Ericsson Base Station F800 - Outgoing Speech; Modulation Circuits

F800 CIRCUIT DESCRIPTION 21 (25)
Uppgjord (även faktaansvarig om annan) -
Prepared (also subject responsible if other)
Nr -
No.
KL/ECS/S/LT Magnus Lindahl ECS/S/LT-96:5044
Dokansv/Godk -
Doc respons/Approved
Kontr -
Checked
Datum -
Date
Rev File
KI/ECS/S/LTC 1996-06-06 A
965044.DOC
Incoming AF from the radio section on J404:5 is filtered in an HP- filter formed by
Z21A, Z21B and peripheral components. After the filters the signal is connected to a
AF switch, Z26A which is followed by an amplifier stage, Z21C. The amplifier has
approx. 5 times amplification and the output signal is -10dBu. The amplified signal is
connected through a de-emphasis network, R56 and C60 to P405:14.
RX data signals are withdrawn before the LP filter and made available on P405:4,
level approx. -10dBu. RX data signals are used for reception of tones in some line
interfaces.
Outgoing speech
Outgoing speech denotes the internal handling on the CPU board of audio signals
generated by the line interface.
TX Line
Mic
Z22A
Z21D
TX Data
Z22B
Limiter
Z22C Z22D
From outport
Z26B
To mod. circuits
Fig N: Block diagram TX AF
An audio signal from the line interface is connected to an amplifier stage, Z22A via
P405:8. The amplifier is followed by a pre-emphasis net , C8, R67. The pre-emphasis
net is followed by a limiter, Z22B. The Z22B limits the amplitude to 3,5V
PP
. The limiter
is followed by an LP filter, R77-R80 and C12. The filtered signal is then connected to
an active LP filter formed by Z22C and Z22D with associated components.
The signal is then passed on to the modulation circuits.
TX data is introduced in the audio path after the limiter, Z22B. TX data is used by
some line interfaces for transmission of tones. The TX data signals are connected to
P405:3 and then passed on to a limiter formed by Z21D.
AF signals from the service handset, P401:4 are connected to the first amplifier, Z22A.
Modulation circuits
In the modulation circuits the incoming signal comes from the line ,TX line, or from the
line interface, TX data,. After the speech circuits the modulation signal is connected
through an audio switch to the modulation sensitivity block.