Tunable Polyphase Filter Feedback for Wideband Quadrature Clocks
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Solution Overview
Problem
Conventional methods for generating quadrature phase clock signals, such as polyphase filters, frequency dividers, and quadrature voltage controlled oscillators, face limitations in generating accurate signals for multiple frequencies due to issues with frequency characteristics, layout area, and power consumption.
Innovation Solution
A tunable polyphase filter and phase detector system that generates four quadrature phase clock signals and adjusts the filter's resistance and capacitance values based on detected phase differences to achieve accurate quadrature phase clock signals for multiple input frequencies, forming a feedback loop to ensure precise phase calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional polyphase filter is used to generate quadrature phase clock signals, then the layout area is reduced, but the frequency characteristics deteriorate because it can generate quadrature phase only at a single frequency
Solution Approach 1:
The polyphase filter is made tunable by incorporating variable capacitance elements that can be adjusted based on the input clock frequency. This dynamic adjustment allows the filter to maintain accurate quadrature phase generation across multiple frequencies while retaining the area advantages of the polyphase filter structure.
Solution Approach 2:
The capacitance values in the polyphase filter are made variable rather than fixed. By changing the capacitance parameters according to the input frequency, the filter achieves accurate quadrature phase output for multiple frequencies. The phase detector monitors phase accuracy and provides feedback to adjust the capacitance values accordingly.
2Measurement precision
If a frequency divider is used to generate quadrature phase clock signals, then the frequency characteristics are improved, but the applicability to high speed applications is limited
Solution Approach 1:
The conventional frequency divider approach is replaced with a polyphase filter-based system. The polyphase filter directly generates quadrature phase signals through its filtering characteristics rather than dividing frequencies, enabling high-speed operation while maintaining accurate frequency characteristics through the variable capacitance tuning mechanism.
3Measurement precision
If a quadrature voltage controlled oscillator is used to generate quadrature phase clock signals, then the frequency characteristics are improved, but the layout area and power consumption increase
Solution Approach 1:
The VCO component is extracted and removed from the system. Instead of using a QVCO with two VCOs, the patent uses a polyphase filter driven by a single VCO (or other clock source), achieving quadrature phase generation through the filter's phase-shifting properties rather than through multiple oscillators, thereby reducing area and power consumption.
4Measurement precision
If a quadrature voltage controlled oscillator is used to generate quadrature phase clock signals, then the frequency characteristics are improved, but the power consumption increases
Solution Approach 1:
The second VCO is extracted and removed from the system. The patent achieves quadrature phase generation using a single VCO feeding into a polyphase filter, eliminating the need for two independent VCOs and their associated power consumption, while maintaining accurate frequency characteristics through the tunable filter.
Data Source
AI summary
A quadrature phase clock generator includes a tunable polyphase filter and a phase detector. The tunable polyphase filter is configured to receive an input clock signal and generate four quadrature phase clock signals. The phase detector is coupled to receive at least two of the four quadrature phase clock signals and generate a control signal adapted to tune the polyphase filter based on the received quadrature phase clock signals. Further, the phase detector is configured to provide the control signal to the polyphase filter in a feedback loop. Based on the control signal from the phase detector, the tunable polyphase filter generates four tuned quadrature phase clock signals as output phase clock signals.