Keysight M9290A Manual page 38

e. An ACP measurement measures the power in adjacent channels. The shape of the response versus frequency
of those adjacent channels is occasionally critical. One parameter of the shape is its 3 dB bandwidth. When the
bandwidth (called the Ref BW) of the adjacent channel is set, it is the 3 dB bandwidth that is set. The passband
response is given by the convolution of two functions: a rectangle of width equal to Ref BW and the power
response versus frequency of the RBW filter used. Measurements and specifications of analog radio ACPs are
often based on defined bandwidths of measuring receivers, and these are defined by their 6 dB widths, not
their 3 dB widths. To achieve a passband whose 6 dB width is x, set the Ref BW to be
f. Most versions of adjacent channel power measurements use negative numbers, in units of dBc, to refer to the
power in an adjacent channel relative to the power in a main channel, in accordance with ITU standards. The
standards for W-CDMA analysis include ACLR, a positive number represented in dB units. In order to be con-
sistent with other kinds of ACP measurements, this measurement and its specifications will use negative dBc
results, and refer to them as ACPR, instead of positive dB results referred to as ACLR. The ACLR can be
determined from the ACPR reported by merely reversing the sign.
g. The accuracy of the Adjacent Channel Power Ratio will depend on the mixer drive level and whether the
distortion products from the analyzer are coherent with those in the UUT. These specifications apply even in
the worst case condition of coherent analyzer and UUT distortion products. For ACPR levels other than those
in this specifications table, the optimum mixer drive level for accuracy is approximately 37 dBm 
(ACPR/3), where the ACPR is given in (negative) decibels.
h. The Fast method has a slight decrease in accuracy in only one case: for BTS measurements at 5 MHz offset,
the accuracy degrades by 0.01 dB relative to the accuracy shown in this table.
i. To meet this specified accuracy when measuring mobile station (MS) or user equipment (UE) within 3 dB of
the required 33 dBc ACPR, the mixer level (ML) must be optimized for accuracy. This optimum mixer level
is 20 dBm, so the input attenuation must be set as close as possible to the average input power  (20 dBm).
For example, if the average input power is 6 dBm, set the attenuation to 14 dB. This specification applies for
the normal 3.5 dB peak-to-average ratio of a single code. Note that if the mixer level is set to optimize
dynamic range instead of accuracy, accuracy errors are nominally doubled.
j. ACPR accuracy at 10 MHz offset is warranted when the input attenuator is set to give an average mixer
level of 10 dBm.
k. In order to meet this specified accuracy, the mixer level must be optimized for accuracy when measuring node
B Base Transmission Station (BTS) within 3 dB of the required 45 dBc ACPR. This optimum mixer level is
18 dBm, so the input attenuation must be set as close as possible to the average input power  (18 dBm).
For example, if the average input power is 5 dBm, set the attenuation to 13 dB. This specification applies for
the normal 10 dB peak-to-average ratio (at 0.01 probability) for Test Model 1. Note that, if the mixer level is
set to optimize dynamic range instead of accuracy, accuracy errors are nominally doubled.
l. Accuracy can be excellent even at low ACPR levels assuming that the user sets the mixer level to optimize the
dynamic range, and assuming that the analyzer and UUT distortions are incoherent. When the errors from the
UUT and the analyzer are incoherent, optimizing dynamic range is equivalent to minimizing the contribution
of analyzer noise and distortion to accuracy, though the higher mixer level increases the display scale fidelity
errors. This incoherent addition case is commonly used in the industry and can be useful for comparison of
analysis equipment, but this incoherent addition model is rarely justified. This derived accuracy specification
is based on a mixer level of 13 dBm.
m. Keysight measures 100 of the signal analyzers for dynamic range in the factory production process. This
measurement requires a near-ideal signal, which is impractical for field and customer use. Because field
verification is impractical, Keysight only gives a typical result. More than 80 of prototype instruments met
this "typical" specification; the factory test line limit is set commensurate with an on-going 80 yield to this
typical.
The ACPR dynamic range is verified only at 2 GHz, where Keysight has the near-perfect signal available. The
dynamic range is specified for the optimum mixer drive level, which is different in different instruments and
different conditions. The test signal is a 1 DPCH signal.
The ACPR dynamic range is the observed range. This typical specification includes no measurement
uncertainty.
38

x 0.572 – RBW
.