The MAX2265 Is Ideal for EDGE Base-Station Pre-Driver Applications

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要約

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.

Table 1. EDGE Pre-Driver Specification and MAX2265 Measured Data

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 P<sub>OUT</sub>.
Figure 1. EDGE modulation spectrum plot at 960MHz and +18.5dBm POUT.

Figure 2. EDGE EVM at 960MHz and +18.5dBm output power.
Figure 2. EDGE EVM at 960MHz and +18.5dBm output power.

Figure 3. EDGE mode transmit output power plot.
Figure 3. EDGE mode transmit output power plot.

Figure 4. S21 and S12 small signal plots.
Figure 4. S21 and S12 small signal plots.

Figure 5. S11 and S22 small signal plots.
Figure 5. S11 and S22 small signal plots.