RF Optical Signal Transmission Using Unipolar Envelope Modulation
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Solution Overview
Problem
The increasing power consumption and nonlinear effects in fiber optics transmission due to high transmit optical power in wireless base stations with multi-band sharing and ultra-wide bandwidth, leading to signal distortion.
Innovation Solution
A signal transmission method that converts radio frequency electrical signals into unipolar-envelope modulated signals with symmetric upper and lower envelopes, allowing for optical modulation to generate unipolar-envelope radio frequency optical signals with low average optical power, reducing power consumption and nonlinear effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If transmit optical power is increased to increase radio frequency radiation power of the antenna, then radio frequency radiation power is improved, but power consumption of optical component increases sharply and signal distortion occurs due to nonlinear effects in fiber optics transmission
Solution Approach 1:
The patent applies asymmetry by transforming the symmetric bipolar RF electrical signal into a unipolar optical signal through envelope detection and rectification. The unipolar signal has asymmetric characteristics with only positive half-cycles, which enables more efficient optical modulation and reduces the required transmit optical power while maintaining the same RF radiation power output.
Solution Approach 2:
The patent changes the signal parameter from bipolar voltage to unipolar envelope amplitude. By detecting the envelope of the RF signal and modulating it onto an optical carrier, the system transforms the signal representation to achieve lower optical power requirements and reduced nonlinear effects in fiber transmission.
2Power
If transmit optical power is increased to increase radio frequency radiation power of the antenna, then radio frequency radiation power is improved, but signal distortion occurs due to severe nonlinear effect in fiber optics transmission
Solution Approach 1:
The unipolar signal representation with asymmetric envelope modulation reduces the dynamic range requirements and minimizes nonlinear distortion in fiber optic transmission. The rectified signal structure ensures that only the positive envelope is transmitted optically, reducing the impact of nonlinear effects that cause signal distortion.
Solution Approach 2:
The patent replaces direct bipolar voltage modulation with an optical field-based unipolar envelope modulation system. This substitution uses optical field intensity modulation instead of direct electrical voltage variation, which is less susceptible to nonlinear effects in fiber optics and reduces signal distortion.
3Quantity of substance
If conventional digital wireless fronthaul is used with multi-band sharing and ultra-wide bandwidth, then data amount increases, but power consumption of the base station increases sharply due to digital-to-analog conversion and data processing
Solution Approach 1:
The patent replaces digital baseband processing and digital-to-analog conversion with direct optical envelope modulation. By detecting the RF signal envelope and modulating it directly onto an optical carrier, the system eliminates power-consuming digital processing stages while maintaining the ability to handle multi-band and ultra-wide bandwidth signals.
Solution Approach 2:
The patent extracts only the essential envelope information from the RF signal for optical transmission, discarding the need for complete digital signal processing. This extraction approach transmits only the necessary amplitude information optically, reducing the data processing burden and power consumption at the base station.
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
Reduces optical component power consumption and signal distortion in fiber optics transmission while maintaining high radio frequency radiation power, achieved by using low transmit optical power.
Implementation Method 1
performing optical modulation on the unipolar-envelope modulated signal to obtain the first radio frequency optical signal
Implementation Method 2
optical-to-electrical conversion is performed on the radio frequency optical signal to obtain the radio frequency electrical signal
Data Source
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AI summary
A signal transmission method and an apparatus are provided. In the method, a first communication apparatus converts a first radio frequency electrical signal into a unipolar-envelope modulated signal, and sends a first radio frequency optical signal to a second communication apparatus. The first radio frequency optical signal is a unipolar-envelope radio frequency optical signal that is obtained by performing optical modulation on the unipolar-envelope modulated signal and whose lower envelope is flat and lower envelope amplitude is less than or equal to a first value. A carrier wave in the unipolar-envelope modulated signal is a sine wave. In addition, the unipolar-envelope modulated signal is a radio frequency electrical signal with a flat lower envelope, and an upper envelope of the unipolar-envelope modulated signal corresponds to an upper envelope of the first radio frequency electrical signal; or the unipolar-envelope modulated signal is a radio frequency electrical signal with a flat upper envelope, and a lower envelope of the unipolar-envelope modulated signal corresponds to a lower envelope of the first radio frequency electrical signal. This manner can reduce a transmit optical power between the first communication apparatus and the second communication apparatus, and help reduce power consumption of an optical component and a nonlinear effect in fiber optics transmission.