9 internal fsk mode – BNC 630 User Manual
Page 28
23
5.9 Internal FSK Mode
Introduction
The Internal FSK mode generates a frequency shift keyed signal of fixed amplitude. An internal timer is used as a modulating
signal to toggle the output frequency between the Mark frequency and the Space frequency at a specified rate.
Internal FSK Mode Parameters
The Internal FSK mode has the following front panel display:
Figure 5.9-1: Internal FSK mode display
1. Modulating Frequency
In this field enter the frequency at which the output will switch between the Mark and Space frequencies. You may enter from 0
Hz to 130,000 Hz in 1 Hz steps.
The internal modulating frequency is accurate to 1 Hz from 0 Hz to 3900 Hz. It is accurate to within 1% across its full range of 0
Hz to 130,000 Hz.
2. Mark Frequency
In this field enter the Mark frequency, from 0 Hz (DC) to 21.5000000 MHz in .01 Hz steps.
3. Space Frequency
In this field enter the Space frequency, from 0 Hz (DC) to 21.5000000 MHz in .01 Hz steps.
4. Level
In this field enter the output level, from 4 mVp-p to 10 Vp-p in 1 mV steps or from -44.0 dBm to +24.0 dBm in .1 dBm steps.
NOTE: For wideband FSK (where the difference between Mark and Space frequencies is > 1.0 MHz), the output level may shift
slightly between the mark and space frequencies. The 630 has internal leveling circuitry which is disabled in this mode, in order to
offer higher FSK modulation rates.
NOTE: The level specified is a 50 ohm LOADED level. This is the level of the signal which will appear across a 50 ohm load
connected to the SIG Out connector. Into an open circuit, the output swing will be twice the value entered.
Offset
You can enter an offset voltage for the output waveform. For more information on output offsets refer to section 4.4.
Ext Gating Input
(rear panel connector)
This TTL compatible input can be used to gate the output signal on or off. A logic high voltage turns off the output.
For further information on the Ext Gating Input, refer to section 2.0.
Int FSK: 1,000 Hz
Mark: 1,000,000.00 Hz
Space: 2,000,000.00 Hz
-10.0 dBm
2
1
3
4