Balanced Duplexer Circuit Using Impedance Inverters for Low Loss
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Solution Overview
Problem
Electrical balanced duplexers in wireless communication systems face inefficiencies in isolating receive signals from transmit signals, particularly under non-ideal operating conditions, leading to suboptimal performance in filtering and signal separation.
Innovation Solution
Incorporating impedance inverters and notch filters into the duplexer circuitry, coupled with impedance gradients and tuners, to enhance the duplexer's ability to block receive signals and allow transmit signals to pass through, thereby improving signal isolation and reducing insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical balanced duplexer uses impedance gradients and balun circuits to separate transmit and receive signals, then signal separation is achieved, but isolation effectiveness deteriorates 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 to enhance signal separation. The impedance inverter with characteristic impedance Z0/2 creates a transformed impedance that improves isolation by preventing receive signals from coupling into the transmit path and vice versa, thereby maintaining reliable signal separation under varying operating conditions.
Solution Approach 2:
The patent modifies the impedance parameters of the duplexer circuit by incorporating impedance inverters with specific characteristic impedances (Z0/2). This parameter change transforms the effective impedance seen by the signals, creating better isolation characteristics. The impedance transformation ratio and characteristic impedance values are specifically chosen to optimize the separation between transmit and receive signals, improving reliability under non-ideal conditions.
2Reliability
If electrical balanced duplexer blocks receive signals from traversing the transmitter balun, then transmit signal protection is improved, but insertion loss increases to 6-8 decibels
Solution Approach 1:
The impedance inverter serves as an intermediary that allows transmit signals to pass through with minimal loss while still providing isolation. By transforming the impedance at the balun output, the inverter creates a matched condition for transmit frequencies, reducing reflection and insertion loss. Simultaneously, it maintains the blocking function for receive frequencies, thus protecting transmit signals while minimizing energy loss.
Solution Approach 2:
The patent changes the impedance parameters along the signal path by introducing the impedance inverter. The characteristic impedance Z0/2 and the transformation ratio are specifically selected to optimize both isolation and insertion loss. This parameter optimization allows the circuit to present a low impedance to transmit signals (reducing loss) while presenting a high impedance to receive signals (maintaining protection).
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 effectively enhances signal isolation between transmit and receive operations, reducing insertion loss from approximately 6-8 decibels to 1-3 decibels, and improves the duplexer's performance across various frequency bands, including those used in 5G radio frequency systems.
Implementation Method 1
an impedance inverter with a characteristic impedance of Z0/2, where Z0 is a characteristic impedance of the transmission line
Implementation Method 2
Each balun circuit may include windings coupled to impedance gradients
Implementation Method 3
Incorporating impedance inverters and notch filters into the duplexer circuitry
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.