Unequal, Equi-phase, 1:N Power Divider Based on a Sectoral Waveguide

Transcription

1 17 INTERNATIONAL JOURNAL OF MICROWAVE AND OPTICAL TECHNOLOGY, Unequal, Equi-phase, 1:N Pwer Divider Based n a Sectral Waveguide A. Mestezk and H. Matzner Department f Cmmunicatin Engineering Hln Institute f Technlg 5 Glmb St., Hln 581, Israel 1 Tel: ; amestezke@gmail.cm Tel: ; Fax: ; haim@hit.ac.il Abstract- A high pwer 1:N divider fr unequal utput amplitudes with equal utput phases, based n a H-plane sectral hrn, is presented. The divider has ne input prt in the rectangular part f the hrn and five utput prts in the sectral part f the hrn. The divider was simulated and measured. Gd agreement between simulatin and measurement was achieved, as well as gd accurac f the utput amplitudes, phases and matching level fr bandwith f abut 46% fr SWR =. Index Terms- Sectral waveguide, unequal pwer divider. I. INTRODUCTION Unequal pwer divider is a ver imprtant cmpnent in a lw sidelbes antenna arras. It is well knwn that ne f the cmmn was t get a radiatin plt with lw sidelbes using antenna arra is feeding the elements f the arra with unequal amplitudes, equi-phase signal, where maximum f the amplitude is applied t the central element and it decreases in ther elements [1]. Unequal pwer distributin with equal utput phases using passive cmpnent was discussed fr example b []. In this case a tw wa unequal Wilkinsn pwer divider based n micrstrip transmissin line with defected grund structure was designed. This structure achieves a divisin rati f -1dB and -7dB at it's utput prts in a frequenc range f 1.GHz t 1.8GHz. Tw wa, unequal pwer divider based n H-plane waveguide T-junctin with tw irises (first fr splitting the input pwer between utput prts and the secnd fr input prt matching) was presented in [3]. Design data was present fr different mechanical dimensins f the divider ver nrmalized frequenc range f.57 < λ λg <.84. A structure based n cmbinatin f unequal T-junctin pwer dividers was presented in [4]. This structure allws unequal distributin f high pwer signals with amplitude errr up t.3db and phase mismatch up t 1.5 between utput prts ver a 1% frequenc band. Unlike unequal structure f pwer dividers, interesting structure f equal, high pwer, pwer divider based n radial waveguide was presented in [5]. The advantages f this structure express in it's radial smmetr, which fr the central excitatin leads t equiphase pwer divisin, cmpactness and capabilit t wrk with high pwer signals. Hwever, in this case ne has t use attenuatrs at the utput prts in rder t have unequal utput amplitudes. In this paper we present an unequal, equi-phase 1:5 pwer divider based n a radial waveguide with H-plane sectral hrn gemetr. The pwer divider was designed t have unequal pwer weights based n Kaiser-Bessel distributin [6]. Phase match in utput prts is als guaranteed b the gemetr f the divider, which is based n radial wave prpagatin. The structure f the paper is as fllws: in sectin II theretical aspects f the pwer

