PLL Charge Pump Circuit With Resistor-Based Flicker Noise Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional charge pump circuits generate high flicker noise due to the use of active transistors, which significantly impact the signal-to-noise ratio, especially in narrow bandwidth scenarios.
Innovation Solution
A charge pump circuit is designed with first and second current source circuits using variable resistor open-loop gain modules and transistors, along with a switching circuit to control charging and discharging, minimizing flicker noise by generating currents through resistors instead of active devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active transistors are used to generate charge pump currents, then the charge pump can function properly, but high flicker noise is generated
Solution Approach 1:
The patent replaces the active transistor-based current generation mechanism with a passive resistor-based current generation mechanism. Specifically, current mirrors are replaced with resistors that generate charge pump currents through voltage-to-current conversion, eliminating the flicker noise inherently generated by active transistor operation while maintaining the charge pump's functional capability
Solution Approach 2:
The patent changes the fundamental parameter of current generation from active device operation to passive resistive voltage division. By using resistors with specific resistance values and reference voltages, the system generates stable currents without the noise characteristics of active transistors, fundamentally altering how charge pump currents are produced
2Reliability
If narrow bandwidth is used in phase-locked loop, then frequency stability is improved, but flicker noise significantly impacts signal-to-noise ratio
Solution Approach 1:
The patent substitutes the noisy active transistor current sources with passive resistor-based current generation in the charge pump. This substitution removes the primary noise source that degrades signal-to-noise ratio in narrow bandwidth PLL applications, allowing the system to maintain both frequency stability and high signal-to-noise ratio performance
3Device complexity
If conventional current mirrors are used, then current generation is simple, but flicker noise is high
Solution Approach 1:
The patent replaces complex active transistor current mirror circuits with simpler passive resistor-based current generation circuits. The resistor-based approach using voltage-to-current conversion is both structurally simpler and noise-free, eliminating the need for matched transistor pairs and complex biasing networks while achieving the same current generation function without flicker noise
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
The proposed solution effectively suppresses flicker noise, stabilizing current generation and improving the signal-to-noise ratio in phase-locked loops, particularly suitable for wireless communication applications.
Implementation Method 1
the first operational amplifier is connected to the first transistor... the first variable resistor open-loop gain module being connected to the first transistor in such a way that a voltage at an input terminal of the first transistor is consistent with a first reference voltage
Implementation Method 2
charge pump currents are typically produced by active current sources, such as current mirrors... However, due to the use of active transistors for producing charge pump currents, generation of high flicker noise is inevitable
Data Source
AI summary
The present disclosure provides a charge pump, a phase-locked loop circuit and a transceiver. The charge pump comprises: a first current source circuit comprising a first transistor and a first variable resistor open-loop gain module for causing a voltage at an input terminal of the first transistor to be consistent with a first reference voltage; a second current source circuit comprising a second transistor and a second variable resistor open-loop gain module for causing a voltage at an output terminal of the second transistor to be consistent with a second reference voltage; and a switching circuit coupled to the first and second current source circuits and the loop filter, and configured to control charging of the loop filter in response to an output signal from a phase frequency detector. The charge pump, the phase-locked loop circuit and the transceiver can suppress the flicker noise for the charge pump.