RF Power Meter Digital Signal Processing Wideband Measurement
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Solution Overview
Problem
Current RF power measurement systems are limited in measuring complex impedance and require multiple assemblies for varying frequency and power ranges, leading to high costs due to precise machining and high-quality components, and lack the ability to accurately measure across a wide range of RF power parameters.
Innovation Solution
A system comprising a semi-directional coupler connected to an RF power transmission system, with filters to compensate for frequency-dependent coupling, an analog-to-digital converter, a microprocessor for computing RF power parameters, and a field-programmable gate array for executing Fast Fourier Transforms, allowing for the measurement and display of RF power parameters such as voltage, power, impedance, and scattering parameters across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inductive type pickup coils and resistor-capacitor frequency compensators are used, then measurement precision is improved within a limited frequency range, but device complexity and cost increase when attempting to cover wider frequency ranges
Solution Approach 1:
The patent replaces the traditional mechanical/electrical assembly of inductive pickup coils, resistor-capacitor frequency compensators, and diode rectifiers with a digital signal processing system. The coupler outputs are fed directly to an analog-to-digital converter, and all measurements are performed using digital FFT algorithms on a microprocessor, eliminating the need for complex analog frequency compensation networks and reducing assembly complexity while maintaining measurement precision across wide frequency ranges
Solution Approach 2:
The patent changes the operating parameters from analog domain to digital domain. By converting the RF signals to digital samples and performing all measurements through software-based FFT algorithms, the system can accurately measure across wide frequency ranges (1.8 MHz to 450 MHz) without requiring physical reconfiguration or multiple specialized assemblies, thus reducing overall device complexity
2Measurement precision
If high-quality directional couplers with precise machining are used, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent employs a semi-directional coupler that does not require the same level of precise machining and high-quality construction as traditional directional couplers. The system compensates for the lower inherent quality of the coupler through digital signal processing and FFT-based measurements, allowing the use of less expensive, easier-to-manufacture components while maintaining measurement accuracy
Solution Approach 2:
The patent introduces digital signal processing as an intermediary between the coupler and the measurement results. The microprocessor performs FFT transformations and calculations to extract accurate RF parameters from the coupler outputs, compensating for any deficiencies in the coupler's physical construction and allowing the use of less expensive coupler designs
3Adaptability or versatility
If multiple assemblies are used to cover different frequency and power ranges, then adaptability is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a universal measurement system that can handle multiple frequency ranges (1.8 MHz to 450 MHz) and power ranges through a single assembly. The semi-directional coupler combined with digital signal processing and FFT algorithms provides a unified solution that eliminates the need for multiple specialized assemblies, reducing device complexity while maintaining broad adaptability
Solution Approach 2:
The patent implements a dynamic measurement approach where the microprocessor can adaptively process signals across different frequency and power ranges using software algorithms. The system can dynamically adjust its measurement parameters and FFT processing to optimize performance for different operating conditions, providing versatility without requiring physical reconfiguration or multiple fixed assemblies
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 system provides accurate and cost-effective measurement of RF power parameters across a broad frequency and power range, reducing the need for multiple assemblies and achieving improved accuracy and directivity, while using less expensive components.
Implementation Method 1
The coils sense voltage variations related to forward- or reverse-traveling voltage waves on the transmission line
Implementation Method 2
a filter to compensate for reception of voltage signals through the coupler
Data Source
AI summary
An in-line directional radio-frequency (“RF”) power meter for measuring power and other parameters in a transmission line. The meter simultaneously measures complex voltage-waves traveling in the forward and reverse directions of a connected transmission line and processes measured voltages to compute forward and reverse power, standing wave ratio, and impedance values. The apparatus includes a microprocessor having microcode for digitally computing RF power parameters, and a field programmable gate array (“FPGA”) having microcode for executing complex Fast Fourier Transforms (“FFT”) to calculate voltages and frequencies, a microprocessor with attached firmware to make a series of complex calculations relative to sensed electrical values in the transmission line and to pass certain calculated values to the device to communicate RF power parameters to a user. The configuration of the apparatus allows for measurement of RF power parameters in a relatively economical package.