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comm.SDRuReceiver

Receive data from USRP device

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Description

The SDRuReceiver System object™ receives data from a Universal Software Radio Peripheral (USRP™) hardware device, enabling simulation and development for software-defined radio applications. Use this object to communicate with a USRP board on the same Ethernet subnetwork or a via a USB connection. You can write a MATLAB® application that uses the System object, or you can generate code for the System object without connecting to a USRP radio.

This object receives signal and control data from a USRP board using the universal hardware driver (UHD™) from Ettus Research™. The System object receives data from a USRP board and outputs a column vector or matrix signal with fixed number of rows.

Note

Starting in R2016b, instead of using the step method to perform the operation defined by the System object, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

To receive data from a USRP device:

  1. Create the comm.SDRuReceiver 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?.

Creation

Syntax

rx = comm.SDRuReceiver
rx = comm.SDRuReceiver(address)
rx = comm.SDRuReceiver(___,Name = Value)

Description

example

rx = comm.SDRuReceiver creates a default SDRu receiver System object.

example

rx = comm.SDRuReceiver(address) sets the IPAddress property to address of the connected USRP device.

example

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

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"

  • "N300"

  • "N310"

  • "N320/N321"

  • "B200"

  • "B210"

  • "X300"

  • "X310"

Data Types: char | string

IP address of the USRP device, 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 by commas or spaces.

This value must match the physical IP address 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 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 devices.

Dependencies

To enable this property, set Platform to "N200/N210/USRP2", "N300", "N310", "N320/N321", "X300", or "X310".

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

Option to enable the TwinRX daughterboard, specified as a numeric or logical 0 (false) or 1 (true). To enable the TwinRX daughterboard on an X-series radio, set IsTwinRXDaughterboard to 1 (true).

When you enable the TwinRX daughterboard, you can use the EnableTwinRXPhaseSynchronization property to enable phase synchronization between channels of the TwinRX daughterboard.

Dependencies

To enable this property, set the Platform property to "X300" or "X310".

Data Types: logical

Configuration Properties

Option to enable phase synchronization between channels of the TwinRX daughterboard, specified as a numeric or logical 0 (false) or 1 (true). When you set this property to 1 (true), the TwinRX daughterboard provides phase synchronization between all the channels. In this case, the value of the CenterFrequency property must be the same for all the channels.

Note

The local oscillator (LO) source on channel 1 is the master source that drives the other LOs of the TwinRx daughterboard channels.

To share LOs between two TwinRx daughterboards, attach the four MMCX RA male cables on one daughterboard to the MMCX RA male cables on the other daughterboard by crossing the cables between the two daughterboards. Make these cable connections.

  • J1 to J2

  • J2 to J1

  • J3 to J4

  • J4 to J3

This figure shows the connections between the TwinRx daughterboards.

Crisscross connection of MMCX RA male cables between two TwinRX daughterboards

Dependencies

To enable this property, set the Platform property to "X300" or "X310" and IsTwinRXDaughterboard property to 1 (true).

Data Types: logical

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

"N300"

  • When IPAddress contains one IP address, specify this property as 1, 2, or [1 2].

  • When IPAddress contains N IP addresses, specify this property as a 1-by-2N row vector.

"N310"

  • When IPAddress contains one IP address, specify this property as one-, two-, three-, or four-element row vector of channel numbers from the set {1, 2, 3, 4}.

  • When IPAddress contains N IP addresses, specify this property as a 1-by-4N row vector.

"N320/N321"

  • When IPAddress contains one IP address, specify this property as 1, 2, or [1 2].

  • When IPAddress contains N IP addresses, specify this property as a 1-by-2N row vector.

"B200"

1

"B210"

1, 2, or [1 2]

"X300" or "X310" when the IsTwinRXDaughterboard property is 0 (false)

  • When IPAddress contains one IP address, specify this property as 1, 2, or [1 2]

  • When IPAddress contains N IP addresses, specify the property as a 1-by-2N row vector.

"X300" or "X310" when two TwinRX daughterboards are connected and the IsTwinRXDaughterboard property is 1 (true)

When the EnableTwinRXPhaseSynchronization property is 0 (false), specify this property as one of these values.

  • [N M], where N and M are distinct integers from 1 to 4 — Channels N and M are in use.

  • [N M P], where N, M, and P are distinct integers from 1 to 4 — Channels N, M, and P are in use.

