PSR Primary Surveillance RADAR

RAdio Detection And Ranging

RADAR

Radar

An electromagnetic system for detection and location of objects

First developed as detection device to earn the approach of hostile aircraft and for directing anti-aircraft weapons

Telemobiloskop

In 1904, Christian Hulsmeyer invents the _____. This is the first practical radar test.

shrimp boats

Controllers pushed plastic markers called “____” around the screen to track the movement of an aircraft.

Returned energy or echo or backscatter

The ____ or ____ or ____ is used to determine the direction and distance of the reflecting object

Transmitter > duplexer > antenna > electromagnetic wave > aim

Transmitting path

duplexer

The ____ alternately switches the antenna between the transmitter and receiver so that only one antenna need be used.

plan position indicator (PPI)

Radar signals can be displayed on the traditional ____ or other more advanced radar display systems.

Primary radar

Secondary radar

Classification of RADAR (2)

Primary radar

It transmits a high frequency signals toward the targets.

The transmitted pulses are reflected by the target and then received by the same radar.

Secondary radar

_____ units work with active answer signals.

This type uses a transponder on the airborne target/object

Pulsed radar

Continuous wave radar

Primary radar classification (2)

Pulsed radar

It transmits high power, high frequency pulses towards the target

Then it waits for the echo of the transmitted signal for sometime before it transmits a new pulse

Choice of pulse repetition frequency decides the range and resolution of the radar

MTI (Moving Target Indicator) Radar

Pulse Doppler Radar

Two broad categories of pulsed radar employing Doppler shifts are:

MTI radar

The ____ uses low pulse repetition frequency (PRF) to avoid range ambiguities, but these radars can have Doppler ambiguities

Pulse Doppler radar

_____ uses high PRF to avoid Doppler ambiguities. But it can have numerous range ambiguities

Continuous wave radar

____ continuously transmit a high frequency signal and the reflected energy is also received and processed continuously.

These radars have to ensure that the transmitted energy doesn't leak into the receiver (feedback connection)

unmodulated CW radar

An example of _____ is speed gauges used by the police. (Range not possible)

Modulated

a signal that constantly changes in frequency around a fixed reference is used to detect stationary objects. (Range can be calculated)

En-route radar

These radar sets initially detect and determine the position, course, and speed of air targets in a relatively large area up to 250 nm

L-Band

En-route radarsystems operate in ____ usually

Airport Surveillance Radar (ASR)

It is an approach control radar used to detect and display an aircraft's position in the terminal area.

25,000 feet (7,620 meters)

40 to 60 nautical miles(75 to 110 km)

ASRs are capable of reliably detecting and tracking aircraft at altitudes below _____ and within _____ of the airport.

precision approach radar

The ground-controlled approach is a control mode in which an aircraft is able to land in bad weather. The pilot is guided by ground control using _____. The guidance information is obtained by the radar operator and passed to the aircraft by either voice radio or a computer link to the aircraft.

Surface movement radar (SMR)

The ____ scans the airport surface to locate the positions of aircraft and ground vehicles and displays them for air traffic controllers in bad weather.

J- to X-band

Surface movement radars operate in _____ and use an extremely short pulse-width to provide an acceptable range-resolution.

En-route Radar

Airport Surveillance radar (ASR)

Precision approach radar (PAR)

Surface movement radar (SMR)

weather radar

Types of radar in aviation

accurately and reliably

The ability to ___ and ___determine the location of aircraft has a direct influence on the separation distances required between aircraft (i.e. separation standards), and therefore on how efficiently a given airspace may be utilised.

160 to 220NM (en route)
10 to 60NM (ASR)

Operational requirements

Range: ____ en-route; ____ ASR

Range resolution

Is the ability of a radar system to distinguish between two or more targets on the same bearing but at different ranges.

Width of the transmitted pulse

Types and sizes of targets

Efficiency of the receiver and indicator

The degree of range resolution depends on (3)

Angular resolution

___ is the minimum angular separation at which two equal targets can be separated when at the same range

Probability of detection

___ is the ratio of detected targets to the number of all possible targets on the radarscreen, i.e. all possible targetsin a given direction

greater than or equal to 80%

The radar must detect, with ____ probability at a defined range, a one square meter radar crosssection.

