Compact Multi-band Rectangular Slotted Antenna for Global Navigation Satellite Systems (GNSS)

Mustapha Djebari, Amine Abdelhadi Department of Electronic, Faculty of Technology

University Saad Dahlab of Blida Blida, Algeria

djebari_m@yahoo.fr, abdelaminester@gmail.com

Abstract— An Investigation in a compact multi-band rectangular microstrip antenna with two different slots suitable for future Global Navigation Satellite Systems (GNSS) applications is proposed and experimentally studied. The antenna operates at multiple frequency bands which are L1, L2, L5 for GPS and G1, G2, G3 for GLONASS and E1, E6, E5a&E5b for GALILEO. The proposed antenna is excited by a microstrip feed line and have three frequency bands through loading an U-shaped slot and an inverted H-shaped slot. It achieved good performance within a large 3-dB beamwidth, which will enable the antenna to receive signals from several GNSS satellites. The obtained results of the return loss, radiation patterns and peak antenna gains are presented using computer simulations and measurements. A prototype of the antenna is fabricated; the measured return loss is in good agreement with the simulated one.

Key words: compact, microstrip, antenna GPS, Galileo, Glonass

I. INTRODUCTION In the coming years more than 60 satellites with multiple

ranging signals will be available from Global Navigation Satellite Systems (GNSSs) consisting of the modernized American GPS (L2C and L5), updated GLONASS (L1 and L2), European Galileo (E5a, E5b, and E6) and other regional systems [1, 2]. Therefore, the future navigation receivers should be capable of working for all the GNSS frequencies. This interoperability between the GNSS systems will help in overcoming some of the shortfalls of individual navigation systems such as service guarantees, integrity monitoring, and improved service performance [3]. Recently, the ability to integrate more than one communication standard into a single system has become an increasing demand for a modern wireless communication device. Due to the limited space, it often requires the antenna can work at several frequencies simultaneously [4]. Among the various types of antennas, circularly polarized (CP) antennas are the most desired ones, owing to their inevitable merits like reducing polarization mismatch and multipath fading. To benefit from broadband and low profiles, various shapes and designs of multi-bands

circularly polarized slot antennas have been developed to overcome both the narrow impedance and axial-ratio bandwidths by applying different techniques on patch and ground structures.

Therefore, there are various multi-band antennas that have been developed over the years, which can be utilized to achieve multi-band operations [5, 6, 7]. Based on the design proposed in [5], a compact patch antenna consisting of a rectangular slotted patch with a size of 80 mm x75 mm x1.6 mm and two different shaped slots fed by a 50 Ω microstrip feed line is developed and presented in this paper. The designed antenna is achieved which operates in multi- frequency bands for future GNSS applications.

The simulation software FDTD_Lab [8] developed in our department is used in the design and simulation processes of this antenna. The simulated results on the radiation patterns and return loss indicate good agreements with each other are fully explained in the following sections.

II. ANTENNA DESIGN The proposed rectangular slotted antenna is printed on the

substrate with relative dielectric constant of εr = 4.3 and thickness of 1.6 mm. On the top of the substrate, a rectangular monopole antenna consisting of a rectangular patch with the inverted-H and U-shaped slots is printed to create three major frequency bands. This structure is fed by a single microstrip line of 50 Ω.

On the opposite side of the substrate, a conducting partial ground plane of width Wg and length Lg is placed. The inverted H-shaped slot deals with the bands of (1.24 - 30 GHz) and (1.575 - 1.602 GHz), while the inverted U-shaped slot deals with the bands of (1.176 GHz) and (1.30 GHz).

The final design of the multi-band antenna with a size of

75 mm x 80 mm x 1.6 mm is illustrated in fig.1. The optimized parameters of the antenna are presented in Table 1.

978-1-4673-6195-8/13/$31.00 ©2013 IEEE

Fig. 1. Geometry and dimensions of proposed antenna

(75 mm x 80 mm x 1.6 mm) TABLE I. Optimized parameters of the a Antenna (mm)

Lp Wp Lg Wg WL WD Lf Wf

53.59 72.69 12.43 75.88 42.94 37.94 15.87 6.35

h G Ws L1 L2 L3 L4 W0

1.6 3.72 6.8 30.74 33.48 19.5 5 21

X X1 X2 W1 W2 W3 W4

5 25.59 6 6 11 7 8

III. EFFECTS OF THE PARAMETERS OF THE ANTENNA An important feature of the proposed antenna is the

capability of impedance matching at multiple resonate frequencies using the two slots which are presented above. Figures 2.1, 2.2 and 2.3 show the simulated return loss for the proposed antenna with different dimensions of the slots.

