Design and Fabrication of High Gain Multi-element Multi-segment Quarter-sector Cylindrical Dielectric Resonator Antenna

1 Introduction

The demand of wideband and high gain antenna is increasing rapidly in the area of wireless communication. To achieve these requirements, the dielectric resonator antenna (DRA) can be an attractive choice for antenna designer due to their advantages such as wide bandwidth, high radiation efficiency, easy excitation techniques and small size [1]. The cylindrical dielectric resonator antenna (CDRA) was the first antenna used as a radiator [2]–[4]. It has been excited with several fundamental modes such as TE_01δ, TM_01δ, HE_11δ, EH_11δ, TE_011+δ etc. for different applications with different feeding techniques [3], [4]. Due to nonappearance of ohmic losses as well as non-existence of surface wave, DRA shows high radiation efficiency compare to microstrip patch antenna [3]–[5].

For the bandwidth and gain enhancement of the DRA, some methods and approaches have been reported in the literature [6]–[12]. Multi-segmentation and stacking approach has been proved to be an effective approach for bandwidth as well as gain enhancement [6]–[10]. The splitting and sectoring of the basic shape/geometry has also been reported for bandwidth enhancement [11], [12]. The compact cylindrical sector DRA takes less radiation area compared to conventional CDRA due to sectored face and it has been introduced with a 75 % reduction in volume [12]. Through the stacking, 20 % increase in impedance bandwidth has been reported with low profile DRA [13] and the 1.2 dBi gain improvement has also been achieved.

Monopole radiation pattern with the concept of multi-element [14], [15] and splitting of the basic shape has been reported in [16]–[20]. Four element CDRA has been proposed by Guha et al. [15] for improvement in impedance bandwidth with monopole like radiation pattern. The split and segmented hemispherical DRAs have been explored for monopole radiation type, which provides 35 % impedance bandwidth as broadband DRAs [16]. For the wideband, four elements triangular and rectangular DRAs excited with coaxial probe has been designed which provides monopole radiation patterns with 35 % bandwidth [17], [18]. Half split and half split-segmented cylindrical DRA has been investigated as monopole radiation pattern for wide bandwidth [9], [21]. For the gain enhancement, hemispherical and triangular DRA has been investigated for wideband applications [8], [22], [23].

This paper presents the design guidelines for multi-element multi-segment q-CDRA (MEMS q-CDRA) for wideband applications. The simulation study of proposed q-CDRA has been performed through Ansoft HFSS simulation software. The proposed MEMS q-CDRA shows very good enhancement in bandwidth as well as in gain. The prototype of MEMS q-CDRAs have been fabricated and tested. Simulated results have good agreement with the measured one. The proposed q-CDRA provides 133.8 % bandwidth (|S₁₁|≤−10 dB) with 6.65 dBi measured gain for uniform monopole-like radiation pattern, which has much higher bandwidth and gain compare to four elements q-CDRA [19] and dual segment (DS) q-CDRA [20].

2 Antenna geometry

The multi-element multi-segment q-CDRA (MEMS q-CDRA) has been designed by splitting uniformly a mold DRA to form multi-element and then stacking of that DRA with multiple layers. The splitting of the CDRA has been performed in such a way that it form equal air gap between DR elements as shown in Figure 1. The DR elements have been excited through coaxial probe in such a way that all sectored q-CDRA corner touches probe, as visible in elevated top view in Figure 1. For perfect matching and coupling of the q-CDRAs, the excitation has been kept at the center position and for simplification of excitation; coaxial probe feed has been chosen. The radius of the each segment is ‘a’ and the effective height of MEMS q-CDRA is ‘h_eff’. The MEMS q-CDRA has several segment (n) with every segment has its own dielectric constant (εrn,n=1,2….n) and height (hn,n=1,2….n) at respective position.

Figure 1:

Geometry for formation of MEMS q-CDRA from a solid cylinder.