Mean Time Before Failure ( MTBF)

____ is the predicted elapsed time between inherent failures of a system during operation.

Failures of a system

Greater than 20,000 hours

MTBF can be calculated as the arithmetic mean(average) time between ____.

For primary radar: ____

Availability

> 99%

The percentage of the total operating time during which the system is performing to specification.

Should be: ___

Pulse Repetition Frequency (PRF)

The ___ of the radar system is the number of pulses that are transmitted persecond.

pulse-repetition time (PRT)

The time between the beginning of one pulse and the start of the next pulse

Approx 800-8600 Hz depending on burst mode and antenna revolution

PRF of STAR 2000

Frequency diversity

2.8 dB

_____ typically uses two transmitters operating in tandem to illuminate the target with two separate frequencies.

The received signals can be separately processed in order to maintain coherence.

In addition to the 3dB gain in performance achieved by using two transmitters in parallel, the use of two separate frequencies improves the radar performance by (typically) ____.

higher maximum range

high jamming immunity

With the multiple frequency radar procedure it is possible to achieve a fundamentally _____.

An important advantage of the multiple frequency procedure is the _____ of the procedure.

Blind speed

____ is a radial speed of the airplane at which the phase shifting of the echo-signal hasthe value ±n · 360°between two pulse periods

Transmitted frequency

PRF

The blind speed is dependent on the ____ and on the ___ of the radar unit

16

Increasing Range by 2 means increasing Transmission power (Pt) by ____ times

Antenna gain

The ratio between the amount of energy propagated in certain direction compared to the energy that would be propagated if the antenna were not directional (Isotropic Radiation)

Anisotropic

Most antenna emit (radiate) stronger radiation in one direction than in another. This antenna is referred to as _____

Radiation pattern

The energy radiated from an antenna forms a field having a definite ____

main beam (or main lobe )

The ____ is the region around the direction of maximum radiation (usually the region that is within 3 dB of the peak of the main beam).

sidelobes

The ____ are smaller beams that are away from the main beam

backlobe

One sidelobe is called _____.

Minimum Discernible Signal (MDS)

defined as the useful echo power at the antenna, which gives on the screen a discernable blip.

Minimum Detectable Signal (MDS)

The result of measurement conditions for the receiver sensitivity at a radar device. (Not standard. Depends on manufacturer’s specification.)

Update Rate

the rate at which the aircraft’s position is updated to users.

4 and 12 seconds

An update rate between _____

Fan-beam antenna

Truncated paraboloid or a circular paraboloid

is a directional antenna producing a mainbeam having a narrow beamwidth on one dimension and a wider beamwidth on the other dimension.

This pattern will be achieved by a ____ reflector or a ____ reflector

Not highly directional in one direction

Problem of fan-beam antenna

Cosecant Squared Antenna (Constant Height Pattern)

Antenna special designed for air-surveillance radarsets.

This permits an adapted distribution of the radiation in the beam and causing a more ideal space scanning.

This antenna pattern can get the required elevation coverage where the received power is independent of the radar range for a constant height target

Deformation of a parabolic reflector.

A stacked beam by more hornsfeeding a parabolic reflector.

An antenna group with either different spacing or different feeding of elements.

There are a couple of variation possibilities, to get a cosecant squared pattern in practice (3)

Highly complex design

Problem of Cosecant Squared Antenna (Constant Height Pattern)

Cassegrain antenna

In telecommunication and radar use, a ____ is an antenna in which the feed radiator is mounted at or near the surface of a concave main reflector and is aimed at a convex sub-reflector

Feed unit (a feed horn mostly)

In the Cassegrain Antenna, both reflectors have a common focal point. Energy from the ____ illuminates the secondary reflector, which reflects it back to the main reflector, which then formsthe desired forward beam.

bars

obstruction

Problem of Cassegrain Antenna:

The sub-reflectors of a Cassegrain type antenna are fixed by ___. These bars and the secondary reflector constitute an ____ for the rays coming from the primary reflector in the most effective direction

phased array antenna

A ____ is composed of several radiating elements each with a phase shifter

constructive/destructive interference

Beams are formed by shifting the phase of the signal emitted from each radiating element, to provide ____ so as to steer the beams in the desired direction.

