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comm.SDRuTransmitter

Send data to USRP device

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Add-On Required: This feature requires the Communications Toolbox Support Package for USRP Radio add-on.

Description

The comm.SDRuTransmitter System object™ sends data to a USRP™ radio, enabling simulation and development for various software-defined radio applications; for USRP N3xx series and X series radios, see the Wireless Testbench™ documentation.

Use this object to communicate with a USRP radio on the same Ethernet subnetwork or via a USB connection. You can write a MATLAB® application that uses the System object, or generate code for the System object without connecting to a USRP radio.

This object accepts a column vector or matrix input signal from MATLAB and transmits signal and control data to a USRP radio using the universal hardware driver (UHD™) from Ettus Research™. The System object is a sink that sends the data it receives to a USRP radio.

To send data from a USRP radio device:

  1. Create the comm.SDRuTransmitter object and set its properties.

  2. Call the object as if it were a function.

To learn more about how System objects work, see What Are System Objects?.

Note

Starting in R2024a, the MathWorks® products and support packages you require to use this System object depend on your radio device.

Radio DeviceRequired MathWorks ProductsSupport Package Installation

USRP2™

USRP N200, N210

USRP B200, B210

Communications Toolbox™ Support Package for USRP RadioInstall Communications Toolbox Support Package for USRP Radio

USRP N300, N310, N320, N321

USRP X300, X310

Wireless Testbench

Wireless Testbench Support Package for NI™ USRP Radios

Install Support Package for NI USRP Radios (Wireless Testbench)

For details on how to use this System object with a radio device supported by Wireless Testbench Support Package for NI USRP Radios, see comm.SDRuTransmitter (Wireless Testbench).

Creation

Syntax

tx = comm.SDRuTransmitter
tx = comm.SDRuTransmitter(address)
tx = comm.SDRuTransmitter(___,Name = Value)

Description

tx = comm.SDRuTransmitter creates a default SDRu transmitter System object.

example

tx = comm.SDRuTransmitter(address) sets the IPAddress property to the address of the connected USRP device.

example

tx = comm.SDRuTransmitter(___,Name = Value) sets Properties using one or more name-value pairs in addition to any input argument combination from previous syntaxes. For example, CenterFrequency = 5e6 specifies the center frequency as 5 MHz.

example

Properties

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Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

Connection Properties

Model number of the radio, specified as one of these values.

  • "N200/N210/USRP2"

  • "B200"

  • "B210"

Data Types: char | string

IP address of the USRP radio, specified as a character vector or string scalar containing dotted-quad values. When you specify more than one IP address, you must separate each address using commas or spaces.

This value must match the physical IP address of the radio device assigned during hardware setup. For more information, see Guided USRP Radio Support Package Hardware Setup. If you configure the radio device with an IP address other than the default, update this property accordingly.

To find the logical network location of all connected USRP radios, use the findsdru function.

Example: "192.168.10.2, 192.168.10.5" or "192.168.10.2 192.168.10.5" specifies IP addresses for two radio devices.

Dependencies

To enable this property, set Platform to "N200/N210/USRP2".

Data Types: char | string

Serial number of the radio hardware, specified as a character vector or string scalar.

This property must match the serial number of the radio hardware assigned during hardware setup. For more information, see Guided USRP Radio Support Package Hardware Setup. If you configure the radio hardware with a serial number other than the default, update this property accordingly.

Dependencies

To enable this property, set Platform to "B200" or "B210".

Data Types: char | string

Configuration Properties

Channel mapping for the radio or bundled radios, specified as a positive scalar or a row vector of positive values. This table shows the valid values for each radio platform.

Platform Property Value ChannelMapping Property Value

"N200/N210/USRP2"

1-by-N row vector, where N is the number of IP addresses in the IPAddress property

"B200"

1

"B210"

1, 2, or [1 2]

When IPAddress contains multiple IP addresses, the channels defined by ChannelMapping are ordered first by the order in which the IP addresses appear in the list and then by the channel order within the same radio.

For example, if the Platform is "N210" and IPAddress is "192.168.20.2, 192.168.10.3", then the ChannelMapping must be [1 2]. Channel 1 of the bundled radio refer to channel 1 of the radio with IP address 192.168.20.2. Channel 2 of the bundled radio refer to channel 1 of the radio with IP address 192.168.10.3.

