Wireless Terminal IIP2 Calibration via Envelope Detector Feedback
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Solution Overview
Problem
Current wireless communication terminals face challenges in calibrating the Second Order Input Intercept Point (IIP2) effectively, leading to reception sensitivity deterioration due to the complexity of hardware and the inability to use Surface Acoustic Wave filters across all frequency bands, resulting in increased InterModulation Distortion 2 (IMD2) and Noise Figure (NF) issues.
Innovation Solution
A method and apparatus for efficiently calibrating IIP2 by using a modem to apply a one-tone signal of 1 MHz to the transmission chain, calibrating DC offset voltage and I/Q signals, and adjusting the signal input to the reception chain via an envelope detector and switch, minimizing hardware modifications and external equipment requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a SAW filter is used to suppress transmission output leakage signal and interference signal, then reception sensitivity is improved, but hardware complexity increases and the filter cannot be used in all frequency bands
Solution Approach 1:
The patent extracts the harmful IMD2 component generated by transmission leakage through calibration processes that measure and compensate for second-order distortion products, eliminating the need for physical SAW filters in certain frequency bands while maintaining reception sensitivity
Solution Approach 2:
The patent changes the operating parameters of the receiver by applying calibration signals at specific frequencies and power levels to measure and compensate for IIP2 variations, allowing the system to maintain high reception sensitivity without requiring hardware filters across all frequency bands
2Device complexity
If no filter other than duplexer is used to simplify hardware, then device complexity is reduced, but IMD2 of transmission leakage signal increases and reception sensitivity deteriorates
Solution Approach 1:
The patent implements a feedback-based calibration system where the receiver measures its own IIP2 characteristics using internally generated calibration signals, and uses this feedback to compensate for IMD2 distortion through digital signal processing, maintaining high reception sensitivity without additional hardware filters
Solution Approach 2:
The terminal performs self-calibration of its IIP2 characteristics using its own transmission and reception chains, eliminating the need for external calibration equipment or additional filter hardware while maintaining optimal reception performance across different frequency bands
3Device complexity
If IIP2 is not calibrated properly, then calibration process is simplified, but reception sensitivity deteriorates due to increased IMD2
Solution Approach 1:
The patent performs IIP2 calibration during the manufacturing process using a simplified test setup, pre-determining calibration parameters that are stored in the terminal for use during operation, thereby eliminating the need for complex real-time calibration procedures while ensuring high reception sensitivity
Solution Approach 2:
The patent uses a simplified calibration model that copies or approximates the actual IIP2 behavior through lookup tables or pre-characterized parameters, allowing accurate compensation for IMD2 without requiring complex real-time measurement and calculation systems
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 allows for precise IIP2 calibration, reducing IMD2 distortion and improving reception sensitivity without the need for additional hardware or software, enabling efficient operation across multiple frequency bands.
Implementation Method 1
a connector configured to connect an output of the transmission chain and an output of the reception chain via an envelope detector
Data Source
AI summary
A method and apparatus for calibrating a terminal is provided. The apparatus includes a modem; a transmission chain configured to process a signal input from the modem and transmit the processed signal via an antenna; a reception chain configured to process a signal received via the antenna and transmit the processed signal to the modem; and a connector configured to connect an output of the transmission chain and an output of the reception chain via an envelope detector and a switch configured to turn on/off the envelope detector, calibrate a DC offset voltage and I and Q signals of the transmission chain by inputting a one-tone signal of 1 MHz into the transmission channel via the modem in a state where the envelope detector is turned on, and calibrate a second order input intercept point (IIP2) characteristic value by adjusting the signal input into the modem via the reception channel.