Phase-Switching Variable Attenuator for High-Frequency Isolation
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Solution Overview
Problem
Phased array systems face challenges in achieving high-frequency signal attenuation with low isolation performance, leading to phase errors and large combining losses in phase shifters, particularly due to the use of π-type variable attenuators with passive circuits that struggle with high-frequency signals.
Innovation Solution
A phase-switching variable attenuation device is designed, incorporating two 0-π VATTs with switch units, transformers, and signal distribution units to achieve high attenuation while maintaining phase accuracy, using FETs and resistive elements to control signal amplitude and phase, and employing capacitors to cancel leakage signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If π-type variable attenuators with passive circuits are used for high-frequency signal attenuation, then attenuation function is achieved, but isolation performance deteriorates and phase errors increase
Solution Approach 1:
The patent divides the single variable attenuator into two separate 0-π VATTs that process differential signals independently. Each VATT handles one signal path (IN1 or IN2), and their outputs are combined through signal distributers. This segmentation allows each attenuator to operate optimally without the isolation problems of the previous single attenuator design, reducing phase errors and combining losses.
Solution Approach 2:
The patent inverts the signal flow configuration by using two input signals (IN1 and IN2) that are 180 degrees out of phase, rather than using a single input signal. The signal distributers cross-connect the inputs to the VATTs (IN1 to VATT2, IN2 to VATT1), creating an inverted signal path configuration that improves isolation performance and reduces phase errors.
2Adaptability or versatility
If phase shifters are designed to shift phase from 0 to 360 degrees, then phase control range is improved, but amplitude stability deteriorates
Solution Approach 1:
The patent changes the operational parameters of the variable attenuators by using 0-π VATT configurations with FETs and resistive elements instead of traditional π-type attenuators. This parameter change enables the system to achieve full 0-360 degree phase shifting while maintaining amplitude stability, as each VATT can independently control its signal path without affecting the other, preventing amplitude variations during phase transitions.
Data Source
AI summary
A variable attenuation device includes: a first variable attenuator configured to receive a first signal through a first input end, attenuate the first signal by an amount of attenuation according to a control voltage, and output the attenuated first signal through a first output end, the first signal being one of a pair of differential signals having a 180-degree phase difference; a second variable attenuator configured to receive a second signal through a second input end, attenuate the second signal by the amount of attenuation according to the control voltage, and output the attenuated second signal through a second output end, the second signal being the other one of the pair of differential signals; a first signal distributer configured to distribute the second signal to the first output end; and a second signal distributer configured to distribute the first signal to the second output end.