User`s guide

10 User’s and Service Guide Supplement

E4438C Option HEC

Repeatable Triggering for Multiple Baseband Sources

Trigger using External Clock

The following section introduces a technique using the internal baseband generator (phase

coherent with the external clock) that will allow < ± 0.5 ns timing resolution. By using the

internal Marker

functions, Event

output connectors, Pattern Trigger In connectors in the

standard arbitrary waveform generator, and designating one unit as the “Master” and the

other as the “Slave” unit, the overall jitter can be reduced to ± 0.5 ns or less. The Marker

function will output a transitional level that corresponds to a specific point of the sampled

waveform and an opposite transitional level corresponding to another specific point in the

sampled waveform. For instance, if the sampled waveform had 200 points and the first

point selected using Marker 1 was #10, and the second point selected was #50 then the

output at the Event 1 would show a transitional level starting at the 10

point and an

opposite transitional level at the 50

point. The transitional level is a 3.3 V CMOS high

output when positive polarity is selected and a 3.3 V CMOS low output when negative

polarity is selected.

The “Master” unit will output on the Event 1 output connector and the “Slave” unit will be

triggered using the Pattern Trigger Input. This will insure that both units are

synchronized together with minimal jitter since the “Master” unit is using the external

clock as a reference signal through the Event 1/Pattern Trigger In to synchronize both

units. Insure that the External Clock used to synchronize the two E4438C Option HEC

units is stable. This will be the determining factor in the integrity of the ARB output

waveforms.

The expected frequency range of the External Clock is 200 MHz to 400 MHz. The E4438C

Option HEC sample rate is equal to the External Clock divided by 4. This means that if the

sample rate can be selected between the frequency range of 50 MHz and 100 MHz.

As mentioned in the previous section, each I/Q input has DACs that will settle on a

random state that may introduce errors into the measurement. The Align DAC function

will need to be utilized in both E4438C Option HEC units (Master then Slave) to insure

that each I/Q set is aligned to reduce any time skew. The following sections contain the

procedure to setup triggering using the external clock.

1. Refer to the E4438C User Guide regarding Marker Functions and Event 1 output connections.