2 171 INTERNATIONAL JOURNAL OF MICROWAVE AND OPTICAL TECHNOLOGY, divider's design are presented. In sectin III simulatin results using CST Micrwave Studi sftware are shwn. Measured results are described in sectin IV, as well as a cmparisn between the design, simulatin and measurement. Finall cnclusins are presented in sectin V. and external radii were ptimized using CST Micrwave simulatin sftware. Table 1: Phsical dimensins f the rectangular waveguide and f the sectral waveguide. A. Gemetr II. DESIGN Rectangular waveguide Sectral waveguide Height (b) = mm Height (b) = mm Width (a) = 4mm Aperture angle (ϕ ) = 6 Length = 37.5mm r = 138.5mm The divider is cmpsed f a rectangular waveguide in its input prt, as shwn in fig. 1, and a sectral waveguide fr the utput prts, as shwn in fig. z Fig.1. The input rectangular waveguide part. x b ϕ σ r µ,ε a Fig.. The utput sectral waveguide part. The phsical dimensins f the pwer divider are presented in Table 1, and were chsen fr getting needed frequenc range and pwer distributin as will be further described. Dimensins f internal z b x B. Operating Frequenc Range Using the rectangular waveguide described in fig. 1, we are planning t wrk, as usual, nl with the dminant mde TE 1 f the rectangular waveguide, which defines a theretical perating frequenc range as fllws [7]: a = 4mm 3.75GHz < f b = mm 7. GHz w(re ct ) < 5 Using the sectrral waveguide described n fig., we find ut that there is mre than ne mde in the frequenc range calculated in sectin II.B. We want t wrk with nl ne prpagating mde fr preventing distrtin in the utput signal and this issue is btained in the sectral hrn structure [8-1]. The thrat f the hrn structure serves as a filter device, allwing nl a single mde t be prpagated freel t the aperture [1]. As a cnclusin we can sa that the perating frequenc range f the sectral hrn structure is defined b TE 1 mde f the rectangular waveguide. The dminant prpagating mde in the sectral waveguide part f the hrn is TM 1 (Pa attentin t differences in crdinate sstem definitin in fig. 1 and fig. ). C. Pwer Distributin The pwer distributin relatinship between the utput prts f the pwer divider can be btained

3 17 frm analsis f the sectral waveguide assuming that there is n backward pwer frm the aperture f the waveguide, frm the circumference f the sectral part, and n mutual cupling between utput prts [8-1]. The pwer densit in the aperture f the sectral waveguide fr TM 1 mde is given b: < ϕ < ϕ H S (1) π / ϕ = ( k 1 ) = Re { } π * E H ϕ ~ sin ϕ ϕ (1) Eq. (1) allws designing f unequal pwer distributin with an thereticall needed ratis between utput prts, but careful must be taken while value f the angle ϕ is t small, in this case pwer distributin behavir is different than described in eq. (1). Fr getting the Kaiser-Bessel distributin, ne needs the fllwing weights: C( ) = db, C( 3) = C( 5) = 1. 91dB, and C( 4) = C( 6) = 8. 3dB, fr α = 1.4 [1]. Using eq. (1), it can be shwn that the utput prt's angles are given as fllws: ϕ = 6, ϕ 1 = 17.8, ϕ = 7.5, accrding t definitin f their lcatin n fig. 3. D. Output Phase Tracking Lw phase mismatch between utput prts is btained b placing utput prts n the same circle line, since in this case all utput prts are lcated n the same wave surface. φ Rint Fig.3. Angles definitin f utput prts. III. SIMULATION φ Rext Fig. 4 describes the gemetr f the simulated divider. P1 is the input prt and prts P, P3, P4, P5, P6 are the utput prts. The results fr the scattering parameters f the divider are presented in fig. 5. It is seen that the divider is matched between 4.9 GHz t 7. GHz fr SWR <. Fig.4. Structure f the 1:5 unequal pwer divider based n sectral hrn waveguide. Fig.5. Simulated S-parameters f the pwer divider described n fig. 4. It is seen that the frequenc range fr SWR < is 4.9GHz < f w < 7.GHz.

4 173 Hence we gt a.3ghz frequenc range (4.5%). The accurac f the Kaiser-Bessel weights is better than.1db and Kaiser-Bessel weights ripple up t 1.1dB. The measured scattering parameters f the divider are shwn in fig. 9 Fig.6. Simulated S-parameter phase f the pwer divider described n fig. 4. Fig. 6 shws that the phase match is lwer than 1.8 between the carius utput prts in the perating frequenc range as defined n fig. 6. IV. CONSTRUCTION AND MEASUREMENTS Pictures f the pwer divider are shwn in fig. 7 and fig. 8 Fig.9. Measured S-parameters f the pwer divider shwing a frequenc range f 4.89GHz < f w < 7.49GHz fr SWR <. Frm measurement results shwn in fig. 9 we get perating frequenc range f.6ghz (46%). The accurac f the Kaiser-Bessel weights is better than.db and Kaiser-Bessel weights ripple is up t 1.dB. Fig.7. A picture f the pwer divider. Fig.1. Measured S-parameter phase f the pwer divider. Fig.8. A picture f the pened pwer divider. Fig. 1 shws a phase matching lwer than 5.1 between the varius utput prts in the perating frequenc range as defined n fig. 9. As can be seen frm fig. 6 and fig. 1 there is a little difference between simulated and measured results, the reasn fr this difference cmes frm small inaccuracies in the manufacturing prcess.

