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Mg-Nd-Cd ferrite as substrate for X-band microstrip patch antenna
Journal Pre-proofs Mg-Nd-Cd Ferrite as Substrate for X-Band Microstrip Patch Antenna S.R. Bhongale PII: DOI: Reference:
S0304-8853(19)31638-5 https://doi.org/10.1016/j.jmmm.2019.165918 MAGMA 165918
To appear in:
Journal of Magnetism and Magnetic Materials
Received Date: Revised Date: Accepted Date:
9 May 2019 16 August 2019 28 September 2019
Please cite this article as: S.R. Bhongale, Mg-Nd-Cd Ferrite as Substrate for X-Band Microstrip Patch Antenna, Journal of Magnetism and Magnetic Materials (2019), doi: https://doi.org/10.1016/j.jmmm.2019.165918
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© 2019 Published by Elsevier B.V.
Mg-Nd-Cd Ferrite as Substrate for X-Band Microstrip Patch Antenna S.R. Bhongale Department of Physics, Yashavantrao Chavan Institute of Science, Satara - 415001(MS) India.
Corresponding author: S.R. Bhongale ([email protected]) (+919850609352) Abstract The magneto-dielectric Mg-Nd-Cd spinel ferrites with chemical formula MgxCd1xNd0.03Fe1.97O4
(x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) was synthesized by oxalate co-
precipitation method under microwave sintering. The electromagnetic input parameters of these ferrites required for design of antennas were investigated in the X-band range. The miniaturization factor found to be highest for composition x = 0.4. The lower dielectric losses and magnetic losses for all compositions of ferrite material were useful for miniaturization of antenna. The patches of silver material were printed on fabricated substrates by using screen printing technique. The performance of return loss, % bandwidth and VSWR indicates that Mg-Nd-Cd ferrite substrates with compositions x = 0.2, 0.8 will have a strength for application as substrates of MPA in X-band microwave communication. Keywords: Mg-Nd-Cd ferrite, Ferrites substrate, Microstrip antennas, Return loss. 1. Introduction The microstrip patch antennas (MPA) in X-band range are prominently used for satellite communication, wireless computer networks and radar. The MPA has natural advantages of miniature size, conformal to any surface, planer structure and low cost [1][2]. The size reduction is a major issue of research in communication field. The miniaturization of MPA can be achieved by using advanced techniques such as geometry
modification, use of substrates with high permittivity materials, etc. However, use of substrates with high permittivity materials reduces its characteristic impedance which leads to mismatching of impedance and resulting in poor efficiency with degradation in antenna performance [3]. The magneto-dielectric materials have the potential to reduce antenna size with increase in bandwidth without degradation of performance [4]-[6]. The spinel ferrite is one of such novel magneto-dielectric materials. Recently, the rapid progress in preparation techniques can be help to synthesize fine spinel ferrites at nano scale. These are most useful materials for many applications due to its numerous manufacturing advantages, such as low production cost and sintering temperature [7]-[8]. The properties of ferrite are very responsive to the cation distribution which depends on the methods of synthesis and doping. The suitable selection of ferrites, doping impurities and synthesis techniques plays an important role to achieve required input electromagnetic parameters of ferrite material to be used as MPA substrate. The magnesium ferrite was one of the important spinal ferrite used in microwave devices, because of its high saturation magnetization, low dielectric loss and magnetic loss [9]. Karche et al. reported that the permeability of Mg-Cd ferrite were increases with the grain size [10]. The use of microwave sintering instead of conventional sintering increases the grain size of ferrites [11]. The substitution of Nd3+ decreases dielectric loss of ferrite [12]. The use of Nd3+substituted Mg-Cd spinel ferrite under microwave sintering as substrate for microstrip patch antenna was still not reported in the literature. Therefore by taking into account various aspects related to Mg- ferrite, effect of Nd3+ substitution and use of microwave sintering, we communicate the performance of simulated and measured return loss (RL), voltage standing wave ratio (VSWR), radiation pattern and gain of fabricated antennas on the Nd3+ substituted Mg-Cd ferrites synthesize under microwave sintering in the present investigation.
Experimental 2.1 Synthesis and characterization Mg-Nd-Cd ferrite The Mg-Nd-Cd ferrite with chemical formula MgxCd1-xNd0.03Fe1.97O4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) was synthesized by the oxalate co-precipitation method under microwave sintering technique. The sulphates (AR grade, Thomas Baker made) such as MgSO4.7H2O (purity 99.5%), 3CdSO4.8H2O (purity 98%), Nd2(SO4)38H2O (purity 98%) and (FeSO4.7H2O, (purity 99.5%) were used as initial precursor. These precursors were dissolved in 500 ml double distilled water in desired stoichiometric ratio with continues magnetic starring. The concentrated sulphuric acid was slowly added to retain 4.8 pH of solution [13]. Thereafter ammonium oxalate solution was slowly added to obtain whole precipitation [14]. This precipitation is mixture of metal oxalates and it contains few impurities of sulphate ions. Therefore the precipitate was washed with double distilled water using Whatman filter paper no.41until removal of sulphate ions. The complete removal of sulphate ions was confirmed by barium chloride test. Thereafter the precipitate was dried out and presintered in microwave oven operated at the 40% wattage for 10 minutes. The presintered sample was crushed in an agate mortar by using AR grade acetone as base and finally sintered at optimized 70% watt for 10 minutes. The synthesized sample powder was characterized by using X-ray diffraction (XRD) and Fourier transforms infrared (FTIR) technique, whereas morphological study was done by using Scanning electron microscope (SEM) of the ferrite. 2.2. Determination of Input Dielectric Parameters of Substrate The input dielectric parameters such as permittivity (εr), dielectric loss tangent (tanδe), permeability (µr) and magnetic loss tangent (tanδm) of substrate required for deign of antenna were measured by material measurement software 80571E from Agilent [15- 16] based on Nicholson-Ross-Weir (NRW) method [17-18]. In this method, it is necessary to
calculate reflection and transmission parameters from the scattering parameters (S11 and S21). The scattering parameters S11 and S21 in terms of transmission coefficient (T) and reflection coefficient (г) can be written as, S11
Γ(1 T 2 ) 1 Γ 2T 2
------ (1)
S21
T(1 Γ 2 ) 1 Γ 2T 2
------ (2)
The reflection coefficient can be given by Eq. (3.7) Γ X X2 1
------ (3)
where X is, S2 S2 1 X 11 21 2S 11
------ (4)
The transmission coefficient can be calculated by using following equation T
S S Γ 11 21 1 - (S S )Γ 11 21
------ (5)
Therefore, the permeability of the material under test is given by Eq. (6) μr
------ (6)
1 Γ 1 1 Λ(1 - Γ) 2 λ λ2 0 c
where Λ is calculated by Eq. (7) 2 ε μ 1 1 1 1 r r ln λ λ T 2 π L Λ2 0 c
------ (7)
and the permittivity of the material is given by Eq. (8) εr
λ2 0 μ r
1 - ( 1 ln 1 ) 2 2πL T λ c
2
where, λ0 = free space wavelength.
