Digital Baseband Optical Transmission for RF Signal Integrity
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Solution Overview
Problem
The quality of optical transmission in radio-over-fiber systems is compromised by noise, non-linearities, and attenuation, leading to high losses and requiring sophisticated modulation techniques and costly equipment, especially when transmitting analogue radio frequency signals over wide distances.
Innovation Solution
Transmitting digital baseband signals over optical fibers to a distributed amplification stage, where digital switch mode power amplifiers are used for amplification before upconversion to radio frequency, utilizing components like delta-sigma modulators and class D amplifiers with relaxed switching frequency requirements, and employing power mixers for efficient signal conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analogue radio frequency signals are transmitted over optical fibers, then signal transmission is achieved, but transmission quality deteriorates due to noise, non-linearities, and attenuation
Solution Approach 1:
The patent replaces the mechanical/electrical analogue signal transmission system with an optical digital signal transmission system. By converting analogue RF signals to digital baseband signals and transmitting them optically, the system avoids the harmful effects of noise, non-linearities, and attenuation that plague analogue optical transmission, thereby resolving the contradiction between achieving transmission and maintaining quality.
Solution Approach 2:
The patent fundamentally changes the signal parameters by converting from analogue domain to digital domain, and from RF frequency to baseband frequency. This parameter transformation allows the signal to be transmitted over optical fibers without suffering from the degradation mechanisms that affect analogue signals, thus improving transmission quality while maintaining reliability.
2Reliability
If sophisticated optical modulation techniques are used to compensate for transmission losses, then transmission quality improves, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex optical modulation techniques with a simpler digital baseband transmission approach. Instead of using sophisticated modulation schemes to combat transmission impairments in the analogue domain, the system transmits digital signals that are inherently more robust, thereby achieving high transmission quality with reduced device complexity and lower cost.
3Ease of manufacture
If intensity modulation and direct detection are used for optical transmission, then implementation simplicity is achieved, but costly modulators and modulator drivers are required to meet analogue RF transmission requirements
Solution Approach 1:
The patent substitutes the expensive analogue RF optical transmission path with a digital baseband optical transmission path. This eliminates the need for costly modulators and modulator drivers required for analogue RF transmission, while maintaining implementation simplicity through the use of standard digital-to-optical conversion techniques.
4Reliability
If double side band modulation is used for optical transmission, then signal transmission is achieved, but chromatic dispersion causes frequency and length dependent suppression of radio frequency power
Solution Approach 1:
The patent replaces double side band modulation with digital baseband transmission over optical fibers. This substitution eliminates the chromatic dispersion-induced frequency and length dependent suppression of RF power, as digital baseband signals are not susceptible to the same dispersion effects that plague modulated RF signals, thereby preventing information loss.
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 approach results in a cost-effective, fault-tolerant method for signal transmission, enabling efficient coverage of multiple frequency bands and communication standards with improved efficiency and reduced component stress, while minimizing the impact of chromatic dispersion and attenuation.
Implementation Method 1
electrical digital data signals are converted into optical digital data signals in at least one electro-optical converter located in the transmitting device
Implementation Method 2
the optical digital data signals are converted from optical signals into electrical signals in at least one opto-electrical converter that is located in said at least one receiving device
Data Source
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AI summary
The invention concerns a method for transmission of data signals over an optical connection (OE1) from a transmitting device (BS) to a receiving device (RAH1), wherein electrical digital data signals are converted into optical digital data signals in an electro-optical converter (EO1, EO2) located in the transmitting device (BS), the optical digital data signals are converted from optical signals into electrical signals in an opto-electrical converter (OE1) located in the receiving device (RAH1), the electrical digital data signals are amplified in the switch mode output stage (SOS) located in the receiving device (RAH1), the amplified electrical digital data signals are converted into amplified electrical analogue data signals in an analogue reconstruction device (AR) located in the receiving device (RAH1), and said amplified electrical analogue data signals are upconverted on a radio frequency in a mixer (M1) located in the receiving device (RAH1), and a receiving device therefor.