PCF5079 datasheet(17/28 Pages) PHILIPS

17 / 28 page

2001 Nov 21

Philips Semiconductors

Product speciﬁcation

Dual-band power ampliﬁer controller for

GSM, PCN and DCS

PCF5079

12.2

PA protection against mismatch

High VSWR at the PA output may occur in systems where

the PA is connected to the antenna via couplers and

switches with low insertion loss, depending on the antenna

matching. The incident and reflected power have to be

monitored and care has to be taken to prevent the

summed RF power does not exceed the defined maximum

value at the PA output.

As two sensor inputs are available in the PCF5079, two

different detector signals can be combined: one for direct

path and one for reflected path. These two voltages, fed to

the sensor inputs, are summed inside the PCF5079

resulting in a decrease in the PA output power if there is an

increase of the VSWR at the antenna port (see Fig.15).

handbook, full pagewidth

MGT330

band select

switch

VS1

VS2

RFin HB

RFout

RFin LB

broad band

coupler

Fig.15 Example of PA mismatch protection circuit.

Table 3

Table of components (see Fig.15)

SYMBOL

COMPONENT

DESCRIPTION

D1, D2

detector diode

Philips 1PS79SB62

R1, R2

resistor

R = 1 k

Ω (decoupling versions)

C1, C2

capacitor

C = 39 pF

−

band select switch

Motorola; Alpha Industries; M/A; COM GaAs MMIC; or discrete pin diode,

e.g. Philips BAP51-03

−

broad band coupler

Murata LCD20 series; TDK HHM 20, 22 series

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