Setting RFSG IQ Rate

[RF_Buzzer]

Hi , 
RFSG has a property of setting the IQ Rate. While I am able to change the IQ Rate in RFSG using property nodes..  RFSG nevertheless coerces it to the next valid value. In my case, I need an IQ Rate of 24 MHz, and I am able to change the IQ Rate in RFSG using property nodes, but RFSG coerces it to 100 MHz. Can anyone please post a VI which sets the IQ Rate to 24 MHz without the RFSG coercing it to any other value .... or should I be using an external clock to do this ? In that case, I still need to RFSG Drivers for my application .... and regardless of the external clock, IQ Rate will again be set to some valid value ( 100 MHz ) ???                                                                                                                                        

[Giarc]

Hello RF_Buzzer,

The NI VSGs that utilize an arb and the PXI-5610 upconverter (PXI-5670, PXI-5671 and PXI-5672) have two different clocking modes for the sample clock: Divide Down and High Resolution.  By default, RFSG uses the Divide Down clock which delivers slightly better performance (especially phase noise) vs. the Hi-Res clock.  The Divide Down divides the 100 MHz sample clock by an integer N, 1 ≤ N ≤ 4,194,304 and will coerce it to one of these values.  The Hi-Res clock in contrast has a resolution of 1.06 uHz and can be tuned to arbitrary values. This clock will give you the 24 MHz rate you are looking for.

To set the sample clock mode, you can set the "Arb Onboard Sample Clock Mode" RFSG property before you set the IQ rate (see the jpg attached).

Regards,

Craig

National Instruments

Message Edited by criag on 09-25-2008 09:57 AM

[Candan]

Based on the RFSG Help file, the IQ rate for the 5670 has two distinct values. That is either 50 Mhz. or 100 Mhz.

Regards;

Candan