  • [1 2 3 4]

When the EnableTwinRXPhaseSynchronization property is 1 (true), specify this property as 1, [1 2], [1 2 3], or [1 2 3 4].

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 Platform is "X300" and IPAddress is "192.168.20.2, 192.168.10.3", then ChannelMapping must be [1 2 3 4]. Channels 1 and 2 of the bundled radio refer to channels 1 and 2 of the radio with IP address 192.168.20.2, respectively. Channels 3 and 4 of the bundled radio refer to channels 1 and 2 of the radio with IP address 192.168.10.3., respectively.

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.

When you set the IsTwinRXDaughterboard property to 0 (false), specify the 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 center frequency is set by scalar expansion.

  • For multiple-input multiple output (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 B210 and N300 radios must be a scalar. You cannot specify the frequencies as a vector.

    • The channels corresponding to the same RF daughterboard of an N310 radio must have the same center frequency.

When you set the IsTwinRXDaughterboard property to 1 (true), specify the center frequency according to these conditions.

  • To tune all channels to the same frequency, specify the center frequency as a scalar and the EnableTwinRXPhaseSynchronization property as 1 (true).

  • To tune the channels to different frequencies, specify the center frequency as a row vector. Each value in the row vector specifies the frequency of the corresponding channel. Set the EnableTwinRXPhaseSynchronization property to 0 (false).

Note

When you set IsTwinRXDaughterboard and EnableTwinRXPhaseSynchronization to 1 (true), the LO source on channel 1 is the master source that drives the other LOs of the TwinRX daughterboard channels. In this case, the CenterFrequency property value must be the same for all channels of the TwinRX daughterboard.

For more information, see EnableTwinRXPhaseSynchronization.

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 received center frequency. However, the LO offset does affect the intermediate center frequency in the USRP hardware, as this diagram shows.

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

In this diagram:

  • f RF is the received RF frequency.

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

  • f LO offset is the LO offset frequency.

  • Ideally, fRF - fcenter = 0.

To move the center frequency away from interference or harmonics generated by the USRP hardware, use this property.

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 hardware 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 N3xx series, N2xx series, USRP2™, and X-series 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)

"N300" or "N310"

122.88e6, 125e6 (default), or 153.6e6

"N320/N321"

200e6 (default), 245.76e6, or 250e6

"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.

"X300" or "X310"

184.32e6 or 200e6 (default)

Dependencies

To enable this property, set Platform to "N300", "N310", "N320/N321", "B200", "B210", "X300", or "X310".

Data Types: double

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

DecimationFactor Property ValueB-SeriesN2xx-SeriesN3xx-SeriesX-Series

1

Valid

Not valid

Valid

Not valid when connected with TwinRX daughterboard

2

Valid

Valid only when you set the TransportDataTypeproperty to int8.

Valid

Valid

3

Valid

Not valid

Valid

Valid

Odd integer from 4 to 128

Valid

Valid

Not valid

Valid

Even integer in the range [4,256]

Valid

Valid

Valid

Valid

Integer multiple of 4 in the range [256,512]

Valid

Valid

Valid

Valid

Integer multiple of 8 in the range [512,1024]

Not valid

Not valid

Valid

Valid

The radio uses the decimation factor when it downconverts the intermediate frequency (IF) signal to a complex baseband 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 B2xx and N3xx series USRP 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

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 remaining16 bits to the quadrature (Q) component, resulting in 32 bits for each complex sample of transport data.

Data Types: char | string

Data type of the output signal, specified as one of these values.

  • "Same as transport data type" — Set the output data type to the same as the transport data type: either int8 or int16.

    • When the transport data type is int8, the output values are raw 8-bit I and Q samples from the board in the range [–128, 127].

    • When the transport data type is int16, the output values are raw 16-bit I and Q samples from the board in the range [–32 768 32 767].

  • "single" — Specify single-precision floating point values scaled to the range [–1, 1].

  • "double" — Specify double-precision floating point values scaled to the range [–1, 1].

Data Types: char | string
Complex Number Support: Yes

Number of samples per frame of the output signal, specified as a positive integer. This value optimally uses the underlying Ethernet packets, which have a size of 1500 8-bit bytes.

Note

Starting in R2021b, the limitation on setting the SamplesPerFrame property to a maximum value of 375000 is removed. You can set this property to any positive integer value.

