0/90 Degree Coupler Complex Termination Impedance Circuit
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Solution Overview
Problem
Existing RF amplifier circuits face saturation issues when amplifying signals beyond a certain power level, leading to unwanted distortion, and require multiple amplifiers with lower gain to avoid distortion, resulting in signal losses due to impedance matching networks.
Innovation Solution
A four-port 0/90 degree passive coupler is used to split an RF input signal into two output signals with a 90-degree phase difference, which are then amplified by mismatched amplifiers without impedance matching networks, utilizing a complex termination impedance circuit to maintain a 90-degree phase difference and minimal amplitude imbalance, thereby avoiding signal losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single amplifier is used to amplify RF input signal, then the output power level is high, but the amplifier saturates and produces unwanted distortion
Solution Approach 1:
The single amplifier is segmented into two amplifiers operating in parallel. Each amplifier processes a portion of the signal with lower gain to avoid saturation and distortion. The outputs are then combined to achieve the desired high power output without distortion.
2Object-affected harmful factors
If two amplifiers are used with lower gain to avoid saturation, then unwanted distortion is reduced, but signal losses increase due to impedance matching networks
Solution Approach 1:
The impedance matching networks, which cause signal losses, are extracted and removed from the circuit. The coupler is designed to directly interface with the amplifiers without requiring external matching networks, thereby eliminating the associated power losses while maintaining proper impedance relationships.
3Object-affected harmful factors
If two amplifiers are used with lower gain to avoid saturation, then unwanted distortion is reduced, but device complexity increases due to impedance matching networks
Solution Approach 1:
The impedance matching networks are extracted and eliminated from the design. The coupler is specifically designed to provide direct interfacing between the signal source and amplifiers without requiring additional matching components, thereby reducing device complexity.
4Measurement precision
If all four ports of the coupler are terminated with characteristic impedance Z0, then the phase difference is maintained, but voltage gain is reduced due to power consumption in matching networks
Solution Approach 1:
The power-consuming impedance matching networks are extracted and removed. The coupler is designed to maintain the 90-degree phase difference between output signals without requiring external matching networks, thereby eliminating the associated power consumption.
Data Source
AI summary
The isolated port of a 0/90 degree coupler is terminated by a novel complex termination impedance circuit having a reactance. The absolute value of the reactance is at least two ohms. The coupler receives a signal on its input port, and outputs a first signal on its first output port and a second signal on its second output port. A first load is coupled to the first output port without an intervening matching network. A substantial impedance mismatch exists between the first output port and the first load. A second load is coupled to the second output port without an intervening matching network. A substantial impedance mismatch exists between the second output port and the second load. Despite the substantial impedance mismatches, the first and second signals have a phase difference in a range of from 88 degrees to 92 degrees while exhibiting an amplitude imbalance less than 2 dB.