch for the transmission or attenuation of a radio frequency (RF) signal.