Polar TX RF Path Delay and IQ Phase Imbalance Calibration
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Solution Overview
Problem
Polar transmitter (Polar TX) systems with feedback receivers (FBR) face challenges in perfectly canceling phase modulation due to RF path delay and limited accuracy due to IQ phase imbalance, which are difficult to calibrate without external devices or complex hardware.
Innovation Solution
The method integrates on-chip RF path delay and IQ phase imbalance calibration using a FM_tune signal, allowing for simultaneous measurement and compensation without external devices, simplifying calculations and relaxing frequency limitations, applicable to both polar and IQ architectures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods are used for RF path delay and IQ phase imbalance, then calibration accuracy can be achieved, but external devices and complex hardware are required
Solution Approach 1:
The system uses its own internal resources (feedback receiver, existing RF paths, and signal processing capabilities) to perform calibration of RF path delay and IQ phase imbalance without requiring external calibration devices. The feedback receiver captures the transmitted signal and the system processes this feedback to extract calibration information, making the system self-calibrating.
Solution Approach 2:
The feedback receiver, originally designed for its primary function of capturing transmitted signals, is also utilized for calibration purposes. The same hardware components (mixers, ADCs, signal processing units) are used both for normal signal reception and for extracting calibration data, eliminating the need for separate dedicated calibration hardware.
2Measurement precision
If RF path delay calibration is performed using external devices, then accurate delay measurement can be achieved, but calibration time and system complexity increase
Solution Approach 1:
The system measures RF path delay using its own transmitted signal captured through the feedback receiver, eliminating the need for external delay measurement devices. The system generates a test signal, transmits it through the RF path, captures it via the feedback receiver, and calculates the delay based on the phase difference between transmitted and received signals.
Solution Approach 2:
The calibration process is integrated into the system initialization sequence, performing delay measurement and IQ phase imbalance calibration before normal operation begins. This preliminary calibration ensures accurate performance from the start without requiring separate calibration steps during operation.
3Measurement precision
If IQ phase imbalance calibration is performed with complex hardware, then calibration accuracy improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The system measures IQ phase imbalance using its own signal processing capabilities without requiring external calibration equipment. The feedback receiver captures the signal and the system calculates the phase difference between I and Q channels using standard signal processing algorithms, making the calibration process as simple as software configuration.
Solution Approach 2:
The patent replaces complex hardware-based calibration methods with software-based signal processing. Instead of using additional physical components or mechanical adjustment mechanisms, the system uses digital signal processing algorithms to measure and compensate for IQ phase imbalance, simplifying both manufacturing and calibration.
Data Source
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AI summary
A method of calibrating parameters for a polar transmitter (Polar TX) system includes receiving phase information derived from transmission information in a Polar TX for producing a radio frequency (RF) broadcast signal. An Inphase local oscillator (LO_I) signal and a quadrature phase local oscillator (LO_Q) signal are derived from a combination of a first signal and the phase information using a digital phase lock loop. A feedback receiver (FBR) receives the RF broadcast signal provided by the Polar TX. The LO_I signal and the LO_Q signal are mixed with the RF broadcast signal to obtain mixer output signals. RF path delay and IQ phase imbalance are concurrently determined as a function of the first signal and of the mixer output signals.