Single-Bit Envelope Tracking for Wideband MIMO RF Integrity
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Solution Overview
Problem
Conventional envelope tracking systems face challenges in maintaining RF signal integrity and power efficiency, particularly in MIMO systems, due to differences in propagation lengths and frequency responses between spatially separated power amplifiers, leading to signal distortions and limited bandwidth.
Innovation Solution
An envelope tracking system that uses a single-bit digital signal to encode an analog envelope tracking control signal, allowing for higher bandwidth support up to 300 MHz, by measuring the amplitude of the RF signal and converting it into a low-voltage differential signaling format for transmission to an envelope tracker, which adjusts the power amplifier supply voltage accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional envelope tracking systems use analog control signals for power amplifier supply voltage adjustment, then power efficiency can be improved, but bandwidth is limited and signal integrity deteriorates due to propagation differences in MIMO systems
Solution Approach 1:
The patent replaces the analog control signal system with a digital control signal system. Specifically, the envelope tracking control signal is converted to a digital format (e.g., I2C, SPI, or other digital protocols) to control the power amplifier supply voltage. This substitution eliminates the signal integrity issues caused by analog signal propagation differences in MIMO systems while maintaining the power efficiency benefits of envelope tracking.
Solution Approach 2:
The patent changes the parameter of the control signal from analog to digital domain. By converting the envelope tracking control signal to digital form, the system maintains power efficiency control while achieving immunity to propagation length and frequency response variations that affect analog signals in spatially separated power amplifier configurations.
2Productivity
If spatially separated power amplifiers are used in MIMO systems, then transmission capacity is improved, but signal distortion occurs due to differences in propagation lengths and frequency responses
Solution Approach 1:
The patent substitutes digital control signals for analog control signals in the envelope tracking system. This allows spatially separated power amplifiers to be controlled independently without suffering from signal propagation differences, as digital signals are immune to such analog degradation effects while still enabling the MIMO configuration for improved transmission capacity.
3Power
If analog envelope tracking control signals are used, then power amplifier supply voltage can be adjusted for power efficiency, but bandwidth is limited and signal degradation occurs
Solution Approach 1:
The patent replaces the analog control signal transmission system with a digital control signal system. This substitution enables higher bandwidth operation (e.g., supporting wideband signals like LTE and Wi-Fi) while maintaining the ability to adjust power amplifier supply voltage for power efficiency, as digital signals can be transmitted at higher frequencies without the degradation issues affecting analog signals.
Data Source
AI summary
Embodiments described herein relate to an envelope tracking system that uses a single-bit digital signal to encode an analog envelope tracking control signal, or envelope tracking signal for brevity. In certain embodiments, the envelope tracking system can estimate or measure the amplitude of the baseband signal. The envelope tracking system can further estimate the amplitude of the envelope of the RF signal. The system can convert the amplitude of the envelope signal to a single-bit digital signal, typically at a higher, oversample rate. The single-bit digital signal can be transmitted in, for example, a low-voltage differential signaling (LVDS) format, from a transceiver to an envelope tracker. An analog-to-digital converter (ADC or A/D) can convert the single-bit digital signal back to an analog envelope signal. Moreover, a driver can increase the power of the A/D output envelope signal to produce an envelope-tracking supply voltage for a power amplifier.