Fast-switching synthesizers serve a wide range of measurement applications, including evaluation of frequency-hopping systems (such as Bluetooth) and testing of components and systems, such as antennas, requiring many test points. The PTS series of frequency synthesizers from Programmed Test Sources (Littleton, MA) have long been known for their outstanding performance in terms of spectral purity and frequency agility when switching under binary-coded-decimal (BCD) remote control. They now add list-mode switching capability under GBIB command, greatly increasing their flexibility in automatic-test-equipment (ATE) systems requiring frequency-hopping or frequency-agile testing.

The PTS synthesizer line includes the PTS 3200 and PTS 6400 (see figure). The former tunes from 1 to 3200 MHz while the latter operates from 1 to 6400 MHz. Both are based on high-speed direct-synthesis techniques that deliver frequency-switching speeds of only 20 µs—and now those switching speeds are available by means of either BCD or list-mode GPIB operation.

Under standard GPIB operation, data-processing delays amount to about 5 ms switching speed for one of the synthesizers to settle to a new frequency after receipt of a GPIB control. But in the List mode of operation, a predefined list of frequency, amplitude, and phase settings is sequenced from internal memory and executed by the PTS frequency synthesizer with microsecond switching speed. For lists of as many as 128 settings of frequency, phase, and amplitude operating with an external trigger, the switching speed is basically the inherent switching speed of the synthesizer (about 20 µs).

For longer lists of as many as 2000 settings, the worst-case switching speed with an external trigger is 250 µs, including a 20-µs internal settling time. The list processing subsystem (available as an option) within each PTS frequency synthesizer allows operators to set the number of frequency points, the number of phase points, the number of output power levels, and the dwell time between switched points.

The List mode frequency/phase/amplitude switching capability is available on most PTS frequency synthesizers, a line that includes models ranging from the 0.1-to-40-MHz model PTS 040 to the 1-to-6400-MHz model PTS 6400. Programmed Test Sources, Inc., 9 Beaver Brook Rd., P.O. Box 517, Littleton, MA 01460; (978) 486-3400, FAX: (978) 486-4495, e-mail: sales@pro grammedtest.com, Internet: www.pro grammedtest.com.