APPLICATION OF DIGITAL CELLULAR RADIO FOR MOBILE LOCATION ESTIMATION IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 DESIGN OF WLAN AND WIMAX BAND REJECTION UTILIZING UWB PLANAR ANTENNA COMPRISING SLIT IN THE CONDUCTOR PLANES SITI FATIMAH JAINAL1, NORLIZA MOHAMED2 AND AZURA HAMZAH3 1Faculty of Engineering, Lincoln University College (LUC), Kelana Jaya, Selangor, Malaysia. 1,3Malaysia Japan International Institute of Technology, UTM Kuala Lumpur, Malaysia. 2Razak Faculty of Technology and Informatics, UTM Kuala Lumpur, Malaysia. *Corresponding author: sitifatimah@lincoln.edu.my (Received: 27th February 2019; Accepted: 30th July 2019; Published on-line:2nd December 2019) ABSTRACT: A compact and low profile ultra wideband planar antenna comprises dual notched-band characteristics for WIMAX and WLAN are presented. UWB communication system is allocated between 3.1 and 10.6GHz, which coexisted with the WLAN and WIMAX frequency bandwidths at 3.3 to 3.6GHz, and 5 to 6GHz, repsectively. The coexistence between multiple frequency bandwidths possibly can cause interference into the communication systems such as data loss and signal disruption. Thus, it is essential to eliminate the coexisted frequency bandwidhs from UWB spectrum. The UWB planar antenna is costructed with a radiator of an elliptical-shaped, and half-ground element which is subjected to suppress the frequency bandwidth for 3.3 to 3.7 and 5 to 6 GHz. Slits are engraved in the elliptical radiator and ground element by etching the conductor elements. Slit shapes are designed in simple and optimized to realize the maximum band notch characteristics. Slit placements are scrutinized and the band notch characteristics are determined. It is considered that the slit in the ground element and the elliptical radiator have stimulated the band notches frequency bandwidths for 3.3 to 3.7 and 5 to 6 GHz, respectively. The UWB planar antennas are compared with the reference antenna and the results are verified. Measured reflection coefficient S11 for band notch peaks at the WLAN and WIMAX frequency bandwidths are about -3.0 and -4.0 dB, respectively. Radiation pattern co-polarizations in the H- and E-plane are in omni- and bi-directional, respectively. Maximum gain G is located in the –z –axis and –x –axis in H- and E-plane in the frequency of interest. Surface currents are distributed in the slit areas. Slits in the elliptical radiator and the ground element are not substantially affect the UWB planar antenna overall performances. ABSTRAK: Antena jalur lebar paling satah yang padat dan bersusuk rendah telah diperkenalkan dan terdiri daripada dua ciri lebar-takik bagi WIMAX dan WLAN. Sistem komunikasi UWB berada pada 3.1 dan 10.6GHz, bertindan dengan jalur lebar frekuensi WLAN dan WIMAX yang berada pada 3.3 hingga 3.6GHz, dan 5 hingga 6GHz, masing- masing. Sifat bertindan antara beberapa jalur lebar frekuensi mungkin akan menyebabkan gangguan pada sistem komunikasi seperti kehilangan data dan gangguan isyarat. Oleh itu, adalah penting bagi membuang jalur lebar frekuensi yang bertindan dengan spektrum UWB. Antena satah UWB telah dibina dengan radiator pemancar berbentuk elips, dan unsur separuh-bumi (lapisan asas) dibawah jalur lebar frekuensi pada 3.3 hingga 3.7 dan 5 hingga 6 GHz. Jalur celahan telah diukir pada radiator elips dan lapisan asas dengan mengukir unsur konduktor. Jalur celahan telah direka mudah dan dioptimumkan bagi mencapai jalur takik maksimum. Kedudukan jalur celahan diteliti dan ciri-diri jalur takik diperolehi. Jalur celahan pada lapisan asas dan radiator elips diperhatikan menyebabkan frekuensi jalur lebar takik sebanyak 3.3 hingga 3.7 dan 5 hingga 6 GHz, masing-masing. 