• Journal of electromagnetic engineering and science
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• v.9 no.2
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• pp.85-97
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• 2009

As operating frequency is raised and as more integration with active and passive elements is required, it becomes difficult to fabricate more than 120 ${\Omega}$ characteristic impedance of a mierostrip line. To solve this problem, an equivalent high impedance transmission-line section is suggested, which consists mainly of a pair of coupled-line sections with two shorts. However, it becomes a transmission-line section only when its electrical length is fixed and its coupling power is more than half. To have transmission-line characteristics(perfect matching), independently of coupling power and electrical length, two identical open stubs are added and conventional design equations of evenand odd-mode impedances are modified, based on the fact that the modified design equations have the linear combinations of conventional ones. The high impedance transmission-line section is a passive component and therefore should be perfectly matched, at least at a design center frequency. For this, two different solutions are derived for the added open stub and two types of high impedance transmission-line sections with 160 ${\Omega}$ characteristic impedance are simulated as the electrical lengths of the coupled-line sections are varied. The simulation results show that the determination of the available bandwidth location depends on which solution is chosen. As an application, branch-line hybrids with very weak coupling power are investigated, depending on where an isolated port is located, and two types of branch-line hybrids are derived for each case. To verify the derived branch-line hybrids, a microstrip branch-line hybrid with -15 dB coupling power, composed of two 90$^{\circ}$ and two 270$^{\circ}$ transmission-line sections, is fabricated on a substrate of ${\varepsilon}_r$= 3.4 and h=0.76 mm and measured. In this case, 276.7 ${\Omega}$ characteristic impedance is fabricated using the suggested high impedance transmission-line sections. The measured coupling power is -14.5 dB, isolation and matching is almost perfect at a design center frequency of 2 GHz, showing good agreement with the prediction.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.1-7
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• 2006

New phase shifters with higher phase shift values are presented using defected ground structures(DGSs). The varactor diodes are mounted on DGSs of termination loads to control the large phase variation of the DGS at resonance. Two types of phase shifters are implemented with a branch-line and a coupled line hybrid. The experimental results of the proposed phase shifters show $135\%$ and $221\%$ increases in maximum phase shills, respectively, compared with those of conventional ones.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.6
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• pp.388-388
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• 2000

A design method for a multisection impedance transforming branch-line hybrid using a genetic algorithm suitable for MMIC applications is proposed. In contrast to the previous design methods, an asymmetric structure is introduced to optimize the hybrid. Optimization is performed within the impedance range to achieve the realizable hybrids with a microstrip line in a desired frequency range. This design method is applicable to the hybrid which has the arbitrary power division ratio, impedance transforming ratio, isolation, directivity and bandwidth. The hybrid designed by the proposed method has 3∼10％ more bandwidth than the previous results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.6
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• pp.28-35
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• 2000

A design method for a multisection impedance transforming branch-line hybrid using a genetic algorithm suitable for MMIC applications is proposed. In contrast to the previous design methods, an asymmetric structure is introduced to optimize the hybrid. Optimization is performed within the impedance range to achieve the realizable hybrids with a microstrip line in a desired frequency range. This design method is applicable to the hybrid which has the arbitrary power division ratio, impedance transforming ratio, isolation, directivity and bandwidth. The hybrid designed by the proposed method has 3∼10％ more bandwidth than the previous results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.5
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• pp.413-420
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• 2009

We propose a novel feed network for a $2{\times}2$ array antenna to form a sectoral conical beam. The proposed feed network, which is a symmetrical structure, consists of four $90^{\circ}$ hybrids, a crossover, and four $90^{\circ}$ delay lines. To verify the performance of the feed network a $2{\times}2$ array antenna and the feed network are fabricated on a microstrip structure, and the radiation patterns are measured at the center frequency of 2.57 GHz. The maximum radiation is measured at the $45^{\circ}$ elevation angle and at the $45^{\circ}$, $135^{\circ}$, $225^{\circ}$, and $315^{\circ}$ azimuth angles depending on the choice of the input port of the feed network.

• FLOWER RESEARCH JOURNAL
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• v.17 no.2
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• pp.128-136
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• 2009

To obtain pure lines for breeding $F_1$ varieties of spreading surfinia and wave petunia, Petunia ${\times}$ hybrida, 20 lines of surfinia petunia and 28 lines of wave petunia that were considered uniform in growth and flowering characteristics were selected by self-pollination of the fifth($S_5$) or the seventh generation($S_7$). The 20 selected lines of surfinia petunia had the branch number ranged from 6.0 to 11.0 cm, and the internode length ranged from 2.0 to 4.2 cm. Among them, ten lines, including '$Pe99-017^7$' were above 60 cm of plant width, above 300 leaves in a plant. Fourteen lines including '$Pe99-017^7$' were more than 150 in the number of flower. In the petal color, thirteen lines, including '$Pe99-017^7$', were red-purple; three, including '$Pe99-007^7$', were purple; '$Pe04-086^7$' and '$Pe04-159^7$' were violet; and line '$Pe072-1^7$' was white. Eight lines including '$Pe02-205-2^5$' ranged from 4.0 to 5.0 cm of flowers diameter, and seven lines including '$Pe04-086^5$' ranged from 3.0 to 4.0 cm of leaf length, which is relatively low. Germination rate of the lines was more than 50%. In the wave petunia, the branch number of the 28 selected lines ranged from 8.0 to 13.0 cm, and the internode length ranged from 1.0 to 3.2 cm, which is relatively higher than surfinia petunias. Among them, ten lines, including '$Pe99-020^7$' were above 60 cm of plant width, above 200 leaves in a plant. Twelve lines including '$Pe04-034-2^5$' were more than 150 in the number of flower. In the petal color, eighteen lines, including '$Pe99-020^7$', were red-purple; three, including '$Pe04-113-4^5$', were red; three, including '$Pe04-263^5$', were white; '$Pe04-201^5$' and '$Pe04-263^5$' were violet blue; and line '$Pe04-072-5^5$' was purple. Nine lines including '$Pe04-201^5$' ranged from 4.0 to 5.0 cm of flowers diameter, and eleven lines including '$Pe04-263^5$' ranged from 3.0 to 4.0 cm of leaf length, which is relatively low. All the lines with various growth and flowering characteristics would be very promising to use as breeding materials for $F_1$ hybrids of spreading petunia, Petunia ${\times}$ hybrida.