Asymmetric 90° Coupler Layout for Low-Frequency Impedance Matching
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Solution Overview
Problem
Existing 90° couplers face challenges in reducing circuit size when handling low-frequency radio frequency signals due to the need for increased electrostatic capacity, leading to larger circuit dimensions.
Innovation Solution
A 90° coupler design with asymmetric capacitor connections, where the second capacitor has a smaller electrostatic capacity than the first, allowing for reduced circuit size while maintaining effective signal splitting and combining functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electrostatic capacity of the capacitor is increased to achieve impedance matching for low-frequency signals, then the impedance matching is improved, but the circuit size increases
Solution Approach 1:
The patent applies asymmetry by configuring the two capacitors with different electrostatic capacities (C1 ≠ C2) and arranging them in an asymmetric topology where one capacitor is connected in series with an inductor while the other is connected differently. This asymmetric configuration enables effective impedance matching for low-frequency signals while reducing the required electrostatic capacity compared to conventional symmetric designs, thereby reducing circuit size.
Solution Approach 2:
The patent changes the parameter of electrostatic capacity by using capacitors with specifically designed different capacity values (C1 and C2) rather than identical values. This parameter change allows the circuit to achieve proper impedance matching for low-frequency operation while minimizing the overall circuit size through optimized capacity distribution.
2Reliability
If the electrostatic capacity of the capacitor is increased to maintain signal splitting function at low frequency, then the signal splitting performance is improved, but the circuit complexity increases
Solution Approach 1:
The asymmetric capacitor configuration (different capacities C1 and C2 with different connection topologies) enables the circuit to maintain effective signal splitting functionality at low frequencies without requiring uniformly large capacitors. This asymmetric design achieves the splitting function with more efficient component utilization, reducing overall circuit complexity.
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 design achieves a compact circuit size with improved impedance matching and reduced loss, ensuring efficient signal phase difference and impedance conversion, suitable for Doherty and balanced amplifiers.
Implementation Method 1
a second inductor that has a first end connected to the second end of the first capacitor and a second end connected to the ground through a resistance element, and that electromagnetically couples to the first inductor
Data Source
AI summary
A 90° coupler includes a first capacitor having a first end connected to a first terminal and a second end connected to a first amplifier, a first inductor having a first end connected to the first terminal and a second end connected to a second amplifier, a second inductor having a first end connected to the second end of the first capacitor and a second end connected to the ground through a resistance element and electromagnetically coupling to the first inductor, and a second capacitor having a first end connected to the first terminal and a second end connected to the second end of the second inductor.