Data Types: double

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

data = rx()
[data,dataLen] = rx()
[data,dataLen,overrun] = rx()
[data,dataLen,overrun,timeStamps] = rx()

Description

example

data = rx() receives data from a USRP device associated with the comm.SDRuReceiver System object, rx.

[data,dataLen] = rx() also returns dataLen, which indicates whether the object receives valid data from the radio hardware.

example

[data,dataLen,overrun] = rx() also returns an integer value that indicates data discontinuity. If overrun is equal to or greater than 1, then data does not represent contiguous data.

example

[data,dataLen,overrun,timeStamps] = rx() also returns the timestamp of each received sample from a USRP device.

Note

Starting in R2021b, the comm.SDRuReceiver System object returns valid data. You do not require conditional execution for any downstream processing based on the presence of valid data. For example, data = rx() always returns valid data.

Output Arguments

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Output signal, returned as a column vector or matrix. For a single-channel radio, this output is a column vector. For a multichannel radio, this output is a matrix. Each column in this matrix corresponds to a complex data received on one channel.

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

Data length, returned as a nonnegative integer. The value of this output is the number of samples received from USRP radio.

Data Types: double

Data discontinuity flag, returned as one of these values.

  • 0 — The object does not detect an overrun.

  • 1 — The object detects an overrun. The output data does not represent contiguous data that is transmitted from the USRP radio to the host.

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

Timestamp of each received sample, returned as a column vector. The length of this output equals the length of received data.

  • To get the GPS timestamp of each received sample from a USRP radio, set the PPSSource property to 'GPSDO'.

  • To get the timestamp of each received sample from bundled radios, set the PPSSource property to 'GPSDO' or 'External'.

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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infoUSRP radio information
gpsLockedStatusLock status of GPSDO to GPS constellation
referenceLockedStatusLock status of USRP radio to 10 MHz clock signal
captureCapture RF signal data using USRP radio
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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Open Live Script

Configure a B210 radio with a serial number B312. Set the radio to receive at 2.5 GHz with a decimation factor of 256.

Create an SDRu Receiver System object for data reception.

rx = comm.SDRuReceiver(...
              Platform ="B210", ...
              SerialNum ="B312", ...
              CenterFrequency =2.5e9, ...
              MasterClockRate =56e6, ...
              DecimationFactor =256);

Save the valid data using the dsp.SignalSink System object.

rxLog = dsp.SignalSink;
    for counter = 1:20
        data = rx();
        rxLog(data);
    end
release(rx)
release(rxLog)
Open Live Script

Create an SDRu receiver System object for a multichannel radio configuration.

radio = comm.SDRuReceiver(Platform ="X300",IPAddress ='192.168.60.2');
radio.ChannelMapping = [1 2];
radio.CenterFrequency = [1.2 1.3]*1e9;
radio.Gain = [5 6];

Get the radio information by calling the info function.

info(radio)
ans = struct with fields:
                    Mboard: 'X300'
                  RXSubdev: {'UBX RX'  'UBX RX'}
                  TXSubdev: {'UBX TX'  'UBX TX'}
    MinimumCenterFrequency: [-70000000 -70000000]
    MaximumCenterFrequency: [6.0800e+09 6.0800e+09]
               MinimumGain: [0 0]
               MaximumGain: [37.5000 37.5000]
                  GainStep: [0.5000 0.5000]
           CenterFrequency: [1.2000e+09 1.3000e+09]
     LocalOscillatorOffset: 0
                      Gain: [5 6]
           MasterClockRate: 200000000
          DecimationFactor: 512
        BasebandSampleRate: 390625
Open Live Script

Configure a B200 radio with an IP address set to 30FD838. Set the radio to receive at 1 GHz with a decimation factor of 512 and a master clock rate of 56 MHz.

Create an SDRu Receiver System object for data reception. Calculate the baseband sample rate by using the master clock rate and decimation factor.

rx = comm.SDRuReceiver(...
              Platform ="B200", ...
              SerialNum ="30FD838", ...
              CenterFrequency =1e9, ...
              MasterClockRate =56e6, ...
              DecimationFactor =512);
sampleRate = rx.MasterClockRate/rx.DecimationFactor;

Create a baseband file writer object with a center frequency of 1 GHz.

rxWriter = comm.BasebandFileWriter('b200_capture.bb', ...
         sampleRate,rx.CenterFrequency);

Write the valid baseband data to 'b200_capture.bb'.

for counter = 1:2000
    data = rx();
    rxWriter(data);
end

Display information about the received signal. Release the System objects.

info(rxWriter);
release(rx);
release(rxWriter);
Open Live Script

Configure a B200 radio with serial number 30FD838. Set the radio to receive at 2.5 GHz with a decimation factor of 125, the output data type to double and master clock rate of 56 MHz.

