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參數(shù)資料
| 型號(hào)： | ACE9030 |
| 廠商： | Mitel Networks Corporation |
| 英文描述： | Radio Interface and Twin Synthesiser |
| 中文描述： | 無線接口和雙合成器 |
| 文件頁數(shù)： | 35/39頁 |
| 文件大?。?/td> | 379K |
| 代理商： | ACE9030 |
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ACE9030
35
division will be 495 for a 14·85 MHz crystal; the term f
is
used to refer to the exact crystal frequency in the following
calculations.
Thus Main synthesiser (nominally 915·030 MHz) gener-
ates:
f
CRYSTAL
x 30501
÷
495 = f
CRYSTAL
x 61·61818182
This result is independant of the chosen comparison fre-
quency which is given above as an illustration only.
With this drive to the first mixer the actual first I.F.
(nominally 45 MHz) is:
f
CRYSTAL
x 61·61818182 – 870·030 MHz
The second mixer is required to downconvert 45 MHz to
450 kHz so needs an LO2 at 44·550 MHz which is 3
∞
f
and this integer multiplication is the reason for choosing a
14·85 MHz crystal. This mixer operates with low-side injection
so the actual second I.F. on the AFCIN pin (nominally
450 kHz) is:
f
CRYSTAL
x 61·61818182 – 870·030 MHz – 3
∞
f
CRYSTAL
= f
CRYSTAL
x 58·61818182 – 870·030 MHz
This signal feeds the F.M. discriminator to extract the
modulation and is also used to derive the AFC information.
The AFC mixer uses a 504 kHz clock derived from the
crystal (f
∞
504
÷
14850 = f
∞
0·03393939) to high-
side downconvert AFCIN to a low frequency on AFCOUT,
giving:
(f
CRYSTAL
x 0·03393939) –
(f
CRYSTAL
x 58·61818182 – 870·030 MHz).
This is 870·030 MHz – f
x 58·58424243 and is the
difference between two large but similar numbers, one fixed
and the other a multiple of f
CRYSTAL
and will have an overall value
strongly dependent on f
To evaluate the sensitivity of the system consider a
+ 1 ppm change in crystal frequency, giving AFCOUT at
53·130 kHz instead of its nominal at 54 kHz, a shift of 870 Hz
or 1·61 %. This frequency can be counted in the
microcontroller using a timebase derived from f
or any
other crystal reference as the error in the timebase due to the
crystal is swamped by the changes in AFCOUT.
The counting of AFCOUT should be over a period long
enough to resolve changes of around 1 % which means at
least 2 ms but is normally a little longer to filter off some noise
and modulation on the signal; around 10 ms is a good starting
value for system development.
Once the crystal error has been estimated the DAC’s
controlling the crystal frequency can be adjusted to bring the
whole cellular terminal into frequency alignment with the
basestation which is normally assumed to be very accurately
held at the correct frequency; effects like Doppler shift will be
significantly less than 1 ppm for all intended users. Some
damping in the control loop for the crystal will be needed to
avoid overshoot and hunting, possibly implemented as always
under-correcting the crystal or by limiting the slew rate of the
corrections.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ACE9040 | Audio Processor Advance Information |
| ACE9050 | System Controller and Data Modem(為蜂窩式手機(jī)提供控制和邏輯接口功能的系統(tǒng)控制器和數(shù)據(jù)調(diào)制解調(diào)器) |
| ACE9050 | System Controller and Data Modem Advance Information |
| ACFA-450 | AM CERAMIC FILTERS |
| ACFA-455 | AM CERAMIC FILTERS |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ACE9030IGFP1N | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Parallel-Input Frequency Synthesizer |
| ACE9030IGFP1R | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Parallel-Input Frequency Synthesizer |
| ACE9030IGFP2N | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Parallel-Input Frequency Synthesizer |
| ACE9030IGFP2R | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Parallel-Input Frequency Synthesizer |
| ACE9030M | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:Radio Interface and Twin Synthesiser |
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