Data Types: double

Center frequency in Hz, specified as a nonnegative scalar or a row vector of nonnegative values. The valid range of values for this property depends on the RF daughter card of the USRP device.

Specify the center frequency value according to these conditions.

  • For a single-input single output (SISO) configuration, specify the value for the center frequency as a nonnegative scalar.

  • For multiple-input multiple output (MIMO) configurations that use the same center frequency, specify the center frequency as a nonnegative scalar. The object sets the center frequency for each channel by using scalar expansion.

  • For MIMO configurations that use different center frequencies, specify the values in a row vector (for example, [70e6 100e6]). The object applies the ith element of the vector to the ith channel that you specify in the ChannelMapping property.

    Note

    • For a MIMO scenario, the center frequency for a B210 radio must be a scalar. You cannot specify the frequencies as a vector.

Tunable: Yes

Data Types: double

LO offset frequency in Hz, specified as a scalar or row vector. The valid range of this property depends on the RF daughterboard of the USRP device.

The LO offset does not affect the transmitted center frequency. However, the LO offset does affect the intermediate center frequency in the USRP radio, as shown in the diagram.

Impact of LO frequency on the intermediate center frequency of the USRP radio

In this diagram:

  • f center is the center frequency that you set in the System object.

  • f LO offset is the LO offset frequency.

Use this property to move the center frequency away from interference or harmonics generated by the USRP radio.

To change the LO offset, specify the value according to these conditions.

  • For a SISO configuration, specify the LO offset as a scalar.

  • For MIMO configurations, the LO offset must be zero. This restriction is due to a UHD limitation. In this case, you can specify the LO offset as 0.

Tunable: Yes

Data Types: double

Overall gain in dB for the USRP radio receiver data path, including analog and digital components, specified as a scalar or row vector. The valid range of this property depends on the RF daughterboard of the USRP device.

Specify the gain according to these conditions.

  • For a SISO configuration, specify the gain as a scalar.

  • For MIMO configurations that use the same gain value, specify the gain as a scalar. The gain is set by scalar expansion.

  • For MIMO configurations that use different gains, specify the values in a row vector (for example, [32 30]). The object applies the ith element of the vector to the ith channel that you specify in the ChannelMapping property.

Tunable: Yes

Data Types: double

Pulse per second (PPS) signal source, specified one of these values.

  • "Internal" — Use the internal PPS signal of the USRP radio.

  • "External" — Use the PPS signal from an external signal generator.

  • "GPSDO" — Use the PPS signal from a global positioning system disciplined oscillator (GPSDO).

To synchronize the time for all the channels of the bundled radios, you can:

  • Provide a common external PPS signal to all of the bundled radios and set this property to "External".

  • Use the PPS signal from each GPSDO that is available on the USRP radio by setting this property to "GPSDO".

To get the lock status of the GPSDO to the GPS constellation, set this property to "GPSDO" and use the gpsLockedStatus function.

Data Types: char | string

Option to enforce GPS time synchronization, specified as one of these values.

  • 1 (true) — Synchronize the USRP radio time to the valid global positioning system (GPS) time if the GPSDO is locked to the GPS constellation at the beginning of the transmit or receive operation.

  • 0 (false) — Set the USRP radio time to the GPSDO time if the GPSDO is not locked to the GPS constellation at the beginning of the transmit or receive operation.

Each time you call the System object, it checks the lock status of the GPSDO. When the GPSDO is locked to the GPS constellation, the System object sets the USRP radio time to the valid GPS time.

Dependencies

To enable this property, set the PPSSource property to "GPSDO".

Data Types: logical

Clock source, specified as one of these values.

  • "Internal" — Use the internal clock signal of the USRP radio.

  • "External" — Use the 10 MHz clock signal from an external clock generator.

  • "GPSDO" — Use the 10 MHz clock signal from a GPSDO.

For B-series radios, the external clock port has the label 10 MHz.For N2xx series and USRP2 radios, the external clock port has the label REF IN.

To synchronize the frequency for all the channels of the bundled radios, you can:

  • Provide a common external 10 MHz clock signal to all of the bundled radios and set this property to "External".

  • Provide a 10 MHz clock signal from each GPSDO to the corresponding radio and set this property to "GPSDO".

To synchronize the frequency for all channels, set this property to "GPSDO" and then verify that the outputs of the referenceLockedStatus and gpsLockedStatus functions both return an output of 1.