Create a USRP radio receiver System object for data reception.

rx = comm.SDRuReceiver(Platform ="B200", ...
         SerialNum ="30FD838", ...
         CenterFrequency =2.5e9, ...
         MasterClockRate =56e6, ...
         DecimationFactor =125, ...
         OutputDataType ="double");

Capture signal data using comm.DPSKDemodulator System object.

demodulator = comm.DPSKDemodulator(BitOutput =true);

Inside a for-loop, receive the data using the rx System object and it returns overrun as an output argument. With SRDu receiver System objects, the overrun output indicates data loss. This output is a useful diagnostic tool for determining real-time operation of the System object. Display the messages when the receiver indicates an overrun with data loss.

for frame = 1:2000
    [data,overrun] = rx();
    demodulator(data);
      if overrun ~= 0
         msg = ['Overrun detected in frame #',int2str(frame)];
      end
end
release(rx)
Open Live Script

Configure a B200 radio with serial number 30FD838. Set the radio to receive at 2.5 GHz with a decimation factor of 125 and master clock rate of 56 MHz. Enable burst-mode buffering to overcome overruns. Set the number of frames in a burst to 20 and the number of samples per frame to 37500.

Create an SDRu receiver System object to use for data reception.

rx = comm.SDRuReceiver(...
               Platform ="B200", ...
              SerialNum ="30FD838", ...
              CenterFrequency =2.5e9, ...
              MasterClockRate =56e6, ...
              DecimationFactor =125, ...
              OutputDataType ="double");
rx.EnableBurstMode = true;
rx.NumFramesInBurst = 20;
rx.SamplesPerFrame = 37500;

Capture signal data using comm.DPSKDemodulator System object.

demodulator = comm.DPSKDemodulator(BitOutput =true);

Inside a for-loop, receive the data using the rx System object.

numFrames = 100;
for frame = 1:numFrames
    [data,overrun] = rx();
      if ~(overrun)
         demodulator(data);
      end
end
release(rx)
Open Live Script

This example shows how to get the GPS timestamp of each received data sample using a USRP radio.

Configure a B210 radio with the serial number set to 3136D5F. Set the PPS signal source to the PPS signal from a GPSDO and enable GPS time synchronization. Set the clock source to GPSDO. Set themaster clock rate to 20MHz, decimation factor to 20, and number of received samples per frame to 10.

Create an SDRu receiver System object for data reception.

format long;                    
rx = comm.SDRuReceiver(Platform = "B210", SerialNum='3136D5F', ...
                       PPSSource = "GPSDO", EnforceGPSTimeSync = true, ...
                       ClockSource= "GPSDO", ...
                       MasterClockRate=20e6, DecimationFactor=200, ...
                       SamplesPerFrame = 20000);

Check the GPS lock status. 

GPSLockStatus = 0;
while ~GPSLockStatus 
    disp("Trying to lock to GPS constellation ...");
    GPSLockStatus =  gpsLockedStatus(rx);
end
Trying to lock to GPS constellation ...

if GPSLockStatus
    disp("GPSDO is locked. Acquiring data from radio ...");
    [data,~, ~,GPSTimestamps] = rx();
    d = datetime(GPSTimestamps(1), 'convertfrom', 'posixtime', 'Format', 'MM/dd/yy HH:mm:ss.SSS','TimeZone','Asia/Calcutta');
end
GPSDO is locked. Acquiring data from radio ...

USRP time synchronized to GPS time

Release the System object. Display the GPS timestamp of the first sample received.

release(rx);
fprintf('GPS timestamp of first sample: %s',d);
GPS timestamp of first sample: 07/27/23 16:33:38.078
Open Live Script

Receive phase synchronized signals using the TwinRX daughterboard. Transmit the sinusoidal signals with a B210 radio and receive the signals on an X300 radio with two TwinRX daughterboards. This example requires two MATLAB sessions running on your host computer.

