Differential RF Power Detection With Common-Mode Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Differential power measurements in transmitters and receivers are often inaccurate due to the common mode portion of differential signals, which induces errors and prevents the determination of true differential power.
Innovation Solution
A power detector circuit with a common mode rejection mechanism, utilizing capacitors and transistors to separate the differential and common mode paths, effectively rejecting the common mode portion of a differential signal and allowing for accurate measurement of differential power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a power detector measures the power of a differential signal, then the power measurement function is achieved, but the common mode portion of the signal induces errors and reduces measurement precision
Solution Approach 1:
The power detector is divided into separate differential mode detection path and common mode detection path. The differential mode path measures the desired differential power signal, while the common mode path specifically detects the common mode interference. By segmenting the detection functions, the circuit can process and reject common mode errors while maintaining accurate differential power measurement.
Solution Approach 2:
The common mode detection path provides feedback about the common mode interference level to the differential mode detection path. This feedback mechanism allows the circuit to dynamically compensate for common mode errors by adjusting the differential power measurement based on the detected common mode signal level, thereby improving measurement precision.
2Measurement precision
If a common mode rejection circuit is added to reject the common mode portion, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The common mode rejection functionality is merged with the existing differential power detection circuit by sharing transistors and signal paths. The same transistors used for differential detection also participate in common mode rejection through appropriate biasing and configuration, eliminating the need for completely separate common mode rejection circuitry and thus reducing overall device complexity.
Solution Approach 2:
The power detector circuit is designed with multi-functional components that serve both differential power detection and common mode rejection functions. The transistors and signal paths are configured to perform multiple functions simultaneously, making the circuit more versatile and reducing the total component count while maintaining high measurement precision.
Data Source
AI summary
A power detector circuit that rejects the common mode portion of a differential signal is disclosed. The circuit includes a differential input having first and second input nodes. Differential and common mode circuit paths are coupled to the differential input. The common mode circuit path includes first and second capacitors coupled to respective first terminals of first and second input nodes of the differential input. The second terminal of each of the first and second capacitors is coupled to a gate terminal of a first bias transistor. The common mode circuit path is configured to reject a common mode portion of a differential input signal provided to the differential input such that a differential output signal is indicative of an amount of power of a differential portion of the differential input signal.