Data Types: char | string

Master clock rate in Hz, specified as a positive scalar. The master clock rate is the analog to digital (A/D) and digital to analog (D/A) clock rate. The valid range of values for this property depends on the connected radio platform.

Platform Property ValueMasterClockRate Property Value (in Hz)

"N200/N210/USRP2"

100e6 (read-only)

"B200" or "B210"

Scalar in the range from 5e6 to 61.44e6.

When you use a B210 radio with multiple channels, the clock rate must be less than or equal to 30.72e6. This restriction is a hardware limitation for two-channel operations on B210 radios.

The default value is 32e6.

Data Types: double

Interpolation factor for the SDRu transmitter, specified as an integer in the range [1,1024] with restrictions that depend on the radio you use.

InterpolationFactor Property ValueB-SeriesN2xx-Series

1

Valid

Not valid

2

Valid

Valid only when you set the TransportDataType property to "int8".

3

Valid

Not valid

Odd integer from 4 to 128

Valid

Valid

Even integer from 4 to 128

Valid

Valid

Even integer from 128 to 256

Valid

Valid

Integer multiple of 4 from 256 to 512

Valid

Valid

Integer multiple of 8 from 512 to 1024

Not valid

Not valid

The radio uses the interpolation factor when it upconverts the complex baseband signal to an intermediate frequency (IF) signal.

Data Types: double

Option to enable timed transmission and reception, specified as a numeric or logical value of 1 (true) or 0 (false). When you set this property to 1 (true), you can:

  • Transmit or receive after the time specified in the TriggerTime property.

  • Transmit or receive at the specified GPS time in the TriggerTime property if you set the PPSSource property to "GPSDO".

  • Simultaneously transmit and receive after the time specified in the TriggerTime property.

Data Types: logical

Trigger time in seconds, specified as a nonnegative scalar. Specify the trigger time after which the radio starts transmitting or receiving data. The TriggerTime value must be greater than the current USRP radio time. Use the getRadioTime function to get the current USRP radio time.

Note

After you call the getRadioTime function, call the System object before releasing it to ensure that the object is released properly.

When you set the PPSSource property to "GPSDO", specify the TriggerTime property as the exact GPS time in seconds at which you want the radio to start transmitting or receiving data.

Note

For AD936x-based USRP B2xx series radios, you can expect a consistent delay between the specified trigger time and the start of transmission or reception.

Dependencies

To enable this property, set the EnableTriggerTime property to true.

Data Types: double

Since R2024b

Option to enable MIMO cable synchronization, specified as a numeric or logical value of 1 (true) or 0 (false). When you set this property to 1 (true), you can:

  • Synchronize two USRP N200/N210 radios.

  • Transmit or receive frequency, phase, and time synchronized data across multiple channels.

  • Share Ethernet across two N200/N210 USRP radios.

To build larger MIMO systems, up to 16 x 16, set the PPSSource and ClockSource property to either "External" or "GPSDO".

Dependencies

To enable this property, set the Platform to "N200/N210/USRP2".

Data Types: logical

Data Properties

Transport data type, specified as one of these values:

  • "int16" — Use 16-bit transport to achieve higher precision.

  • "int8" — Use 8-bit transport to achieve a transport data rate that is approximately two times faster than 16-bit transport. The quantization step is 256 times larger than 16-bit transport.

The default transport data type assigns the first 16 bits to the in-phase (I) component and the remaining 16 bits to the quadrature (Q) component, resulting in 32 bits for each complex sample of transport data.

Data Types: char | string

Option to enable burst mode, specified as a numeric or logical value of 1 (true) or 0 (false). To produce a set of contiguous frames without an overrun or underrun to the radio, set this property to 1 (true). Enable burst mode to simulate models that cannot run in real time.

When you enable burst mode, specify the number of frames in a burst by using the NumFramesInBurst property. For more information, see Detect Underruns and Overruns.

Data Types: logical

Number of frames in a contiguous burst, specified as a nonnegative integer.

Dependencies

To enable this property, set EnableBurstMode to 1 (true).

Data Types: double

Usage

Syntax

tx(data)
underrun = tx(data)

Description

tx(data) sends data to a USRP device associated with the comm.SDRuTransmitter System object tx.

example

underrun = tx(data) returns an integer value that indicates data discontinuity for the input data data.

example

Input Arguments

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Data to transmit, specified as a complex column vector or complex matrix. The number of columns in the matrix depends on the number of channels in use, which you specify in the property. For a single-channel radio, this input must be a column vector. For a multichannel radio, this input must be a matrix. Each column in this matrix corresponds to complex data sent on one channel.