90 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 Antena satah UWB dibandingkan dengan antena rujukan dan dapatan kajian telah disahkan tidak mempengaruhi keputusan antena planar UWB dengan ketara. Ukuran pantulan pekali S11 yand diukur pada frekuensi jalur lebar takik WLAN and WIMAX adalah -3.0 dan -4.0 dB, masing-masing. Corak pancaran radiasi ko-polar pada satah H- dan E- adalah omni- dan bi-arah, masing-masing. Kekuatan isyarat maksima G berada di paksi –z dan –x pada satah H- dan E- pada frekuensi yang dipilih. Elektrik pada permukaan tersebar dalam kawasan jalur celahan. Celah radiator elips dan lapisan asas tidak mempengaruhi prestasi keseluruhan antena satah UWB. KEY WORDS: ultra wideband, planar antenna, WLAN, WIMAX, and slit 1 INTRODUCTION Ultra wideband (UWB) frequency bandwidth is assigned from 3.1 to 10.6 GHz and has been commonly applied for communications and sensors, position location and tracking [1], wireless monitoring of transplanted organs [2], monitoring human’s activities such as sport and quality of sleep by using wireless body network (WBAN) [3], sensor to detects positioning and tracking of a target by a quad-copter and target [4], detection of human’s body behind wall [5], and indoor positioning, radar/medical imaging and target sensor data collection [6-7]. Ultra wideband communication system benefits such as high data rate transfer, less path loss and better immunity to multipath propagation, availability in low- cost transceivers, and low transmit power and low interference, and the requirements in the means of reducing interference due to the coexistence with other narrowband systems have been discussed in [6]. UWB antenna has been proposed in [8] in the means of improving its performances by using conductive adhesive of carbon composite. UWB frequency bandwidth coexisted with other narrowband system and the UWB communication characteristics has been compared with single co-channel interference for various materials of partitions in real environments such as brick board, cloth office partition, concrete block, dry-wall, plywood, structure wood, and single co-channel, had been investigated in [9] where the study shows that the channel capacity had degraded with interference for mostly on the drywall partition and found lowest for structural wood partition. UWB interference has been studied in [10] and channel loss estimation using the Okumura channel and tested within the ZigBee circuit with dual-power. Possible interference between an indoor UWB system and an outdoor fixed wireless access (FWA) system operating in the 3.5-5.0 GHz has been discussed in [11]. Multiband-orthogonal frequency-division multiplexing (MB-OFDM) coexistence with time hopping ultra- wideband (TH-UWB) networks has been studied analytically in the means of modeling the interference for TH-UWB [12]. Mutual interference performance has been studied in [13] by performing pulse shaping from UWB to other narrowband system. The wavelet technique and reduction of interference from other narrowband system to UWB system in conjunction with Transmitted-Reference (TR-UWB) signaling scheme with adaptive receiver is utilized. Multiple access interference in the bi-orthogonal modulation for UWB communication systems performances has been investigated in [14]. UWB interference such as UWB activity or UWB density is a critical matter when protecting WiBro performance and analytical method based on a system level simulation of a WiBro (OFDMA) is proposed in [15]. The narrowband interferences which had affected the wideband system has been investigated and characterized in [16-17]. Interference from a UWB transmitter into a narrowband receiver has been studied in [18]. 91 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 The impacts of ultra wideband in narrowband interferences have also been investigated in [19-22] and had described the degradation of the system, and although filtering can be used in the system in the means of correcting the narrowband interference, it has failed in at high interference level. The analysis of the effect of narrowband interference on UWB system in the presence of multipath fading had demonstrated narrowband problems at certain condition as stated in [23]. UWB signals had encountered many interference sources primarily from narrowband systems and also had affected many narrowband radios as described in [24]. Thus, studies have been indicating that the coexistence between multiple frequency bandwidths could cause interferences to other communication systems. The effects could be in signal degradation, data loss, buzzing sound and communication error. Furthermore, more severe effects could have been resulted by the interference such as system failure and malfunction. Thus, it is essential to eliminate the coexistence frequency bandwidth from the UWB frequency