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NVGate 2021: Release note (view source)
Revision as of 14:08, 28 December 2020
, 14:08, 28 December 2020→Enrich your measurements in real time: from GPS to environmental metadata
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[[File:kiné_select_edit.png|400px]] | [[File:kiné_select_edit.png|400px]] | ||
= Relax the limits of filtering! = | |||
All details on the filters can be read [[NVGate_Filter_Builder|here]] | |||
===New prototype filters=== | |||
In addition to the Butterworth filter, now you can build the IIR filters with the Chebyshev type I (band-pass ripple) filter or Chebyshev type II (stop-band ripple) filter. | |||
The Butterworth filter has flat response in both the pass band and stop band, but its transition band is wide. | |||
The Chebyshev type I (band-pass ripple filter) has the steepest roll-off among the three filters, and its response in the stop band is flat. However, it has ripples in the pass band. | |||
The Chebyshev type II (stop-band ripple) filter has flat response in the pass band, but it has ripples in the stop band. Its transition band is narrower than the Butterworth filter, but wider than the Chebyshev type I. | |||
Below is an example showing these three filters with the same filter order. | |||
[[File:filters_3.png|600px]] | |||
Thanks to its maximal flat frequency response in the pass band, the Butterworth filter is commonly used in applications where signal distortion should be minimized, such as audio noise reduction. It is also widely used for anti-aliasing. The Chebyshev filters are optimized to provide steep roll-off, and they are usually used in applications where the maximum rejection of the nearby frequencies is required. | |||
==Increased filter order== | |||
The order of the filter affects the steepness of its roll-off. The higher the order is, the sharper the transition between the pass band and the stop band is. An example demonstrating the impact of the filter order is shown below. | |||
[[File:butterworth_freq_response.png|600px]] | |||
For the high pass and low pass filters, the filter order can be selected from 1 to 40 in the Office mode, and from 1 to 10 in the Connected mode now. In the previous NVGate version, the maximum filter order was 6. | |||
For the band pass and band stop filters, the filter order is 2*N, and N can be selected from 1 to 30 in the Office mode, and between 1 to 10 in the Connected mode now. In the previous NVGate version, the maximum value of N was 5. | |||
===Relaxed constraints on the cut-off frequency=== | |||
To guarantee the stability of the filter, there are certain constraints on the value of the cut-off frequency. Compared with previous version of NVGate, such constraints are relaxed significantly now. | |||
[[File:image_2020-11-27_095451.png|600px]] | |||
For the high pass and low pass filters, the maximum value of the cut-off frequency is the input frequency range '''FR'''. The minimum value is '''FR''' / 50000 in the Office mode, and '''FR''' / 40000 in the Connected mode. In the previous NVGate version, the minimum value was '''FR''' / 40 for the low pass filter, and '''FR''' / 400 for the high pass filter. | |||
For the band pass and band stop filters, the low cut-off frequency ''f''<sub>low</sub> and the high cut-off frequency ''f''<sub>high</sub> need to meet the following conditions in the Office mode: | |||
* ''f''<sub>low</sub> ≥ 0.0001 * '''FR''' | |||
* ''f''<sub>high</sub> ≤ '''FR''' | |||
* 0.0004 * '''FR''' ≤ ''f''<sub>high</sub> - ''f''<sub>low</sub> ≤ 0.9998 * '''FR''' | |||
And in the Connected mode, the conditions are as below: | |||
* ''f''<sub>low</sub> ≥ 0.0005 * '''FR''' | |||
* ''f''<sub>high</sub> ≤ '''FR''' | |||
* 0.000675 * '''FR''' ≤ ''f''<sub>high</sub> - ''f''<sub>low</sub> ≤ 0.99 * '''FR''' | |||
In the previous NVGate version, the conditions on the cut-off frequencies were: | |||
* ''f''<sub>low</sub> ≥ 0.055 * '''FR''' | |||
* ''f''<sub>high</sub> ≤ '''FR''' | |||
* 0.0075 * '''FR''' ≤ ''f''<sub>high</sub> - ''f''<sub>low</sub> ≤ 0.99 * '''FR''' | |||
==Improved precision== | |||
Now, the filters are calculated in 64-bit floating point format in the Office mode, and in 40-bit floating point format in the Connected mode. In the previous NVGate version, the 32-bit floating point format was used in both modes. | |||
===Octave overall no limitation=== | |||
1/n Octave Overall levels frequency range plug-ins are now editable. You can define the min and max. | |||
This overall is computed in the time domain (weighting filter and detector). Processing weighting in the time domain provides accurate measurement for non-stationary signals (impulsive). | |||
[[File:octave_filter.png|400px]] | |||
'''Full range mode''' computes the overall on the whole frequency range excluding the DC component. (The minimum range is defined by "CPB filters Lower central frequency"/5). | |||
'''Limited range''' lets the user define the range by changing the low cut off frequency and high cut off frequency. | |||
===Application=== | |||
=== global level with filter=== | |||
=== remove noise from spectrum=== | |||
===Listen signal with filter=== | |||
= Enrich your measurements in real time: from GPS to environmental metadata = | = Enrich your measurements in real time: from GPS to environmental metadata = | ||