A sinusoidal time-varying electrical signal. AC Signal amplitude DC Offset AC Signal frequency AC Signal phase angle A continuous sinusoidal wave (carrier) whose amplitude is varied as a function of the instantaneous value of a second wave (modulating). Carrier amplitude Carrier frequency Modulation frequency Depth of modulation An unvarying electrical signal with an optional ac component.. DC Level AC Component amplitude AC Component frequency AC Component phase angle A parallel digital source that creates a digital logic signal in which the physical values for logic one, logic zero and high impedance data values are determined by the logic threshold values specified. Data Value Clock period Logic One level Logic Zero level A serial digital source that creates a digital logic signal in which the physical values for logic one, logic zero and high impedance data values are determined by the logic threshold values specified. Data Value Clock period. Zero denotes infinite time for static digital data. Logic One level Logic Zero level A radio aid to air navigation that provides distance information by measuring the time of transmission from an interrogator to a transponder and return. The DME system is composed of a transponder in the ground based unit and an interrogator in the airborne unit. The interrogator on the aircraft emits a pulse signal that once received by the DME transponder on the ground starts a response sequence which sends a return pulse signal on a different (paired) channel to the aircraft. The aircraft equipment receives the response from the ground station, computes the elapsed time between interrogation and response then subtracts 50 us (to cover ground station processing time) and divides the result by 2. This result is then displayed on the DME indicator. The DME operates on the UHF band in the range 962 MHz to 1213 MHz with a step of 1 MHz. The frequencies used by the interrogator are between 1025 MHz and 1150 MHz and the transponder on the ground replies using two set frequencies, the first from 962 MHz to 1024 MHz and the second from 1151 MHz to 1213 MHz. The number of available frequencies is 252 giving 126 available channels. Each channel has 2 frequencies one for interrogation and the other for the response from the ground station. On each pair of frequencies the difference between the interrogator frequency and the answer frequency is always of 63 MHz. For the channels between 1 and 63, the interrogation frequency is 63 MHz higher than the response frequency and for channels from 63 to 126 the response frequency is 63 MHz higher than the interrogator frequency. Carrier Amplitude Interrogator Frequency Interrogation Rate A radio aid to air navigation that provides distance information by measuring the time of transmission from an interrogator to a transponder and return. The DME system is composed of a transponder in the ground based unit and an interrogator in the airborne unit. The interrogator on the aircraft emits a pulse signal that once received by the DME transponder on the ground starts a response sequence which sends a return pulse signal on a different (paired) channel to the aircraft. The aircraft equipment receives the answer from the ground station, computes the elapsed time between interrogation and response. A period of 50 µs (to cover ground station processing time) is then subtracted and the result is divided by 2. This result is then displayed on the DME indicator. The DME operates on the UHF band in the range 962 MHz to 1213 MHz with a step of 1 MHz. The frequencies used by the interrogator are between 1025 MHz and 1150 MHz and the transponder on the ground replies using two set frequencies, the first from 962 MHz to 1024 MHz and the second from 1151 MHz to 1213 MHz. The number of available frequencies is 252 so 126 channels are be available. Each channel has 2 frequencies one for interrogation and the other for the response from the ground station. On each pair of frequencies the difference between the interrogator frequency and the answer frequency is always of 63 MHz. For the channels between 1 and 63, the interrogation frequency is 63 MHz higher than the response frequency and for channels from 63 to 126 the answer frequency is 63 MHz higher than the interrogator frequency. Transponder Frequency Carrier Amplitude Slant Range Range Rate Rate of Change of Range Rate A continuous sinusoidal wave (carrier) generated when the frequency of one wave is varied in accordance with the amplitude of another wave(modulating). Carrier amplitude Carrier frequency Frequency Deviation Modulation frequency The glide slope is the vertical guidance portion of an ILS. At present, 40 glide slope channels exist with 150 KHz-channel separation in the frequency range from 328.6 - 335.4 MHz. The carrier is amplitude modulated at 90 Hz and 150 Hz in a spatial pattern with the 90 Hz modulation predominant when the airplane is above the glide path and the 150 Hz