Baseband Sample Rate in NI USRP Radios

Each Wireless Testbench™ reference application object enables you to set the baseband sample rate of the radio by using the SampleRate object property. The object automatically selects the master clock rate 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.

Supported Master Clock Rates

The analog-to-digital converter (ADC) and digital-to-analog converter (DAC) in USRP™ radios run at the full master clock rate, which is hardware-dependent. This table shows the master clocks rates available on supported NI™ USRP radios.

Radio Device	Master Clock Rate
USRP N310	122.88 MHz 125.00 MHz 153.60 MHz
USRP N320	200.00 MHz 245.76 MHz 250.00 MHz
USRP N321	200.00 MHz 245.76 MHz 250.00 MHz
USRP X310	184.32 MHz 200.00 MHz
USRP X410	245.76 MHz 250.00 MHz

Set Baseband Sample Rate

The object automatically selects the master clock rate on the radio hardware based on the SampleRate property value. If necessary, to achieve the specified sample rate, the radio uses a Farrow rate converter along with integer interpolation for transmit signals or integer decimation for capture signals.

To bypass the Farrow filter, set the SampleRate property to a master clock rate value or to a value such that MCR/SampleRate is a supported decimation or interpolation factor, where MCR is the master clock rate that the object selects.

Radio	Supported Decimation or Interpolation Factor
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 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

Farrow Rate Converter

If MCR/SampleRate is not a supported decimation or interpolation factor, the signal passes through the Farrow rate converter. Because of hardware limitations, the Farrow rate converter can only convert sample rates that are less than MCR/2.

Resampling Transmit Waveform

If the basebandTransceiver, basebandTransmitter, or preambleDetector object uses a Farrow rate converter to achieve the sample rate specified by the SampleRate property, the object resamples the transmit waveform that you specify when calling the transmit object function. The resulting waveform has an increased number of data samples.