This is due to a known issue where a PLL within the downconverter takes about 20 ms to change bands. Due to the frequency plan used in the unit, this occurs only once in the operating band: at 30.5 GHz. There are two possible scenarios that can cause this:
- Changing from the 30.5-40 GHz band to the 24-30.5 GHz band
- Changing from the 24-30.5 GHz band to the 30.5-40 GHz band
We are working on a solution for this issue, but a workaround is presented here.
Using the SCPI command :SENSE:RF:LOCK? after sending the :FREQ:CENT command will return whether the device has locked yet or not. If it returns 0, :SENSE:RF:LOCK? should be polled until it returns 1. See the below example for how this would work.
[...]
:FREQ:CENT 30400000000;:*OPC?;:SENS:RF:LOCK? query returns 1
:FREQ:CENT 30440000000;:*OPC?;:SENS:RF:LOCK? query returns 1
:FREQ:CENT 30480000000;:*OPC?;:SENS:RF:LOCK? query returns 1
:FREQ:CENT 30520000000;:*OPC?;:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 0
:SENS:RF:LOCK? query returns 1
:FREQ:CENT 30560000000;:*OPC?;:SENS:RF:LOCK? query returns 1
:FREQ:CENT 30600000000;:*OPC?;:SENS:RF:LOCK? query returns 1
:FREQ:CENT 30640000000;:*OPC?;:SENS:RF:LOCK? query returns 1
[...]
This applies to all D4000 units to date. Please contact Support if need further assistance.