ABSTRAKSI: ABSTRAK
Antena Tricula Omnidireksional Chebyshev ini dirancang bangun dengan dua tujuan :
1. Untuk menyediakan prototipe antena Omnidireksional berpita sangat lebar, supaya dapat digunakan oleh beberapa operator secara bergotong royong, untuk menghemat menara dan lahannya.
2. Untuk membuktikan hipotesis dari pembimbing 1 bahwa antena adalah pemadan impedansi antara ruang propagasi dengan saluran radio.
Spesifikasi yang harus dipenuhi adalah : frekuensi kerja 0,3 GHz – 3,0 GHz dalam VSWR ≤ 1,5:1 pada terminal 50 Ω anbalan, gain ≥ 2,14 dBi, omnidireksional, dan berpolaritas linier. Ia harus dibangun dengan saluran strip kembar jajar, berdasar transformator Chebyshev untuk digunakan di udara atau hampa; menggunakan balun jenis monokonik supaya berpita lebar tetapi tanpa lilitan pada toroida.
Dengan kaidah saluran strip kembar jajar, diperoleh konstruksi (susunan bahan dan ukuran masing-masing) sebagai berikut : N = 5,098 ≈ 6 tingkat, εr1 = 3,78 (kaca l1 = 23,3 mm), εr2 = 2,96 (kertas asturo l2 = 26,4 mm), εr3 = 2,25 (puzzle l3 = 30,3 mm), εr4 = 1,96 (kertas kalender STT l4 = 32,4 mm), εr5 = 1,49 (kertas koran l5 = 37,2 mm), εr6 = 1,16 (sterofoam l6 = 42,1 mm); menggunakan strip tembaga jajar lebar (w) 3,44 mm x panjang (l) 220 mm x spasi (s) 20 mm (dipilih). Balun monokonik dibangun dari tembaga bersudut konik 90° tinggi (s) = 20 mm, berterminal ZT = 50 Ω anbalan.
Melalui pengujian spesifikasi di pekarangan IT Telkom didapat hasil sebagai berikut. Didalam VSWR ≤ 1,5 ternyata frekuensi kerja 0,95 GHz – 3,0 GHz pada terminal 50 Ω anbalan, gain = 8,381 dBi pada frekuensi 1,8 GHz dan gain = 7,059 pada 2,4 GHz, berpola radiasi omnidireksional, dan berpolaritas elips.
Dari hasil pengujian spesifikasi di atas, maka dapat disimpulkan bahwa sebagian besar spesifikasi dari antena ini telah terpenuhi, hanya saja lebar pita dan polarisasi dari antena ini belum tercapai. Untuk penepatan frekuensi kerja 0,3 GHz – 3,0 GHz disarankan spasi (s) = 20 mm diubah menjadi 50 mm dan mengubah sistem catuan menjadi monotriangular biasa serta penggandengannya diubah secara kapasitif bukannya konduktif. Untuk memperbaiki hasil uji agar memenuhi spesifikasi, maka disarankan supaya IT Telkom membuat ruang tanpa gema karena hasil uji akan lebih baik jika dilakukan di dalam ruang tanpa gema.
Kata Kunci : Antena Tricula, Transformator Chebyshev, Saluran Strip KembarABSTRACT:
This Chebyshev Omnidirectional Three-ivory Antenna is designed in two purposes: 1. To supply a wideband omnidirectional antenna prototype that can be used by some operators at once to economize the load of tower and its field. 2. To prove the hypothetic of first advisor which is told that antenna is a device that used as a transformers between free space and transmission lines. The spesifications that must be fulfilled are : working frequency 0.3 GHz – 3.0 GHz in VSWR ≤ 1.5:1 at 50 Ω unbalance; gain ≥ 2.14 dBi; omnidirectional pattern and linear polarization. This antenna should be constructed with two strip rows, based on Chebyshev transformer which is used in air or vacuum; using a monoconic as balun to deliver a wideband antenna without a toroida.
Based on twin rows strips theory, the construction is obtained (with the materials and size), they are : N = 5,098 ≈ 6 levels, εr1 = 3,78 (glass l1 = 23,3 mm), εr2 = 2,96 (asturo paper l2 = 26,4 mm), εr3 = 2,25 (puzzle carpet l3 = 30,3 mm), εr4 = 1,96 (STT date paper l4 = 32,4 mm), εr5 = 1,49 (newspaper l5 = 37,2 mm), εr6 = 1,16 (styrofoam l6 = 42,1 mm); using brass strip with width (w) 3,44 mm x length (l) 220 mm x space (s) 20 mm (choosen). Monoconic balun was built by 90° brass pieces, 20 mm in height, terminal 50 Ω unbalance.
By measurement of these spesification in IT Telkom’s garden, the results are : in VSWR ≤ 1,5 the working frequency 0,95 GHz – 3,0 GHz at terminal 50 Ω unbalance, gain = 8,381 at 1,8 GHz and gain = 7,059 at 2,4 GHz, omnidirectional pattern, and ellips polarization.
From the results of the spesification measurement above, it can be seen that most of the spesification from this antenna was fulfilled, only the lower frequency and the polarization is out of plan. To make the working frequency 0,3 GHz – 3,0 GHz, it suggest to make the space (s) = 20 mm become 50 mm and change the monoconic become monotriangular and coupling between the strip and the monoconic should become coupling-capasitive, not conductive. To fix the results that fulfill the spesification, it suggest that IT Telkom shoul make an anechoic chamber because the good measurement should be done in an anechoic chamber.Keyword: : Tricula Antenna, Chebyshev Transformer, Two Strip Rows