PLL Variable Capacitance Circuit With MOS Bias Network
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Solution Overview
Problem
Existing variable capacitance components in electronics, such as phase locked loops, face challenges with high costs, manufacturing variability, limited operating bandwidth, and sensitivity to temperature, process, and voltage variations, particularly in digital phase locked loop circuits that rely on multiple fixed-value capacitors.
Innovation Solution
A variable capacitance circuit using Metal Oxide Semiconductor (MOS) transistors or other semiconductor devices to switch capacitors in and out, configured in a parallel network with offset bias voltages, allowing for a wide voltage range and reduced sensitivity to temperature, process, and voltage variances, by maintaining constant charge pump current pulse magnitude and low pass filter resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital phase locked loop circuits use multiple fixed-value capacitors to adjust capacitance, then capacitance adjustment is achieved, but design time, surface area, and component count increase
Solution Approach 1:
The patent uses a single capacitor with variable capacitance controlled by voltage applied to a varactor diode, replacing multiple fixed-value capacitors. This changes the parameter control method from discrete component switching to continuous voltage control, achieving capacitance adjustment without increasing component count
Solution Approach 2:
The varactor diode serves multiple functions: it provides continuous capacitance adjustment, eliminates the need for multiple fixed capacitors, and integrates control within a single component. This multi-functional approach reduces overall circuit complexity while maintaining adaptability
2Adaptability or versatility
If digital phase locked loop circuits use multiple fixed-value capacitors to adjust capacitance, then capacitance adjustment is achieved, but manufacturing cost and surface area increase
Solution Approach 1:
By using voltage to control the capacitance of a single varactor diode rather than manufacturing and assembling multiple fixed-value capacitors, the solution reduces manufacturing complexity and cost while maintaining capacitance adjustment capability
Solution Approach 2:
The patent combines the functions of multiple fixed-value capacitors into a single variable capacitor component (varactor diode), reducing the number of discrete components that need to be manufactured, assembled, and tested, thereby lowering manufacturing cost and surface area
3Adaptability or versatility
If digital phase locked loop circuits use multiple fixed-value capacitors to adjust capacitance, then capacitance adjustment is achieved, but noise increases and accuracy decreases
Solution Approach 1:
The varactor diode enables smooth, continuous capacitance adjustment through voltage control, eliminating the discrete steps and associated noise from switching between fixed-value capacitors. This provides more precise and accurate capacitance control
Solution Approach 2:
The voltage-controlled varactor diode provides continuous capacitance adjustment without interruption or switching noise, maintaining smooth operation and higher precision compared to discrete capacitor switching methods
4Adaptability or versatility
If existing variable capacitance components are used, then capacitance control is achieved, but operating bandwidth is limited
Solution Approach 1:
The patent uses voltage-controlled capacitance in a varactor diode, which can respond rapidly to voltage changes and operate over a wide frequency range. This enables broader operating bandwidth compared to traditional variable capacitance components
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 solution provides a cost-effective, accurate, and noise-immune variable capacitance over a large voltage range, reducing design complexity and component count while maintaining performance across manufacturing variations.
Implementation Method 1
A variable capacitance circuit may operate a Metal Oxide Semiconductor (MOS) transistor or other semiconductor device to switch a capacitor in and out
Implementation Method 2
Several circuits may be combined in a parallel network having offset bias voltages, such that the combined network may produce a variable capacitance over a large voltage range
Data Source
AI summary
A variable capacitance circuit may operate a Metal Oxide Semiconductor (MOS) transistor or other semiconductor device to switch a capacitor in and out. Several circuits may be combined in a parallel network having offset bias voltages, such that the combined network may produce a variable capacitance over a large voltage range. The variable capacitance circuit may be incorporated into a phase locked loop (PLL) circuit where similar devices may be configured to produce a voltage reference as part of the PLL circuitry. Such a circuit may be immune to temperature, process, or voltage variances, since the current pulse magnitude times the low pass filter resistance times the sensitivity of a controlled voltage oscillator can be held constant.