Paper Title (use style: paper title)


2018 International Conference on Sensor Network and Computer Engineering (ICSNCE 2018) 

69 

 

The Comparison on the Side Feed Mode of Micro-strip Patch 

Wen Dang 

Department of Communication and Information 

Xi'an Technology University 

Lane 78, Yanta Road,  

Beilin District, Xian, China 

e-mail: 13637863650@163.com 

 

Xinliang Liu 

Department of Communication and Information 

Xi'an Technology University 

Lane 78, Yanta Road,  

Beilin District, Xian, China 

e-mail: 84829562@qq.com 

 
Abstract—The feeding of the micro-strip patch is flexible and 

complex, especially side feeding. In this paper, a single micro-

strip patch antenna with a center frequency of 2.45GHZ is 

taken as an example to explore the performance of the slotted 

feed and non-slotted feed and verified in HFSS15.0. Combined 

with HFSS15.0 software simulation and theoretical calculation, 

the corresponding conclusions can be obtained. The theoretical 

value and simulation results will be shown that: the required 

1/4 converter sizes of the non-slotted side feed and slotted side 

feed are different. By contrasting with sizes of two feeding 

modes, electrical size of the slotted feed is smaller. It can be 

known that all performances of the slotted feed are more 

superior. 

Keywords-HFSS Simulation; Micro-strip Patch; Side-feed; 

Slot; Matching 

I. INTRODUCTION  

Antenna is a necessary component for radiating and 
receiving radio waves in engineering systems such as 
wireless communications, radio and television, navigation, 
satellite, radar and other engineering systems. The micro-
strip patch is simple and easy to plastic, its feeding modes 
are flexible and changeable. The stability of the antenna can 
be also affected by micro-strip patch feeding mode. The 
different feeding mode has different properties. The design 
of the feeding system determines the current distribution of 
the radiation patch. The more consistent the current direction 
is, the higher the gain is, the greater the energy is, and the 
better the directivity is [3]. Therefore, in an antenna system, 
it is especially important that how the feeding system should 
design, which determines the stability of the system and the 
quality of microwave devices. 

In this paper, two different side feed modes of the 
radiation patch are analyzed and compared. By simulating 
the cell structure of the micro-strip patch antenna with the 
center frequency f at 2.45GHZ in HFSS15.0, the 
corresponding sizes of the 1/4 impedance converter and 
intrinsic impedance are different, when the feeding position 
is not the same place, which has been validated in HFSS15.0. 
The mode following the theoretical sizes calculated by given 
equations is simulated in HFSS15.0. The simulation results 
have been drawn the followings. For the non-slotted side 
feed, the radiation impedance is caused by the edge 
impedance of the patch. The theoretical calculated 1/4 
converter has a large error between the length and width 
values. To achieve the minimum S11 at the center frequency, 

it is necessary to optimize the micro-strip line parameters for 
several times. For the slotted side feed, the radiation 
impedance is produced by the edge impedance of the patch 
and the edge impedance of the groove. The theoretical value 
of the 1/4 converter has a higher accuracy. The best 
performance of the center frequency can be achieved by 
adjusting the width and depth of the slotted feeding. Based 
on the above conditions, the minimum value of the antenna 
S11 can be obtained, the smaller the reflection energy is, the 
greater the transmission efficiency is. 

II. DESIGN AND ANALYSIS OF RADIATION PATCH UNIT 

In this paper, the radiation patch of the center frequency f 
= 2.45GHZ would be used as an example, the thickness h of 
the substrate with Rogers5880 is 1.5mm, its dielectric 
constant is 2.2. According to the formula (1) – (5) [8] - [9] , 
it can  be obtained  that the width w, length L were 40mm 
and 48.4mm  respectively, as well as  the input impedance. 

The width w of radiation patch  is the following: 

2

1

2

1

2










 
 r

f

c
w





Where c is the speed of free space wave. 
Taking into account the edge shortening effect, the actual 

length L of  the radiation patch should be expressed as: 

L
f

c
L

e

 2
2 



Where 

e


 is the effective permittivity, L  is the length 
of the equivalent radiation gap, they can be calculated by 
using the following formulas  respectively.   

2

1

e
121

2

1

2

1


















w

h
rr





 



2018 International Conference on Sensor Network and Computer Engineering (ICSNCE 2018) 

70 

 

  
  8.0258.0

264.03.0
412.0 e






hw

hw
hL

e






The input impedance can be obtained as following: 



 
)(cos

2
2

z

G
zY

in






Where G is the radiation conductance, β is the phase 
constant in the medium, and z is the distance from the feed 
point to the radiation patch edge. It can be concluded that the 
different input impedance can be obtained by selecting 
different feeding point positions. 

A. Radiation Patch Unit  

The length and width of the radiation patch can be 
calculated by formulas (1)-(4). The edge impedance of the 
radiation patch can be obtained by formula (5). The length 
and width of the 1/4 impendence converter can be known by 
the edge impedance. The width and length of the 50Ω 
intrinsic impedance can be also counted. According to the 
optimum sizes, the model can be built in hfss15.0 shown in 
Fig.1. 

 
The size of the slotted micro-strip patch can be also 

calculated by the same method. The optimum sizes can be 
obtained after many optimizations, it can be built in hfss15.0 
shown in Fig.2. 

 
 
 
 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

Figure 1. Slotted patch antenna 

After hfss15.0 simulation, the results are obtained in 

TableⅠ. The simulation results obtained by the two feeding 
methods are basically the same. The theoretical sizes of the 
slotted feed is closer to the simulated ones, even almost 
identical, and its electrical size is smaller. When optimizing 
in the way of the slotted feed, the workloads can be greatly 
reduced and the efficiency can be improved. 