------ (8)
λc = cutoff wavelength. The permittivity and permeability can be directly calculated from reflection coefficients (г) and transmission coefficients (T) using the formulae by NRW method. The synthesized sample powder was milled and pressed under 5 tons cm-2 into rectangular pellets having dimensions suitable for WR-90 waveguide. The pellets were sintered for 1h at 150°C. The pellets were used for measuring dielectric parameters on VNA. Thus the variation of εr, tanδe, µr and tanδm as a function of frequency were directly measured [19]. 2.2 Design of antennas: The design of antennas was explained in three steps. First step was to choose the operating frequency (fr) at which the microstrip patch antenna to be designed. In present investigation, the proposed microstrip patch antenna was designed at operating frequency 10.5 GHz. The second step was selection of substrate material with required values of input design parameters such as permittivity (εr), dielectric loss tangent (tanδe), permeability (µr) and magnetic loss tangent (tanδm) to miniaturize size of antenna with increased performance. The use of magneto-dielectric material instead of pure dielectric material may satisfy such conditions. Therefore, in present work, Mg-Nd-Cd ferrite magneto-dielectric materials were used as substrates. The third step is to keep suitable height (h) of substrate is to avoid more fringing field at patch periphery. The height (h) of substrate was optimized to control fringing field at patch periphery [20] and it was kept at 2 mm in this investigation. 2.3 Determination of patch dimensions: The geometry of the rectangular patch on magneto-dielectric material was depends on the permittivity and permeability of the material [2]. The length of rectangular
microstrip patch antenna at operating frequency for magneto-dielectric substrates is given by Eq. 1[21], L
c 2f r ε r μ r
------- (1)
Where, c = free space light velocity, fr = resonant frequency, εr and µr = permittivity and permeability of the Mg-Nd-Cd ferrite substrate respectively. The factor
ε r μ r was called as miniaturization factor. It was due to loading of
magneto-dielectric substrate. In microstrip patch antenna, fringing field at the periphery must be coming into picture. Due to this the permittivity and permeability of substrate material was changed into effective permittivity (εreff) and effective permeability (μreff). Therefore small extension of length is observed in the physical length of antenna. The effective length Leff of the patch is calculated by Eq. (2), Leff
2fr
c ε reffμ reff
------- (2)
Using the value permittivity (εr) and permeability (µr) of the substrate materials at resonant frequency (10.5GHz), length (L) of patch was determined, whereas width (W) of patch was determined by simulation with optimization for minimum return loss of antenna at designed resonant frequency. The dimensions of the ground plane were kept approximately 6h greater than patch dimensions all around the periphery [20]. 2.4 Simulation and fabrication of antennas: The variations of input parameters of Mg-Cd-Nd ferrites such as εr, µr, tanδe and tanδm as a function frequency have been discussed in results section and their values at operating frequency 10.5 GHz used for design of antennas were presented in the TABLE I. The microstrip patch antennas on the various compositions of Mg-Cd-Nd ferrite substrates were designed by using Ansoft Desiner SV2.2 software [22]. The coaxial feed was used for excitation of antenna. The feed points were optimized carefully for 50 ohms impedance
matching with input impedance. The geometry of designed patch antennas with coax feed by simulation is as shown in the Fig.1. The distances of feed point from edges of patch Lg and Wg are determined from the geometry of patch antennas. The L, W, Lg and Wg antennas are presented in TABLE I. The designed antennas were simulated to study the antenna parameters such as return loss, % 10dB bandwidth, voltage standing wave ratio (VSWR), radiation pattern, gain and beamwidth. Thereafter substrates of antennas were fabricated by using Mg-Cd-Nd ferrite by pressing in die of diameter 2.25cm. The schematic layout of ground plane and patch for the fabrication of screen used for printing is as shown in the Fig.2. The patches of conducting silver metal were printed on substrate using screen printing technique. The SMA connector was connected at the proper feed point. The top and bottom view of fabricated antennas on Mg-Nd-Cd ferrite substrates with SMA connector are presented in the Fig.3. Return loss (RL), %10dB bandwidth (BW) and voltage standing wave ratio (VSWR) of these fabricated antennas were measured by single port calibration method on VNA (Vector Network analyzers, model ROHDE & SCHWARZ ZVL). 3
Results and discussion
3.1 Characteristics of Mg-Nd-Cd ferrites The detailed study of X-ray and FTIR characteristics, morphological study are explained elsewhere [23]. The typical X-ray diffractogram, FTIR absorption spectra and SEM microphotograph for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite are presented in the Fig.1, 2 and 3 respectively. The presence of planes (220), (311), (400), (422), (511/333), (440) at angels 29.98°, 35.27°, 42.95°, 53.51°, 56.67°, 62.40° in the typical difractogram in Fig. 1 confirms the formation of cubic spinal structure of ferrites under investigation. The intensity peaks represented by star (*) indicates formation of ortho ferrite phases due to substitution of neodymium. The appearance of two major absorption bands at wave
numbers 427.74 cm-1 and 577.27 cm-1 in Fig.2 are the characteristics absorption bands of spinal ferrite suggested by Waldron [24]. From Fig. 3, it is seen the average grain size of ferrite found to be 1.37 µm, indicating formation of grains in the micrometer range. 3.2 Input Antenna Parameters of Substrate: The permittivity (εr), dielectric loss tangent (tanδe), permeability (µr) and magnetic loss tangent (tanδm) as function of frequency for all compositions of Mg-Nd-Cd ferrites were determined by using NRW method. The typical variations of εr and µr, tanδe and tanδm with frequency for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite are presented in Fig.7 and Fig.9 respectively. From Fig.7, it is observed that the trend of permittivity of ferrite dose not follows dispersion property, but increases with frequency. This can be is attributed to the significant improvement of polarization (dielectric constant) of ferrite [25]. The variation of permeability with frequency shows usual frequency dispersion behavior. From Fig. 8, it is seen that tanδe is decreases with frequency. Whereas tanδm is initially increases, reaches maximum value at 10.5 GHz frequency and then decreases with increase of frequency. 3.3 Miniaturization of Antenna: The miniaturization factor (n) for antennas on all ferrites under investigation is determined by using eqn ε r μ r at various frequencies and is presented in Fig.9. From this figure, it is seen that the miniaturization factor for antennas Mg-Nd-Cd ferrites with x = 0.4 is higher than that for all other ferrites. The miniaturization factor for Mg-Nd-Cd ferrite remains nearly constant with increase in frequency. This may be due to small variations in permittivity and permeability with frequency. For higher miniaturization factor, the antenna size becomes compact which results in more difficult feeding and input impedance becomes more sensitive to the feed location [26]. Therefore more care has been taken to find feed locations for excitation of antenna in this investigation.
