A rectangular microstrip patch antenna with differed pair of L-slots is presented. The proposed antenna
is designed to evaluate the effect of alteration in probe-feed point. The proposed microstrip antenna is
suitable for bluetooth, mobile and wireless communication applications simultaneously. It is designed successfully for mobile communication systems and Wireless Local Area Networks (WLAN) applications. The
results obtained had showed better improvement in the return loss and radiation pattern in comparison to
the other existing antennas

Parveen, L.

Ramni, G.

Saleem, K.

Sandeep, A.

Electronic Sumy State University Institutional Repository

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ Vol. 7 No 4, 04011(6pp) (2015) Том 7 № 4, 04011(6cc) (2015)   2077-6772/2015/7(4)04011(6) 04011-1  2015 Sumy State University Variation in Feed Point within Differed L-Slot Multi-frequency Microstrip Patch  Sandeep Arya, Ramni Gupta, Saleem Khan, Parveen Lehana  Department of Physics & Electronics, University of Jammu, J&K, India-180006  (Received 21 July 2015; published online 10 December 2015)  A rectangular microstrip patch antenna with differed pair of L-slots is presented. The proposed anten-na is designed to evaluate the effect of alteration in probe-feed point. The proposed microstrip antenna is suitable for bluetooth, mobile and wireless communication applications simultaneously. It is designed suc-cessfully for mobile communication systems and Wireless Local Area Networks (WLAN) applications. The results obtained had showed better improvement in the return loss and radiation pattern in comparison to the other existing antennas.  Keywords: Microstrip patch antenna, Multi-frequency actions, L-slots, Probe feeding, Insertion loss,  Radiation pattern.   PACS numbers: 84.40.Ba, 95.85.Bh   1. INTRODUCTION  The directivity and the muliti-band integrated an-tenna configuration generally employ printed circuits and the parameters of the configured antenna depend on the materials employed and their thickness [1]. Due to tremendous increase in the demand of wireless communication devices, it is advantageous to have an integrated antenna that concurrently covers different frequencies/bands for different applications [2-7]. For mobile applications, an integrated antenna is required to simultaneously provide access for GSM (0.9 GHz-1.80 GHz), CDMA (1.90 GHz-2.20 GHz), Bluetooth (2.45 GHz-2.55 GHz) and WiMAX (2.50 GHz-2.70 GHz) while neglecting other frequencies [8]. Moreover, the devices for 3G mobile communication systems must be compatible with 2G. During recent times, several researchers proposed new designs of antennas to be operated in dual and triple band frequencies [9] [10]. There are mainly two feeding methods in a mi-crostrip patch antenna. Feeding RF power directly to the radiating element through a microstrip line or probe feed, known as contacting method. In the non-contacting method, an electromagnetic field coupling is done to transfer power between the microstrip line and the radiating pact that includes proximity feed-ing and aperture feeding. Thus, there is no physical contact between the elements [11] [12].  In the present work, we have presented the design and the results of the tests of a rectangular microstrip patch antenna. Two differed L-slots are cut in the patch. Probe feeding method is used and the position of the feed point is optimized according to the theoretical analysis. The antenna is then analysed in accordance to the designed dimensions. The paper is planned in a way that details on the analysis of the microstrip patch an-tenna are given in the Analysis section, whereas the design of the proposed antenna is discussed in the sec-tion named Experimental Design. Further, the designed antenna is evaluated for results in the form of output parameters. Results from the tests performed are given in the section Results and Discussions. Finally Conclu-sions of the work are given.  