Atec PMM-9010_9030_9060 - Manual (Page 12)

After the A/D conversion the behaviour
of a regular receiver is mathematically
simulated in order to perfectly match
international standards specifica-tions.
Even for a digital architecture,
preselector filters and input attenuators
are mandatory for limiting the signal
energy into well defined RF bands, to
improve the dynamic range and to
increase the signal to noise ratio, thus
ensuring accurate measurements of all
wideband complex signals typical of
EMC measurements.
The input attenuator provides the
maximum dynamic range with no
distortion. This is particularly important
in conducted tests where overloading
signals may be present outside the
frequency band under test.
To prevent this from happening, the
PMM 9010’s input attenuator is directly
controlled by the DSP in wideband
mode to maintain the response
linearity in any conditions and also to
protect the RF input from out-of-band
signals that are too high.
No calibrations and no adjustments are
required after the A/D converter: CISPR
IF filters and detectors are all
mathematically calculated and are thus
not subject to any degradation for the
life of the instrument. This high
performance digital architecture features an ultra-fast A/D converter
with the DSP controlling 3 more
processors for different functions: RSP,
FPGA, CPLD.
The ADC is followed by the Receiver
Signal Processor - RSP - that performs
most of the analogue-like functions of
the receiver and handles all the
numeric signals within the digital IF,
with the main advantage of this
solution directly deriving from the
perfection of the mathematic
approach: the computing function is
equivalent to conventional analogue
mixers, but simply cannot generate
spurious components which are
therefore absent.
The sampled signals are processed by
the RSP in a purely mathematical
“mixer-like mode”, and then applied to
FIR (Finite Impulse Response) digital
RBW filters: the result is an unbelievably
stable filter, a shape controlled to
perfection as it is mathematically
modelled. Adjustments needed by
analogue filters are simply not required.
One of the fastest available DSP not
only controls the RSP, but also performs
all of the calculations and signal
processing,
like simultaneous
detections and graphical
representation, in real time; it controls
other functions like the frequency
sweep, etc.
The DSP simultaneously applies the
mathematical algorithms correspon-
ding to the detectors Peak, CISPR Quasi-
Peak, RMS, Average, RMS+AVE whose
response is no longer depends on the
input signals, as the detectors always
work exactly as intended in perfect
time coherent measurements.
Thanks to the high number of
operations performed by the DSP -
equivalent to those of an ideal 10 GHz
Pentium 4™ - the DSP also manages the
different operating modes:
Sweep
Mode, like a traditional receiver with
CISPR Limits stored in non-volatile
memory, Spectrum and Manual Mode.
The Spectrum Mode allows the receiver
to perform spectrum analyzer
functions, and thanks to the very high
scan speed (<100 ms for full-span 9
kHz-30 MHz @ IF resolution 300 kHz) it
is very useful for any kind of debugging.
In Manual Mode the filter in CISPR
bands is selected automatically
according to the frequency and the
data are displayed with a dynamic
range up to 120 dB, and the hold time is
exactly the integration time
theoretically required by the applied
detectors.
Moreover, hold time means that the
receiver really stops for the preset time,
Operating Principles of the
PMM 9010-PMM 9030-PMM 9060
Perfect, life-long stable and calibration-free RBW filters
(picture: 200 Hz RBW CISPR filter)