Feedback Receiver Power Measurement for RF Output Calibration

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Solution Overview

Problem

Current radio communication systems face challenges in accurately measuring RF power output due to limitations in analog output power measurement methods, including precision issues related to temperature and frequency variations, and the need for extensive factory calibration, which increases costs and time.

Innovation Solution

Implementing a digital measurement method using a digital signal processing unit, transmitter, and feedback receiver to control attenuation and calculate output power values based on digital input and feedback signals, with calibration factors adjusted for temperature and gain variations, reducing the need for additional circuitry and simplifying factory calibration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If analog RMS power detector IC devices are used to measure output power, then the measurement can be performed with simple and low-cost circuitry, but the measurement precision deteriorates due to temperature and frequency variations

Engineering Contradiction:

Improvecircuitry complexityVSAvoidoutput power measurement precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent changes the measurement parameter from direct analog voltage measurement to digital signal processing of baseband signals. By converting the RF signal to baseband through mixing and low-pass filtering, then measuring the digital signal levels, the system achieves temperature and frequency compensation without requiring complex analog calibration circuits.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If analog RMS power detector IC devices are used, then the device complexity is reduced, but the factory calibration time and cost increase due to the need for precise coefficient determination

Engineering Contradiction:

Improvedetector circuit complexityVSAvoidfactory calibration time

Core Design Contradiction:

Device complexityVSLoss of time

Solution Approach 1:

The patent replaces the mechanical/analog calibration process with a digital computation approach. Instead of determining complex response characteristic coefficients through analog measurements during factory calibration, the system uses digital signal processing to compute power from baseband signal samples, eliminating the need for time-consuming analog calibration procedures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If digital measurement methods with down-conversion and analog to digital conversion are used, then the measurement precision is improved by reducing temperature and frequency variation effects, but the device complexity and cost increase due to additional circuitry

Engineering Contradiction:

Improveoutput power measurement precisionVSAvoidcircuitry complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the baseband processing circuitry serve multiple functions: it enables both the digital power measurement method and the existing feedback receiver functionality. By reusing the same mixing, low-pass filtering, and digital processing circuits for both purposes, the system achieves precise digital power measurement without adding dedicated measurement circuitry.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent enables the feedback receiver's baseband processing circuits to serve the power measurement function independently. The digital signal processing unit that already exists for feedback purposes is utilized to compute power measurements, allowing the system to self-measure power without external measurement equipment or additional dedicated circuits.

Inventive Principle:

Principle #25Self-service

4Device complexity

If existing digital feedback receivers are reused for power measurement, then the device complexity is reduced, but the measurement precision deteriorates due to the difficulty of mapping RF gains to baseband power readings

Engineering Contradiction:

Improvemeasurement system complexityVSAvoidpower measurement precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent extracts the power measurement function from the RF domain and places it in the baseband domain. By measuring the power of the baseband I and Q signals directly after low-pass filtering, the system avoids the complex RF-to-baseband gain mapping problem. The power computation is performed on the already-converted baseband signals where the relationship between signal level and power is direct and linear.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8705595B2Digital output power measurement in radio communication systems

Publication Date: 2014.04.22 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Devices and methods related to devices capable to perform digital output power measurement besides attenuation control are provided. A device includes a digital signal processing unit, a transmitter and a feedback receiver. The digital signal processing unit is configured to control attenuation along a transmission path and a feedback path based on a comparison of a power of a digital input signal with a raw power of a corresponding digital feedback signal, and to calculate an output power value of an analog RF signal to be broadcasted, using the raw power of the digital feedback signal and one or more feedback gain factors related to gain in the feedback receiver.