NARDA PMM ER9000, User Manual

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3-10 Operating Instructions
3.2.3.1 Detectors
PMM ER9000 has been designed to allow the use of many kinds of detectors.
CISPR Standard has introduced the application of two detectors that are
derived from the Root Mean Squared and from the Average ones.
3.2.3.2 RMS-AVG
Definition The RMS-Average detector is a special function, defined by the CISPR
standard, implemented in the PMM ER9000 receiver.
The RMS-Average detector, according to the CISPR 16-1-1 standard, supplies
a reading of the input signal that is weighted, for repeated pulses, such that for
a constant indication, the relationship between amplitude and repetition
frequency is in accordance with the following rule:
The Amplitude is proportional to (repetition frequency)-1/2
The value is the maximum level during the measurement time (Hold Time) and
the averaging is carried out with a lowpass filter of the 2
nd
order to simulate a
mechanical instrument.
The calibration is in reference to the RMS value of an unmodulated sine wave
signal.
3.2.3.3 C-AVG
Definition
CISPR 16-1-1 defines the Average detector as designed to give the maximum
value of the weighted average value of the envelope of the signal passed
through the pre-detector stages.
The detector is used, for example, to measure pulsed sinusoidal signals with a
low pulse repetition rate, what the standards refer to as intermittent, unsteady
and drifting disturbances.
The measurement result of the response to intermittent, unsteady and drifting
narrowband disturbances must be equivalent to the peak reading of an
instrument with a meter time constant, independent of the observation time
(Hold time), of 160 ms for Bands A and B, and of 100 ms for CISPR Bands C,
D and E. A meter-simulating network following the envelope detector of the
receiver can accomplish this.
The average detector is useful to measure narrowband signals, to overcome
problems associated with either modulation content or the presence of
broadband noise.
When the Average is measured according to CISPR 16-1-1, the maximum
value of the linear mean envelope during the measurement interval is shown.