User Guide

NSD-5

3. System Module PAMS Technical Documentation

Page 44 Nokia Corporation Issue 1 05/02

bias. Since a voltage of greater than 3.8V was required for the bias, the 5-volt output

from CCONT has been utilized. The collectors of both stages of the PA are based from the

battery source. The reference current provided by the current source (formed by V601

and V602) controls gain of PA module by means of the Iref pin. The Tx-Gate signal is used

to switch a current mirror to switch the PA with approximately 4 mA current. If there is

no RF input to the PA, then it will draw approximately 100mA.

Table 13: Typical gain of the PA

1900MHz Transmitter Interstage Filtering

Due to the small separation between the U.S. PCS Tx Band (1930 - 1990MHz) and the Rx

band (1850 - 1910MHz), it is extremely difficult to filter the Tx noise from the Rx band

to a level acceptable to the receiver. The split band filter provides the Rx band rejection.

A single SAW filter cannot provide the rejection due to the wide PCS band and the small

separation between the Tx and Rx in PCS band. The split band filter output is connected

to a SPDT RF switch.

1900MHz Upconverter

The 1900MHz upconverter has been designed with discrete circuitry for PWB space rea-

sons and yield issues with the original MA/COM upconverter used in DCT3 (Apache).

A discrete solution has been designed with the IFA, mixer, RFA, and VVA in the same con-

figuration as in the Apache IC. The VVA used is AT119. The gain distribution between the

IFA and RFA has changed from DCT3. A discrete mixer CMY211 is used for upconversion

and it has a much better IIP

as compared to the mixer inside Apache IC. This allows IFA

gain to be increased and RFA gain to be decreased, which will dramatically improve the

Tx SNR (signal-to-noise ratio) at low powers. This results in far better low power Rho as

compared to DCT3.

The ACPR over the entire range of Tx power is also better than DCT3. Current consump-

tion of the entire upconverter is around 35mA. The discrete upconverter consists of V604

(IFA), N605 (mixer), and V605 (RFA).

Driver

The PCS driver used is a single-input, double-output amplifier. The outputs can be

selected through a digital control (CH). All inputs and outputs are single-ended, 50 ohm,

and matched. This amplifier is used in the Tx chain to increase the power of CDMA sig-

nals to the PA module. It consumes a low amount of current.

Transmitter Intermediate Frequency (TIF)

The TIF IC generates the intermediate frequency (IF) for the 1900MHz transmitter. This IC

reference designator (N604) incorporates the IQ modulator for CDMA mode, 85dB of

dynamic range control, and a switch for the two transmitters. Also included in the TIF IC

is most of the circuitry required for the power detection for CDMA over power detection

1900MHz PA

Gain 25dB