Agilent Technologies 85032B/E 50 Specifiche Scaricare il pdf (Pagina 231)

Theory of Operation 8712ET/ES and 8714ET/ES

System Theory RF Network Analyzers

6-16 Service Guide

RF Path of the ES Analyzer.

NOTE The following description assumes the transfer switch position is set to

provide output to the DUT through PORT 1 as pictured in Figure 6-5.

The RF output signal from the source assembly is routed through a coupler, an attenuator,

the transfer switch, and a second coupler before being output to the DUT at one of the

front panel ports.

As the RF source signal passes through the ﬁrst coupler, part of the signal is routed to the

R input on the receiver board to be used as a reference signal. The RF signal then travels

through the attenuator, transfer switch, and the second coupler to the DUT. The second

coupler samples the reﬂected signal from the DUT. For the switch position shown, the

sample of the reﬂected signal is routed to the A input on the receiver board. The signal

goes through the DUT and enters the instrument at PORT 2. The signal coming from the

DUT into PORT 2 is sampled by a directional coupler. The sample is routed to the B input

on the receiver board.

NOTE When the transfer switch position is the opposite of that shown in Figure 6-5,

the functions of the receiver inputs A and B are reversed.

Narrowband and Broadband Processing.

The other functions of the ES receiver are similar to the functions described in the

Narrowband and Broadband Processing description of the ET receiver. The operation of A,

B, R, B*, R*, X, Y detectors and the auxiliary inputs are identical.

Differences between the 50Ω and 75Ω Analyzers.

Connections for the DUT (PORT 1 and PORT 2) are available in both 50Ω and 75Ω

versions. The two versions are identical except for the following:

• the type-N connectors (PORT 1 and PORT 2)

• the cable between each type-N connector and its corresponding directional coupler

• The directional couplers for the A and B receiver inputs. For 75Ω units, the transition

from 75Ω το 50Ω occurs within the directional couplers.

Limiters.

Limiters are used to protect the circuitry on the receiver board (A5) from damage by

overpower or electrostatic discharge (ESD). The limiters are not discrete parts but are

built into the transfer switch, shown in Figure 6-5. Limiters protect the receiver board

much like a fuse: when a very high amount of power is applied to an input, the limiter

“fails” and becomes an open circuit. In actual practice, application of an excessive amount

of power to the input can cause the limiter to modify its characteristics but not become an

open circuit. In this case, the limiter may exhibit symptoms of a degraded match and/or

increased attenuation.

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Agilent Technologies 85032B/E 50 Specifiche Pagina 231