User`s guide

14
Setting Up and Doing a
Measurement
The order of keystrokes for
setting up a group delay
measurement is not crucial. The
HELP key under the Sweep
menu describes one possible
sequence:
1. Configure the sources
(Sources menu): the
personality allows for the
HP-IB control for up to three
sources (RF, LO, and
modulation). At a minimum,
you must have control of the
RF source to perform a
measurement. When entering
an HP-IB address, use the
last two digits only (for
example, enter 19 rather
than 819). If you are using an
HP 8360 series synthesizer
with the internal modulation
generator option (Opt. 002),
the mod address should be
the same as the RF address,
and both RF src: and Mod
src: should be set to
HP836XX.
When using an HP 70340A
synthesizer, set RF src: to
HP 836XX.
2. Set the power level of the
sources (Power menu):
usually, only the RF power is
set. If a non-HP-IB modulation
generator or the internal
modulation option of the
HP 8360 is used, you need
not set the MOD POWER. If the
internal modulation option is
available, set the AM DEPTH
or FM DEVIATion, as
appropriate. For best results
with either internal or
external modulation, use an
RF frequency. Use the
following guide for setting M
and N:
Upconverters:
M = 1, N = 1
(IF = RF + LO)
Downconverters:
For LO > RF,
M = -1, N = 1
(IF = LO - RF)*
For LO < RF,
M = 1, N = -1
(IF = RF - LO)
* frequency inversion occurs
If the DUT is a multiplier, set
M to the correct harmonic
number, and set N and LO to
zero.
The softkey labeled RF is
used for setting the
synthesizer frequency after
VIEW SPECTRM is pressed.
The value for RF is normally
the center of the passband of
interest. During the actual
measurement, this value is
not used, as the synthesizer
is programmed according to
the start, stop, and step
frequencies.
If the LO frequency is not
known exactly, use the FIND
LO routine under the Process
menu. This routine also
programs the synthesizer to
the value set by the RF
softkey. After the LO
frequency is computed, it
automatically updates the
value for the LO softkey. This
routine requires that M and
N are set correctly.
AM depth of 90%, or an FM
deviation of twice the
modulation frequency (ß=2).
This will maximize the
amplitude of the modulation
sidebands of interest.
Note: that when measuring a
multiplier with FM, the
deviation must be corrected by
the multiplication factor.
For example, if using 1 MHz of
FM to test a x3 multiplier, the
deviation should be set to
2 MHz/3 or 667 KHz.
3. Configure the system (Config
menu): the first step is to
select the modulation type
and frequency with the top
two softkeys. Remember, the
measurement aperture is
equal to twice the modulation
frequency, and is independent
of the frequency step.
Next, enter M, N and the LO
frequency which correspond
to the hardware setup. The
following equation is used to
compute the IF frequency at
the output of the DUT:
IF = M*RF + N*LO
The signs of M and N are
determined from whether the
DUT is an up or
downconverter, and whether
it uses high or low-side LO
mixing. The IF frequency
must always be positive, but
it can sweep either up or
down in frequency. This
flexibility allows measurement
of frequency-inverting devices.
Frequency inversion only
occurs when measuring a
downconverter where the LO
frequency is higher than the