Transmission Circuit Input Equalization for AM-AM and AM-PM Error Correction
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Solution Overview
Problem
Existing transmission circuits in mobile communication devices experience amplitude-amplitude (AM-AM) and amplitude-phase (AM-PM) errors due to interactions between the power amplifier circuit and RF front-end circuit, leading to undesired amplitude distortion and spectrum regrowth, particularly in wide modulation bandwidths.
Innovation Solution
The transmission circuit employs a phase correction circuit and power management integrated circuit (PMIC) to equalize the input vector using multiple complex filters, applying phase shifts and scaling factors 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 amplifies RF signals in millimeter wave spectrums, then the RF signal power is boosted to higher levels, but amplitude-amplitude (AM-AM) and amplitude-phase (AM-PM) errors are introduced due to interactions with the RF front-end circuit
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 phase correction circuit retrieves these pre-computed values based on the modulated voltage level and applies them to compensate for distortions that would otherwise occur during power amplification, thereby maintaining signal accuracy while achieving high power output.
Solution Approach 2:
The patent implements feedback through the phase correction circuit that continuously monitors the modulated voltage level and dynamically adjusts the phase shift applied to the RF signal. By feeding back the voltage level information and using it to select appropriate correction values from lookup tables, the system compensates for amplitude distortions in real-time, resolving the contradiction between high power amplification and amplitude precision.
2Adaptability or versatility
If the power amplifier circuit is coupled to the RF front-end circuit, then the transmission circuit achieves complete functionality, but group delay interactions create AM-AM and AM-PM errors across the modulation bandwidth
Solution Approach 1:
The patent introduces an intermediary phase correction circuit between the power amplifier and the modulation detection path. This intermediary component receives the modulated voltage level, retrieves correction values from lookup tables, and applies phase shifts to compensate for AM-PM errors. By placing this intermediary correction mechanism in the signal path, the system maintains full transmission functionality while correcting reliability-degrading errors caused by the necessary coupling between power amplifier and RF front-end circuits.
3Productivity
If the RF signal is modulated across a wide modulation bandwidth (≥200 MHz), then the data rate is increased, but instantaneous excessive compression and spectrum regrowth occur due to AM-AM and AM-PM errors
Solution Approach 1:
The patent applies preliminary action by pre-calculating correction values for the entire modulation bandwidth before transmission occurs. Lookup tables are populated with phase and amplitude correction values corresponding to different voltage levels and frequency offsets, enabling the phase correction circuit to quickly compensate for wideband distortion effects without real-time computation delays, thus maintaining high data rates while preventing spectrum regrowth.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the phase shift parameter based on the modulated voltage level and frequency offset. The phase correction circuit modifies the phase parameter in response to changing signal conditions, and the lookup tables store correction values that account for frequency-dependent AM-AM and AM-PM errors across the wide modulation bandwidth, thereby preventing spectral distortion while maintaining high productivity.
Data Source
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.