7/28/2019 thi anten truyn sng cui k 2011

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Trng i Hc Bch KhoaKhoa in - in TB Mn Vin Thng

THI: ANTEN TRUYN SNGThi gian: 80 phtKHNG DNG TI LIU

Cu 1: (3 im)

o li cng sut ca mt anten, ngi ta cho mt ngun pht ni tr 50 nivi anten cn o ny. Khi ta o cng sut thu c ti ti ca anten thu khongcch cho trc l 0 dBm. Mt mt phn cc trong trng hp ny l 1dB. Anten cno ny c tr khng 2550 jZA += . Sau ti v tr anten pht cn o ngi ta thay

bng mt dipole na bc sng th cng sut thu c ti ca anten thu khongcch cho trc l -6 dBm. Mt mt phn cc trong trng hp ny l 0.5dB.

a. Tnh li anten cn o theo dBdb. Gi s anten thu l dipole na bc sng, tn s hot ng l 1GHz, khong

cch anten thu pht l 100m. Tnh cng sut ngun pht

Cu 2: (3 im)

Cho h thng bc x nh thc gm 5 phn t.a. Trnh by m hnh phn b dng trn cc phn t.

b. Xy dng v v th cho h thng bc x trn.c. Nu cc phn t ca h thng bc x l anten c trng bc x

( )

cos2

cos4

=

r

erE

jkr

. Tnh gc gi tr khng v gc na cng sut ca h

thng anten ny.

Cu 3: (2 im)

Cho mt h thng VHF pht sng phn cc ngang dng lin lc khong cch20km. Anten pht c cao 100m anten thu c cao 20m. Cng sut anten pht l10dBm. li anten pht l 8dB. C hai anten nhn nhau hng cc i.

a. Tnh trng thu c ti anten thu.b. Nu anten thu c li 20dB. Tnh cng sut thu c trn anten thu.

Cu 4: (2 im)

Cho mt ng dn sng c kch thc 5.3=a cm, 5.2=b cm.a. Xc nh tn s ng dn sng ny hot ng n mode.

b. Cho tn s 9=f GHz. Tnh s mode truyn c trong ng dn sng.