2

84904 with a 10 dB step 84906 or

84907 to cover an attenuation range

of 121 dB or 81 dB in 1 dB steps.

Individual calibration data reports of

attenuation and SWR are available.

This data, measured with an Agilent

automatic network analyzer, can be

ordered as Option 8490XX-UK6.

Attenuation switching and control

These units feature the same

small solenoids and switching circuits

as the Agilent Technologies

8494/5/6/7 step attenuator family.

Switching time is a maximum of 20

milli-seconds, including contact set-

tling time. Once switched, the units

are latched with permanent magnets,

capable of withstanding shocks over

10 Gs. The solenoids automatically

disconnect after switching, which

minimizes the attenuators’ power

requirements and simplifies the driv-

er circuit design (figure 3). Solenoids

are available in either 24 volt (stan-

dard, Option 8490xx-024), 15 volt

(Option 8490xx-015), and 5 volt

(Option 8490xx-011) ranges to fit

your instrument or system

requirements.

The units come equipped with 10-pin

DIP headers for connecting dc control

lines. Available accessories include a

203 mm (8 inch) or 406 mm (16 inch)

ribbon cable with DIP-type connectors

that is compatible with standard 14-

pin DIP IC sockets (11764-60002 or

11764-60003, respectively). Altern-

atively, a 1524 mm (5 foot) cable with

free wires for direct soldering (11764-

60001), or a 1524 mm (5 foot) drive

cable that connects to the 11713B/C

attenuator/ switch driver, allowing for

easy integration into GPIB-controlled

automatic test systems (11764-60004),

may be ordered.

Selection switching

Figure 2 shows one attenuator sec-

tion schematic. Each section utilizes

one solenoid with dual coil windings,

one coil to switch in the attenuator

card (e.g. 10 dB) and one coil to

switch in the thru line (0 dB).

Figure 2. Section electrical diagram

With positive voltage applied to the

common pin, the state (attenuator

card or thru line) of a particular sec-

tion is determined by connecting its

attenuator card pin or thru pin to a

negative voltage or ground. Figure 4

defines the pin assignments and wire

color code for the 11764-60001/60002/

60003 drive cables. Table 1 is a sole-

noid drive pin and attenuation guide.

Table 2 (on page 4) defines recom-

mended attenuator section activation.

As a section is switched, the internal

contacts of the activated coil open,

thus shutting off current flow. At the

same time, the internal contacts for

the other coil close so that it can be

activated when desired. Figure 3

shows a section that has been

switched to the attenuator card posi-

tion (note the closed thru line coil

contact). The switching is “break-

before-make” type, thus a momentary

interruption of the RF signal occurs

at switching.

Although all sections can be switched

simultaneously, the attenuator driver

must not allow both pins of the same

section (e.g. Section 1, pins 1 and 2)

to be activated concurrently, or else

that section would cycle rapidly. All

terminals are “floating,” so bipolar or

unipolar power supplies can be used.

Typical

External

Driver

RF Input

Attenuation

Card

To next

Section

RF to

next Section

of Output

RF Connector

Drive Pin

(e.g., pin 6)

Internal

Coil Contacts

Thru Line

Pin

(e.g., pin 5)

LED Indicator Circuit

Switch Driver Circuit

+5V

+5V

+24V

Inverter

LED

TTL Input

Driver

4.22K

Internal

Coil Contacts

0.62K

0.13K

5082-4880

(DM7406N*)

B

D

4.22K

Drive

Cable

Thru Line

Drive Pin

To next Section

Attenuator Section

RF

Connector

Drive Pin

RF In

Attenuation Card

RF to next

Section

or Output

Thru Line

0.62K

TTL Output

TTL Indicator Circuit

Inverter

A

(DS75452N*)

(DM7404N*)

*Fairchild Semiconductor

part numbers, also supplied

by other vendors:

NOTE: Additional circuit

design information may

be required from the

component manufacturers.

Figure 3. Driver and indicator circuits for one section of an Agilent 84904, 6, 7 K/L