BIRD 5012D, Руководство по эксплуатации

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Wideband Power Sensors
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CCDF measurements are most useful for pseudo-random signals, such as
WCDMA, where a high CCDF means that the transmitter is being overdriven.
CCDF can also detect amplitude distortion within an envelope caused by
unwanted modulating signals. In TDMA systems, CCDF indicates the health of
power amplifier stages and their ability to sustain rated power over an
appropriate time frame. As a trouble-shooting aid, CCDF allows tracking of
trends such as amplifier overdrive (which can cause dropped calls and high bit
error rates).
Low Repetition Rate Waveforms
Many of today's channel access methods involve the use of low repetition
frequency time division-multiple access (TDMA) techniques. Examples of these
relatively new TDMA formats include Digital Mobile Radio (DMR), and TETRA
systems. The DMR format uses an approach where two discrete time slots
provide access to a single 25 kHz communication channel, providing the
equivalent of 12.S kHz channel bandwidth for the system. The modulation
techniques used within these systems vary, from relatively benign forms of
frequency shift keying, to more complex quadrature formats such as
Quadrature Phase Shift Keying (QPSK).When measuring the power output of
transmitters using the DMR format, the base station transmitters will normally
transmit with both time slots active, even if there is no traffic on one of the time
slots. Under these conditions, it is a simple matter to measure the average
power of this continuous waveform. When measuring the output power of
subscriber units however, normal operation is to use only one time slot,
approximately 30 ms in duration, followed by approximately 30 ms at zero
power in the interval where the other time slot would normally be located. The
remaining waveform resembles a 30 ms burst, occurring at a 17 Hz repetition
rate. Since the measurement of average power under this condition would
result in an unstable reading, the correct measurement would be that of burst
average power. When making this measurement, the sensor will measure the
duty cycle of the signal, as well as the average power, and compute the burst
average power of the waveform based upon these parameters.
Figure 6 Low Rep Waveform