bandwidth. There are various methods to suppress the mutual narrowband interference (NBI) in UWB communication system. Chirp waveforms of two non-linear UWB based on the arctrigonometric and archperbolic variable is proposed in the means of alleviating the narrowband interference (NBI) in [25]. The effect of interference to bit error rate performance which used the time hopping pulse modulation for impulse radio ultra- wideband is analyzed in [26]. Method of using chirp waveforms of non-linear in the means of suppressing the interference of narrowband in UWB communication system has been explained in [27]. Band-stop filter is applied to prevent the narrowband interference (NBI) in a receiver for transmitted-reference ultra-wideband (TR-UWB) systems consists of narrowband interference (NBI) and inter-pulse interference (IPI) mitigation [28]. A null phase-shift polarization (NPSP) which combined a linear polarization-vector transformer (PVT), single notch polarization (SNP) filter and an amplitude and phase compensator (APC) has been proposed in [29] to suppress narrowband interference (NBI). Elimination of narrowband interference (NBI) could use antenna design modification as an option. The method is simple and low profile as it requires the etching of the conductor element of the antenna which has been reported [30-38]. Structure for the reference and proposed antenna were discussed in section 2. Results were substantiated in section 3 and then concluded in section 4, respectively. 2 STRUCTURES OF UWB PLANAR ANTENNAS Slit placements in the elliptical radiator and ground element are simulated in the early stage for UWB planar antenna type 2A and 2B. Slit is etched in four points known as point a, b, c, and d, consecutively as depicted in Figure 1. Slit is etched in one-sided of the elliptical element and ground plane as it is in symmetric. Thus, the results would be in identical. The elliptical radiator and ground element is divided into two parts (lower and upper). The origin is placed in the middle point of the elliptical radiator and ground element, respectively. Slit is positioned in the centre of the lower and upper area of the elliptical radiator and ground plane. The point coordinates for the slit placement a, b, c, and d are tabulated in Table 1. Slit placements are simulated consecutively and the reflection coefficients S11 are compared. Band notch characteristics are studied in the means of achieving the desired band notch frequency bandwidths. Slit placements are optimized in order to obtain the optimum band notch characteristics for UWB planar antenna type 2A, and 2B, respectively. The finalized slit configurations are listed in Table 2. 92 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 Fig. 1. Slit placements for UWB planar antenna Table 1: Slit placements in the elliptical element and ground plane Point P(x,y,z) a P(-6, 12, 0.035) b P(-6, 4, 0.035) c P(-11,-6, 0.035) d P(-11,18,0.035) Table 2: Parameters for slit S1 and S2 Antenna type Slit type Parameter Dimension 2A S1 Length, l 7.12 mm Width, w 1.10 mm Slope angle, 7.98 deg S2 Length, l 11.0 mm Width, w 0.60 mm Slope angle, 39.43 deg 2B S1 Length, l 8.28 mm Width, w 0.13 mm Slope angle, 1.38 deg S2 Length, l 11.27 mm Width, w 0.60 mm Slope angle, 41.04 deg The reference, UWB planar antenna type 2A, and 2B structures are illustrated in Figure 2 and the dimensions are tabulated in Table 3. UWB planar antenna type 2A and 2B substrates used FR-4 with the permittivity r of 4.6 and 4.4, respectively. The dielectric electric tangent delta is given 0.019. Size of the reference antenna is compact. The conductor planes are placed one-sided on the substrate and half-ground element is used. Thickness of the substrates for UWB planar antenna type 2A and 2B are different due to the value of the substrate permittivity r, thus to achieve impedance matching. 