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[問題] digital receiver實作的書

[ comm_and_RF ]2 留言, 推噓總分: +1

作者: MoonSoul - 發表於 2021/11/19 15:23(2年前)

1^F推bxxl: 有算式,就不難實作. 通常就加減乘除而已1.171.223.233 11/20 13:13

[問題] LO Leakage是什麼意思

[ comm_and_RF ]12 留言, 推噓總分: +2

作者: FP91GX - 發表於 2021/10/05 13:44(2年前)

2^F推bxxl: leakage就是漏電. 漏電當然是愈小愈好1.171.209.216 10/05 18:05

3^F→bxxl: LO leakage是LO漏到訊號路徑上1.171.209.216 10/05 18:08

4^F推bxxl: 如果RF訊號跟LO同頻,就會被汙染1.171.209.216 10/05 18:10

5^F→bxxl: 右圖是刻意設計成RF跟LO不同頻,以避免汙染1.171.209.216 10/05 18:11

[問題] FSK與PSK的Pulse shapping

[ comm_and_RF ]16 留言, 推噓總分: +3

作者: avatarof - 發表於 2021/05/27 13:27(2年前)

13^F推bxxl: pulse shaping的作用就兩種, 降低ISI 跟1.171.213.114 06/06 15:36

14^F→bxxl: 控制spectral mask.1.171.213.114 06/06 15:37

15^F推bxxl: PSK是linear modulation, FSK不是.1.171.213.114 06/06 15:41

16^F→bxxl: 所以同樣的濾波器用在兩邊的效果不太一樣1.171.213.114 06/06 15:42

Fw: [建議] 民間基地台國防武器

[ comm_and_RF ]10 留言, 推噓總分: +3

作者: eduishappy - 發表於 2020/11/28 08:31(3年前)

3^F推bxxl: 這種方式老早就沒用了吧,美國軍方發展的220.129.9.17 11/29 18:42

4^F→bxxl: FH/DS展頻通訊就是用來對付narrowband jamer220.129.9.17 11/29 18:42

5^F推bxxl: 再說指向性高,代表你可以干擾的空域面積很小220.129.9.17 11/29 18:49

6^F→bxxl: 飛機剛好經過的時間就會很短,搭配跳頻等技術220.129.9.17 11/29 18:49

7^F→bxxl: 會被你干擾到的時間比例又再大幅下降.220.129.9.17 11/29 18:50

8^F→bxxl: 還有這種東西應該只能干擾通訊,不會讓飛機220.129.9.17 11/29 18:50

9^F→bxxl: 墜毀.220.129.9.17 11/29 18:51

10^F→bxxl: 現代飛機不會設計成收不到通訊就墜毀吧220.129.9.17 11/29 18:52

[問題] 關於TDMA/FDD,FDMA/TDD

[ comm_and_RF ]6 留言, 推噓總分: +2

作者: MapleStory55 - 發表於 2020/09/26 15:59(3年前)

3^F推bxxl: 這個去看規格或介紹就有實際例子了114.45.101.81 09/29 08:50

4^F→bxxl: 比如說GSM就是TDMA/FDD114.45.101.81 09/29 08:53

5^F推bxxl: GSM https://bit.ly/3kVqPTP114.45.101.81 09/29 08:56

[請益] 計算SER及BER的疑問

[ comm_and_RF ]5 留言, 推噓總分: +2

作者: u836224 - 發表於 2020/07/15 23:47(3年前)

1^F推bxxl: 因為兩個bit只錯1個,所以BER~SER/2220.136.208.226 07/17 08:32

[問題] PAPR問題請教

[ comm_and_RF ]26 留言, 推噓總分: +7

作者: End1essRain - 發表於 2020/04/21 01:15(4年前)

21^F推bxxl: PAPR有公式的啊,兩個都算出來16QAM比較大114.25.16.119 04/23 09:42

22^F→bxxl: 如果peak點相同,那16QAM的average必定較小114.25.16.119 04/23 09:43

23^F→bxxl: 是看peak/avg ratio, 不能只看peak114.25.16.119 04/23 09:43

[問題] 為什麼PAM4傳輸速度可以是NRZ的兩倍？

[ comm_and_RF ]4 留言, 推噓總分: +2

作者: brent43 - 發表於 2020/03/26 10:57(4年前)

3^F推bxxl: PAM, 4個level只能代表2個bit的資訊114.45.100.221 03/26 17:02

4^F→bxxl: 跟幾個眼睛沒關係114.45.100.221 03/26 17:02

[問題] 複數高斯，雷利分佈跟capaity的關係

[ comm_and_RF ]15 留言, 推噓總分: +4

作者: ironstark - 發表於 2020/02/08 20:18(4年前)

5^F推bxxl: Rayleigh跟complex Gaussian, 的單點機率都220.136.123.234 02/09 16:02

6^F→bxxl: 都是0啊. 他們的pdf機率密度不為0, 但是任意220.136.123.234 02/09 16:03

7^F→bxxl: 的單點機率為0220.136.123.234 02/09 16:03

8^F→bxxl: 這也就是1F說的,區分p.d.f跟機率220.136.123.234 02/09 16:04

[問題] 通道估測跟CSI問題

[ comm_and_RF ]4 留言, 推噓總分: +1

作者: ironstark - 發表於 2019/11/29 14:25(4年前)

1^F推bxxl: 可以.114.45.16.95 12/06 09:36

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