External Local Oscillators

The AIR-T's AD9371 provides two external LO inputs to allow an external synthesizer to be used with the device. These inputs must be 2x the desired LO frequency. Operation for the external LO option is limited to a maximum of 4000 MHz (8000 MHz maximum input external LO frequency). The power range for external LO signals is 0 to +6dBm.

Receive External Local Oscillator

First, connect an external synthesizer to the RLO (receive) connector. Next, configure SoapySDR device. The External LO is enabled via a device argument: rx_lo_src="external"

For example, modify the hello world example by replacing line 27 and 28 as follows:

Replace:

sdr.setFrequency(SOAPY_SDR_RX, 0, freq)         # Tune the LO

with:

sdr = SoapySDR.Device(dict(driver="SoapyAIRT", rx_lo_src="external"))
sdr.setFrequency(SOAPY_SDR_RX, 0, freq)         # Tune the LO

It is important that the frequency value used in sdr.setFrequency(SOAPY_SDR_RX, 0, freq) is the desired LO frequency (half the input external LO frequency).

Transmit Eternal Local Oscillator

Currently external LO is only supported for the receive path (RLO). Transimit (TLO) support is coming soon.


Last update: February 20, 2020