A. Effect of the length L1

The simulated 10 dB return loss for different lengths of the

L1 parameter of the antenna is presented in fig. 2.1. The optimized value of the L1 is given in Table 1. It can be observed that decreasing the length of L1, decreases the band., but don’t change noticeable the first and the second band.

Fig. 2.1 Simulated return loss for the antenna with various lengths of L1

B. Effect of the length L4 To highlight these variations, different values of L4 are

studied. As presented in fig. 2.2, we can see that by increasing and decreasing L4, there is no change in the first and third band frequencies

Picking L4 = 5 mm (optimized value), enhances the antenna with maximum bandwidth of 12 % for the second band, small changes in this parameter (L1) leads to considerable variations in both impedance matching and central frequency of the second band

Fig. 2.2 Simulated return loss for the antenna with various lengths of L4

C. Effect of the length L2 Through extensive simulations and experiments, it was

found that length of the L2 trip should be selected as L2=33.48 mm, small changes in this parameter will cause a slight shift to the left and the right in the middle resonance frequency of the antenna in the second band and decrease impedance matching of the first band as shown in fig. 2.3.

Fig. 2.3 Simulated return loss for the antenna with various lengths of L2

IV. ANTENNA POLARIZATION AND RADIATION PATTERN To illustrate the circular polarization mechanism, which

requires modes of equal magnitude that are in opposite phase, the simulated surface current distributions viewed from the microstrip side are illustrated in Fig. 3.1.

Fig. 3.1 Simulated Distribution of the surface current on the feed and ground of the antenna at 1.278 GHz in 0±, 90±, 180±, and 270± phase.

The direction of the surface currents on the antenna slots

and the microstrip feed network is presented at 1.278 GHz as the phase changes from 0 through 270 degrees. It is observed that the surface current distribution in 90 and 270 degrees are

equal in magnitude and opposite in phase as in 0 and 180 degrees, as shown in fig. 3.1.

The Radiation patterns and directivity of the antenna at

typical frequencies of 1.176 GHz, 1.278 GHz, 1.575 GHz and 1.602 GHz are presented in fig. 3.2, 3.3, 3.4 and 3.5 respectively.

Fig. 3.2 Simulated radiation patterns at 1.176 GHz (Phi=0)

Fig. 3.3 Simulated radiation patterns at 1.278 GHz (Phi=0)

Fig. 3.4 Simulated radiation patterns at 1.575 GHz (Phi=0)

Fig. 3.5 Simulated radiation patterns at 1.602 GHz (Phi = 0)

V. ANTENNA PERFORMANCE The result of the simulated return loss can observed in

fig. 4.1 and we can see that the antenna resonate well at all frequencies. Figure 4.2 shows the VSWR values which are less than 2. All the parameters of the return loss, resonating frequencies and impedances are resumed in table 2.

Fig. 4.1 Simulated return loss of the antenna

Fig. 4.2 VSWR of the antenna TABLE II. Resumed characteristics of the antenna

Figure 4.3 shows the measured return loss result of the

compact antenna. The measured return loss is in good agreement with the simulated one and below -10 dB at all operating frequencies.

Resonating frequency

(GHz)

impedance bandwidth

( % )

Return loss (dB)

1.176 11 (at -15 dB) -32.65

1.278 5 (at -15 dB) -36.80

1.575 30 (at -15 dB) -15.55

1.602 30 (at -15 dB) -31.08

The obtained three operation bands of the proposed antenna are ranging from (1.06-1.23 GHz), (1.23-139 GHz) and (1.53-1.65 GHz) respectively, which are wide enough to cover the required bandwidths of all the GNSS frequencies.

The antenna gains at 1.176/1.278/1.575/1.602 GHz are 2.7dBi, 2.7 dBi, 4.2 dBi and 4.3 dBi respectively.

Fig. 4.3 Comparison of the simulated and measured return loss

Figure 4.4 shows the photo of the realized compact antenna

which has a size of 80 mm x75 mm x1.6 mm. The antenna is printed on substrate with relative dielectric constant of εr = 4.3.

Fig. 4.4 Photo of the realized Antenna

VI. CONCLUSION In this paper, we have investigated printed rectangular

slotted antennas, which is basically a printed microstrip antenna with two different slotted shapes multi-band GNSS applications.

The effects of different dimensions of the slots on the feature of the proposed antenna have also been discussed. Good antenna performances of the operating frequencies across the three operating bands have been obtained. The Simulated und measured results are in good agreement.

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