Климов А. В., Бойко С. Н. Інститут Космічного Приладобудування вул. Авіамоторна, д. 53, Москва 111250, Росія Тел.: (095) 2739529; e-mail: alexey@antex.ru

Макет був виготовлений на частоту 915 МГц на підкладці з діелектричною проникністю е = 8,5 tg5 = 0,002. Товщина підкладки 8 мм. Розміри топології антени приведені на Fig.1.

Вимірювання діаграми спрямованості проводилися в угломестной площині для двох взаємно перпендикулярних перетинів: перерізу, перпендикулярного щілинах (площина вектора Е) і перетину, паралельного щілинах (площина вектора Н). Виміряні діаграми спрямованості наведені на Fig. 2, 3. ДН в площині вектора Н близька до кругової. В перпендикулярній їй площині ДН близька за формою до вісімці.

Коефіцієнт посилення на центральній частоті склав мінус 2,2 дБ. Смуга частот за рівнем КСХН = 2 склала 4 МГц. Поляризація поля випромінювання лінійна і збігається з напрямком вектора Е в щілинах.

Puc. 2. Діаграма випромінювання в Н-площині Fig. 2. H-plane radiation pattern distribution

III. Висновок

Експерименти підтвердили можливість створення малогабаритних мікрополоскових антен на підкладках з гранично обмеженим розміром екрану. Дослідження показали, що застосування двох щілин дає додаткове перевага в тому, що дозволяє перебудовувати антену в смузі частот близько 10% по відношенню до центральної за рахунок зміни довжин щілин.

IV. Список літератури

[1]  V. Kalinichev, A. Kurushin. Microstrip antennas for mobile phones. Chip News, 2001, September, No. 7(60), p. 7-12.

[2] E. Nefedov, B. Panchenko. Microstrip antennas. М.: Radio i Svjaz ‘, 1986. 145 p.

[3]  Kossiavas G.. PapiernikA.. Boisset J. P.. Sauvan M. The Cpatch: a small microstrip element. “Electron. Lett.”, 1989, 25, No.4, p.253-254.

THE SMALL-SIZED LBAND ANTENNA

Klimov A.V. , Boiko S.N.

Institute of Space Device Engineering

Aviamotornaja str., H53, Moscow -111250, Russia Ph.: (095) 2739529; e-mail: alexev(8>antex.ru

Abstract The research results are considered for the possible way of reduction in size the microstrip antenna by means of additional slot-holes in patch topology. The experimental parameters are given for model ofthe small-sized L-band antenna.

I.  Introduction

Three basic ways to reduce microstrip antenna dimensions are well known: grounding of one end ofthe patch (area reduction is in two times) [1]; use of substrates with the large dielectric constant (area reduction can reach 20 times) [2]; formation of slots in topology of the microstrip antenna (reduction of the area is almost in 4 times) [1, 3].

The first way consists in grounding ofthe one end of microstrip antenna. In this case antenna’s length decreases in two times under operation at the same basic frequency [1]. Such antenna named the F-antenna represents the quarter wave resonator, with one end grounded, and another one opened. Advantage ofthe small size ofthe F-antenna is reached due to reduction of antenna efficiency, because one half of the antenna is excluded from radiation process. Moreover, the Fantennas are usually narrow-band devices.

The second way is physically obvious, but it is in itself poorly productive owing to fast fall of radiation efficiency in process of increasing the dielectric constant of a substrate material (especially in the case of electrically thin substrates).

The third way consists in cutting the slot-hole line in microstrip patch. In this case the antenna current path increases. As a result the resonant frequency decreases compared with antenna without slot-hole line. The insertion of slot-hole line reduces the microstrip antenna size at the same operation frequency. In this case the microstrip antenna size is reduced practically without deterioration of efficiency. The analysis of a near field in such antenna shows, that the electromagnetic energy concentrates in the slot-hole, and, as a consequence, the slot-hole plays the essential role in the far field pattern formation of such an antenna [1, 3].

II.  Main part

The principal feature of the antenna considered was the equality of the patch topology and screen sizes. In the case of one slot-hole [3], antenna feed point should be displaced from the topology center. As a result, when the screen size is small, the currents leak into the feeding coaxial cable armature. At the same time the cable begins to influence on a radiation process, distorting the far field radiation pattern. The simplest way of feeding cable influence elimination is the placing of the feed point at the center of topology. The special way was offered consisting in introduction an additional slot-hole located symmetrically around feed point (Fig. 1).

The experimental model was manufactured for frequency 915 MHz on the substrate with dielectric constant s = 8.5, tg 5=

0.         002. The thickness of substrate is 8 mm. The dimensions of the antenna topology are given in Fig. 1.

The radiation patterns (Fig.2, 3) were measured in perpendicular (E-plane) and parallel (H-plane) planes relative to the slot-holes. Gain on the central frequency was minus 2.2 dB. The bandwidth at VSWR = 2 was 4 MHz. The polarization is linear and coincides with a direction of a vector E in slot-holes.

III.  Conclusion

Experiments verified the possibility to construct small sized microstrip antennas on substrate with extremely restricted grounding screen size. The application of two slot-holes in microstrip antenna topology gives a side benefit that allows antenna retuning in frequency band about 10 % (in relation to central frequency) by means of changing slot-hole lengths.

Джерело: Матеріали Міжнародної Кримської конференції «СВЧ-техніка і телекомунікаційні технології», 2003р.