PLL Phase Difference Control Without RF Phase Shifter Loss
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Solution Overview
Problem
Existing radio frequency phase shifters for beamforming applications suffer from high loss and limited frequency band control, and analog-based technologies struggle to achieve precise phase shifting required for wireless power transmission.
Innovation Solution
A phase locked loop (PLL) circuit is modified by adding a phase adjustment current to the loop current, allowing precise phase shifting without the need for a separate RF phase shifter, enhancing resolution and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an analog phase shift circuit using a transmission line is used, then phase shifting function is provided, but loss increases and frequency band control is limited
Solution Approach 1:
The patent replaces the analog transmission line-based phase shift circuit with a digital phase shift circuit. The digital circuit uses a phase locked loop (PLL) with a digitally controlled oscillator (DCO) and phase adjustors to achieve phase shifting through digital control signals, eliminating the need for physical transmission line adjustments and reducing signal loss while enabling precise frequency band control.
Solution Approach 2:
The patent changes the control parameter from physical transmission line length to digital control signals. By using a DCO whose oscillation frequency is controlled by a digital control signal, and phase adjustors that receive digital control signals to adjust phase, the system achieves dynamic and precise phase shifting across different frequency bands without the limitations of fixed transmission line configurations.
2Measurement precision
If an analog phase shift circuit is used, then phase shifting is provided, but phase shifting precision is insufficient for wireless power transmission
Solution Approach 1:
The patent replaces the analog phase shift circuit with a digital phase shift circuit that uses a PLL architecture. The digital circuit incorporates a PFD for precise phase detection, a DCO for digitally controlled oscillation, and phase adjustors that receive digital control signals. This digital implementation provides superior phase shifting precision through fine-grained digital control while maintaining manageable circuit complexity through modular design.
Solution Approach 2:
The patent implements a feedback mechanism through the phase locked loop architecture. The PFD continuously compares the phase of the reference clock with the feedback clock from the DCO, generating error signals that are fed back to adjust the DCO's oscillation phase. This closed-loop feedback system ensures high phase shifting precision by automatically correcting any phase deviations, meeting the stringent requirements for wireless power transmission.
3Reliability
If a separate RF phase shifter is added, then phase shifting function is achieved, but device complexity and path loss increase
Solution Approach 1:
The patent merges the phase shifting function directly into the PLL circuit architecture itself, eliminating the need for a separate RF phase shifter. The phase locked loop integrates the reference clock input, frequency division, digital control, and phase adjustment functions in a unified structure. This integration reduces device complexity by removing redundant components while maintaining or improving beamforming accuracy through the precise digital phase control mechanisms within the PLL.
Solution Approach 2:
The patent designs the PLL circuit to perform multiple functions: frequency synthesis, phase shifting, and beamforming control. The same PLL architecture that generates the required output frequency also provides precise phase control through the DCO and phase adjustors. This multi-functional design eliminates the need for separate dedicated phase shifting components, reducing overall device complexity while achieving the required beamforming accuracy for reliable wireless power transmission.
Data Source
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AI summary
Internal phase shifting is achieved by adding a feedback divider to a feedback loop of a phase locked loop circuit configured to determine a transmission frequency of a wireless transmission terminal and adding a phase adjustment current to a loop current. Since the phase adjustment current is applied to an adder circuit, a phase difference is maintained even when the feedback loop is in a stable state, and accordingly, an output of the feedback divider maintains the phase difference with a reference frequency as intended by the phase adjustment current applied to the adder circuit.