Ttr –920 tcas II receiver transmitter

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  • No forced air-cooling.

  • High reliability.

  • Installation flexibility.

  • On-board maintenance system.

  • Enhanced maintainability.

The TTR –920 TCAS II receiver-transmitter contains all rf surveillance and collision avoidance processing functions for the TCAS system. It interrogates the ATC transponders in all nearby aircraft and calculates their location from the  bearing, range and altitude data derived from the transponder replies. This interrogation/reply process continues as long as the TCAS and transponders can maintain two-way communications. Intruder aircraft track information is sent to a cockpit-mounted traffic display via an ARINC 420 high-speed data bus. The collision avoidance processing section of the TTR-920 continuously monitors this track information and detects any potentially traffic situation. When a potential conflict is detected, appropriate aural and visual alerts are issued to the flight crew. If the situation war rants, recommended avoidance guidance is also displayed in the cockpit.


  • No forced air cooling

Advanced in L-band power amplifier technology, together with a unique whisper/shout attenuator design and a high efficiency transformerless ac power supply, have reduced the internal power dissipation so that no forced air cooling is required for the TTR-920. Therefore, the TTR-920 can operate satisfactory in all types of equipment cooling systems including those specified by ARINC 404 and ARINC 600.

  • High reliability

The TTR-920 is designed for a significantly higher reliability than normally expected with equipment of this complexity. As a normal part of the design phase, reliability demonstration tests are used to verify design predictions. A high confidence factor in the correlation of the predicted vs demonstrated MTBF comes from design criteria which are based on low power dissipation, component derating, decreased part count, large scale integration, surface mount technology and good thermal design.

  • Installation flexibility

The CollinsTTR-920 is designed for installation in a variety of different aircraft types involving a variety of different system architectures. The advanced technologies utilized allow the design to provide nearly universal installation capability, interfacing with all analog equipment per ARINC 5XX and digital equipment per ARINC 7XX. This will accommodate the older aircraft fleets as well as the newer aircraft installation.

  • Interface with on-board maintenance systems

Some newer aircraft types have a standard equipment, on-board maintenance systems (OMS). These systems interface with all installed LRUs to established the operational status of various aircraft systems. The TTR-920 properly interfaces in all of the on-board maintenance systems currently defined in ARINC 604.

  • High capacity nonvolatile fault memory.

Maintainability is enhanced by a comprehensive self-test and a high capacity, nonvolatile fault memory. The unit continuously monitors its own performance during normal operation and automatically provides for current status reporting. Self-test can be manually initiated from the TTR-920 front panel. A maintenance display located on the front panel of the unit will indicate the current system status to the LRU level when the manual self-test is initiated. The contents of the nonvolatile memory can be accessed in the shop to obtain a history of all performance information in addition to current operational status. The nonvolatile memory records LRU failure to the functional subassembly level for simplified maintenance action.

  • Built-in module extender

The TTR-920 is functionally partitioned into plug-in modules, which allows for easy disassembly, troubleshooting and reassembly. A built-in module extender is provided to assist troubleshooting all digital circuit assemblies.

  • Ada software program language

The aviation industry has standardized on Ada high-level software program language. This language offers significant advantages in software structure, testability and maintainability. The TTR-920 utilizes Ada for all surveillance and TCAS logic software.

  • Whisper/shout attenuator

The whisper/shout attenuator is used to control transmitted power of the interrogation signal. It is capable of attenuating the transmitter output from 0 to 26 dB in one –dB steps. The TTR-920 implementation uses selective modulation of the four devices in the transmitter output stage for the large steps in the 0-26 dB whisper/shout attenuator. This unique method permits a single, low insertion loss verger attenuator stage for the l-dB steps, and results in reduced transmitter stress and reduced cooling requirements.

  • TCXO frequency source

The frequency source is a one-channel L-band synthesizer, that provides a 1030-MHz signal when the phase-locked loop is locked. The frequency source is built on the same high dielectric powdered ceramic microstrip board as a the transmitter.

