Digital Phase Shifter Output Matching for Low Reflection
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Solution Overview
Problem
The digital phase shift circuit experiences an increase in output reflection coefficient and fluctuation of phase shift amount due to mismatch between the output impedance and the input impedance of the rear-stage circuit, leading to a decrease in electric power supplied to the rear-stage circuit.
Innovation Solution
A digital phase shift circuit is designed with a basic phase shift circuit and an output circuit that decreases the output load of the basic phase shift circuit, including features such as an output signal line with a larger line width than the signal line, and an open stub connected to the output signal line to change the output impedance to a real number.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output impedance of the digital phase shift circuit is matched to the input impedance of the rear-stage circuit, then the output reflection coefficient decreases, but the device complexity increases due to the need for additional output circuit components
Solution Approach 1:
The output circuit is segmented into distinct functional components: an output signal line with controlled impedance, an open stub for reactance compensation, and an output grounding line. This segmentation allows each component to be optimized independently for its specific function while contributing to the overall impedance matching goal.
Solution Approach 2:
The open stub acts as an intermediary element between the basic phase shift circuit and the rear-stage circuit. It provides reactance compensation that bridges the impedance mismatch, enabling better power transfer without requiring direct impedance matching between the main circuit and load.
2Power
If the line width of the output signal line is increased to decrease output load, then the electrical conductance increases, but the area of the circuit increases
Solution Approach 1:
The output signal line has a locally increased line width specifically at the output端 where it connects to the rear-stage circuit. This localized widening increases the conductance and decreases the output load only where needed, rather than increasing the line width throughout the entire signal path.
Solution Approach 2:
The open stub extends in a direction perpendicular to the main signal flow, utilizing the vertical dimension for reactance compensation. This allows impedance matching functionality to be added without significantly increasing the horizontal footprint of the circuit.
Data Source
AI summary
A digital phase shift circuit includes: a basic phase shift circuit including a signal line, a pair of inner lines provided on both sides of the signal line, a pair of outer lines provided outside of the inner lines, a first grounding conductor connected to one ends of the pair of inner lines and the pair of outer lines, a second grounding conductor connected to the other ends of the pair of outer lines, and a pair of electronic switches provided between the other ends of the pair of inner lines and the second grounding conductor; and an output circuit configured to decrease an output load of the basic phase shift circuit in comparison with an input load thereof.