DTC Predistortion Calibration for Harmonic Spur Reduction
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Solution Overview
Problem
Wireless communication devices face challenges with non-linearities in transceiver systems, particularly in digital-to-time converters (DTCs), which can lead to increased energy in unwanted harmonics and violate regulatory requirements, necessitating power reduction.
Innovation Solution
A DTC calibration circuit is employed to separately capture and compensate for the non-linearity of rising and falling edges in DTCs using loop-back receiver circuits, allowing for pre-distortion of DTC codes to reduce unwanted spurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If DTC is used for phase modulation in transceiver systems, then signal processing flexibility is improved, but non-linearities increase causing unwanted harmonics
Solution Approach 1:
The patent applies preliminary action by measuring the DTC non-linearity characteristics beforehand and storing correction values in lookup tables. During operation, pre-distorted DTC codes are generated by combining original codes with correction codes from the lookup tables, compensating for non-linearities before they affect the output signal. This prevents unwanted harmonics while maintaining signal processing flexibility.
2Object-generated harmful factors
If transmitter power is reduced to meet regulatory requirements, then unwanted harmonic energy is decreased, but communication efficiency is worsened
Solution Approach 1:
The patent changes the parameter of DTC codes by applying pre-distortion correction values to modify the timing signals. This transforms the DTC output characteristics to compensate for non-linearities, allowing the transmitter to maintain full power while meeting spectral emission requirements. The correction codes adjust the DTC timing parameters to cancel out non-linear distortion effects.
3Manufacturing precision
If separate calibration for rising and falling edges is implemented, then non-linearity compensation precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the DTC calibration process into separate rising edge and falling edge measurements. The loop-back receiver independently captures non-linearity characteristics for each edge type, and separate lookup tables are generated for rising and falling edges. This segmentation enables precise compensation for each edge's specific non-linearities without requiring complex real-time processing during operation.
Data Source
AI summary
A method for compensating signal nonlinearities includes generating a local oscillator (LO) signal and performing phase modulation of the LO signal to generate a phase-modulated LO signal. The phase modulation is based on applying at least one digital-to-time converter (DTC) code of a plurality of DTC codes to a rising edge signal portion and a falling edge signal portion associated with the LO signal. Nonlinearities associated with the rising edge signal portion and the falling edge signal portion are determined. The at least one DTC code is adjusted based on the nonlinearities.