Rainbow Electronics MAX1213 - Manual (Page 19)

MAX1213
1.8V, 12-Bit, 170Msps ADC for
Broadband Applications
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Noise Power Ratio (NPR)
NPR is commonly used to characterize the return path of
cable systems where the signals are typically individual
quadrature amplitude-modulated (QAM) carriers with a
frequency spectrum similar to noise. Numerous such
carriers are operated in a continuous spectrum, generat-
ing a noise-like signal, which covers a relatively broad
bandwidth. To test the MAX1213 for NPR, a “noise-like”
signal is passed through a high-order bandpass filter to
produce an approximately square spectral pedestal of
noise with about the same bandwidth as the signals
being simulated. Following the bandpass filter, the signal
is passed through a narrow band-reject filter to produce
a deep notch at the center of the noise pedestal. Finally,
this signal is applied to the MAX1213 and its digitized
results analyzed. The RMS noise power of the signal
inside the notch is compared with the RMS noise level
outside the notch using an FFT. Note that the NPR test
requires sufficiently long data records to guarantee a
suitable number of samples inside the notch. NPR for the
MAX1213 was determined for 35MHz and 50MHz noise
bandwidth signals, simulating a typical cable signal envi-
ronment (see the Typical Operating Characteristics for
test details and results).
Pin-Compatible Lower
Speed/Resolution Versions
Applications that require lower resolution and/or higher
speed can refer to other family members of the
MAX1213. Adjusting an application to a lower resolution
has been simplified by maintaining an identical pinout for
all members of this high-speed family. See
Table 2 for a
selection of different resolution and speed grades.
Table 2. Selection of Lower Resolution/
Higher Speed Versions of the MAX1213
PART
RESOLUTION
(BITS)
SPEED GRADE
(Msps)
MAX1121 8 250
MAX1122 10 170
MAX1123 10 210
MAX1124 10 250