アンテナのゲインが3デービーだからパワーが2倍と一緒・・・
電圧は2倍になったから6デービーのゲイン・・・
デービー・・・デシベル dBのことです。
お気づきの通り同じ2倍でも電力は3dB、電圧は
6dBと異なります。
dBへの換算は
電力の場合 10LOG(倍数)
電圧の場合 20LOG(倍数)
ですのでそうなりますね。
どうしてそうなるのかは、負荷に対し印加する電圧を
2倍にしたら電流も2倍流れ、電力的には4倍となる。
つまり電圧の2倍(6dB)は電力の6dB(4倍)に相当すると
覚えておきましょう。
このサイトを探せば計算式が落ちていますが、
それすら面倒な方に換算表を。。。
参考
dBμVは1μV・dBmは1mWの何倍かなので、表の倍数を
電圧はμV・電力はmWに置き換えてそのまま使えます。
例 (電圧) 60dBμV → 1000μV=1mV
(電力) 40dBm → 10000mW=10W
電圧 | ||||
倍数 | dB | dB | 倍数 | |
ー | ー | 0 | 1 | |
1 | 0 | 1 | 1.1220184543 | |
2 | 6.0205999133 | 2 | 1.2589254118 | |
3 | 9.5424250944 | 3 | 1.4125375446 | |
4 | 12.0411998266 | 4 | 1.5848931925 | |
5 | 13.9794000867 | 5 | 1.77827941 | |
6 | 15.5630250077 | 6 | 1.995262315 | |
7 | 16.9019608003 | 7 | 2.2387211386 | |
8 | 18.0617997398 | 8 | 2.5118864315 | |
9 | 19.0848501888 | 9 | 2.8183829313 | |
10 | 20 | 10 | 3.1622776602 | |
11 | 20.8278537032 | 11 | 3.5481338923 | |
12 | 21.583624921 | 12 | 3.9810717055 | |
13 | 22.2788670461 | 13 | 4.4668359215 | |
14 | 22.9225607136 | 14 | 5.0118723363 | |
15 | 23.5218251811 | 15 | 5.6234132519 | |
16 | 24.0823996531 | 16 | 6.3095734448 | |
17 | 24.6089784276 | 17 | 7.0794578438 | |
18 | 25.1054501021 | 18 | 7.9432823472 | |
19 | 25.5750720191 | 19 | 8.9125093813 | |
20 | 26.0205999133 | 20 | 10 | |
21 | 26.4443858947 | 21 | 11.220184543 | |
22 | 26.8484536164 | 22 | 12.5892541179 | |
23 | 27.2345567204 | 23 | 14.1253754462 | |
24 | 27.6042248342 | 24 | 15.8489319246 | |
25 | 27.9588001734 | 25 | 17.7827941004 | |
26 | 28.2994669594 | 26 | 19.9526231497 | |
27 | 28.6272752832 | 27 | 22.3872113857 | |
28 | 28.9431606268 | 28 | 25.1188643151 | |
29 | 29.247959958 | 29 | 28.1838293126 | |
30 | 29.5424250944 | 30 | 31.6227766017 | |
31 | 29.8272338767 | 31 | 35.4813389234 | |
32 | 30.1029995664 | 32 | 39.8107170553 | |
33 | 30.3702787976 | 33 | 44.6683592151 | |
34 | 30.6295783408 | 34 | 50.1187233627 | |
35 | 30.881360887 | 35 | 56.234132519 | |
36 | 31.1260500153 | 36 | 63.095734448 | |
37 | 31.3640344813 | 37 | 70.7945784384 | |
38 | 31.5956719323 | 38 | 79.4328234724 | |
39 | 31.8212921405 | 39 | 89.1250938134 | |
40 | 32.0411998266 | 40 | 100 | |
41 | 32.2556771344 | 41 | 112.2018454302 | |
42 | 32.464985808 | 42 | 125.8925411794 | |
43 | 32.6693691116 | 43 | 141.2537544623 | |
44 | 32.8690535297 | 44 | 158.4893192461 | |
45 | 33.0642502755 | 45 | 177.8279410039 | |
46 | 33.2551566336 | 46 | 199.5262314969 | |
47 | 33.4419571587 | 47 | 223.8721138568 | |
48 | 33.6248247475 | 48 | 251.188643151 | |
49 | 33.8039216006 | 49 | 281.8382931264 | |
50 | 33.9794000867 | 50 | 316.2277660168 | |
51 | 34.151403522 | 51 | 354.8133892336 | |
52 | 34.3200668727 | 52 | 398.1071705535 | |
53 | 34.485517392 | 53 | 446.683592151 | |
54 | 34.6478751965 | 54 | 501.1872336273 | |
55 | 34.8072537899 | 55 | 562.3413251903 | |
56 | 34.9637605401 | 56 | 630.9573444802 | |
57 | 35.1174971134 | 57 | 707.9457843841 | |
58 | 35.2685598713 | 58 | 794.3282347243 | |
59 | 35.4170402328 | 59 | 891.2509381337 | |
60 | 35.5630250077 | 60 | 1000 | |
61 | 35.7065967002 | 61 | 1122.018454302 | |
62 | 35.84783379 | 62 | 1258.9254117942 | |
63 | 35.9868109891 | 63 | 1412.5375446228 | |
