Transmitter PLL Dynamic Bandwidth for Frequency Pulling Control
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Solution Overview
Problem
Current EDGE transmitters face modulation distortion due to RF oscillator pulling and supply-ground coupling of extraneous noise, leading to increased hardware complexity and power consumption when trying to mitigate frequency pulling effects.
Innovation Solution
The implementation of an All-Digital Phase-Locked Loop (ADPLL) with dynamic bandwidth adjustment, where the loop bandwidth is only increased when significant frequency pulling occurs, minimizing the duration of bandwidth widening to reduce noise-induced oscillator pulling and maintain low area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the loop bandwidth is increased to mitigate frequency pulling effects, then the modulation distortion is reduced, but the power consumption and hardware complexity increase
Solution Approach 1:
The patent implements dynamic bandwidth adjustment where the loop bandwidth of the ADPLL is not fixed but is adjusted in real-time based on the actual frequency pulling conditions. The bandwidth is increased only when significant frequency pulling occurs and reduced when conditions improve, optimizing the balance between modulation accuracy and power consumption.
Solution Approach 2:
The patent changes the loop bandwidth parameter dynamically rather than maintaining a constant high bandwidth. This parameter adjustment allows the system to achieve adequate frequency pulling mitigation only when necessary, thereby reducing average power consumption while maintaining acceptable modulation accuracy.
2Reliability
If the loop bandwidth is increased to reduce frequency pulling effects, then the error vector magnitude performance improves, but the spectral mask and phase noise deteriorate
Solution Approach 1:
The patent employs dynamic bandwidth adjustment where the loop bandwidth is temporarily increased only during periods of significant frequency pulling. This dynamic approach prevents continuous bandwidth widening, thereby avoiding the degradation of spectral mask and phase noise that would result from maintaining a permanently wide bandwidth configuration.
Solution Approach 2:
The patent implements periodic monitoring of frequency pulling conditions and adjusts the loop bandwidth accordingly. The bandwidth is widened only during specific periods when frequency pulling exceeds thresholds and is reduced during normal operation, achieving EVM improvement without continuous spectral mask degradation.
3Stability of the object's composition
If the loop bandwidth is continuously widened to counteract oscillator pulling, then the frequency stability improves, but the area and power consumption increase
Solution Approach 1:
The patent implements a dynamically adjustable loop bandwidth that responds to actual frequency pulling conditions. Rather than continuously widening the bandwidth which would require oversized hardware components, the system adjusts bandwidth only when frequency stability is compromised, allowing for more compact and power-efficient circuit design.
Solution Approach 2:
The patent changes the loop bandwidth parameter based on operating conditions rather than designing for worst-case continuous wide bandwidth. This allows the use of smaller, less power-consuming hardware components that can achieve adequate frequency stability through intelligent parameter adjustment rather than brute-force bandwidth widening.
Data Source
AI summary
An embodiment of the present invention provides transmitter having a phase locked loop that has a dynamically controllable loop bandwidth. A transmit modulator is coupled to the PLL for performing vector modulation in response to transmission symbols. Each transmission symbol comprises an amplitude signal and a phase signal. A controller is coupled to the PLL and to the transmit modulator and is operable to detect when a criteria of the transmission symbols crosses a threshold and to adjust loop bandwidth in response to crossing the threshold. The criteria of the transmission symbols may be a function of the amplitude signal or a function of the phase signal, and may be the amplitude signal, a first derivative of the amplitude signal, a second derivative of the amplitude signal, a square of the amplitude signal, a derivative of the amplitude signal squared, the phase signal, or a derivative of the phase signal.