3.4 Analysis of antenna output parameters: The simulated and measured return loss (RL) as a function of frequency for microstrip patch antennas on Mg-Nd-Cd ferrite substrates are shown in Fig.10. From Fig.10, observed simulated and measured return loss, 10 dB % return loss bandwidth at operating frequency of all antennas are noticed in TABLE II. The very small changes in simulated and measured operating frequency from designed frequency (10.5 GHz) are observed. The simulated RL is lower than measured RL for all antennas indicating poor impedance matching for fabricated antennas. This may be due to errors in connection of SMA connector at proper feed point. However, for antenna on Mg-Nd-Cd ferrite with x = 0.2, the measured RL is nearly equal to the simulated RL indicating better impedance matching to this fabricated antenna as compared to others. It is seen that the simulated higher cutoff frequencies for all antennas on Mg-Nd-Cd ferrites are beyond the range of measured frequency. The measured bandwidths for all antennas on Mg-Nd-Cd ferrite are in the range of 10.24 to 31.65. The highest bandwidth is observed for antenna on Mg-NdCd ferrite substrate with x = 0.8. Similar improved bandwidth is observed for microstrip patch antenna on Ni-Zn ferrite [27]. The simulated and measured VSWR as function of frequency for all antennas under investigation are presented in Fig.11. The minimum VSWR at operating frequency are noticed in TABLE II. It is found that the simulated and measured VSWR is the in the range of 1.01 to 1.33 and 1.12 to 1.70. The measured VSWR is higher than simulated VSWR. This may be due to mismatching of SMA connection and simulated feed location. The simulated and measured VSWR for antennas on Mg-Nd-Cd ferrites substrate x = 0.2, 0.8 and x = 0.4, 1 respectively are lowest. It indicates the better optimization of impedance matching at feed location for these antennas. The magnitudes of return loss, % bandwidth and VSWR for the microstrip patch
antennas on Mg-Nd-Cd ferrite substrates with composition x = 0.2, 0.8 have better performance as compared with other compositions. Therefore the compositions x = 0.2, 0.8 of Mg-Nd-Cd ferrite have a strength for application as substrates of MPA in microwave communication. The 2D polar radiation patterns for all antennas under investigation are simulated at the operating frequency. The typical radiation pattern of antenna on Mg-Nd-Cd ferrite (x = 1) is shown in Fig.12. The simulated maximum gain and beamwidth of all antennas are measured and noticed in the TABLE II. The gains of all antennas are low; it may be due to the higher losses particularly magnetic losses of all Mg-Cd- Nd ferrite. The variation of the gain of antennas on Mg-Nd-Cd ferrite substrate as function of magnetic loss tangent (tanδm) is presented in the Fig.13. From this figures, it is clear that gain of antennas as usual decreases with increase in magnetic loss tangent. A. R. Albino et al. [28] observed similar result for ferrite substrate. Form TABLE II, it is observed that the beamwidth is in range of 70° to 120° for antennas on Mg-Nd-Cd ferrites. The overall increased beamwidths are observed for antennas on Mg-Nd-Cd ferrites as compared to the reported beamwidths for antennas on Mg-Cd ferrites [29]. 4
Conclusion Nanocrystalline simulated and measured operating frequency of microstrip patch
antennas on Mg-Nd-Cd ferrites is close to designed frequency. The highest bandwidth is observed for antenna on Mg-Nd-Cd ferrite substrate with x = 0.8. The gains of antennas are decreases with increase in magnetic loss tangent. The overall increased beamwidth is observed for antennas on Mg-Nd-Cd ferrites as compared to that for antennas on Mg-Cd ferrites. The performance of return loss and % bandwidth and VSWR indicates that MgNd-Cd ferrite substrate with x = 0.2, 0.8 have a strength for application as substrates of MPA in microwave communication.