The complex data in the transmitted signal must be one of these data types:

  • 16-bit signed integers — Complex values in the range [–32768, 32767]

  • Single-precision floating point — Complex values in the range [–1, 1]

  • Double-precision floating point — Complex values in the range [–1, 1]

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

Output Arguments

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Data discontinuity flag, returned as one of these values.

  • 0 — The object does not detect underrun.

  • 1 — The object detects an underrun. The input data does not represent contiguous data from the host to the USRP radio.

Although the value of this output does not represent the actual number of packets dropped, as this value increases, the farther your execution of the object is from achieving real-time performance. You can use this value as a diagnostic tool to determine real-time execution of the object. For more information, see Detect Underruns and Overruns.

Data Types: uint32

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

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infoCurrent USRP radio settings
referenceLockedStatusLock status of USRP radio to 10 MHz clock signal
gpsLockedStatusLock status of GPSDO to GPS constellation
getRadioTimeGet current USRP radio time
stepRun System object algorithm
releaseRelease resources and allow changes to System object property values and input characteristics
resetReset internal states of System object

Examples

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This example uses:

Open Live Script

Configure a B210 radio with serial number 30F59A1. Set the radio to transmit at 2.5 GHz with an interpolation factor of 256.

Create an SDRu Transmitter System object for data transmission.

tx = comm.SDRuTransmitter(...
              Platform = "B210", ...
              SerialNum = "30F59A1", ...
              CenterFrequency = 2.5e9, ...
              InterpolationFactor = 256);

Create a DPSK modulator as the data source using comm.DPSKModulator System object. Inside a for-loop, transmit the data using the tx System object.

mod = comm.DPSKModulator(BitInput = true);
    for counter = 1:20
      data = randi([0 1],30,1);
      modSignal = mod(data);
      tx(modSignal);
    end

This example uses:

Open Live Script

Use the info object function to get information from a connected B210 radio. The function shows the actual values for the radio. These values can vary slightly from the values specified in the object.

radio = comm.SDRuTransmitter(Platform ="B210",SerialNum ="31B92DD");
radio.CenterFrequency = 912.3456e6;
radio.LocalOscillatorOffset = 1000;
radio.Gain = 8.3;
radio.MasterClockRate = 10.56789e6;
radio.InterpolationFactor = 510;
info(radio)                   
ans = struct with fields:
                    Mboard: 'B210'
                  RXSubdev: 'FE-RX2'
                  TXSubdev: 'FE-TX2'
    MinimumCenterFrequency: 4.4716e+07
    MaximumCenterFrequency: 6.0053e+09
               MinimumGain: 0
               MaximumGain: 89.7500
                  GainStep: 0.2500
           CenterFrequency: 9.1235e+08
     LocalOscillatorOffset: -999.7189
                      Gain: 8.2500
           MasterClockRate: 1.0568e+07
       InterpolationFactor: 512
        BasebandSampleRate: 2.0640e+04

This example uses:

Open Live Script

Configure an B210 radio with serial number 30F59A1. Set the radio to transmit at 2.5 GHz with an interpolation factor of 125 and master clock rate of 56 MHz.

Create an SDRu Transmitter System object for data transmission.

tx = comm.SDRuTransmitter(...
               Platform = "B210", ...
              SerialNum = "30F59A1", ...
              CenterFrequency = 2.5e9, ...
              InterpolationFactor = 125, ...
              MasterClockRate = 56e6);

Create a DPSK modulator as the data source using comm.DPSKModulator System object.

modulator = comm.DPSKModulator(BitInput = true);

Inside a for-loop, transmit the data using the tx System object and return underrun output argument. Display messages when the transmitter indicates an underrun with data loss.

for frame = 1:20000
      data = randi([0 1], 30, 1);
      modSignal = modulator(data);
      underrun = tx(modSignal);
      if underrun~=0
          msg = ['Underrun detected in frame # ', int2str(frame)];
      end
end
    release(tx)

This example uses:

Open Live Script

Configure a B200 radio with serial number set to 30FD838. Set the radio to transmit at 2.5 GHz with an interpolation factor of 125 and master clock rate of 56 MHz. Enable burst-mode buffering to overcome underruns. Set the number of frames in a burst to 20.

