диафрагмированные волноводные фильтры / 78ec391f-f6ec-41bf-b405-b98a0f82a374

Abstract- In this paper, a technique for enhancing the gain of a direct microstrip line fed dielectric resonator antenna (DRA) with a bandpass frequency selective surface (FSS) as superstrate has been proposed. A 3.6 dBi increase in gain is observed when the proposed multi-layered FSS has been placed at a distance of half of the resonating wave length from the ground plane of the microstrip line fed DRA. The antenna with FSS offers a peak gain of 9.1 dBi at the resonating frequency and 5% bandwidth covering the frequency band from 6.42 GHz to 6.75 GHz.

I. INTRODUCTION

In recent years, dielectric resonator antennas (DRAs) have been of interest owing to their attractive features such as small size, low loss at high frequency, wider bandwidth, high temperature tolerance etc [1]. The DRAs can be fed by various feeding mechanisms like direct microstrip line feed, co-axial probe, aperture coupled by microstrip line or coplanar waveguide, conformal strip feed, non-resonant microstrip patch feed etc [2]. Different shape of DRAs like cylindrical, rectangular, hemispherical, elliptical, pyramidal, triangular etc. have been explored and investigated by various researchers in the last few decades. A directive, high gain antenna can be realized using superstrate layer above it. The superstrate layer can be designed with high dielectric materials or engineered structures such as EBG, FSS, AMC. To design a low profile antenna, the superstrate layer should be compact, easy to fabricate, inexpensive, easily available etc. FSS can be good candidate for this purpose. FSS can be designed with various configurations like ring, square loop, strip and patch with slots, etc. [3]-[4].

In this paper, based on the coupled resonator spatial filter (CRSF) FSS presented in [4], a second order, bandpass FSS has been designed for gain enhancement of a direct microstrip line fed DRA. A 50Ω microstrip line has been designed to couple electric and magnetic near-fields from the microstrip line to the DRA. Gain enhancement of the antenna is achieved by placing the FSS at half wave length spacing from ground plane of the antenna.

II. ANTENNA DESIGN

dimensions of 51×51×0.79 mm3, loss tangent of 0.0023 and dielectric constant of 2.7. The rectangular DRA with dielectric constant of 20 has the length of 9.5 mm, width of 9.5 mm and height of 4.5 mm. The height of the DRA has been varied and maximum broadside radiation has been observed when it is 4.5 mm. The DRA has been fed by a 50Ω direct microstrip line with width 2.13 mm. The 50Ω microstrip line has a length of 21.5 mm and some fraction of total length L1=2.26 mm as shown in Fig.1 is placed beneath the DRA to couple the electric and magnetic near field from microstrip line to DRA. The DRA excites fundamental TE111. As shown in the Fig. 2, the DRA resonates at 6.6 GHz with an impedance bandwidth of 7% covering frequency band from 6.39 GHz to 6.83 GHz. Fig. 3 shows the radiation pattern of the DRA at 6.6 GHz. The maximum peak gains both the E- plane and H- plane have been simulated as 5.5 dBi.

x

Port

Microstrip line

Fig. 1. Schematic diagram of the DRA.

The microstrip line fed DRA and FSS have been simulated using commercially available high frequency structure simulator (HFSS). Initially, a rectangular DRA as shown in Fig. 1 has been designed on Arlon AD270 substrate with the

Frequency (GHz)

Fig. 2. Return loss of the DRA without FSS.

Angle (deg)

Fig. 3. Radiation pattern of the DRA without FSS at 6.6 GHz.

III. DRA WITH FSS

The proposed DRA with FSS has been shown in Fig.4 (a). A band pass FSS shown in Fig.4 (b) has been designed to operate at the resonating frequency of the DRA by cascading three layers of patch and an aperture type FSS array has been constructed. The CRSF FSS proposed in [4] has been used as a superstrate to increase the gain of the DRA in the broadside direction. The FSS has the following parameters as F1=F2=17 mm, R1=7.5 mm and R2=2.1 mm. The proposed antenna with the CRSF FSS has found to resonate at 6.6 GHz with impedence bandwidth of 5% covering frequency from 6.42 GHz to 6.75 GHz. The gain of the antenna is found to increase by 3.6 dBi after placing the FSS as a superstrate. Both the E- plane and H-plane have the peak gains of 9.1 dBi. The crosspolarization levels of E-plane and H plane are found below 34 dB and 26 dB from their respective peak values.

FSS

Z

X

DRA

Arlon AD270

Ground Plane

(a)

(b)

Fig. 4 (a) Schematic side view (zx plane) of the DRA with FSS. (b) Configuration of FSS layers.

Frequency (GHz)

Fig. 4. Return loss of the microstrip line fed DRA with FSS.

Fig. 5. Radiation pattern of the DRA with FSS at 6.6 GHz.

IV. CONCLUSION

A direct microstrip line fed DRA with a FSS has proposed for high gain applications. It operates at centre frequency of 6.6 GHz with impedance bandwidth of 5% covering frequency from 6.42 GHz to 6.75 GHz. The simulated peak gain of 9.1 dBi has been observed for the DRA with FSS. It may be found suitable as a receiving antenna with high gain and efficiency in noisy and congested spectrum environments.

ACKNOWLEDGMENT

This work was supported by the University Grant Commission (UGC), India.

REFERENCES

[1]K. M. Luk, and K. W. Leung, Dielectric Resonator Antennas. Baldock, England: Research Studies Press, 2003.

[2]B.Rana, and S.K. Parui, “Nonresonant Microstrip Patch-Fed Dielectric Resonator Antenna Array,” IEEE Antennas Wireless Propag. Lett., vol. 14, pp. 747-750, 2015.

[3]Khjlj R. Pous and D. M. Pozar, “A frequency-selective surface using coupled microstrip patches,” IEEE Trans. Antennas Propag., vol. 39, no. 12, pp.1763–1769, 1991.

[4]H. Zhou, S. Qu, B. Lin, J. Wang, H. Ma, and Zhuo Xu, “Filter-Antenna Consisting of Conical FSS Radome and Monopole Antenna,” IEEE Trans. Antennas Propag., vol. 60, no. 6, pp.3040–3045, 2012.