Phase Detector Assembly With 90° Shifted Reference Alignment
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Solution Overview
Problem
Low-noise phase detectors in phase-locked loops for high-frequency oscillators can only detect phase differences and have limited dynamic range, requiring a transient process and asymmetrical modulation when switching from a digital phase detector, leading to inefficiencies and noise.
Innovation Solution
Phase-shifting the reference signal by 90° for one phase detector and keeping it in-phase for the other, eliminating the need for a DC offset voltage and avoiding transient processes and asymmetry in the dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low-noise phase detector (mixer or XOR) is used, then noise is reduced, but the dynamic range is limited to 180° and a transient process is required after switching from a digital phase detector
Solution Approach 1:
The invention applies preliminary action by pre-shifting the reference signal by 90° before it enters the low-noise phase detector. This preliminary phase shift aligns the characteristic curves of both the digital and low-noise phase detectors, eliminating the need for a transient settling process when switching between detectors. The 90° shifted signal is combined with the in-phase signal through a summing network, creating a composite signal that maintains symmetry and prevents the characteristic mismatch that would otherwise require settling time.
2Productivity
If a DC offset voltage is added to avoid transient process, then switching between phase detectors is smoothed, but the modulation range becomes asymmetrical
Solution Approach 1:
The invention deliberately introduces asymmetry in the signal paths through the summing network, where one input receives the in-phase reference signal and the other receives the 90° phase-shifted reference signal. This controlled asymmetry in signal routing creates a symmetrical composite characteristic curve at the output, eliminating the need for DC offset compensation and maintaining equal modulation range in both directions. The asymmetry in input signaling produces symmetry in the overall detector characteristic.
3Adaptability or versatility
If a combined phase detector arrangement is used, then both phase and frequency detection capabilities are achieved, but the characteristic curve zero points differ between detectors
Solution Approach 1:
The invention changes the phase parameter of the reference signal by introducing a 90° phase shift in one path while keeping the other path at 0°. This parameter change in the reference signal phase aligns the zero points of both phase detectors' characteristic curves. The summing network then combines these signals with different phase parameters to produce a composite output where both detectors operate with consistent reference points, enabling seamless switching without transient processes.
Data Source
Figure 1~3
AI summary
The detector assembly has a low-noise phase detector (1) e.g. mixer, including a characteristic zero point with 90 degrees, and a digital phase detector (2) in which an output signal of a high frequency oscillator is compared with a reference signal. One of the output and reference signals is phase-shifted around 90 degrees by a 90 degree power splitter (4) and is supplied to the phase detectors, where the other signal is supplied to the phase detectors in phase.