Pulse Generator Programming Channel Rates

Application Note Title: Individual Channel Rates
Revision #: 1.00


Scope:
This application note explains how a user can produce outputs of different rates from a
Quantum Composers pulse generator by utilizing the `Duty Cycle' mode. Two different
approaches will be explained; the first is a quick and dirty process that allows a novice user to
get the correct setup, while the second approach goes into greater detail about the math behind
the process.


Body:
This application note is written with the assumption that the user understands the basic features
and functionality of the Quantum Composers pulse generators. If after reading this app note
there is confusion on how to access and adjust such features as Period, Duty Cycle, the number
of On/Off pulses or how to verify the output rate for each channel feel free to contact Quantum
Composers technical support.

1st Approach
Set the To Period of pulse generator to 1us. Set channel mode to `Duty Cycle' with an `On'
pulse count of "1". Next take the desired frequency channel output and turn it into a
microsecond time base (round to the nearest microsecond); subtract 1 from this number and this
gives the number of duty cycle `Off" pulses needed to achieve the desired output frequency for
that channel. For example:

Example
Channel
Mode
Duty
Cycle
On
Pulses
count
1
To (period)




0.000001 seconds (1 MHz)
Desired channel frequency output

120Hz

Equivalent microsecond time base
1/120Hz = 0.00833333 sec = 8333us
Number of `Off Pulses'


8333 - 1 = 8332 (Off Pulse count)

This setup will give the desired channel frequency of 120Hz. This easy approach to individual
channel rates is good for outputs of 1 MHz and slower. To accomplish faster output rates see
the 2nd Approach.

2nd Approach
Set the channel mode to `Duty Cycle' an `On' pulse count of "1". Set the To at the desired
period; for fastest and most accurate individual channel output frequencies set the period to the
highest rate. Next take the desired frequency channel output and turn it into a second time base;

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round this number to nearest significant digit as dictated by the To period in seconds. Take this
number and divide it by the To time base (in seconds) and round it to the nearest whole number;
subtract 1 from this number and this gives the number of `Off' pulse counts. The following are
a couple of examples:

Example 1
Channel
Mode
Duty
Cycle
On
Pulses
count
1
Example
To
selection
0.00000005
seconds
Desired channel frequency output

120Hz

Equivalent microsecond time base
1/120Hz = 0.00833333 seconds (rounded)
Number of `Off Pulses'


0.00833333 / 0.00000005 = 166667 rounded
calculations
continued
166667
-
1
=
166666 (Off Pulse count)

Example 2
Channel
Mode
Duty
Cycle
On
Pulses
count
1
Example
To
selection
0.0000002
seconds
Desired channel frequency output

300kHz

Equivalent microsecond time base
1/300kHz = 0.0000033 seconds (rounded)
Number of `Off Pulses'


0.0000033 / 0.0000002 = 17 rounded
calculations
continued
17
-
1
=
16 (Off Pulse count)

Note that the output frequencies cannot be faster than the To frequency. It can also be noted
that the math behind the two approaches outlined in this application note is the same. However,
keeping the period set at 1MHz, as described in the 1st approach, and changing to the desired
output frequency into microseconds allows for simpler math.

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