PLL Frequency Modulation with Drift Compensation for Data Transmission
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Solution Overview
Problem
Existing frequency modulation systems face issues with output frequency drift towards the carrier frequency during data transmission, leading to incorrect demodulation by the receiver.
Innovation Solution
A phase-locked loop with a coupling circuit and compensation unit is used to generate a frequency-modulated output signal, where a compensation signal is coupled into the loop to maintain a stable frequency difference from the carrier frequency, allowing rapid frequency changes without additional circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency modulation is used for data transmission with a phase-locked loop, then the system allows higher dynamic range and is less susceptible to interference, but the output frequency drifts towards the carrier frequency during data transmission causing incorrect demodulation
Solution Approach 1:
The patent applies preliminary anti-action by introducing a compensation signal that preemptively counteracts the frequency drift caused by the phase-locked loop. The compensation signal is generated based on the expected drift behavior and is injected into the modulation path before the drift occurs, thereby preventing the output frequency from converging to the carrier frequency and maintaining the necessary frequency difference for correct demodulation
2Stability of the object's composition
If the phase-locked loop adjusts the output frequency to the carrier frequency, then the system maintains frequency locking, but the necessary difference between output frequency and carrier frequency is lost making correct demodulation impossible
Solution Approach 1:
The patent applies local quality by creating a localized frequency offset through the compensation signal that specifically affects the modulation path without disrupting the overall phase-locked loop operation. The compensation unit introduces a controlled frequency difference locally in the modulation path, allowing the PLL to maintain its frequency locking function while preserving the necessary frequency deviation for data transmission
3Productivity
If rapid frequency changes are implemented for high bandwidth data transmission, then the data transmission bandwidth is improved, but the phase-locked loop cannot maintain stable frequency locking
Solution Approach 1:
The patent applies preliminary action by pre-generating the compensation signal based on the modulation data pattern before the actual frequency modulation occurs. This allows the compensation to be ready in advance, enabling rapid frequency changes for high bandwidth transmission while the pre-computed compensation maintains frequency locking stability by counteracting the expected drift
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 ensures stable frequency modulation during data transmission, enabling rapid frequency transitions and preventing drift towards the carrier frequency, thus ensuring correct demodulation by the receiver.
Implementation Method 1
a voltage-controlled oscillator (VCO) for generating the output signal
Implementation Method 2
a phase-locked loop for adjusting an output frequency of the output signal to a carrier frequency
Data Source
AI summary
A device for transmitting data includes a transmitter for generating a frequency-modulated output signal. The transmitter includes a phase-locked loop for adjusting an output frequency of the output signal to a carrier frequency, and a coupling circuit for coupling a data stream into the phase-locked loop. The output signal modulated in frequency by the coupled-in data stream has an output frequency variable over time, and the coupling circuit includes a compensation unit, which couples a compensation signal into the phase-locked loop. The compensation signal compensates at least approximately for an adjustment of the output frequency to the carrier frequency carried out by the phase-locked loop.