Table Of Contents

Filter Order Estimation (Inverse Chebyshev) (G Dataflow)

Version:
    Last Modified: March 15, 2017

    Estimates the Inverse Chebyshev filter order.

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    filter type

    The type of filter that this node estimates.

    Name Description
    Lowpass

    Estimates a lowpass filter.

    Highpass

    Estimates a highpass filter.

    Bandpass

    Estimates a bandpass filter.

    Bandstop

    Estimates a bandstop filter.

    Default: Lowpass

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    frequency specifications

    Band edge frequencies of the filter, in Hz.

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    lower pass frequency

    First passband edge frequency in Hz.

    Default: 0.2

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    lower stop frequency

    First stopband edge frequency in Hz.

    Default: 0.3

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    higher pass frequency

    Second passband edge frequency in Hz. The node ignores this input for lowpass and highpass filters.

    Default: 0

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    higher stop frequency

    Second stopband edge frequency, in Hz. The node ignores this input for lowpass and highpass filters.

    Default: 0

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    ripple specifications

    Ripple level in the passband and stopband of the filter.

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    passband

    Ripple level in the passband.

    Default: 0.1

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    stopband

    Ripple level in the stopband.

    Default: 60

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    dB?

    A Boolean value that specifies whether this node applies a decibel scale or a linear scale to the ripple levels.

    True The node applies a decibel scale to the ripple level.
    False The node applies a linear scale to the ripple level.

    Default: True

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    error in

    Error conditions that occur before this node runs.

    The node responds to this input according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

    Default: No error

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    sampling frequency

    The sampling frequency in Hz.

    This value must be greater than zero.

    Default: 1.0 Hz, which is the normalized sampling frequency

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    estimated order

    Minimum order value that the filter requires to meet the specifications you set.

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    low cutoff frequency

    Low cutoff frequency. The cutoff frequency corresponds to the edge frequency of the stopband.

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    high cutoff frequency

    High cutoff frequency. The cutoff frequency corresponds to the edge frequency of the stopband.

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    error out

    Error information.

    The node produces this output according to standard error behavior.

    Standard Error Behavior

    Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

    error in does not contain an error error in contains an error
    If no error occurred before the node runs, the node begins execution normally.

    If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

    If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.
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    stopband attenuation

    Stopband attenuation in decibels.

    Algorithm for Inverse Chebyshev Order Estimation

    This node uses the following equations to estimate the order of an Inverse Chebyshev filter:

    N = acosh ( ε s / ε p ) acosh ( Ω s / Ω p )
    ε p = 10 A p / 10 1
    ε s = 10 A s / 10 1
    where
    • N is the estimated order
    • Ap is the passband ripple in dB
    • As is the stopband ripple in dB
    • means Round Toward + Infinity

    The following table lists the equations for calculating Ω p and Ω s for different types of filters:

    Lowpass filter

    Ω p = Ω p 1

    Ω s = Ω s 1

    Highpass filter

    Ω p = 1 / Ω p 1

    Ω s = 1 / Ω s 1

    Bandpass filter

    Ω p = Ω p 2 Ω p 1

    Ω s = min ( | Ω s 1 Ω p 1 Ω p 2 Ω s 1 | , | Ω s 2 Ω p 1 Ω p 2 Ω s 2 | )

    Bandstop filter

    Ω p = max ( | 1 Ω p 1 Ω s 1 Ω s 2 Ω p 1 | , | 1 Ω p 2 Ω s 1 Ω s 2 Ω p 2 | )

    Ω s = 1 Ω s 2 Ω s 1

    where the various Ω values equal as follows:

    Ω p 1 = tan ( π * lower pass frequency sampling frequency )
    Ω p 2 = tan ( π * higher pass frequency sampling frequency )
    Ω s 1 = tan ( π * lower stop frequency sampling frequency )
    Ω s 2 = tan ( π * higher stop frequency sampling frequency )

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: This product does not support FPGA devices


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