  • Four-channel beam steering network

The antenna beam steering network automatically detects and corrects for phase errors resulting from the differences in antenna cable length or connector characteristics. ARINC 735 specifies 2.5 dB + 0.5 dB insertion loss for the directional antenna coax cable installation. However, the TTR-920 can accommodate cable insertion loss from 0 dB to 4.0 dB. The individual coax cables to the directional antenna must comply only with the 4-dB maximum loss specification. The four cables need to be matched only to within one electrical wavelength at the TCAS operating frequency, about 7 to 10 inches, depending on cable propagation velocity.

  • Antenna flexibility

The TTR-920 can accommodate either a directional antenna or an omnidirectional antenna mounted on the bottom of the aircraft fuselage. This is a customer option. A directional antenna mounted on the top of the aircraft fuselage is a system standard.

This technical description is divided into electrical design, software design, monitor/self-test description, mechanical design and TCAS III growth provisions.


The TTR-920 electrical design consists of rf circuits, digital circuits and power supply.
RF Circuits
The rf circuits consists of the transmitter, modulator, receiver, if section, frequency source, whisper/ shout attenuator, beam steering network, transmit/receive/cal switch, top/bottom antenna selector switch, BITE oscillator and modulator, and video processor. The rf circuits are housed in two assemblies within the receiver-transmitter (rt). One assembly contains the low-pass filter, top/bottom antenna selector switch, beam steering network, the transmit/receive/cal switch and the receiver front end. The second assembly contains the transmitter, the whisper/shout attenuator, the frequency source, BITE oscillator and the modulator.
The transmitter consists of six stages, the first stage is class AB and the last five stages are class C. The nominal output will be 1850 watts peak pulsed power at 0.03% duty cycle over the temperature range of the unit. The first stage will have an input power of +17dBm.
The first stage of the transmitter is a class AB common emitter amplifier with a 600-mW output and 10 dB of gain. The second stage is a class C common base amplifier with a 4-3watt output and 9 dB of gain. The first and second stage collectors are fed a 28-volt peak bracket pulse. The output of the second stage is fed into a “T” high-pass filter and then into the emitter of the third stage. The third stage is a class C common base amplifier with a 26-watt output and 7 dB of gain. The fourth stage is a class C amplifier with a 100-W output. The fifth stage, also a class C amplifier drives a 90- degree hybrid splitter which in turn feeds two 90 degree hybrid splitters. This results in four outputs of equal amplitude. Each of these outputs is fed to a 500-W class C stage that is identical to the fifth stage. The splitting process is then reversed and the signals are combined for an output of 1850 watts peak after considering combiner and mismatch losses. This design provides good control of pulse rise and fall times and protects against oscillations and transients.
The modulator consists of seven sections, five 35-amp stages, a 10-amp stage and a 0.5 amp stage. The first is driven by a bracket wave form. The last six stages are modulated by the pulse data itself. Each of the five high-power stages consist of two MOSFET transistors in cascode driving a high current MOSFET. This amplifier is in the switch mode during transitions and until the output of the amplifier reaches 43 volts, at which point an active feedback network is triggered to regulate the output. This design the capacitor storage bank size, and compensates for temperature variations.
