Transmission Circuit Equalization for AM-AM and AM-PM Distortion
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Solution Overview
Problem
In mobile communication devices, the interaction between the power amplifier circuit and the RF front-end circuit leads to unwanted amplitude-amplitude (AM-AM) and amplitude-phase (AM-PM) errors across a wide modulation bandwidth, causing undesired amplitude distortion and spectrum regrowth in RF signals transmitted in millimeter wave spectrums.
Innovation Solution
The transmission circuit employs a power management integrated circuit (PMIC) with a phase correction circuit and a phase shifter to equalize the input vector using multiple complex filters, determining a reference phase correction voltage and scaling factor to generate a phase correction voltage, which is applied to the RF signal to correct AM-AM and AM-PM errors, thereby reducing instantaneous compression and spectrum regrowth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power amplifier circuit is coupled to the RF front-end circuit to amplify RF signals in millimeter wave spectrums, then the RF signal power is boosted to higher levels, but AM-AM and AM-PM errors are introduced causing amplitude distortion and spectrum regrowth
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction values for AM-AM and AM-PM errors in lookup tables before transmission. The baseband processor computes equalization factors based on known channel characteristics and power amplifier parameters, then applies these corrections to the input signal before it reaches the power amplifier, thereby preventing distortion rather than correcting it after the fact.
Solution Approach 2:
The patent implements feedback by using the known output characteristics of the power amplifier and RF front-end circuit to compute correction factors that are fed back to the baseband processor. The system continuously adjusts the equalization parameters based on the interaction between the power amplifier output reflection coefficient and the RF front-end circuit input reflection coefficient, creating a closed-loop correction mechanism.
2Productivity
If the power amplifier circuit is coupled to the RF front-end circuit, then signal transmission is enabled, but group delay interaction creates AM-AM and AM-PM errors across modulation bandwidth
Solution Approach 1:
The patent applies preliminary action by pre-computing phase correction values based on the known group delay characteristics of the RF front-end circuit and power amplifier. The system calculates equalization factors that compensate for phase errors before transmission, storing these corrections in lookup tables for rapid application during operation, thereby preventing phase distortion rather than correcting it after transmission.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the equalization parameters in the baseband processor based on the operating conditions. The system modifies the correction factors according to the modulation bandwidth, power level, and frequency to optimize phase error compensation across different transmission scenarios, transforming fixed correction values into adaptive parameters.
3Manufacturing precision
If complex filtering is applied to correct AM-AM and AM-PM errors across wide modulation bandwidth, then amplitude distortion and spectrum regrowth are reduced, but computational complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the correction process into separate, independent lookup tables for different frequency bands and modulation conditions. Instead of applying a single complex filter across the entire bandwidth, the system segments the modulation bandwidth into multiple segments, each with pre-computed correction factors, thereby reducing the real-time computational burden while maintaining correction effectiveness.
Solution Approach 2:
The patent implements copying by pre-computing and storing correction patterns in lookup tables that can be rapidly copied and applied during transmission. The baseband processor generates correction values offline or during idle periods, then copies these pre-computed values into memory for fast retrieval and application, replacing complex real-time calculations with simple memory access operations.
Data Source
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AI summary
Phase and amplitude error correction in a transmission circuit is provided. The transmission circuit includes a transceiver circuit, a power management integrated circuit (PMIC), and a power amplifier circuit(s). The transceiver circuit generates a radio frequency (RF) signal(s) from an input vector, the PMIC generates a modulated voltage, and the power amplifier circuit(s) amplifies the RF signal(s) based on the modulated voltage. When the power amplifier circuit(s) is coupled to an RF front-end circuit, unwanted amplitude-amplitude (AM-AM) and amplitude-phase (AM-PM) errors may be created across a modulation bandwidth of the transmission circuit. In this regard, in embodiments disclosed herein, the input vector is equalized based on multiple complex filters to thereby cause the AM-AM and AM-PM errors to be corrected in the transmission circuit. As a result, it is possible to reduce undesired instantaneous excessive compression and/or spectrum regrowth across the modulation bandwidth of the transmission circuit.