5.8.1. Hop frequency
Press
【
Menu
】
key to light “Hop_f” character, and then set hop frequency value. Frequency shift
keying is similar with FM whose modulating waveform is square. “hop frequency” is similar with
“frequency deviation”, with the difference of, frequency deviation is an offset value that the
frequency of carrier wave plus or minus, whose setting range is relational with the frequency of
carrier wave, hop frequency could be set arbitrarily within whole frequency range, it has no
relationship with carrier frequency.
5.8.2. Hop rate
Press
【
Menu
】
key to light “Rate” character, then set hop rate value. In FSK, the modulation
waveform is fixed as a square wave with 50% duty cycle, the frequency of the square wave is the
hop rate.
5.8.3. Trigger source
Press
【
Menu
】
key, select “Source” option and then set trigger source, there are only two values
to choose: 0 and 1. Set the value as 0 to choose internal trigger source, and set it as 1 to choose
external trigger source. If external trigger source is chosen, connect a TTL trigger signal to the
《
Trig In
》
port on the rear panel of the generator. W hen the trigger signal is with logic low level,
the frequency of output signal is the carrier frequency. W hen the trigger signal is with logic high
level, the frequency of output signal is the hop frequency. W hen external trigger source is chosen,
the hop rate setting is ignored.
5.8.4. Sync output
In FSK, the generator outputs a sync signal from the front panel “Sync” connector, which is a
square wave with TTL level and 50% duty cycle, its frequency is equal to the hop rate. When the
output signal is the carrier, a low level sync signal is outputted. W hen the output is hop frequency,
a high level sync signal is outputted.
In FSK, press
【
FSK
】
key again, the “FSK” keyboard indicator will be off, the generator exits FSK
function and returns back to continuous function.
5.9. Frequency sweeping function
In frequency sweep, the output frequency changes from the start frequency point to the end
frequency point according to the setting sweep time. Users may sweep within the whole frequency
range. During this process, the phase of output signals is continuous. All the 16 kinds of
waveform except of pulse and white noise listed in the waveform table could be swept.
Linearity frequency sweeping is similar with Ramp frequency modulation, with the difference of,
frequency sweeping does not use modulation waveform, but continuously output a series of
discrete frequency points according to certain time interval.
Press
【
Sweep
】
key, the light of it will be lighted and the CHA output frequency sweeping signal.
5.9.1. Start and end frequency
Press
【
Menu
】
key to light “Start” letter and then set start frequency point. Press
【
Menu
】
key to
light “Stop” letter and then set end frequency point. If the end frequency value is more than the
start frequency value, the sweep is positive from lower frequency to higher frequency, increasing
step by step from the start frequency to the end frequency and then return to the start frequency.
If end frequency value is less than the start frequency value, the sweep is opposite from higher
frequency to lower frequency, decreasing step by step from the start frequency to the end
frequency and then return to the start frequency.
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