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參數(shù)資料
| 型號(hào)： | ACE9040 |
| 廠商： | Mitel Networks Corporation |
| 英文描述： | Audio Processor Advance Information |
| 中文描述： | 音頻處理器進(jìn)展信息 |
| 文件頁數(shù)： | 22/33頁 |
| 文件大小： | 335K |
| 代理商： | ACE9040 |
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22
ACE9040
FINAL MODULATION PREPARATION
Pre-emphasis
A pre-emphasis filter follows the compressor to boost
the amplitude of higher audio frequencies by tilting the fre-
quency response by 6 dB per octave across the whole speech
band as shown in figures 5 and 8. To prevent overload in the
pre-emphasis filter the signal first passes through an
attenuator set to suit the system in use. If an external
compander is used or the companding function is bypassed
the gain is set to 0 dB. When using the internal compander the
gain is set to – 7 dB for TACS or – 11·0 dB for AMPS.
Compander bypass is determined by control bits COMP[2:1].
The pre-emphasis filter and attenuator input is pin PREIN and
the output is an internal connection to the hard limiter. The pre-
emphasis filter, but not the attenuator, can be bypassed if the
PREEMPH bit in the “Operation mode” control message is set
to “1”.
Hard Limiter
To ensure compliance with the peak deviation specifi-
cation for cellular telephone systems, a hard limiter follows the
pre-emphasis filter to remove any transient level changes that
have passed through the soft limiter. This limiter will handle
large signals and has symmetrical clipping levels close to the
supply rails V
& V
(GND). To ensure clipping at the same
hard limiter input signal level with both the nominal power
supply voltages, hard limiter gain is adjusted by an external pin
“V485”. For the nominal supply voltages of 4.85 V and 3.75 V
gain is respectively 16 dB (V485 pin at “1”) and 13.5 dB (V485
pin at “0”). An 8 dB attenuator follows the limiter to prevent any
further clipping of the signal in the following transmit lowpass
filter.
TX Lowpass Filter TXLPF
A TXLPF lowpass filter with an optimised stop band
response limits the signal bandwidth to a cut-off frequency of
3·0 kHz, the frequency response is shown in figure 6. The
combined frequency response of the pre-emphasis and
lowpass filter stages is shown in figure 8. It is possible for test
purposes to bypass this lowpass filter by setting bit TEST[0] in
the “Initializing mode 1” control message to a “1”.
Speech Deviation Level Setting
A controlled gain stage AUDIODEV sets the output level
to give the required FM deviation for speech. The gain is set
by bits AUDEV[3:0] in the “Initializing mode 1” control mes-
sage. AUDIODEV is followed by a transmit audio mute switch
enabled by bit TXM in the “Operation mode” control message.
A buffer drives output pin TLPO with the transmit speech
signal (and DTMF when in use) which is added with DATA/ST
and SAT tones in the modulation combiner.
Fig. 12 Transmit Data and DTMF Paths
TRANSMIT DATA AND DTMF PATHS
Transmit Data
Data communication from mobile terminals to base
stations in the AMPS and TACS cellular phone systems takes
place over the Reverse Control Channel (RECC) during call
set-up and in short bursts over the Reverse Voice Channel
(RVC) during a call.
RECC or RVC data is transmitted for AMPS or TACS as
a 10 kHz or 8 kHz Manchester Coded FSK signal
respectively. The data signal is generated by the ACE9050
“System Controller and Data Modem” or similar digital circuit
to drive ACE9040’s DATI input pin. The DATI input data signal
is filtered using a 4th order Butterworth lowpass filter with
nominal - 3 dB points of 16 kHz for TACS, or 20 kHz for
AMPS. This filter is implemented using switched capacitor
techniques and is preceded by a continuous time anti-alias
DATI
DTMF[3:0]
DTWIST DTMFMODE[2:1]
DTMFM
IPS
TONEM
RXI
RECEIVE
VOICE PATH
TRANSMIT
VOICE PATH
DATO
DTMF
VMID
DATM
16/20kHz
DATAF[1:0]
-2.8 to + 3.2dB
DATD[3:0]
DATADEV
LOW-PASS
FILTER
DTMF
PRE-
EMPHASIS
MODE
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| 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 |
| ACFA-459 | AM CERAMIC FILTERS |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ACE9040IGFP1N | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:RF/Baseband Circuit |
| ACE9040IGFP1R | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:RF/Baseband Circuit |
| ACE9040IGFP2N | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:RF/Baseband Circuit |
| ACE9040IGFP2R | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:RF/Baseband Circuit |
| ACE9040J/IW/FP1Q | 制造商:Rochester Electronics LLC 功能描述: 制造商:Zarlink Semiconductor Inc 功能描述: 制造商:ZARLINK 功能描述: |
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