Setting The Measurement System; Accounting For Frequency Conversion; Sidebands And Images - Keysight Technologies N9040B UXA Manual

Measurement Related Tasks and Concepts

Setting the Measurement System

Setting the Measurement System

Accounting for Frequency Conversion

If noise figure measurement includes frequency conversions, the following
points will need to be carefully considered.

Sidebands and Images

For any measurement involving frequency conversion, you need to consider the
exact frequency ranges involved, and make decisions about the filtering
requirements for the specific measurement. For example, there may be several
different methods of measuring a mixer, and the method chosen may be set by
the choice of available filters.
Figure 3-1 Sidebands and Images with Downconversion
Amplitude
Simple, ideal, mixers output signals on both the sum and difference of their RF
and LO frequencies. Hence, for a fixed output frequency and a fixed LO
frequency, there are two different input frequencies that are converted to the
output frequency. This is shown in
The noise sources used in noise figure measurements are broad-band. When
using a downconverter, there is a probability that noise will be presented to a
simple mixer in both the upper and lower input frequency bands that are
converted into the same IF output band to which the analyzer is tuned. The
analyzer receives mixer-created noise from the two frequency bands which are
superimposed. The noise is random, and the two power levels combine by
simple addition. Similarly, the analyzer receives noise-source-created noise
from the two frequency bands combined as added power. Any measurement
where two mixing products are combined like this is usually termed
Double-Sideband, DSB.
50
F -F
usb lo
mixing
F -F
lo lsb
mixing
Broad-band Noise
X-Series Input
Band
F
LO
LSB Input
Figure 3-1.
N9069C Noise Figure Measurement Guide
Frequency
USB Input