Transmitter parameters

AN4103

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Transmitter parameters

All the measurements given in the following sections have been measured under these

The measurements concerning adjacent channel power, modulation bandwidth and

unwanted emissions in the spurious domain are given in the following sections. These

measurements have been taken according to EN 300 220 v1 [2] paragraphs 7.6, 7.7 and

7.8.

2.1

Adjacent channel power

The adjacent channel power (ACP) is defined as the amount of the modulated RF signal

power which falls within a given adjacent channel. This power is the sum of the mean power

produced by the modulation, hum and noise of the transmitter. These measurements are

applicable to narrowband systems (eg. applications or equipment) used in a non-

channelized continuous frequency band with a channel bandwidth less than or equal to

25 kHz, or systems used in a channelized frequency band with a channel spacing less than

or equal to 25 kHz.

This test measures the power transmitted in the adjacent channel during continuous

modulation. The ACP is measured with a spectrum analyzer which conforms to the

requirements given in EN 300 220-1 v2.3.1 (2010-02) [2] annex C.

In this application note the ACP measured with 12.5 kHz channel spacing is investigated.

For this measurement the integrated bandwidth of the adjacent channel is 8.5 kHz and the

ETSI limit for the ACP is 10 µW (-20 dBm).

Figure 4 and Figure 5 illustrate the measured ACP at the center frequency of 169.4 MHz.

The data rate is set to 2.4 kbps, the frequency deviation is set to 2.4 kHz, the modulation is

set to Gaussian FSK (GFSK) with a BT = 0.5 in Figure 4. The data rate is set to 4.8 kbps,

the frequency deviation is set to 1.2 kHz, the modulation is set to Gaussian FSK (GFSK)

with a BT = 0.5 in Figure 5. These modulation settings are extracted from the CEN/TC 294

prEN 13757-4:2011.10 draft version, "communication systems for meters and remote

reading of meters - Part 4: wireless meter readout (radio meter reading for operation in SRD

bands) [4]. This document describes the characteristics of the W-MBUS mode-N standard

for radio metering.

The output power integrated around the carrier is 11 dBm in the 8.5 kHz bandwidth and with

average detection. With this power the ACP is -39 dBm in the first case and -45 dBm in the

second case. The two measured values are well below the ETSI limit of -20 dBm.

SPIRIT1 is fully compliant with the ETSI transmitter adjacent channel power requirements

by a large margin.