In the first MATLAB session, configure a B210 radio with the serial number 31B92DD. Set the radio to transmit at 2.45 GHz with an interpolation factor of 100, and a master clock rate of 61.44 MHz. Specify a gain of 60 dB and transport data type of int16.

tx = comm.SDRuTransmitter(...
                    Platform ="B210", ...
                    SerialNum = "31B92DD", ...
                    MasterClockRate = 61.44e6, ...
                    InterpolationFactor = 100, ...
                    Gain = 60, ...
                    CenterFrequency = 2.45e9, ...
                    TransportDataType = "int16");

Generate a sine wave with a frequency of 30 kHz for transmission. Calculate the sample rate by using the master clock rate and interpolation factor for an B210 radio System object configuration. Set the output data type of the sine wave to double.

sinewave = dsp.SineWave(1,30e3); 
sinewave.SampleRate = 100e6/100; 
sinewave.SamplesPerFrame = 5e4; 
sinewave.OutputDataType = 'double'; 
sinewave.ComplexOutput = true;
data = step(sinewave);

Set the frame duration for the transmission based on the samples per frame and sample rate. Create time scope and frequency scope System objects to display time-domain and frequency-domain signals, respectively. Display a message when transmission starts.

frameDuration = (sinewave.SamplesPerFrame)/(sinewave.SampleRate); 
time = 0;
timeScope = timescope(TimeSpanSource = "Property", TimeSpan = 4/30e3,...
                      SampleRate = 100e6/100);
spectrumScope = dsp.SpectrumAnalyzer('SampleRate',sinewave.SampleRate); 
disp("Transmission Started"); 
timeScope(data); 
spectrumScope(data);

Inside a while-loop, transmit the sine wave using the tx System object. Display a message when transmission is complete. Release the radio System object.

while time < 30
    tx(data); 
    time = time+frameDuration; 
end 
disp("Transmission Stopped"); 
release(tx);

In the second MATLAB session, configure an X300 radio with an IP address of 192.168.20.2. Set the radio to receive at 2.45 GHz with a decimation factor of 200 and a master clock rate of 200 MHz. Enable the TwinRX daughterboard and the TwinRX phase synchronization capability to receive phase synchronized signals. Set the ChannelMapping property to [1 2 3 4]. Connect the power splitter from an B210 transmitter to four receiver channels of the X300 radio for calibration.

rx = comm.SDRuReceiver(Platform = "X300", ...
                    IPAddress = '192.168.20.2', ...
                    OutputDataType = "double", ...
                    IsTwinRXDaughterboard = true, ...
                    EnableTwinRXPhaseSynchronization = true, ...
                    ChannelMapping = [1 2 3 4], ...
                    MasterClockRate = 200e6, ...
                    DecimationFactor = 200, ...
                    Gain = 70, ...
                    CenterFrequency = 2.45e9, ...
                    SamplesPerFrame = 4000);

Set the frame duration for the signal reception based on the samples per frame and sample rate. Create time scope and frequency scope System objects to display time-domain and frequency-domain signals, respectively. Display a message when reception starts.

frameduration = (rx.SamplesPerFrame)/(200e6/200); 
time = 0; 
timeScope = timescope(TimeSpanSource = "Property",...
                      TimeSpan = 4/30e3,SampleRate = 200e6/200);
spectrumScope = dsp.SpectrumAnalyzer('SampleRate',200e6/200); 
spectrumScope.ReducePlotRate = true; 
disp("Reception Started");
Reception Started

Inside a while-loop, receive the sine wave using the rx System object. Normalize the signal with respect to the amplitude for each receive channel. Compute the fast Fourier transform (FFT) of each normalized signal. Calculate the phase difference between channels 1 and 2, channels 1 and 3, and channels 1 and 4. Display the phase difference between channel 1 and each of the other channels of the TwinRX daughterboard.

counter = 0;
while time < 10 && counter < 10  
 data = rx();  
    amp(1) = max(abs(data(:,1))); 
    amp(2) = max(abs(data(:,2))); 
    amp(3) = max(abs(data(:,3))); 
    amp(4) = max(abs(data(:,4))); 
    maxAmp = max(amp); 
    if any(~amp)  
       normalizedData = data; 
    else 
      normalizedData(:,1) = maxAmp/amp(1)*data(:,1); 
      normalizedData(:,2) = maxAmp/amp(2)*data(:,2); 
      normalizedData(:,3) = maxAmp/amp(3)*data(:,3); 
      normalizedData(:,4) = maxAmp/amp(4)*data(:,4); 
    end 
    freqOfFirst = fft(normalizedData(:,1)); 
    freqOfSecond = fft(normalizedData(:,2)); 
    freqOfThird = fft(normalizedData(:,3)); 
    freqOfFourth = fft(normalizedData(:,4)); 
    angle1 = rad2deg(angle(max(freqOfFirst)/max(freqOfSecond))); 
    angle2 = rad2deg(angle(max(freqOfFirst)/max(freqOfThird))); 
    angle3 = rad2deg(angle(max(freqOfFirst)/max(freqOfFourth))); 
    timeScope([real(normalizedData),imag(normalizedData)]); 
    spectrumScope(normalizedData); 
    time = time + frameduration;
    counter = counter +1;
    disp([' Phase difference between channel 1 and 2: ', num2str(angle1)]); 
    disp([' Phase difference between channel 1 and 3: ', num2str(angle2)]);
    disp([' Phase difference between channel 1 and 4: ', num2str(angle3)]); 
    disp(' ');

