This is machine translation

Translated by Microsoft
Mouseover text to see original. Click the button below to return to the English version of the page.

Note: This page has been translated by MathWorks. Click here to see
To view all translated materials including this page, select Country from the country navigator on the bottom of this page.

Baseband Sampling Rate and Filter Chains

You can set the baseband sampling rate and filter chains for the AD9361 RF chip on the USRP®[1] E310 embedded series radio hardware. The options you choose depend on how much control you want over the design of the filters in the transmit or receive chains. You can have the software design the filter chain automatically, or you can manually design the filter chain according to your own specification.

When you set the baseband rate on a transmitter or receiver System object™ or block, the software applies the default filter design to the filter chain. This process calculates the analog filters, interpolation and decimation filters, and FIR coefficients for your specified sample rate. The default filter design parameters are as follows:

  • The passband edge frequency of the overall lowpass filter is a third of the baseband sample rate.

  • The stopband edge frequency of the filter is 1.25 times the passband edge frequency.

  • For a transmit filter chain, the RF bandwidth is 1.6 times the transmit stopband edge frequency.

  • For a receive filter chain, the RF bandwidth is 1.4 times the receive stopband edge frequency.

If you need different settings, you can change the settings by invoking the AD9361 Filter Design Wizard from Analog Devices®.

The filter wizard requires the following MathWorks® products:

  • MATLAB®

  • Signal Processing Toolbox™

  • DSP System Toolbox™

For instructions on operating the filter wizard, see MATLAB Filter Design Wizard for AD9361 of the Analog Devices website.

Filter Design with Blocks

Design Custom Filter

To open the AD9361 Filter Design Wizard, on the Advanced tab of the block mask, click Design custom filter. The initial settings are the default filter design settings.

In the filter wizard:

  1. Update the settings to meet the requirements of your application.

  2. Click Design Filter.

  3. Click Apply filter design.

  4. Click OK on the dialog box informing you that the design was saved to a block mask.

  5. Close the filter wizard.

Filter Design with System Objects

Design Custom Filter

  1. Create a transmitter or receiver System object. Open the AD9361 Filter Design Wizard by calling designCustomFilter. For example:

    tx = sdrtx('E310','BasebandSampleRate',10e6)
    designCustomFilter(tx)
  2. In the filter wizard:

    1. Update the settings to meet the requirements of your application.

    2. Click Design Filter.

    3. Click Apply filter design.

    4. Click OK on the dialog box informing you that the design was saved to a System object.

    5. Close the filter wizard.

Save and Restore Custom Filter Design

  1. Create a name-value cell array that represents all the necessary settings for the filter design based on the System object, then save it.

    filtnv = { ...
    'BasebandSampleRate',tx.BasebandSampleRate, ...
    'FIRCoefficientSize',tx.FIRCoefficientSize, ...
    'FIRCoefficients',tx.FIRCoefficients, ...
    'FIRGain',tx.FIRGain, ...
    'FIRDecimInterpFactor',tx.FIRDecimInterpFactor, ...
    'AnalogFilterCutoff',tx.AnalogFilterCutoff, ...
    'FilterPathRates',tx.FilterPathRates, ...
    'FilterDesignTypeForRx',tx.FilterDesignTypeForRx, ...
    'FilterDesignTypeForTx',tx.FilterDesignTypeForTx ...
    };
    save 'mycustomfilter' 'filtnv'
    
  2. Restore custom filter to a new object. The 'ShowInternalProperties' argument is used to avoid warnings when setting the filter properties and is not strictly necessary for restoring a filter.

    clear all
    load mycustomfilter
    rx = sdrrx('E310','ShowInternalProperties',true,filtnv{:});
    rx.ShowInternalProperties = false

See Also

Functions

Blocks

System Objects

External Websites


[1] USRP, USRP2, UHD, and Ettus Research are trademarks of National Instruments Corp.