56:
31:
2764:
713:
it is usual to define the cutoff frequency as the point after the last peak in the frequency response at which the level has fallen to the design value of the passband ripple. The amount of ripple in this class of filter can be set by the designer to any desired value, hence the ratio used could be
1943:
where subscript T indicates a 2-dimensional transverse
Laplacian. The final step depends on the geometry of the waveguide. The easiest geometry to solve is the rectangular waveguide. In that case, the remainder of the Laplacian can be evaluated to its characteristic equation by considering
169:
of the nominal passband value). Alternatively, a stopband corner frequency may be specified as a point where a transition band and a stopband meet: a frequency for which the attenuation is larger than the required stopband attenuation, which for example may be 30 dB or 100 dB.
624:
1667:
here refers to whichever field (the electric field or the magnetic field) has no vector component in the longitudinal direction - the "transverse" field. It is a property of all the eigenmodes of the electromagnetic waveguide that at least one of the two fields is transverse. The
506:
2413:
1454:
907:
2571:
1941:
2079:
1645:
513:
2768:
1790:
2174:
1155:
794:
equal to zero and solving for the frequency. Thus, any exciting frequency lower than the cutoff frequency will attenuate, rather than propagate. The following derivation assumes lossless walls. The value of c, the
391:
1315:
2290:
1342:
671:
2573:
The wave equations are also valid below the cutoff frequency, where the longitudinal wave number is imaginary. In this case, the field decays exponentially along the waveguide axis and the wave is thus
1551:
809:
2476:
359:
263:
746:, the frequency above which a radio wave fails to reflect off the ionosphere at the incidence angle required for transmission between two specified points by reflection from the layer.
2277:
2230:
1826:
1947:
2444:
1556:
1202:
1075:
1011:
939:
1238:
84:
2471:
1817:
1665:
1043:
1682:
2084:
1175:
1091:
979:
959:
1254:
278:
631:
2176:
The transverse wavenumbers can be specified from the standing wave boundary conditions for a rectangular geometry cross-section with dimensions
1463:
1088:) in a waveguide of circular cross-section (the transverse-magnetic mode with no angular dependence and lowest radial dependence) is given by
2691:
1319:
However, the dominant mode cutoff frequency can be reduced by the introduction of baffle inside the circular cross-section waveguide. For a
619:{\displaystyle \left|H(j\omega _{\mathrm {c} })\right|={\frac {1}{\sqrt {2}}}={\sqrt {\frac {1}{1+\alpha ^{2}\omega _{\mathrm {c} }^{2}}}}.}
1324:
2446:
is the critical frequency between propagation and attenuation, which corresponds to the frequency at which the longitudinal wavenumber
779:
2645:
501:{\displaystyle \left|H(j\omega )\right|=\left|{\frac {1}{1+\alpha j\omega }}\right|={\sqrt {\frac {1}{1+\alpha ^{2}\omega ^{2}}}}.}
308:
2779:
2408:{\displaystyle {\frac {\omega ^{2}}{c^{2}}}=\left({\frac {n\pi }{a}}\right)^{2}+\left({\frac {m\pi }{b}}\right)^{2}+k_{z}^{2},}
2234:
2187:
2773:
1449:{\displaystyle \left(\nabla ^{2}-{\frac {1}{c^{2}}}{\frac {\partial ^{2}}{\partial {t}^{2}}}\right)\psi (\mathbf {r} ,t)=0,}
787:
755:
2587:
126:
1320:
224:
2602:
902:{\displaystyle \omega _{c}=c{\sqrt {\left({\frac {m\pi }{a}}\right)^{2}+\left({\frac {n\pi }{b}}\right)^{2}}},}
743:
221:
point since a fall of 3 dB corresponds approximately to half power. As a voltage ratio this is a fall to
2566:{\displaystyle \omega _{c}=c{\sqrt {\left({\frac {n\pi }{a}}\right)^{2}+\left({\frac {m\pi }{b}}\right)^{2}}}}
362:
734:
are transmitted at an angle into the sky and reflected back to Earth by layers of charged particles in the
2833:
99:
265:
of the passband voltage. Other ratios besides the 3 dB point may also be relevant, for example see
130:
709:
Sometimes other ratios are more convenient than the 3 dB point. For instance, in the case of the
2805:
Calculation of the center frequency with geometric mean and comparison to the arithmetic mean solution
2287:
are the two integers representing a specific eigenmode. Performing the final substitution, we obtain
2416:
723:
269:
below. Far from the cutoff frequency in the transition band, the rate of increase of attenuation (
1936:{\displaystyle \left(\nabla _{T}^{2}-k_{z}^{2}+{\frac {\omega ^{2}}{c^{2}}}\right)\psi (x,y,z)=0,}
217:. Most frequently this proportion is one half the passband power, also referred to as the 3
2744:
2686:. Institution of Electrical Engineers. London: Institution of Electrical Engineers. p. 214.