The receiver front end consists of three sections; a bandpass filter, a low-noise amplifier and a mixer. This circuit is identical for each of the four rf channels. The bandpass filter is centered at 1090 MHz and has a bandwidth of 25 MHz with an insertion loss of 2dB. The signal rejection at 1030 MHz is 45 dB minimum. The low-noise amplifier is used to keep the receiver noise figure down to less than 12 dB. The low-noise amplifier provides 24 dB of reverse isolation to help reduce the local oscillator radiation to under –79 dBm. The mixers are doubly balanced ring diode mixers that are used to convert the 1090-MHz rf signals to 60 MHz. The four 60-MHz signals are fed through the microstrip circuit board to the if board using low capacitance feed-throughs. A +7-dBm, 1030-MHz local oscillator signal is fed to each mixer. The four local oscillator signals are applied from a single four-way in-phase power splitter.
The if section operates at two if frequencies, 60 MHz and 17,5 MHz. The first is section consists of four channels, one for each of the directional antenna elements. Each channel contains a 60-MHz linear amplifier, a 60-MHz surface acoustic wave (SAW) bandpass filter, another 60-MHz linear amplifier, and a two-way splitter to direct half of the signal to a hybrid combiner and half to a mixer circuit. The hybrid combiner accepts the output from each of the four channels and directs the summation to a 70-dB dynamic range logarithmic amplifier. The output of the log amplifier is a video pulse, which is provided to the video digitizer circuit and also is used as a trigger for gating the angle of arrival determining circuitry.
The mixer and second if section continue the four receiver channels. The output of the first if is mixed with 77.5 MHz to provide a 17.5-MHz signal, which is applied to a limiting amplifier, which limits at approximately –80 dBm. The output of the limiting amplifier is applied t each of two-phase detectors, which compares the phase of adjacent antenna elements. A multiplexer selects the phase detectors appropriate to the sector being interrogated and directs these signals to flash A/D converters, which convert the phase information to an 8- bit digital signal. The digital outputs are sampled at an eight MHz rate and loaded to random access memory, which can be read by the signal processing circuitry.
The frequency source is a one channel L-band synthesizer. It is built on high dielectric powdered ceramic microstrip board. The design requires no external tuning and is highly reliable.
The beam steering network has four outputs that are connected to the four antenna elements, through the top/bottom switchers. The phase of the four output signals is used to shape and point the beams in each of the four directions and to generate the omnidirectional pattern.
The transmit/receiver/cal switch is a solid-state rf switch that connects the antenna to the receiver in the receive mode and to the power amplifier in the transmit mode. It also connects the BITE oscillator to either the receiver or antenna elements through the beam steering unit.
The top/bottom switch is a solid-state rf switch that connects the output of the beam steering network to one element of either the top or bottom directional antenna. The bottom antenna terminals have a built-in 7-dB attenuation. This feature allows the use of either an omnidirectional or directional antenna on the bottom without requiring external terminations if a single omnidirectional antenna element is used.
The BITE oscillator and modulator are used for calibration of the intermediate frequency phase detectors and to compensate for variations in cable lengths between the receiver-transmitter and the antenna.
The video digitizer circuit accepts the video output of the log amplifier and conditions the signal to a series of digital pulse for use by the signal processing circuitry. This circuit sets the minimum threshold level to discriminate against low-level signals, rejects narrow pulses, and rejects slow rise-time pulses.
Digital Circuits
The TTR-920 signal processing circuits feature:

  • Custom gate arrays

  • TMS320 microcontroller

  • Surface-mounted device technology

  • AAMP microprocessors

  • Ada high level language

  • Multiple bus structure

The digital circuits consists of the CPU signal processor and L/O Processor functions.

The CPU hardware consists of three advanced architecture microprocessors (AAMP, each with local RAM, EPROM and EEPROM memory resources and an interrupt controller connected to a local operating bus. One of the processors is also connected to the system I/O circuit. Each processor’s local bus is connected to the global bus through a buffer. With access to this bus controlled by a bus arbiter. Also connected to the global bus is RAM for interprocessor communication, EEPROM for fault storage purposes and the system timer interrupt circuit.
The signal processor consists of a TMS 320C25 controller, memory resources, system I/O, a Mode S signal processor ASIC, a Mode C signal processor ASIC and a Transmit Encoder ASIC. The controller provides the mechanism for controlling the flow of information within and among the various peripherals.
The system I/O orchestrates the transmitter/receiver operation, controlling the whisper/shout attenuator, beam steering, top/bottom and transmit/receive switches in the rf module. Additionally it controls the operation of the Mode S, Mode C and Transmit Encode ASICs.
The Mode S signal processor ASIC performs the functions of Mode S message sync detection and lock, bit decode, message error detection and correction and range measurement. This circuit receives serial data from the rf module and provides corrected, formatted data to a FIFO buffer along with the value of the range counter associated with the reply.
The Mode C signal processor ASIC performs the functions of Mode C message framing pulse detection, bit decode, message confidence estimation and range measurement. This circuit is capable of decoding messages even in the presence of overlapping and interleaved replies from more than one transponder. The circuit receives serial data from the rf module and provides a range value and formatted data and associated confidence bit for each of the Mode C altitude bit positions into a FIFO buffer.
The Transmit Encoder ASIC provides the modulation stimulus for the tansmitter for both Mode C and Mode S interrogations, controls the operation of the Mode S and Mode C processors, and provides test patterns for use during BITE testing of the receiver/transmitter.
Bearing measurement is made by associating the pulse reply time with the phase angle data stored in the “Bearing RAM” by the rf circuitry. Each pulse will have one or more measurements of bearing stored in a location of RAM related to the time of arrival. By reading the range associated with a reply, the location of the bearing data for each pulse can be calculated; and this data can in turn be used to calculate the bearing from which the pulse was sent.
The I/O hardware provides the TCAS rt external interface. This I/O consists of a number of ARINC 429 buses, discrete inputs and outputs, synchro receiver, analog to digital converters and a voice annunciator output.
Power Supply
The off-line power supply module accepts 115 volt, 400 Hz primary power and converts it to the dc voltages that are needed within the TCAS II receiver-transmitter. The supply generates +72, +62, +30, +15, +12, +9, +5, -5, -12 and –15 V dc. A quad power supply monitor with a 5-V logic output is used to monitor the +62, +30, +5 and –12 volt outputs. The power supply is designed for reduced weigh and improved efficiency by eliminating the traditional 400 Hz input transformer. 115 V ac primary power is rectified and applied to the input of a dc-dc flyback converter which supplies the appropriate dc voltages. Regulation is performed by a pulse width modulator IC, thus requiring no preregulation. The regulator uses a high voltage FET to switch the rectified primary power at approximately 80 kHz, leading to the reduction in size of magnetic components and filter capacitors.
This section gives a high-level description of the software structure and identifies the major processes and interfaces of the TCAS software. The software consists of the following processors: RF Signal Processing, ATCRBS Surveillance, Mode S Surveillance, Collision Avoidance, Performance Monitoring and Self-Test and I/O Processing. The TCAS shows the relationship of these processes and the interfacing data.
RF Signal Processing
RF Signal Processor conditions and transfers data between the hardware and the TCAS application software. A description of this process is in the following paragraph.
The Signal Processor module provides a preprocessor type function between the System Software (operating on the CPU hardware) and the rf module. The Signal Processor accepts tasks from the System Software, executes the low-level details of those tasks and then returns the results to the System Software. The System Software interface is implemented through dual port read-write memory (RWM). The rf module interface contains he serial data and discret lines necessary to calibrate, test and control the rf circuitry and antenna. The Signal Processor functions are controlled by a TNS320C25 signal processor. The Mode S and Mode C processes are implemented in custom gate arrays. The firmware is written in C and assembly language, since an Ada compiler is not available for the TMS320C25.
ATCRBS Surveillance Processing
This process correlates and tracks aircraft equipped with Air Traffic Control Radar Beacon System (ATCRBS) transponders. The process uses one algorithm for aircraft that report altitude and another algorithm for aircraft not reporting altitude. The input to the process consists of two data buffers that are updated by the rf signal processing as a result of the whisper/shout interrogation replies. One buffer contains range ordered replies from altitude reporting aircraft and the other buffer contains range ordered replies from the non-altitude reporting aircraft.
ATCRBS surveillance attempts to correlate each reply to established tracks. Replies that cannot be correlated are evaluated for formation of new tracks. Provisions are made to eliminate replies that appear to be caused by ground reflection. The output of ATCRBS surveillance are entries into the Intruder Surveillance Buffer. Each entry consists of a reply that correlates to an established track. Intruder Surveillance Buffer entries contain range, altitude, bearing and other target data.
Mode S Surveillance Processing
The Mode S Surveillance process monitors the passive Mode S replies which consists of squitter and altitude replies from other Mode S aircraft. If sufficient passive replies are received, Mode S Surveillance interrogates the target to acquire altitude and range. Once a target has been acquired, additional interrogations are made to obtain bearing information. The target will continue to be tracked until it is out of surveillance range. The output of Mode S surveillance is similar to that of ATCRBS Surveillance entries into the Intruder Surveillance Buffer.
Collision Avoidance Processing
The Collision Avoidance process performs additional target tracking and track data smoothing. The two main inputs to the collision avoidance process are Intruder Surveillance Buffer generated by the surveillance processes and the Own Aircraft data buffer. Once the targets have been tracked, each target is evaluated to detect if the target is a threat. IF the threat target is a TCAS equipped aircraft, then an air-to-air data link is established to coordinate the resolution of the threat condition. Details of the collision avoidance algorithms are specified in DO-185, Volt II.

