Continuous Sweep Frequency Response Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing filter frequency response testing methods are time-consuming and provide poor resolution, especially when testing multiple filters over a broad frequency range, often missing fractional frequencies and resulting in inaccurate characterization of filter bandwidth due to the use of single-tone test signals and large step sizes.
Innovation Solution
A continuously swept input signal, such as a chirp waveform, is used to generate a continuous frequency sweep, allowing for a single output signal capture and subsequent Fast Fourier Transform (FFT) analysis, with a calibration path to eliminate test system effects and provide true system response, enabling faster and more accurate frequency bandwidth testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-tone test signals are used to test filter frequency response, then the test system can measure frequency response at discrete frequencies, but the test time becomes excessively long when testing multiple filters over a broad frequency range
Solution Approach 1:
The patent applies continuous frequency sweeping instead of discrete single-tone testing. The sine wave generator continuously varies the frequency across the entire test band, allowing the filter under test to be characterized across all frequencies simultaneously rather than stepping through frequencies one at a time. This continuous action dramatically reduces test time while maintaining measurement accuracy.
Solution Approach 2:
The patent implements a calibration path that measures and stores system response characteristics before actual filter testing. This preliminary calibration data is then used to compensate for test system effects during production testing, eliminating the need to re-calibrate for each filter test and significantly reducing overall test time.
2Productivity
If discrete frequency steps are used to cover the entire frequency band, then the test can be completed in finite steps, but fractional frequencies between test frequencies cannot be tested resulting in poor resolution
Solution Approach 1:
The patent transitions from static discrete frequency points to a dynamic continuous frequency sweep. The frequency varies continuously over time, allowing measurement of all frequency points including fractional frequencies between traditional test steps. This dynamic approach provides infinite frequency resolution while maintaining efficient test completion.
3Productivity
If the step size of input test tones is increased to reduce test time, then testing becomes faster, but the response in notches or narrow pass bands may be missed resulting in incorrect characterization
Solution Approach 1:
The continuous frequency sweep ensures that no frequency points are skipped, including critical points within notches and narrow pass bands. The sine wave generator continuously varies frequency without gaps, guaranteeing that the maximum and minimum response points are captured regardless of how narrow the feature being tested.
4Measurement precision
If multiple output signal captures are performed at different frequencies, then the frequency response can be measured, but the test time increases significantly when testing multiple filters
Solution Approach 1:
The patent combines multiple frequency measurements into a single continuous sweep operation. Instead of capturing output signals at each discrete frequency point separately, the system performs one continuous sweep capturing the entire frequency response in a single operation, dramatically reducing the number of capture cycles needed.
Solution Approach 2:
The calibration path performs preliminary measurement of test system effects and stores this data for reuse. This preliminary action eliminates the need to perform time-consuming system characterizations during each production filter test, reducing test cycle time while maintaining measurement accuracy through subsequent compensation of the stored calibration data.
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 significantly reduces test time and increases data points, providing precise characterization of filter frequency response, including fractional frequencies, and is particularly effective for narrow band filters, improving the accuracy and efficiency of filter testing.
Implementation Method 1
A continuous frequency sweep signal is used as the input test signal
Implementation Method 2
The output signal is digitized and the frequency response is calculated with fast fourier transform (FFT)
Implementation Method 3
A bypass route provides a calibration factor. The test data may be divided by the calibration factor to eliminate test system effects
Data Source
AI summary
A system and method for measuring the frequency response of a system under test using a single swept-frequency chirp signal. A tapered chirp-frequency test signal is created with a bandwidth defined by first and second frequencies. The test signal is routed to a calibration path, and the output of the calibration path is routed to a digitizer. The output of the calibration path is digitized, and a Fourier transform of the calibration path output is generated. The test signal is then routed to a test system, and the output of the test system is coupled to the digitizer. The output of the test system is digitized, and a Fourier transform of the test system output is generated. A normalized frequency-domain representation of the test system created by dividing the Fourier transform of the test system output by the Fourier transform of the calibration path output.