93 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 UWB planar antenna type 2A and 2B used the thickness hs(2A)=1.6 and hs(2B)=0.76 mm, respectively. However, the conductor planes thickness and the size of the antenna are maintained. Impedance matching is achieved by determining the eccentricity e of the elliptical radiator as Eq. 1. (1) Fig. 2. UWB planar antenna (a) reference (b) type 2A (c) type 2B (d) side view Table 3: Parameters for UWB planar antenna Parameter Dimension [mm] Ls 45 Lg 24 L1 16 L2 12.8 wg 21 hc 0.035 hs(2A) 1.6 hs(2B) 0.76 r(2A) 4.6 r(2B) 4.4 Slits are engraved in the elliptical radiator and the ground element, respectively. Slit is etched in the middle side of the elliptical radiator for UWB planar antenna type 2A and 2B. However, slit in the UWB planar antenna type 2A is etched slanted compare with slit in horizontal for type 2B. Slit configurations are determined by the impedance matching and to optimize the reflection coefficient S11. Higher value of the reflection coefficient S11 is desired for the band notch characteristics. Slit in the ground plane is etched slanted and downwards in about at the centre of the ground plane. Slit configurations in the ground plane are quite similar to each other for UWB planar antenna type 2A and 2B. However, slits in the elliptical element have major different in slit width w and slope angle, . Theoretically, this is owing to the difference in the substrate permittivity r, and slit S1 and S2 configurations are counted in the means of optimizing the band notch characteristics. Generally, surface current distributions are drifted in the elliptical element compared in the ground plane owing to the feed point. Therefore, slit placements in the elliptical element have become critically affected the band notch characteristics compared in the ground plane, where the surface current is disseminated inferiorly. 94 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 Simulation procedure was depicted in Figure 3. First step is to set the simulation setting. Simulation parameters such as boundary, background, and frequency bandwidth are encoded. Optimization is carried out in the means of achieving the optimum band notch characteristics for UWB planar antenna type 2A and 2B. Reference and UWB planar antenna type 2A and 2B are simulated by time domain in Computer Simulation Software (CST) using Antenna-Planar (Microwave/Radio Frequency/Optical) module. Simulation frequency is allocated between 3 and 11GHz. The boundary condition and reflection level are given in open-space and 0.0001, respectively. Fig. 3. Workflow for UWB planar antenna The open boundary is in convolution perfect match layer (CPML) for minimizing the reflection at the boundary during simulation. UWB planar antenna operating frequency is N Start Setup simulation setting Identify slit S1 parameters for antenna type 2A and Simulation of the antenna type 2A and 2B Reflection coefficient 5~6GHz YES Identify slit S2 parameters for antenna type 2A and Simulation of the antenna type 2A and Reflection coefficient YES Report writing End YES Validation NO Fabrication Measurement Experimental results Simulated results analysis 95 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 between 3.1 and 10.6GHz, thus the reflection coefficient S11 must be below -10dB between this frequency bandwidth. However, the reflection coefficients S11 for the band notch frequency bandwidths must be above -10dB level in the means of eliminating the band notch frequency bandwidths. The higher reflection coefficients S11 level between the band notch frequencies bandwidths the better eliminations of the band notch frequency bandwidths. 3 RESULT AND DISCUSSION The reference, UWB planar antenna type 2A, and 2B performances are compared after optimization of the band notch characteristics by adjusting the slits parameters. It is desired that the UWB planar antenna type 2A and 2B performances are unchanged when compared with the reference antenna. Thus, it is substantiated that the slits existence on the conductor elements not significantly changes the UWB planar antenna type 2A and 2B performances. The UWB planar antennas are compared with [39-40] as their structures are nearly similar to the UWB planar antenna and etching method also been used for the band notching, and the results are comparable. However, the slits structures are more complicated compared to the UWB planar antennas. The reflection coefficients S11 for the band notch peaks are in the same range. The radiation patterns also exhibit in omni-directional and bi-directional for the H- and E-plane, respectively similar to the UWB planar antennas. The numbers of lobes are increased for higher frequency regions. The maximum gains G for the UWB planar antenna is comparable with [39-40] as the maximum gain is achieved at 6.9 dB. However, the overall gains G for [40] is lower than the UWB planar antennas. It is considered that the slit structures in the radiator could affect the overall gain G of the designed antenna due to slit in [40] is considered larger than the UWB planar antenna. Reflection coefficient S11, surface current distribution, radiation patterns, gain, and efficiency are discussed in sub-section 3.1, 3.2, and 3.3, consecutively. 