User`s guide
5
70004A
70820A
HP-IB
10 MHz
Ref
CH 1
CH 2
HP 71500A with
IBASIC
Attenuator
20 dB
RF
Out
Internal Modulation Opt. 002
Frequency Translating DUT
Internal
LO
AM/FM Output
(rear panel)
836xxA
Figure 2: Measurement setup using internal modulation.
Simplified user interface.
Custom menukeys tailor the
MTA’s user interface for making
group delay measurements
without the need for an external
computer.
Limitations
The key limitations of this
application are that it is slower
than most other solutions, and
the relative accuracy, while
adequate for most measurements,
may not be as good compared
to what customers have come to
expect from instruments such
as the HP 8510 vector network
analyzer.
Measurement
Overview
Measurement Block
Diagram
A block diagram view of the
measurement is shown in figure
1. The modulated RF carrier is
measured in channel 1 of the
HP 71500A, while the baseband
modulation signal is measured
as a reference in channel 2.
The modulation source can be a
stand-alone instrument or
internal to the RF source.
Modulation Source
There are two basic
measurement setups. The first
setup (figure 2) uses the internal
modulation capabilities of the
source, such as (optionally)
provided by the HP 8360 family
of synthesizers. The second
setup (figure 3) uses an external
modulation source, controlled
either manually or via HP-IB.
Many non-HP-IB modulation
sources have poor frequency
accuracy. In some cases, it may
be necessary to fine-tune
the modulation frequency of the
source to match the value used
in the program.
Note: when connecting
synthesizers or modulation
sources that are to be controlled
via HP-IB, use the HP-IB
connector on the rear panel of
the HP 70820A module, NOT
the HP-IB connector on the
HP 70004A mainframe/display.
Connecting the 10 MHz
references of the HP 71500A
and the sources together is
recommended, but not required.
70004A
70820A
HP-IB
10 MHz
Ref
Attenuator
CH 1
CH 2
HP 71500A with
IBASIC
RF
Out
Frequency Translating DUT
Internal
LO
836xxA
Modulation
Input
Modulation Source
Figure 3: Measurement setup using an external modulation source.
Synthesizer Support
The group delay program
supports the HP 836xx, HP 834x,
HP 70340A, and HP 3325A
synthesizers. The program can
easily be modified to drive other
synthesizers if necessary (see
Adding Sources on page 19).
The group delay personality
does not require 1 Hz frequency
resolution of the RF source, but
this feature is very desirable for
other measurements (such as
pulsed-RF characterization) and
is highly recommended if a new
source is being ordered.