Single-Bit Envelope Tracking for High-Bandwidth RF Supply Control
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Solution Overview
Problem
Conventional envelope tracking systems in wireless devices face challenges in maintaining RF signal integrity and power efficiency, particularly due to spatial separation of power amplifiers and limited bandwidth, which results in signal distortions and reduced battery life.
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 determining the amplitude of the RF input signal and converting it into a low-voltage differential signaling format for transmission to an envelope tracker, which modifies the power amplifier supply voltage accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional analog envelope tracking control signals are used, then the system is simpler to implement, but the bandwidth is limited and signal integrity deteriorates at higher frequencies
Solution Approach 1:
The patent replaces the conventional analog control signal with a digital single-bit encoded signal. This substitution transforms the continuous analog domain into a discrete digital domain, enabling higher bandwidth operation up to 300 MHz while maintaining signal integrity. The digital encoding approach eliminates the bandwidth limitations inherent in analog systems.
Solution Approach 2:
The patent changes the fundamental parameter of the control signal from analog voltage level to digital bit sequence. By encoding the envelope tracking control signal as a single-bit digital signal that varies in frequency or timing rather than amplitude, the system achieves extended bandwidth capability while the envelope tracker converts this digital signal back to the appropriate voltage levels for power amplifier control.
2Reliability
If power amplifier supply voltage is maintained at high levels, then RF signal transmission is ensured, but power consumption increases and battery life decreases
Solution Approach 1:
The patent implements dynamic supply voltage adjustment for the power amplifier by using envelope tracking. The single-bit digital control signal enables the envelope tracker to dynamically modulate the power amplifier's supply voltage in real-time based on the instantaneous RF signal envelope. This allows the power amplifier to operate at lower voltages during low-signal conditions while maintaining high voltage during peak transmission, significantly reducing average power consumption while ensuring reliable communication when needed.
3Ease of operation
If spatial separation between power amplifiers and control circuits is increased, then device layout flexibility improves, but signal distortion increases due to limited bandwidth
Solution Approach 1:
The patent replaces the analog control signal transmission with a digital single-bit encoded signal. This substitution allows the control signal to be transmitted over longer distances and through more complex routing without degradation, as digital signals are more robust to interference and attenuation. The single-bit encoding maintains signal fidelity even when spatial separation between the power amplifiers and control circuits is increased, enabling greater layout flexibility in device design.
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.