AN4117

Transmitter parameters

Doc ID 023222 Rev 1

7/22

2

Transmitter parameters

All the measurements here reported are performed with the following parameters: Tc = 25

°C, Vdd = 3.0 V, f = 434.030 MHz. They are also measured with the reference design

reported in EN 300 220 v1 [2] Annex A.1.

The modulation bandwidth, adjacent channel power, and unwanted emissions in the

spurious domain measurements are here reported. The measurements are realized

according to EN 300 220 v1 [2] sections 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. This measurement is

applicable only to narrowband systems.

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, ACP measured with 12.5 kHz and 25 kHz channel spacing are

investigated. For these measurements the integrated bandwidths of the adjacent channel

are 8.5 kHz and 16 kHz respectively. The ETSI limit for the ACP is 10 µW (-20 dBm) for 12.5

kHz channelization and 200 nW (-37 dBm) for 25 kHz channelization.

Figure 4 and 5 illustrate the measured ACP at the 434.3 MHz center frequency with 12.5

kHz channelization, Figure 6 illustrates the measured ACP with 25 kHz channelization. The

data rate for the modulated signal in Figure 4 is set to 1.2 Kbps, the frequency deviation is

set to 1 kHz, and the modulation is set to 2-FSK. The data rate for the modulated signal in

Figure 5 is set to 2.4 Kbps, the frequency deviation is set to 2.4 kHz, and the modulation is

set to Gaussian FSK (GFSK) with BT = 0.5. The data rate for the modulated signal in

Figure 6 is set to 4.8 Kbps, the frequency deviation is set to 2.4 kHz, and the modulation is

set to Gaussian FSK (GFSK) with BT = 0.5.

The output power integrated around the carrier is 12 dBm in the bandwidth and with average

detection. With this power the ACP is -38 dBm in the first two cases and -43 dBm in the third

case. The SPIRIT1 is fully compliant with the ETSI transmitter adjacent channel power

requirements with margin.