Acknowledgement The authors would like to thank the Rayat Shikshan Sanstha, Satara, Department of Physics, Yashvantarao Chavan Institute of Science, Satara, References [1] K. Carver, J.W. Mink, Microstrip antenna technology, IEEE Trans. Antennas Propag. 29, (1981), 2-24. [2] R. Garg. P. Bhartia, I. Bahl, and A. Ittipiboon, Microstrip Antennas Design Handbook (London: Artech House 2001) 253. [3] H. Mosallaei and K. Sarabandi, Magneto-Dielectrics in electromag-netics: Concept and applications, IEEE Trans. Antennas Propag., 52 (2004)1558 –1567. [4] S. Bae, Y. K. Kong, and A. Lyle, Effect of Ni-Zn ferrite on bandwidth and radiation efficiency of embedded antenna for mobile phone, J. Appl. Phys., 103(2008) 07E929. [5] K. Buell. H. Mossallaei, and K. Sarabandi, A substrate for small patch antennas providing tunable miniaturization factors, IEEE Trans. Mi-crowave Theory Tech., 54 (2006) 135–146. [6] L. B. Kong, Z. W. Li, G. Q. Lin, and Y. B. Gan, Ni-Zn ferrites composites with almost equal values of permeability and permittivity for low-frequency antenna design, IEEE Trans. Magn., 43 (2007) 6–10. [7] A. Thakur, A. Chevalier, J.-L. Mattei, and P. Queffélec, Low-loss spinel nano-ferrite with matching permeability and permittivity in the ultra high frequency range, J. Appl. Phys., 10 (2010) 014301. [8] D. H. Souriou, J. L. Mattei, A. Chevalier, and P. Queffélec, “Influential parameters on magnetic properties of nickel zinc ferrites for antenna miniaturisation,” J. Appl. Phys., 107, (2010) 09A518.
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Fig.1. Designed microstrip patch antennas by simulation on Mg-Nd-Cd ferrite substrates.
Fig.2. Schematic layout for fabrication of screen.
Fig.3. Fabricated microstrip patch antennas on Mg-Nd-Cd ferrite substrate
Fig. 4. X-ray difractogram for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.5. FTIR spectra for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.6. SEM microphotograph for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.7. Variation of permittivity (εr) and permeability (µr) with frequency for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.8. Variation of dielectric loss tangent (tanδe) and magnetic loss tangent (tanδm) for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.9. Miniaturization factors at various frequencies for antenna on Mg-Nd-Cd ferrites.
Fig.10. Variation of simulated and measured return loss (RL) with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates.
Fig.11. Variation of simulated and measured VSWR with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates.
Fig.12. Radiation pattern on Mg-Nd-Cd (x = 0) ferrite substrate.
Fig.13. Variation of gain with magnetic loss tangent. Figure Caption Fig.1. Designed microstrip patch antennas by simulation on Mg-Nd-Cd ferrite substrates. Fig.2. Schematic layout for fabrication of screen. Fig.3. Fabricated microstrip patch antennas on Mg-Nd-Cd ferrite substrate Fig.4. X-ray difractogram for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.5. FTIR spectra for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.6. SEM microphotograph for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.7. Variation of permittivity (εr) and permeability (µr) with frequency for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.8. Variation of dielectric loss tangent (tanδe) and magnetic loss tangent (tanδm) for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.9. Miniaturization factors at various frequencies for antenna on Mg-Nd-Cd ferrites. Fig.10. Variation of simulated and measured return loss (RL) with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates. Fig.11. Variation of simulated and measured VSWR with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates. Fig.12. Radiation pattern on Mg-Nd-Cd (x = 0) ferrite substrate. Fig.13. Variation of gain with magnetic loss tangent. [30]
Table 1. Input parameters for design of microstrip patch antenna on
MgxCd1-xNdyFe2-yO4 substrate Mg Content
F (GHz)
ε'
μ'
tanδe
tanδm
Height Length h L (mm) (mm) 2 6.9 2 7.0
0.0 0.2
10.5 10.5
5.75 5.46
1.00 0.97
0.180 0.230
0.054 0.125
0.4
10.5
5.66
1.03
0.014
0.296
2
0.6 0.8 1.0
10.5 10.5 10.5
4.10 4.80 3.18
1.16 1.00 1.29
0.074 0.170 0.200
0.238 0.158 0.098
2 2 2
Width W (mm) 7.1 7.5
Lg mm
Wg mm
1.2 1.2
1.1 1.4
6.2
6.8
1.2
2.2
6.9 6.9 7.2
7.6 7.5 7.6
1.2 1.3 1.6
1.8 1.7 1.6
Table 2. Simulated and measured output parameters of microstrip patch antenna Mg Content 0.0 0.2 0.4 0.6 0.8 1.0
Frequency F (GHz) Simul Meas ated ured 10.53 10.50 10.50 10.67 10.50 10.33 10.58 10.62 10.44 10.74 10.56 9.35
Return loss RL(dB) Simula Measu ted red -30.98 -14.72 -31.20 -29.95 -28.88 -17.91 -21.48 -12.60 -34.74 -11.53 -16.78 -19.16
% 10dB Bandwidth Simul Meas ated ured 28.47 12.08 23.62 10.64 31.65 20.21
VSWR Simu lated 1.05 1.01 1.06 1.17 1.04 1.33
Meas ured 1.70 1.70 1.12 1.58 1.34 1.26
Gain 0.42 0.32 0.24 0.38 0.35 0.46
[31] Highlights 1. The Mg-Nd-Cd ferrite can be used as substrate for microstrip patch antenna. 2. The lower dielectric and magnetic loss tangent of material were useful for miniaturization of antennas. 3. The overall increased beamwidth is observed for antennas on Mg-Nd-Cd ferrites 4. The gain of antennas as usual decreases with increase in magnetic loss tangent.
Beam width 120° 93° 70° 110° 105° 110°
[32] Graphical Abstract The simulated and measured return loss (RL) as a function of frequency for microstrip patch antennas on Mg-Nd-Cd ferrite substrates are shown in figure. The measured RL is nearly equal to the simulated RL for an antenna on Mg-Nd-Cd ferrite with x = 0.2 indicating better impedance matching to this fabricated antenna as compared to others. The highest bandwidth is observed for antenna on Mg-Nd-Cd ferrite substrate with x = 0.8.
Variation of simulated and measured return loss (RL) with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates.