5 174 Table summarizes design, simulatin and measurement results: Table : Cmparisn between design, simulatin, and measurement results Parameter Design Simulatin Measurement Freq. range Pwer weights Output phase mismatch C1-C= -1.91dB C-C= -8.3dB C1-C= -1.8±.3dB C-C= -8.33±1.1dB C1-C= -1.8±.4dB C-C= -8.5±1.dB 1.7 ± ±1.1 V. CONCLUSIONS We presented a 1:5 unequal, equi-phase pwer divider with Kaiser-Bessel weights based n sectral waveguide. Using CST-Micrwave simulatin sftware the theretical idea f radial wave prpagatin in the pwer divider was prven. Measured results are ver clse t the simulated results. The radial wave prpagatin and pwer divider's structure guarantee lw phase mismatch between utput prts and allw wrking with high pwer signals, which can be useful in antenna arras that needs suppl radiatin plt with lw sidelbe level. Achieved perating frequenc range f 46% allws using this kind f pwer divider in a wide spectrum f micrwave sstems. Other pwer distributins can be achieved simpl b changing the angles f the utput prts. Care must be taken int accunt that the distance f uter utput prbes frm the sectr's side brder walls will nt be t small, therwise the apprximatin f eq. (1) wn't be valid. Accurac in manufacturing prcess has directl influence n phase and amplitude parameters f the pwer divider. Jun-Sek Park, Dal Ahn, and Sangwk Nam, "A 4 : 1 Unequal Wilkinsn Pwer Divider", IEEE Micrwave and Wireless Cmpnents Letters, Vl. 11, N. 3, March 1. [3] J. Jubert and S. R. Rengarajan, "Design f Unequal H-plane Waveguide Pwer Dividers fr Arra Applicatins", Antennas and Prpagatin Sciet Internatinal Smpsium, Vl.3, pp ,1996 IEEE. [4] S. Christpher, V. A. Abid Hussain, M. S. Easwaran and V. N. Dabade, "Design Aspects f Cmpact High Pwer Multiprt Unequal Pwer Dividers", Phased Arra Sstems and Technlg, IEEE Internatinal Smpsium, pp , 1996., IEEE. [5] M. E. Bialkwski, V.P. Waris and P. W. Davis "Mdelling and Testing f Radial Divider/Cmbiner", Singapre ICCS aps 94, Cnference Prceedings, Vl.1, pp.-34-4, 1994 IEEE. [6] F. Grss, Smart Antennas fr Wireless Cmmunicatin, McGraw-Hill Cmpanies, Inc, pp. 85, 5. [7] M.D. Pzar, Micrwave Engineering, Secnd Editin, Jhn Wile and Sns, Inc., Ch. 3.3, [8] N. Marcuvitz. Waveguide Handbk, 1986 Editin, IET, Ch..7, [9] R. F. Harringtn, Time-Harmnic Electrmagnetic fields, Jhn Wile and Sns, Inc., 1, Ch [1] S. Silver, Micrwave Antenna Ther and Design, 1-st editin, McGraw-Hill Cmpanies, Inc, pp , REFERENCES [1] F. Grss, Smart Antennas fr Wireless Cmmunicatin, McGraw-Hill Cmpanies, Inc, 5, Ch. 4. [] Jng-Sik Lim, Sung-Wn Lee, Chul-S Kim,