PSB4596 Siemens Semiconductor Group, PSB4596 Datasheet - Page 22

• Manufacturer Part Number: PSB4596
• Description: Analog Line Interface Solution ALIS
• Manufacturer: Siemens Semiconductor Group

4.2.1
After passing the DAA and a simple anti-aliasing pre-filter with an analog gain stage, the
voice signal is converted to a 1-bit digital data stream in the sigma-delta converter. The
first down-sampling steps are performed in fast digital hardware filters. Subsequent
processing is implemented in the digital structure which allows easy and flexible
programming of parameters. Finally, the fully processed signal is transferred to the data
interface.
Subsequent processing is done by microcode in the digital filter structure to allow
adaptability. Gain adjustment is provided in two stages, AR1 and AR2. The total gain
adjustment is programmable in two ranges: from 14 to 24 dB, in steps of 0.5 dB; and from
-3 to 14 dB, with steps between 0.02 and 0.05 dB.
Located inbetween is a decimation stage to reduce the sampling rate to the 8 kHz PCM
rate, and a low-pass filter to band-limit the signal in accordance with ITU-T G.714 and
ETSI (NET33) recommendations (in RFIX1); also an equalization stage (in FRR).
Finally, the signal is passed out to the Serial Data Interface (SDI).
ALIS meets or exceeds all ITU and ETSI (NET33) recommendations on attenuation
distortion and group delay.
4.2.2
The digital input signal is received via the data interface. Low-pass filtering, gain
correction and frequency-response correction are implemented in the digital filter
structure. The up-sampling interpolation is then performed by fast hardware structures
to reduce the DSP load. The up-sampled 1-bit data stream is converted to an analog
equivalent which is smoothed by a post-filter (POFI) and converted to a 2-wire signal in
the DAA.
There are also two independent tone generators which can insert tones into the Transmit
path. They have adjustable frequencies, default 2 kHz, and a programmable bandpass-
filter to adapt the output for DTMF. When either tone generator is on, the data signal
transmission is suppressed.
4.2.3
ALIS implementation includes two loops. One is used to generate the AC-termination
impedance (IM) and the other is used to perform proper hybrid balancing (TH). A simple
additional path IM (from the receive to the transmit path) supports the impedance-
matching function.
4.2.4
Several analog and digital test loops are implemented in ALIS. The receive and transmit
paths may be short-circuited at two different points for test purposes.
Semiconductor Group
Receive Path
Transmit Path
Loops
Test Features
22
Analog Line Interface Solution
PSB 4595 / PSB 4596
ALIS Implementation
Data Sheet 06.98