[33]
S0304-8853(19)31638-5 https://doi.org/10.1016/j.jmmm.2019.165918 MAGMA 165918
To appear in:
Journal of Magnetism and Magnetic Materials
Received Date: Revised Date: Accepted Date:
9 May 2019 16 August 2019 28 September 2019
Please cite this article as: S.R. Bhongale, Mg-Nd-Cd Ferrite as Substrate for X-Band Microstrip Patch Antenna, Journal of Magnetism and Magnetic Materials (2019), doi: https://doi.org/10.1016/j.jmmm.2019.165918
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Mg-Nd-Cd Ferrite as Substrate for X-Band Microstrip Patch Antenna S.R. Bhongale Department of Physics, Yashavantrao Chavan Institute of Science, Satara - 415001(MS) India.
Corresponding author: S.R. Bhongale ([email protected]) (+919850609352) Abstract The magneto-dielectric Mg-Nd-Cd spinel ferrites with chemical formula MgxCd1xNd0.03Fe1.97O4
(x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) was synthesized by oxalate co-
precipitation method under microwave sintering. The electromagnetic input parameters of these ferrites required for design of antennas were investigated in the X-band range. The miniaturization factor found to be highest for composition x = 0.4. The lower dielectric losses and magnetic losses for all compositions of ferrite material were useful for miniaturization of antenna. The patches of silver material were printed on fabricated substrates by using screen printing technique. The performance of return loss, % bandwidth and VSWR indicates that Mg-Nd-Cd ferrite substrates with compositions x = 0.2, 0.8 will have a strength for application as substrates of MPA in X-band microwave communication. Keywords: Mg-Nd-Cd ferrite, Ferrites substrate, Microstrip antennas, Return loss. 1. Introduction The microstrip patch antennas (MPA) in X-band range are prominently used for satellite communication, wireless computer networks and radar. The MPA has natural advantages of miniature size, conformal to any surface, planer structure and low cost [1][2]. The size reduction is a major issue of research in communication field. The miniaturization of MPA can be achieved by using advanced techniques such as geometry
modification, use of substrates with high permittivity materials, etc. However, use of substrates with high permittivity materials reduces its characteristic impedance which leads to mismatching of impedance and resulting in poor efficiency with degradation in antenna performance [3]. The magneto-dielectric materials have the potential to reduce antenna size with increase in bandwidth without degradation of performance [4]-[6]. The spinel ferrite is one of such novel magneto-dielectric materials. Recently, the rapid progress in preparation techniques can be help to synthesize fine spinel ferrites at nano scale. These are most useful materials for many applications due to its numerous manufacturing advantages, such as low production cost and sintering temperature [7]-[8]. The properties of ferrite are very responsive to the cation distribution which depends on the methods of synthesis and doping. The suitable selection of ferrites, doping impurities and synthesis techniques plays an important role to achieve required input electromagnetic parameters of ferrite material to be used as MPA substrate. The magnesium ferrite was one of the important spinal ferrite used in microwave devices, because of its high saturation magnetization, low dielectric loss and magnetic loss [9]. Karche et al. reported that the permeability of Mg-Cd ferrite were increases with the grain size [10]. The use of microwave sintering instead of conventional sintering increases the grain size of ferrites [11]. The substitution of Nd3+ decreases dielectric loss of ferrite [12]. The use of Nd3+substituted Mg-Cd spinel ferrite under microwave sintering as substrate for microstrip patch antenna was still not reported in the literature. Therefore by taking into account various aspects related to Mg- ferrite, effect of Nd3+ substitution and use of microwave sintering, we communicate the performance of simulated and measured return loss (RL), voltage standing wave ratio (VSWR), radiation pattern and gain of fabricated antennas on the Nd3+ substituted Mg-Cd ferrites synthesize under microwave sintering in the present investigation.
Experimental 2.1 Synthesis and characterization Mg-Nd-Cd ferrite The Mg-Nd-Cd ferrite with chemical formula MgxCd1-xNd0.03Fe1.97O4 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) was synthesized by the oxalate co-precipitation method under microwave sintering technique. The sulphates (AR grade, Thomas Baker made) such as MgSO4.7H2O (purity 99.5%), 3CdSO4.8H2O (purity 98%), Nd2(SO4)38H2O (purity 98%) and (FeSO4.7H2O, (purity 99.5%) were used as initial precursor. These precursors were dissolved in 500 ml double distilled water in desired stoichiometric ratio with continues magnetic starring. The concentrated sulphuric acid was slowly added to retain 4.8 pH of solution [13]. Thereafter ammonium oxalate solution was slowly added to obtain whole precipitation [14]. This precipitation is mixture of metal oxalates and it contains few impurities of sulphate ions. Therefore the precipitate was washed with double distilled water using Whatman filter paper no.41until removal of sulphate ions. The complete removal of sulphate ions was confirmed by barium chloride test. Thereafter the precipitate was dried out and presintered in microwave oven operated at the 40% wattage for 10 minutes. The presintered sample was crushed in an agate mortar by using AR grade acetone as base and finally sintered at optimized 70% watt for 10 minutes. The synthesized sample powder was characterized by using X-ray diffraction (XRD) and Fourier transforms infrared (FTIR) technique, whereas morphological study was done by using Scanning electron microscope (SEM) of the ferrite. 2.2. Determination of Input Dielectric Parameters of Substrate The input dielectric parameters such as permittivity (εr), dielectric loss tangent (tanδe), permeability (µr) and magnetic loss tangent (tanδm) of substrate required for deign of antenna were measured by material measurement software 80571E from Agilent [15- 16] based on Nicholson-Ross-Weir (NRW) method [17-18]. In this method, it is necessary to
calculate reflection and transmission parameters from the scattering parameters (S11 and S21). The scattering parameters S11 and S21 in terms of transmission coefficient (T) and reflection coefficient (г) can be written as, S11
Γ(1 T 2 ) 1 Γ 2T 2
------ (1)
S21
T(1 Γ 2 ) 1 Γ 2T 2
------ (2)
The reflection coefficient can be given by Eq. (3.7) Γ X X2 1
------ (3)
where X is, S2 S2 1 X 11 21 2S 11
------ (4)
The transmission coefficient can be calculated by using following equation T
S S Γ 11 21 1 - (S S )Γ 11 21
------ (5)
Therefore, the permeability of the material under test is given by Eq. (6) μr
------ (6)
1 Γ 1 1 Λ(1 - Γ) 2 λ λ2 0 c
where Λ is calculated by Eq. (7) 2 ε μ 1 1 1 1 r r ln λ λ T 2 π L Λ2 0 c
------ (7)
and the permittivity of the material is given by Eq. (8) εr
λ2 0 μ r
1 - ( 1 ln 1 ) 2 2πL T λ c
2
where, λ0 = free space wavelength.
