Baseband Sample Rate in NI USRP Radios
Each NI™ USRP™ radio supports a set of master clock rates (MCRs) and decimation or interpolation factors.
The following Wireless Testbench™ objects enable you to set the baseband sample rate of the radio by using the
SampleRate
object property. These objects automatically select the MCR
on the radio hardware based on the specified sample rate.
If necessary, to achieve the specified sample rate, the radio uses a Farrow
rate converter. For details, see Farrow Rate Converter. To bypass the Farrow filter
when using these objects, set the SampleRate
property to an MCR value, or
a supported decimation or interpolation factor of an MCR value.
The usrp
System object™ also selects the MCR and decimation or interpolation factor on the radio
hardware based on the specified baseband sample rate, but it does not use a Farrow rate
converter. You must set the SampleRate
property to an MCR value, or a supported decimation or
interpolation factor of an MCR value.
Supported Master Clock Rates
The analog-to-digital converter (ADC) and digital-to-analog converter (DAC) in USRP radios run at the full MCR, which is hardware-dependent. This table shows the master clocks rates available on supported NI USRP radios. For more information about radio support, see Supported Radio Devices.
Radio Device | MCR |
---|---|
USRP E320 (since R2025a) |
|
USRP N300 USRP N310 |
|
USRP N320 USRP N321 |
|
USRP X300 USRP X310 |
|
USRP X410 |
|
Set Baseband Sample Rate
NI USRP radios can transmit and receive waveforms at a sample rate of MCR divided by a supported decimation or interpolation factor, where MCR is the master clock rate.
Radio | Supported Decimation or Interpolation Factor |
---|---|
USRP E320 (since R2025a) | 1 |
2 | |
3 | |
Even integer in the range from 4 to 256 | |
Multiple of 4 in the range from 256 to 512 | |
Multiple of 8 in the range from 512 to 1008 | |
USRP N300 USRP N310 USRP N320 USRP N321 USRP X410 | 1 |
2 | |
3 | |
Even integer in the range from 4 to 256 | |
Multiple of 4 in the range from 256 to 512 | |
Multiple of 8 in the range from 512 to 1016 | |
USRP X300 USRP X310 | Integer in the range from 1 to 128 |
Even integer in the range from 128 to 256 | |
Multiple of 4 in the range from 256 to 512 | |
Multiple of 8 in the range from 512 to 1016 |
Note
If you have a USRP X410 radio, the application can derive a sample rate using interpolation or decimation from an MCR value up to 250 MHz. Without using the Farrow rate converter, the radio can generate the following sample rates:
245.76 MHz divided by a supported decimation or interpolation factor
250 MHz divided by a supported decimation or interpolation factor
491.52 MHz (since R2025a)
500 MHz (since R2025a)
Farrow Rate Converter
For the following Wireless Testbench objects, if MCR/SampleRate
is not a
supported decimation or interpolation factor, the signal passes through the Farrow rate converter.
Note
Because of hardware limitations, the Farrow rate converter can only convert sample rates that are less than MCR/2.
If you have a USRP X410 radio, the Farrow rate converter can only convert sample rates using an MCR value up to 250 MHz. This means that the radio can generate sample rates from 241,890 Hz to 125 MHz using the Farrow rate converter.
Resampling Transmit Waveform
When you call the transmit
function with an object that uses a
Farrow rate converter to achieve the sample rate specified by the
SampleRate
property, the object resamples the transmit waveform.
The resulting waveform has an increased number of data samples.
See Also
Objects
basebandReceiver
|basebandTransceiver
|basebandTransmitter
|preambleDetector
|energyDetector
|usrp