end 
 Phase difference between channel 1 and 2: 22.7838

 Phase difference between channel 1 and 3: 159.7515

 Phase difference between channel 1 and 4: -136.388

 

 Phase difference between channel 1 and 2: 22.7311

 Phase difference between channel 1 and 3: 159.9299

 Phase difference between channel 1 and 4: -136.2448

 

 Phase difference between channel 1 and 2: 22.7629

 Phase difference between channel 1 and 3: 160.0174

 Phase difference between channel 1 and 4: -136.2094

 

 Phase difference between channel 1 and 2: 22.8828

 Phase difference between channel 1 and 3: 159.9154

 Phase difference between channel 1 and 4: -136.3182

 

 Phase difference between channel 1 and 2: 22.8373

 Phase difference between channel 1 and 3: 160.068

 Phase difference between channel 1 and 4: -136.2829

 

 Phase difference between channel 1 and 2: 22.911

 Phase difference between channel 1 and 3: 160.032

 Phase difference between channel 1 and 4: -136.1785

 

 Phase difference between channel 1 and 2: 22.8487

 Phase difference between channel 1 and 3: 160.069

 Phase difference between channel 1 and 4: -136.2131

 

 Phase difference between channel 1 and 2: 22.8922

 Phase difference between channel 1 and 3: 159.9904

 Phase difference between channel 1 and 4: -136.2636

 

 Phase difference between channel 1 and 2: 22.8615

 Phase difference between channel 1 and 3: 160.0293

 Phase difference between channel 1 and 4: -136.2306

 

 Phase difference between channel 1 and 2: 22.8312

 Phase difference between channel 1 and 3: 160.0191

 Phase difference between channel 1 and 4: -136.4391

 

release(timeScope); 

release(spectrumScope); 

release(rx);
disp("Reception ended"); 
Reception ended

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 sweep time to obtain the slope.

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

Use bw2rangeres (Phased Array System Toolbox) function to get the range resolution corresponding to the signal bandwidth and time2range (Phased Array System Toolbox) function to get 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 the 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 the 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 the Timescope and SpectrumScope

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]);

Transmission and Reception of FMCW Radar Waveform

Transmit the FMCW radar waveform and receive the reflceted 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);

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

Create a function that configures comm.SDRuReceiver System object. Set the frame duration for the radio to receive data based on samples per frame and sample rate. Display a message when reception starts. Inside a for-loop, receive the data using the rx System object and return the overrun output argument. 

function [receiveTime,overrunCount] = sdruReceiveData()
        duration = 10;
        masterClockRate = 35e6;
        decimationFactor = 1;
        samplesPerFrame = 10000;

        sampleRate = masterClockRate/decimationFactor;
        frameDuration = samplesPerFrame/sampleRate;
        iterations = duration/frameDuration;

        rx = comm.SDRuReceiver(Platform = "B210",SerialNum = "30F59A1", ...
                       MasterClockRate = masterClockRate, ...
                       DecimationFactor = decimationFactor, ...
                       OutputDataType = "double");
        count = 0;
        rx();
        disp("Started Reception...");
        tic
        for i = 1:iterations
            [data,~,overrun] = rx();
            if overrun
            count = count + 1;
            end
        end
        receiveTime = toc;
        overrunCount = count;
        release(rx);
        end

Generate a MEX file with the name sdruReceiveMex from the function sdruReceiveData.

codegen sdruReceiveData -o sdruReceiveMex;

Run this MEX file to receive data using the generated MEX and observe the reception time and number of overruns.

[ReceiveTime,overrunCount] = sdruReceiveMex()

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Introduced in R2011b

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