Image and Spur Rejection in Fast sweep mode ( SA44B )

Hi,

I have a question about fast sweep mode. Works Image and Spur Rejection in full range frequency of SA44B (1 Hz – 4.4 GHz) for fast sweeping?

And second question: Does SA44B have intermediate frequency (IF) 21.4 MHz?

Here is manual’s part of SA44B about Image and Spur Rejection:

“The USB-SA44B does not have hardware-based image rejection, instead relying on a software algorithm
to reject image responses. The algorithm mixes the incoming RF with two distinct local oscillator
frequencies, typically spaced by 21.4 MHz and up to 100 milliseconds, and rejects responses not present
in both. This algorithm has some limitations:”

THX for answers

Wizardek

Wizardek,
The IF frequency for the SA44B in fast sweep is 10.7 MHz. Image rejection works by injecting the LO low side (RF – 10.7 MHz), and then high side (RF + 10.7 MHz), and taking the lower reading for each bin.

Hi Justin,

THK for fast answer. What does means IF 2.9 MHz in user manual? The IF is variable?

Attachments:

You must be logged in to view attached files.

The 2.9 MHz IF is used when span is 200 kHz or less, to provide superior image rejection for narrow-band sweeps. It sweeps once with a 10.7 MHz IF, and once with a 2.9 MHz IF, and compares results to provide the cleanest spectrum possible.

Justin,
THKS, I understand this correctly? For span 200 kHz and less makes four “samples”? These samples are (RF-10.7 MHz), (RF-2.8 MHz) for low side band and (RF+10.7 MHz), (RF+2.8 MHz)? And for span 250 kHz and 5 MHz are only two “samples” (RF-10.7 MHz) and (RF+10.7 MHz)?

Wizardek

For spans (not RBW) of 200 kHz or less, the LO frequencies are RF + 10.694 MHz and RF + 2.921 MHz. For spans greater than 200 kHz (up to several GHz), the LO frequencies are RF + 10.7 and RF – 10.7. In both cases the signal is sampled twice.

[Author]

Posts