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basebandReceiver

Configure SDR as baseband receiver

Since R2022a

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Add-On Required: This feature requires the Wireless Testbench™ Support Package for NI™ USRP™ Radios add-on.

Description

Use the basebandReceiver object to configure the specified software-defined radio (SDR) as a baseband receiver to capture raw IQ data from the air.

This diagram shows a conceptual overview of capturing radio signals in Wireless Testbench™ using a radio that you configure with this object. The onboard data buffering ensures contiguous data capture. When you capture more data than the onboard memory buffer size, the data is sent directly to the host computer.

Creation

Syntax

bbrx = basebandReceiver(radio)
bbrx = basebandReceiver(radio,Name=Value)

Description

bbrx = basebandReceiver(radio) creates a baseband receiver configuration object for the specified radio radio.

Note

The object requires exclusive access to radio hardware resources. Before creating this object, clear any existing Wireless Testbench object associated with the specified radio from the workspace.

example

bbrx = basebandReceiver(radio,Name=Value) sets properties using one or more name-value arguments. For example, CaptureDataType="double" sets the data type of the returned captured data to double.

example

Input Arguments

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Radio setup configuration, specified as a string scalar. To create a radio setup configuration, set up your radio and save your radio setup configuration using the Radio Setup wizard. To list all saved radio setup configurations, call the radioConfigurations function.

For a list of supported radios, see Supported Radio Devices.

Example: "MyRadio" indicates that you saved a radio setup configuration under the name MyRadio in the Radio Setup wizard.

Properties

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Radio center frequency in Hz, specified as one of these options.

  • Positive numeric scalar — The object applies this value by scalar expansion to each antenna in the Antennas property.

  • Numeric array — The object applies the ith array element value to the ith antenna in the Antennas property.

The valid center frequency range depends on the radio device.

Radio DeviceCenter Frequency

USRP™ N300

1 MHz to 6 GHz

USRP N310

1 MHz to 6 GHz

USRP N320

1 MHz to 6 GHz

USRP N321

1 MHz to 6 GHz

USRP X300

10 MHz to 6 GHz

USRP X310

10 MHz to 6 GHz

USRP X410

1 MHz to 8 GHz

Note

When setting this property for multiple antennas on a USRP N300 or USRP N310 radio, consider these hardware characteristics.

  • The antenna ports on the RF0 and RF1 radio channels use the same center frequency. Therefore, set identical center frequency values for the antennas specified as "RF0:RX2" and "RF1:RX2".

  • The antenna ports on the RF2 and RF3 radio channels use the same center frequency. Therefore, set identical center frequency values for the antennas specified as "RF2:RX2" and "RF3:RX2". These antennas are available only on a USRP N310 radio.

Data Types: double

Capture radio antennas, specified as one of these options.

  • String scalar — Specify use of single antenna.

  • String array — Specify use of multiple antennas.

Use this table to identify a supported radio antenna port on the radio device and the corresponding string constant that you can specify for this property. The default value depends on the radio.

Radio DeviceSupported Antenna PortString Scalar

USRP N300

RF0 channel: RX2 port"RF0:RX2" (default)
RF1 channel: RX2 port"RF1:RX2"

USRP N310

RF0 channel: RX2 port"RF0:RX2" (default)
RF1 channel: RX2 port"RF1:RX2"
RF2 channel: RX2 port"RF2:RX2"
RF3 channel: RX2 port"RF3:RX2"

USRP N320

RF0 channel: RX2 port"RF0:RX2" (default)
RF1 channel: RX2 port"RF1:RX2"

USRP N321

RF0 channel: RX2 portRF0 channel: RX2 port
RF0 channel: RX2 portRF0 channel: RX2 port

USRP X300

RFA channel: RX2 port

"RFA:RX2" (default)

RFB channel: RX2 port

"RFB:RX2"

USRP X310

RFA channel: RX2 port

"RFA:RX2" (default)

RFB channel: RX2 port

"RFB:RX2"

USRP X410

DB0 RF0 channel: RX 1 port

"DB0:RF0:RX1" (default)

DB0 RF1 channel: RX 1 port

"DB0:RF1:RX1"

DB1 RF0 channel: RX 1 port

"DB1:RF0:RX1"

DB1 RF1 channel: RX 1 port

"DB1:RF1:RX1"

Note

When you update this property, the execution time of the next object function call increases by a few seconds.

