VCO Delay Matching for Magnetic Coupling Pulling Reduction
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Solution Overview
Problem
Voltage-controlled oscillators (VCOs) in transmitter circuits experience frequency pulling due to magnetic coupling with power amplifiers, which existing methods struggle to fully mitigate, especially in scenarios where frequency separation or additional modulator circuits are impractical.
Innovation Solution
The implementation of a coupling delay matching (CDM) system that introduces additional signal delays to phase-shift the feedback signal by an integer multiple of the VCO period, reducing frequency pulling by aligning or offsetting the phase of the VCO and power amplifier signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If frequency separation between VCO and power amplifier is increased to reduce magnetic coupling, then frequency pulling is reduced, but device complexity and circuit design difficulty increase
Solution Approach 1:
The patent changes the phase parameter of the feedback signal by introducing a controllable delay element. By adjusting the delay amount to match the oscillation period of the VCO, the feedback signal's phase is shifted by an integer multiple of the period, transforming the harmful magnetic coupling effect into a beneficial or neutral effect without requiring frequency separation.
Solution Approach 2:
The patent introduces a delay element as an intermediary component between the power amplifier and the VCO. This intermediary component manipulates the phase of the feedback signal, allowing the system to maintain close frequency operation while eliminating frequency pulling through phase alignment.
2Object-affected harmful factors
If additional modulator circuits are added to separate frequencies, then magnetic coupling is reduced, but device complexity increases
Solution Approach 1:
Instead of adding modulator circuits to change frequency, the patent changes the phase parameter of the existing feedback signal through a delay element. This parameter change achieves the same goal of reducing magnetic coupling without the complexity of additional modulation circuits.
Solution Approach 2:
The patent extracts and addresses only the phase component of the feedback signal by removing the harmful phase relationship through delay adjustment. This selective approach eliminates frequency pulling without requiring complete frequency separation through modulators.
3Power
If VCO and power amplifier operate at the same frequency, then magnetic coupling reinforces oscillation, but frequency pulling still occurs due to phase differences
Solution Approach 1:
The patent uses feedback control by monitoring the phase relationship between the VCO output and the power amplifier feedback signal. A delay element is introduced to adjust the feedback signal's phase, ensuring it aligns with the VCO oscillation phase, thereby reinforcing oscillation while eliminating frequency pulling.
Solution Approach 2:
The patent changes the phase parameter of the feedback signal by adjusting the delay element's delay amount to match the VCO oscillation period. This parameter adjustment ensures the feedback signal constructively reinforces the VCO oscillation without causing frequency pulling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces frequency pulling by phase-shifting the feedback signal, minimizing the impact of magnetic coupling on the VCO, thereby enhancing the stability of the transmitter system without requiring significant frequency separation or additional modulator circuits.
Implementation Method 1
Relatively high currents passing through the inductor(s) of the power amplifier can tend to magnetically couple back to the inductor(s) of the VCO
Implementation Method 2
introduces additional signal delays to phase-shift the feedback signal by an integer multiple of the VCO period
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Techniques are described for reducing frequency pulling in voltage-controlled oscillator (VCO) circuits. Some embodiments operate in context of a transmitter having a VCO and a power amplifier (PA), where resonant components of the VCO are impacted by magnetically coupled feedback from resonant components of the PA. The VCO and PA are coupled via a set of signal path components that cause signal path delay, such that the feedback signal is phase-delayed with respect to the signal generated by the VCO. A coupling delay matching system is used to introduce additional delay, thereby further phase-shifting the feedback signal to an integer multiple of the oscillation period of the VCO signal; thereby reducing frequency pulling of the VCO.