HP 8753D - Page 426

Amplitude
and
Phase
Tracking
The
match
between
mixers
is
dened
as
the
absolute
dierence
in amplitude
and/or phase
response
over
a
specied
frequency
range
.
The
tracking between
mixers is
essentially how
well
the
devices
are
matched
over
a
specied
interval.
This interval
may be
a frequency
interval or
a
temperature
interval,
or
a
combination
of
both.
Y
ou
can
make
tracking
measurements
by
ratioing
the
responses
of two
mixer conversion
loss
measurements
.
Then
any
dierence
you
view
in
response is
due to
the mixers
and
not
the
measurement
system.
Replace
mixer
A
with
the
mixer
that
you
want to
compare it
to.
Mixer
R
should
always
remain
in
place
as
the
reference
mixer
.
Figure
6-97.
Connections for an
Amplitude and Phase Tracking Measurement Between Two Mixers
Phase Linearity and Group Delay
Group
delay is the rate of change of phase through a device with respect to frequency (d
 /d ! ).
Traditionally,
group delay has been used to describe the propagation delay (
 g), and deviation
from linear phase
through a linear device
. However
, this parameter also contains valuable
information about transmission delay
and distortion through a non-linear device such as a
mixer or frequency converter.For example, at group delay corresponds to low modulation
distortion (that is, carrier and sidebands propagate at the same rate).
Phase linearity and group delay are both measurements of the distortion of a transmitted
signal. Both measure the non-linearity of a device's phase response with respect to frequency.
Application and Operation Concepts 6-159