2422:
1457:
783:
775:
282:
202:
115:
63:
1180:
1048:
984:
912:
2736:
2697:
2687:
2641:
1336:
1207:
688:
298:
210:
2637:
2630:
69:
2728:
2592:
710:
162:
2809:
2717:"PEC-PMC Baffle Inside Circular Cross Section Waveguide for Reduction of Cut-Off Frequency"
2449:
1795:
1650:
1016:
2575:
1241:
302:
178:
158:
35:
2074:{\displaystyle \psi (x,y,z,t)=\psi _{0}e^{i\left(\omega t-k_{z}z-k_{x}x-k_{y}y\right)}.}
2804:
1160:
964:
944:
800:
796:
698:
206:
2827:
2608:
2597:
771:
1640:{\displaystyle \left(\nabla ^{2}+{\frac {\omega ^{2}}{c^{2}}}\right)\psi (x,y,z)=0.}
55:
2818:
2783:
2748:
759:
17:
2789:
791:
194:
119:
2716:
66:
plot) of any first-order low-pass filter with a normalized cutoff frequency at
2732:
1820:
767:
735:
731:
274:
87:
2740:
2701:
165:(a frequency for which the output of the circuit is approximately โ3.01
2081:
Thus for the rectangular guide the
Laplacian is evaluated, and we arrive at
1676:
198:
174:
146:
59:
1785:{\displaystyle \psi (x,y,z,t)=\psi (x,y)e^{i\left(\omega t-k_{z}z\right)},}
2681:
2169:{\displaystyle {\frac {\omega ^{2}}{c^{2}}}=k_{x}^{2}+k_{y}^{2}+k_{z}^{2}}
1150:{\displaystyle \omega _{c}=c{\frac {\chi _{01}}{r}}=c{\frac {2.4048}{r}},}
1310:{\displaystyle \omega _{c}=c{\frac {\chi _{11}}{r}}=c{\frac {1.8412}{r}}}
270:
214:
154:
150:
142:
138:
2668:
Microwave
Filters, Impedance-Matching Networks, and Coupling Structures
727:
680:
218:
166:
157:. It is sometimes taken to be the point in the filter response where a
134:
95:
30:
2819:
Mathematical definition of and information about the Bessel functions
286:
1335:
The starting point is the wave equation (which is derived from the
1679:
can further be reduced by considering only functions of the form
758:
is the lowest frequency for which a mode will propagate in it. In
54:
29:
149:
characteristic โ a frequency characterizing a boundary between a
118:
at which energy flowing through the system begins to be reduced (
666:{\displaystyle \omega _{\mathrm {c} }={\frac {1}{\alpha }}.}
181:, the cutoff frequencies correspond to the lower and upper
1546:{\displaystyle \psi (x,y,z,t)=\psi (x,y,z)e^{i\omega t}.}
941:
are the mode numbers for the rectangle's sides of length
1672:
axis is defined to be along the axis of the waveguide.
1323:, the cutoff wavelength is the wavelength at which the
1553:
Substituting and evaluating the time derivative gives
227:
2715:
Modi, Anuj Y.; Balanis, Constantine A. (2016-03-01).
2479:
2452:
2425:
2293:
2237:
2190:
2087:
1950:
1829:
1798:
1685:
1653:
1559:
1466:
1345:
1257:
1210:
1183:
1163:
1094:
1051:
1019:
987:
967:
947:
915:
812:
806:
For a rectangular waveguide, the cutoff frequency is
786:
for electromagnetic waves, which is derived from the
634:
516:
394:
311:
213:
has fallen to a given proportion of the power in the
72:
2419:in the rectangular waveguide. The cutoff frequency
803:of light in whatever material fills the waveguide.
