OFDM Receiver FFT Window Control via Signal Delay Switching
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Solution Overview
Problem
Existing OFDM receiving apparatuses face challenges in preventing phase rotation of signals after FFT due to changes in transmission channels, especially when receiving signals while moving, which increases the circuit size required for phase-rotation correction and limits the ability to follow rapid channel changes.
Innovation Solution
A receiving apparatus with a window control unit that generates multiple delay signals with different delay amounts and a signal switching unit to adjust the FFT window position without changing the reference point, preventing phase rotation by switching between these signals based on predetermined timing, thereby reducing the need for a phase-rotation correction circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the FFT window position is controlled in a unit of a data sample of the received signal, then the position can be adjusted to track channel changes, but phase rotation occurs and circuit size increases
Solution Approach 1:
The invention segments the received signal into multiple delay signals with different delay amounts. By dividing the signal processing into separate delay paths, the system can switch between different delay signals to adjust the FFT window position without causing phase rotation, thereby tracking channel changes while avoiding the need for complex phase-rotation correction circuits.
Solution Approach 2:
The invention makes the FFT window position adjustable and dynamic by switching between multiple delay signals based on channel conditions. This dynamic adjustment allows the system to adapt to rapid channel changes in mobile environments while maintaining signal integrity and avoiding phase rotation issues.
2Adaptability or versatility
If the clock frequency is offset to move the FFT window position, then the window position can be adjusted, but rapid channel changes cannot be followed due to clock deviation influence
Solution Approach 1:
The invention implements dynamic control of the FFT window position by switching between multiple delay signals with different delay amounts. This allows rapid adjustment of the window position in response to channel changes without being constrained by clock frequency offset limitations, thereby improving the system's ability to track rapid channel variations in mobile environments.
Solution Approach 2:
The invention changes the delay amount parameter of the delay signals to adjust the FFT window position. By varying the delay amount among multiple pre-generated delay signals, the system can rapidly respond to channel changes without introducing clock deviation effects, thus improving response speed while maintaining accurate window positioning.
3Reliability
If the FFT window position changes to track channel variations, then reception quality improves, but phase rotation occurs requiring correction circuits
Solution Approach 1:
The invention segments the signal processing into multiple delay paths, each with a different delay amount. This segmentation allows the system to switch between delay signals to adjust the FFT window position without causing phase rotation, thereby maintaining high reception quality in mobile environments while avoiding the need for additional phase-rotation correction circuits.
Solution Approach 2:
The invention creates multiple copies of the received signal with different delay amounts applied. By switching between these copied and delayed signals, the system can adjust the FFT window position to track channel variations without introducing phase rotation, thus improving reception quality while keeping the circuit design simple.
Data Source
AI summary
An object of the present invention is to provide a receiving apparatus and a receiving method capable of preventing phase rotation of a signal after FFT from occurring on a frequency domain. Further, the receiving apparatus according to the present invention is provided with: a window control unit configured to control a position of an FFT window in which FFT is performed to the time domain signal, and output FFT data corresponding to the FFT window; a signal delaying unit configured to generate, from the time domain signal, a plurality of delay signals with different delay amounts; and a signal switching unit having a switch for outputting by switching between two of the time domain signal and the plurality of delay signals based on a predetermined switch timing, the signal switching unit being configured to output the FFT data including the output signal of the switch.