Electro-Metrics EM-2115, Instruction Manual

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EM-2115 APPENDIX C FUNCTION AND DESCRIPTION
(EM2115C-1)
APPENDIX C
EM-2115
FUNCTION AND DESCRIPTION
C-1.0 Introduction
This section contains a brief description of unit and circuitry function for the EM-2115
Interference Analyzer.
C-2.0 Synopsis Of Receiver Operation
The EM-2115 Interference Analyzer is a medium range EMI/RFI receiver operating from
9 kHz to 1 GHz.
A built-in microprocessor controls the operation of the receiver from information keyed
in via the front panel controls. The receiver can also be controlled using an external computer via
the rear panel IEEE-488 General Purpose Interface Bus (GPIB).
The receiver is divided into three major sections: RF Tuner, IF Amplifier, and Detection
circuitry.
An RF signal between 9 kHz and 1 GHz is applied to the RF Tuner through a 1 GHz low
pass filter and a 0 to 100 dB RF input attenuator. Depending on the frequency of the input signal,
the RF Tuner produces one of three IF outputs (175 kHz, 1.6 MHz, 8.7 MHz). A Preamplifier
circuit pre-amplifies and for three frequency ranges (0.070-0.150 MHz, 0.120-0.250 MHz, 0.250-
0.500 MHz) down-converts the IF from 1.6 MHz to 175 kHz.
The IF Amplifier circuitry amplifies the selected IF output plus shapes and sets the band-
widths for the receiver.
The amplified and bandwidth defined IF signal is applied to a logging circuit that produc-
es a logged DC output of the IF signal (AM Video). In addition, the logging circuit also produces
a limited IF output that is applied to the Discriminator Module.
The AM Video signal is applied to the Detector Board that produces the peak, quasi-peak,
average (carrier), rms, and slideback outputs for the front panel digital and analog meters, X-Y
recorder, and oscilloscope presentations.
The limited IF output applied to the Discriminator Module produces the FM Video output
used by the AFC circuitry, FM Audio output, and external FM Video output.