RF Load Power Detection Using Passive Network Voltage Sampling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
RF power amplifiers in wireless applications typically measure forward power, which does not equate to the real power consumed by the load, limiting the ability to accurately control amplifier output and ensuring safe maximum power delivery to the antenna.
Innovation Solution
A method and apparatus that measure real power delivered to the load by using voltages from both sides of a passive network and a phase-delayed voltage, determining the voltage difference and multiplying it with the phase-shifted voltage to calculate the real power consumed, which is then filtered to provide accurate power consumption data for adjusting the power amplifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If forward power is measured using a directional coupler, then the amplifier output can be controlled, but the measurement does not accurately reflect the real power consumed by the load
Solution Approach 1:
The patent introduces a measurement intermediary (the passive network with voltage sampling points) between the power amplifier and load to capture voltage information that can be used to calculate real power. This intermediary enables accurate power measurement without requiring direct access to the load or complex measurement equipment at the load location.
Solution Approach 2:
The patent replaces the traditional directional coupler measurement system with an electrical calculation system. Instead of using electromagnetic coupling to measure power, the system uses voltage sampling and mathematical computation (P = V²/R or P = VI cosφ) to determine real power, substituting a simpler electrical measurement approach for the more complex electromagnetic measurement system.
2Power
If impedance transformation network is added to increase power output, then the power amplifier can deliver higher power, but the measurement of real power at the load becomes more difficult
Solution Approach 1:
The patent performs preliminary measurement action by sampling the voltage at the input side of the passive network, before the impedance transformation occurs. This preliminary voltage measurement, combined with knowledge of the transformation ratio, allows calculation of the real power at the load without requiring direct measurement at the load side, thus simplifying the measurement process despite the presence of impedance transformation.
Solution Approach 2:
The patent changes the measurement parameter from direct power measurement at the load to voltage measurement at the amplifier output, which can then be mathematically transformed to obtain load power. This parameter change exploits the known relationship between the voltages at different points in the impedance transformation network to simplify measurement.
Data Source
AI summary
Real power delivered to a load in an RF transmit path is measured. Measuring the real power includes supplying a first voltage from a first side of a passive network disposed between the power amplifier and the load, supplying a second voltage from a second side of the passive network; and using the first and second voltages and a phase delayed voltage to determine the real power delivered to the load. A voltage difference between the first and second voltages is determined and multiplied by the phase shifted voltage. A low pass filter is then applied to the output of the multiplier to provide an indication of the real power consumed by the load. The indication of real power consumed may then be used to control the power amplifier.