Example: Antennas=["RF0:RX2","RF1:RX2"] specifies two capture antennas.

Data Types: string

Capture radio gain in dB, specified as one of these options.

  • Positive numeric scalar — The object applies this value by scalar expansion to each antenna that you specify in the Antennas property.

  • Numeric array — The object applies the ith array element value to the ith antenna in the Antennas property.

The valid gain range depends on the radio device.

Radio DeviceCapture Radio Gain

USRP N300

0 dB to 75 dB

USRP N310

0 dB to 75 dB

USRP N320

0 dB to 60 dB

USRP N321

0 dB to 60 dB

USRP X300

0 dB to 31.5 dB

USRP X310

0 dB to 31.5 dB

USRP X410

0 dB to 60 dB

Data Types: double

Baseband sample rate in Hz, specified as a positive numeric scalar. For more information on how the radio achieves the specified sample rate, see Baseband Sample Rate in NI USRP Radios.

The valid sample rate depends on the radio device.

Radio DeviceSample Rate

USRP N300

  • 120,945 Hz to 76.8 MHz

  • 122.88 MHz

  • 125.00 MHz

  • 153.60 MHz (default)

USRP N310

USRP N320

  • 196,851 Hz to 125 MHz

  • 200.00 MHz

  • 245.76 MHz

  • 250.00 MHz (default)

USRP N321

USRP X300

  • 181,418 Hz to 100 MHz

  • 184.32 MHz

  • 200.00 MHz (default)

USRP X310

USRP X410

  • 241,890 Hz to 125 MHz

  • 245.76 MHz

  • 250.00 MHz (default)

Note

When you update this property, the execution time of the next object function call increases by a few seconds.

Data Types: double

Data type of the captured data, specified as "int16", "double", or "single". Use this property to set the data type of the captured data that the capture object function returns.

Note

When you update this property, the execution time of the next object function call increases by a few seconds.

Data Types: string

Behavior of the capture object function upon dropped samples, specified as one of these values.

  • "error" — The object function stops with an error message.

  • "warning" — The object function displays a warning message.

  • "none" — The object function ignores dropped samples.

Data Types: string

Object Functions

captureCapture IQ data using baseband receiver or transceiver
isCapturingStatus of capture running in background using baseband receiver
captureOutputsRetrieve outputs from capture run in background using baseband receiver
stopCaptureStop capture running in background using baseband receiver

Examples

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Open Live Script

Create a baseband receiver object, specifying a radio setup configuration previously saved in the Radio Setup wizard.

bbrx = basebandReceiver("MyRadio")
bbrx = 
  basebandReceiver with properties:

               RadioGain: 10
         CenterFrequency: 2.4000e+09
              SampleRate: 250000000
                Antennas: "RF0:RX2"
    DroppedSamplesAction: "error"
         CaptureDataType: "int16"

Set the baseband sample rate and center frequency.

bbrx.SampleRate = 122.88e6;
bbrx.CenterFrequency = 2.2e9;

Capture 3 ms of IQ data with the radio associated with the baseband receiver object using the default antenna. 

[data,~] = capture(bbrx,milliseconds(3));
Open Live Script

Create a baseband receiver object, specifying a radio setup configuration previously saved in the Radio Setup wizard. Specify two antennas, each with a different center frequency.

bbrx = basebandReceiver("MyRadio", ...
    Antennas=["RF0:RX2" "RF1:RX2"], ...
    CenterFrequency=[2.2e9,2.4e9])
bbrx = 
  basebandReceiver with properties:

               RadioGain: 10
         CenterFrequency: [2.2000e+09 2.4000e+09]
              SampleRate: 153600000
                Antennas: ["RF0:RX2"    "RF1:RX2"]
    DroppedSamplesAction: "error"
         CaptureDataType: "int16"

Capture 10000 IQ samples with the radio associated with the baseband receiver object. 

length = 10000;
[data,~] = capture(bbrx,length);

The output data is a 10000 x 2 array. Each column contains the data captured on one antenna, in the order that they are specified.

