BGY284 Просмотр технического описания (PDF) - Philips Electronics

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BGY284

power amplifier with integrated control loop for GSM850, EGSM900, DCS1800 & PCS1900

Philips Electronics 

Philips Semiconductors

power amplifier with integrated control loop for

GSM850, EGSM900, DCS1800 & PCS1900

Preliminary specification

BGY284

DESCRIPTION RAMP-UP

Minimum td1 before VTX on becomes high (control loop becomes active) the VSTAB must be available.

The Vband signal will select the correct transmit channel (LB = GSM850/EGSM900, or HB = DCS1800/PCS1900). The

Vband signal must be at the correct value no later than the rising edge of the VTXon signal.

The VTXon signal going high enables the power control loop. To set-up the right internal biasing conditions and charge

the integration capacitors to the right starting value there is a set-up time of VTXon before the first increase of VDAC.

Before VDAC signal is ramping high there has to be RF power on the input of the selected channel (PD LB,HB).

VDAC has to step up to the voltage level to get the required power level. Sequence of VDAC steps can be chosen to have

approximately a quarter cosine wave ramp-up of PL LB,HB in such a way that there is no violation of the GSM power mask,

and that in the same time there is no violation of the spectrum due to transients.

To avoid violation of the lowest power level in the GSM power mask (indicated by *), the BGY284 has to give sufficient

isolation in following condition: VTXon high, VDAC minimum value, RF power on input of PA.

For GSM850/EGSM900 the system specification for maximum output power level of the handset in this condition is

−36 dBm.

For DCS1800/PCS1900 the system specification in this condition is −48 dBm.

In the handset the antenna switch can still be in Rx mode and therefore still provide isolation between the PA and the

antenna. This situation is accounted in the isolation conditions in electrical characteristics transmit mode.

DESCRIPTION RAMP-DOWN

VDAC will step down from the voltage level for the current power level to offstate. Sequence of VDAC steps can be chosen

to have approximately a quarte cosine wave ramp-down of PL LB,HB in such a way that there is no violation of the GSM

power mask, and that in the same time there is no violation of the spectrum due to transients.

The control loop can be switched off (VTXon signal going to logic 0) as soon as the VDAC has reached the offstate level.

At the same time also the Vband signal is allowed to change polarity and the RF input power (PD LB,HB) at the selected

channel can be removed. Because there is no input power anymore there is no additional isolation specification required

to meet the GSM system specification.

For GSM850/EGSM900 the system specification for maximum output power level of the handset in this condition is

−54 dBm.

For DCS1800/PCS1900 the system specification in this condition is −48 dBm.

td6 after VTXon signal going to logic 0 (control loop is switched off) and all charge in the internal capacitors of the control

loop has been removed the BGY284 can go into idle mode (VSTAB can go to 0 V).

2003 Aug 20

7

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