1
Getting
Started
Functional Description
1-9
Functional
Description
A detailed functional description is given in the following
paragraphs. The description is divided into logical groups: front
panel connectors, operating modes, output type, output state and
filters.
Front Panel
Connectors
The 5251 has 3 BNC connectors on its front panel: main and SYNC
outputs and trigger input. There are also 2 SMB connectors:
sample clock and 10 MHz reference clock inputs. These
connectors are described below.
Output
The output connector outputs fixed (pre-defined) waveforms to 100
MHz, user (arbitrary) and sequenced waveforms with sampling
clock to 250 MS/s. Output impedance is 50
Ω
, that is, the cable
connected to this output should be terminated with 50
Ω
load.
Amplitude accuracy is calibrated when connected to a 50
Ω
load.
The amplitude is doubled when the output impedance is above 1
M
Ω
.
SYNC Output
The SYNC output generates a single TTL pulse for synchronizing
other instruments (i.e., an oscilloscope) to the output waveform.
The SYNC signal always appears at a fixed point relative to the
waveform. The location of the SYNC signal along the waveform is
programmable. The SYNC output is also used as marker output
when the sweep, or other modulation functions are turned on.
TRIG IN
In general, this input accepts signals that stimulate generation of
output waveforms. The trigger input is inactive when the generator
operates in continuous mode. When placed in trigger, gated or
burst modes, the trigger input is made active and waits for the
proper condition to trigger the instrument. In trigger and burst
modes, the trigger input is edge sensitive, i.e., it senses transitions
from high to low or from low to high to trigger the 5251. The
direction of the transition is programmable. In gated mode, the
trigger input is level sensitive, i.e., the generator is gated when the
logic level is high and idle when the level is logic low. Trigger level
for this input is programmable within the rage of -5V to +5 V.
The same input is used in FSK, ASK and PSK mode, where the
output hops between two frequencies, amplitude and phases. The
output generates carrier frequency, amplitude and phase when the
trigger input level is false and consequently, shifted frequency,
amplitude and phase when the trigger input level is true.
Summary of Contents for 5251
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