RF Equipment Usage í¬ Spectrum Analyzer

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RF Equipment Usage

— Spectrum Analyzer

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Presentation Notes

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Upon completion of this course, you will be able to:

Understand how to use a spectrum analyzer


Chapter 1 Overview

Chapter 2 Procedure

Chapter 3 Precautions


Overview Basic functions of a spectrum analyzer

A spectrum analyzer is used to test the frequency domain performance, including spectrum, adjacent channel power, fast time-domain scan, spurious emission, and intermodulation attenuation.

Common usage: testing interference

Common analyzer models: Agilent E4402 or E4404


Chapter 1 Overview

Chapter 2 Procedure



Procedure Step 1: Connect the reference source signals to a spectrum analyzer.

(Recommended) Connect an external reference with high precision of the 10 MHz clock to the [10M REF INPUT] at the bottom of the spectrum analyzer.

If no external reference is available, use the signals passing through the [10M REF OUTPUT] port of the analyzer.

− Use a short circuit module or RF cable to connect the [10M REF INPUT] port to the [10M REF OUTPUT].

If a device counter (for example, TRX) needs to be measured, input the FCLK clock output signal on the filler panel of the timing/transmission and management unit (TMU) (or MCK) into the [GATE TRIG/EXT TRIG IN (TTL)] port of the spectrum analyzer.

10M OUT 10M IN

GATE TRIG/EXT TRIG IN (TTL)


Procedure (Continued) If the external interference needs to be measured, connect the port for inputting test signals

to an antenna.

− If only the interference level needs to be tested, connect the port to an omni-directional antenna. If the interference source must be located, connect the port to a directional antenna.

If the device counters (for example, spurious emission and intermodulation) need to be measured, use an attenuator of about 30 dB to connect the signals to be measured (for example, the TX signals on the TRX) to the port for inputting test signals.

Port for connecting an antenna or a device

FREQUENCY

SPAN AMPLITUDE


Procedure (Continued)

Step 2: Switch on the analyzer. Check whether the analyzer is in work state and whether the keys work.

Step 3: After the power-on, the analyzer is in the [SPECTRUM ANALYZER] (scan) state by default. If the external interference needs to be measured, do as follows:

Press FREQUENCY. Enter the central frequency (for example, 900 MHz).

Press SPAN. Enter the scanning bandwidth.

Press AMPLITUE. Set the reference level (for example, –40 dBm).

Press MARKER. Enter the frequency signal to be queried.

− The upper right corner of the analyzer screen shows the frequency and level of the frequency number where the cursor is placed.

− Press [PEAK SEARCH] to place the cursor to the peak level value of the signal.


Procedure (Continued)

If the device counters need to be tested, do as follows: (The following example shows how to test the interference (spurious emission) of the TRX.)

Connect an attenuator to the input port. Then, connect the input port to the input port of the TRX receiver. Note that both the input ports of the main receiver and the diversity receiver can be connected to the input port of the analyzer. The BCCH frequency must be selected. Open the TRX and start the test after the TRX works properly.

Press [MODE]. Select GSM900 ANALYZER. The interface for GSM900 test is displayed.

Select Spurious Emission. The test for TRX spurious emission starts.

− If the spurious spectrum level is lower than –80 dBm, the system is normal. If the spurious spectrum level is higher than –80 dBm, the system is interfered with.

− If the interference spectrum shifts, the TRX self excitation occurs in the system.


Chapter 1 Overview

Chapter 2 Procedure



Precautions

Note specially that the maximum level of the test input port of all spectrum analyzers is always 30 dBm (1 W). Therefore, the signals to be tested must be connected to an attenuator of at least 30 dB regardless of the level of the signals. After that, the signals can be input to the spectrum analyzer for test. By doing this, the spectrum analyzer is protected even if the level of the signals to be tested is high.

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RF Equipment Usage í¬ Spectrum Analyzer

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