IRT Electronics RWT-3810, RWR-3810 User Manual

3810-rwt.ib.rev1.doc Page 1 of 11 17/10/2007

IRT Eurocard

Types RWT-3810 / RWR-3810

L Band RF Fibre Optic Link

DANGER

A

void direct exposure to beam

Peak power 1 mW
Wavelength 1300 nm

Invisible LASER radiation-

Class 1 LASER Product

Designed and manufactured in Australia

IRT can be found on the Internet at:

http://www.irtelectronics.com

I R T Electronics Pty Ltd A.B.N. 35 000 832 575

26 Hotham Parade, ARTARMON N.S.W. 2064 AUSTRALIA
National: Phone: [phone] Fax: [phone]
International: [phone] [phone]
Email: [e-mail]
Web: www.irtelectronics.com

IRT Communications

www.irtcommunications.com

3810-rwt.ib.rev1.doc Page 2 of 11 17/10/2007

RWT-3810 / RWR-3810

L BAND RF FIBRE OPTIC LINK

Instruction Manual

Table of Contents

Section Page

General description 3
Technical specifications 5
Pre-installation 6

Operational safety 6

Installation 7

Installation in frame 7

Front and rear layouts 9
Maintenance & storage 10
Warranty & service 10

Equipment return 10
Drawing index 11

IRT Communications

www.irtcommunications.com

3810-rwt.ib.rev1.doc Page 3 of 11 17/10/2007

IRT Eurocard

RWT-3810 / RWR-3810

L BAND RF FIBRE OPTIC LINK

General description

The IRT RWT-3810 / RWR-3810 wide band RF fibre optic link is a modular system for transmitting a broadband
RF signal ranging from 900 MHz to 2050 MHz along an optical fibre. A system consists of two IRT Eurocard
modules, the RWT-3810 LASER transmitter module and the RWR-3810 photo-diode receiver module.

RWT-3810 Laser Transmitter.

The RWT-3810 LASER transmitter module consists of a wide bandwidth LASER diode, whose operating current is
set by a driver circuit controlled by feedback from the monitoring diode in the laser package. A wide band RF
amplifier is used to drive the LASER with the RF signal applied to the module input.

A RF gain control and RF monitor connector are provided on the front panel. The gain of the RF amplifier is
adjusted by the front panel control (RV1), which varies the bias on the attenuator circuit in the RF gain stage.
The gain is adjusted for best signal to noise and inter-modulation performance by setting the RF level at the front
panel RF monitor connector at –40dBm.

The laser internal monitoring diode output is connected to comparator circuits, which are used to provide optical
power indications. The circuits drive LD3 on the front panel for laser power ON and FAIL indication (green for
normal and red for failure), and after passing through a relay circuit, a LASER POWER ALARM is available as an
external connection. The adjustment and connection data for this circuit is given in the installation section of the
manual.

A 10.7 MHz pilot tone generator circuit is provided which with a detector circuit in the RWR-3810 receiver will
verify the RF signal path of the system. The pilot tone level from the generator is monitored by a detector circuit
whose output will be indicated by LD2 (green for normal and red for failure), an d can, by closing LK2, operate the
alarm relay circuit if a failure occurs.

LNB DC power can be applied to the RF cable connection to the RWT-3810 by closing LK4 on the board and
applying the required DC voltage to SK3 on the rear panel.

SK3 pin 1 is the ground connection and pin 2 is the active connection. The circuit is not polarity sensitive.

The power supply comprises two bridge rectifiers whose rectified outputs are paralleled (positive and negative
respectively) to provide redundancy. The inputs to these rectifiers are two independent feeds of 28 Vac (centre tap
grounded). The rectified DC is regulated by three-terminal regulators. The DC indicator LED on the front panel is
wired in series with a zener diode between +12 and -12 Volts. The zener is to ensure that the LED extinguishes if
any one of the regulators fails.

IRT Communications

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3810-rwt.ib.rev1.doc Page 4 of 11 17/10/2007

RWR-3810 Photo-diode Receiver.

The RWR-3810 photo-diode receiver module consists of an optical detector diode circuit with integral pre­amplifier. Integrated attenuator and discrete amplifier circuits follows to set the output RF level of the system.

A RF gain control and RF monitor connector are provided on the front panel. The gain of the RF amplifier is
adjusted by the front panel control (RV3), which varies the bias on the attenuator circuit in the RF gain stage. The
RF level can be varied from –45dBm to –20dBm at the output RF connector for a correctly modulated RWR-3810
transmitter. The RF level at the front panel monitor connector is set at the same level as the rear panel RF output,
this allows the RF level to be checked as the RF gain is adjusted. This output should be terminated with the 75 ohms
termination provided when not in use.

The bias current of the optical detector diode is connected to a comparator circuit, which is used to provide received
optical signal indication. The circuit will light indicator lamp LD3 on the front panel for OPTICAL SIGNAL
indication (green for normal and red for failure), and with LK1 closed will operate a relay circuit, an ALARM
contact set is available as an external connection. The adjustment and connection data for this circuit is given in the
installation section of the manual.

A 10.7 MHz pilot tone detector circuit is provided which with the pilot generator circuit in the RWT-3810
transmitter will verify the RF signal path of th e system. The pilot ton e level is monito red b y a detecto r circuit wh o se
output will be indicated by LD2 (green for normal and red for failure), and can, by closing LK2, operate the alarm
relay circuit if a failure occurs.

The power supply comprises two bridge rectifiers whose rectified outputs are paralleled (positive and negative
respectively) to provide redundancy. The inputs to these rectifiers are two independent feeds of 28 Vac (centre tap
grounded). The rectified DC are regulated by three-terminal regulators. The LED on the front panel is wired in
series with a zener diode between +12 and -5.2 Volts. The zener is to ensure that the LED extinguishes if any one of
the regulators fails.

NOTE: Direct connections are made to the rear of the RWT-3810 and RWR-3810 modules for the

OPTICAL and RF cabling, these must be disconnected when a module is to be mounted or removed from the
IRT Eurocard mounting frame.

IRT Communications

www.irtcommunications.com