AN1602 Freescale Semiconductor / Motorola, AN1602 Datasheet - Page 9

• Manufacturer Part Number: AN1602
• Description: AN1602 Application Note: Dual-Band PA Application w/DECT Capability Using Std RFICs
• Manufacturer: Freescale Semiconductor / Motorola

DECT
that case the quiescent current of the DCS PA needs to be
decreased in order to get an acceptable efficiency at about
27 dBm output power. This can be realized by increasing the
R14 resistor value to 5.6 k in order to get about –2.7 V at the
VCDCS point. The user will also have to change the input
matching network in order to match the DECT bandwidth. An
example of such an input matching is given Figure 14 . In this
configuration, the gain on the DCS path is reduced by 2.0 dB
because of higher losses at the input.
Open Loop
control has been experienced to suppress the control loop.
This technique has been called “open–loop” control, and a
separate application note, AN1599, describing this technique
is available.
the implementation of the open–loop concept. The user can
MOTOROLA SEMICONDUCTOR APPLICATION INFORMATION
The DCS path can also be evaluated in the DECT band. In
Figure 14. Input Matching for DCS and DECT Band
The highly linear transfer function achieved with the drain
The dual band demonstration board is designed to allow
Figure 13. Output RF Voltage Variation with
Linear Control Ramp at 3.6 V
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experiment this technique by simply adding a 3 pole
Sallen–key filter in the control circuit, in order to smooth the
transitions (see Figure 12).
4.7 k
and the dual band board can be experimented in open loop
mode.
SYSTEM SOLUTION
shows a possible architecture in which the output switch can
be the MRFIC0903. In that configuration the ENSWT pin can
be used to control the switch.
Since the switch/filter block shown does not exist as a
standard product, this demonstration board can help the user
define a dedicated switch specification in order to drive the
product definition.
different matching). MRFIC1817/MRFIC1818 is also usable
for PCS band. The application circuit shown here can also be
used for other dual mode amplifiers such as AMPS/PCS with
small changes in the component implementation.
Figure 15. Dual Band PA Architecture with Duplexers
R8 resistor is changed to 1.0 k , R9, R10 need to be set at
The antenna interface may require duplexers. Figure 15
Figure 16 shows a possible architecture without duplexer.
MRFIC0913 is also suitable for AMPS standard (with a
C27 (560 pF), C28 (1.5 nF), C29 (1.0 nF) are added
Figure 16. Dual Band PA Architecture
without Duplexer
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