------ (8)
λc = cutoff wavelength. The permittivity and permeability can be directly calculated from reflection coefficients (г) and transmission coefficients (T) using the formulae by NRW method. The synthesized sample powder was milled and pressed under 5 tons cm-2 into rectangular pellets having dimensions suitable for WR-90 waveguide. The pellets were sintered for 1h at 150°C. The pellets were used for measuring dielectric parameters on VNA. Thus the variation of εr, tanδe, µr and tanδm as a function of frequency were directly measured [19]. 2.2 Design of antennas: The design of antennas was explained in three steps. First step was to choose the operating frequency (fr) at which the microstrip patch antenna to be designed. In present investigation, the proposed microstrip patch antenna was designed at operating frequency 10.5 GHz. The second step was selection of substrate material with required values of input design parameters such as permittivity (εr), dielectric loss tangent (tanδe), permeability (µr) and magnetic loss tangent (tanδm) to miniaturize size of antenna with increased performance. The use of magneto-dielectric material instead of pure dielectric material may satisfy such conditions. Therefore, in present work, Mg-Nd-Cd ferrite magneto-dielectric materials were used as substrates. The third step is to keep suitable height (h) of substrate is to avoid more fringing field at patch periphery. The height (h) of substrate was optimized to control fringing field at patch periphery [20] and it was kept at 2 mm in this investigation. 2.3 Determination of patch dimensions: The geometry of the rectangular patch on magneto-dielectric material was depends on the permittivity and permeability of the material [2]. The length of rectangular
microstrip patch antenna at operating frequency for magneto-dielectric substrates is given by Eq. 1[21], L
c 2f r ε r μ r
------- (1)
Where, c = free space light velocity, fr = resonant frequency, εr and µr = permittivity and permeability of the Mg-Nd-Cd ferrite substrate respectively. The factor
ε r μ r was called as miniaturization factor. It was due to loading of
magneto-dielectric substrate. In microstrip patch antenna, fringing field at the periphery must be coming into picture. Due to this the permittivity and permeability of substrate material was changed into effective permittivity (εreff) and effective permeability (μreff). Therefore small extension of length is observed in the physical length of antenna. The effective length Leff of the patch is calculated by Eq. (2), Leff
2fr
c ε reffμ reff
------- (2)
Using the value permittivity (εr) and permeability (µr) of the substrate materials at resonant frequency (10.5GHz), length (L) of patch was determined, whereas width (W) of patch was determined by simulation with optimization for minimum return loss of antenna at designed resonant frequency. The dimensions of the ground plane were kept approximately 6h greater than patch dimensions all around the periphery [20]. 2.4 Simulation and fabrication of antennas: The variations of input parameters of Mg-Cd-Nd ferrites such as εr, µr, tanδe and tanδm as a function frequency have been discussed in results section and their values at operating frequency 10.5 GHz used for design of antennas were presented in the TABLE I. The microstrip patch antennas on the various compositions of Mg-Cd-Nd ferrite substrates were designed by using Ansoft Desiner SV2.2 software [22]. The coaxial feed was used for excitation of antenna. The feed points were optimized carefully for 50 ohms impedance
matching with input impedance. The geometry of designed patch antennas with coax feed by simulation is as shown in the Fig.1. The distances of feed point from edges of patch Lg and Wg are determined from the geometry of patch antennas. The L, W, Lg and Wg antennas are presented in TABLE I. The designed antennas were simulated to study the antenna parameters such as return loss, % 10dB bandwidth, voltage standing wave ratio (VSWR), radiation pattern, gain and beamwidth. Thereafter substrates of antennas were fabricated by using Mg-Cd-Nd ferrite by pressing in die of diameter 2.25cm. The schematic layout of ground plane and patch for the fabrication of screen used for printing is as shown in the Fig.2. The patches of conducting silver metal were printed on substrate using screen printing technique. The SMA connector was connected at the proper feed point. The top and bottom view of fabricated antennas on Mg-Nd-Cd ferrite substrates with SMA connector are presented in the Fig.3. Return loss (RL), %10dB bandwidth (BW) and voltage standing wave ratio (VSWR) of these fabricated antennas were measured by single port calibration method on VNA (Vector Network analyzers, model ROHDE & SCHWARZ ZVL). 3
Results and discussion
3.1 Characteristics of Mg-Nd-Cd ferrites The detailed study of X-ray and FTIR characteristics, morphological study are explained elsewhere [23]. The typical X-ray diffractogram, FTIR absorption spectra and SEM microphotograph for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite are presented in the Fig.1, 2 and 3 respectively. The presence of planes (220), (311), (400), (422), (511/333), (440) at angels 29.98°, 35.27°, 42.95°, 53.51°, 56.67°, 62.40° in the typical difractogram in Fig. 1 confirms the formation of cubic spinal structure of ferrites under investigation. The intensity peaks represented by star (*) indicates formation of ortho ferrite phases due to substitution of neodymium. The appearance of two major absorption bands at wave
numbers 427.74 cm-1 and 577.27 cm-1 in Fig.2 are the characteristics absorption bands of spinal ferrite suggested by Waldron [24]. From Fig. 3, it is seen the average grain size of ferrite found to be 1.37 µm, indicating formation of grains in the micrometer range. 3.2 Input Antenna Parameters of Substrate: The permittivity (εr), dielectric loss tangent (tanδe), permeability (µr) and magnetic loss tangent (tanδm) as function of frequency for all compositions of Mg-Nd-Cd ferrites were determined by using NRW method. The typical variations of εr and µr, tanδe and tanδm with frequency for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite are presented in Fig.7 and Fig.9 respectively. From Fig.7, it is observed that the trend of permittivity of ferrite dose not follows dispersion property, but increases with frequency. This can be is attributed to the significant improvement of polarization (dielectric constant) of ferrite [25]. The variation of permeability with frequency shows usual frequency dispersion behavior. From Fig. 8, it is seen that tanδe is decreases with frequency. Whereas tanδm is initially increases, reaches maximum value at 10.5 GHz frequency and then decreases with increase of frequency. 3.3 Miniaturization of Antenna: The miniaturization factor (n) for antennas on all ferrites under investigation is determined by using eqn ε r μ r at various frequencies and is presented in Fig.9. From this figure, it is seen that the miniaturization factor for antennas Mg-Nd-Cd ferrites with x = 0.4 is higher than that for all other ferrites. The miniaturization factor for Mg-Nd-Cd ferrite remains nearly constant with increase in frequency. This may be due to small variations in permittivity and permeability with frequency. For higher miniaturization factor, the antenna size becomes compact which results in more difficult feeding and input impedance becomes more sensitive to the feed location [26]. Therefore more care has been taken to find feed locations for excitation of antenna in this investigation.
