transmit

Transmit waveform over the air with an NI USRP radio device

Since R2024a

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Syntax

transmit(device,waveform,mode)
transmit(___,StartTime=startTime)

Description

transmit(device,waveform,mode) transmits the IQ waveform waveform to the air using the specified NI™ USRP™ radio device. The transmission mode mode specifies continuous or single-shot transmission. To stop a continuous transmission, call stopTransmission(device).

example

transmit(___,StartTime=startTime) schedules the transmission to start at the specified start time startTime. (since R2025a)

Examples

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This example uses:

Open Live Script

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

device = usrp("MyRadio");

Program the FPGA with your bitstream and configure the hardware interfaces.

programFPGA(device,"myBitstream.bit","myDeviceTree.dts");
Loading bitstream to FPGA...
Loading bitstream to FPGA is now complete.

describeFPGA(device,"ModelName_wthandoffinfo.mat");

Specify the number of samples in the transmit waveform and allocate memory in the PL DDR Buffer.

transmitLength = 1000;
device.TransmitAntennas = "DB0:RF0:TX/RX0";
device.TransmitDDRAllocation = transmitLength;

Connect to the radio and apply radio front end properties.

setup(device);

Generate random data to transmit.

wav = complex(randn(transmitLength,1),randn(transmitLength,1));

Scale the data so that the maximum real or complex value is 0.8.

wav = 0.8*(wav/max(max([abs(real(wav)),abs(imag(wav))])));

Scale the transmit data to complex int16.

txWaveform = int16(wav*double(intmax('int16')));

Transmit the generated waveform continuously.

transmit(device,txWaveform,"continuous");

Stop the continuous transmission after 5 seconds.

pause(5);
stopTransmission(device);

Input Arguments

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NI USRP radio device, specified as a usrp System object™.

IQ waveform to transmit, specified as one of these options:

  • Complex-valued column vector with even number of rows — Use this option to send an IQ waveform on a single transmit antenna.

  • Complex-valued matrix with even number of rows — Use this option to send IQ waveforms on multiple transmit antennas. The number of antennas specified by the TransmitAntennas property of the usrp object specified in the device input argument must match the number of matrix columns.

If you specify a waveform with a single or double data type, you must scale the transmit data sample values to the range [intmin('int16'),intmax('int16')].

The waveform length is limited by the TransmitDDRAllocation property of the usrp object specified in the device input argument.

Note

Some radios contain RF pipelines that can retain samples from the last transmitted signal. To ensure reliability when you set the transmission mode to "once", add redundant samples to the end of your waveform.

Data Types: int16 | single | double
Complex Number Support: Yes

Transmission mode, specified as one of these options:

  • "continuous" — The function transmits the waveform waveform continuously to the air by repeating the data samples until you call stopTransmission(device).

  • "once" — The function transmits the waveform waveform once in a single-shot transmission.

Data Types: string

Since R2025a

Start time for transmission, specified as a positive numeric scalar. To schedule a transmission to start at a future time, first get the current radio time in seconds, first use the getRadioTime function to get the current radio time in seconds. Then, specify the radio time at which you want to start transmitting data.

For more information about how to schedule transmit and receive operations, see Time-Synchronize Operations.

Example: getRadioTime(radio)+0.5 schedules the capture operation to start 500 milliseconds in the future.

Data Types: double

Version History

Introduced in R2024a

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See Also

Objects

Functions

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