1、 MIL - STD - 291C 10 February 1998 SUPERSEDING MIL - STD - 291B 13 December 1967 DEPARTMENT OF DEFENSE INTERFACE STANDARD STANDARD TACTICAL AIR NAVIGATION (TACAN) SIGNAL AMSC N/A FSC 5826 DISTRIBUTION STATEMENT A . Approve d for public release; distribution is unlimited. INCH - POUND Provided by IHS
2、Not for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-291CiiFOREWORD1. This standard is approved for use by all Departments and Agencies of the Department ofDefense.2. Beneficial comments (recommendations, additions, deletions) any any pertinent data whichmay be
3、of use in improving this document should be address to Commander, Naval Air WarfareCenter Aircraft Division, Code 4.1.4.2B120-3, Highway 547, Lakehurst, NJ 08733-5100, usingthe self-addressed Standardization Document Improvement Proposal (DD Form 1426) appearingat the end of this document or by lett
4、er.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-291CiiiCONTENTSPARAGRAPH PAGEFOREWORD . ii1. SCOPE . 11.1 Scope . 12. APPLICABLE DOCUMENTS (Not applicable)3. DEFINITIONS (Not applicable)4. GENERAL REQUIREMENT 14.1 TACAN channels 14.1.1 Num
5、ber of channels 14.1.1.1 Interrogating frequency . 14.1.1.2 Ground reply frequency . 15. DETAILED REQUIREMENTS . 25.1 TACAN surface transponder signal . 25.1.1 Radio frequency (r.f) . 25.1.2 R.F. pulse spectrum 25.1.3 Continuous wave (cw) output . 25.2 Pulse sh ape . 25.2.1 Pulse top . 25.2.2 Pulse
6、rise time . 25.2.3 Pulse fall time . 25.2.4 Pulse duration . 25.3 Pulse droop . 25.4 Pulse coding . 35.5 Main reference pulse group . 35.6 Auxiliary reference pulse group . 35.7 Precedence 35.8 Identification signal . 35.8.1 Equalizing pulse pair . 35.8.2 Identity cycle 35.9 Pulse repetition rate 45
7、.10 Dead time . 45.11 Composite 15 and 135 Hz variable bearing signal 45.11.1 Harmonic content . 55.12 Distance reply signal . 5Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-291CivCONTENTS (Continued)PARAGRAPH PAGE5.12.1 Reply efficiency .
8、55.13 TACAN interrogating signal . 55.13.1 Radio frequency 55.13.2 R.F. pulse spectrum 65.13.3 Cw output . 65.13.4 Pulse shape . 65.13.5 Pulse top . 65.13.6 Pulse rise time . 65.13.7 Pulse fall time . 65.13.8 Pulse duration . 65.14 Pulse coding . 65.15 Pulse repetition rate 65.1.5.1 Pulse repetition
9、 Rate variation . 65.16 Air-to-air (A/A) mode signal . 75.17 A/A system delay time 75.18 Signal characteristics . 76. NOTES6.1 Intended use . 76.2 International standardi zation agreement 76.3 Cross reference . 76.4 Subject term (keyword) listing 86.5 Changes from previous issue . 8TABLEI TACAN Freq
10、uencies . 9FIGUREI Random pulse distribution limits 17Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-291C11. SCOPE1.1 Scope . This standard defines the Standard TACAN Signal. The characteristics andtolerances specified will ensure compatibil
11、ity of all airborne and ground equipment.2. APPLICABLE DOCUMENTS (Not applicable)3. DEFINITIONS (Not applicable)4. GENERAL REQUIREMENTS4.1 TACAN channels . The TACAN system shall operate on the frequencies shown in table I.4.1.1 Number of channels . There shall be provision of 252 channels, 126 “X”
12、channelsnumbered 1X through 126X, and 126 “Y” channels numbered 1Y through 126Y. Each channelshall have an interrogating frequency/pulse spacing and reply frequency/pulse spacing as shown intable I. In addition, there shall be provision for 126 pairs of air-to-air (A/A) mode channels asspecified in
13、5.1 and also in table I.4.1.1.1 Interrogating frequency . The interrogating frequency for the 252 channel TACANsystem shall begin with Channel 1 (X or Y) at 1025 megahertz (MHz) and increase in 1 MHzincrements until Channel 126 (X or Y) at 1150 MHz is reached. The interrogating pulse spacingshall be
14、 12 microseconds (sec) for X channels, 36 sec for Y channels, and 24 sec for Y modeA/A. (See table I) (NOTE: See 3.4 for definition.)4.1.1.2 Ground reply frequency . The ground reply frequency for the 252 channel TACANsystem shall begin at Channel 1X with 962 MHz (which is 63 MHz lower than the inte
15、rrogatingfrequency) and increase in 1 MHz increments until Channel 63X is reached at 1024 MHz.Continuing, Channel 64X will be at ground reply frequency of 1151 MHz (which is 63 MHzhigher than the interrogating frequency), and increase in 1 MHz increments until Channel 126X isreached at 1213 MHz. The
16、 ground reply pulse spacing for X Channels shall be 12 sec. For YChannels, the ground reply frequency shall begin for Channel 1Y with 1088 MHz (which is 63MHz higher than the interrogating frequency) and increase in 1 MHz increments until Channel63Y is reached at 1150 MHz. Continuing, Channel 64Y wi
17、ll be at a ground reply frequency of1025 MHz (which is 63 MHz lower than the interrogating frequency) and increase in 1 MHzincrements until Channel 126Y is reached at 1087 MHz. The ground reply pulse spacing for Ychannels shall be 30 sec. (See table I.)Provided by IHSNot for ResaleNo reproduction or
