Operating instructions

More Complex Programming Examples R&S ESCI
1166.6004.12 7.22 E-1
Measuring the Third Order Intercept Point
The third order intercept point (TOI) is the (virtual) level of two adjacent useful signals at which the
intermodulation products of third order have the same level as the useful signals.
The intermodulation product at f
S2
is obtained by mixing the first harmonic of the useful signal P
N2
with
signal P
N1
, the intermodulation product at f
S1
by mixing the first harmonic of the useful signal P
N1
with
signal P
N2
.
f
s1
= 2 x f
n1
- f
n2
(1)
f
s2
= 2 x f
n2
- f
n1
(2)
The following example is based on two adjacent signals with a level of –30 dBm at 100 MHz and
110 MHz. The intermodulation products lie at 90 MHz and 120 MHz according to the above formula. The
frequency is set so that the examined mixture products are displayed in the diagram. Otherwise, the
default setting of the R&S ESCI is used for measurements (SetupInstrument).
REM ************************************************************************
Public Sub TOI()
result$ = Space$(100)
'--------- R&S ESCI default setting ----------------------------------------
----
CALL SetupStatusReg 'Set status registers
CALL IBWRT(receiver%,"*RST") 'Reset instrument
CALL IBWRT(receiver%,"INIT:CONT OFF") 'Single sweep
CALL IBWRT(receiver%,"SYST:DISP:UPD ON") 'ON: display on
'OFF: off
'--------- Set frequency ---------------------------------------------------
CALL IBWRT(receiver%,"FREQ:STARt 85MHz;STOP 125 MHz") 'Span
'--------- Set level -------------------------------------------------------
CALL IBWRT(receiver%,"DISP:WIND:TRAC:Y:RLEV –20dBm") 'Reference level
CALL IBWRT(receiver%,"INIT;*WAI") 'Perform sweep with sync
'--------- TOI measurement -------------------------------------------------
CALL IBWRT(receiver%,"CALC:MARK:PEXC 6DB") 'Peak excursion
CALL IBWRT(receiver%,"CALC:MARK:FUNC:TOI ON") 'Switch on TOI measurement
CALL IBWRT(receiver%,"CALC:MARK:FUNC:TOI:RES?") 'and read out results
CALL IBRD(receiver%,result$)
'--------- Read out result ------------------------------------------------
Print "TOI [dBm]: ";result$
END SUB
REM
************************************************************************