Question:

How do I generate a Burst signal using the Agilent 33120A?  How do I output a signal once the Agilent 33120A receives a trigger? 

Answer:
Burst modulation outputs a specific number of cycles of a waveform at a designated rate. Getting Started

Carrier Waveform Shape
The shape of the signal. Can be sine (default), square, triangle, ramp, or arbitrary.
Carrier Frequency
The original frequency of the waveform. The frequency can range from 10 mHz to the maximum frequency of the waveform or 5 MHz (whichever is less) with a default of 1 kHz.
Burst Rate
The rate at which the specified number of cycles is output as a burst. Internal burst rate can be set from 10 mHz to 50 kHz. Default is 100 Hz.
Burst Count
The number of cycles to be output in each burst. Can be set from 1 (default) to 50,000 cycles, or infinite.
Burst Source
The Agilent 33120A has two triggered modes; internal and external. The internal triggered burst mode will output one burst of cycles (burst count) at a specified rate (burst rate). The external triggered burst mode will output one burst of cycles each time an external trigger is received. The external trigger can be in the form of a bus trigger, a press on the front-panel [SINGLE] key, or a rising edge of a TTL pulse to the rear-panel Ext Trig terminal. The trigger source is set to internal in the gated burst mode.
Burst Phase
The starting phase of the waveform. Can be set to any value between -360 degrees and +360 degrees. Can only be used in the triggered burst mode.
Gated Burst Mode
In the gated burst mode, the output is enabled or disabled based on the logic level of the gate signal applied to the Ext Trig terminal. While the gate signal is true (TTL high), the function generator outputs a continuous waveform. When the gate signal is false (TTL low), the output is turned off (zero volts or the DC offset level).
Triggered Burst Mode
In this mode, the Agilent 33120A will output one burst of cycles (burst count) each time a trigger is received. After the specified number of cycles has been output, the function generator waits for the next trigger. You can configure the function generator to accept an internal trigger (burst rate), a bus trigger, or an external trigger. External triggers can be sent by pressing the front-panel [SINGLE] key or by applying a trigger signal to the rear-panel Ext Trig terminal. The generator will output one burst of cycles when it receives the rising edge of a TTL pulse in the external trigger signal.
Front Panel Example We wish to output a three-cycle 5 Vpp, 1 kHz sine wave with a burst rate of 200 Hz.
  1. Select the function, frequency, and amplitude of the carrier. Press the [SINE] key on the front panel to select the sine wave (this is actually the default). Next, adjust the carrier frequency to 1 kHz using the arrow keys, the knob, or the enter number methods. Adjust the amplitude to 5 Vpp in the same manner.
  2. Turn on BURST. [SHIFT] [BURST] Note that the BURST annunciator turns on. At this point, the carrier is BURST modulated with the default burst parameters (100 Hz burst rate, a burst count of 1).
  3. Set the burst count. Press the [SHIFT] [RECALL MENU] to go directly to the BURST CNT command in the menu. Pres the down arrow, and adjust the burst count to 3 cycles using the arrow keys, the knob, or the enter number methods. Press the [ENTER] key to change the burst count and exit the menu.
  4. Set the Burst rate. Press the [SHIFT] [RECALL MENU] to go directly to the last command you used before exiting the menu previously (BURST CNT). Press the right arrow. You should see BURST RATE. Press the down arrow to enter the parameter. Using the arrow keys, the knob, or the enter number methods, adjust the shift rate to 200 Hz. Press [ENTER] to change the frequency and exit the menu.
The modulated signal is now ready to view on the oscilloscope. You should now see three cycles of a 5 Vpp, 1 kHz sine wave with a repetition rate of 200 Hz (5 ms). This is the internal triggered burst mode, where the Agilent 33120A triggers itself at the desired rate. In this mode, the starting phase can also be adjusted by modifying the BURST PHAS parameter in the menu. Programming Example Below is a sample program in Agilent Basic for the front-panel example. The example set up a three-cycle 5 Vpp, 1 kHz sine wave that will occur at a 200 Hz rate. 
   10 !

   20 CLEAR 7                       ! clear bus interface

   30 ASSIGN @Gen TO 710            ! assign I/O path to address

   40 OUTPUT @Gen;"*RST"            ! Reset the function generator

   50 !

   60 OUTPUT @Gen;"FUNC:SHAP SIN"   ! carrier waveform shape

   70 OUTPUT @Gen;"FREQ 1000"       ! carrier frequency is 1 kHz

   80 OUTPUT @Gen;"VOLT 5"          ! carrier amplitude is 5 Vpp

   90 OUTPUT @Gen;"BM:NCYC 3"       ! burst count is 3 cycles

  100 OUTPUT @Gen;"BM:INT:RATE 200" ! burst rate is 200 Hz

  110 OUTPUT @Gen;"BM:STAT ON"      ! turn BURST on

  120 !

  130 END
Using Burst Modulation to Obtain Low Duty Cycle Pulses

The Agilent 33120A has an adjustable duty cycle which ranges from 20% to 80%. However, low duty cycle pulses are often desirable. We can accomplish this using the burst mode of the Agilent 33120A. In this example, we will generate a 1 ms pulse with 100 Hz repetition for a duty cycle of 0.01%

To generate the pulse, first select the square wave and set the amplitude and offset needed for the application. To set pulse width, the appropriate frequency must be set. For a pulse width of 1 ms, use 500 kHz as the carrier frequency. To calculate this number, take the inverse of the pulse width and divide by two (a square wave has 50% duty cycle). See the equation in the diagram.

Select burst mode and set the burst rate to the desired frequency. In this example, we will use the default burst rate of 100 Hz.

For double pulses, change the burst count from the default of 1 to 2 cycles. Using Burst Modulation to Output a Continuous Waveform Upon Receipt of a Trigger The Agilent 33120A can adjust the burst count from 1 to 50,000 cycles and infinite. With the burst count set to infinite, the Agilent 33120A will output a continuous cycle when a trigger is received. Set up the Agilent 33120A with the desired carrier waveform and turn on BURST. Set the burst source (BURST SRC) to external (EXT) for the external triggered mode. Set the number of cycles in BURST CNT to INFINITE. To do this, enter the BURST CNT menu so you can adjust the number of cycles. Using the right or left arrows, move the cursor until the CYC is blinking. Press the down arrow, and the display will read INFINITE. Save the change and turn off the menu by pressing [ENTER]. This will place the Agilent 33120A in an infinite burst mode. When a trigger is received, the waveform will be continuously output.
    Revision 1.0       22 Mar 99       cld