Tektronix CMD 80, User Manual

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CDMA: Manual Test (Signaling)
CMD 80 Digital Radiocommunication Tester User Manual
3–25
H
AWGN LEVEL (Additive White Gaussian Noise Level). This option
provides additional noise to more closely simulate actual operating
conditions. The tester displays the AWGN LEVEL softkey when the optional
AWGN system is installed. Press the AWGN LEVEL softkey to adjust the
level of the AWGN generator. Press the ON or OFF front-panel keys to turn
the AWGN generator on or off.
The tester’s additive white gaussian noise (AWGN) signal is a calibrated,
wideband (1.8 MHz) signal simulating white noise. The AWGN power is
measured across the entire 1.8 MHz bandwidth. In some tests, such as those
specified in IS-98, the described noise power is measured across the
1.23 MHz bandwidth of the CDMA signal. To use the tester’s AWGN signal
for these types of tests, you must set the AWGN level 1.1 dB higher than
specified in IS-98 to compensate for differences in bandwidth.
For example, in IS-98, section 9.3.3, Demodulation of Forward Traffic
Channel in Additive White Gaussian Noise, the specification indicates that
the total AWGN power should be 1.0 dB greater than the total forward traffic
channel power. This specification assumes that the AWGN power is
measured in a 1.23 MHz bandwidth. Since the tester uses a 1.8 MHz
bandwidth to measure its AWGN power, you must compensate for the
difference in noise measurement bandwidth by setting the AWGN level in
the tester 1.1 dB higher than the value specified in the IS-98 test specifica-
tion.
In this example, where the IS-98 specification calls for a 1.0 dB greater
AWGN level than the forward traffic channel level, you must set the tester’s
AWGN setting to 2.1 dB (the 1.0 dB from the IS-98 specification plus
1.1 dB for bandwidth compensation).
NOTE
. The total output power of the tester is the sum of the Forward CDMA
signal plus the AWGN signal. When the Forward CDMA signal is within 10 dB
of its maximum power output, the AWGN signal is turned off. Once the Forward
CDMA signal is no longer within 10 dB of its maximum power, the AWGN signal
level may be set to a new value.
H
Base station carrier frequency offset. Press the BS CARRIER FREQ
OFFSET softkey to enter the frequency offset by which you want to shift the
base station carrier. This allows you to test if the mobile station tracks the
base station frequency.
H
Defaults. Press the DEFAULTS softkey to set all the parameters to their
preset conditions (typically, the default values are based on IS-98 specifica-
tions).