Transformer-Coupled Frequency Converter for DC Offset Reduction
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Solution Overview
Problem
Conventional direct-conversion receivers face challenges with DC offset due to close frequency proximity between poly-phase local oscillating and radio frequency signals, leading to increased circuit complexity and chip area consumption when using sub-harmonic mixers to mitigate this issue.
Innovation Solution
A frequency-converting circuit employing a transformer-coupling approach with single input port transduction units and switching units to generate quadrature RF signals, reducing the need for complex phase shifting and minimizing power consumption and circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional sub-harmonic mixers are used to reduce DC offset, then isolation between mixer and input terminal is improved, but device complexity increases due to requiring multiple poly-phase LO signals with different phase displacements
Solution Approach 1:
The patent combines the functions of multiple sub-harmonic mixers into a single integrated frequency-converting circuit. The transformer-coupling approach merges the processing of multiple RF signals (I and Q channels) into one unified structure that generates quadrature baseband signals, eliminating the need for separate mixers and reducing overall circuit complexity while maintaining DC offset rejection.
Solution Approach 2:
The frequency-converting circuit is designed to handle multiple functions within a single architecture: it processes both I and Q RF signals, generates quadrature baseband outputs, and rejects DC offset simultaneously. The circuit can operate with different LO frequencies and phase relationships, making it a universal solution that replaces multiple specialized components.
2Manufacturing precision
If multiple poly-phase LO signals with different phase displacements are generated, then quadrature baseband signals can be obtained, but chip area consumption increases
Solution Approach 1:
The patent merges the phase-shifting functions into a compact integrated structure where the transformer coupling naturally generates the required phase relationships. Instead of using separate phase shifters for each LO signal, the circuit uses a unified transformer-based approach that produces quadrature signals with minimal additional area.
Solution Approach 2:
The circuit achieves quadrature signal generation by changing the frequency parameter of the LO signal rather than relying on complex phase-shifting networks. By using LO signals at different frequencies (fLO and fLO/2) with specific phase relationships, the circuit generates quadrature baseband signals through frequency mixing, reducing the area required for phase manipulation components.
3Object-affected harmful factors
If conventional down converter architecture is used with multiple phase shifters, then DC offset is reduced, but power consumption increases
Solution Approach 1:
The patent combines multiple signal processing functions into a single power-efficient architecture. The transformer-coupled frequency-converting circuit processes both I and Q channels simultaneously using shared components, reducing the total power consumption compared to conventional architectures that use separate mixers and phase shifters for each channel.
Solution Approach 2:
The frequency-converting circuit performs multiple functions (frequency conversion, phase shifting, and DC offset rejection) in a single integrated structure, eliminating the need for multiple dedicated circuits. This multi-functional approach reduces overall power consumption by sharing common components and eliminating redundant functionality.
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 transformer-coupling approach effectively reduces DC offset, saves power, and decreases circuit complexity and chip area by generating poly-phase LO signals with reduced LO frequency, achieving high-linearity performance and efficient frequency conversion.
Implementation Method 1
a transformer-coupling approach is used
Data Source
AI summary
A frequency-converting circuit and a down converter with the frequency-converting circuit are disclosed. The above-mentioned frequency-converting circuit is used for converting an RF signal into a first baseband signal according to a poly-phase LO signal. The frequency-converting circuit includes a coupler, a first transduction unit and a first switching unit. The coupler is for receiving and splitting the RF signal and delivering a first RF signal via the first output terminal thereof. The first transduction unit is for amplifying the first RF signal. The first switching unit is for performing switching operations on the output signal of the first transduction unit and producing the first baseband signal.