Image Rejection Mixer Delay Circuit for Phase Error Suppression
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Solution Overview
Problem
Conventional image rejection mixers fail to suppress unwanted frequency components when the 90-degree phase shifter deviates from exact 90 degrees, leading to inefficiencies in filtering out non-desired signals.
Innovation Solution
An image rejection mixer configuration that includes a differential distribution circuit, first and second differential mixing circuits, a combining circuit, and a delay circuit, where the delay circuit delays signals by a consistent amount to ensure effective suppression of unwanted frequency components regardless of the phase shift accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional image rejection mixer uses a 90-degree phase shifter to suppress unwanted frequency components, then frequency component suppression is achieved when the phase shift is exactly 90 degrees, but suppression fails when the phase shift deviates from 90 degrees
Solution Approach 1:
The patent changes the phase shift parameter from a fixed 90 degrees to a variable delay amount. The delay circuit introduces a controllable time delay to the local oscillator signal, allowing the phase relationship to be adjusted dynamically. This resolves the contradiction by making the suppression performance independent of the exact 90-degree phase shift requirement, thereby improving reliability while maintaining frequency component suppression capability.
Solution Approach 2:
The patent introduces dynamic adjustment capability through the delay circuit, which can vary the delay amount based on operating conditions. This transforms the static 90-degree phase shifter into a dynamic system that can adapt to different frequencies and conditions, ensuring reliable suppression performance across varying operating parameters.
2Measurement precision
If a filter is used to suppress unwanted frequency components after mixing, then frequency component suppression is achieved, but device complexity increases
Solution Approach 1:
The patent merges the frequency component suppression function into the mixing process itself by using the delay circuit to create destructive interference for unwanted frequency components. This combines the phase shifting and frequency selection functions into a single integrated approach, eliminating the need for separate filter circuits and thereby reducing device complexity while maintaining suppression effectiveness.
Solution Approach 2:
The delay circuit acts as an intermediary element that mediates between the local oscillator signal and the mixing process. By introducing a controlled delay, it enables the mixing circuits to naturally suppress unwanted frequency components through destructive interference, replacing the need for additional filter components and simplifying the overall circuit structure.
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
This configuration enables the image rejection mixer to consistently suppress frequency components other than the desired signal, even when the phase shift is not exactly 90 degrees, thereby improving signal filtering efficiency.
Implementation Method 1
a delay circuit delaying one of first signals divided by the differential distribution circuit and another one of second signals provided to the second differential mixing circuit by a same delay amount
Data Source
AI summary
An image rejection mixer includes a delay circuit for delaying one of first signals divided by a distribution circuit and a second signal provided to a second mixing circuit by the same delay amount d, or delaying the other one of the first signals divided by the distribution circuit and the second signal provided to a first mixing circuit by the same delay amount d.