Specifications

Setting up the PNA LO for an 8.33 MHz IF signal

ThePNALOmustbesetsothatan8.33MHzIFsignalisproducedbythemixersfor

inputtothePNAOptionH11inputs.Usingtheequationsbelow,theappropriateLO

frequencycanbecalculated.(TosetupthePNA-XLOforanIFsignal,intheprocedure

below, simply change “8.33 MHz” to “7.605634 MHz “.)

Using the rear panel LO available with Option H11 as the LO input of the 85309B:

Weknowthatforamixer,IF=N(LO)–RF

where N = external mixer harmonic number

WithOption080(frequencyoffset)thefrequencyoutoftherearpanelLOportisdefined

as,LO= (RF)+offset+8.33MHz

SubstitutingforLOinthefirstequationwehave,

IF=N((RF)+offset+8.33MHz)–RF

=()N(RF)+N(offset)+N(8.33)–RF

TocreatealowsideLO,setm=1andd=N

Simplifying,IF=RF+N(8.33)+N(offset)–RF

 =N(8.33)+N(offset)

Since IF must be equal to 8.33 MHz, then:

 8.33=N(8.33)+N(offset)

(1 – N)8.33 = N(offset)

Therefore, offset (MHz) = ( ) 8.33

UsingtheOption080dialogbox(showninFigure25)tosetuptheLO,entertheoffset

calculated above, set Multiplier to 1 and Divisor to N (the harmonic number of the

external mixer) and select the box next to Frequency Offset on/off, then click OK.

Figure 25. Option 080 dialog box.

Note

The following equations are not required for

frequencies under 20 GHz. At lower frequencies,

the PNA operates in fundamental mixing mode

andtheLOfrequencyisautomaticallyoffsetby

8.33 MHz.

1 – N