18、 networking permitted without license from IHS-,-,-MIL-STD-291C25. DETAILED REQUIREMENTS5.1 TACAN surface transponder signal . The standard signal, to be radiated and received bythe transponder of the TACAN system, shall be vertically polarized and the radiated signal shallhave the following charact
19、eristics:5.1.1 Radio frequency (r.f.) . The transmitted frequency shall be maintained within plus orminus 0.002 percent of that specified.5.1.2 R.F. pulse spectrum . The peak effective radiated power contained in each of the two0.5 MHz bands centered on frequencies plus or minus 0.8 MHz above and be
20、low the nominalchannel frequency shall not exceed 100 milliwatts (mw), and the peak effective radiated powercontained in each of the two 0.5 MHz bands centered on frequencies plus or minus 2.0 MHzabove and below the nominal channel frequency shall not exceed 2.0 mw. Each lobe of thespectrum shall be
21、 less than the adjacent lobe nearer the nominal channel frequency.5.1.3 Continuous wave (cw) output . Cw output between pulse pairs shall not exceed 5microwatts (w) with the beacon in normal operational mode. The peak signal amplitude for aperiod of 1 sec between pulses of a pair on X channels and 1
22、9 sec between pulses of a pair andpulses of the main reference group on Y channels shall be at least 20 decibel (db) below the peakpulse amplitude. During the Y channel auxiliary reference burst group, the energy shall be at least20 db below the peak pulse amplitude for at least 4 sec between pulses
23、 of the group.5.2 Pulse shape . The pulse envelope as detected by a linear detector shall have a roundedshape falling within the following limits:5.2.1 Pulse top . The instantaneous amplitude of the pulse shall not, at any instant betweenthe point of the leading edge which is 95 percent of the maxim
24、um voltage amplitude and the pointof the trailing edge which is 95 percent of the maximum amplitude, fall below a line which is 95percent of the maximum voltage amplitude of the pulse and is parallel to the base line.5.2.2 Pulse rise time . The time required for the leading edge of the pulse to rise
25、 from 10 to90 percent of its maximum voltage amplitude shall be 2.0 0.25 sec.5.2.3 Pulse fall time . The time required for the trailing edge of the pulse to fall from 90percent to 10 percent of its maximum voltage amplitude shall be 2.5 0.5 sec.5.2.4 Pulse duration . The pulse duration which is meas
26、ured between the points on theleading and trailing edges of the pulse which are 50 percent of the maximum voltage amplitude ofthe pulse shall be 3.5 0.5 sec.5.3 Pulse droop . Prior to amplitude modulation by the antenna of the composite r.f. pulsetrain, the percentage modulation of the pulse train a
27、t 15 or 135 Hertz (Hz) shall not exceed 0.08Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-291C3percent (see 3.5 and 3.6). This shall be measured with the transponder operating normally andshall include the effects of droop and recovery time
28、 of the main and auxiliary reference groups.5.4 Pulse coding . For X channels, the pulses shall be coded in pairs with a spacing whichshall be 12 0.10 sec as measured at 50 percent voltage amplitude points from the leading edgeof the first pulse to the leading edge of the second pulse. For Y channel
29、s, the ground-to-airfunction spacing shall be 30 0.10 sec as measured at 50 percent voltage amplitude points fromthe leading edge of the first pulse to the leading edge of the second pulse.5.5 Main reference pulse group . The 15 Hz reference bearing group is called the mainreference group: for X cha
30、nnels, it shall consist of a group of 12 pairs of pulses, with the spacingbetween pairs established as 12 0.10 sec; for Y channels, it shall consist of a group of 13 singlepulses spaced 30 0.10 sec. In each case, the repetition rate of the group shall be 15 Hz 0.2percent.5.6 Auxiliary reference puls
31、e group . The 135 Hz reference bearing group is called theauxiliary reference group: for X channels, it shall consist of 6 pairs of pulses, with the spacingbetween pairs established as 24 0.10 sec; for Y channels, it shall consist of a group of 13 singlepulses spaced 15 0.10 sec. In each case, the r
32、epetition rate of the group shall be 135 Hz whichshall be synchronized with the main reference group; however, the auxiliary group which wouldotherwise coincide in time with the main reference group shall be removed so that only the mainreference group appears in this position in the final output si
33、gnal.5.7 Precedence . Random, identity, and distance reply pulses shall not appear during a mainor auxiliary reference group.5.8 Identification signal . The identification signal shall consist of a series of paired pulsesspaced as specified in 3.4, transmitted at a repetition rate of 1350 pulse pair