3.1 Reflection coefficient Reflection coefficient S11 for eccentricity e and slits placement is depicted in Figure 4 and 5, consecutively. Band notch characteristics for the slit placements are tabulated in Table 4. The reflection coefficient, S11 level for operating frequency, f is known below -10 dB. The frequency bandwidths for 4.3~4.9 and 7.3~8.7GHz are located above -10dB when e=0, where as for 3.3~8.3 and 8.8~11GHz when e=1, for type A. Frequency bandwidths were to be found at 8.7~9.3GHz for e=0, and are placed for 3.6~9 and 9.7~11GHz for e=1, for type B respectively. The results substantiate that eccentricity e=0.6 is ideal for type 2A and 2B as it is within the operating frequency level. Centre frequencies fc for slit placements at point A for type 2A and 2B is located at 6.7 and 7.3GHz, respectively. Point D is located at 4.4 and 4.3GHz for type 2B, respectively. Thus, point A and D are adjusted in the means of realizing band notch characteristics for 5~6 and 3.3~3.7GHz, respectively. Reference and UWB planar antenna type 2A and 2B were simulated and measured. The comparisons for the reflection coefficient S11 are presented in Fig. 6, respectively. 96 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 (a) Type 2A (b) Type 2B Fig. 4. Reflection coefficient, S11 due to eccentricity e (a) Type A (b) Type B Fig. 5. Reflection coefficient S11 for slit placements 97 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 Table 4: Band notch characteristics due to slit placements Antenna type Point Centre frequency, fc [GHz] Reflection coefficient, S11 [dB] A a 6.7 -5.7 b 7.6 -2.5 c 4.5 -5.1 d 4.4 -8.1 B a 7.3 -6.0 b 8.4 -3.6 c 4.4 -6.9 d 4.3 -9.2 (a) Type 2A (b) Type 2B Fig. 6. Finalized reflection coefficient, S11 for reference and UWB planar antenna type 2A and 2B BN1 and BN2 are known as the band notch characteristics realized for the frequency bandwidth at 5~6 and 3.3~3.7GHz, correspondingly. The dual notched-band characteristics R ef le ct io n co ef fi ci en t, S 1 1 dB Frequency GHz R ef le ct io n co ef fi ci en t, S 1 1 dB Frequency GHz 98 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 for UWB planar antenna type 2A and 2B are tabulated in Table 5. It is substantiated that dual band notch are generated due to the slits in the elliptical radiator and ground element. The slit in the elliptical radiator and ground element are considered to generate the notched- band at the frequency bandwidth in 5~6GHz and 3.3~3.7GHz, correspondingly. Theoretically, it is considered that the frequency bandwidths for 5~6 and 3.3~3.7GHz are suppressed from the UWB communication system. Simulated and measured results are compared and results have shown reasonable agreement between both. Table 5: Dual band notch characteristics performances for UWB planar antenna type 2A and 2B Antenna type Band notch characteristic Centre frequency, fc [GHz] Reflection coefficient, S11 [dB] Frequency bandwidth, fbw [GHz] 2A Simulated BN1 5.5 -3.7 1.0 BN2 3.6 -4.4 0.4 Measured BN1 5.4 -3.4 1.0 BN2 3.6 -3.3 0.4 2B Simulated BN1 5.6 -3.3 1.0 BN2 3.6 -5.0 0.4 Measured BN1 5.4 -3.2 1.0 BN2 3.7 -3.4 0.5 3.2 Surface current distributions Surface current distributions for the reference and UWB planar antenna type 2A, and 2B for the centre frequency fc, 3.5 and 5.5GHz are exemplified in Table 6. Surface currents are centralized around the slits area. Theoretically, the surface currents surge vertically in the elliptical radiator and ground element. Slits are sited horizontally to intercept the vertically-polarized surface current and consequently mismatched the input impedance in the antenna. Surface currents are surged in the edges of the ground element in the lower frequency area and mainly in the elliptical radiator in the middle frequency region. Surface current is surged in slit in the ground plane and elliptical element for the frequency 3.5 and 5.5GHz, respectively. Hence, it is contemplated that slit in the ground plane and elliptical element have generated the band notch characteristics in the UWB planar antenna type 2A and 2B, accordingly. 