Lpf Circuit - Furuno FS-1575 Service Manual

Signal Name
15V Power supply voltage for the TX FIL board.
CLK, DATA,
TX FIL board control signals, which are serial signals with the T-CPU.
ST
Inputs RF signal transmitted from the PA board with the FS-1575 or
TX IN FS-2575 system, and that transmitted from the COMB board with the
FS-5075 system.
Control signals, which connects TX FIL output power to the 50-ohm
CHECK ON
dummy load circuit when conducting a self-test on the transmission block.
V-SWR Vr detection signal inputted in the TX FIL board.
IN VR
Detected value is displayed on the SELF CHECK window.
ALC signal, which maintains TX output power at the specified power level.
This signal controls output power from the TX board.
ALC
Input signals for the ALC detection circuit are V-SWR VR and VF for
input/output in/from the TX FIL circuit.
TX_RX ANT T/R antenna terminal, which is connected to the antenna coupler.
RX ANT RX antenna terminal, which is connected to the RX board.
BK ON Controls the 50-ohm break-in (BK) relay.
TX FIL HW TX FIL board hardware information. This information is displayed by
VER selecting [MENU] -> 9.SERVICE -> 5.TEST -> 1.VERSION.

1. LPF circuit

The LPF circuit consists of eight Low-pass filters with a different frequency band
between 1605 kHz and 27.5 MHz and reduces spurious emission caused by the DRV
and PA boards.
The Low-pass filters provide insertion loss of not more than 0.5dB and stop-band
attenuation of not less than 40dB with frequencies more than double the cutoff
frequency of each Low-pass filter.
8M: PA OUT
CONFIDENTIAL (internal use only)
This confidential document is used only by FURUNO authorized persons.
It is strictly prohibited to reproduce the document in whole or in part without prior written permission of FURUNO.
Table 7.2.9 Major Signals of TX FIL Board
Function
8M: TX FILOUT
7-30
7.2 Transmission Circuit