2629:
2565:
2465:
2438:
2407:
2271:
2224:
2168:
2073:
1935:
1811:
1784:
1659:
1639:
1545:
1448:
1309:
1232:
1196:
1169:
1149:
1069:
1037:
1005:
973:
953:
933:
901:
665:
618:
500:
353:
257:
201:either above or below which the power output of a
78:
161:and passband meet, for example, as defined by a
2721:IEEE Microwave and Wireless Components Letters
197:, cutoff frequency or corner frequency is the
354:{\displaystyle H(s)={\frac {1}{1+\alpha s}},}
8:
1460:by considering only functions of the form
258:{\textstyle {\sqrt {1/2}}\ \approx \ 0.707}
133:, cutoff frequency applies to an edge in a
122:or reflected) rather than passing through.
2555:
2536:
2522:
2503:
2496:
2484:
2478:
2457:
2451:
2430:
2424:
2396:
2391:
2378:
2359:
2345:
2326:
2310:
2300:
2294:
2292:
2272:{\displaystyle k_{y}={\frac {m\pi }{b}},}
2251:
2242:
2236:
2225:{\displaystyle k_{x}={\frac {n\pi }{a}},}
2204:
2195:
2189:
2160:
2155:
2142:
2137:
2124:
2119:
2104:
2094:
2088:
2086:
2052:
2036:
2020:
1998:
1988:
1949:
1887:
1877:
1871:
1862:
1857:
1844:
1839:
1828:
1803:
1797:
1763:
1741:
1684:
1652:
1594:
1584:
1578:
1569:
1558:
1528:
1465:
1423:
1403:
1398:
1387:
1381:
1373:
1364:
1355:
1344:
1297:
1280:
1274:
1262:
1256:
1215:
1209:
1188:
1182:
1162:
1134:
1117:
1111:
1099:
1093:
1050:
1018:
986:
966:
946:
914:
888:
869:
855:
836:
829:
817:
811:
778:. The cutoff frequency is found with the
650:
640:
639:
633:
603:
597:
596:
586:
569:
554:
536:
535:
515:
485:
475:
458:
427:
393:
375:. The magnitude of this function in the
327:
310:
281:network, the roll-off is โ20 dB per
233:
228:
226:
71:
628:Hence, the cutoff frequency is given by
125:Typically in electronic systems such as
2620:
1084:mode (next higher from dominant mode TE
2683:Theory and design of microwave filters
730:communication is a technique in which
266:
38:with lower 3 dB cutoff frequency
1675:The "longitudinal" derivative in the
1177:is the radius of the waveguide, and
293:Single-pole transfer function example
45:and upper 3 dB cutoff frequency
7:
1045:is not allowed), while for TM modes
762:, it is more common to consider the
1836:
1566:
1394:
1384:
1352:
641:
598:
537:
25:
1327:is approximately equal to 2.405.
273:) with logarithm of frequency is
34:Magnitude transfer function of a
2810:Conversion of cutoff frequency f
2767: This article incorporates
2762:
1424:
2780:General Services Administration
2628:Van Valkenburg, M. E. (1974).
1978:
1954:
1921:
1903:
1734:
1722:
1713:
1689:
1628:
1610:
1521:
1503:
1494:
1470:
1434:
1420:
1244:of the first kind of order 1.
1227:
1221:
1080:The cutoff frequency of the TM
543:
525:
412:
403:
321:
315:
285:(approximately โ6 dB per
1:
2670:, pp.85-86, McGraw-Hill 1964.
1251:cutoff frequency is given by
788:electromagnetic wave equation
738:. In this context, the term
981:respectively. For TE modes,
799:, should be taken to be the
790:by setting the longitudinal
114:is a boundary in a system's
2439:{\displaystyle \omega _{c}}
754:The cutoff frequency of an
27:Frequency response boundary
2850:
2588:Full width at half maximum
1197:{\displaystyle \chi _{01}}
770:that will propagate in an
2733:10.1109/LMWC.2016.2524529
2636:(3rd ed.). pp.
