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IRIG 106-99 CHAPTER 3 - FREQUENCY DIVISION MULTIPLEXING TELEMETRY STANDARDS 3.1 General 3.2 FM Subcarrier Characteristics 3.3 FM Subcarrier Channel Characteristics 3.4 Tape Speed Control and Flutter Compensation Footnotes FREQUENCY DIVISION MULTIPLEXING TELEMETRY STANDARDS 3.1 General In frequency division multiplexing, each data channel makes use of a separate subcarrier which occupies a defined position and bandwidth in the modulation baseband of the RF carrier. Two types of frequency modulation (FM) subcarrier formats may be used. The data bandwidth of one format type is proportional to the subcarrier center frequency, while the data bandwidth of the other type is constant, regardless of subcarrier frequency. 3.2 FM Subcarrier Characteristics In these systems, one or more subcarrier signals, each at a different frequency, are employed to frequency modulate (FM) or phase modulate (PM) a transmitter in accordance with the RF conditions specified in chapter 2. The following subparagraphs set forth the standards for utilization of FM frequency division multiplexing. 3.2.1 Each of the subcarriers conveys measurement data in FM form. The number of data channels may be increased by modulating one or more of the subcarriers with a time-division multiplex format such as pulse-code modulation (PCM). 3.2.2 The selecting and grouping of subcarrier channels depend upon the data bandwidth requirements of the application at hand and upon the necessity to ensure adequate guard bands between channels. Combinations of both proportional-bandwidth channels and constant-bandwidth channels may be used. 3.3 FM Subcarrier Channel Characteristics 3.3.1 Proportional-Bandwidth FM Subcarrier Channel Characteristics 3.3.2 Constant-Bandwidth FM Subcarrier Channel Characteristics The following subparagraphs describe the characteristics of proportional-bandwidth and constant-bandwidth FM subcarrier channels. 3.3.1 Proportional-Bandwidth FM Subcarrier Channel Characteristics. Table 3-1 lists the standard proportional-bandwidth FM subcarrier channels. The channels identified with letters permit ±15 or ±30 percent subcarrier deviation rather than ±7.5 percent deviation but use the same frequencies as the 12 highest channels. The channels shall be used within the limits of maximum subcarrier deviation. See appendix B for expected performance tradeoffs at selected combinations of deviation and modulating frequency. |
±7.5% CHANNELS |
| 1 2 3 |
400 560 730 |
370 518 675 |
430 602 785 |
6 8 11 |
58 44 32 |
30 42 55 |
11.7 8.33 6.40 |
| 4 5 6 |
960 1300 1700 |
888 1202 1572 |
1032 1398 1828 |
14 20 25 |
25 18 14 |
72 98 128 |
4.86 3.60 2.74 |
| 7 8 9 |
2300 3000 3900 |
2127 2775 3607 |
2473 3225 4193 |
35 45 59 |
10 7.8 6.0 |
173 225 293 |
2.03 1.56 1.20 |
| 10 11 12 |
5400 7350 10 500 |
4995 6799 9712 |
5805 7901 11 288 |
81 110 160 |
4.3 3.2 2.2 |
405 551 788 |
.864 .635 .444 |
| 13 14 15 |
14 500 22 000 30 000 |
13 412 20 350 27 750 |
15 588 23 650 32 250 |
220 330 450 |
1.6 1.1 .78 |
1088 1650 2250 |
.322 .212 .156 |
| 16 17 18 |
40 000 52 500 70 000 |
37 000 48 562 64 750 |
43 000 56 438 75 250 |
600 788 1050 |
.58 .44 .33 |
3000 3938 5250 |
.117 .089 .06 |
| 19 20 21 |
93 000 124 000 165 000 |
86 025 114 700 152 625 |
99 975 133 300 177 375 |
1395 1860 2475 |
.25 .19 .14 |
6975 9300 12 375 |
.050 .038 .029 |
| 22 23 24 25 |
225 000 300 000 400 000 560 000 |
208 125 277 500 370 000 518 000 |
241 875 322 500 430 000 602 000 |
3375 4500 6000 8400 |
.10 .08 .06 .04 |
16 875 22 500 30 000 42 000 |
.021 .016 .012 .008 |
SUBCARRIER CHANNELS ±15% CHANNELS |
| A B C |
22 000 30 000 40 000 |
18 700 25 500 34 000 |
25 300 34 500 46 000 |
660 900 1200 |
.53 .39 .29 |
3300 4500 6000 |
.106 .078 .058 |
| D E F |
52 500 70 000 93 000 |
44 625 59 500 79 050 |
60 375 80 500 106 950 |
1575 2100 2790 |