B. Verification 

In order to verify the rationality of the above conclusions, 
the  input port can be excited by the wave port with a 50 Ω 
load. when the width of the micro-strip line is w0 and the 
medium thickness is h, the height of the wave port is 
generally set to 6 ~ 10h. When there is w0>h, the width of 
the wave port is set to 10w0. When there is w0 <h, the width 
of the wave port is generally set to 5w0 or 3 ~ 4h [8]. 
According to the rules, it can be built and verified in 
HFSS15.0. The size and impedance of each port are shown 

in TableⅠ. 
From TableⅠ, it can be seen that the impedance value 

can be directly gotten by adding wave-port excitation for the 
converter as the input impedance, after running in hfss15.0. 
The slotted feed mode is closer to the theoretical value than 
the non-slotted feed mode. Thus, the slotted feed mode can 
improve the efficiency of the operation and reduce the 
workload. 

C. Comparison and New Discoveries of Two Feed Modes  

In the micro-strip feed, the return loss can be affected by 
the size of the 1/4 converter. The reflected voltage wave in 
the circuit can be reduced by proper using the 1/4 converter, 
the loss can be also reduced. The different performances of 

slotted and non-slotted feed are shown in TableⅠ. 
 

48.4mm 

40mm 

6mm 

14mm 

10mm 

1mm 

Figure 1.  No slotted patch antenna 

4.62mm 

48.4mm 

40mm 

 

6mm 

4mm 

22.76m 

1
0

m
m

 

Figure 2.  Slotted patch antenna 

 



2018 International Conference on Sensor Network and Computer Engineering (ICSNCE 2018) 

71 

 

 

TABLE I.  COMPARISON BETWEEN THE SLOTTED AND NON-SLOTTED FEEDING ( UNIT: MM ) 

 The Slotted  The Non-slotted   

 Optimization Optimization Calculation 

The length of patch 48.4 48.4 48.40 

The wide of patch 40 40 39.70 

 

The port of 1/4 converter 

length 22.76 14 22.76 

wide 2.1 1 2.14 

impedance 82.3Ω 116.2Ω 79.37Ω 

 
The port of 50Ω 

length 4.62 6 4.62Ω 

wide 6 10  

impedance 50.7Ω 42.2Ω 50Ω 

Substrate thickness H 1.5 1.5 1.5 

The wide of the slotted 4   

The length of the slotted 10   

S11 -45.3db -37.9db  

gain 7.89db 7.82db  

Size 2010mm2 1971.516mm2  

bandwidth 1.2% 1.2%  

reduction 2% 

 

From TableⅠ, it can be concluded that the electrical size 
of the slotted feed is slightly smaller than the electrical size 
of the non-slotted feed, in that case where the return loss, the 
gain and bandwidth of the same patch are substantially 
consistent. The theoretical value of the slotted feed size is 
closer to the optimum value. Therefore, when the micro-strip 
arrays are formed, the advantages of the slotted feed are 
more obvious. 

III.  CONCLUSION 

According to comparison and analysis of the simulation 
results of the two feeding methods, the following 
conclusions can be drawn: 

The value of the S11 is closely related with the size of the 
micro-strip line, especially the width of the micro-strip line. 
The impact of the width play important role, the center 
frequency and the ideal value can be coincident by adjusting 
the width. The value of S11 can be made better by adjusting 
the length, So that the feed network can achieve full match. 

The 1/4 converter （ Z1 ） of the non-slotted feed is 
determined by the micro-strip characteristic impedance (ZL) 
and the edge impedance (ZL) of the patch. Similarly, the 
edge impedance of the slotted feed patch is mainly caused by 
the edge of the slot and the radiation patch. 

The edge impedance and micro-strip line impedance can 
be calculated in HFSS15.0 by directly adding wave port 
excitation. After calculation, the impedance Z0  values can 

be gotten as shown in TableⅠ. 
In short, all performances of the slotted feed are better 

than ones of the non-slotted feed. In the feed mode selection, 
the slotted feed is a relatively stable feeding method. 

IV. THE DEVELOPMENT PROSPECT AND SIGNIFICANCE 

In the paper, by comparing the performances of two 
different feeding methods[11], it could been seen that 

performances of all aspects of slotted feed are even better. 
When the slotted feed is matched, the theoretical value is 
more accurate without too much optimization, saving a lot of 
time and improving the simulation efficiency, which 
provides a good foundation for the micros-trip antenna array. 
The slotted radiation patch reduces the electrical size of the 
patch greatly, so that the antenna structure is more compact 
and miniaturization. This will be the future development 
tendency of micro-strip antennas. 

Today, micro-strip theory is mature and widely used. 
With the wide application and great development of micro-
strip antenna in the fields of satellite communication [5], 
millimeter-wave [4] and mobile communication, the research 
of micro-strip planar antenna technology [10] will become 
one of the hotspots in future antenna research. At present, the 
compact profile of the antenna is a welcomed developed 
tendency [6] - [7]. The sizes of the radiation patch, whether it 
is as a unit patch micro-strip antenna, or as the array antenna 
unit array, affect the antenna resonance point and other 
performances. Stable basic unit structure will be provided 
broadband for the micro-strip patch as  good foundation. 

ACKNOWLEDGEMENT 

I would like to thank all my teachers who have helped me 
to develop the fundamental and essential academic 
competence. My sincere appreciation also goes to all the 
teachers  and students who helped me. 

 

REFERENCES 

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wideband signal feed circularity polarized microstrip antenna, ”  
Progress In Electromagnetics Research, PIER 80, 45–61, 2008 



2018 International Conference on Sensor Network and Computer Engineering (ICSNCE 2018) 

72 

 

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