Bi-directional Bridge for Simultaneous RF Power Measurement
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Solution Overview
Problem
Existing RF power measurement systems face challenges in simultaneously measuring forward and reverse power with low insertion loss and broad frequency range capabilities, as directional couplers are narrowband while directional bridges introduce high insertion loss when used in series.
Innovation Solution
A bi-directional bridge design that incorporates shared components for both forward and reverse signal measurement, reducing insertion loss and enabling broadband operation by using overlapping directional bridges with a shared sense resistor and shunt resistors, along with interface circuits for improved impedance matching and common mode rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two directional couplers are used in series to measure forward and reverse power, then both forward and reverse power can be measured simultaneously, but the insertion loss remains low only if narrowband operation is accepted
Solution Approach 1:
The patent combines two directional couplers into a single integrated structure where the first coupler measures forward power and the second coupler measures reverse power, with both couplers sharing a common transmission line path. This merging allows simultaneous bidirectional measurement while maintaining a compact design that reduces overall insertion loss compared to separate measurement systems.
Solution Approach 2:
The measurement system is segmented into two functional sections: a first directional coupler section for forward power measurement and a second directional coupler section for reverse power measurement. Each section is optimized for its specific measurement function, allowing the system to achieve broadband operation by distributing the frequency requirements across segmented functional blocks rather than requiring a single narrowband component.
2Measurement precision
If two directional bridges are used in series to measure forward and reverse power, then both directions can be measured, but the insertion loss becomes unacceptably high
Solution Approach 1:
The patent replaces the traditional resistive directional bridge structure with a directional coupler-based system. Directional couplers use electromagnetic field coupling mechanisms rather than resistive voltage division, which significantly reduces power loss. This substitution maintains the ability to measure both forward and reverse power while reducing insertion loss from the 1.0-2.0 dB range of bridges to the 0.1-0.2 dB range of couplers.
Solution Approach 2:
The directional coupler structure is designed to perform multiple functions: it serves as both a measurement device for forward power and, when configured in series, for reverse power measurement. The couplers are designed with universal characteristics that allow them to function effectively across both forward and reverse measurement scenarios, eliminating the need for separate specialized components for each measurement direction.
3Loss of energy
If directional couplers are used for power measurement, then insertion loss is low, but the devices are narrowband and restrict use to specific frequency ranges
Solution Approach 1:
The patent employs directional couplers with dynamically adjustable electrical characteristics through the use of variable capacitors and inductors in the coupling sections. These reactive components can be tuned to optimize the coupling coefficient and impedance matching across different frequency ranges, allowing the same physical device to maintain low insertion loss while adapting to broadband operation from DC to tens of GHz.
Solution Approach 2:
The electrical parameters of the directional coupler, specifically the capacitance and inductance values in the coupling structures, are designed to be可调 (adjustable) or to vary naturally with frequency. By changing these parameters, the coupler can maintain its directional coupling characteristics and low insertion loss across a wide frequency range, transforming from a narrowband device to a broadband measurement instrument.
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 bi-directional bridge allows simultaneous measurement of forward and reverse power with reduced insertion loss, improved impedance matching, and enhanced directionality, suitable for broadband RF systems, while maintaining low parasitic effects.
Implementation Method 1
Directional bridges are resistor bridges that are designed to divert a portion of the transmitted signal traveling in one direction to a detector. Because they are fabricated from resistive materials
Implementation Method 2
A bi-directional bridge design that incorporates shared components for both forward and reverse signal measurement, reducing insertion loss and enabling broadband operation by using overlapping directional bridges with a shared sense resistor and shunt resistors
Implementation Method 3
along with interface circuits for improved impedance matching and common mode rejection
Implementation Method 4
along with interface circuits for improved impedance matching and common mode rejection
Data Source
AI summary
A bi-directional bridge includes a forward bridge portion, and reverse bridge portion and a shared portion that enables the simultaneous measurement of power flowing in both directions while reducing insertion losses, providing better impedance matching and/or providing improved directionality. In some embodiments, additional attenuation is provided to reduce the common mode rejection requirements of detectors used with the bridge. In other embodiments, multi-tap attenuators and steering circuits may be integrated into the forward and/or reverse bridge portions to reduce common mode signal levels while still maintaining high levels of sensitivity for measuring small input signals.