34、s per second (sec) andsynchronized so that the first pulse of an identity pair shall occur 740 50 sec after the firstpulse of the preceding auxiliary reference group.5.8.1 Equalizing pulse pair . To preserve a constant duty cycle and to minimize bearing errorduring identity signals, an equalizing pa
35、ir of pulses shall be transmitted 100 10 sec after eachidentity pair.5.8.2 Identity cycle . The random and distance reply pulses shall be replaced by the identitypulses at a recurrence rate of once ever 37.5 sec 10 percent. During identity, the beacon codeshall be transmitted as dots and dashes (Mor
36、se Code) of identity pulses; the spaces between dotsand dashes being occupied by distance reply and random pulses. The dots shall be 0.125 sec 10percent; dashes shall be 0.375 sec 10 percent. Maximum message length shall not exceed 5.0seconds.Provided by IHSNot for ResaleNo reproduction or networkin
37、g permitted without license from IHS-,-,-MIL-STD-291C45.9 Pulse repetition rate . The signal shall have randomly distributed pulses which shall bemaintained at a rate of 2700 90 pairs per sec before the reference groups are added; the randompulses shall include any distance replies. The distribution
38、 of the random pulse pairs, for nointerrogating load, shall fall within the limits shown on Figure 1, for a dead time of 60 sec.5.10 Dead time . Dead time is defined as the total time following a decoded pulse pair (froman interrogation or noise) during which there will be no response to subsequent
39、interrogations ornoise. The dead time shall not normally exceed 60 sec and is not usually extended by the echosuppression circuits, but or special cases where the geographical site of the transponder is such asto produce undesirable reflection problems, a longer echo suppression time may be specifie
40、d; thiswill tend to increase the average dead time. In extreme cases, this may require compensatingpulses to maintain azimuth accuracy. The spacing between any two consecutively transmittedrandom pulse pairs that are not replies shall be not less than 60 sec.5.11 Composite 15 and 135 Hz variable bea
41、ring signal . The bearing signal shall be generatedby rotating a directional pattern which produces, at a point in space, a composite amplitudemodulation of the r.f. pulse signals at 15 and 135 Hz. Viewed from above, the direction ofpattern rotation shall be clockwise. For X-mode operation the ampli
42、tude modulation shall besynchronized with the 15 Hz main reference group so that at a point due south of the beacon the10th pulse of the main reference group will coincide with the positive slope point of inflection ofthe 15 Hz component of the bearing signal and at points geographically spaced by a
43、ll multiples of40 degrees from due south, the 12th pulse of each auxiliary reference group shall coincide withthe positive slope point of inflection of the 135 Hz component. For Y-Mode operation thecoincidence points shall be midway between the 6th and 7th pulses of the 15 Hz reference group,and sha
44、ll be at the 12th pulse of the 135 Hz reference group. The main reference group shalloccur when the maximum of the composite signal is directed due east of the transponder. In theabsence of harmonics, the modulation envelope of the detected r.f. pulse signal shall follow thisformula:y = 1.0 Asin (2
45、B ft 2 - () + Bsin (18 B ft - 9 ()Where:(1) y = normalized composite 15- 135 Hz signal amplitude(2) A = represents modulation of 15 Hz component(3) B = represents modulation of 135 Hz component(4) 2 = deviation in electrical degrees from coincidence of the 15 Hz modulation andthe main reference grou
46、p.(5) = deviation in electrical degrees from coincidence of the 135 Hz modulation andthe auxiliary reference group.(6) ( = bearing to the ground or shipboard station from the point of observation.(7) f = pattern rotation frequency in Hz.Provided by IHSNot for ResaleNo reproduction or networking perm
47、itted without license from IHS-,-,-MIL-STD-291C5(8) t = time in seconds from the corrected position of the 10th pulse of the X-modemain reference group or 15 sec after the 6th pulse of the Y-mode mainrefe rence group. t is computed from the average position of the 12th pulse ofeach auxiliary referen
48、ce group.Tolerances:f = 15 Hz 0.2 percentFor angles of elevation between -45 and +45 degrees2 = 0.3 degree maximum = 0.3 degree maximumA = 0.21 0.09B = 0.21 0.09Sum of A and B not greater than 0.55Cross polarization effects up to plus or minus 45 degrees from the vertical and withinelevation angles
49、of -45 to +45 degrees must be limited such that 2 does not exceed 3degrees and does not exceed 1 degree.5.11.1 Harmonic content . At vertical angles from the horizon to 6 degrees above the horizonthe root means square (r.m.s.) sum of the second through the sixth harmonics of the 15 Hzmodulation comp
