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87050A Option K24
Theory of Operation
Theory of Operation
The theory of operation begins with a general description of the 87050A Option K24
Multiport Test Set. This is followed by more detailed operating theory. The operation of
each group is described briefly, to the assembly level only. Detailed component level circuit
theory is not provided.
System Theory
The test set consists of three main components: a power supply, a front panel display and a
controller interface mother board. The purpose of the power supply is to provide power to
both the front panel display and the main switch board. The front panel display serves to
indicate the switching paths to the user. The controller interface mother board does the
actual switching between the different ports.
A1 Power Supply
The switching power supply provides regulated dc voltages to power all assemblies in the
test set. A dc cable provides power to the main switch board. A connector from the main
switch board to the front panel display provides dc power and control signals to the front
panel. The power supply provides the following voltages: +24V, +12V, and +5V.
The power LED on the front panel indicates that the instrument is on and that the power
supply is providing power.
A2 Front Panel Display
The front panel display consists of an LCD. The LCD is divided into two lines, forward and
reverse. The first line indicates which of the 24 ports is connected to the forward path. The
second line indicates which of the 24 ports is connected to the reverse path. Control signals
and dc power are provided by a cable connected to the main switch board.
A3 Controller Board (Mother Board) and Switch Driver Board
(Daughter Board)
Refer to
Figure 13 on page 50
for the following discussion. The mother and daughter board
provide the bias to switch the paths of the various ports to the Transmission and Reflection
ports. The front panel display contains an LCD that indicates the switched ports. A
particular test port (1 thru 24) can be in one of the following three states:
• Switched to the forward path
• Switched to the reverse path
• Terminated in 50 Ω
When a port is not connected, it is automatically terminated in 50 Ω.
The test set consists of twenty four 1×2 switches, eight 1×6 switches, and two 1×4 switches.
The 1×2 switches divide each of the input ports (1 thru 24) into two separate paths, the
Transmission path or the Reflection path.
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User's and Service Guide
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Troubleshooting
