Wideband RF Transmission Circuit With ET Voltage Equalization
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Solution Overview
Problem
In mobile communication devices, the alignment of time-variant envelope tracking voltage with the RF signal's voltage envelope is often misaligned due to factors like group delay and impedance mismatch, leading to distortion and inefficiency in power amplifiers, especially in wide modulation bandwidths.
Innovation Solution
A wideband transmission circuit is designed with a transceiver circuit that applies an equalization filter to the time-variant input vector to compensate for the voltage distortion filter created at the output stage of the power amplifier, improving alignment and reducing unwanted compression and spectrum regrowth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the power amplifier circuit is coupled to the RF front-end circuit to amplify RF signals, then the signal transmission capability is improved, but voltage distortion is introduced due to interaction between output reflection coefficient and input reflection coefficient
Solution Approach 1:
The patent applies preliminary action by pre-compensating the input signal through equalization filtering before it enters the power amplifier circuit. The equalization filter is designed to anticipate and counteract the voltage distortion that will be introduced by the interaction between the power amplifier's output reflection coefficient and the RF front-end circuit's input reflection coefficient, thereby preventing distortion rather than correcting it afterward
Solution Approach 2:
The equalization filter serves as an intermediary element between the signal source and the power amplifier circuit. This intermediary component modifies the input signal characteristics to compensate for the anticipated distortion effects, acting as a mediator that prepares the signal to withstand the harmful interactions in the power amplifier stage
2Use of energy by moving object
If envelope tracking voltage is used to improve power amplifier efficiency, then energy efficiency is improved, but misalignment with voltage envelope occurs due to group delay and impedance mismatch
Solution Approach 1:
The patent implements feedback by continuously monitoring the actual voltage envelope of the RF signal and comparing it with the envelope tracking voltage. Based on this comparison, the system adjusts the envelope tracking voltage to maintain proper alignment, compensating for delays and mismatches that occur during operation
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the envelope tracking voltage parameters (amplitude, phase, timing) to maintain optimal alignment with the actual voltage envelope. This involves changing the electrical characteristics of the tracking voltage in real-time to compensate for group delay and impedance mismatch effects
3Productivity
If wide modulation bandwidth is used to increase data rate, then communication capacity is improved, but voltage distortion and misalignment worsen across the bandwidth
Solution Approach 1:
The patent applies segmentation by dividing the wide modulation bandwidth into multiple frequency segments or sub-bands. The equalization filter is designed to provide frequency-dependent compensation, treating each segment with appropriate filtering characteristics to address distortion specific to that frequency range, thereby managing wideband distortion more effectively than a single-stage approach
Data Source
AI summary
A wideband transmission circuit is provided. The wideband transmission circuit includes a transceiver circuit and a power amplifier circuit(s). The transceiver circuit generates a radio frequency (RF) signal(s) from a time-variant input vector and provides the RF signal(s) to the power amplifier circuit(s). The power amplifier circuit(s) amplifies the RF signal(s) based on a modulated voltage and provides the amplified RF signal(s) to a coupled RF front-end circuit (e.g., filter/multiplexer circuit). In embodiments disclosed herein, the transceiver circuit is configured to apply an equalization filter to the time-variant input vector to thereby compensate for a voltage distortion filter caused by a coupling of the power amplifier circuit(s) and the RF front-end circuit. As a result, it is possible to reduce undesired instantaneous excessive compression and/or spectrum regrowth resulting from the voltage distortion filter to thereby improve efficiency and linearity of the power amplifier circuit(s).