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Spurious

Purpose of measurements—what they prove

Spurious measurements are necessary in all radio communications systems, and

in GSM they are extensive. For correct operation GSM transmitters must not

put energy into the wrong parts of the spectrum. If they do, other users of the

GSM system may experience interference and worse still, other users of the

radio spectrum (for example, police, television, commercial radio, military and

navigation) will experience degraded, or even jammed links.

Almost any fault in the transmitter circuits can manifest itself as spurious of one

kind or another.

The spurious measurements discussed in this section are those defined as

“conducted.” These specifications apply when the test instrumentation is

connected directly to the device under test antennae connector. The ETSI and

ANSI standards also defined a large number of measurements for “radiated”

spurious. These are not covered in this note.

For the purposes of clarity, in terms of representing the specifications, this

section is broken down as follows:

Tx and Rx band spurious Spurious that affect the system of interest.

Cross-band spurious Spurious that affect other GSM systems

operating at different frequencies

(GSM900 into DCS1800).

Out-of-band spurious Wideband spurious that affects other users

of the radio spectrum.

All of the spurious measurements are defined in ETSI and ANSI specifications

as standard spectrum analyzer measurements, that is, a band is swept (with

certain filter/speed settings) and a pass/fail limit applied.

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