Dynamic FFT Length Adjustment for Mobile Terminal Signal Testing
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Solution Overview
Problem
Existing mobile terminal test apparatuses struggle to perform FFT processes reliably on signals with short lengths that do not conform to communication standards, leading to measurement errors due to inappropriate FFT windowing.
Innovation Solution
A receiving device with a signal length calculation unit, FFT length setting unit, and resolution bandwidth setting unit that adjusts the FFT length and resolution bandwidth based on the measured signal length to prevent data-less section processing and minimize measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed FFT length conforming to communication standard is used, then standard signal processing is simplified, but measurement accuracy deteriorates for short non-standard signals
Solution Approach 1:
The FFT length is changed from a fixed standard value to a dynamic value that adapts to the actual signal length. The receiving device calculates the signal length and selects an appropriate FFT length from multiple candidates, enabling the system to handle both standard and non-standard signals accurately.
Solution Approach 2:
The FFT length parameter is made variable based on signal characteristics. Multiple FFT length candidates are prepared in advance, and the receiving device selects the appropriate candidate based on the calculated signal length, thereby optimizing measurement accuracy for different signal types.
2Measurement precision
If FFT length is reduced to match short signal length, then measurement accuracy improves, but frequency resolution deteriorates
Solution Approach 1:
The receiving device dynamically selects from multiple FFT length candidates based on the actual signal length. This dynamic selection allows the system to optimize between measurement accuracy and frequency resolution depending on the specific signal characteristics being measured.
Solution Approach 2:
Multiple FFT length parameters are prepared in advance as candidates. The receiving device changes the FFT length parameter based on signal length calculations, enabling flexible optimization of the trade-off between measurement accuracy and frequency resolution for different measurement scenarios.
3Productivity
If standard window function section width is used, then processing of standard signals is efficient, but reliability deteriorates for short non-standard signals
Solution Approach 1:
The window function section width is made dynamic by preparing multiple candidates corresponding to different FFT lengths. The receiving device selects the appropriate window function width based on the calculated signal length, ensuring reliable FFT processing for both standard and non-standard signals while maintaining efficiency.
4Speed
If FFT process is performed on signals shorter than FFT length, then processing speed is maintained, but measurement reliability deteriorates due to data-less sections
Solution Approach 1:
The receiving device performs preliminary calculation of signal length before the FFT process. Based on this preliminary information, it selects an appropriate FFT length candidate that matches the signal characteristics, preventing the reliability issue of processing short signals with overly long FFT lengths while maintaining efficient processing.
Solution Approach 2:
The FFT length is dynamically adjusted based on preliminary signal length calculations. This dynamic adjustment ensures that the FFT process is performed with an appropriate length for each signal, maintaining both processing speed and measurement reliability by avoiding data-less sections in the FFT analysis.
Data Source
AI summary
A receiving device includes a reception unit 10 that samples a signal to be measured a transmitted from a DUT 2 and acquires a sample signal d; an FFT processing unit 21 that performs an FFT process by multiplying the sample signal; a signal length calculation unit 31 that calculates a signal length of the signal to be measured from the sample signal; a comparing unit 33 that compares the calculated signal length of the signal to be measured with a first FFT length conforming to a communication standard; and an FFT length setting unit 34 that, when as a result of the comparison by the comparing unit, the signal length is shorter than the first FFT length, sets a second FFT length shorter than the signal length of the signal to be measured, as the FFT length of the FFT process by the FFT processing unit.