User Guide

PAMS
Technical Documentation
NSB–1
System Module
Page 3 – 29
Original 06/98
Functional Description
The following description of the RF is valid for both DCS1800 and
DCS1900, the only difference between the two systems is:
1. antenna
2. duplexer (Z401)
3. RX and TX interstage filters (Z604 and Z503/Z505)
4. UHF VCO modules (G701)
5. matching networks (discrete components)
6. PA (N500)
Even though different components are used in the two engines, the foot-
prints of the different components are the same. As can been seen from
the RF block diagram, most of the functions have been integrated into
three ASICs.
CRFU2a (N402) is a wideband UHF ASIC with both receiver and trans-
mitter functions. The receiver functions include LNA bias and two down-
conversion mixers (Gilbert cell) with LO buffers. The LNA transistor is ex-
ternal to CRFU2a. The transmitter functions include an upconversion
mixer (image rejection) with LO buffer. All inputs/outputs are wideband
and require external matching networks for optimal performance.
PLUSSA (N401) provides two main functions:
1. RX/TX blocks
2. PLL
The receiver includes a Receive Controlled Gain Amplifier, a mixer with
LO buffers and IF amplifiers. The transmitter section includes a Transmit
Controlled Gain Amplifier, an I/Q Modulator, circuitry required to generate
the Quadrature Local Oscillator and Transmit Power Control which con-
trols the MMIC PA (N500) output power. The PLL section is control via a
serial bus and contains both UHF and VHF PLL and predividers.
The MMIC PA (N500) uses Ga–As– heterojunction bipolar transistor (GaAs
HBT) technology. The PA has an overall dynamic range of 45dB, and is ca-
pable of producing 32.5dBm output power with +3dBm input.
Interfacing with the above ASICs is four more ASICs. These include:
1. CCONT (N100)– is a multifunction power management IC. This
ASIC contains six 2.8V linear regulators used in the RF section as well as
two 2.8V regulators used in the BB section. CCONT also contains a
switch mode supply power which generates +5V which is used to power
the charge pumps in PLUSSA. Some of the features of this IC are a nine
channel A/D converter, power up/down procedures, reset logic, charging
control, watchdog, sleep control and SIM interface.
2. COBBA_GJ (N300)– is an interface between the digital
world of the BB processing and the analog world of RF and audio circuit-
ry.
3. MAD2 (D200) – contains system logic and DSP
4. CHAPS (N110) – charging control ASIC