2. ANALYSIS   In a microstrip patch antenna, the patch behaves as a resonant cavity (short circuit walls on top and bot-tom, open-circuit walls on the sides), that only allows certain modes to exist at different resonant frequencies, thus, producing significant radiations. For thin sub-strates, conductor and dielectric losses are prominent while for relatively thicker substrates, surface-wave losses are high. For a thin substrate, the electric field vector is independent of the substrate thickness [13]. The magnetic field inside the patch is given by the Maxwell’s equation   1  H Ej (i)  Since the area of the patch is spread over the two axes, that is, x-axis and y-axis, and the magnetic field is purely horizontal. Thus, it is assumed that the wave is propagating in the z-direction. LΔLyxzLeffSubstratePatchFeed PointW  Fig. 1 – Top view of a rectangular microstrip patch antenna  Considering Fig. 1 as the reference for calculations,  SANDEEP ARYA, RAMNI GUPTA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04011 (2015)   04011-2 the resonance frequency can be calculated by approxi-mating the equations of rectangular wave guide for TMmn mode and the equation is given as   2 2 0  z zE k E  (ii)  The value of Ez can be calculated as   cos cos           zm x n yEL W (iii)  Substituting the value of equation (iii) in equation (ii), and solving for k,   2 22            m nkL W (iv)  Since, 0 0    rk     (v) and, 2  f where f is the resonant frequency, thus f can be calculated as,   2 22            rc m nfL W (vi)  where 0 01 c      (vii)  For broadside beam radiation pattern, TM10 is usu-ally used, Hence, for m  1 and n  0   cos    zxEL (viii)   12     rrcfL (ix)  From Figure 1,   2  effL L L  (x)  Hence, 12      reffrcfL    (xi)  According to Hammerstad formula,     0.3 0.2640.4120.258 0.8reffreffWEhL hWEh                (xii)  where, Ereff is the effective dielectric constant, h is the thickness of dielectric substrate, and W is the width of the patch. The value of Ereff can be calculated as   1/21 11 122 2r rreffhEW                 (xiii)  The width of the patch is given by   0122rcwf (xiv) For sensible designs, some finite ground plane is es-sential beneath the substrate. For such practical design of microstrip patch antenna, it necessitate that the ground plane should be greater than the patch dimen-sions by approximately six times the substrate thick-ness [14-16]. Thus, the dimensions of the ground plane may be given as   6gL h l   (xv)   6gW h w   (xvi)  The input parameters of the microstrip patch an-tenna are estimated using above equations before final-izing the design for 3D modelling.  3. EXPERIMENTAL DESIGN  The proposed designed is simulated using FEM based computer simulation technology (CST MICRO-WAVE STUDIO) software in high frequency (HF) do-main solver. Figure 2 shows the 3D geometry of the dou-ble layered slotted microstrip patch antenna design. It consists of two mirror L-slots on the square shaped patch. The dimensions of the designed antenna and loca-tion of the co-axial probe feed point is set using theoreti-cal analysis as is given in the previous section. The oper-ating range from single frequency to penta-frequency applications within the S-band depends on the distance and orientation of the slots as well as on the position of the probe feed point.    Fig. 2 – 3D Schematic of designed microstrip patch antenna  The top view of the double layered patch antenna is shown in Figure 3. The proposed design is based on Roger’s duroid RT-5880 substrate while the material selected for the patch is copper (Cu). The dimensions of the metallic patch are 45  45 mm2 with thickness 0.5 mm. The thickness of the substrate is 3 mm. The designed antenna is enclosed in the square (90  90 mm2) shaped domain with thickness 0.5 mm containing air or vacuum inside it. The domain is assumed to be surrounded by a perfectly matched lay-er (PML) so as to absorb the radiation from the antenna with minimum reflection, thus, contains minimum re-turn loss. The dimensions of the bottom layer, i.e. ground are 60 mm  60 mm  9 mm. The material chosen for the ground and the patch are same. Table 1 shows the mate-rial properties that are equally accountable in simulat-ing the design.   