3 Approach and analysis

A general approach and guide line with the help of simulation results has been prepared for bandwidth as well as gain enhancement. From the single homogeneous medium low bandwidth has been achieved in [19]. To overcome this problem, MEMS concept with sectoring of CDRA has been introduced. Different segment with different dielectric constant can control the bandwidth and resonance frequency, as it is given from theory that the bandwidth is inversely proportional to the dielectric constant of the material [3]. It can be also observed that the height of different layer and probe also affects the bandwidth as well as resonance frequency and the optimization of different segment height with height of the probe has been performed. In this section, a general guideline has been proposed to achieve the highest bandwidth with high gain for MEMS q-CDRA. The selection of number of layer with appropriate dielectric constant has been discussed.

3.1 Initial approach

In the beginning, four elements q-CDRA in composite form has been designed and fabricated, which is shown in Figure 2. Each element has dimensions of height ‘h’=13 mm and radius ‘a’=4 mm. The q-CDRAs has been kept on metallic ground plane (99 % copper) of size 50 mm×50 mm×3 mm. The ground plane has been optimized for best antenna performance. The optimized dimension of ground plane has act as perfect infinite ground plane for DRA, as the dimension of DRA is very less compare to ground plane. The q-CDRA has dielectric constant (Ɛ_r) of 9.8 (Alumina ceramic, 99 %). The selection of dielectric material has been performed through optimization technique for different dielectric constant with antenna performance as shown in Figure 3. Here, in Figure 3 dielectric constant of the material has been varied from 2.0 to 10.0. The value of refection coefficient is decreasing as dielectric constant value increasing, which shows better impedance matching. From Figure 3 and Table 1, it can be perceived that the dielectric constant (9.8) has showing better performance as compare to other dielectric constant value for four elements q-CDRA. The aspect ratio (2a/.h=0.62, ‘h’=13 mm and ‘a’=4 mm) of the q-CDRA has been kept constant and antenna performance has been studied and compared in Table 1. From Table 1, it can be observed that, the gain of the antenna has been almost increasing with increase in dielectric constant. The maximum coupling can be observed near dielectric constant 10.0 for desired application based operating frequency band. A fair bandwidth and gain can be observed at dielectric constant 9.8, which is commercially available dielectric material for fabrication. As, it is known that the |S₁₁| below −10 dB shows around 90 % of power transmitted and remaining 10 % of the power reflected back. The value of minimum |S₁₁| shows maximum transmission of power [24]. The selection of dielectric constant has been chosen each time through simulation and simulated data has been compared in a single graph.

Figure 2:

(a) Geometry and (b) Fabricated prototype of four elements q-CDRA [19].

Figure 3:

|S₁₁| versus frequency curve for different dielectric constant of the four elements q-CDRA with fixed aspect ratio (a/h=0.3, h=13 mm and a=4 mm).

Table 1:

Antenna performance for variation of dielectric constant (εr) with fixed aspect ratio (2a/h=0.62, a=4 mm and h=13 mm).

Dielectric constant (εr)	Resonant frequency fr(GHz)	% Bandwidth (Below −10 dB)	Gain (dBi)	Min. Reflection Coefficient (|S11| ≤−10  dB)
2.0	6.5	30.76	1.5	−15 dB
3.0	6.4	39.06	1.9	−18 dB
4.0	6.2	77.41	2.3	−18 dB
5.0	6.0	78.43	2.6	−19 dB
6.0	6.0	79.65	3.1	−20 dB
7.0	6.0	66.66	3.2	−22 dB
8.0	6.1	57.37	2.7	−35 dB
9.0	6.2	64.51	4.1	−25 dB
10.0	6.8	54.41	4.7	−55 dB
9.8	6.9	59.42	4.7	−55 dB

