Agilent Technologies 1912A Manual do Utilizador descarregar pdf (Página 2)

Calibrator

HI-path

LO-path

ADC

The N1913/1914A operation block diagram shown in Figure 2 is applicable to

all Agilent power meters. The meter works with both thermocouple and diode

detector mounts, providing accurate RF average power measurement. The

sensor converts the high frequency power to a DC or low frequency signal that

the meter can then measure and relate to a certain RF power level.

The DC or low frequency signal from the sensor will be chopped, ampliﬁ ed

in AC-coupled system, and sent to the meter through the sensor cable. This

process is necessary because it is difﬁ cult to transmit the DC signal across the

cable, as the external DC noise will be easily coupled into the original signal.

The chopper and AC ampliﬁ er are embedded in the sensor itself. In the meter,

the chopped signal is synchronously detected, de-chopped, and ampliﬁ ed again.

The calibrator precisely calibrates the signal measured by the meter to a power

reference level.

The signal is fed into one of the multi-path blocks after the calibration process.

Since most of the Agilent power sensors come with multi-path design, the

low path and high path require different gain adjustments for accurate signal

measurements. The signal will then be routed to data acquisition where

the analog-to-digital converter (ADC) will execute the digital sampling. The

essential measurement task is mostly done by the DSP. The microprocessor

is the heart of the whole power meter operation, supervising not only data

acquisition portion but also all the external interfaces (such as keypad input)

and connectivity (remote communication and external triggering).

N1913/1914A

Operation Overview

Sensor

Sensor control

Ampliﬁ er

Data acquisition

Memory

DSP

LCD and front panel

Figure 2. Operation block diagram of N1913/1914A

Microprocessor

Chopper

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Agilent Technologies 1912A Manual do Utilizador Página 2