basebandTransmitter

Configure SDR as baseband transmitter

Since R2022a

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

Description

Use the basebandTransmitter object to configure the specified software-defined radio (SDR) as a baseband transmitter to transmit IQ waveforms to the air.

This diagram shows the conceptual overview of transmitting radio signals in Wireless Testbench™ using a radio that you configure with this object. The onboard data buffering ensures contiguous data transmit. The transmission controller enables you to specify continuous or single-shot transmissions.

Creation

Syntax

bbtx = basebandTransmitter(radio)

bbtx = basebandTransmitter(radio,PropertyName=Value)

bbrx = basebandTransceiver(radio,Preload=true)

Description

bbtx = basebandTransmitter(radio) creates a baseband transmitter application 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 application object associated with the specified radio from the workspace.

bbtx = basebandTransmitter(radio,PropertyName=Value) sets properties using one or more name-value arguments. For example, CenterFrequency=2.2e9 sets the center frequency to 2.2 GHz.

bbrx = basebandTransceiver(radio,Preload=true) loads the application onto the radio during object creation. (since R2025a)

Use this syntax when you plan to schedule or synchronize operations using the radio time.

Input Arguments

radio — Radio setup configuration

string scalar | radio object

Radio setup configuration, specified as one of these options.

• String scalar — The name of a radio setup configuration you saved using the Radio Setup wizard. To list all saved radio setup configurations, call the radioConfigurations function with no input arguments. For example, "MyRadio".

• Radio object — A radio object that corresponds to a radio setup configuration you saved using the Radio Setup wizard. For example, to create a radio object for a radio setup configuration with the name "MyRadio", call radio = radioConfigurations("MyRadio").

  Use this option when you want to use synchronization features. You can refer to radio object properties to get information about the radio setup configuration that the object corresponds to, such as the model number of the radio, the radio IP address, and the synchronization options. Additionally, you can:

  • Check the lock status of the reference clock, local oscillators, or GPS disciplined oscillator (GPSDO) on the radio using the referenceLockedStatus, loLockedStatus, and gpsLockedStatus functions respectively.

  • Get the current radio time using the getRadioTime function.

  • Synchronize multiple devices by setting the radio time using the getTimeLastPPS and setTimeNextPPS functions.

  • Get time and GPS information from the radio using the getGPSTime and getGPSNMEA functions.

  • Schedule synchronized property updates on your basebandTransmitter object using the setCommandTime, getCommandTime, and clearCommandTime functions.

  For more information, see Time Synchronize Operations on NI USRP Radios.

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

Preload — Option to load the application onto the radio

false (default) | true

Since R2025a

Option to load the application onto the radio, specified as one of these options.

• false — The application is loaded onto the radio the first time you call the transmit function.

• true — Load the application onto the radio during object creation. This takes a few extra seconds.

  Use this option when you plan to schedule or synchronize operations that use this object. Loading the application onto the radio at object creation prevents the radio time from being reset when you the transmit function. Specifying properties during object creation is also recommended, as updating some object properties will cause the radio time to be reset.

Data Types: logical

Properties

CenterFrequency — Radio center frequency in Hz

2.4e9 (default) | positive numeric scalar | numeric array

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 Device	Center 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:TX/RX" and "RF1:TX/RX".

• 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:TX/RX" and "RF3:TX/RX". These antennas are available only on a USRP N310 radio.

Data Types: double

Antennas — Transmit radio antennas

string scalar | string array

Transmit 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 Device	Supported Antenna Port	String Scalar
USRP N300	RF0 channel: TX/RX port	"RF0:TX/RX" (default)
	RF1 channel: TX/RX port	"RF1:TX/RX"
USRP N310	RF0 channel: TX/RX port	"RF0:TX/RX" (default)
	RF1 channel: TX/RX port	"RF1:TX/RX"
	RF2 channel: TX/RX port	"RF2:TX/RX"
	RF3 channel: TX/RX port	"RF3:TX/RX"
USRP N320	RF0 channel: TX/RX port	"RF0:TX/RX" (default)
	RF1 channel: TX/RX port	"RF1:TX/RX"
USRP N321	RF0 channel: TX/RX port	"RF0:TX/RX" (default)
	RF1 channel: TX/RX port	"RF1:TX/RX"
USRP X300	RFA channel: TX/RX port	"RFA:TX/RX" (default)
	RFB channel: TX/RX port	"RFB:TX/RX"
USRP X310	RFA channel: TX/RX port	"RFA:TX/RX" (default)
	RFB channel: TX/RX port	"RFB:TX/RX"
USRP X410	DB0 RF0 channel: TX/RX 0 port	"DB0:RF0:TX/RX0" (default)
	DB0 RF1 channel: TX/RX 0 port	"DB0:RF1:TX/RX0"
	DB1 RF0 channel: TX/RX 0 port	"DB1:RF0:TX/RX0"
	DB1 RF1 channel: TX/RX 0 port	"DB1:RF1:TX/RX0"

Note

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

Example: Antennas=["RF0:TX/RX","RF1:TX/RX"] specifies two transmit antennas.