64 | 36.1235994797 | 64 | 1584.8931924611 | |
65 | 36.2582671329 | 65 | 1778.2794100389 | |
66 | 36.3908787108 | 66 | 1995.2623149689 | |
67 | 36.521496054 | 67 | 2238.7211385683 | |
68 | 36.6501782541 | 68 | 2511.8864315096 | |
69 | 36.7769818147 | 69 | 2818.3829312645 | |
70 | 36.9019608003 | 70 | 3162.2776601684 | |
71 | 37.0251669744 | 71 | 3548.1338923358 | |
72 | 37.1466499286 | 72 | 3981.071705535 | |
73 | 37.2664572024 | 73 | 4466.8359215096 | |
74 | 37.3846343946 | 74 | 5011.8723362727 | |
75 | 37.5012252678 | 75 | 5623.4132519035 | |
76 | 37.6162718456 | 76 | 6309.5734448019 | |
77 | 37.7298145034 | 77 | 7079.4578438414 | |
78 | 37.8418920538 | 78 | 7943.2823472428 | |
79 | 37.9525418258 | 79 | 8912.5093813375 | |
80 | 38.0617997398 | 80 | 10000 | |
81 | 38.1697003776 | 81 | 11220.1845430196 | |
82 | 38.2762770477 | 82 | 12589.2541179417 | |
83 | 38.3815618475 | 83 | 14125.3754462276 | |
84 | 38.4855857212 | 84 | 15848.9319246111 | |
85 | 38.5883785143 | 85 | 17782.7941003892 | |
86 | 38.6899690249 | 86 | 19952.6231496888 | |
87 | 38.7903850524 | 87 | 22387.2113856834 | |
88 | 38.889653443 | 88 | 25118.8643150958 | |
89 | 38.9878001329 | 89 | 28183.8293126445 | |
90 | 39.0848501888 | 90 | 31622.7766016838 | |
91 | 39.1808278464 | 91 | 35481.3389233575 | |
92 | 39.2757565469 | 92 | 39810.7170553497 | |
93 | 39.3696589711 | 93 | 44668.3592150963 | |
94 | 39.462557072 | 94 | 50118.7233627272 | |
95 | 39.5544721058 | 95 | 56234.1325190349 | |
96 | 39.6454246608 | 96 | 63095.7344480193 | |
97 | 39.7354346853 | 97 | 70794.5784384137 | |
98 | 39.8245215138 | 98 | 79432.8234724282 | |
99 | 39.912703892 | 99 | 89125.0938133746 | |
100 | 40 | 100 | 100000 | |
電力 | ||||
倍数 | dB | dB | 倍数 | |
ー | ー | 0 | 1 | |
1 | 0 | 1 | 1.2589254118 | |
2 | 3.0102999566 | 2 | 1.5848931925 | |
3 | 4.7712125472 | 3 | 1.995262315 | |
4 | 6.0205999133 | 4 | 2.5118864315 | |
5 | 6.9897000434 | 5 | 3.1622776602 | |
6 | 7.7815125038 | 6 | 3.9810717055 | |
7 | 8.4509804001 | 7 | 5.0118723363 | |
8 | 9.0308998699 | 8 | 6.3095734448 | |
9 | 9.5424250944 | 9 | 7.9432823472 | |
10 | 10 | 10 | 10 | |
11 | 10.4139268516 | 11 | 12.5892541179 | |
12 | 10.7918124605 | 12 | 15.8489319246 | |
13 | 11.1394335231 | 13 | 19.9526231497 | |
14 | 11.4612803568 | 14 | 25.1188643151 | |
15 | 11.7609125906 | 15 | 31.6227766017 | |
16 | 12.0411998266 | 16 | 39.8107170553 | |
17 | 12.3044892138 | 17 | 50.1187233627 | |
18 | 12.552725051 | 18 | 63.095734448 | |
19 | 12.7875360095 | 19 | 79.4328234724 | |
20 | 13.0102999566 | 20 | 100 | |
21 | 13.2221929473 | 21 | 125.8925411794 | |
22 | 13.4242268082 | 22 | 158.4893192461 | |
23 | 13.6172783602 | 23 | 199.5262314969 | |
24 | 13.8021124171 | 24 | 251.188643151 | |
25 | 13.9794000867 | 25 | 316.2277660168 | |
26 | 14.1497334797 | 26 | 398.1071705535 | |
27 | 14.3136376416 | 27 | 501.1872336273 | |
28 | 14.4715803134 | 28 | 630.9573444802 | |
29 | 14.623979979 | 29 | 794.3282347243 | |
30 | 14.7712125472 | 30 | 1000 | |
31 | 14.9136169383 | 31 | 1258.9254117942 | |
32 | 15.0514997832 | 32 | 1584.8931924611 | |
33 | 15.1851393988 | 33 | 1995.2623149689 | |
