Passive Mixer Input Matching Using Coupled Inductors
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Solution Overview
Problem
Passive mixers face a tradeoff between input matching and gain stage design, leading to high noise figures and reduced gain due to the need for large series inductors or transformers that increase RF line loss and affect linearity.
Innovation Solution
A passive mixer design incorporating a differential transistor pair with inductively coupled inductors forming three transformers, where the inductors are disposed to increase mutual inductance and are equally wound, along with a gain stage to amplify RF signals, facilitating improved input impedance matching and wide band performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large series inductors or transformers are used to improve input matching, then input matching is improved, but RF line loss increases and gain decreases
Solution Approach 1:
The patent changes the electrical parameters by using inductively coupled inductors with optimized mutual inductance values. Instead of using large series inductors, the invention uses transformers formed by inductively coupled inductors (first, second, and third inductors) with specific coupling coefficients to achieve input matching without the associated RF line losses. The inductors are disposed in specific directions to increase mutual inductance, achieving the desired impedance matching through parameter optimization rather than component size increase.
2Measurement precision
If large series inductors or transformers are used to improve input matching, then input matching is improved, but linearity decreases
Solution Approach 1:
The invention optimizes the mutual inductance parameters of the coupled inductors to achieve input matching while maintaining linearity. The first and second inductors are disposed in directions that increase mutual inductance, and the transformers are designed with specific coupling coefficients that prevent the degradation of linearity. This parameter-based approach avoids the use of large series inductors that would otherwise compromise linearity.
3Power
If gain stage design is optimized for high gain, then gain is improved, but noise figure increases
Solution Approach 1:
The patent introduces inductively coupled inductors as intermediary elements between the RF input and the gain stage. These inductors form transformers that provide impedance transformation and matching, allowing the gain stage to operate at optimal impedance conditions without requiring excessive gain amplification. This intermediary approach enables the system to achieve the desired output level with lower noise figure by avoiding high-gain amplification stages.
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 solution achieves low gain with high linearity and low noise characteristics while minimizing the tradeoff between input matching and gain stage design, resulting in improved gain and linearity with wide band characteristics.
Implementation Method 1
The first inductor, the second inductor, and the third inductor may be each inductively coupled to each other such that three transformers are formed
Implementation Method 2
The first inductor and the second inductor may be disposed in a direction to increase a mutual inductance
Data Source
AI summary
A method and apparatus for input matching of a passive mixer are disclosed. The passive mixer includes a differential transistor pair including a first transistor and a second transistor, a first inductor having one end connected to the first transistor and another end connected to a ground, a second inductor having one end connected to the second transistor and another end connected to a ground, and a third inductor having one end for receiving a radio frequency (RF) signal and another end connected to a ground.