Create an SDRu Transmitter System object for data transmission.

tx = comm.SDRuTransmitter(...
               Platform = "B200", ...
              SerialNum = "30FD838", ...
              CenterFrequency = 2.5e9, ...
              InterpolationFactor = 125, ...
              MasterClockRate = 56e6);
tx.EnableBurstMode = true;
tx.NumFramesInBurst = 20;

Create a DPSK modulator as the data source using comm.DPSKModulator System object.

modulator = comm.DPSKModulator(BitInput = true);
data = randi([0 1],37500,1);
modSignal = modulator(data);

Inside a for loop, transmit the data using the tx System object.

numFrames = 100;
for frame = 1:numFrames
    underrun = tx(modSignal);
end
no tx ack

release(tx)

This example uses:

Open Live Script

This example shows how to transmit a signal at GPS trigger time using a USRP™ radio.

Generate a sine wave with a frequency of 30 kHz.

sinewave = dsp.SineWave(1,30e3); 
sinewave.SampleRate = 100e6/100; 
sinewave.SamplesPerFrame = 1e4; 
sinewave.OutputDataType = 'double'; 
sinewave.ComplexOutput = true;
data = sinewave();

Create an SDRu transmitter System object tx to transmit the sine wave. Set the serial number to 3136D5F. To transmit the signal at the GPS time, set the PPS signal source to the PPS signal from a GPSDO, clock source to GPSDO, and enable GPS time synchronization.

Fs = 15e6; % Sample Rate
interpDecim  = 2; % Interpolation or Decimation factor of interest
masterClkRate = interpDecim*Fs; % Master clock rate

txGain = 45;
txChannelMapping = 1;

tx = comm.SDRuTransmitter(Platform = "B210", SerialNum='3136D5F', ...
    PPSSource = "GPSDO", EnforceGPSTimeSync=true, ...
    ClockSource= "GPSDO", MasterClockRate=masterClkRate,...
    InterpolationFactor=interpDecim, ChannelMapping=txChannelMapping,...
    Gain=txGain, CenterFrequency=3.21e9);

To enable the transmitter to start transmitting at the GPS time, set the EnableTimeTrigger to 1 or true. Add a time delay to the GPS trigger time.

time_now = datetime('now');
trigger_time = time_now + hours(0) + minutes(0) + seconds(10);  % Provide the time delay
trigger_time
trigger_time = datetime
   20-Jun-2023 17:15:09


trigger_time.TimeZone = 'Asia/Calcutta';
usrp_trigger_time = posixtime(trigger_time);  % Provide as input to trigger time
tx.EnableTimeTrigger = true;
tx.TriggerTime = usrp_trigger_time;

Transmit the signal.

numFrames = 100;
for i=1:numFrames
    txdata = data;
    underrun = tx(txdata);
end
USRP time synchronized to GPS time

Release the transmitter System object.

release(tx);

This example uses:

Open Live Script

This example shows how to use time triggering with a B210 radio to calculate the range of a target using frequency-modulated continuous wave (FMCW) radar waveform.

Generate FMCW radar waveform

Set the sample rate, interpolation factor or decimation factor, and master clock rate.

Fs = 30e6; % Sample Rate
interpDecim  = 1; % Interpolation or Decimation factor of interest
masterClkRate = interpDecim*Fs; % Master clock rate

Set the sweep time and sweep bandwidth. Divide the sweep bandwidth by the sweep time to obtain the slope.

% Specify sweep time and sweep bandwidth
sweepTime = 1e-3;
sweepBW = 15e6;
slope = sweepBW/sweepTime;

Use the bw2rangeres (Phased Array System Toolbox) function to calculate the range resolution corresponding to the signal bandwidth and the time2range (Phased Array System Toolbox) function to calculate the maximum range the signal propagates during sweepTime/6 seconds.

