Agilent Technologies E7495A RF Bedienungsanleitung PDF herunterladen (Seite 7)

Solving the problem

The technicians used the N9340B with a directional

antenna (N9311X-504) from the N9311X RF accessory kit

to scan the uplink frequency span of 890 MHz to 915 MHz

on sector 3. They found the noise ﬂ oor between 890 MHz

and 900 MHz was much higher than the normal noise ﬂ oor

(see Figure 1).

The GSM base station was shut down for further analysis.

Technicians used the N9340B’s interference monitoring

feature (spectrogram) to continuously monitor the 870-MHz

to 915-MHz frequency and found strong CDMA-like

signals between 870 MHz and 890 MHz. Also shown on

the spectrogram was a wideband noise-like interference

at 890 MHz to 900 MHz (see Figure 2).

To see if the signals were CDMA signals, technicians used

the N9340B’s occupied bandwidth (OBW) one-button

measurement to evaluate the signals’ bandwidth. The

N9340B showed the measurement occupied bandwidth

was 1.2 MHz, which is the bandwidth of a CDMA signal

(see Figure 3).

Results

A nearby CDMA base station was found to generate the

out-of-band emissions that interfered with the GSM

base station. A report with measurement screenshots

was submitted to the two service providers to resolve

this interference issue.

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Figure 1. Noise floor for the 890

MHz to 915 MHz frequency span

Figure 2. Interference signals on

the spectrogram

Figure 3. Occupied bandwidth

reading on the N9340B

N9311X-504

directional

antenna

1 2 3 4 5 6 7 8 9 10 11 12 ... 16 17

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