Atec HP-Agilent-8904A - Manual (Page 7)

AM FM F M DSB Pulse
Output 1
Output 2
CHANNEL B
CHANNEL C
CHANNEL D
S
External . Freq Phase Amp
Timing
7
. . . Fast hop
Option 003 adds the ability to hop the
8904A in frequency, phase, and/or
amplitude. Up to 16 frequency/phase/
amplitude states can be entered into
the “Hop Ram” memory. To hop, an
external device must address the four-
bit TTL-level address bus provided on
the digital port connector on the rear
panel. As the address supplied to the
bus is varied, the 8904A will hop to
the frequency/phase/amplitude state
that corresponds to that address of the
Hop Ram memory. Fast hop can only
be performed on channel A. Phase
continuous frequency switching can
be done in as little as 8 µs. Since the
signals are digitally created, there is no
settling time like traditional PLL syn-
thesizers. Only the cycle time of the
Digital Waveform Synthesis IC deter-
mines the switching speed. Control
functions allow you to enable or disable
any one of the three hop parameters.
For example, phase and amplitude hop
can be disabled to produce only fre-
quency hopping without having to
remove the phase and amplitude hop
data from the Hop Ram. If Option 001
and 003 are installed, the other three
channels can be used while hopping.
Channel B, for example, could be set to
phase modulate channel A with noise
while channel A is hopping. This setup
allows controlled amounts of “phase
noise” to be added to the hopping signal.
. . . Digital modulation
One application for Option 003 is the
creation of digital modulation formats.
By hopping frequency, FSK and other
frequency switching type modulation
formats with up to 16 frequencies can
be generated. BPSK, QPSK, and other
phase shifting formats can be made by
hopping just phase. With a combina-
tion of amplitude and phase hopping,
the 8904A Option 003 can generate
QAM signals with up to 16 phase
amplitude states. The digital data
must be supplied to the digital con-
trol port in a four-bit wide parallel
word to control the timing.
Add external timing control to get . . .
Option 003 adds external
timing control for fast hop
or digital modulation
CHANNEL A