VARIATION IN FEED POINT WITHIN DIFFERED… J. NANO- ELECTRON. PHYS. 7, 04011 (2015)   04011-3    Fig. 3 – Top view of the design along with the dimensions  Table 1 – Material Properties  Properties Materials Rogers RT 5880 Copper (Cu) Air in outer domain Permittivity (r) 2.2 1.0 1.0 Permeability (r) 1.0 1.0 1.0 Density (kg/m3) 2200 8700 1.16 Electrical conductivity (S/m) 0.001 60  106 0.00 Resistivity (Ωm) 2  1011 1.72  10 – 8 3.3  1016  A coaxial probe feed point is selected in such a way that the proposed antenna design may work successfully for the number of operating frequency regions in the  S-band. The position and the diameter of the coaxial probe influence the performance of the antenna. A multiband antenna is desirable if multiple narrow band channels are to be covered [17] [18]. The bandwidth of the antenna is directly proportional to the substrate thickness h. The impedance matching is difficult for higher value of h due to large probe inductance.   4. RESULTS AND DISCUSSIONS  The results verify the alteration in frequency bands and bandwidth with respect to change in position of the feed point.    Fig. 4 – Characteristic impedance of the simulated antenna  Table 2 shows some of the selected coordinates of the feed point and their effect on performance parameters of the antenna. For this design simulation, the processing speed of the computational machine is 3.1 GHz with 4 GB RAM. The virtual memory used while simulation is 2.1 GHz. Precise sized meshing is not selected to avoid the computational load. Frequency domain setting is selected for simulating the model. The characteristic impedance (Z0) of the simulated design comes out to be 28.3 Ω and is shown in Figure 4. Theoretically, the value of Z0 is 50 Ω that shows small existence of standing waves while propagation of RF signals. Some of the sim-ulated results are shown in Figures 5-8. We have simu-lated the results for each usable frequency while altering the position of coaxial feed point and found that the re-sults are noticeably different with the changing position of feed point. Figure 7 shows the far field gain for the feed point coordinate (– 9,0) and the far field gain is ob-tained for five different frequencies with maximum gain varying between – 6.1 dBM/m2 to – 3.91 dBM/m2. Similarly, Fig. 8 shows the far filed gain while changing the feed point co-ordinates from (– 9,0) to  (– 5,0).  Table 2 – Parametric variations with respect to change in feed point position  Feed point (x, y) Resonant fre-quencies (GHz) Return Losses S11 Bandwidth (MHz) Gain (dB) E-field (dB) H-field (dB) Power (dB) – 15, – 15 2.7640 – 10.73 11.6 6.013 20.40 – 31.12 – 5.361 – 5,0 2.1820 2.7544 – 24.00 – 15.78 38.0 31.0 7.097 6.104 21.85 20.76 – 29.67 – 30.76 – 3.912 – 5.004 – 7,0 2.182 2.7725 3.162 – 32.45 – 19.07 – 25.15 37.4 45.0 57.0 7.098 6.024 5.265 21.86 20.74 20.02 – 29.66 – 30.78 – 31.50 – 3.897 – 5.022 – 5.740 – 8,0 2.182 2.7831 3.1719 3.6484 – 38.26 – 13.98 – 24.21 – 11.54 37 40 70 20 7.095 5.990 5.354 6.047 21.86 20.58 20.11 20.50 – 29.66 – 30.94 – 31.42 – 31.02 – 3.898 – 5.180 – 5.655 – 5.261 – 9,0 1.6449 2.1820 2.7900 3.1800 3.6500 – 12.76 – 28.79 – 11.57 – 16.00 – 14.79 36.0 35.0 30.0 68.4 30.0 5.553 7.088, 5.920, 5.442, 6.008 20.09 21.85 20.37 20.09 20.63 – 31.43 – 29.67 – 31.16 – 31.43 – 30.89 – 6.101 – 3.910 – 5.395 – 5.667 – 5.131   SANDEEP ARYA, RAMNI GUPTA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04011 (2015)   04011-4 Fig. 5 – Graphs showing s-parameters values for different coaxial positions: (a) (– 9,0), (b) (– 7,0), (c) (– 8,0) and (d) (– 5,0)    Fig. 6 – Graphs showing VSWR values for coaxial positions: (a) (– 9,0), (b) (– 7,0), (c) (– 8,0) and (d) (– 5,0)   a   VARIATION IN FEED POINT WITHIN DIFFERED… J. NANO- ELECTRON. PHYS. 7, 04011 (2015)   04011-5  b   c   d   e  Fig. 7 – Far field radiation pattern for coaxial position (– 9,0) at different resonant frequencies: (a) 1.6449 GHz, (b) 2.182 GHz,  (c) 2.79 GHz, (d) 3.18 GHz, and (e) 3.65 GHz    Fig. 8 – Far field radiation pattern for coaxial position (– 5,0) at resonant frequencies: (a) 2.182 GHz, and (b) 2.7544 GHz   SANDEEP ARYA, RAMNI GUPTA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04011 (2015)   04011-6 The electric field distribution characteristics indicate that all the resonant modes for different coaxial positions can be tuned and controlled independently. Results show that despite a small distortion, the radiation patterns are reasonably well enough to work in different frequen-cy bands. This feature of varying coaxial point is attrac-tive for the designed antenna where multi-frequencies can be handled with satisfactory gain and radiation pat-terns. The value of E- and H-plane field is also shown in Table 2. The antenna can be operated well between fre-quency ranges 1.6449 GHz to 3.6484 GHz with good bandwidth. Hence the frequency diversity is verified with good performance of the antenna.  5. CONCLUSION  In the present work, a multi-frequency microstrip patch antenna is designed by using coaxial probe feed. Two L-slots are used to design a single, dual, triple, quad and a penta-band antenna. This design does not require complex circuitry and is based on mono layer, single patch. The gain of antenna is high enough, hav-ing 5.354 dB smaller value of gain.  The characteristic impedance (28.3 Ω) is low but the impedance matching is accurate. The proposed antenna can handle mutliple frequencies by simply varying the feed point and covers lot of demanding frequency slots used in day-to-day communication systems.   ACKNOWLEDGEMENT  The first author wishes to thank the University Grants Commission (UGC), India for providing finan-cial assistance to complete this work in the form of mi-nor research project.   REFERENCES  1. A. Elsherbini, K. Sarabandi, IEEE Antennas Wireless Propag. Lett. 10, 75 (2011). 2. Y. Cao, B. Yuan, G. Wang, IEEE Antennas Wireless Propag. Lett. 10, 911 (2011). 3. D.M. Pozar, D.H. Schaubert, Microstrip Antennas: The analysis and design of microstrip antennas and arrays (Wiley: IEEE Press: 1995). 4. K.L. Wong, Compact and broadband microstrip antennas (John Wiley: 2003). 5. G. Kumar, K.P. Ray, Broadband microstrip antennas  (Artech House: 2002). 6. A.A. Deshmukh, K.P. Ray, IEEE Antennas Propag. Maga-zine 53, 41 (2011). 7. C.I. Lin, K.L. Wong, IEEE T. Antennas Propag. 55, 3690 (2007). 8. S. Weigand, G.H. Huff, K.H. Pan, J.T. Bernhard, IEEE T. Antennas Propag. 51, 457 (2003). 9. W.C. Mok, S.H. Wong, K.M. Luk, K.F. Lee, IEEE T.  Antennas 61, 4341 (2013). 10. J. Anguera, G. Font, C. Puente, C. Borja, J. Soler, IEEE Microwave Wireless Component. Lett. 13, 123 (2003). 11. S. Arya, S. Khan, C. Shan, P. Lehana, J. Computational Intellig. Electron. System. 1, 178 (2012). 12. R. Arora, A. Kumar, S. Khan, S. Arya, Int. J. Commun. Antenna Propag. 4, 27 (2014). 13. Z. Safa, Z. Lahbib, J. Microwave., Optoelectron. Electro-magn. Appl. 12, 23 (2013). 14. F. Croq, D.M. Pozar, IEEE T. Antennas Propag. 40, 1367 (1992). 15. T. Huynh, K.F. Lee, Electron Lett. 31, 1310 (1986). 16. F. Yang, X.X. Zhang, X. Ye, Y. Rahmat-Samii, IEEE T. Antennas Propag. 49, 1094 (2001). 17. K.O. Odeyemi, D.O. Akande, E.O. Ogunti, Eur. J. Sci. Res. 55, 72 (2011). 18. K.F. Lee, S.L.S. Yang, A. Kishk, IEEE Antennas Wireless Commun. Lett. 7, 645 (2008).  

