Aim-TTI TGA1240 Series, Инструкция по эксплуатации

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37
Tone Mode
General
In Tone mode the output is stepped through a user
−
defined list of up to 16 frequencies under the
control of the signal set by the
source
soft
−
key on the
TRIGGER IN
setup screen. This
signal can be the Internal Trigger Generator, an external trigger input, the front panel MAN TRIG
key or a remote command. On multi
−
channel instruments the control signal can also be the
Trigger Out from an adjacent channel.
All standard and arbitrary waveforms can be used in Tone mode with the exception of pulse,
pulse
−
train and sequence. During Tone all waveforms are generated in DDS mode for fast
phase
−
continuous switching between frequencies. For DDS operation all waveforms must be
4096 points in length; this is the natural length for standard waveforms but all arbitrary
waveforms are expanded or condensed in software to 4096 points when the Tone list is built. This
does not affect the original data.
Because DDS mode is used the frequency range for all waveforms is 1mHz to 10MHz in Tone
mode, including triangle, ramp and squarewave which have different limits in continuous
operation.
Tone Frequency
Press the
tone setup…
soft
−
key on the
MODE
screen, called by pressing the MODE key,
to get the
TONE
setup screen:
TONE type: trig
◊
◊
2·000000 kHz #2
♦
3·000000 kHz del
◊
◊
end of list #4
Each frequency in the list can be changed by pressing the appropriate soft
−
key and entering the
new value from the keyboard. The selected frequency can be deleted from the list by pressing
the
del
(delete) soft
−
key. Additional frequencies can be added to the end of the list by
selecting
end of list
with the appropriate soft
−
key and entering the new frequency from
the keyboard.
The whole list can be scrolled back and forward through the display using the rotary control.
Tone Type
The
type
soft
−
key on the
TONE
setup screen permits three types of tone switching to be
specified.
With
type
set to
trig
the frequency changes after each occurrence of the signal edge
specified in the
source
and
slope
fields on the
TRIGGER IN
screen but only after
completing the last cycle of the current frequency.
With
type
set to
gate
the frequency changes when the signal specified in the
source
field goes to the level specified in the
slope
field on the
TRIGGER IN
screen and
continues until the level changes again at which point the current cycle is completed; the output
is then gated off until the next occurrence of the gating signal at which time the next frequency in
the list is gated on. The difference between triggered and gated tone changes is therefore that in
triggered mode the signal changes phase
−
continuously from one frequency to the next at the
waveform zero
−
crossing point immediately after the trigger signal whereas in gated mode there
can be an ‘off’ period between successive frequencies whilst the gate signal is not true.
With
type
set to
fsk
the frequency changes instantaneously (and phase
−
continuously)
at each occurrence of the signal edge specified in the
source
and
slope
fields on the
TRIGGER IN
screen without completing the current waveform cycle ; this is true FSK
(Frequency Shift Keying) tone switching.