Two-Point Phase Modulator Calibration for Wideband PLL Modulation
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Solution Overview
Problem
Phase modulators using phase-locked loops (PLL) are limited by bandwidth, restricting data rate, and existing two-point phase modulators lack effective calibration methods for conversion gain.
Innovation Solution
A two-point phase modulator with a PLL circuit that forms a loop during activation, detects phase differences, stores voltage, and generates an output frequency signal, while a conversion gain calibration unit calculates the conversion gain value during deactivation, ensuring wide bandwidth without distortion by adjusting digital-to-analog conversion gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a phase modulator uses a PLL circuit to adjust division ratio, then frequency conversion capability is improved, but data rate is limited by PLL bandwidth
Solution Approach 1:
The patent segments the modulation function into two independent paths: a digital path using sigma-delta modulator for coarse frequency adjustment, and an analog path using direct voltage application for fine frequency adjustment. This segmentation allows each path to operate optimally within its bandwidth constraints, achieving both wide bandwidth and high data rate simultaneously.
Solution Approach 2:
The patent transitions from a single-dimension digital control approach to a two-dimensional control system combining digital (sigma-delta) and analog (direct voltage) modulation paths. This dimensional expansion enables the system to overcome the bandwidth limitation of purely digital PLL control while maintaining frequency conversion capability.
2Device complexity
If conversion gain is not calibrated, then device complexity is reduced, but output signal distortion increases
Solution Approach 1:
The patent implements a self-calibration mechanism where the system automatically measures its own conversion gain by applying a test voltage and measuring the resulting frequency change. This self-service approach eliminates the need for external calibration equipment or complex manual adjustment mechanisms, achieving high precision without proportionally increasing device complexity.
Solution Approach 2:
The patent employs feedback control in the calibration process by measuring the actual frequency output, comparing it with the expected frequency based on applied voltage, and using this feedback to calculate and adjust the conversion gain value. This feedback mechanism ensures accurate calibration while maintaining relatively simple circuit implementation.
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
Enables increased data rate and accurate calibration of conversion gain, ensuring wide bandwidth and minimizing distortion in the output frequency signal.
Implementation Method 1
A phase frequency detector detects differences in phase and frequency between the reference frequency signal and the divided output frequency signal
Implementation Method 2
A charge pump pumps charge based on an output signal of the phase frequency detector and outputs a pumping voltage
Implementation Method 3
A loop filter changes the voltage based on the pumping voltage applied through the switch and stores the changed voltage
Implementation Method 4
A voltage-controlled oscillator generates the output frequency signal based on an output signal of the second adder
Data Source
AI summary
A two-point phase modulator and a method of calibrating conversion gain of the same are provided. The two-point phase modulator locks an output frequency signal by charging and pumping charge in a phase-locked loop (PLL) circuit at the beginning of operation, opens a loop of the PLL circuit for a period of time, and applies a step signal, thus calibrating conversion gain of a modulation signal that controls the output frequency signal. Thus, the conversion gain may be accurately calibrated by the calibration operation at one time.