Balanced Duplexer With Impedance Inverters for Low-Loss Isolation
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Solution Overview
Problem
Existing electrical balanced duplexers face challenges in providing effective isolation between transmit and receive signals, especially under non-ideal operating conditions, leading to less than optimal performance in filtering receive signals from transmit signals and vice versa.
Innovation Solution
The incorporation of impedance inverters and notch filters into the electrical balanced duplexer, in conjunction with impedance gradients and tuners, enhances the duplexer's ability to isolate receive operations from transmit operations by providing specific impedances that effectively block or allow signals to pass through based on frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical balanced duplexer uses impedance gradients and balun circuits to isolate transmit and receive signals, then frequency division and signal isolation are achieved, but insertion loss is high (6-8 decibels) and isolation effectiveness is reduced under non-ideal operating conditions
Solution Approach 1:
The patent introduces impedance inverters as intermediary components between the balun circuits and the antenna. These inverters act as mediators that transform the impedance characteristics seen by the balun circuits, enabling them to operate more effectively. The impedance inverter converts the low impedance presented by the balun at certain frequencies to a high impedance, and vice versa, thereby improving both isolation and reducing insertion loss without requiring fundamental changes to the balun circuit topology
Solution Approach 2:
The patent employs impedance inverters that dynamically change the impedance parameters of the circuit based on frequency. By transforming the impedance characteristics at different frequency points, the system achieves better isolation between transmit and receive paths while maintaining lower insertion loss. The impedance inverter effectively inverts the impedance transformation ratio, converting a transformation ratio of K to 1/K, which optimizes the matching and isolation performance
2Adaptability or versatility
If electrical balanced duplexer uses balance-unbalance transformer circuits with impedance gradients, then transmit and receive signals can be separated by frequency, but the isolation between transmit and receive operations is insufficient under non-ideal conditions
Solution Approach 1:
The impedance inverter serves as an intermediary component that enhances the isolation performance of the existing frequency division mechanism. It does not replace the balun circuit's frequency separation function but rather amplifies and optimizes its effect by transforming impedance characteristics, ensuring that signals at different frequencies experience the desired impedance mismatch for effective isolation
Solution Approach 2:
The patent applies impedance inversion to reverse the impedance transformation effect. Instead of the balun circuit transforming impedance in one direction, the impedance inverter transforms it in the opposite direction, creating a double inversion effect that enhances isolation. This inversion principle allows the system to achieve better isolation by presenting opposite impedance characteristics to different frequency signals
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 improves the duplexer's insertion loss and isolation between transmit and receive operations, reducing insertion loss from approximately 6-8 decibels to 1-3 decibels and achieving better isolation, especially when operating in full duplexer mode.
Implementation Method 1
The windings may couple to an impedance gradient that provides an impedance at a corresponding frequency to enable/block signal traversal through the balun
Implementation Method 2
Each balun circuit may include windings coupled to impedance gradients that provide an impedance that corresponds to a frequency of a signal to enable the signal to pass through or to block the signal
Data Source
AI summary
A duplexer may be used to isolate a transmitter and a receiver that share a common antenna. By using impedance gradients to provide impedances that cause balance-unbalance transformers (balun) of the duplexer to cut-off access to the common antenna rather than duplicate the antenna impedance, the duplexer is balanced. Such cut-offs may have a lower insertion loss than a duplexer that merely duplicates the antenna impedance to separate the differential signals of the receiver and transmitter from the common mode signal.