Variation in Feed Point within Differed L-Slot Multi-frequency Microstrip Patch

SocioEconomic Challenges Journal (Sumy State University)

JOURNAL OF NANO- AND ELECTRONIC PHYSICS ЖУРНАЛ НАНО- ТА ЕЛЕКТРОННОЇ ФІЗИКИ 
Vol. 7 No 4, 04011(6pp) (2015) Том 7 № 4, 04011(6cc) (2015) 
 
 
2077-6772/2015/7(4)04011(6) 04011-1  2015 Sumy State University 
Variation in Feed Point within Differed L-Slot Multi-frequency Microstrip Patch 
 
Sandeep Arya, Ramni Gupta, Saleem Khan, Parveen Lehana 
 
Department of Physics & Electronics, University of Jammu, J&K, India-180006 
 
(Received 21 July 2015; published online 10 December 2015) 
 
A rectangular microstrip patch antenna with differed pair of L-slots is presented. The proposed anten-
na is designed to evaluate the effect of alteration in probe-feed point. The proposed microstrip antenna is 
suitable for bluetooth, mobile and wireless communication applications simultaneously. It is designed suc-
cessfully for mobile communication systems and Wireless Local Area Networks (WLAN) applications. The 
results obtained had showed better improvement in the return loss and radiation pattern in comparison to 
the other existing antennas. 
 
Keywords: Microstrip patch antenna, Multi-frequency actions, L-slots, Probe feeding, Insertion loss,  
Radiation pattern. 
 
 PACS numbers: 84.40.Ba, 95.85.Bh 
 
 
1. INTRODUCTION 
 
The directivity and the muliti-band integrated an-
tenna configuration generally employ printed circuits 
and the parameters of the configured antenna depend 
on the materials employed and their thickness [1]. Due 
to tremendous increase in the demand of wireless 
communication devices, it is advantageous to have an 
integrated antenna that concurrently covers different 
frequencies/bands for different applications [2-7]. For 
mobile applications, an integrated antenna is required 
to simultaneously provide access for GSM (0.9 GHz-
1.80 GHz), CDMA (1.90 GHz-2.20 GHz), Bluetooth 
(2.45 GHz-2.55 GHz) and WiMAX (2.50 GHz-2.70 GHz) 
while neglecting other frequencies [8]. Moreover, the 
devices for 3G mobile communication systems must 
be compatible with 2G. During recent times, several 
researchers proposed new designs of antennas to be 
operated in dual and triple band frequencies [9] [10]. 
There are mainly two feeding methods in a mi-
crostrip patch antenna. Feeding RF power directly to 
the radiating element through a microstrip line or 
probe feed, known as contacting method. In the non-
contacting method, an electromagnetic field coupling 
is done to transfer power between the microstrip line 
and the radiating pact that includes proximity feed-
ing and aperture feeding. Thus, there is no physical 
contact between the elements [11] [12].  
In the present work, we have presented the design 
and the results of the tests of a rectangular microstrip 
patch antenna. Two differed L-slots are cut in the patch. 
Probe feeding method is used and the position of the 
feed point is optimized according to the theoretical 
analysis. The antenna is then analysed in accordance to 
the designed dimensions. The paper is planned in a way 
that details on the analysis of the microstrip patch an-
tenna are given in the Analysis section, whereas the 
design of the proposed antenna is discussed in the sec-
tion named Experimental Design. Further, the designed 
antenna is evaluated for results in the form of output 
parameters. Results from the tests performed are given 
in the section Results and Discussions. Finally Conclu-
sions of the work are given. 
 