The geometry and fabricated prototype of four elements dual segment (DS) q-CDRA has been shown in Figure 4(a) and 4(b) respectively. Each segments of dielectric constant has been chosen as commercially available low dielectric constant (Teflon=2.1, Epoxy FR4=4.4, k−6=6.0) and high dialectic constant material (Alumina=9.8). The lower segment dielectric constant (εr1) should be low compare to upper segment dielectric constant (εr2) to enhance the bandwidth, as it is observe from Table 2. The overall dimension of the antenna has been unchanged for analysis in Table 2. The highest bandwidth with fair gain has been achieved for dielectric constant 2.1 (lower segment) and 9.8 (upper segment). The operating bandwidth has been observed below −10 dB of |S₁₁|, resonant frequency has been observed at minimum |S₁₁|. The % bandwidth has been calculated through relation: % Bandwidth=fh−fl/fr, fh is higher cut off frequency and fl is lower cut off frequency for −10 dB of |S₁₁|.

Figure 4:

(a) Geometry and (b) Fabricated structure of four elements dual segment (DS) q-CDRA.

Table 2:

Antenna performance with layer arrangement of four elements DS q-CDRA (For two layers), effective height (h_eff)=13 mm.

Lower Segment (I)		Upper Segment (II)		Operating Bandwidth (GHz)	Resonant Frequency (fr) GHz	% Bandwidth	Gain at Resonant Frequency (dBi)
εr1	h1 (mm)	εr2	h2 (mm)
2.1	4.0	9.8	9.0	5.1–11.5	7.5	85.33	4.35
9.8	4.0	2.1	9.0	4.7–6.4	5.7	32.38	4.04
9.8	9.0	2.1	4.0	5.4–9.8	7.6	49.25	4.58
2.1	9.0	9.8	4.0	6.2–10.3	8.2	50.00	5.23
4.4	4.0	9.8	9.0	5.0–9.6	5.9	77.96	4.20
6.0	4.0	9.8	9.0	4.8–8.5	5.8	63.79	4.15

Similar to Table 2, four elements three segment q-CDRA has been analyzed for different dielectric constant with different position in Table 3. The desired antenna performance has been achieved with commercially available dielectric constant of 4.4 (εr1, lower segment), 2.1 (εr2, middle segment) and 9.8 (εr3,upper segment). Here with this combination highest bandwidth and gain has been achieved. Similarly for the four elements four segment q-CDRA has been analyzed in Table 4. Due to fabrication complication up to three segments it has been fabricated and given general name as multi-element multi-segment q-CDRA (MEMS q-CDRA).

Table 3:

Antenna performance with layer arrangement of four elements MEMS q-CDRA (For three layers), effective height (h_eff)=13 mm.

Lower Segment (I)		Middle Segment (II)		Upper Segment (III)		Operating Bandwidth (GHz)	Resonant Frequency (fr) GHz	% Bandwidth	Gain at Resonant Frequency (dBi)
εr1	h1(mm)	εr2	h2(mm)	εr3	h3 (mm)
4.4	3.0	2.1	5.0	9.8	5.0	5.1–13.9	6.6	128.8	7.6
4.4	3.0	9.8	5.0	2.1	5.0	5.6–11.8	7.5	82.66	5.4
9.8	5.0	2.1	5.0	4.4	3.0	5.4–10.5	6.0	85.0	5.25
9.8	5.0	4.4	3.0	2.1	5.0	5.8–11.2	7.9	68.35	7.5
2.1	5.0	4.4	3.0	9.8	5.0	6.2–11.8	8.2	68.29	7.4
2.1	5.0	9.8	5.0	4.4	3.0	5.5–10.4	7.3	67.12	6.6
6	4.0	9.8	4.0	2.1	5.0	5.4–11.1	7.2	79.16	4.85
6	4.0	2.1	5.0	9.8	4.0	5.1–13.0	6.1	129.5	4.25
9.8	4.0	2.1	5.0	6	4.0	5.1–9.5	5.7	77.19	4.17
9.8	4.0	6.0	5.0	2.1	4.0	5.4–9.8	7.6	57.23	4.57
9.8	4.0	6.0	4.0	2.1	5.0	5.4–10.0	7.9	57.34	4.60
2.1	5.0	6.0	4.0	9.8	4.0	5.8–11.0	7.9	75.94	5.13

Table 4:

Antenna performance with layer arrangement of four elements MEMS q-CDRA (for four layers), effective height (h_eff)=13 mm.

