Frequency Modulator Using Integrated Signals for High Data Rates
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Solution Overview
Problem
Existing frequency modulators face limitations in data rate due to transient processes during switch operation, have low frequency stability, and lack flexibility in frequency shifts, with complex and inefficient direct digital synthesis and IQ modulators also being inefficient and prone to parasitic oscillations.
Innovation Solution
A low-power frequency modulator that integrates the modulation signal and carrier signal, forming a differential signal which is then phase-modulated to achieve frequency modulation, eliminating the need for frequency-modulating the crystal oscillator and allowing for flexible frequency shifts and baseband filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a switch is used to change the series capacitance of the crystal oscillator for frequency modulation, then the frequency can be modulated, but the data rate is limited due to transient processes during switch operation
Solution Approach 1:
The patent replaces the mechanical/electronic switch-based frequency modulation mechanism with a direct digital synthesis (DDS) approach. Instead of physically switching capacitors to change crystal oscillator frequency, the invention uses digital signal processing to generate frequency-modulated signals, thereby eliminating transient processes associated with physical switching and enabling much higher data rates.
Solution Approach 2:
The invention changes the fundamental parameter control method from analog (switching capacitance values) to digital (adjusting phase increment words and frequency tuning words). By modifying the digital control parameters in the DDS system, frequency modulation is achieved without the transient delays inherent in analog switching mechanisms.
2Adaptability or versatility
If the oscillation frequency of the crystal oscillator is made variable for frequency modulation, then frequency modulation is achieved, but the frequency stability becomes low
Solution Approach 1:
The patent segments the frequency modulation function from the crystal oscillator itself. The crystal oscillator maintains its stable base frequency, while a separate DDS module handles frequency modulation by generating phase-corrected signals. This segmentation allows the oscillator to remain stable while the overall system achieves frequency variability through digital processing.
Solution Approach 2:
The invention introduces a phase-locked loop (PLL) and DDS system as intermediaries between the stable crystal oscillator and the final frequency-modulated output. The PLL locks onto the oscillator's stable frequency, while the DDS module generates the frequency-modulated signal based on digital control words, thus mediating between stability and variability requirements.
3Adaptability or versatility
If direct digital synthesis is used for frequency modulation, then frequency flexibility is improved, but the system complexity increases and efficiency decreases
Solution Approach 1:
The patent implements a universal DDS core that can generate various frequency-modulated signals by simply changing digital control parameters. The same hardware structure (phase accumulator, phase-to-amplitude converter, DAC) serves multiple modulation functions, reducing overall system complexity compared to dedicated circuits for each modulation type while maintaining high frequency flexibility.
4Adaptability or versatility
If IQ modulators are used in the transmission path for frequency modulation, then frequency modulation capability is achieved, but the device complexity increases and efficiency decreases
Solution Approach 1:
The invention extracts and eliminates the unnecessary I and Q signal generation and combination stages from the modulation path. By using direct phase modulation through the DDS system, the patent removes the complex IQ modulator architecture while retaining the essential frequency modulation capability, thereby simplifying the device structure and improving efficiency.
Data Source
AI summary
A frequency modulation method is provided in which the frequency of a carrier signal is modulated on the basis of the frequency of a modulation signal, and in which the modulation signal is integrated. The carrier signal is integrated, and a differential signal is formed from the integrated modulation signal and the integrated carrier signal. The differential signal is phase-modulated in order to obtain the frequency-modulated carrier signal as the output signal.