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Maxim > Design Support > Technical Documents > Application Notes > Wireless and RF > APP 584
Keywords: rf, pa, bluetooth, 2.4ghz wireless, rfic, wlan, fhss, lna, rf ics
APPLICATION NOTE 584
+23dBm PA and PA Predriver with 37% Efficiency
for 2.4GHz FHSS WLAN Applications
Nov 20, 2001
Abstract: Presents design trade-offs and measured performance of MAX2644 and MAX2242 for PA and
PA driver in FHSS radios for WLAN applications. Bias and RF layout and matching are modified to
improve performance at 2450MHz. +23dBm output power was achieved with -12dBm input power.
Supply current is 185mA with 3V applied.
Additional Information
Wireless Product Line Page
Quick View Data Sheet for the MAX2242
Quick View Data Sheet for the MAX2644
Applications Technical Support
There are many commercially available transceivers optimized for
2.4GHz FHSS (frequency-hopping spread spectrum) applications,
such as Bluetooth, HomeRF, and DECT (digital European cordless
telephone). The majority of these ICs have limited transmit power
and therefore are restricted to transmitting over very short
distances. Many PC-card manufacturers seeking to differentiate their product from the competition are
adding external PAs (power amplifiers) to extend the transmit range of their product. Bluetooth and
HomeRF allow a maximum output power of +20dBm (100mW) at the antenna, whereas 2.4GHz DECT
can transmit up to +24dBm (250mW). PAs for these applications are generally required to deliver
between +23dBm and +27dBm to overcome an expected 3dB of loss in the RF switch and duplexer,
which separate the PA and the antenna (see Figure 1). To prolong battery life, Bluetooth and DECT
utilize GFSK (Gaussian frequency-shift keying) modulation and HomeRF uses two- and four-level FSK,
which allows the use of saturated PAs, which are more power-efficient than linear power amplifiers.
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