% Calculate the range resolution and maximum range
rangeRes = bw2rangeres(sweepBW);
fprintf('Range resolution = %d',rangeRes)
Range resolution = 9.993082e+00

maxRange  = time2range(sweepTime/6);
fprintf('Maximum range = %d',maxRange)
Maximum range = 2.498270e+04

Create a phased.FMCWWaveform (Phased Array System Toolbox) object.

hwav = phased.FMCWWaveform(SampleRate=Fs, SweepTime=sweepTime,...
                           SweepBandwidth=sweepBW, OutputFormat='Sweeps', NumSweeps=1);

Generate the FMCW radar waveform.

xRef =  hwav();
NumSamps = length(xRef);

Set Transmitter Properties

Create a comm.SDRuTransmitter object.

txGain = 45;
txChannelMapping = 1;

tx = comm.SDRuTransmitter(Platform = "B210", SerialNum='3136D5F', ...
    PPSSource = "Internal", ...
    ClockSource= "Internal", ...
    MasterClockRate=masterClkRate,...
    InterpolationFactor=interpDecim,...
    ChannelMapping=txChannelMapping,...
    Gain=txGain, CenterFrequency=3.21e9);

Set the EnableTimeTrigger property for the transmitter object as true and set the desired trigger time for transmission.

% Provide trigger time
usrpTriggerTime = 12;

tx.EnableTimeTrigger = true;
tx.TriggerTime = usrpTriggerTime;

Set Receiver Properties

Create a comm.SDRuReceiver object.

rxGain = 45;
rxChannelMapping = 2;

rx = comm.SDRuReceiver(Platform = "B210", SerialNum='3136D5F', ...
    PPSSource = "Internal", ...
    ClockSource= "Internal", ...
    MasterClockRate=masterClkRate,...
    DecimationFactor=interpDecim, ...
    SamplesPerFrame = NumSamps,...
    OutputDataType="double",...
    ChannelMapping=rxChannelMapping, Gain=rxGain,CenterFrequency=3.21e9);

Set the EnableTimeTrigger property for the receiver object as true and set the desired trigger time for reception.

rx.EnableTimeTrigger = true;
rx.TriggerTime = usrpTriggerTime; % Same as tx trigger time

Set Timescope and Spectrumscope properties

Set the spectrumAnalyzer and timescope properties.

decimfact = 4;
spectrumScope1 = spectrumAnalyzer(SampleRate=Fs);
spectrumScope2 = spectrumAnalyzer(SampleRate=Fs/decimfact);
spectrumScope3 = spectrumAnalyzer(SampleRate=Fs/decimfact);

spectrumScope2.PeakFinder.Enabled = true;
spectrumScope3.PeakFinder.Enabled = true;

% Set the number of frames you would like to process
numFrames = 1;
frameTime = NumSamps/Fs;
timeSpan = numFrames*frameTime;

timeScope = timescope(SampleRate=Fs, ...
    TimeSpanSource="property", ...
    TimeSpan = timeSpan, ...
    LayoutDimensions=[2,1]);

Transmit and Receive FMCW Radar Waveform

Transmit the FMCW radar waveform and receive the reflected FMCW radar waveform from the target after the specified trigger time.

yBuff = zeros(numFrames*NumSamps,1);
xRefBuff = zeros(numFrames*NumSamps,1);

for i=1:numFrames
    txData = hwav();
    underrun = tx(txData);
    if underrun==0
        disp('Transmission successful')
    else
        disp('Transmission failed')
    end
    % Receive the signal

    [rxdata, ~,overflow, rx_time_stamp] = rx();
    if overflow==0
        disp('Reception successful')
    else
        disp('Reception failed')
    end
    yDechirp = dechirp(rxdata,txData);
    yBuff((i-1)*NumSamps+1:i*NumSamps,1) = yDechirp;
   
    xRefBuff((i-1)*NumSamps+1:i*NumSamps,1) = txData;
   
    spectrumScope1(txData)
    spectrumScope2(decimate(yDechirp,decimfact))
end
Transmission successful

Reception successful

fmcw1.png

fmcw2.pngCalculate the Range of the Target Based On the Beat Frequency

To calculate the beat frequency, use spectrum analyzer to find the peak frequency.

spectrumData1 = getMeasurementsData(spectrumScope2);
beatFreq = spectrumData1.PeakFinder.Frequency(1);
c = 3e8; % Speed of light
beatFreqRange = beat2range(beatFreq,slope,c);
fprintf('Range of the target based on beat frequency = %d',beatFreqRange)
Range of the target based on beat frequency = 8.056641e+02

timeScope(real(xRefBuff),real(yBuff));

fmcw3.pngRelease the timescope, spectrumscope, transmitter and receiver System objects.

release(timeScope);
release(spectrumScope1);
release(spectrumScope2);
release(rx);
release(tx);

Since R2024b

This example uses:

Open Live Script

This example shows how to synchronize two N2xx series USRP™ radios using a MIMO cable for transmission and reception.