Open Live Script

Create an anonymous function, showSignalPower, that calculates the average signal power of captured data and displays it in the command window.

showSignalPower = @(data, timestamp, ~) ...
    disp("Signal captured at " + string(timestamp)...
    + " has average power of " + string(10*log10(mean(abs(data).^2))) + " dB");

Create a basebandReceiver object, specifying a radio setup configuration previously saved using the Radio Setup wizard. Specify the data type of data captured with this object as "double".

bbrx = basebandReceiver("MyRadio","CaptureDataType","double")
bbrx = 
  basebandReceiver with properties:

               RadioGain: 10
         CenterFrequency: 2.4000e+09
              SampleRate: 250000000
                Antennas: "RF0:RX2"
    DroppedSamplesAction: "error"
         CaptureDataType: "double"

Capture 10 ms of IQ data and specify the showSignalPower function to run when the capture operation completes.

[data, timestamp, droppedSamples] = capture(bbrx,milliseconds(10),CompletionFcn=showSignalPower);
Signal captured at 27-Nov-2023 15:56:38 has average power of -48.506 dB
Open Live Script

Create a baseband receiver object, specifying a radio setup configuration previously saved in the Radio Setup wizard.

bbrx = basebandReceiver("MyRadio")
bbrx = 
  basebandReceiver with properties:

               RadioGain: 10
         CenterFrequency: 2.4000e+09
              SampleRate: 250000000
                Antennas: "RF0:RX2"
    DroppedSamplesAction: "error"
         CaptureDataType: "int16"

Capture 100 ms of IQ data and save it to a file in the basebandData folder called capture1.mat. 

mkdir('basebandData');
[dataPath,~] = capture(bbrx,milliseconds(100),SaveLocation='basebandData/capture1.mat');

Load the data into the workspace.

load(dataPath,'data');
Open Live Script

Create a baseband receiver object, specifying a radio setup configuration previously saved in the Radio Setup wizard. 

bbrx = basebandReceiver("MyRadio")
bbrx = 
  basebandReceiver with properties:

               RadioGain: 10
         CenterFrequency: 2.4000e+09
              SampleRate: 153600000
                Antennas: "RF0:RX2"
    DroppedSamplesAction: "error"
         CaptureDataType: "int16"

Capture 1 s of IQ data in the background and save it to a file in the basebandData folder called capture1.mat.

mkdir('basebandData');
capture(bbrx,seconds(1),SaveLocation='basebandData/capture1.mat',Background=true);

Check if the capture is in progress.

isCapturing(bbrx)
ans = logical
   1

Wait for the capture to complete.

while isCapturing(bbrx)
    pause(0.1);
end

Check that the capture is no longer in progress. 

isCapturing(bbrx)
ans = logical
   0

Retrieve the outputs of the capture operation and load the captured IQ data into the workspace.

[dataPath,~] = captureOutputs(bbrx);
load(dataPath,'data');

Tips

  • You cannot use save and load to store and reload Wireless Testbench objects. Instead, you can re-create the object with these steps:

    1. Write code to create a basebandReceiver object with a saved radio setup configuration radio and set the properties.

    2. Save the code to a script.

    3. Run the script in a new MATLAB® session with the same saved radio setup configuration.

  • To check your host performance capability for capturing data, see the Evaluate Host Capture Performance example. This example shows you how to identify the highest sample rate at which contiguous IQ data can be captured with your hardware setup.

Version History

Introduced in R2022a

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See Also

Functions

Objects

Topics