I. Find in the text English equivalents for the following words and expressions:

запрашивать ответчик, обнаружить любую опасную ситуацию, принудительное охлаждение, высокий фактор доверия, использование передовых технологий, ремонтоспособность улучшена, самопроверка может быть инициирована вручную, встроенный модуль расширения, представлять значительные преимущества, направленная и ненаправленная антенна, гибридный сумматор, калибровка фазовых детекторов промежуточной частоты, устройство обработки сигналов, измерение пеленга, блок независимого источника питания.

II. Answer the following questions:

  1. What does the TTR-920 interrogate and calculate?

  2. What is issued to the flight crew when a potential conflict is detected?

  3. Where does a high confidence factor come from?

  4. Maintainability is enhanced by a comprehensive self-test and high capacity, isn`t it?

  5. When does the unit continuously monitor its own performance?

  6. How can self-test be initiated?

  7. Why does the nonvolatile memory record the failure?

  8. What is a built-in module extend provided to?

  9. What can the antenna beam stearing network automatically detect and correct?

  10. What does the TTR-920 electrical design consist of?

  11. Where does the hybrid combiner accept the output from?

  12. How is bearing measurement made?

III. Give Russian equivalents for the following expressions from the text:

maintainability is enhanced, the advanced technologies utilized, to offer significant advantages, calibration of the intermediate frequency phase detectors, directional and omnidirectional antenna, to interrogate the transponder, higher reliability, the nonvolatile memory, forced air cooling, self-test can be manually initiated, the hybrid combiner, a built-in extender, a high confidence factor, to detect hazardous traffic situation.




Aircraft transponders CO-70 and CO-70-144 operate with foreign ATC RBS secondary radars with a view to controlling the aerodrome and en-route traffic.

The secondary radar system comprises both the aircraft and ground equipment. The ground radar interrogates the transponders of aircraft within its coverage. Interrogation is accomplished by two-pulse interval codes. In reply the aircraft transponders send coded trains whose structure is dictated by the operating mode.

The secondary radar antenna pattern embodies minor lobes in a horizontal plane caused by the definite geometrical dimensions of the antenna, effect of clutter, etc. Radiation power of the minor lobes is sufficient for interrogating the aircraft transponders even at a substantial distance from the radar. As a result, auxiliary blips appear in wrong azimuth and the aircraft transponder gets ineffectively overloaded.

Suppression of interrogation caused by these minor lobes is based on artificial blanking of the transponder receiving channel at a proper time. For this purpose, use is made of a three-pulse suppression system. In order to insure suppression of the minor lobe interrogation signals, the radar should be equipped with two transmitters or a SHF antenna switch. For its operation the suppression system depends on comparing of amplitudes of the code and suppression pulses.

Skeleton Diagrams of Transponder

The transponder receives interrogation signals of the secondary radars at a frequency of 1,030 + 2.5 MHz which are passed through the HF unit to the receiver mixer. At the same time, the mixer receives the 1005.6 MHz signal delivered from the local oscillator. IF signals of 24.4 MHz picked off the mixer output pass to the logarithmic IF where they are amplified and rectified and delivered to the integrating unit. Then, the signals shaped in amplitude and width are delivered from the integrating unit output to the encoder. The latter decodes the interrogation codes and generates a reply code containing information about either the aircraft number or flight altitude depending on the interrogation code.

The aircraft number code is chosen by the pilot on the control panel depending on the conditions of flight.

Altitude data is delivered to the encoder to the altitude converter which transforms the flight altitude analog voltage into a code.

Then, coded signals pass from the encoder output to the modulator and, then, to the oscillator generating response HF pulses at a frequency of 1,090 + 3 MHz. Afterwards, the HF signals are delivered from the transmitter output to the antenna through the HF unit. The transponder feeds on 115V, 400 Hz and +27 V.

Functional Diagram of Transponder

Antenna AM-001 provides for receiving and transmitting signals at frequencies of 1,030 and 1,090 MHz. The antenna is a quarter-wave vertical dipole which is usually installed in the middle of the fuselage bottom. The antenna features an input resistance of 50 ohms and travelling-wave ratio not less than 0.7

The HF unit comprises a set of coaxial line sections which serve to separate both the transmitter and receiver frequencies and a preselector and test coupler.

Separation of frequencies of 1,030 and 1,090 MHz is effected through sections of the coaxial lines whose length is selected so that input resistance of the sections is high enough when a signal of one frequency is passing and is low when a signal of the other frequency is going through.