.22 .17 .13 |
7875 10 500 13 950 |
.044 .033 .025 |
| G H I |
124 000 165 000 225 000 |
105 400 140 250 191 250 |
142 600 189 750 258 750 |
3720 4950 6750 |
.09 .07 .05 |
18 600 24 750 33 750 |
.018 .014 .010 |
| J K L |
300 000 400 000 560 000 |
255 000 340 000 476 000 |
345 000 460 000 644 000 |
9000 12 000 16 800 |
.04 .03 .02 |
45 000 60 000 84 000 |
.008 .006 .004 |
SUBCARRIER CHANNELS ±30% CHANNELS |
| AA BB CC |
22 000 30 000 40 000 |
15 400 21 000 28 000 |
28 600 39 000 52 000 |
1320 1800 2400 |
.265 .194 .146 |
6600 9000 12 000 |
.053 .038 .029 |
| DD EE FF |
52 500 70 000 93 000 |
36 750 49 000 65 100 |
68 250 91 000 120 900 |
3150 4200 5580 |
.111 .083 .063 |
15 750 21 000 27 900 |
.022 .016 .012 |
| GG HH II |
124 000 165 000 225 000 |
86 800 115 500 157 500 |
161 200 214 500 292 500 |
7440 9900 13 500 |
.047 .035 .026 |
37 000 49 500 67 500 |
.009 .007 .005 |
| JJ KK LL |
300 000 400 000 560 000 |
210 000 280 000 392 000 |
390 000 520 000 728 000 |
18 000 24 000 33 600 |
.019 .015 .010 |
90 000 120 000 168 000 |
.004 .003 .002 |
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Round off to nearest Hz. The indicated maximum data frequency response and minimum rise time is based on the maximum theoretical response that can be obtained in a bandwidth between the upper and lower frequency limits specified for the channels. See appendix B, paragraph 3.0 for determining possible accuracy versus response tradeoffs. Channels A through L may be used by omitting adjacent lettered and numbered channels. Channels 13 and A may be used together with some increase in adjacent channel interference. Channels AA through LL may be used by omitting every four adjacent double lettered and lettered channels and every three adjacent numbered channels. Channels AA through LL may be used by omitting every three adjacent double lettered and lettered channels and every two adjacent numbered channels with some increase in adjacent channel interference. |
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3.3.2 Constant-Bandwidth FM Subcarrier
Channel Characteristics. Table 3-2 lists the standard
constant-bandwidth FM subcarrier channels. The letters A, B, C, D, E, F, G,
and H identify the channels for use with maximum subcarrier deviations of ±2,
±4, ±8, ±16, ±32, ±64, ±128, and ±256 kHz, along with maximum frequency
responses of 2, 4, 8, 16, 32, 64, 128, and 256 kHz. The channels shall be
used within the limits of maximum subcarrier deviation. See
appendix B for
expected performance tradeoffs at selected combinations of deviation and
modulating frequencies. |
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3.4 Tape Speed Control and Flutter Compensation Tape speed control and flutter compensation for FM/FM formats may be accomplished as indicated in subparagraph 6.8.4, chapter 6. The standard reference frequency used shall be in accordance with the criteria in table 3-3 when the reference signal is mixed with data. |
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Speed and Flutter Compensation Reference Frequency (kHz ±0.01%) 960 12 480 1 240 1 200 100 50 25 12.5 6.25 3.125 |
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If the reference signal is recorded on a separate tape track, any of the listed
reference frequencies may be used provided the requirements for compensation
rate of change are satisfied. If the reference signal is mixed with the data signal, consideration must be given to possible problems with intermodulation sum and difference frequencies. Also, sufficient guard band must be allowed between the reference frequency and any adjacent data subcarrier. Chapter 3 Footnotes 12. These frequencies are for flutter compensation only and not for capstan servo speed control. In addition, the 240 kHz reference signal may be used as a detranslation frequency in a constant-bandwidth format. |