Education Library

Frequently Asked Question

What type of frequency sweeping is available?

There are several types of frequency sweeping available:

Linear ramp with defined endpoints - (commonly called ramped FSK). The user is able to program a beginning and terminating frequency. The user can then specify an incremental frequency and the rate at which to increment the frequency. Upon reaching the terminating frequency the device may either hold the terminating frequency value (standard), or return to the starting frequency instantaneously (return-to-zero).

Linear sweep with no defined endpoints - As with ramped FSK, the user can specify an incremental frequency value and the rate at which to increment the frequency. However, as there are no defined endpoints, once the sweep begins, it only stops when the user indicates a stop, either via a pin control (HOLD pin on AD9852) or by writing to one of the registers a zero value. The user can also clear the "Linear Sweep Enable" bit in the control register for the device, but this clears all information from the linear sweep registers, and the frequency immediately returns to the value stored in the frequency tuning word of the active profile.

RAM modes of operation - The AD9953 and AD9954 include a 1024x32 RAM which can be programmed by the user. The values stored in the RAM can be used as frequency tuning words. Please see the AD9953 or AD9954 datasheets for more details of the RAM sweep modes of operation.