Digital Filter Editor
Filter Designer 
- is an Engee application designed for flexible customisation and design of various types of digital filters. With this tool it is possible to design filters that fulfil different frequency response requirements, providing efficient filtering of signals in various fields such as digital signal processing, telecommunications and audio engineering.
To open the filter editor, go to the Engee application window 
and select Filter Designer . The Digital Filter Editor opens in a separate browser tab and takes some time to load:
In the editor you can select filter type, synthesis method, filter order and set frequency parameters depending on specific tasks. These functions allow you to create filters with specified characteristics.
After all the settings have been made, click the Filter synthesis button at the bottom of the editor to display the information on the graphs:
Filter Setup
The filters are configured using four modules.
Type of filter frequency response
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Module Filter AFC Type - selects the type of the amplitude-frequency response of the filter.
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Low Pass Filter (LPF) - passes low frequencies and suppresses high frequencies.
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High Pass Filter (HPF) - passes high frequencies and suppresses low frequencies.
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Bandpass filter - allows frequencies within a certain range to pass through and suppresses the rest.
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Regret filter - suppresses frequencies in a certain range and passes the rest.
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Filter synthesis method - choosing an algorithm to form the filter.
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BICH (infinite impulse response) - a filter with an infinite response to a single impulse.
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Butterworth filter - a filter with maximally flat amplitude response in the passband.
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Chebyshev1 (of the first type) - a filter with ripples in the passband and a sharp decline beyond it.
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Chebyshev2 (second type) - filter with ripples in the suppression band and a smooth decline in the passband.
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Elliptic - a filter with ripples in both the passband and suppression band.
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FIR (finite impulse response) - a filter with a finite response to a single pulse.
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Uniform - a filter with a uniform distribution of coefficients.
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Windowed - a filter created by usage of window functions to reduce side lobes.
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Filter order
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Module Filter order - selection of the polynomial degree, which determines the complexity of the filter.
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Minimum order - filter with the smallest possible number of coefficients.
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Arbitrary order - filter with the number of coefficients specified by the user.
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Parameters
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Frequency grid density factor - parameters determining the accuracy of frequency axis discretisation.
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If you select the Window synthesis method for the FIR (finite impulse response) parameter, the parameters window will change its view:
Brief description of window types
Type Description Bartlett
A triangular window that decreases smoothly to zero at the ends is used to minimise spectrum leakage.
Bartlett_Hanna.
A smoothed window that combines the characteristics of Bartlett and Hahn windows, providing good side lobe suppression.
Blackman
A window with high side lobe suppression and a wide main lobe, suitable for accurate spectral analysis.
Blackman_Harris
A variant of the Blackman window with even more side lobe suppression, often used in high dynamic range applications.
Bomana
A symmetrical window with usage of coefficients that balance the main lobe width and the level of the side lobes.
Gaussian
A window with a Gaussian distribution that provides an optimal compromise between time and frequency domain.
Kaiser
A parametric window that allows you to adjust the trade-off between the width of the main lobe and the level of the side lobes.
Nattola
A window with a smooth transition and good suppression of side lobes, used in spectral analysis.
Parzena
Smooth window with small spectrum leakage, used in signal analysis tasks.
Rectangular
Window without smooth transition, minimises spectrum leakage but creates high side lobes.
With_flat_top
A window with an extended flat area on top to improve amplitude accuracy in spectral analysis.
Taylor
A window with an adjustable number of side lobes, used to improve side lobe suppression.
Triangular
A simple window with linear reduction to zero, often used for smoothing data.
Tukey
A parametrically shaped window that goes from rectangular to cosine.
Hannah
A cosine window with a smooth reduction to zero at the ends, often used to minimise spectrum leakage.
Hamming window
A modification of the Hahn window with a smaller attenuation coefficient at the ends, used for filtering signals.
Chebyshev window
A window with uniform side lobe oscillation, ensuring that the side lobe level is minimised.
Frequency characteristics
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Module Frequency requirements - setting of key frequency characteristics of the filter.
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Dimensionality - frequency units (Hz, kHz, MHz, GHz).
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Sampling frequency - number of samples of the signal in one second.
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Passing frequency - frequency below which the signal passes through the filter.
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Suppression frequency - the frequency above which the signal is suppressed.
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Depending on the selected type of filter AFC, the number of frequency characteristics of the filter changes, e.g.:
LPF Bandpass filter 
AFC requirements
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Module AFC Requirements - enter the values of weighting coefficients W for the corresponding bands:
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W in-band - weighting factor in the passband.
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W out-of-band - weight coefficient outside the passband.
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Depending on the selected type of filter AFC, the number of W weight coefficients changes, e.g.:
LF Bandpass filter 
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If the Window synthesis method is selected for the FIR (Finite Impulse Response) parameters, the coefficient settings will be disabled for the AFC Requirements module:
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The Filter Information section shows the parameters and characteristics of the filter. The application provides the following options for graphical and numerical display of the characteristics of the designed filter:
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AFC - amplitude-frequency response of the filter, showing the dependence of the signal gain on frequency;
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FFC - phase-frequency characteristic of the filter, showing the dependence of the signal phase shift on frequency;
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AFC and FFC - joint display of amplitude-frequency and phase-frequency characteristics;
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GVZ - group delay time, showing the average delay of the signal at different frequencies;
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FZ - phase delay, showing the time delay of the signal phase;
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IC - impulse characteristic, showing the filter response to a single impulse (delta function);
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TX - transient characteristic showing the filter response to a single step function (Heaviside function);
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NPD - zero-pole diagram, defining the points of the numerator polynomial (zeros) and denominator polynomial (poles) reversal to zero.
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KF - filter coefficients (coefficients of the numerator and denominator of the filter transfer function).
Working with graphs
When hovering the cursor over a graph, the following options are available:
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Download plot as PNG.
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Zoom
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Box select
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Lasso select
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Pan
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Zoom in
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Zoom out
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Autoscale
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Reset axes (reset axes)
Download results
To upload the synthesis results, click KF (filter coefficients) in the Filter Information module:
The Calculator and Denominator columns show the coefficients of the digital filter transfer function.
Clicking on Calculator or Denominator will unload txt files - num.txt for numerator and denom.txt for denominator. In this case all denominator values are equal to one, which may indicate that we consider FIR (Finite Impulse Response) filter with finite impulse response, where the denominator is a constant.
Thus, the digital filter editor allows you to create your own filters with specified parameters, which helps in efficient signal processing.