Interface Description EMII-800 Service Manual Application Information
EMII-800 V1.0 AnyDATA.NET Proprietary
Use Subject to Restrictions
antenna in order to prevent any damages on circuits, that may be generated by output signals reflected from the
duplexer and re-inputted to the power amplifier output end.
2.6. Description of Frequency Synthesizer Circuit
2.6.1 Voltage Control Temperature Compensation Crystal Oscillator(TCX201, VCTCXO)
The temperature range that can be compensated by TCX201 which is the reference frequency generator of mobile
terminal is -30 ~ +80 degrees. TCX201 receives frequency tuning signals called TRK_LO_ADJ from MSM as
0.5V~2.5V DC via R and C filters in order to generate the reference frequency of 19.68MHz and input it into the
frequency synthesizer of UHF band. Frequency stability depending on temperature is
2.0 ppm.
2.6.2 UHF Band Frequency Synthesizer (U202)
Reference frequency that can be inputted to U 202 is 3MHz~40MHz. It is the dual mode
frequency synthesizer (PLL) that can synthesize the frequencies of UHF band 50MHz~1200MHz and IF band
20MHz~300MHz. U202 that receives the reference frequency of 19.68MHz from U174 creates 30kHz comparison frequency
with the use of internal program and then, changes the frequency of 900MHz band inputted from X200 which is the voltage
adjustment crystal oscillator into the comparison frequency of 30kHz at the prescaler in U202. Then, two signal differences are
calculated from the internal phase comparator. The calculated difference is inputted to DC for adjusting the frequency of U202
through U202 No.2 PIN and external loop filter in order to generate UHF signals. In addition, outputs of other PIN17 are
inputted into BBA after going through the VRACTOR diode and tank circuit so that the outputs of BBA internal receive end
VCO are adjusted to 170.76MHz.
2.6.3 Voltage Control Crystal Oscillator (U204)
U171 that generates the LO frequency (900MHz) of mobile terminal receives the output voltage of PLL U 202 and
then, generates the frequency of 954MHz at 0.7V and the frequency of 980MHz at 2.7V. The sensitivity on control
voltage is 23MHz/v and the output level is 1dBm(maximum). Since LO frequency signal is very important for the
sensitivity of mobile terminal, they must have good spurious characteristics. U174 is -70dBc(maximum).