1321:single-mode optical fiber
1070:{\displaystyle m,n\geq 1}
1006:{\displaystyle m,n\geq 0}
934:{\displaystyle m,n\geq 0}
756:electromagnetic waveguide
2603:Spatial cutoff frequency
2473:is zero. It is given by
1233:{\displaystyle J_{0}(r)}
744:maximum usable frequency
267:ยง Chebyshev filters
1944:solutions of the form
780:characteristic equation
79:{\displaystyle \omega }
2775:Federal Standard 1037C
2769:public domain material
2680:Hunter, I. C. (2001).
2666:Mathaei, Young, Jones
2567:
2467:
2440:
2409:
2273:
2226:
2170:
2075:
1937:
1813:
1786:
1661:
1641:
1547:
1450:
1311:
1234:
1198:
1171:
1151:
1071:
1039:
1007:
975:
955:
935:
903:
667:
620:
502:
355:
277:to a constant. For a
259:
131:communication channels
100:electrical engineering
91:
80:
52:
2788: (in support of
2568:
2468:
2466:{\displaystyle k_{z}}
2441:
2410:
2274:
2227:
2171:
2076:
1938:
1814:
1812:{\displaystyle k_{z}}
1787:
1662:
1660:{\displaystyle \psi }
1642:
1548:
1451:
1331:Mathematical analysis
1312:
1235:
1204:is the first root of
1199:
1172:
1152:
1072:
1040:
1038:{\displaystyle m=n=0}
1008:
976:
956:
936:
904:
668:
621:
503:
356:
260:
81:
58:
33:
2605:(in optical systems)
2477:
2450:
2423:
2291:
2235:
2188:
2085:
1948:
1827:
1819:is the longitudinal
1796:
1683:
1651:
1557:
1464:
1343:
1325:normalized frequency
1255:
1247:The dominant mode TE
1208:
1181:
1161:
1092:
1049:
1017:
985:
965:
945:
913:
810:
718:Radio communications
632:
514:
392:
309:
225:
70:
2814:and time constant ฯ
2417:dispersion relation
2401:
2165:
2147:
2129:
1867:
1849:
724:radio communication
608:
2563:
2463:
2436:
2405:
2387:
2269:
2222:
2166:
2151:
2133:
2115:
2071:
1933:
1853:
1835:
1809:
1782:
1657:
1637:
1543:
1458:Helmholtz equation
1446:
1307:
1230:
1194:
1167:
1147:
1067:
1035:
1003:
971:
951:
931:
899:
784:Helmholtz equation
663:
616:
592:
498:
351:
255:
183:cutoff wavelengths
116:frequency response
92:
76:
64:frequency response
53:
2693:978-0-86341-253-0
2561:
2549:
2516:
2372:
2339:
2316:
2264:
2217:
2110:
1893:
1600:
1410:
1379:
1337:Maxwell equations
1305:
1289:
1170:{\displaystyle r}
1142:
1126:
974:{\displaystyle b}
954:{\displaystyle a}
894:
882:
849:
764:cutoff wavelength
705:Chebyshev filters
689:angular frequency
658:
611:
610:
564:
563:
493:
492:
449:
346:
301:for the simplest
299:transfer function
251:
245:
241:
211:electronic filter
173:In the case of a
18:Cutoff wavelength
16:(Redirected from
2841:
2793:
2787:
2782:. Archived from
2766:
2765:
2753:
2752:
2712:
2706:
2705:
2677:
2671:
2664:
2658:
2657:
2655:
2654:
2635:
2632:Network Analysis
2625:
2593:High-pass filter
2572:
2570:
2569:
2564:
2562:
2560:
2559:
2554:
2550:
2545:
2537:
2527:
2526:
2521:
2517:
2512:
2504:
2497:
2489:
2488:
2472:
2470:
2469:
2464:
2462:
2461:
2445:
2443:
2442:
2437:
2435:
2434:
2414:
2412:
2411:
2406:
2400:
2395:
2383:
2382:
2377:
2373:
2368:
2360:
2350:
2349:
2344:
2340:
2335:
2327:
2317:
2315:
2314:
2305:
2304:
2295:
2286:
2282:
2278:
2276:
2275:
2270:
2265:
2260:
2252:
2247:
2246:
2231:
2229:
2228:
2223:
2218:
2213:
2205:
2200:
2199:
2183:
2179:
2175:
2173:
2172:
2167:
2164:
2159:
2146:
2141:
2128:
2123:
2111:
2109:
2108:
2099:
2098:
2089:
2080:
2078:
2077:
2072:
2067:
2066:
2065:
2061:
2057:
2056:
2041:
2040:
2025:
2024:
1993:
1992:
1942:
1940:
1939:
1934:
1899:
1895:
1894:
1892:
1891:
1882:
1881:
1872:
1866:
1861:
1848:
1843:
1818:
1816:
1815:
1810:
1808:
1807:
1791:
1789:
1788:
1783:
1778:
1777:
1776:
1772:
1768:
1767:
1666:
1664:
1663:
1658:
1646:
1644:
1643:
1638:
1606:
1602:
1601:
1599:
1598:
1589:
1588:
1579:
1574:
1573:
1552:
1550:
1549:
1544:
1539:
1538:
1456:which becomes a
1455:
1453:
1452:
1447:
1427:
1416:
1412:
1411:
1409:
1408:
1407:
1402:
1392:
1391:
1382:
1380:
1378:
1377:
1365:
1360:
1359:
1316:
1314:
1313:
1308:
1306:
1298:
1290:
1285:
1284:
1275:
1267:
1266:
1239:
1237:
1236:
1231:
1220:
1219:
1203:
1201:
1200:
1195:
1193:
1192:
1176:
1174:
1173:
1168:
1156:
1154:
1153:
1148:
1143:
1135:
1127:
1122:
1121:
1112:
1104:
1103:
1076:
1074:
1073:
1068:
1044:
1042:
1041:
1036:
1012:
1010:
1009:
1004:
980:
978:
977:
972:
960:
958:
957:
952:
940:
938:
937:
932:
908:
906:
905:
900:
895:
893:
892:
887:
883:
878:
870:
860:
859:
854:
850:
845:
837:
830:
822:
821:
740:cutoff frequency
711:Chebyshev filter
696:
686:
678:
672:
670:
669:
664:
659:
651:
646:
645:
644:
625:
623:
622:
617:
612:
609:
607:
602:
601:
591:
590:
571:
570:
565:
559:
555:
550:
546:
542:
541:
540:
507:
505:
504:
499:
494:
491:
490:
489:
480:
479:
460:
459:
454:
450:
448:
428:
419:
415:
385:
374:
360:
358:
357:
352:
347:
345:
328:
264:
262:
261:
256:
249:
243:
242:
237:
229:
209:, amplifier, or
163:half-power point
108:corner frequency
104:cutoff frequency
90:(0 dB) passband.
85:
83:
82:
77:
21:
2849:
2848:
2844:
2843:
2842:
2840:
2839:
2838:
2824:
2823:
2813:
2801:
2796:
2772:
2763:
2761:
2757:
2756:
2714:
2713:
2709:
2694:
2679:
2678:
2674:
2665:
2661:
2652:
2650:
2648:
2627:
2626:
2622:
2617:
2584:
2538:
2532:
2531:
2505:
2499:
2498:
2480:
2475:
2474:
2453:
2448:
2447:
2426:
2421:
2420:
2361:
2355:
2354:
2328:
2322:
2321:
2306:
2296:
2289:
2288:
2284:
2280:
2253:
2238:
2233:
2232:
2206:
2191:
2186:
2185:
2181:
2177:
2100:
2090:
2083:
2082:
2048:
2032:
2016:
2006:
2002:
1994:
1984:
1946:
1945:
1883:
1873:
1834:
1830:
1825:
1824:
1823:, resulting in
1799:
1794:
1793:
1759:
1749:
1745:
1737:
1681:
1680:
1649:
1648:
1590:
1580:
1565:
1564:
1560:
1555:
1554:
1524:
1462:
1461:
1397:
1393:
1383:
1369:
1351:
1350:
1346:
1341:
1340:
1333:
1276:
1258:
1253:
1252:
1250:
1242:Bessel function
1211:
1206:
1205:
1184:
1179:
1178:
1159:
1158:
1113:
1095:
1090:
1089:
1087:
1083:
1047:
1046:
1015:
1014:
983:
982:
963:
962:
943:
942:
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62:(a logarithmic
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2799:External links
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2786:on 2022-01-22.