Segment (I)		Segment (II)		Segment (III)		Segment (IV)		Operating Bandwidth (GHz)	Resonant Frequency (fr) GHz	% Bandwidth	Gain at Resonant Frequency (dBi)
εr1	h1(mm)	εr2	h2(mm)	εr3	h3(mm)	εr4	h4(mm)
6.0	4.0	2.1	3.5	4.4	1.5	9.8	4.0	5.1–12.6	5.9	128.00	5.10
6.0	4.0	2.1	3.5	9.8	4.0	4.4	1.5	5.1–12.3	6.08	119.57	4.97
6.0	4.0	9.8	4.0	4.4	1.5	2.1	3.5	5.7–9.7	6.98	57.30	5.48
9.8	4.0	6.0	4.0	4.4	1.5	2.1	3.5	5.3–9.86	7.7	59.22	5.86
9.8	4.0	4.4	1.5	6.0	4.0	2.1	3.5	5.2–9.3	7.1	57.74	5.34
9.8	4.0	2.1	3.5	4.4	1.5	6.0	4.0	5.4–10.78	7.4	72.70	5.56
2.1	3.5	6.0	4.0	4.4	1.5	9.8	4.0	5.5–10.6	7.7	66.23	5.87
2.1	3.5	4.4	1.5	6.0	4.0	9.8	4.0	5.7–11.6	8.1	72.83	6.35
2.1	3.5	9.8	4.0	4.4	1.5	6.0	4.0	5.8–12.76	8.3	83.85	6.54
4.4	1.5	6	4	2.1	3.5	9.8	4	5.6–13.29	8.0	96.12	6.18
4.4	1.5	2.1	3.5	6.0	4.0	9.8	4.0	5.7–13.1	8.1	91.35	6.27
4.4	1.5	9.8	4	2.1	3.5	6	4	5.4–12.3	7.25	95.17	5.50

3.3 MEMS q-CDRA (Four Element Three Segment q-CDRA)

From the above guidelines, three segments q-CDRA has fair antenna performance with manageable fabrication problem. The four elements with three-segment q-CDRA has been given general name of MEMS q-CDRA. The schematic view and fabricated prototype of the proposed antenna is shown in Figure 5(a) and 5(b) respectively. The ground plane has perfect electric conductor (PEC) with dielectric constant (εr) of 1. It has zero dielectric tangent loss (tan δ=0) with relative permeability (μr) of 1. The ground plane should be high conductive material so that it can act as perfect reflector, as the PEC has very high bulk conductivity (approx. 1e+030 Siemens/m). The thickness of ground plane should be as enough to fit the SMA connector, because the thickness doesn’t have any impact on antenna performance. Here the thickness of ground plane has been chosen 3 mm. The probe height has been optimized for minimum reflection coefficient though extensive simulations and found to be 9.2 mm from the bottom of the ground plane. The height of the layers has been optimized through extensive simulation for minimum reflection coefficient. The variation of layer thickness and dielectric constant with position of layer has been analyzed, and shown in Tables 5–7 for minimum reflection coefficient. Table 5, gives analysis for middle segment when upper and lower segment kept constant. Similarly, Tables 6 and 7 gives analysis lower and upper segment respectively, while remaining two kept constant. The dielectric constant of 2.1 (Teflon), 4.4 (Epoxy FR4) and 6.0 (k−6) has been taken due to low dielectric constant, which is also commercially available. The height of segment has been varied 1 mm to 5 mm and its performance has been observed. The overall antenna dimension has to keep constant, so that thickness of the layer has been varied up to 5 mm only. The desired dimensions of the proposed antenna have been achieved for the best antenna performance as follows: the lower segment height (hlower=3mm), middle segment height (hmiddle=5mm) and upper segment height (hupper=5mm). The size of ground plane (50 mm×50 mm×3 mm), effective height (heff=13mm) and radius (a=4 mm) of the proposed DRA has been kept same as four elements q-CDRA [19] and DS q-CDRA [20]. Optimization of ground plane has been accomplished through Ansoft HFSS simulation software. The dimension of the ground plane has been acquired for minimum reflection coefficient through parametric analysis. The ground plane works as like infinite ground plane for the proposed antenna due to size of the MEMS q-CDRA, which is very less as compare to the ground plane dimension. The ground plane acts as perfect reflector, which is able to reduce back lobe. The segments of the DRA have been fixed through adhesive material (ELFY), which has very less effect on antenna performance.