34 | 15.3147891704 | 34 | 2511.8864315096 | |
35 | 15.4406804435 | 35 | 3162.2776601684 | |
36 | 15.5630250077 | 36 | 3981.071705535 | |
37 | 15.6820172407 | 37 | 5011.8723362727 | |
38 | 15.7978359662 | 38 | 6309.5734448019 | |
39 | 15.9106460703 | 39 | 7943.2823472428 | |
40 | 16.0205999133 | 40 | 10000 | |
41 | 16.1278385672 | 41 | 12589.2541179417 | |
42 | 16.232492904 | 42 | 15848.9319246111 | |
43 | 16.3346845558 | 43 | 19952.6231496888 | |
44 | 16.4345267649 | 44 | 25118.8643150958 | |
45 | 16.5321251378 | 45 | 31622.7766016838 | |
46 | 16.6275783168 | 46 | 39810.7170553497 | |
47 | 16.7209785794 | 47 | 50118.7233627272 | |
48 | 16.8124123738 | 48 | 63095.7344480193 | |
49 | 16.9019608003 | 49 | 79432.8234724282 | |
50 | 16.9897000434 | 50 | 100000 | |
51 | 17.075701761 | 51 | 125892.541179417 | |
52 | 17.1600334363 | 52 | 158489.319246111 | |
53 | 17.242758696 | 53 | 199526.231496888 | |
54 | 17.3239375982 | 54 | 251188.643150958 | |
55 | 17.4036268949 | 55 | 316227.766016838 | |
56 | 17.4818802701 | 56 | 398107.170553497 | |
57 | 17.5587485567 | 57 | 501187.233627272 | |
58 | 17.6342799356 | 58 | 630957.344480193 | |
59 | 17.7085201164 | 59 | 794328.234724282 | |
60 | 17.7815125038 | 60 | 1000000 | |
61 | 17.8532983501 | 61 | 1258925.41179417 | |
62 | 17.923916895 | 62 | 1584893.19246111 | |
63 | 17.9934054945 | 63 | 1995262.31496888 | |
64 | 18.0617997398 | 64 | 2511886.43150958 | |
65 | 18.1291335664 | 65 | 3162277.66016838 | |
66 | 18.1954393554 | 66 | 3981071.70553497 | |
67 | 18.260748027 | 67 | 5011872.33627272 | |
68 | 18.3250891271 | 68 | 6309573.44480193 | |
69 | 18.3884909074 | 69 | 7943282.34724282 | |
70 | 18.4509804001 | 70 | 10000000 | |
71 | 18.5125834872 | 71 | 12589254.1179417 | |
72 | 18.5733249643 | 72 | 15848931.9246111 | |
73 | 18.6332286012 | 73 | 19952623.1496888 | |
74 | 18.6923171973 | 74 | 25118864.3150958 | |
75 | 18.7506126339 | 75 | 31622776.6016838 | |
76 | 18.8081359228 | 76 | 39810717.0553497 | |
77 | 18.8649072517 | 77 | 50118723.3627272 | |
78 | 18.9209460269 | 78 | 63095734.4480193 | |
79 | 18.9762709129 | 79 | 79432823.4724282 | |
80 | 19.0308998699 | 80 | 100000000 | |
81 | 19.0848501888 | 81 | 125892541.179417 | |
82 | 19.1381385238 | 82 | 158489319.246111 | |
83 | 19.1907809238 | 83 | 199526231.496888 | |
84 | 19.2427928606 | 84 | 251188643.150958 | |
85 | 19.2941892571 | 85 | 316227766.016838 | |
86 | 19.3449845124 | 86 | 398107170.553497 | |
87 | 19.3951925262 | 87 | 501187233.627272 | |
88 | 19.4448267215 | 88 | 630957344.480194 | |
89 | 19.4939000664 | 89 | 794328234.724282 | |
90 | 19.5424250944 | 90 | 1000000000 | |
91 | 19.5904139232 | 91 | 1258925411.79417 | |
92 | 19.6378782735 | 92 | 1584893192.46111 | |
93 | 19.6848294855 | 93 | 1995262314.96888 | |
94 | 19.731278536 | 94 | 2511886431.50958 | |
95 | 19.7772360529 | 95 | 3162277660.16838 | |
96 | 19.8227123304 | 96 | 3981071705.53497 | |
97 | 19.8677173427 | 97 | 5011872336.27272 | |
98 | 19.9122607569 | 98 | 6309573444.80194 | |
99 | 19.956351946 | 99 | 7943282347.24282 | |
100 | 20 | 100 | 10000000000 |
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