RF Power Amplifier Sensing Circuit for Compact Power Measurement
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Solution Overview
Problem
Conventional RF power amplifier couplers are large, costly, and frequency-dependent, making them inefficient for measuring power delivered to a load in RF PA circuits, especially in compact applications like cellular telephones, due to substantial electrical coupling length and losses.
Innovation Solution
A compact sensing circuit using a multiplier circuit to sense differential voltage and current directly at the load, providing an analog output proportional to the power delivered, which can control the gain of the RF PA to maintain constant output power under varying conditions, utilizing lumped elements and integrated circuit technology to minimize size and loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional coupler is used to measure power delivered to the load, then power measurement capability is achieved, but the device size and circuit board surface area become substantially large
Solution Approach 1:
The patent extracts the power measurement function from the conventional coupler structure and implements it using separate sensing circuits (voltage sensing circuit 220 and current sensing circuit 230) that can be integrated directly at the load. This separation allows the measurement function to be decoupled from the large coupler structure, enabling compact implementation while maintaining measurement capability.
Solution Approach 2:
The patent nests the voltage sensing circuit and current sensing circuit directly at the load, integrating multiple measurement functions within a compact structure. The sensing circuits are positioned to measure voltage across and current through the load simultaneously, creating a nested configuration that minimizes circuit board surface area while achieving accurate power measurement through the relationship P=VI.
2Measurement precision
If a conventional coupler with substantial electrical coupling length is used, then power measurement is achieved, but electrical losses become substantial
Solution Approach 1:
The patent removes the long electrical coupling path inherent in conventional couplers by extracting the measurement function and implementing it through direct sensing circuits at the load. The voltage sensing circuit 220 and current sensing circuit 230 measure parameters directly at the load without requiring substantial electrical coupling length, thereby minimizing electrical losses while maintaining measurement accuracy.
3Loss of energy
If a conventional coupler is designed to minimize electrical coupling length, then losses are reduced, but frequency dependency increases
Solution Approach 1:
The patent implements a universal measurement approach where the sensing circuits (voltage sensing circuit 220 and current sensing circuit 230) can accurately measure power across a broad frequency range. By using general-purpose sensing circuits rather than frequency-optimized couplers, the system achieves frequency independence and can adapt to varying operating conditions without being constrained by electrical coupling length optimizations for specific frequency bands.
4Measurement precision
If a conventional coupler is used, then power measurement is achieved, but the device complexity and difficulty of design increase
Solution Approach 1:
The patent segments the power measurement function into distinct voltage sensing circuit 220 and current sensing circuit 230, each performing a specific measurement task. This segmentation simplifies the overall design by breaking down the complex coupler structure into manageable, independent sensing modules that can be designed and implemented separately, reducing overall device complexity while maintaining measurement capability.
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 solution achieves accurate power measurement with reduced size and loss, maintaining constant output power under varying loads and temperatures, and is less dependent on frequency, thus improving performance and compliance with emission requirements.
Implementation Method 1
a sensing circuit coupled to the input node and the output node to sense a differential voltage between the input and output nodes and to sense a detected voltage at the input node
Implementation Method 2
a multiplier circuit to receive the differential voltage and to receive the detected voltage, the multiplier circuit to provide an output voltage proportional to an instantaneous power delivered to the load based on the differential voltage, the detected voltage, and the impedance of the first element of the first circuit
Data Source
AI summary
Apparatus, system, and method including a circuit including an element having an electrical impedance, an input node to receive a signal, and an output node to couple to a load; a sensing circuit coupled to the input node and the output node to sense a differential voltage between the input and output nodes and to sense a detected voltage at the input node; and a multiplier circuit to receive the differential voltage and to receive the detected voltage. The multiplier circuit provides an output voltage proportional to the instantaneous power delivered to the load based on the differential voltage, the detected voltage, and the impedance of the element. A system may further include a radio frequency (RF) power amplifier (PA). A method may further include controlling a gain of the RF PA to maintain the power delivered to the load at a predetermined level based on the output voltage of the multiplier circuit.