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801:group velocity
797:speed of light
766:, the maximum
751:
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742:refers to the
719:
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2609:Time constant
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772:optical fiber
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37:
32:
19:
2784:the original
2774:
2724:
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2710:
2682:
2675:
2667:
2662:
2651:. Retrieved
2631:
2623:
1674:
1669:
1334:
1318:
1246:
1079:
805:
763:
760:fiber optics
753:
739:
721:
708:
693:
674:
627:
509:
386:
383:
379:
377:
371:
367:
296:
205:, such as a
192:
182:
172:
124:
111:
107:
103:
93:
46:
39:
2790:MIL-STD-188
792:wave number
732:radio waves
714:any value.
279:first-order
195:electronics
189:Electronics
2653:2008-06-22
2615:References
2576:evanescent
1821:wavenumber
768:wavelength
750:Waveguides
736:ionosphere
683:variable,
510:At cutoff
275:asymptotic
120:attenuated
88:unity gain
2741:1531-1309
2702:505848355
2543:π
2510:π
2482:ω
2428:ω
2366:π
2333:π
2298:ω
2258:π
2211:π
2092:ω
2046:−
2030:−
2014:−
2008:ω
1986:ψ
1952:ψ
1901:ψ
1875:ω
1851:−
1837:∇
1757:−
1751:ω
1720:ψ
1687:ψ
1677:Laplacian
1655:ψ
1608:ψ
1582:ω
1567:∇
1533:ω
1501:ψ
1468:ψ
1418:ψ
1395:∂
1385:∂
1362:−
1353:∇
1278:χ
1260:ω
1186:χ
1115:χ
1097:ω
1062:≥
998:≥
926:≥
876:π
843:π
815:ω
776:waveguide
656:α
637:ω
594:ω
584:α
533:ω
483:ω
473:α
446:ω
440:α
410:ω
340:α
247:≈
199:frequency
175:waveguide
147:band-stop
86:=1 and a
74:ω
60:Bode plot
2828:Category
2582:See also
387:plane is
271:roll-off
215:passband
155:stopband
151:passband
143:bandpass
139:highpass
2749:9594124
2638:383โ384
782:of the
728:skywave
697:is the
681:s-plane
679:is the
203:circuit
179:antenna
135:lowpass
127:filters
96:physics
2747:
2739:
2700:
2690:
2644:
2279:where
1792:where
1300:1.8412
1240:, the
1157:where
1137:2.4048
909:where
675:Where
287:octave
283:decade
250:
244:
177:or an
153:and a
2771:from
2745:S2CID
1013:(but
370:= โ1/
253:0.707
145:, or
110:, or
2737:ISSN
2698:OCLC
2688:ISBN
2642:ISBN
2283:and
2180:and
961:and
691:and
363:pole
297:The
207:line
129:and
102:, a
98:and
2729:doi
1339:),
774:or
722:In
687:is
365:at
289:.)
193:In
94:In
2830::
2792:).
2778:.
2743:.
2735:.
2725:26
2723:.
2719:.
2696:.
2640:.
2578:.
2184::
1635:0.
1282:11
1249:11
1190:01
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1077:.
726:,
701:.
378:j'
305:,
219:dB
185:.
167:dB
141:,
137:,
106:,
2812:c
2751:.
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2501:(
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2240:k
2220:,
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2202:=
2197:x
2193:k
2182:b
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2162:2
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2113:=
2106:2
2102:c
2096:2
2069:.
2063:)
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2054:y
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2018:k
2011:t
2004:(
2000:i
1996:e
1990:0
1982:=
1979:)
1976:t
1973:,
1970:z
1967:,
1964:y
1961:,
1958:x
1955:(
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1928:0
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1690:(
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1480:y
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1471:(
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1421:(
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1375:2
1371:c
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1292:=
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1222:(
1217:0
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1106:=
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1024:=
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1001:0
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969:b
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867:(
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685:ฯ
677:s
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614:.
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529:j
526:(
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404:(
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319:s
316:(
313:H
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231:1
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