modulation predominant if the airplane is below the glide path. This is achieved by transmitting 2 beams with equal offset about the correct glide slope angle, the upper beam being modulated to a depth of 40% with a 90 Hz tone and the lower beam to 40% with a 150 Hz tone, the carrier of both beams is phase locked such that any receiver will treat them as a single carrier signal with 2 modulating tones. If the aircraft is positioned off the glide slope, the ILS receiver will detect one signal as stronger than the other resulting in the demodulated amplitude (or apparent depth of modulation) of one tone being greater than that of the other. If the receiver is exactly on the glide slope, it will receive an RF carrier where the 90 Hz and 150 Hz modulation depths appear exactly the same. The greater the deviation from the glide slope the greater will be the difference in amplitude of the tones. Carrier amplitude Frequency 150 Hz attenuation depth 90 Hz attenuation depth The localizer is the lateral guidance portion of the ILS giving azimuth guidance with reference to the runway centre line. It operates using the same principles as the Glide Slope but with forty channels in the VHF band 108.0 MHz to 112.0 MHz, each localizer channel being paired with a glide slope channel. The carrier is modulated with a 90 Hz and 150 Hz tone in a spatial pattern that makes the 90 Hz tone predominant when the aircraft is to the left of the course and the 150 Hz tone predominant when the aircraft is to the right of the course. The localizer carrier contains a Morse coded signal identifying the runway and approach direction and also may carry a ground-to-air communication channel. Carrier Amplitude Carrier frequency 150Hz attenuation depth 90Hz attenuation depth Two or three marker beacons operate at 75 MHz to give range with reference to the touch-down point. The outer marker is modulated with a 400 Hz tone to a depth of 95%. It is located 4 - 7 miles from the end of the runway where the glide slope intersects the procedure turn altitude ± 50 ft vertically. It radiates a fan shaped pattern vertically and normal to the localizer and activates a marker receiver when the aircraft passes through. The middle marker is a second fan shaped marker similar to the outer marker. It is located approximately 3500 ft from the ILS approach end of the runway and modulated at 1300 Hz. The inner marker, when used for category II approaches, intercepts the glide path at about the 100 ft height to mark the over-shoot decision point (if the runway is still not visible). The marker is recognized by its 3000Hz modulation. Category II approaches allow operation down to 30 m (or 100ft) and 400 m (or 1300 ft) visibility. Marker Frequency Carrier Frequency A continuous sinusoidal wave (carrier) whose phase is varied in accordance with the amplitude of another wave. Carrier amplitude Carrier frequency Phase Deviation Modulation frequency Modulation amplitude A signal characterized by short duration periods of (sinusoidal) ac electrical potential. AC Signal amplitude AC Signal frequency DC offset Initial delay Pulse width Pulse repetition frequency Number of pulses A signal, characterized by a train of pulses of sinusoidal electrical ac activity with different durations and amplitudes. AC amplitude AC frequency DC offset Pulse train A signal characterized by a train of pulses of electrical dc activity with different durations and amplitudes with an optional ac component. DC level AC component amplitude AC component frequency Delay before first pulse Pulse width Pulse repetition frequency Number of pulses A signal, characterized by a train of different, short duration periods of DC electrical activity. DC level Pulse train AC Component amplitude AC Component frequency The Radar_RX_Signal provides an appropriate delayed signal response to an input Radar signal. Atten Range of simulated target Rate of change of rate change Rate of change of target range Proportion of Tx pulses returned A pulsed ac signal used as a reference for received radar signals (Radar_RX_Signal). Tx signal amplitude Tx signal frequency Initial delay Pulse duration Pulse repetition frequency Number of pulses A periodic wave whose instantaneous value varies alternately and linearly between two specified values (initial and alternate). The interval required to transition from the initial value to the alternate value shall not be equal to the interval to transition from the alternate value to the initial value. Ramp signal amplitude DC offset Ramp signal period Ramp signal time to rise Transient disturbances occurring unpredictably, except in a statistical sense. Noise signal amplitude Pseudo random noise frequency Pseudo random noise seed Two ac sine wave voltages whose relationships of amplitude represent the rotation of a shaft position of an electro-mechanical transducer, Shaft angle Reference amplitude Reference frequency Zero index Shaft angle rate Transformer Ratio