The Sampling Frequency Dialog lets you set the sampling frequency, and the corresponding frequency/time unit names. You can set the sampling frequency via any of the following:

• Selecting Sampling Frequency from the FIR menu
• Hitting the Design Options button
• Selecting Design Options from the FIR menu

The sampling frequency essentially is a scaling factor for all other frequencies. You can work in any frequency scaling so long as you are consistent. Therefore, for example, you might choose to represent 1 kHz as either 1.0 (kHz) or 1000 (Hz). But if you specify a sampling frequency of " 1.0" to represent " 1 kHz" , you should enter " 0.1" when you wish to represent " 100 Hz" . We suggest you choose the sampling frequency scaling based on whatever is easy to think about ,and whatever is convenient to type.

Enter the numerical frequency in the left box. The default sampling frequency is 1.0.

Frequency and time units are shown on various graphs and displays throughout the program, notably on the button in the upper right of each  design editor. This is merely a user convenience: the program uses only the numerical sampling frequency for calculations. The frequency and time units also can be dimensionless, which is the default. Select the units for frequency and time from the list on the right. The time unit is always the reciprocal of the frequency unit. For example, if the frequency unit is MHz (MegaHertz) the time unit is us (microseconds). A list is provided of common frequency units, with their corresponding time units. If your application uses units which are not provided, you may enter custom units using the format frequency, time. (A comma delimits the frequency unit from the time unit.)