Abstract
This application note presents measured performance data for the MAX2265 power amplifier (PA) when used for EDGE 8PSK modulation. +18.5dBm power was obtained in the 925MHz to 960MHz band. With a 5V power supply, 340mA were used to provide EVM better than 1%.
Additional Information:
Introduction
Many GSM operators are beginning to install 2G networks to support higher data rates, addressing the expected demands of mobile-phone users. EDGE, which stands for "Enhanced Data Rates for GSM Evolution," essentially triples the existing GSM data rate from 1-bit/symbol GMSK (gaussian minimum shift key) modulation to 3 bits/symbol 8PSK (phase shift key) while operating in the same occupied channel bandwidth.
The newly adopted modulation scheme of 8PSK requires a highly linear amplifier to minimize spectral regrowth and phase distortion. Power amplifiers for base station applications impose even more stringent requirements for its pre-driver to present a pristine signal with minimum non-linearity. As usual, the pre-driver must be electrically and thermally stable with good reliability for this application.
The MAX2265 is an excellent low-cost bipolar solution for GSM/EDGE base station down link pre-driver applications. Performance specifications are presented in this application note. Measured data indicates that the MAX2265 meets or exceeds requirements with margin.
| Parameter | Customer Spec | Measured Data | Units | Reference/Notes |
| Supply Voltage | 5.0 | 5.0 | V | - |
| Supply Current | - | 340 | mA | POUT = +18.5dBm |
| Frequency Range | 925 - 960 | 925 - 960 | MHz | - |
| POUT | +17.5 | +18.5 | dBm | EDGE Mode |
| Gain | 20 | 24.5 | dB | - |
| Spurious at 400kHz offset | -70 | -71 | dBc | Measured in 30kHz BW |
| Spurious at 600kHz offset | -80 | -83 | dBc | Measured in 30kHz BW |
| EVM (average) | 1 | 0.98 | % | - |
Figure 1. EDGE modulation spectrum plot at 960MHz and +18.5dBm POUT.
Figure 2. EDGE EVM at 960MHz and +18.5dBm output power.
Figure 3. EDGE mode transmit output power plot.
Figure 4. S21 and S12 small signal plots.
Figure 5. S11 and S22 small signal plots.
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