M a k i n g M e a s u r e m e n t s U s i n g S p e c t r u m A n a l y z e r M a d e

Using the Time-Gated Spectrum Analyzer Capability Without the Gate Utility (Option 107 only)

Use the guidelines in 7Able 5-l when using time-gated spectrum analyzer capability to view a pulsed RF signal. These are only guidelines, and the spectrum analyzer settings can be changed if necessary.

Table 5-1.

Determining Spectrum Analyzer Settings for Viewing a Pulsed RF Signal

Spectrum Analyzer

 

Spectrum

Analyzer

Setting

 

Comments

 

Function

 

 

 

 

 

 

 

 

 

 

 

 

 

S w e e p T i m e

Set the sweep time to be 401 times greater

Because the gate must be on at least once

 

 

than the pulse repetition interval IPRII:

per trace point, the sweep time has to be

 

 

 

 

 

 

 

 

 

 

 

 

 

set to the pulse repetition interval times for

 

 

S w e e p

t i m e

> 4 0 1 x

PRI

 

 

 

every point of the trace. IEach trace has

 

 

 

 

 

 

 

 

 

 

 

 

 

401 points.)

 

 

 

 

 

 

 

 

 

 

 

Gate

Delay

The gate

delay

is

equal

to the

signal delay

The gate delay must be set so that the

 

 

plus half of the pulse width:

 

 

gating captures the pulse. If the gate delay

 

 

 

 

 

 

 

 

 

 

 

 

 

is too short or too long, the gating can mist

 

 

G a t e

D e l a y =

S i g n a l D e l a y

+

r/2

the pulse or include resolution bandwidth

 

 

 

 

 

 

 

 

 

 

 

 

 

transient

responses.

 

 

 

 

 

 

 

 

 

 

 

Gate

Length

The gate

length

is

equal

to

one-fourth the

If the gate length is too long, the signal

 

 

pulse

width:

 

 

 

 

 

 

 

 

display can include transients caused by the

 

 

 

 

 

 

 

 

 

 

 

 

 

spectrum

analyzer filters.

 

 

G a t e

l e n g t h =

r/4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Video

Bandwidth

S e t t h e

v i d e o

b a n d w i d t h t o

a

v a l u e g r e a t e r

T h e v i d e o

b a n d w i d t h m u s t b e w i d e e n o u g h

 

 

than 1 divided by the gate length:

so that the rise times of the video

 

 

 

 

 

 

 

 

 

 

 

 

 

bandwidth do not attenuate the signal.

 

 

V i d e o

B a n d w i d t h >

gate ,!englh

 

 

 

 

 

 

Resolution Bandwidth

Set the resolution bandwidth to a value

The resolution bandwidth must be wide

 

 

greater then 2 divided by the gate delay

enough so that the charging time for the

 

 

minus

the signal

delay:

 

 

 

 

resolution bandwidth filters is less than the

 

 

 

 

 

 

 

 

 

 

 

 

 

pulse width of the signal.

 

 

R e s o l u t i o n B a n d w i d t h >

 

 

 

 

 

 

 

 

 

 

 

 

2

 

 

 

 

 

 

 

 

 

 

G a t e D e l a y - S i g n a l D e l a y

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5-39