Air Traffic Systems‘An air-force in miniature on just one Station' (1970’s)

Airfield EquipmentsWhere do we start ?

Airfield EquipmentsWhere do we start ?

Where are our Aircraft ?

RADAR

RAdio

Direction

And

Ranging

Purpose of the Watchman Radar

The Watchman Radar has 2 roles:

2. Approach Radar

1. Airfield Surveillance Radar (ASR)

Introduction

Fibre OpticCable (4km max)

Radar Head

ATC

TX SPR

Tx

RVUDIU

DFTI

Rx

Range

Crown Watchman System used by RAF has a maximum range of 60Nm

Used by the Navy at Naval Air Stations up to 80Nm

Gibraltar and Cyprus have “enhanced” systems capable of 120Nm

0 15 30 45 60

Frequency

Operates in the S Band of frequencies 2 to 4 GHz (NATO E/F Band)

This means the wavelength is approximately 10cm

Frequency

‘S’ band radar

Working frequency– between 2.705 – 3.05 GHz

Wavelength– approx. 10 cm

Pulse Repetition Frequency

With “Uniform” triggering, the PRF is 1,100 pulses per second (pps)

This means that the Pulse Repetition Interval (PRI) is 909µs

Transmitter Characteristics

MOPA Configuration (Master Oscillator – Power Amplifier)

- Master Oscillator = 70MHz crystal

- Power Amplifier = Travelling Wave Tube (TWT)

Master Oscillator

70 MHz is multiplied & mixed with a Local Oscillator to give our operating frequency

Power Amplifier - TWT

Efficiency

– The TWT is only 20% efficient, the other 80% dissipated as heat

Cost

– A new TWT cost around £100,000 (can be refurbished – identified by being blue in colour and may have a suffix ‘R’ after the serial number).

Disadvantages of the TWT

Power Amplifier

Travelling Wave Tube (TWT)

RF In

RF Out

Heater

GridCathode Collector

Helix

Power Amplifier

So why use a Travelling Wave Tube (TWT)?

- Bandwidth – Wide band so we can transmit at different frequencies

- Stability - Very stable across the frequency range

Travelling Wave Tube

TWT Output Power

• Peak Output Power = 50 - 55 kW

• Mean Output Power = Approx 1 kW

Aerial

• The Aerial consists of a parabolic reflector and 2 horns

- The Main Beam horn

which is used for Tx

and Rx

- The Aux Beam horn

for Rx only

Aerial Properties

The Aerial rotates at 15rpm (4 Seconds)

It can survive wind speeds of up to 70 knots while operating

If switched off and left to weathercock, it can survive up to 120 knot winds

Signal Processing Rack

The Signal Processing Rack (SPR) has several functions:

- It houses the Tx Driver, Receiver and X-Site Link

- It carries out all the signal processing for the system

- It performs system timing and control functions

Signal Processing

4 video channels in the watchman system

3 processed video channels– Normal Radar Video (NR)– Ground Clutter Filter (GCF)– Moving Clutter Filter (MCF)

1 unprocessed channel– Background Video

Radar Viewing Unit

Console itself, serving a number of sensor inputs

Accepts input from Radar

Performs some processing and Displays on PPI

Enables ATC controller functions

Display Monitor

Processor Unit

WATCHMAN RDS 1600 DISPLAY

Display

Processor Unit

23

WATCHMAN RDS 1600 DIST UNIT

20

WATCHMAN RDS 1600 KEYBOARDAND TRACKERBALL ASSY

24

AIRFIELD RADAR INTEGRATION PROJECT

(ARIP)

Why ARIP?After the September 11th attacks in the USA, it was decided to augment the UK’s Air Defence network by feeding in Airfield Radar pictures to the Control & Reporting Centres (CRCs)

RAF HQ Strike Command

Site 1

ARIP Telecoms Concept

SSR PSR

Main

SSR PSR

Standby

RAF Scampton

RAF Boulmer

ISDN 2 ISDN 2

Site 2

SSR PSR

Main

SSR PSR

Standby

ISDN 2 ISDN 2

Site 3

SSR PSR

Main

SSR PSR

Standby

ISDN 2 ISDN 2

Site 4

SSR PSR

Main

SSR PSR

Standby

ISDN 2 ISDN 2

Site 21

SSR PSR

Main

SSR PSR

Standby

ISDN 2 ISDN 2

Site 22

SSR PSR

Main

SSR PSR

Standby

ISDN 2 ISDN 2

Site 23

SSR PSR

Main

SSR PSR

Standby

ISDN 2 ISDN 2

Roving RX (Air Defence Battery)

Roving Tx

SSR PSR

Main

SSR PSR

Standby

ISDN 2 ISDN 2

ISDN 30ISDN 30 ISDN 30ISDN 2

Mobile phone

(?)

Roving RX (briefing and Co-ordination)

ISDN 2

Dial-up ISDN connections

ARIP WATCHMAN DISPLAY REPRESENTATION

Airfield layout

Any Questions?