Reflectionless Filter Absorbing Stop-Band Energy
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Solution Overview
Problem
Conventional reflective filters cause issues such as sensitivity in mixer performance, instability in high-gain amplifiers, nonlinear effects, potential damage to transmitters, and leakage due to reactive harmonic loading and poor matching, which are not effectively addressed by existing filter designs.
Innovation Solution
A reflectionless filter design that includes a symmetric two-port circuit with both lossless and lossy elements, where the normalized input impedance of the even-mode equivalent circuit is equal to the normalized input admittance of the odd-mode equivalent circuit, allowing for minimal reflections and absorption of unwanted signals in the stop-band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional reflective filter is used, then stop-band rejection is achieved, but reactive termination causes sensitivity in mixer performance and instability in high-gain amplifiers
Solution Approach 1:
The patent converts the harmful reflective termination into a beneficial absorptive termination by placing resistive elements in parallel with the filter capacitors. This transforms the reactive stop-band termination that causes mixer sensitivity and amplifier instability into a resistive termination that absorbs unwanted signals, eliminating the harmful reactive effects while maintaining stop-band rejection.
2Object-affected harmful factors
If a conventional reflective filter is used, then stop-band rejection is achieved, but nonlinear effects and potential damage to transmitters occur
Solution Approach 1:
The patent eliminates nonlinear effects by converting the reactive filter termination into a resistive termination using parallel resistive elements. This resistive termination prevents the reactive loading that causes nonlinear distortion in power amplifiers and protects transmitters from damage by providing a stable, non-reactive load across all frequency bands including the stop-band.
3Reliability
If a conventional reflective filter is used, then stop-band rejection is achieved, but leakage and interference occur due to poor matching
Solution Approach 1:
The patent resolves impedance matching problems by transforming the reactive filter output impedance into a resistive impedance through parallel resistive elements. This provides a stable 50-ohm resistive termination in the stop-band that eliminates standing waves, leakage, and interference caused by reactive mismatches, while maintaining proper signal isolation through the filter's frequency-selective properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The reflectionless filter achieves minimal reflections on input and output ports, infinite return loss at all frequencies, and improved system performance by absorbing unwanted signals rather than reflecting them, reducing instability and interference issues.
Implementation Method 1
reflectionless filters, in which the stop-band portion of the spectrum is absorbed rather than reflected back to the source
Data Source
AI summary
Reflectionless low-pass, high-pass, band-pass, and band-stop filters, as well as a method for designing such filters is disclosed. The filters function by absorbing the stop-band portion of the spectrum rather than reflecting it back to the source, which has significant advantages in many different applications.