Ability to permit the beam to jump from one target to the next in a few microseconds

120 degree sector

Phased array antenna

Advantage: Ability to _____

Problem: the coverage is limited to a _____ in azimuth and elevation

Linear arrays

Ray deflection only in a single plane possible

Arrangement of phased array antenna where These antennae consist of lines whose elements are fed about a common phase shifter.

Disadvantage: _____

Planar arrays

Complicated arrangement and more electronically controlled phase shifter needed

Arrangement of phased array antenna where These antenna arrays completely consist of singles radiating elements and each of it gets an own phase shifter.

Problem: ____

Rotating joint

Whenever a stationary rectangular waveguide is to be connected to a rotating antenna, a ____ must be used.

Circular waveguide

A _____ is normally used in a rotating joint

Reflections

Loss in overall efficiency

Any abrupt change in the size and shape in the waveguide interface can cause ____ and a ____.

E bend

H bend

1 The bend where E Fields are distorted.

2 The bend where H fields are distorted

Two 45-degree bends

Bends that are Quarter wavelength apart.

The reflections that occur at the bends cancel each other, leaving the fields as though no reflections have occurred.

Twisting

Sometimes the electromagnetic fields must be rotated so that they are in the proper phase to match the phase of the load. This may be accomplished by ____ the waveguide.

Two wavelengths

The twist must be gradual and greater than _____

dehydrator

a ____ will maintain a clean, dry, particulate-free environment within the waveguide.

encoder

Azimuth Change Pulses (ACP’s)

A mechanical or optical controlled “_____” is mounted at the revolving part of the antenna.

This produces _____

North Reference Pulse (NRP)

The counter gets a reset by a so called ____ once per revolution or ACP (Azimuth Reference Pulse.)

Drive system

Consist of Motor assembly, gear box and bearing ring gear, pedestal etc

Lubrication system

For moving parts maintenance, lubrication is performed periodically using specified grease and tools like grease-gun.

Aid landing

The first use of PSR technology involved using radar to ____

Ground controlled approach (GCA)

In 1943 US Air Force air traffic controllers began routinely using ____ equipment to help military pilots land safely in poor visibility.

15 planes per hour

Civil controllers first used military GCA equipment at LaGuardia airport in 1945, where it helped triple the landing rate to ___

ILS

In 1950 GCA were replaced with ___

Complete rotating antenna

GCA were improved with ___

Doppler effect

Modern air traffic control radars use the ____ to discriminate moving aircraft from stationary targets and to measure storm velocities.

Latency

_____ is the time it takes for a data packet to be received by the remote computer.

It should be real time

Redundancy

Can be accomplished by both channel redundancy, or natural redundancy though message repetition, or both

Quality

In order to achieve the maximum data throughput and minimum transmission delay, the size of the frame information field should be dynamically determined by transmission parameters such as _____ of channel used

Data Link Control (DLC)

The use of ____ supports the exchanger of radar related data and should provide error detection

Repetition codes

__ is a coding scheme that repeats the bits across a channel to achieve error-free communication.

Parity Bits

____ is a bit that is added to a group of source bits to ensure that the number of set bits (i.e., bits with value 1) in the outcome is even or odd

checksum

A _____ of a message is a modular arithmetic sum of message code words of a fixed word length (e.g., byte values)

Parity bits

Check digits

Longitudinal redundancy checks

Checksum schemes include (3)

Cyclic redundancy checks (CRCs)

____ is a non-secure hash function designed to detect accidental changes to digital data in computer networks; as a result, it is notsuitable for detecting maliciously introduced errors.

Burst errors

A cyclic code has favourable properties that make it well suited for detecting ____.

All Purpose STructured Eurocontrol Radar Information Exchange

ASTERIX

Relatively large amounts of data

Some natural redundancy, target reports being repeated every few seconds.

Real-time data, implying short transmission delays

The message structure ASTERIX shall be used to exchange radar related data which are characterised by: (3)

Data Categories

The data exchanged over the communication medium between the different usersshall be classified into ______

identification

application task

priority

The purpose of such a classification in ASTERIX shall be to:

Allow easy _____ of the data;

Facilitate the dispatching of the data to the appropriate _____ in the receiving unit;

Establish a certain hierarchy among the data based on their ____