Interface Description EMII-1900 Service Manual Application Information
EMII-1900 V1.0 AnyDATA.NET Proprietary
Use Subject to Restrictions
1. Overview
RFT3100 receives modulated digital signals from the MSM of the digital circuit and then, changes them into analog signals by
the digital/analog converter (DAC, D/A Converter) in order to create baseband signals. Created baseband signals are changed
into IF signals by RFT3100 and then, fed into the Mixer after going through AGC. IF signals that have been fed are mixed with
the signals of VCO and changed into the RF signals and then, they are amplified at the Power AMP. Finally, they are sent out
to the cell site via the antenna after going through the isolator and duplexer.
2. RF Transmit / Receive Part
2.1 CDMA Transmit End
8 bit I and Q transmit signals are inputted into 2 DACs (DIGITAL-TO-ANALOG CONVERTER) from
the output terminal I_DATA, I_DATA\, Q_DATA, Q_DATA\ of MSM through the input terminals
I_DATA, I_DATA\, Q_DATA, Q_DATA\ of RFT3100. Transmit signal input speed is two times of
TXCLK+, TXCLK- which are two transmit/receive reference frequency.
Among transmit signals being inputted, signals are inputted into I signal DAC when the transmit clock is
in the rise edge, whereas signals are inputted into Q Signal DAC during the drop edge. I and Q transmit
signals are compensated and outputted at MSM in order to compensate the 1/2 clock time difference
generated between reference clocks. In the signals coming out from the output terminal of DAC, there are
spurious frequency ingredients resulting from DAC output transition edge and parasite ingredients,
transmit clock frequencies and harmonics which are unwanted signals. Accordingly, spurious ingredients
are removed by passing the signals through LPF of passband 6.30KHz. Unlike the receive end, the
transmit end LPF requires no OFFSET adjustment. Analog baseband signals that have passed the CDMA
LPF are mixed with I and Q signals of frequency 130.38 MHz (260.76 MHz created in the RFT3100
internal VCO are divided by half into frequency 130.38MHz having the phase difference of 90 degrees) in
two mixers. The mixed signals are added again and converted into IF frequency 130.38 MHz
⥮
630 KHz
(CDMA Spread Power Density Modulated Signals) and then, outputted.
2.2. Tx IF/Baseband Processors, RFT3100 (U102)
The RFT3100 includes digital-to-analog converters(DAC) for converting digital baseband to analog
baseband, low-pass filters, a mixer for up-converting to IF and an 85 dB dynamic range Tx AGC
amplifier. The RFT3100 has an IF mixer for upconverting analog baseband to IF, a programmable PLL
for generating Tx IF frequency, single sideband upconversion from IF to RF, two cellular and two PCS
driver amplifiers. The RFT3100 will operate over the follow Tx frequency ranges :
Cellular band 824MHz ~ 925MHz
PCS band 1750MHz ~1910MHz
CHAPTER 3. Circuit Description