2. ANALYSIS  
 
In a microstrip patch antenna, the patch behaves as 
a resonant cavity (short circuit walls on top and bot-
tom, open-circuit walls on the sides), that only allows 
certain modes to exist at different resonant frequencies, 
thus, producing significant radiations. For thin sub-
strates, conductor and dielectric losses are prominent 
while for relatively thicker substrates, surface-wave 
losses are high. For a thin substrate, the electric field 
vector is independent of the substrate thickness [13]. 
The magnetic field inside the patch is given by the 
Maxwell’s equation 
 
 
1

  H E
j
 (i) 
 
Since the area of the patch is spread over the two axes, 
that is, x-axis and y-axis, and the magnetic field is 
purely horizontal. Thus, it is assumed that the wave is 
propagating in the z-direction. 
L
ΔL
y
x
z
Leff
Substrate
Patch
Feed Point
W
 
 
Fig. 1 – Top view of a rectangular microstrip patch antenna 
 
Considering Fig. 1 as the reference for calculations, 
 SANDEEP ARYA, RAMNI GUPTA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04011 (2015) 
 
 
04011-2 
the resonance frequency can be calculated by approxi-
mating the equations of rectangular wave guide for 
TMmn mode and the equation is given as 
 
 2 2 0  z zE k E  (ii) 
 
The value of Ez
 
can be calculated as 
 
 cos cos
    
    
   
z
m x n y
E
L W
 (iii) 
 
Substituting the value of equation (iii) in equation (ii), 
and solving for k, 
 
 
2 2
2         
   
m n
k
L W
 (iv) 
 
Since, 0 0    rk     (v) 
and, 2  f where f is the resonant frequency, thus 
f can be calculated as, 
 
 
2 2
2
 
 
   
    
   r
c m n
f
L W
 (vi) 
 
where 
0 0
1
 
c      (vii) 
 
For broadside beam radiation pattern, TM10 is usu-
ally used, Hence, for m  1 and n  0 
 
 cos
 
  
 
z
x
E
L
 (viii) 
 
 
1
2 
 
  
 
r
r
c
f
L
 (ix) 
 
From Figure 1, 
 
 2  effL L L  (x) 
 
Hence, 
1
2 
 
  
 
 
r
effr
c
f
L
    (xi) 
 
According to Hammerstad formula, 
 
 
 
 
0.3 0.264
0.412
0.258 0.8
reff
reff
W
E
h
L h
W
E
h
  
   
   
  
   
  
 (xii) 
 
where, Ereff is the effective dielectric constant, h is the 
thickness of dielectric substrate, and W is the width of 
the patch. The value of Ereff can be calculated as 
 
 
1/2
1 1
1 12
2 2
r r
reff
h
E
W
 

     
      
    
 (xiii) 
 
The width of the patch is given by 
 
 
0
1
2
2
r
c
w
f



 (xiv) 
For sensible designs, some finite ground plane is es-
sential beneath the substrate. For such practical design 
of microstrip patch antenna, it necessitate that the 
ground plane should be greater than the patch dimen-
sions by approximately six times the substrate thick-
ness [14-16]. Thus, the dimensions of the ground plane 
may be given as 
 
 6gL h l   (xv) 
 
 6gW h w   (xvi) 
 
The input parameters of the microstrip patch an-
tenna are estimated using above equations before final-
izing the design for 3D modelling. 
 
3. EXPERIMENTAL DESIGN 
 
The proposed designed is simulated using FEM 
based computer simulation technology (CST MICRO-
WAVE STUDIO) software in high frequency (HF) do-
main solver. Figure 2 shows the 3D geometry of the dou-
ble layered slotted microstrip patch antenna design. It 
consists of two mirror L-slots on the square shaped 
patch. The dimensions of the designed antenna and loca-
tion of the co-axial probe feed point is set using theoreti-
cal analysis as is given in the previous section. The oper-
ating range from single frequency to penta-frequency 
applications within the S-band depends on the distance 
and orientation of the slots as well as on the position of 
the probe feed point. 
 
