Quadrature PLL Phase Control Using Injection Current Feedback
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Solution Overview
Problem
Existing quadrature phase lock loop (PLL) circuits face challenges in maintaining phase balance over a wide frequency range, especially at millimeter wave frequencies, due to frequency dependence and lack of robust closed-loop control mechanisms.
Innovation Solution
The implementation of two identical PLL circuits referenced to the same clock, with a phase detector and an adjustable current source to apply an injection current, creating a phase difference and adjusting it in real-time to maintain a 90-degree phase shift between I and Q signals, thereby achieving phase-balanced quadrature local oscillator signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a passive or active phase shifter or 90-degree power divider is used to split LO signal into I and Q signals, then phase balance can be achieved at a specific frequency, but the circuit becomes frequency dependent and cannot maintain exact phase balance over a wide frequency range
Solution Approach 1:
The patent uses two coupled VCOs where the phase relationship is dynamically maintained through coupling rather than being fixed by frequency-dependent passive components. The VCOs can operate across a wide frequency range while maintaining quadrature relationship through their coupled oscillation mechanism.
Solution Approach 2:
The patent implements a closed-loop feedback system using phase detectors that continuously monitor the phase difference between I and Q signals and provide feedback to adjust the coupling, ensuring exact 90-degree phase balance is maintained across the frequency range.
2Adaptability or versatility
If coupled VCOs are used to generate quadrature signals, then a wide frequency range can be covered, but phase balance suffers when amplitudes are out of balance due to mismatches between VCOs
Solution Approach 1:
The patent employs phase detectors that continuously monitor the phase difference between the coupled VCO outputs and provide feedback signals to adjust the coupling mechanism, ensuring that phase balance is maintained even when amplitude mismatches occur between the VCOs.
Solution Approach 2:
The coupled VCO system automatically adjusts its operating parameters through the feedback mechanism to maintain quadrature relationship, with the system self-correcting for amplitude mismatches without external intervention.
3Ease of manufacture
If master and slave latches are used to generate I and Q signals, then implementation at high frequencies becomes difficult, and the approach is not a closed-loop scheme
Solution Approach 1:
The patent implements a closed-loop feedback system using phase detectors that continuously monitor the phase relationship between I and Q signals and provide feedback to maintain exact quadrature, eliminating the open-loop limitations of latch-based approaches.
Solution Approach 2:
The patent replaces the mechanical/latch-based signal generation approach with an electronic coupled VCO system that uses electromagnetic coupling and feedback control, enabling reliable operation at millimeter wave frequencies where latch circuits become impractical.
Data Source
AI summary
A method includes phase-shifting an output signal of a phase lock loop (PLL) circuit by applying an injection current to an output of a charge pump of a the PLL circuit. A circuit includes: a first phase lock loop (PLL) circuit and a second PLL circuit referenced to a same clock; a phase detector circuit that detects a phase difference between an output signal of the first PLL circuit and an output signal of the second PLL circuit; and an adjustable current source that applies an injection current to at least one of the first PLL circuit and the second PLL circuit based on an output of the phase detector circuit.