User's Manual

15 014-0030-00 Rev. G
6 Transmitter Information
6.1 Transmit Spectral Shape
The spectrum shape of the AP can be described as similar to the Global System for Mobile
Communications (GSM) which uses Gaussian Minimum Shift Keying (GMSK) but with a 1 MHz
signal passband instead of the 200 kHz for GSM. Spectral side lobes are present even when the
transmitter is in the linear range. As the Power Amplifier (PA) goes into compression (starting
around 25 dBm) the main lobe compresses inward while the side lobes increase in amplitude.
P
out
 0 dBm P
out
 30 dBm
Figure 6. Spectral Shape—Linear and Compressed
6.2 Load VSWR Effects on TX Power Accuracy
The gain of the high power PA (P
out
≥ 16 dBm) is susceptible to load Voltage Standing Wave
Ratio (VSWR). A summary of VSWR effects on TX power accuracy is listed in the following
table. This establishes minimum return loss (VSWR) requirements of ≤ -15 dB. Note that in
normal operation, the closed loop power control will attempt to compensate for some gain
variation.
Table 12. Summary of TX Gain/Power Variation Due to Load VSWR
Return Loss
Gain/Power Variation
Comments
7 dB
± 1.5 dB
Not to specification
15 dB
± 0.7 dB
To specification
20 dB
± 0.35 dB
To specification