3.4 Analysis of antenna output parameters: The simulated and measured return loss (RL) as a function of frequency for microstrip patch antennas on Mg-Nd-Cd ferrite substrates are shown in Fig.10. From Fig.10, observed simulated and measured return loss, 10 dB % return loss bandwidth at operating frequency of all antennas are noticed in TABLE II. The very small changes in simulated and measured operating frequency from designed frequency (10.5 GHz) are observed. The simulated RL is lower than measured RL for all antennas indicating poor impedance matching for fabricated antennas. This may be due to errors in connection of SMA connector at proper feed point. However, for antenna on Mg-Nd-Cd ferrite with x = 0.2, the measured RL is nearly equal to the simulated RL indicating better impedance matching to this fabricated antenna as compared to others. It is seen that the simulated higher cutoff frequencies for all antennas on Mg-Nd-Cd ferrites are beyond the range of measured frequency. The measured bandwidths for all antennas on Mg-Nd-Cd ferrite are in the range of 10.24 to 31.65. The highest bandwidth is observed for antenna on Mg-NdCd ferrite substrate with x = 0.8. Similar improved bandwidth is observed for microstrip patch antenna on Ni-Zn ferrite [27]. The simulated and measured VSWR as function of frequency for all antennas under investigation are presented in Fig.11. The minimum VSWR at operating frequency are noticed in TABLE II. It is found that the simulated and measured VSWR is the in the range of 1.01 to 1.33 and 1.12 to 1.70. The measured VSWR is higher than simulated VSWR. This may be due to mismatching of SMA connection and simulated feed location. The simulated and measured VSWR for antennas on Mg-Nd-Cd ferrites substrate x = 0.2, 0.8 and x = 0.4, 1 respectively are lowest. It indicates the better optimization of impedance matching at feed location for these antennas. The magnitudes of return loss, % bandwidth and VSWR for the microstrip patch
antennas on Mg-Nd-Cd ferrite substrates with composition x = 0.2, 0.8 have better performance as compared with other compositions. Therefore the compositions x = 0.2, 0.8 of Mg-Nd-Cd ferrite have a strength for application as substrates of MPA in microwave communication. The 2D polar radiation patterns for all antennas under investigation are simulated at the operating frequency. The typical radiation pattern of antenna on Mg-Nd-Cd ferrite (x = 1) is shown in Fig.12. The simulated maximum gain and beamwidth of all antennas are measured and noticed in the TABLE II. The gains of all antennas are low; it may be due to the higher losses particularly magnetic losses of all Mg-Cd- Nd ferrite. The variation of the gain of antennas on Mg-Nd-Cd ferrite substrate as function of magnetic loss tangent (tanδm) is presented in the Fig.13. From this figures, it is clear that gain of antennas as usual decreases with increase in magnetic loss tangent. A. R. Albino et al. [28] observed similar result for ferrite substrate. Form TABLE II, it is observed that the beamwidth is in range of 70° to 120° for antennas on Mg-Nd-Cd ferrites. The overall increased beamwidths are observed for antennas on Mg-Nd-Cd ferrites as compared to the reported beamwidths for antennas on Mg-Cd ferrites [29]. 4
Conclusion Nanocrystalline simulated and measured operating frequency of microstrip patch
antennas on Mg-Nd-Cd ferrites is close to designed frequency. The highest bandwidth is observed for antenna on Mg-Nd-Cd ferrite substrate with x = 0.8. The gains of antennas are decreases with increase in magnetic loss tangent. The overall increased beamwidth is observed for antennas on Mg-Nd-Cd ferrites as compared to that for antennas on Mg-Cd ferrites. The performance of return loss and % bandwidth and VSWR indicates that MgNd-Cd ferrite substrate with x = 0.2, 0.8 have a strength for application as substrates of MPA in microwave communication.
