Switchable All-Pass Phase Shifter for Impedance-Matched Tuning
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Solution Overview
Problem
Existing phase shifters, such as those described in Non-Patent Literature 1, have a uniquely determined frequency characteristic of phase shift, leading to a fixed phase-shift error in desired frequency bands, which limits the ability to achieve a desired amount of phase shift.
Innovation Solution
A phase shifter design that includes a first all-pass filter and a second all-pass filter, each with specific configurations of inductors and capacitors, along with switching switches to select between the two filters, allowing for adjustable element values based on impedance matching, frequency, and a variable, thereby achieving a desired frequency characteristic of phase shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a combination of lumped-parameter elements that achieves an amount of phase shift and a matching condition is uniquely determined, then the phase shifter can achieve impedance matching, but the frequency characteristic of the amount of phase shift is also uniquely determined, resulting in a phase-shift error in desired frequency bands
Solution Approach 1:
The patent applies parameter changes by introducing a variable element (such as a variable capacitor or inductor) into the all-pass filter circuit. This variable element allows the phase shift amount to be adjusted independently while maintaining impedance matching conditions. By changing the parameter values of the reactive elements, the circuit can achieve different phase shift characteristics without compromising the impedance match, thereby resolving the contradiction between reliable impedance matching and accurate phase shift control.
2Reliability
If the element values of the all-pass filters are fixed to achieve impedance matching, then the matching condition is satisfied, but the frequency characteristic of the amount of phase shift cannot be adjusted to match desired specifications
Solution Approach 1:
The patent implements dynamics by making the element values of the all-pass filter adjustable rather than fixed. The variable element allows the circuit to adapt its phase shift characteristics dynamically while maintaining impedance matching. This dynamic capability enables the phase shifter to be tuned for different frequency characteristics and phase shift amounts, providing versatility without sacrificing impedance match reliability.
3Device complexity
If a uniquely determined frequency characteristic of phase shift is used, then the circuit design is simplified, but the phase-shift error in desired frequency bands increases
Solution Approach 1:
The patent resolves this contradiction by introducing a variable element that allows parameter adjustment. While the basic circuit structure remains relatively simple, the ability to change parameter values enables precise control over phase shift characteristics. This approach maintains design simplicity while achieving high phase-shift accuracy through parameter optimization rather than complex circuit topologies.
Data Source
AI summary
A phase shifter includes: a first all-pass filter; a second all-pass filter; a first switching switch to provide a signal to either one of the first all-pass filter and the second all-pass filter; and a second switching switch to select the signal having passed through the first all-pass filter or the signal having passed through the second all-pass filter, wherein the first all-pass filter includes two inductors and three capacitors, and the second all-pass filter includes two inductors and three capacitors, or the first all-pass filter includes three inductors and two capacitors, and the second all-pass filter includes three inductors and two capacitors, and element values of elements included in the first all-pass filter and element values of elements included in the second all-pass filter are determined by impedance at which impedance matching is achieved, a frequency of the signal, and a variable.