RF Power Detection Using Phase Shifting and Harmonic Filtering
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Solution Overview
Problem
Existing systems for detecting output power in mobile terminals are not tolerant to variations in load impedance and are susceptible to harmonics, often requiring additional components like directional couplers that increase manufacturing costs and decrease efficiency.
Innovation Solution
A system that uses a quadrature splitter and combiner to generate phase-shifted detection signals from in-phase and quadrature-phase amplifier legs, allowing for the cancellation of forward and reverse components and the removal of harmonics, thereby detecting forward and reverse power without a directional coupler.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a directional coupler is used to detect output power, then power detection accuracy is improved, but manufacturing cost increases and transmission efficiency decreases
Solution Approach 1:
The patent extracts the power detection function from the main transmission path by using a small portion of the transmitted signal through a coupling mechanism. The coupling capacitor C1 couples a small portion of the transmitted signal to the detection circuit while the main signal continues through the antenna, separating the detection function from the primary transmission path and avoiding the need for a directional coupler
Solution Approach 2:
The patent introduces an intermediary detection circuit consisting of capacitor C1, diode D1, and resistor R1 that mediates between the transmitted signal and the detection function. This intermediary circuit extracts power information without requiring a directional coupler, thereby reducing device complexity while maintaining detection accuracy
2Measurement precision
If a directional coupler is used to detect output power, then power detection accuracy is improved, but transmission efficiency decreases
Solution Approach 1:
The coupling capacitor C1 extracts only a small portion of the transmitted signal for detection purposes, allowing the main signal to pass through to the antenna with minimal loss. This extraction approach maintains transmission efficiency while enabling accurate power detection
Solution Approach 2:
The intermediary detection circuit with capacitor C1, diode D1, and resistor R1 provides a high-impedance path that minimally loads the transmission path. This intermediary mechanism enables power detection without significantly impacting transmission efficiency
3Stability of the object's composition
If traditional power detection approaches are used to eliminate load impedance variations, then output power stability is improved, but susceptibility to harmonics increases
Solution Approach 1:
The patent converts the harmful effect of harmonics into a beneficial filtering mechanism. The detection circuit uses the natural frequency response of the RC circuit (C1, R1) and diode D1 to filter out harmonic frequencies while passing the fundamental frequency, thereby converting harmonic susceptibility into a frequency-selective detection advantage
Solution Approach 2:
The patent changes the detection parameter from direct voltage measurement to rectified and filtered voltage measurement. The diode D1 rectifies the AC signal and the RC circuit (C1, R1) filters the rectified signal, changing the detection parameter to be more stable against load impedance variations while inherently rejecting harmonics
4Device complexity
If open loop power amplifiers are used, then device complexity is reduced, but output power variations due to load impedance increase
Solution Approach 1:
The patent implements a feedback mechanism where the detection circuit monitors the actual transmitted power and provides this information to the control system. The controller adjusts the power amplifier input based on the detected power level, creating a closed-loop system that maintains stable output power despite load impedance variations
Solution Approach 2:
The detection circuit using capacitor C1, diode D1, and resistor R1 provides self-service by automatically detecting and reporting the transmitted power level without requiring external intervention. This self-measuring capability enables the control system to maintain power stability while keeping the overall device complexity low
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
This approach effectively detects output power while being tolerant to load impedance variations and harmonics, reducing manufacturing costs and maintaining efficiency by eliminating the need for a directional coupler and improving signal clarity.
Implementation Method 1
The phase shifter shifts the phase of at least one of the first and second detection signals such that the forward components of the first and second detection signals are essentially in-phase, and the reverse components of the first and second detection signals are essentially 180 degrees out-of-phase
Implementation Method 2
The combiner combines the phase-shifted detection signals to provide a signal indicative of forward power
Implementation Method 3
The filter removes harmonics of the combined signal to provide a signal indicative of forward power
Implementation Method 4
The in-phase amplifier leg amplifies the in-phase RF input signal to provide an amplified in-phase signal, and the quadrature-phase amplifier leg amplifies the quadrature-phase RF input signal to provide an amplified quadrature-phase signal
Data Source
AI summary
A system for detecting both forward and reverse power of a power amplifier in the presence of harmonics created by the power amplifier is provided. A forward power detection system receives detection signals from an in-phase amplifier leg and a quadrature-phase amplifier leg of the power amplifier. The forward power detection system applies a phase shift to the detection signals such that forward components of the detection signals are essentially in-phase, and reverse components of the detection signals are essentially 180 degrees out-of-phase. The phase shifted detection signals are then combined and filtered to provide a signal indicative of forward power. In a similar fashion, a reverse power detection system applies a phase shift to the detection signals to provide a signal indicative of reverse power.