Data Types: string

RadioGain — Transmit radio gain in dB

10 (default) | positive numeric scalar | numeric array

Transmit 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 Device	Transmit Radio Gain
USRP N300	0 dB to 65 dB
USRP N310	0 dB to 65 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

SampleRate — Baseband sample rate in Hz

highest device sample rate (default) | positive numeric scalar

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 Device	Sample 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) 491.52 MHz (since R2025a) 500 MHz (since R2025a)

Note

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

• If you have a USRP X410 radio and you change the SampleRate property between a sample rate greater than 250 MHz and a sample rate less than or equal to 250 MHz, a new FPGA image is loaded to the radio when you call the transmit function. This can take up to a minute.

Data Types: double

TransmitDataType — Data type of transmitted data

"int16" (default) | "double" | "single"

Since R2025a

Data type of the transmitted data, specified as "int16", "double", or "single".

Use this property to specify the data type of the data that you transmit with the transmit function.

Note

• You must specify a waveform with the same data type in your call to the transmit function, or the data type you specify with this argument will be overwritten.

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

Data Types: string

Object Functions

transmit	Transmit waveform using baseband transmitter or transceiver
stopTransmission	Stop transmission from baseband transmitter or transceiver

Examples

Configure Baseband Transmitter and Transmit Waveform

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

bbtx = basebandTransmitter("MyRadio")

bbtx = 
  basebandTransmitter with properties:

          RadioGain: 10
    CenterFrequency: 2.4000e+09
         SampleRate: 250000000
           Antennas: "RF0:TX/RX"

Set the baseband sample rate and center frequency.

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

Generate random transmit waveform.

txWaveform = complex(randn(1000,1),randn(1000,1));

Transmit the generated waveform continuously with the radio associated with the baseband transmitter object using the default antenna.

transmit(bbtx,txWaveform,"continuous");

Stop the continuous transmission after 5 seconds.

pause(5);
stopTransmission(bbtx);

Transmit Data on Multiple Antennas with Baseband Transmitter

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

bbtx = basebandTransmitter("MyRadio", ...
    Antennas=["RF0:TX/RX" "RF1:TX/RX"], ...
    CenterFrequency=[2.2e9 2.4e9])

bbtx = 
  basebandTransmitter with properties:

          RadioGain: 10
    CenterFrequency: [2.2000e+09 2.4000e+09]
         SampleRate: 153600000
           Antennas: ["RF0:TX/RX"    "RF1:TX/RX"]

Generate two random complex transmit waveforms.

txWaveform = [complex(randn(1000,1),randn(1000,1)), ...
    complex(randn(1000,1),randn(1000,1))];

Transmit the generated waveform once with the radio associated with the baseband transmitter object.

transmit(bbtx,txWaveform,"once");

Transmit Data at Scheduled Time with Baseband Transmitter

Create a radio object, specifying a radio setup configuration previously saved using the Radio Setup wizard.

radio = radioConfigurations("MyRadio")

radio = 
  X310 with properties:

           Name: "MyRadio"
       Hardware: "USRP X310"

      IPAddress: "192.168.10.2"

    ClockSource: "internal"
     TimeSource: "internal"

       LOSource: "internal"
     LOExported: 0

Create a baseband transmitter object, specifying your radio object. Specify the Preload name-value argument as true to load the application onto the radio during object creation. Specify the RF properties during object creation.

bbtx = basebandTransmitter(radio,Preload=true, ...
    SampleRate=50e6,CenterFrequency=2.4e9, ...
    TransmitDataType="double")

bbtx = 
  basebandTransmitter with properties:

           RadioGain: 10
     CenterFrequency: 2.4000e+09
          SampleRate: 50000000
            Antennas: "RFA:TX/RX"
    TransmitDataType: "double"

Schedule the start time for the transmit operation to be 5 seconds in the future.

startTime = getRadioTime(radio) + 5

startTime = 
5.5661

Generate a random transmit waveform.

txWaveform = complex(randn(1000,1),randn(1000,1));

Transmit the generated waveform in a single shot with the radio associated with the baseband transmitter object.

transmit(bbtx,txWaveform,"once");

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 basebandTransmitter 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.

Version History

Introduced in R2022a

R2025a: Load application onto your radio during object creation

Specifying the Preload name-value argument as true now enables you to load the application onto your radio during object creation.

When Preload is not specified or set to false, which is the default behaviour, the application is loaded to hardware the first time you call the transmit function.

R2025a: Create basebandTransmitter object with radio object

You can now use a radio object as the radio input argument when you create a basebandTransmitter object.

R2025a: Specify transmit data type

You can now use the TransmitDataType property to specify the data type of the data that you transmit with the transmit function. This property configures the basebandTransmitter object with the transmit data type in advance of you calling the transmit function.

Set this property when you specify a StartTime in your call to the transmit function. This ensures that the radio time will not be reset. You must specify a waveform with the same data type in your call to the transmit function, or the data type you specify with this argument will be overwritten and the radio time will be reset.

R2025a: Transmit data at up to 500 MS/s with USRP X410

The basebandTransmitter object now supports the following master clock rates (MCRs) on USRP X410 radios:

• 491.52 MHz

• 500 MHz

To transmit data at sample rates equal to these MCRs, set the SampleRate property equal to one of these values and call the transmit function.