In the HF unit provision is made for a coupler with an attenuation of 20 dB to check the transmitter output and receiver sensitivity.

The preselector of the HF unit comprises four coaxial coupled circuits insuring a passband of at least 10 MHz relative to a frequency of 1,030 MHz and selectivity not less than 60 dB at detuning by 25 MHz.

The local oscillator incorporates a master crystal-stabilized oscillator, frequency trippler, amplifier stage, and multiplied-by-7 stage. The last stage employs diode 1A401B and is constructionally located in the preselector. The local oscillator employs transistors, type 1T311Г, with output being least 0.5 mW.

Used as a mixer is a diode 2A102A connected into the coaxial circuit coupled with the local oscillator and preselector. The local oscillator causes a current of at least 0.15 mA in the mixer diode.

The IF amplifier features a intermediate frequency fi of 24.4 MHz and passband of 7 to 8.5 MHz. The amplifier comprises eight stages connected in a stagger-tuned pair circuit. The amplifier has a logarithmic amplitude response within a dynamic range of 50 dB owing to three independent detector diodes at the outputs of the fourth, sixth and eight stages.

The IF amplifier insures a maximum output voltage of 6 V at an output noise level of 0.25 W. The amplifier employs transistors 1T311A installed on an individual strip.

A signal picked off the IF amplifier output is passed to the amplitude comparator of pulses P1 and P2 which compares the amplitude of pulse P1 of the interrogation code with the amplitude of suppression pulse P2. If the amplitudes are equal or that of pulse P2 exceeds the amplitude of pulse P1 towards the minor lobe, the comparator passes both pulses P1 and P2. In this case the three-pulse suppression sharper forms a pulse to blank the circuits for deciphering codes A,B and C. Thus, the transponder interrogation caused by the minor lobes is reliably suppressed by the minor lobes of the radar aerial directional pattern.

If the amplitude of pulse P1 exceeds that of pulse P2 by 9 dB towards the major lobe, the first circuit passes pulse P1 only and the second circuit does not shape the blanking pulse.

The inhibition circuit provides for disabling the normallizer input when the SUPPRESSION (СУПРЕССИЯ), LOAD LIMIT (ОГРАНИЧЕНИЕ ЗАГРУЗКИ), BLANK Σ БЛАНК Σ ), or SBY pulse is applied. The SUPPRESSION signal insures suppression of the interference caused by the transponder through its input while a reply signal is generated.

As the number of interrogation codes exceeds a specified value (1,300 Hz), the transponder blanking time increases so as to keep the number of the reply trains constant.

When is the SBY operation, the transponder is blacked through the input while it remains fully ready for operation. When the mode selector (РЕЖИМ РАБОТЫ) is thown to A, B or C from the SBY position, a reply signal appears instantly at the transponder output.

The shaper forms the interrogation code pulses in amplitude and width.

The interrogation decoding circuits are switched over from the transponder control panel.

Codes A and C are coded in mode A, codes B and C in mode B and code C only in mode C.

Decoding is accomplished by means of the AND (И) diode circuits and delay line. After any code is decoded, a crystal calibrator gets trigged to provide for writing complete pulses in the register. Besides, when codes A and B are being decoded. A pulse is generated for interrogating the aircraft number commutator.

When the code C is decoded, a pulse is shaped to trigger an interrogation amplifier of a shaft position-to-digital converter.

The suppression circuit insures disabling of the transponder by pulses from the operative peripheral systems and shaping of an own pulse to blank the other systems during transmission of a reply signal.

The load limiter insures the transponder against overloading due to rise in the number of the interrogation codes. At a normal repetition rate of interrogation codes the load limiter blanks the transponder input through the inhibition circuit only for the time of transmission of a reply code. But, if the repetition rate of the interrogation codes exceeds the specified limit (about 1,300 Hz), the blanking time increases so as to keep the number of replies constant.

  1. Find in the text English equivalents for the following words and expressions:

работать с чем-либо, включать что-либо, заключать в себе, подавление запроса ответчика, искусственное бланкирование, 3-х импульсная система подавления, быть оборудованным чем-либо, отличаться от, осуществлять (связь) через что-либо, преобразование, для декодирования запросных кодов, вертикально-поляризованные сигналы, поступать в шифратор, входное сопротивление, чувствительность приёмника, запирание ответчика, при помощи чего-либо.