Figure 5:

(a) Geometry and (b) Fabricated structure of four elements three segment q-CDRA.

Table 5:

Middle segment thickness variation of MEMS q-CDRA [hlower= heff−hmiddle−hupper, hupper= 5mm, εr,upper= 9.8 and, εr,lower= 4.4].

	εr,middle = 2.1		εr,middle = 4.4		εr,middle = 6.0
hmiddle(mm)	% B.W	fr(GHz)	% B.W	fr(GHz)	% B.W	fr(GHz)
1	63.7	6.3	46.3	8.1	37.6	8.5
2	88.0	6.6	52.4	7.7	41.5	8.3
3	95.4	6.9	57.7	7.6	48.4	8.2
4	115.6	7.35	81.8	7.3	56.7	7.9
5	128.8	6.6	96.0	6.9	57.2	7.6

Table 6:

Lower segment thickness variation of MEMS q-CDRA [hmiddle= heff−hlower−hupper, hupper= 5mm, εr,upper= 9.8 and, εr,middle= 2.1].

	εr,lower = 4.4		εr,lower = 6.0		εr,lower = 2.1
hlower(mm)	% B.W	fr(GHz)	% B.W	fr(GHz)	% B.W	fr(GHz)
1	55.7	6.3	78.4	8.3	89.3	6.7
2	93.6	6.9	67.5	8.1	65.7	6.9
3	128.8	6.6	93.7	7.6	92.4	7.6
4	113.4	7.9	81.5	6.4	78.3	8.2
5	97.3	8.4	98.3	6.2	67.4	8.5

Table 7:

Upper segment thickness variation of MEMS q-CDRA [hmiddle=heff−hlower−hupper, hlower=3mm(constant), εr,lower=4.4 and, εr,middle= 2.1].

	εr,upper = 2.1		εr,upper = 6.0		εr,upper = 9.8
hupper(mm)	% B.W	fr(GHz)	% B.W	fr(GHz)	% B.W	fr(GHz)
1	55.4	9.6	79.2	9.1	82.7	8.9
2	68.9	9.3	77.1	8.5	77.5	8.4
3	56.2	9.2	69.2	8.1	68.3	7.9
4	59.8	8.7	83.6	7.8	89.4	7.8
5	83.5	8.3	103.5	7.7	128.8	6.6

4 Results and discussion

The input characteristics of the proposed MEMS q-CDRA have been investigated through simulation (Ansoft HFSS software) and compared with measured data. The proposed antenna input parameter has been measured through Vector Network Analyzer (Anritsu MS2038C VNA). The far field patterns have been simulated and compared with measured data. The far field parameter of the proposed antenna has been measured inside anechoic chamber size 7×5×3 m. For the gain measurement, three antenna method has been used [24].

