Transceiver Equalization Filter Calibration for Envelope Tracking
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Solution Overview
Problem
In mobile communication devices, the alignment of time-variant envelope tracking voltage with the RF signal voltage is often misaligned due to factors like group delay and impedance mismatch, leading to unwanted distortion and inefficiency in power amplifiers, especially across wide modulation bandwidths.
Innovation Solution
A calibration circuit is implemented in the transceiver circuit to generate gain and delay lookup tables, allowing the equalization filter to dynamically adapt and compensate for voltage distortion, thereby reducing excessive compression and spectrum regrowth across the modulation bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If power amplifiers amplify RF signals in millimeter wave spectrums to higher power, then transmission capability is improved, but distortion and interference increase
Solution Approach 1:
The patent applies preliminary anti-action by using an equalization filter to pre-compensate for distortion and interference before the RF signals are amplified by power amplifiers. The equalization filter is configured to counteract the harmful effects that will occur during amplification, thereby maintaining signal quality even at higher power levels in millimeter wave spectrums.
2Use of energy by moving object
If envelope tracking voltage is used to improve power amplifier efficiency, then energy efficiency is improved, but voltage misalignment causes performance degradation
Solution Approach 1:
The patent implements feedback by continuously monitoring the alignment between envelope tracking voltage and RF signal voltage, and using this information to adjust the equalization filter settings. The system measures the actual voltage alignment and feeds this information back to optimize the equalization parameters, ensuring maintained voltage alignment accuracy across varying operating conditions and frequencies.
Solution Approach 2:
The patent applies dynamics by making the equalization filter adaptive and configurable across different frequencies within the modulation bandwidth. The equalization filter parameters are dynamically adjusted based on the operating frequency to maintain optimal voltage alignment, transforming a static system into one that adapts to changing conditions.
3Reliability
If equalization filter is applied to compensate voltage distortion, then signal quality is improved, but filter calibration complexity increases
Solution Approach 1:
The patent applies parameter changes by calibrating the equalization filter across multiple frequencies within the modulation bandwidth to determine optimal filter parameters for each frequency. The system measures voltage distortion characteristics at different frequencies and adjusts the equalization filter parameters accordingly, storing these calibrated parameters for use during operation. This approach maintains signal quality across the entire bandwidth while managing calibration complexity through systematic parameter optimization.
Data Source
AI summary
Equalization filter calibration in a wideband transmission circuit is provided. The transceiver circuit generates a radio frequency (RF) signal(s) from a time-variant modulation vector and a power amplifier circuit(s) amplifies the RF signal(s) based on a modulated voltage. The transceiver circuit is configured to apply an equalization filter to the time-variant modulation vector to thereby compensate for a voltage distortion filter created at the output stage of the power amplifier circuit(s). In embodiments disclosed herein, a calibration circuit can be configured to calibrate the equalization filter across multiple frequencies within a modulation bandwidth of the power amplifier circuit to generate a gain offset lookup table (LUT) and a delay LUT. As a result, the equalization filter can be dynamically adapted to reduce undesired instantaneous excessive compression and/or spectrum regrowth resulting from the voltage distortion filter across the modulation bandwidth of the power amplifier circuit.