  1. Answer the following questions:

  1. What equipment do aircraft transponders CO-70 and CO-70-144 operate with?

  2. What does the secondary radar system comprise?

  3. What does the secondary radar antenna pattern embody?

  4. What is the difference between transponders CO-70 and CO-70-144?

  5. Is coupling between the particular units and peripheral system accomplished through a stock mount or junction box?

  6. What are the main purposes of particular units?

  7. Who(m) is the aircraft number code chosen by?

  8. Where do the coded signals from the encoder output?

  9. What does the local oscillator incorporate?

  10. What does the amplitude comparator of pulses P1 and P2 compare?

  11. In what way does the sharper form the interrogation code?

  12. By what means is decoding accomplished?

III. Give Russian equivalents for the following expressions from the text:

to differ from, suppression of interrogation, artificial blanking, vertically-polarized signals, to pass from, the twin set of transponders, a three-pulse suppression system, for decoding the interrogation codes, to pick off a signal, an input resistance, to blank a transponder, to deliver to the encoder, to embody smth, to comprise smth, to accomplish through, to connect into the coaxial circuit, to be equipped with, to have a logarithmic amplitude response.


Radio detection and Ranging (Radar) is the art of locating the presence of an object by radio means, determining their angular position, with regard to some reference point and their range.

In order to accomplish this, a beam of R.F. energy is directed over some are given in search of a target, by means of a highly directional rotatable aerial. If the beam strikes the target some of R.F. energy is reflected and a small portion of this reflected energy travel bask in the direction of the transmitter.

If a sensitive receiver, capable of detecting this reflected energy is arranged to operate in the vicinity of the transmitter, together with some time measuring device capable of measuring the extremely short periods of time elapsing between transmission o the extremely short periods of time elapsing between transmission of the energy an reception of reflections (Echoes), the following information can be deduced when echoes are obtained.

Some reflecting body (in Radar terminology "a Target") has found by the beam, a demonstrated by the echo received at the receiver and recorded by the time measuring device.

It can be shown that the range or distance of the target from the transmitter is proportional to the time interval, measured from the instant that transmission of energy commences, to the instant at which the returning echo is received.

The bearing of the target, measured with reference to the direction of the ship's head, or in the case of a shore station, measured from compass North, is indicated by the angle through which the aerial must be rotated, in order that the centre of the beam may face the target.

The elevation or height of an airborne target can be obtained, under favorable conditions, by measuring the angle of elevation by which the aerial must be tilted in order that the centre of the beam may face the target, and by simultaneously measuring the slant range thus obtained.

Requirements for the Basic Radar System. The minimum requirements for the basic Radar System are therefore:

  1. A suitable transmitter.

  2. A very sensitive receiver.

  3. A device capable of measuring short intervals of time of the order of a microseconds or less.

  4. An aerial system having highly directive properties and capable of being rotated through any desired angle. If designed for use against airborne targets it must be capable of being tilted to an extreme elevation of at least 45 degrees.

The pulse length, or diration of each pulse (microseconds), and the rate at which successive pulses are repeated (repetition rate or pulse frequency) are determined in design by the performance and duties which a particular Radar system is required to fulfil.

Radar information

This equipment falls in two separate categories, airport surveillance radar (ASR) and precision approach radar (PAR). Each is a separate and distinct functions. Together, these radar equipment from the ground controlled approach system.

Both operate on the same principle. Extremely short bursts of radio energy are generated by a special radio transmitter and fired into space from a highly directional antenna system. As these bursts of energy, or pulses, strike reflecting objects in their path, such as tall buildings, tanks, radio towers, and airplanes, a minute portion of their energy is reflected back to the transmitter location where it is picked up and amplified by a sensitive receiver.

An accurate electronic “stop watch ” measures the time required for the pulse to travel to each reflecting object and return to the receiver. Since these pulses travel at speed of light, these time intervals are extremely short, being measured in microseconds, or millionths of a second.

Another ingenious component of the equipment translates this information into polar coordinates and presents it to the operator as spots of light, or “pips” on the face a cathode-ray tube, or “scope”. These pips accurately represent the position of each reflecting objects in terms of azimuth angle and distance from the transmitting antenna. The location of the transmitting antenna is indicated on the scope as a reference of light.

