天線工程導論 - nuu.edu.tw

1 Cheng-Hsing HsuDepartment of Electrical EngineeringDepartment of Electrical Engineering National United University1 1. 2. 3. 4. 5. 6. : , , .. : , : , ( ), , ( ), ..(), For most antennas, losses are small so that the gain is nearly equal to directivity. Thus, as a practical matter, gain and directivity are often used , dipoles and slots Both loop and dipole have identical field patterns but with Eand Hinterchanged. The horizontal loop is horizontally polarized and the vertical loop is vertically polarizedpolarized. To qualify as a small loop or short dipole, the dimensions should be and slotsdipoles and slots If the dipole has been cut from a metal sheet, leaving a slot, the dipole and slot are said to be and slot are said to be complementary.

2 The field patterns of the dipole and slot are the same but with Eand h ttii th lt To be completely complementary, the sheet containing the slot should be large (ideally infinite) and perfectly conducting. ZZ2020ddsYZZZZ4400==Slot antennaOdtillitOpened-out coaxial-line antennas All of the antennas in Fig. 3-3 are omnidirectional in hh il lihthe horizontal plane with a null in the vertical (zenith) (tili)tOpened-out 2-conductor(twin-line) antennasOpened-out waveguide antennas (aperture types)Flatsheet reflector antennasFlat-sheet reflector antennasFigure37 Figure3-7 Flat reflector antennas with one and two /2 dipoles (a and b) and 90 or square-corner reflector (c). The directivity of a /2 dipole can be increased by placing it in front of a flat conducting reflector as in (a).

3 An array of two /2 dipoles in front of a flat reflector as in (b) produces higher directivity Even more directivity is obtainedflat reflector as in (b) produces higher directivity. Even more directivity is obtained by folding the flat reflector into a 90 or square corner as at (c).Parabolic dish and dielectric lens antennasdfEnd-fire antennasBroad bandwidth antennas:Broad bandwidth antennas: the conical spiral and the log -periodicThe patch antennaThe patch antenna The patch is a low-profile, low-gain, narrow-bandwidth antennaantenna. Aerodynamic considerations require low-profile antennas on aircraft and many kinds of vehicles. Radiation from the patch is like radiation from two slots, at the left and right edges of the patch. (Isotropic antenna) ( ) (1) < /(2 ) Wheeler(2) < /10 King(3) < /8 Schelkunoff, Friis(), Ra RL Gd=+ (= ) :]dBi)[ (10 LaaaRRRG+ =.

4 AR= RL Ra LaRR+ () (1) (2) (3) (3) cos)1(2)exp(230+ = RjkRjjkRIERl sin)1(4)exp(222300 + = RkRjkRjjkRIERRjl0sin)1(4)exp(2===+ = HHERjkRjkRIHRl R lI 20)(3 lIP=20)(2 l=R)(3 aR ( 2l))(sin)(zkIzI =l )cos()coscos()exp(60kkjkRIjE =ll 120sin60 EHRIjE= = 120 )cos2cos()exp(jkR22 =l sin)2()exp(60 EHRjkRIjE= = 120H= )};2()2ln({152=++= iCIP =xidxxxxCcos)(x][732 =PR :][732 =IRa sin)1(4)exp(20+ = RjkRjkRISjEcos)1(2)exp(423+ = RjkRjkRISHRRRsin)1(4)exp(2223 + = RkRjkRjkRISHRR0=== HEER420)2( aIP= :)(12 P=40)2( aRa= : :)(6 a )i()exp(60kJjkRkIE )sin()exp(601 EHkaJRjkRkaIE= : 120H =.

5 Cos)(II= sincos)}(sin)(sin{)exp(3020 JJRjkRIjE+ = cos)}(sin)(sin{)exp(3020 JJRjkRIjER = = 0, 2gba ==)sinsin2sin()cossin2cos()exp(40 kbkaRjkRVjE =})sinsin(cossinsin)()cossin(cossinsin{ )2()2(222 kkRj+ )sinsin2sin()cossin2cos()exp(4)()cossin( 0 kbkaRjkRkVjEak =})sin(cossin)()cossin(coscossin{ 222222 kkR+ a ::0kV :: k ++ = = Q0cdaaaPPPWPWl = :;:;:PPP :;:;:cdaPPP3212 ;QQQra >== )()(2 .282 .122hQhQrarrar = < = >aQQ0= )(16)2(2hQrar BWVSWRQVSWRBW01 = Q BW Gd 32 r Gd 1 +10 dBi 1 +10 dBi +7 dBiDuroid255 +6 7 dBi + dBi +6 dBi (Glass Epoxy) + dBi 2)(4E10 + dBi = 200200),(),(4ddEEGd 2s L n 2a , , (Axial mode helical antenna) 1 a) 1 2a 2 s b) I 1 c) I 1 I.