Acknowledgement The authors would like to thank the Rayat Shikshan Sanstha, Satara, Department of Physics, Yashvantarao Chavan Institute of Science, Satara, References [1] K. Carver, J.W. Mink, Microstrip antenna technology, IEEE Trans. Antennas Propag. 29, (1981), 2-24. [2] R. Garg. P. Bhartia, I. Bahl, and A. Ittipiboon, Microstrip Antennas Design Handbook (London: Artech House 2001) 253. [3] H. Mosallaei and K. Sarabandi, Magneto-Dielectrics in electromag-netics: Concept and applications, IEEE Trans. Antennas Propag., 52 (2004)1558 –1567. [4] S. Bae, Y. K. Kong, and A. Lyle, Effect of Ni-Zn ferrite on bandwidth and radiation efficiency of embedded antenna for mobile phone, J. Appl. Phys., 103(2008) 07E929. [5] K. Buell. H. Mossallaei, and K. Sarabandi, A substrate for small patch antennas providing tunable miniaturization factors, IEEE Trans. Mi-crowave Theory Tech., 54 (2006) 135–146. [6] L. B. Kong, Z. W. Li, G. Q. Lin, and Y. B. Gan, Ni-Zn ferrites composites with almost equal values of permeability and permittivity for low-frequency antenna design, IEEE Trans. Magn., 43 (2007) 6–10. [7] A. Thakur, A. Chevalier, J.-L. Mattei, and P. Queffélec, Low-loss spinel nano-ferrite with matching permeability and permittivity in the ultra high frequency range, J. Appl. Phys., 10 (2010) 014301. [8] D. H. Souriou, J. L. Mattei, A. Chevalier, and P. Queffélec, “Influential parameters on magnetic properties of nickel zinc ferrites for antenna miniaturisation,” J. Appl. Phys., 107, (2010) 09A518.
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[29] S.R. Bhongale, H. R. Ingavale, T. J. Shinde, P. N. Vasambekar, Performance of Wide Band Cadmium Ferrite Microstrip Patch Antenna in X-Band region, J. Electron. Mater., 47 (2018) 577 - 584.
Fig.1. Designed microstrip patch antennas by simulation on Mg-Nd-Cd ferrite substrates.
Fig.2. Schematic layout for fabrication of screen.
Fig.3. Fabricated microstrip patch antennas on Mg-Nd-Cd ferrite substrate
Fig. 4. X-ray difractogram for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.5. FTIR spectra for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.6. SEM microphotograph for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.7. Variation of permittivity (εr) and permeability (µr) with frequency for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.8. Variation of dielectric loss tangent (tanδe) and magnetic loss tangent (tanδm) for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite.
Fig.9. Miniaturization factors at various frequencies for antenna on Mg-Nd-Cd ferrites.
Fig.10. Variation of simulated and measured return loss (RL) with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates.
Fig.11. Variation of simulated and measured VSWR with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates.
Fig.12. Radiation pattern on Mg-Nd-Cd (x = 0) ferrite substrate.
Fig.13. Variation of gain with magnetic loss tangent. Figure Caption Fig.1. Designed microstrip patch antennas by simulation on Mg-Nd-Cd ferrite substrates. Fig.2. Schematic layout for fabrication of screen. Fig.3. Fabricated microstrip patch antennas on Mg-Nd-Cd ferrite substrate Fig.4. X-ray difractogram for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.5. FTIR spectra for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.6. SEM microphotograph for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.7. Variation of permittivity (εr) and permeability (µr) with frequency for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.8. Variation of dielectric loss tangent (tanδe) and magnetic loss tangent (tanδm) for Mg0.4Cd0.6Nd0.03Fe1.97O4 ferrite. Fig.9. Miniaturization factors at various frequencies for antenna on Mg-Nd-Cd ferrites. Fig.10. Variation of simulated and measured return loss (RL) with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates. Fig.11. Variation of simulated and measured VSWR with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates. Fig.12. Radiation pattern on Mg-Nd-Cd (x = 0) ferrite substrate. Fig.13. Variation of gain with magnetic loss tangent. [30]
Table 1. Input parameters for design of microstrip patch antenna on
MgxCd1-xNdyFe2-yO4 substrate Mg Content
F (GHz)
ε'
μ'
tanδe
tanδm
Height Length h L (mm) (mm) 2 6.9 2 7.0
0.0 0.2
10.5 10.5
5.75 5.46
1.00 0.97
0.180 0.230
0.054 0.125
0.4
10.5
5.66
1.03
0.014
0.296
2
0.6 0.8 1.0
10.5 10.5 10.5
4.10 4.80 3.18
1.16 1.00 1.29
0.074 0.170 0.200
0.238 0.158 0.098
2 2 2
Width W (mm) 7.1 7.5
Lg mm
Wg mm
1.2 1.2
1.1 1.4
6.2
6.8
1.2
2.2
6.9 6.9 7.2
7.6 7.5 7.6
1.2 1.3 1.6
1.8 1.7 1.6
Table 2. Simulated and measured output parameters of microstrip patch antenna Mg Content 0.0 0.2 0.4 0.6 0.8 1.0
Frequency F (GHz) Simul Meas ated ured 10.53 10.50 10.50 10.67 10.50 10.33 10.58 10.62 10.44 10.74 10.56 9.35
Return loss RL(dB) Simula Measu ted red -30.98 -14.72 -31.20 -29.95 -28.88 -17.91 -21.48 -12.60 -34.74 -11.53 -16.78 -19.16
% 10dB Bandwidth Simul Meas ated ured 28.47 12.08 23.62 10.64 31.65 20.21
VSWR Simu lated 1.05 1.01 1.06 1.17 1.04 1.33
Meas ured 1.70 1.70 1.12 1.58 1.34 1.26
Gain 0.42 0.32 0.24 0.38 0.35 0.46
[31] Highlights 1. The Mg-Nd-Cd ferrite can be used as substrate for microstrip patch antenna. 2. The lower dielectric and magnetic loss tangent of material were useful for miniaturization of antennas. 3. The overall increased beamwidth is observed for antennas on Mg-Nd-Cd ferrites 4. The gain of antennas as usual decreases with increase in magnetic loss tangent.
Beam width 120° 93° 70° 110° 105° 110°
[32] Graphical Abstract The simulated and measured return loss (RL) as a function of frequency for microstrip patch antennas on Mg-Nd-Cd ferrite substrates are shown in figure. The measured RL is nearly equal to the simulated RL for an antenna on Mg-Nd-Cd ferrite with x = 0.2 indicating better impedance matching to this fabricated antenna as compared to others. The highest bandwidth is observed for antenna on Mg-Nd-Cd ferrite substrate with x = 0.8.
Variation of simulated and measured return loss (RL) with frequency of antennas on MgxCd1-xNd0.03Fe1.97O4 ferrite substrates.
[33]