IP2 Calibration Using Duplexer Leakage and Binary Search
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Solution Overview
Problem
Conventional second-order intercept point (IP2) calibration in wireless receivers is inefficient due to the need for costly and time-consuming factory calibration processes, which often over-calibrate the receive circuit and are susceptible to finding local maxima during the calibration search, leading to extended calibration times and component failures.
Innovation Solution
The method involves transmitting a calibration signal through the duplexer to simulate real-world operation conditions, using a binary-like search to evaluate multiple points and reduce the likelihood of getting stuck in local maxima, and only calibrating to the point necessary for adequate reception performance, thereby accounting for duplexer non-ideal performance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional factory IP2 calibration is performed, then IP2 calibration is achieved, but calibration time and cost increase significantly
Solution Approach 1:
The system performs self-calibration by automatically generating calibration signals, measuring the received signal strength, and adjusting IP2 parameters without requiring external calibration equipment or manual intervention, thereby reducing calibration time and cost while maintaining accuracy
Solution Approach 2:
The calibration signal is transmitted through the normal transmit path and received through the normal receive path, allowing the same hardware components to serve both operational and calibration functions, eliminating the need for dedicated calibration equipment
2Measurement precision
If conventional factory IP2 calibration is performed, then IP2 calibration is achieved, but calibration cost increases
Solution Approach 1:
The transceiver performs self-calibration using its own transmit and receive circuits, eliminating the need for expensive external calibration equipment and reducing manufacturing costs while maintaining calibration accuracy
Solution Approach 2:
The calibration function is extracted from the normal operational signal flow by injecting calibration signals during idle periods or using unused frequency resources, allowing calibration to be performed without additional hardware
3Reliability
If conventional calibration methods are used, then calibration is performed, but the process is susceptible to finding local maxima leading to extended calibration times and component failures
Solution Approach 1:
The system measures the received calibration signal strength and uses this feedback to iteratively adjust IP2 parameters, ensuring the calibration converges to the global maximum rather than getting stuck in local maxima, thereby improving reliability
Solution Approach 2:
The calibration process dynamically adjusts the search strategy based on measured signal strength, transitioning from broad parameter sweeps to fine-tuned adjustments, which prevents getting trapped in local maxima and reduces calibration time
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 reduces calibration time and cost by efficiently determining IP2 calibration parameters, improving accuracy, and minimizing the number of component failures, while ensuring the calibration meets the necessary performance thresholds.
Implementation Method 1
a portion of the calibration signal leaks across the receive port of the duplexer and propagates over the receive circuit
Data Source
AI summary
IP2 calibration efficiency can be improved by passing the calibration signal through the transceiver's duplexer instead of inserting the calibration signal directly onto transceivers receive circuit. Passing the calibration signal through the duplexer may reduce IP2 calibration periods for transceivers having less-permeable duplexers, or duplexers that provide better than average separation between the RX and TX circuits. IP2 calibration inefficiencies can also be reduced by using a binary-like search when computing the in-phase and quadrature-phase path correction coefficients of the IP2 correction code.