Here the similarity between ASR and PAR ends. ASR is primarily useful as a traffic-control instrument, since it gives the airport controller an accurate map of the control area showing the position of aircraft within a radius of 30-60 and up 8000-10000 feet. It generates map by continually rotating its antenna through 360 degrees, successively striking targets and painting each pip in the proper on the fluorescent scope face.

Since the fluorescent coating continues to glow for some time after being activated , the controller has a continuous picture of the traffic which is revised every 2 seconds as the antenna revolves.

While the PAR utilizes the same basic principles, it is designed to perform an entirely different function. It monitors the progress of an airplane on approach to the instrument landing runway in range, azimuth, and elevation above the ground. Since it interested in nothing beyond the final approach path, the azimuth antenna scans through a 20-degree arc covering this path, rather than revolving continuously through 360 degrees. A similar antenna scans through a vertical arc of 6 degrees to give elevation information.

A high degree of accuracy is south and achieved in the PAR equipment. The high transmitter frequency (9,100 megacycles per second) has been chosen to make practical a beam of extreme sharpness which results in the best possible definition and resolution of reflecting objects. The angular motion of scanning is rapid, giving practically continuous revision of the picture.

Accuracy is further increased by the method of presentation. Since it is only necessary to see 20 degrees in azimuth and 6 degrees in elevation, these triangular segments in presentation to occupy almost the full area of the scope face.

The position of a landing may thus be determined within approximately 20 feet in elevation, 40 feet in azimuth, and 300 feet in range when the aircraft is 1 mile from the end of the runway. The accuracy of these factors increases as the aircraft approaches the end of the runway.

To use this equipment to the fullest extent, a transparent map is superimposed on the face of the surveillance scope on which are engraved points and lines to represent radio fixes and paths that are useful from the air traffic pattern point of view. A similar map carrying lines to indicate the correct glide path and runway extension line is placed over the precision scope.

While the pilot need not know the foregoing fundamentals in order to execute an approach, a knowledge of them will certainly be helpful, since he will know what is going on at the ground of the system.

To utilize this equipment for the pilot`s benefit, it is necessary to analyze the new and entirely different concept of navigation which it presents. The pilot on instruments is no longer blind; he has at his disposal an electronic “eye”, which regardless of weather, can tell him his exact position.

The procedures to utilize this picture information can best be summarized as “Operation Teamwork”. By means of ordinary radiotelephone equipment, the airport traffic controller to act as temporary navigator. He can tell the pilot exactly where he is; the course to fly to get where he wants to go. When the pilot is on approach, the controller gives him the information needed to maintain the ideal approach and glide path to touchdown. The pilot is also advised of the position and courses of other traffic in the vicinity.

  1. Find in the text English equivalents for the following words and expressions:

определять, в поисках цели, посредством чего-либо, в направлении чего-либо, способный к обнаружению, измеряющее устройство, тело отражающее сигнал, при благоприятных условиях, измеряя угол возвышения, столкнуться с целью, длина импульса, очень короткие импульсы, излучать в пространство, направленная система антенн, собирать, принимать, чувствительный приёмник, переводить информацию, пятна света, инструмент управления движением.

  1. Answer the following questions.

  1. What is radio detection and ranging?

  2. How can the elevation of height of an airborne target be obtained?

  3. What are the requirements for Basic Radar System?

  4. How do ASR and PAR operate?

  5. What device are bursts of energy amplified by?

  6. What does an accurate electronic “stop watch” measure?

  7. What do the spots of light represent?

  8. What does ASR give the airport controller?

  9. How long does the controller have a continuous picture of the traffic, and why?

  10. In what range may the position of a landing be determined?

III. Give Russian equivalents for the following expressions from the text:

in the direction of smth, measuring device, the fluorescent coating, for the pilot`s benefit, to face the target, to translate the information, a high degree of accuracy, to be capable for defecting, the pulse length, spots of light, to utilize the same principles, to pick up, traffic-control instrument, a sensitive receiver, reflecting body, in search of a target, by means of smth, under favorable conditions, by measuring the angel of elevation, directional antenna system, to fire into space, extremely short bursts.

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