 
 
Fig. 2 – 3D Schematic of designed microstrip patch antenna 
 
The top view of the double layered patch antenna is 
shown in Figure 3. 
The proposed design is based on Roger’s duroid RT-
5880 substrate while the material selected for the patch 
is copper (Cu). The dimensions of the metallic patch are 
45  45 mm2 with thickness 0.5 mm. The thickness of the 
substrate is 3 mm. The designed antenna is enclosed in 
the square (90  90 mm2) shaped domain with thickness 
0.5 mm containing air or vacuum inside it. The domain 
is assumed to be surrounded by a perfectly matched lay-
er (PML) so as to absorb the radiation from the antenna 
with minimum reflection, thus, contains minimum re-
turn loss. The dimensions of the bottom layer, i.e. ground 
are 60 mm  60 mm  9 mm. The material chosen for the 
ground and the patch are same. Table 1 shows the mate-
rial properties that are equally accountable in simulat-
ing the design. 
 
 VARIATION IN FEED POINT WITHIN DIFFERED… J. NANO- ELECTRON. PHYS. 7, 04011 (2015) 
 
 
04011-3 
  
 
Fig. 3 – Top view of the design along with the dimensions 
 
Table 1 – Material Properties 
 
Properties Materials 
Rogers RT 
5880 
Copper 
(Cu) 
Air in outer 
domain 
Permittivity (r) 2.2 1.0 1.0 
Permeability (r) 1.0 1.0 1.0 
Density (kg/m3) 2200 8700 1.16 
Electrical 
conductivity (S/m) 
0.001 60  106 0.00 
Resistivity (Ωm) 2  1011 1.72  10 – 8 3.3  1016 
 
A coaxial probe feed point is selected in such a way that 
the proposed antenna design may work successfully for 
the number of operating frequency regions in the  
S-band. The position and the diameter of the coaxial 
probe influence the performance of the antenna. A 
multiband antenna is desirable if multiple narrow band 
channels are to be covered [17] [18]. The bandwidth of 
the antenna is directly proportional to the substrate 
thickness h. The impedance matching is difficult for 
higher value of h due to large probe inductance.  
 
4. RESULTS AND DISCUSSIONS 
 
The results verify the alteration in frequency bands 
and bandwidth with respect to change in position of the 
feed point. 
 
 
 
Fig. 4 – Characteristic impedance of the simulated antenna 
 
Table 2 shows some of the selected coordinates of the 
feed point and their effect on performance parameters of 
the antenna. For this design simulation, the processing 
speed of the computational machine is 3.1 GHz with 
4 GB RAM. The virtual memory used while simulation is 
2.1 GHz. Precise sized meshing is not selected to avoid 
the computational load. Frequency domain setting is 
selected for simulating the model. The characteristic 
impedance (Z0) of the simulated design comes out to be 
28.3 Ω and is shown in Figure 4. Theoretically, the value 
of Z0 is 50 Ω that shows small existence of standing 
waves while propagation of RF signals. Some of the sim-
ulated results are shown in Figures 5-8. We have simu-
lated the results for each usable frequency while altering 
the position of coaxial feed point and found that the re-
sults are noticeably different with the changing position 
of feed point. Figure 7 shows the far field gain for the 
feed point coordinate (– 9,0) and the far field gain is ob-
tained for five different frequencies with maximum gain 
varying between – 6.1 dBM/m2 to – 3.91 dBM/m2. 
Similarly, Fig. 8 shows the far filed gain while 
changing the feed point co-ordinates from (– 9,0) to  
(– 5,0). 
 
