Dual-Path Phase-Locked Loop for Low-Noise Beamforming
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Solution Overview
Problem
Phase locked loops (PLLs) in wireless systems face stringent phase noise requirements due to closer sub-carrier spacing in 5G millimeter wave systems, necessitating accurate phase shifts for beamforming, while also needing programmable frequency and low phase noise without excessive power consumption.
Innovation Solution
A phase locked loop arrangement that adjusts the phase of an oscillator signal by comparing a reference signal with feedback signals to generate a control signal, using a loop filter, controllable oscillator, frequency divider, and comparator paths to improve phase control accuracy and reduce hardware area, with a method involving a common reference signal, first and second feedback signals, and current signals to adjust the phase of the oscillator signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single feedback signal path is used in the PLL, then the circuit complexity is low, but the phase control accuracy is insufficient to meet stringent 5G millimeter wave requirements
Solution Approach 1:
The feedback signal path is segmented into multiple parallel paths (first feedback signal path and second feedback signal path), each with its own comparator. This segmentation allows independent optimization of each path while achieving higher overall phase control accuracy through combined operation, resolving the contradiction between accuracy and complexity.
Solution Approach 2:
The invention transitions from a single-dimensional feedback path to a multi-dimensional architecture by adding parallel feedback paths with different delay characteristics. This dimensional expansion enables the system to capture phase information from multiple angles, improving accuracy without proportionally increasing complexity.
2Reliability
If multiple feedback signal paths are added to improve phase control accuracy, then the phase noise performance improves, but the hardware area increases
Solution Approach 1:
Multiple feedback paths are merged into a unified PLL architecture that shares common components such as the loop filter, controllable oscillator, and reference signal source. This merging approach allows the system to achieve improved phase noise performance through multiple comparison paths while minimizing the increase in hardware area by reusing shared resources.
Solution Approach 2:
The common reference signal source and loop filter serve multiple feedback paths simultaneously, providing multi-functionality. This universal design enables the PLL to achieve superior phase noise performance through multiple paths without proportionally increasing hardware area, as each component serves multiple purposes.
3Manufacturing precision
If the phase shifts are imposed on the oscillator signal for beamforming, then the beamforming accuracy is improved, but the phase noise requirements become more stringent
Solution Approach 1:
The PLL performs preliminary phase correction and stabilization before the signal is used for beamforming. By pre-adjusting the oscillator signal phase and reducing phase noise in advance, the system achieves accurate beamforming without requiring the oscillator to meet excessively stringent phase noise requirements, thus resolving the contradiction.
Solution Approach 2:
The multiple feedback paths continuously monitor and correct phase deviations in the oscillator signal before it is applied to beamforming. This real-time feedback mechanism ensures that phase shifts imposed on the oscillator signal maintain high beamforming accuracy while the feedback loops actively suppress phase noise, resolving the contradiction between the two requirements.
4Adaptability or versatility
If programmable frequency control is implemented to enable operation on different frequency channels, then the system versatility is improved, but the device complexity increases
Solution Approach 1:
The PLL incorporates dynamically adjustable parameters including programmable frequency division ratios and adjustable phase shifts. These dynamic control capabilities enable the system to operate on different frequency channels and adapt to various beamforming requirements without requiring multiple fixed-frequency circuits, thus achieving versatility without proportionally increasing complexity.
Solution Approach 2:
The system achieves frequency channel adaptability by changing key parameters such as the frequency division ratio and phase shift values rather than redesigning the entire circuit for each frequency. This parameter-based approach allows programmable frequency control across different channels while maintaining relatively simple control circuitry, resolving the contradiction between versatility and complexity.
Data Source
AI summary
A phase locked loop, particularly for or in a beamforming system comprises a loop filter (1) to provide a control signal (FC) to a controllable oscillator (2); a frequency divider (3) configured to provide a first feedback signal (FB) and a second feedback signal (FBD) in response to an oscillator signal (FO), the second feedback signal (FBD) delayed with respect to the first feedback signal (FB); a first comparator path (4) configured to receive the first feedback signal (FB) and a second comparator path (5) configured to receive the second feedback signal (FBD), each of the first and second comparator path (4, 5) configured to provide a respective current signal (CS1, CS2) to the loop filter (1) in response to a respective adjustment signal (FA1, FA2) and a phase deviation between a common reference signal (FR) and the respective feedback signal (FB, FBD).