The IF OUT feature, available on most FieldFox models, is intended to provide a stable down-converted translation of the input RF signal. The signal is available at the IF OUT port, and is centered at the FieldFox 3rd IF frequency of 33.75 MHz. The Spectrum Analyzer should be set to Zerospan (Span = 0 Hz) so that a stable down-conversion can be maintained while using IF OUT.
In Zerospan, the SA is tuned to a specific center frequency which will be in ONE of the following 15 bands. When in Zerospan AND in IF OUT mode, an RF signal input AT the center frequency of the FieldFox is converted and appears at the IF OUT port at exactly 33.75 MHz. Signals above or below the center frequency show up above or below 33.75 MHz depending on the net inversion status of the band.
When IF OUT is selected (either Wide or Narrow), all Insta-Align background measurements are suppressed in order to avoid any interruption to the down-converted signal. As a result, on screen FieldFox amplitude accuracy specifications no longer apply and a Meas UNCAL message appears on the display.
|
Band # |
Frequency Range |
Net Inversion Status |
|
1 |
0 to 15 MHz |
Inverted |
|
2 |
15 MHz to 500 MHz |
Inverted |
|
3 |
500 MHz to 1366.25 MHz |
Inverted |
|
4 |
1366.25 MHz to 2600 MHz |
Inverted |
|
5 |
2600 MHz to 3900 MHz |
NOT Inverted |
|
6 |
3900 MHz to 7500 MHz |
NOT Inverted |
|
7 |
7500 MHz to 9500 MHz |
Inverted |
|
8 |
9500 MHz to 12.3 GHz |
Inverted |
|
9 |
12.3 GHz to 15.7 GHz |
Inverted |
|
10 |
15.7 GHz to 16.3 GHz |
Inverted |
|
11 |
16.3 GHz to 19.5 GHz |
NOT Inverted |
|
12 |
19.5 GHz to 23.0 GHz |
NOT Inverted |
|
13 |
23.0 GHz to 23.734 GHz |
NOT Inverted |
|
14 |
23.734 GHz to 25.5 GHz |
NOT Inverted |
|
15 |
25.5 GHz to 26.7 GHz |
NOT Inverted |
When the center frequency is tuned exactly at one of the band transitions, the selected band will be the higher of the two. For example, for a center frequency of exactly 15.000 MHz, band 2 is selected.
At band transitions, there is typically a small net gain change at the IF OUT port. The IF OUT feature is not calibrated. There is NO specification on Gain.
The individual bands have unique Net Inversion Status because of variance in the use of Hi Side and Low Side mixing during the translation.
Inverted - An RF input signal ABOVE the center frequency will appear BELOW the IF OUT center of 33.75 MHz.
NOT Inverted - An RF Input signal ABOVE the center frequency will appear ABOVE the IF OUT center of 33.75 MHz.
When selecting IF OUT, you chose between the following settings:
OFF - The translated IF signal at the IF OUT connector is no longer guaranteed to be centered at 33.75MHz.
Narrow - The IF frequency has approximately 15 MHz bandwidth.
Wide - The IF frequency has approximately 30 MHz bandwidth.
The above image shows measurements of the IF Out signal from another FieldFox. As the RF Input is stepped across the center frequency of the other FieldFox, the IF Out signal traces the bandpass of the Narrow (blue trace) and Wide (orange trace) IF Out choices. You can ignore the large signal to the left, which is the LO feedthrough from the measuring FieldFox.