Agilent Technologies Switch/Measure Instrukcja Użytkownika Pobierz pdf (Strona 4)

Introduction

This application note presents the fundamental RF parametric measurements

necessary to characterize GSM900, DCS1800 and PCS1900 base transceiver

stations and their components.

These measurements are widely used today, but new test equipment is making

them easier to perform, faster and more precise. This note aims to enhance

the reader’s understanding of GSM measurements so they can be used and

optimized appropriately. It is also intended as a useful reference for engineers

in manufacturing, research and development and field service.

As far as possible, graphics are used to represent the theory behind each

measurement and the test limits applied. For each measurement, pictorial

examples of setup, method and specification limits are given. These have

been derived from the ETSI and ANSI standards.

Why measure?

The GSM standards define a radio communications system that works properly

only if each component part operates within precise limits. Essentially a

compromise is established between the link quality experienced by an individual

user and the level of interference experienced by others. Mobiles and base

stations must transmit enough power, with sufficient fidelity to maintain a call

of acceptable quality, without transmitting excessive power into the frequency

channels and timeslots allocated to others. Receivers must have adequate

sensitivity and selectivity to acquire and demodulate a low-level signal.

Performance is critical in three areas: in-channel, out-of-channel, and out-of-band.

In-channel measurements determine the link quality seen by the user in question:

Phase error and mean frequency error

Mean transmitted RF carrier power

Transmitted RF carrier power versus time

Out-of-channel measurements determine how much interference the user causes

other GSM users:

Spectrum due to modulation and wideband noise

Spectrum due to switching

Tx and Rx band spurious

Out-of-band measurements determine how much interference the user

causes other users of the radio spectrum (military, aviation, police):

Other spurious (cross band and wideband)

Amplitude

In-channel

Out-of-channel

Out-of-band

Frequency

Figure 1. In-channel, out-of-channel, out-of-band measurements

1 2 3 4 5 6 7 8 9 ... 35 36

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Agilent Technologies Switch/Measure Instrukcja Użytkownika Strona 4