Wireless Transceiver Frequency Synchronization via Envelope Detection
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Solution Overview
Problem
Existing frequency synchronization methods in wireless transceiver systems, particularly those using OFDM signals, face challenges in accurately synchronizing frequencies when the phase of the repetitive waveform is rotated by 360° or more, requiring high accuracy in the transmitter and receiver.
Innovation Solution
A wireless transceiver system that includes a transmitter with a clock generator, a fixed data item generator, and an OFDM packet generator, and a receiver with an envelope detector, comparator, packet detector, and phase-locked loop (PLL) controller, which generates and synchronizes a clock signal by comparing the envelope signal with a threshold to produce a square wave signal, allowing for accurate frequency synchronization without requiring high accuracy in the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If correlation operation using repetitive waveform is used for frequency synchronization, then frequency synchronization can be achieved, but accurate frequency offset detection becomes impossible when phase rotation exceeds 360°
Solution Approach 1:
The patent introduces an envelope signal as an intermediary to transfer frequency information from the transmitted signal to a detectable form. The envelope detector extracts amplitude variations that contain frequency offset information, making it possible to measure frequency offset even when phase rotation exceeds 360°. This intermediary approach converts an undetectable parameter (phase rotation) into a detectable one (envelope amplitude).
Solution Approach 2:
The patent replaces the conventional correlation-based frequency synchronization method with an envelope detection method. Instead of using complex correlation operations that fail when phase rotation exceeds 360°, the system substitutes a simpler envelope detection mechanism that can reliably extract frequency offset information under all phase conditions.
2Measurement precision
If high accuracy sender is provided at the receiver to achieve accurate frequency synchronization, then frequency synchronization accuracy improves, but device complexity and cost increase
Solution Approach 1:
The patent enables the receiver to perform frequency synchronization using only the transmitted signal itself, without requiring an external high-accuracy reference oscillator. The envelope detector extracts frequency information directly from the received signal's amplitude variations, allowing the system to be self-sufficient and eliminating the need for additional high-precision components.
Solution Approach 2:
The patent replaces expensive high-accuracy reference oscillators with a simple envelope detector that uses basic amplitude detection circuitry. This substitution uses lower-cost, less precise components to achieve the same frequency synchronization function, significantly reducing device complexity and cost while maintaining synchronization accuracy.
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 high-accuracy frequency synchronization between the transmitter and receiver, even when the phase is rotated by 360° or more, without needing a high-accuracy sender at the receiver.
Implementation Method 1
The first detector is configured to detect an envelope that indicates amplitude in a time waveform of the OFDM packet to obtain an envelope signal
Implementation Method 2
The PLL is configured to extract a synchronized clock signal from a main frequency component of the square wave signal, the synchronized clock signal being a signal synchronized with the clock signal
Data Source
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AI summary
According to one embodiment, a wireless transceiver system 100 includes a transmitter 101 and a receiver 151. The transmitter 101 includes a first generator 102, a second generator 103, a third generator 104. The second generator 103 generates fixed data item that has bit values corresponding to the clock signal. The third generator 104 performs OFDM modulation for the fixed data item. The receiver 151 includes a first detector 154, a second detector 156, a PLL unit 158, a controller 157. The first detector 154 is configured to detect an envelope that indicates amplitude in a time waveform. The controller 157 is configured to control to operate the PLL unit from a first time point when the head part is detected to a second time point when a first period is elapsed.