DS_1x66B_001
73M1866B/73M1966B Data Sheet
8.6 Transmit Path Signal Processing
8.6.1 General Description
In the transmit path, data is first sent by the host DSP through a serial interface to the 73M1x66B then
interpolated by an interpolation filter, serialized and transmitted across barrier interface to the Line-Side
Device, which is floating relative to the Host-Side Device earth ground. The data received on the
Line-Side Device is then de-serialized and digitally sigma-delta modulated to a one-bit data stream of
1.536 Mbps for a sample frequency of 8 kHz or 3.072 Mbps for a sample frequency of 16 kHz. The signal
is further filtered first by a switched capacitor filter and then a continuous time anti-aliasing circuit.
•
•
The 0.2 dB pass-band ripple frequency is from dc to 3.422 kHz for an 8 kHz sample rate or 6.844 kHz
for a 16 kHz sample rate.
The 3 dB bandwidth is 3.65 kHz for an 8 kHz sample rate or 7.299 kHz for a 16 kHz sample rate.
8.6.2 Total Transmit Path Response
Figure 26 and Figure 27 show the transmit path frequency response. The response shape is the same,
but the frequencies double for a 16 kHz sample rate.
Transmit Path Overall Frequency Response
10
10
0
10
20
30
40
50
60
70
80
90
100
com
composite(x)
iplo
xo u
xo u
− 100
0
0
1
2
3
4
5
6
7
8
x⋅16
8
Freq(kHz)
Figure 26: Transmit Path Overall Frequency Response to Fs of 8 kHz
Transmit Passband Response
1.
1
0.8
0.6
0.4
0.2
0
composite(x)
0.2
0.4
0.6
0.8
1
− 1.0
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4
x⋅16
Freq(kHz)
Figure 27: Transmit Path Passband Response for an 8 kHz Sample Rate
Rev. 1.6
49
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