Connect two N2xx series radios using a MIMO cable. Connect the transmitter output to a power splitter and then connect each output of the splitter to the receive channels of the N2xx radios.

Run the transmitter_mimo.m script in a different MATLAB® session to start transmission.

Set the sample rate and master clock rate.

radioFrontEndSampleRate = 1e6;
radioMasterClockRate = 100e6;

Calculate the decimation factor by dividing the master clock rate by the sample rate.

decimationFactor = radioMasterClockRate/radioFrontEndSampleRate;

Set the frame length.

frameLength = 1e4;

Create a receiver System object.

rx = comm.SDRuReceiver(Platform = "N200/N210/USRP2",...
                       IPAddress ="192.168.10.2,192.168.10.3",...
                       CenterFrequency = 2e9,Gain = 30,...
                       SamplesPerFrame = frameLength,...
                       DecimationFactor = decimationFactor,...
                       ChannelMapping = [1,2],...
                       OutputDataType = "double");

Enable MIMO cable synchronization.

rx.EnableMIMOCableSync = true;

Set the frame duration.

frameDuration = frameLength /radioFrontEndSampleRate ;

Create a spectrumAnalyzer System object to visualize the captured signal.

spectrumScope = spectrumAnalyzer(SampleRate = radioFrontEndSampleRate);

Create a timescope System object to display the captured signal in time domain.

timeScope = timescope(TimeSpan = 4/10e3,SampleRate = radioFrontEndSampleRate);
timeScope.YLimits=[-0.5, 0.5];

Receive the signal.

time = 0;
disp("Reception started");
Reception started

while time<10
    recvData = rx();
    % Compute cross-correlation
    [c, lags] = xcorr(recvData(:,2), recvData(:,1));
    % Find the lag with maximum correlation
    [~, I] = max(abs(c));
    timeOffset = lags(I)/radioFrontEndSampleRate; % Convert lag to time
    freqOfFirst = fft( recvData(:,1));
    freqOfSecond = fft( recvData(:,2));
    spectrumScope(recvData);
    timeScope(recvData);
    time = time+frameDuration;
end

Release the receiver System object.

release(rx);

This example shows how to generate a MEX file called sdruTransmitMex from the function sdruTransmitData. When you run this MEX file, the code shows a performance improvement and no underruns for data frames that contain 10000 samples.

Create a function that configures a comm.SDRuTransmitter System object. Generate a sine wave of 100 kHz for transmission. The function calculates the sample rate by using the master clock rate and interpolation factor. Set the frame duration for the radio to transmit sine wave based on the samples per frame and sample rate. Display a message when transmission starts. Inside a for-loop, transmit the data using the tx System object and return the underrun as an output argument.

function[transmitTime,underrunCount] = sdruTransmitData()
       duration = 10;
       samplesPerFrame = 1e4;
       masterClockRate = 20e6;
       interpolationFactor = 1;
 
       sampleRate = masterClockRate/interp;
       frameDuration = samplesPerFrame/sampleRate;
       iterations = duration/frameDuration;

       sinGen = dsp.SineWave(Frequency =100e3, SampleRate = sampleRate, ...
                       SamplesPerFrame = samplesPerFrame, ...
                       ComplexOutput = true);
       data = sinGen();
       tx = comm.SDRuTransmitter(Platform = "B210",SerialNum = "30F59A1", ...
                          CenterFrequency = 2.45e9, ...
                          MasterClockRate = masterClockRate, ...
                          InterpolationFactor = interpolationFactor);
       tx(data);
       disp("Started Transmission...");
       underrunCount = 0;
       tic
       for i = 1:iterations
           underrun = tx(data);
           if underrun
              underrunCount = underrunCount + 1;
           end
       end
       transmitTime = toc;
       release(tx);
end

Generate a MEX file with the name sdruTransmitMex from the function sdruTransmitData.

codegen sdruTransmitData -o sdruTransmitMex;

Run this MEX file to transmit data using the generated MEX and observe the transmission time and number of underruns.

[transmitTime,underrunCount] = sdruTransmitMex()

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Extended Capabilities

Version History

Introduced in R2011b

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