The |S₁₁| versus frequency curves of the proposed MEMS q-CDRA has been investigated using simulation and compared with measured data, as shown in Figure 6. The operating bandwidth of 5.0 GHz to 13.7 GHz has been observed for |S₁₁|≤−10 dB through measurement, while through simulation 5.2 GHz to 13.9 GHz. The measured resonant frequency and percentage bandwidth have been achieved 6.5 GHz and 133.8 % respectively. The extracted experimental and simulated operating bandwidth, resonant frequency and % bandwidth have been tabulated in Table 8. The proposed MEMS q-CDRA provides wide bandwidth (133.8 %), which is due to more number of segment participating in radiation and it covers complete 5.0 GHz WiMAX and WLAN band for practical application. Slightly mismatch has been observed between the measured and simulated resonant frequency which may be due to misalignment of the segment during fabrication. The comparison of the proposed antenna has been done with the other similar type of published results and shown in Table 8. The proposed antenna performance has been compared with previous published structure and found better performance with other published structure. In Table 8 bandwidth enhancement can be observed through multi-segment approach. Through four elements q-CDRA and four element DS q-CDRA 58.15 % and 85.13 % bandwidth have been achieved, while through MEMS 133.8 %. From Table 8, it can be observe that without changing the effective radiation area/volume bandwidth can be enhanced.

Figure 6:

Comparison of measured and simulated |S₁₁|vs. frequency curves of proposed MEMS q-CDRA.

The simulated and measured input impedance curves of the proposed antenna have been shown in Figure 7. The real (R_in) and imaginary (X_in) part of input impedance has been observed in frequency range of 4.0 GHz to 14.0 GHz. At the resonant frequency the real value should be 50 Ω and imaginary value should be 0 Ω, which results maximum power transfer at that frequency. The simulated and measured imaginary part/reactance (X_in) have been -j0.1 and -j0.5 observed respectively at the resonant frequency of 6.5 GHz and 6.6 GHz respectively. It can be depicted that the value of the simulated and measured input resistance (R_in) at the resonant frequency is 50.25 Ω and 51.50 Ω respectively. The measured input resistance value of the proposed MEMS q-CDRA has close agreement with the simulated value, which also shows good impedance match with 50 Ω coaxial probe feed.

Figure 7:

Input impedance vs. frequency curve of proposed MEMS q-CDRA.

The near field (E-field and H-field) distributions of the proposed MEMS q-CDRA have been observed through Ansoft HFSS simulation software at its resonant frequency. The distributions of E-field and H-fields of proposed MEMS q-CDRA have been shown in Figure 8(a) and 8(b) respectively. It can be analyzed that the field distribution reveals TM_01δ – like mode as dominant mode in the proposed antenna. The resonant frequency has been occurred near to 6.5 GHz, where exactly validates the dominant mode resonance in proposed MEMS q-CDRA. It can be also observed that electric fields components face their counter vectors in XY plane which creates no radiation along the broadside direction. The orientation of electric fields shows along z-axis polarization which leads to a vertically polarized radiation antenna and its radiate like a quarter wave magnetic monopole patterns surround the structure [14].

Figure 8:

(a) E-field and (b) H-field distribution in proposed MEMS q-CDRA.

The far field patterns of the proposed MEMS q-CDRA have been studied at three different frequencies (5.5 GHz, 6.5 GHz and 9.0 GHz) through the simulation and compared with measurement. The measured and simulated radiation patterns of the proposed q-CDRA at the 5.5 GHz, 6.5 GHz and 9.0 GHz have been shown in Figures 9–11 respectively. It can be verifed that the proposed q-CDRA radiate like monopole radiation pattern at all three frequencies. In the E-plane (YZ-plane and ZX-plane) it shows null at the broadside direction (θ=0°) due to TM_01δ mode. The maximum radiation for E-plane has been observed along 60° with −15 dB and minimum value −65 dB at same angle, means relatively −50 dB difference between co-pole and cross-pole radiation.The measured half power beamwidth of the proposed antenna has been observed for E-plane as 32° for YZ-plane and 44° for ZX-plane at resonant frequency 6.5 GHz. It is in conformity with the counteracting E-field distributions within the DR elements of the proposed antenna. Also the radiation pattern of the proposed antenna has omnidirectional pattern in H-plane (XY-plane).

