PLL Frequency Modulator With Capacitive Divider for Fast Frequency Shifts
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Solution Overview
Problem
Existing frequency modulators with closed phase locked loops face limitations in modulation bandwidth due to high implementation complexity and energy consumption, particularly in achieving rapid and precise frequency changes and handling higher-rate modulation signals.
Innovation Solution
A frequency modulator design featuring a closed phase locked loop with a capacitive voltage divider and a modulation unit that allows for rapid transition of control voltages by adding or removing current at the center tap, reducing transient processes and enabling faster, more precise frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a digital preemphasis filter and automatic calibration unit are used to achieve precise matching of transfer functions, then modulation bandwidth is improved, but device complexity and energy consumption increase significantly
Solution Approach 1:
The patent extracts the essential function of rapid frequency modulation by directly varying the frequency divider ratio in response to modulation signals, removing the complex preemphasis filter and calibration unit while maintaining effective modulation bandwidth through the inherent responsiveness of the frequency divider mechanism
Solution Approach 2:
Instead of using complex filtering and calibration to achieve precise transfer function matching, the patent inverts the approach by directly controlling the frequency divider ratio to achieve the desired frequency modulation effect, simplifying the system while maintaining performance
2Speed
If a digital preemphasis filter and automatic calibration unit are used to achieve precise matching of transfer functions, then modulation bandwidth is improved, but energy consumption increases
Solution Approach 1:
The patent removes the energy-consuming preemphasis filter and calibration unit, retaining only the essential frequency divider and phase-locked loop components needed for effective frequency modulation, thereby significantly reducing power consumption while maintaining modulation bandwidth
Solution Approach 2:
The patent employs simple, low-power digital logic elements for frequency division and control rather than complex analog filtering and calibration circuits, achieving adequate performance with minimal energy expenditure
3Ease of operation
If the divisor of the frequency divider is varied as a function of the modulation signal, then frequency modulation is achieved, but the frequency change per unit time is relatively small
Solution Approach 1:
The patent implements dynamic control of the frequency divider ratio through direct digital manipulation of the division factor in response to modulation signals, enabling rapid frequency transitions by quickly updating the divider ratio without being limited by analog filter response times
Solution Approach 2:
The patent replaces analog filtering and calibration mechanisms with digital logic and control, allowing for instantaneous updates of the frequency divider ratio and achieving faster frequency change rates through digital switching rather than analog transition
4Adaptability or versatility
If additional components such as filters and analog-to-digital converters are added, then modulation functionality is improved, but device complexity and energy consumption increase
Solution Approach 1:
The patent achieves versatile frequency modulation functionality using a universal phase-locked loop structure with a programmable frequency divider that can accommodate different modulation schemes and frequency ranges without requiring additional specialized components like filters or multiple converters
Solution Approach 2:
The patent implements sufficient frequency modulation capability through direct frequency divider control without adding excessive filtering or calibration stages, achieving adequate performance for communication applications while maintaining simplicity
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
This design simplifies implementation, reduces energy consumption, and allows for rapid and precise frequency changes, enabling higher-rate modulation signals and improved performance in transmitting/receiving devices.
Implementation Method 1
a modulation unit that is designed to provide, at a first output, values of a divisor that are a function of the modulation signal, and at a second output, a second control voltage that is a function of the modulation signal
Data Source
AI summary
A frequency modulator is provided for generating an output signal with a frequency that is a function of a modulation signal, wherein the modulation signal can assume N≧2 different discrete modulation values, and a predetermined frequency value of the output signal is associated with each modulation value, containing: a) a closed phase locked loop with a loop filter for providing a first control voltage, with a voltage controlled oscillator for generating the output signal, and with a switchable frequency divider for deriving a frequency-divided signal, and b) a modulation unit that is designed to provide, at a first output, values of a divisor that are a function of the modulation signal, and at a second output, a second control voltage that is a function of the modulation signal, c) wherein the oscillator has a first control input connected to the loop filter and has a second control input connected to the second output of the modulation unit, and is designed to generate the output signal as a function of the first control voltage and the second control voltage, d) and wherein the frequency divider is connected to the first output of the modulation unit and is designed to derive the frequency-divided signal in such a manner that it has instantaneous frequencies that are a function of the divisor values. According to the invention, the modulation unit has a capacitive voltage divider with a center tap and is designed to provide the second control voltage at the center tap. The invention further concerns a transmitting/receiving device and an integrated circuit having such a frequency modulator.