AN4133

Transmitter

Doc ID 023362 Rev 1

11/35

3

Transmitter

All the measurements given are measured under the following conditions: Tc = 25 °C, Vdd =

3.0 V, f = 922 MHz (middle frequency of the bandwidth used), unless otherwise specified.

The maximum output power of the SPIRIT1 in this band is 10 dBm, so all the measurements

for the convenience radio stations and low-power radio stations with +24 dBm or +13 dBm

output power will be performed at +10 dBm. Low-power radio stations with output power of 0

dBm will be performed with the correct output power.

A radio channel consists of up to 5 consecutive unit radio channels which are defined such

that their center frequency is located from 920.6 MHz to 923.4 MHz with 200 kHz separation

and a bandwidth of 200 kHz. SPIRIT1 fully supports the center frequency, separation and

bandwidth requirements. No measurement in that sense will be done.

There aren't specific requirements for the modulation method, while the permissible value

for the occupied bandwidth is (200 x n) kHz or less, where n is the number of unit radio

channels constituting the entire radio channel and is an integer from 1 to 5. The

measurement in this case will be done with a GFSK (BT = 0.5) modulation with 100 kbps

data rate, 50 kHz frequency deviation. Different combinations of modulation, data rate and

frequency deviation creates signals that have a bandwidth lower than 200 kHz: a specific

check has to be done for each case.

There are no specific requirements in the standard about setting the detector, resolution

bandwidth (RBW) or video bandwidth (VBW) of the spectrum analyzer. The detector will be

set to peak, the resolution and video bandwidths will be set sufficiently large to ensure the

correctness of the measurement, and the display will be set to peak hold.

3.1

Adjacent channel leakage power

The adjacent channel leakage power 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.

Different masks are defined for the two types of operating modes. For the convenience radio

stations the masks given in Figure 4 and 6 are defined. The first one defines the channel

mask of a radio channel whose frequency is from 920.5 MHz to 922.3 MHz. The second one

defines the channel mask of a radio channel whose frequency is from 922.3 MHz to 923.5

MHz. The max output power permitted for the convenience radio station is 250 mW (+24

dBm), the SPIRIT1 doesn't support this output power, so the mask compliance is verified

with an output power of 10 dBm. An external PA should be used to reach the maximum

output power.

Figure 5 and 7 show the compliance measurement with the two masks and that the SPIRIT1

complies. If an external power amplifier is used to burst the output power to +24 dBm a

verification of the channel masks has to be done. If the mask requirements aren't met, a

reduction of the data rate and/or frequency deviation is necessary.

For the low-power radio stations the masks printed in Figure 8, 10, 12, 14, and 16 are

defined.

Figure 8 defines the channel mask of a radio channel whose frequency is from 915.9 MHz

to 916.9 MHz. In this case the maximum permitted output power is 1 mW (0 dBm), so the

measurement is performed with this output power level. Figure 9 shows the SPIRIT1