A serial databus signal that transmits and receives strings of characters and operates according to the specification TIA-232. Data Word Baud Rate Data Bits Parity Stop Bits Flow Control A periodic wave, that alternately assumes one of two fixed values of amplitude for equal lengths of time. Square wave amplitude Square wave period DC offset Secondary Surveillance Radar (SSR) provides information to supplement that obtained from a primary radar. ATC for civilian air traffic control, and Identification, IFF for military use, governing documents for ATC are ARINC Specification 572 and ARINC Specification 711 and for IFF STANAG 5017. An aircraft on-board transponder will sense an interrogation from a ground (or airborne) station on a specific frequency (1030 MHz) and responds with coded signals on another frequency (1090 MHz). P1 Amplitude Interrogation mode P3 Start Time P3 level SLS Deviation SLS Level The transponder response to a valid SSR interrogation. It consists of an encoded pulse train. Each pulse train consists of a number of data pulses, the number and position of these data pulses (after the start pulse) being determined by the mode selected. There are 16 pulse positions in the pulse train, however the code or (height) information carried by the response will determine which pulses are present. Carrier Amplitude P3 pulse start time SSR Response Pulse Train A change of dc electrical potential from one level to another, either positive or negative. Step size DC offset Step time An amplitude modulated signal in which the carrier is suppressed. Carrier amplitude Carrier frequency Modulation frequency Depth of modulation Three ac sinusoid voltages whose relationships of amplitude represent the rotational shaft position of an electro-mechanical transducer. Shaft angle Reference amplitude Reference frequency Zero index Shaft angle rate Transformer Ratio TACAN (tactical air navigation) is a complete UHF polar coordinate navigation system using pulse techniques. The function operates identically as a DME and the bearing function is derived by rotating the ground transponder antenna so as to obtain a rotating multi-lobe pattern for coarse and fine bearing information, as defined in MIL-STD-291B The model defines a subset of the TACAN X signal concerned with bearing, rather than the complete signal as test requirements dealing with TACAN distance can be refined using the DME model. The transponder emits RF pulses that are amplitude modulated to provide bearing information, The amplitude modulation is produced by rotating a parasitic reflector array about the antenna radiating element. The array consists of one 15 Hz and nine 135 Hz reflectors. As the pattern from the 15 Hz reflector passes through the magnetic east azimuth, a main reference burst (MRB) is transmitted. As the pattern from the 135 Hz reflectors passes through east, an auxiliary reference burst (ARB) is transmitted, except when the pattern is coincident with the 15 Hz pattern. This produces a total of one MRB and eight ARB bursts per antenna rotation. The airborne receiving equipment determines the aircraft bearing from the ground station by measuring elapsed time, first, from the MRB to the 0 degree phase of the 15 Hz component and second, from the ARB to 0 degree of the 135 Hz component. The TACAN beacon also generates a 2 or 3 letter Morse identification signal every 37.5 seconds Transponder Frequency Modulation Index Magnetic Bearing er Amplitude A periodic wave whose instantaneous value varies alternately and linearly between two specified values (initial and alternate). The interval required to transition from the initial value to the alternate value shall be equal to the interval to transition from the alternate value to the initial value. Triangular wave signal amplitude Trianglar wave signal period DC offset VHF Omnidirectional Range (VOR) is a system combining ground based and airborne equipment to provide bearing to or from a ground station, as defined in ARINC Specification 579. The VOR radiates a radio frequency carrier in the band 108.0-117.975 MHz, with which are associated two separate 30Hz modulations. The phase of one of these modulations is independent of the point of observation (reference phase). The phase of the other modulation (variable phase) is such that, at a point of observation, it differs from the reference phase by an angle equal to the bearing of the point of observation with respect to the VOR. The two separate modulations consist of the following: A sub-carrier of 9960 Hz, frequency modulated at 30 Hz, modulating the carrier to a nominal depth of 30%. This 30 Hz component is fixed independent of the azimuth and is termed the Reference Phase. A 30 Hz component, modulating the carrier to a nominal depth of 30%. This 30 Hz component is caused by a rotating antenna producing a change in phase with azimuth and is termed the Variable Phase. Carrier amplitude Carrier frequency Radial bearing