LY THUYET DÚaNG DAY GHEP VA PHAT TRI^N
3.4 Phat triln ly thuyet duong day ghep 1 He so ghep song ciia duong day ghep
3.4.1 He so ghep song ciia duong day ghep
Trong tap sach Micro\va\c engineering nc'ii licMig cua minh xuat ban nam 2002. tcic gia David Pozar. giac^ su cua hoc Mcn Massachusett. My khong dua ra cae
phucmg trinh tinh loan dc) tc^n hao do ghep scSng giua hai duon^i da> ^^ dai song
song each nhau mc)t khoang s. nen trong cae xi du mị phong cua ong NC cae loạ ho Igc ducmg day ghep. do suy hao tin h,cu lạ nncn dai ihong la bang OdB 1 u> nh.cn.
trong thuc ii khi ch6 tao cae bg loc thong dai sir dung eac duang day ghep Iuon
Iuon xay ra hien tugng suy hao tin hieu trong mi^n dai thong. Co nhi^u ly do d^ giai thich cho hien tugng nay va trong s6 do phai k^ d8n sir m^t mat do ghep song giua hai duang day dan dien song song. Trong muc nay cong thirc tinh do suy hao tai tAn so cgng hucmg cua song truyln tren duong day ghep se dugc xay dung nhSm bo xung cho ly thuyet duang day ghep.
Dau tien, ta xet mot doan duang day ghep c6 chieu dai la / Hinh 3-6c. neu la dat mot nguon cong suat di vao tai cong 1, se co hien tuang song ehay tren ducmg day thu nhat. Dong dien ehay trong duong day thu nhat se ga\ cam ung sang ducmg day thu hai mot dien ap. Neu de cc3ng 2 va cong 4 her mach. cong 3 mac lai nhu Hinh 3-6c thi cong suat di vao cong 1 se di ra tai cc'ing 3. Nt^u duang day ghep cc) dc)
dai la X/4 thi cong suat di vao cong I sc dircrc ghc^p den ecSng 2 \a di ra cong 3 la nhieu nhat. Do do nhijng tin hieu cc) bucrc scbng X=4l neu / ducrc xac dinh trucVc thi he so ghep song la Ion nhat va duoc goi la he so ghep tai tan so cong hucmg k =
\ST,\. k cang Icrn khi ma khoang each giira hai duong da\ cang gan nhau, lire la v
cang nhọ Cong sual mat mat do ghep la:
âni =-201ogk.