6 I(22kJjkr 2sincos)sin()sin(2)2(3010eakakaJreIajEjk rjkre = 8 cos)sin('2)2(3010kaJreIajEje = I :1 )}()({21'11vJvJJnnn+ =2jk )sin(22cos)sin('2)2(2302102kaJesnkaJreIs njEjkrjkrm = sincos)sin()sin(2)2(23010kakaJreIsnjEm =8 +++=dsEEEEIR memea)(12012220 +++=dEEEEEEEEG memed)()(42222 +++dEEEE meme)( (Narrow-Band) (NarrowBand) + ( ) ( ) (BALUN) ()() Z=73+j43 Z=73+j43 (%): :,: [%] =433=MHzf]m[ fMHzf8293433=mmdf [%] = [m] = 1 (NarrowBand)1 (Narrow-Band) 1 130 130 BALUN (Narrow-Band) (NarrowBand) 1/4 (NarrowBand) (Narrow-Band) ( ) 1 A R D A R D A R 1/2 ( ) )

7 A D 1/2 A ( 4(a) (b) ) 1: (()()) 1/4 1/4 A( A) R( R) 2(a) 3 A R2(a) 3 A R 1/4 90 R R A R A R I2 90 3 R 3 R R I2 90 A A 270 A 1/4 90 3 R 3 R 360 A A A 180 D( D) 2(b) 3 ()

8 D A D 13 13 90 D A 90 180 3 4 ( ) FR4 FR4 (a) (b) FR4 4 (NarrowBand) (Narrow-Band) UHF ( :microstrip antenna) : :222relgWL ===})1( {2121 :1/For 2relWhhhWrr++ ++=< :1/For12122hWWWh +}1211{2121 :1/For relhhWrr+ ++= 1W+ (CompactAntenna) (Compact Antenna) (Load Monopole) (a) 1/4 (p) () (b) (c) ][)}4(2cot{2653pFhC =(1) ][ )}(2cot{}1)4{ln(pFdhfC =(1) }81{ = )8(12 DDh+ ][ aspFDChD=<(2) ][ )4ln(d l(1) (1) :] H[ )2cot(}1)2{ln( ll =dfL(2) : df2559bbll] H[ )}2tan()2}{cot(1)2{ln( bbdfL =llEx:(1) :()] H[)2cot(}1)2{ln( ; ).

9 (400==== llLdhMHzf) (}1) {ln( ] H[ )2cot(}1){ln( = = dfL] H[ ) (}1) {ln(400 = 2N] H[ ] H[9539522 NkaL4743] H[56880953] H[ = === ] H[ NEx:(2) :Ex:(2) :]H[)}2()2}{ (1)2{l ( ; ); (450 ==== bbLbMHzflll) (}1) {ln( ] H[ )}2tan()2}{cot(1){ln( = = bbdfLll] H[ ) (}1) {ln(450 = = ( ) (Compact Antenna) (Compact Antenna) : 1 1 ]m[ [MHz][m]300 == 489[MHz] ]cm[ si2L sin2La=]m[ )17( 713 0 m m> 0 Bm B0 :]H[20 ANLm ]H[ 0lLm =[H/m])10( :-60 :: Nm [m]:][m:2 lA 110Z= :)2211(2120fLjRfCjfCja ++ + 21fCj C1 1=aafRRZLf2021)2()2( aaaRfZRRZC02022 =.)

10 : : f1 f2 12 : : : : (loosely couple) : : : : 1 : L C (trap circuit) f f 1/4 f f 1/4 2 1 LCf = F FR4 : (1) (2) (3) (4) UWB(Ultra-Wide Band)UWB(UltraWide Band) DS-UWB : (IR: Impulse Radio) (DS-SS.)