Service Manual

CDMA sampling clock synthesizer
Local Oscillator for I-Q Mixer
I.Q offset Control Loop
Three-line Serial Bus Interface ( SBI ) for initializing and control of the IFR3000 from MSM5000
3.1.3.4 RX-IF SAW
RX-IF SAW is used to reject any undesirable out of band signal.
Rx Mode Operation
210.38 MHz of RX center frequency includes CDMA spread spectrum modulation signal that ±630KHz wide. Rx center frequency is
converted to the I&Q baseband signal through a mixer that is part of IFR3000. The receive signal is passed on to MSM5000 after low pass
filtering. . . This signal is digitized by 4 bit flash ADC.
3.1.4 TX Part
TX part consists of IFT3000, Up Converter, Power Amplifier Pre – Driver, Power Amplifier IC, and Duplexer and the role of each part is as
follows ;
3.1.4.1 IFT3000 ( Baseband-IF Converter )
IFT3000 consists of AGC amplifier and Baseband Analog Processor and TX IF PLL.
IFT3000 converts digital I and Q baseband components into analog I and Q components, and converts up to the IF frequency and puts out
an amplitude controlled
Tx IF signal. Base-band analog processor has PLL in it and has general purpose ADC circuit to read the battery
strength and temperature.
AGC is designed to control the gain according to the strength of signal that is generated from Tx IF synthesizer within 84dB of maximmum
dynamic
range. The gain of the AGC amplifier is +0.8dB when gain control voltage is 2.7V and is –82.3dB when gain control voltage is 0.3V but
actually uses 80dB
( 0.7V ~ 2.5V ) of gain range.
Single mode operation for CDMA transmit signal path includes ;
Conversion of digital I-Q Data to Analog Base Band Signals
Base Band to IF Up Conversion
Local Oscillator for I-Q Mixer
Mode Control Logic for Rx/Tx
General Purpose ADC for System Monitoring
Three-line Serial Bus Interface ( SBI ) for control of the IFT3000 via the MSM3000
Tx Operation Mode
8Bits I,Q Data that is from MSM3000 is input to I,Q D/A Converter. I data from rising edge of Tx clock is saved at I DAC and Q data from
fallingedge is saved at Q DAC. The frequency spectrum of CDMA DAC has noise that is generated at Tx clock is
filtered by the anti -aliasing LPF (630KHz ).. These analog, I,Q signals is synthesized
differentially with 130.38MHz IF that is generated at synthesizer of Tx center frequency and transferred to Tx AGC part.
3.1.4.2 TX Up converter and Power Amplifier Pre-Driver:
The final TX frequency of 1850-1910MHz is generated by the TX upconverter and driver amplifier chip using the IF of 130.38MHz and
1720-1780MHz LO generated by the PLL. The PA driver amplifies this signal so that PA sees a sufficient signal level at its input.
3.1.4.3 Power Amplifier
The power amplifier amplifies the TX power to required transmit levels with sufficient linearity to keep the spurious emissions within limits.
The voltage for the PA is supplied directly from the main supply. It can be turned off by taking the PA_ON input low.
3.2 Logic part
Logic part consists of power supply, digital part, PCMCIA interface part.
3.2.1 Power Supply
Power is supplied to the power management IC directly from the Laptop supply. The power management IC generates different voltages
as required by other sections of the card.
3.2.2 Digital Circuits
Digital part consists of MSM5000, Memory ( Flash, SRAM ) and EEPROM. MSM5000 is the ASIC chip designed for base-band digital signal
processing
and the standard clock that is needed for operation is ; CHIPx8 ( 9.8304MHz ) provided from RF part and 2 resonators ( 27MHz &
32.768KHz. The role of each clock is as follows;
- CHIPx8 : The clock that is developed in the IFR3000 by dividing the 19.68MHz TCXO frequency by a
512/1025 divider.