3.3 Radiation patterns Radiation patterns RP, gain G and efficiency eff of the reference, UWB planar antenna type 2A, and 2B are exhibited in Fig. 7 and 8, consecutively. It is demonstrated that the radiation patterns in the H- and E-plane for the UWB planar antenna type 2A and 2B is in omni- and bi-directional, respectively. Radiation patterns in the H-plane of the UWB planar antenna type 2A and 2B is comparable with the monopole antenna. This is as a result of the vertically positioned of the feeding cable on the ground plane. Radiation patterns RP performances are tabulated in Table 7. It is corroborated that the higher gain G is pointed in the –z –axis and –x –axis in H- and E-plane, correspondingly. However, maximum gain G for the frequencies of interest 7.5 and 9.5GHz for UWB planar antenna type 2B in the E- plane is pointed in the +x –axis. 99 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 Table 6: Surface current distributions for reference antenna and UWB planar antenna type 2A and 2B Antenna type Surface current distribution / Frequency GHz 3.5 5.5 A B 2A 2B It is considered that the slit in the elliptical radiator is placed in the +x –axis, hence has influenced the radiation patterns of the UWB planar antenna type 2B, accordingly. Radiation patterns of the reference are equated with UWB planar antenna type 2A and 2B, and the results are passable. It is preferred that the performances for UWB planar antenna type 2A and 2B not significantly amended from the reference antenna. Radiation efficiency eff for the frequency 5~6 and 3.3~3.7GHz have substantiated deterioration for the UWB planar antenna type 2A and 2B, correspondingly. It is demonstrated that the band notch are realized in the respective frequency bandwidths, accordingly. (a) Type 2A (b) Type 2B Fig. 7. Radiation patterns for UWB planar antenna type 2A and 2B 100 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 (a) Gain G (b) Efficiency eff Fig. 8. Gain G and efficiency eff for UWB planar antenna type 2A and 2B Table 7: Radiation pattern performances for UWB planar antenna type 2A and 2B Antenna type Frequency GHz Main lobe plane Efficiency % Gain dB H- E- Simulate Measured Simulated Measured 2A 4.5 180 162 96.2 94.2 3.6 6.3 7.5 258 196 94.0 100.0 3.6 4.8 9.5 173 136 91.7 83.9 5.3 4.8 2B 4.5 177 164 94.8 81.3 2.9 5.4 7.5 172 347 95.5 100.0 4.0 5.4 9.5 181 42 94.4 87.5 4.7 4.9 101 IIUM Engineering Journal, Vol. 20, No. 2, 2019 Jainal et al. https://doi.org/10.31436/iiumej.v20i2.1097 4 CONCLUSION UWB planar antenna comprises dual notched-band characteristics to decline the frequency bandwidth for WIMAX and WLAN are presented. The method employed in the design is simple and low profile. Slits in the elliptical radiator and ground element apparently have initiated the band notch characteristics in UWB planar antenna type 2A and 2B. The structure of the reference and UWB planar antenna type 2A and 2B uses half- ground plane, and designs are compact. The impedance mismatched is corresponded with the surface currents distributions in the slits area, respectively. The reflection coefficients S11 have decreased promptly at the notched-band frequency bandwidths and have achieved about -3.0 and -4.0dB at the center frequency 5.5 and 3.5GHz, respectively. Gain G values are plunged at the band notch center frequencies, 5.5 and 3.5GHz to 4.0 and 3.5dB, respectively. Radiation efficiency erad for the UWB planar antennas have dropped to 70% from the overall performances. Thus, it is indicated that the frequency bandwidths for 5 to 6 and 3.3 to 3.7GHz are suppressed from the UWB frequency bandwidth, accordingly. However, the radiation patterns for the UWB planar antennas are compared with the reference antenna and have indicated that it is not significantly affected by the slits in the conductor elements. 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