Figure 9:

Radiation patterns of proposed MEMS q-CDRA (a) in XY plane (b) in YZ plane (c) in ZX plane at frequency 5.5 GHz.

Figure 10:

Radiation patterns of proposed MEMS q-CDRA (a) in XY plane (b) in YZ plane (c) in ZX plane at resonant frequency 6.5 GHz.

Figure 11:

Radiation patterns of proposed MEMS q-CDRA (a) in XY plane (b) in YZ plane (c) in ZX plane at frequency 9.0 GHz.

The simulated and measured gain versus frequency curves of the proposed q-CDRA has been shown in Figure 12. It can be depicted that the measured gain 6.65 dBi at 10.5 GHz and 6.0 dBi at resonant frequency 6.5 GHz. The measurement of gain has been performed at an angle 60° in azimuth E-plane, because it has maximum radiation in this direction. The difference between measured and simulated gain has been observed at higher frequency due to fabrication error of the proposed antenna. Fabrication error can be misalignment between the segmented part and imperfact contact between the DRA and ground plane. Due to these imperfections air gap can be introduced, which results can difference in effective dielectric constant. The measured gain of the proposed antenna has been observed minimum of 4.5 dBi through out the operating frequency band. The gain of proposed antenna has been improved compare to four elements q-CDRA [19] and four element dual segment (DS) q-CDRA [20]. In four element DS q-CDRA, only two segment has been performed and in four element q-CDRA without segment. The improvement in the gain has been occurred due to multi-segment approach with proper placing of the different material segments. For lower segment dielectric constant 4.4 (Epoxy FR4), middle segment dielectric constant 2.1 (Teflon) and upper segment dielctric constant 9.8 (Alumina) material have been used. The gain of the proposed q-CDRA has been observed nearly constant in the entire operating bandwidth. The value of simulated, peak directivity and radiation efficiency at the resonant frequency of the proposed MEMS q-CDRA has been found 8.10 dB and 98 % respectively. The radiation performance of the proposed antenna has been compared with four element q-CDRA and four element DS q-CDRA in Table 9. It explain gain, directivity and radiation efficincy comparision. The peak directivity will be always more than the gain of the antenna. At the resonant frequency simulated gain is 6.6 dBi and the peak directivity 8.10 dB. The maximum measured gain of the four element q-CDRA, four elements q-CDRA and MEMS q-CDRA have been observed 4.55 dBi, 4.85 dBi and 6.65 dBi in operating frequency band. The gain enhancement has been observed due to multi-segment approach applied on the four elements q-CDRA. The analysis for maximum gain at resonant frequency, maximum gain achieved in entire operating bandwidth, directivity and radiation efficiency have been shown in Table 9. It can be observed that MEMS q-CDRA has better performance compare to other q-CDRAs.

Figure 12:

Gain vs. frequency curve for proposed MEMS q-CDRA compared with four elements q-CDRA [19] and four elements DS q-CDRA [20].

5 Conclusion

A novel multi-element multi-segment quarter cylindrical DRA (MEMS q-CDRA) has been designed and fabricated. The MEMS q-CDRA provides wider bandwidth (~ 133.8 %) with complete covering of 5.0 GHz WiMAX and WLAN band. It has uniform monopole type radiation pattern over the complete operating bandwidth. The measured maximum gain of the proposed MEMS q-CDRA has been observed 6.65 dBi at 10.5 GHz, which shows gain improvement compare to four element q-CDRA [19] and DS q-CDRA [20]. Through the imposing of multi-element and multi-segment approach in the basic shape, bandwidth as well as gain can be improved satisfactory. The designed MEMS q-CDRA has found a suitable application in WiMAX and WLAN band.