Table 2 – Parametric variations with respect to change in feed point position 
 
Feed point 
(x, y) 
Resonant fre-
quencies (GHz) 
Return Losses 
S11 
Bandwidth 
(MHz) 
Gain 
(dB) 
E-field 
(dB) 
H-field 
(dB) 
Power 
(dB) 
– 15, – 15 2.7640 – 10.73 11.6 6.013 20.40 – 31.12 – 5.361 
– 5,0 2.1820 
2.7544 
– 24.00 
– 15.78 
38.0 
31.0 
7.097 
6.104 
21.85 
20.76 
– 29.67 
– 30.76 
– 3.912 
– 5.004 
– 7,0 2.182 
2.7725 
3.162 
– 32.45 
– 19.07 
– 25.15 
37.4 
45.0 
57.0 
7.098 
6.024 
5.265 
21.86 
20.74 
20.02 
– 29.66 
– 30.78 
– 31.50 
– 3.897 
– 5.022 
– 5.740 
– 8,0 2.182 
2.7831 
3.1719 
3.6484 
– 38.26 
– 13.98 
– 24.21 
– 11.54 
37 
40 
70 
20 
7.095 
5.990 
5.354 
6.047 
21.86 
20.58 
20.11 
20.50 
– 29.66 
– 30.94 
– 31.42 
– 31.02 
– 3.898 
– 5.180 
– 5.655 
– 5.261 
– 9,0 1.6449 
2.1820 
2.7900 
3.1800 
3.6500 
– 12.76 
– 28.79 
– 11.57 
– 16.00 
– 14.79 
36.0 
35.0 
30.0 
68.4 
30.0 
5.553 
7.088, 
5.920, 
5.442, 
6.008 
20.09 
21.85 
20.37 
20.09 
20.63 
– 31.43 
– 29.67 
– 31.16 
– 31.43 
– 30.89 
– 6.101 
– 3.910 
– 5.395 
– 5.667 
– 5.131 
 
 SANDEEP ARYA, RAMNI GUPTA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04011 (2015) 
 
 
04011-4 
Fig. 5 – Graphs showing s-parameters values for different coaxial positions: (a) (– 9,0), (b) (– 7,0), (c) (– 8,0) and (d) (– 5,0) 
 
 
 
Fig. 6 – Graphs showing VSWR values for coaxial positions: (a) (– 9,0), (b) (– 7,0), (c) (– 8,0) and (d) (– 5,0) 
 
 
a 
 
 VARIATION IN FEED POINT WITHIN DIFFERED… J. NANO- ELECTRON. PHYS. 7, 04011 (2015) 
 
 
04011-5 
 
b 
 
 
c 
 
 
d 
 
 
e 
 
Fig. 7 – Far field radiation pattern for coaxial position (– 9,0) at different resonant frequencies: (a) 1.6449 GHz, (b) 2.182 GHz,  
(c) 2.79 GHz, (d) 3.18 GHz, and (e) 3.65 GHz 
 
 
 
Fig. 8 – Far field radiation pattern for coaxial position (– 5,0) at resonant frequencies: (a) 2.182 GHz, and (b) 2.7544 GHz 
 
 SANDEEP ARYA, RAMNI GUPTA, ET AL. J. NANO- ELECTRON. PHYS. 7, 04011 (2015) 
 
 
04011-6 
The electric field distribution characteristics indicate 
that all the resonant modes for different coaxial positions 
can be tuned and controlled independently. Results show 
that despite a small distortion, the radiation patterns 
are reasonably well enough to work in different frequen-
cy bands. This feature of varying coaxial point is attrac-
tive for the designed antenna where multi-frequencies 
can be handled with satisfactory gain and radiation pat-
terns. The value of E- and H-plane field is also shown in 
Table 2. The antenna can be operated well between fre-
quency ranges 1.6449 GHz to 3.6484 GHz with good 
bandwidth. Hence the frequency diversity is verified 
with good performance of the antenna. 
 
5. CONCLUSION 
 
In the present work, a multi-frequency microstrip 
patch antenna is designed by using coaxial probe feed. 
Two L-slots are used to design a single, dual, triple, 
quad and a penta-band antenna. This design does not 
require complex circuitry and is based on mono layer, 
single patch. The gain of antenna is high enough, hav-
ing 5.354 dB smaller value of gain.  The characteristic 
impedance (28.3 Ω) is low but the impedance matching 
is accurate. The proposed antenna can handle mutliple 
frequencies by simply varying the feed point and covers 
lot of demanding frequency slots used in day-to-day 
communication systems.  
 
ACKNOWLEDGEMENT 
 
The first author wishes to thank the University 
Grants Commission (UGC), India for providing finan-
cial assistance to complete this work in the form of mi-
nor research project. 
 
 
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Variation in Feed Point within Differed L-Slot Multi-frequency Microstrip Patch

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