1. INTERNATIONAL JOURNAL OF ELECTRONICS AND
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
COMMUNICATION–ENGINEERING Issue 1, January- June (2012), (IJECET)
0976 – 6464(Print), ISSN 0976 6472(Online) Volume 3, & TECHNOLOGY © IAEME
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 3, Issue 1, January- June (2012), pp. 123-129
IJECET
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A DESIGN PROCEDURE FOR ACTIVE RECTANGULAR
MICROSTRIP PATCH ANTENNA
1
Mahmoud Abdipour, Gholamreza Moradi, Reza Sarraf Shirazi
2 2
1 Department of Electrical Engineering, Azad Branch, Islamic Azad
University,Arak,Iran (Mahmoud.abdipour@gmail.com)
2 Department of Electrical Engineering,Amirkabir University,Tehran, Iran
(ghmoradi@aut.ac.ir)
2 Department of Electrical Engineering,Amirkabir University,Tehran,Iran
(sarraf@aut.ac.ir)
ABSTRACT
In this paper a design procedure for active rectangular microstrip patch
antenna is presented. The design procedure begins with the theory of passive
part. Then appropriate input and output matching circuits are examined. Finally,
with connecting passive antenna as amplifier input, the overall structure is
designed and simulated. Also a comparison between passive and active antenna
is done. The used substrate is RT/DOUROID 5880 with relative permittivity of
2.2 and thickness of 1.588 mm .The ADS software and its full wave Momentum
is used for simulation. The results show a relative improvement in the active
antenna characteristics with respect to passive antenna.
Keywords- Microstrip antenna, Active antenna , X-band, ADS 2009
1. INTRODUCTION
In recent years, active antenna has been welcomed because of their vast
advantages. In fact, using this structure in addition to the advantages of passive
antenna, can be overcome the disadvantages of these antenna such as small
bandwidth, large noise figure and large length [1]. In active antenna structure, a
passive antenna is placed beside of amplifier. If the antenna to be used as a load
to the amplifier, and if antenna to be used as an input to the amplifier, antenna
is transmitter and receiver, respectively. Important considerations in the design
of active antenna include high gain and smooth in all its bandwidth, low noise
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME
figure, appropriate matching in input and output, linear operation and the small
size. Among antennas that are used as passive part for such structures,
rectangular microstrip patch antenna are the most popular because of ease of
analysis and fabrication, and their attractive radiation characteristics[2]. Feed
type, plays an important role in the design of patch antenna. an microstrip patch
antenna can be feed with coaxial probe or microstrip line that in the meanwhile
microstrip line is preferable because this line can be considered to continue of
patch which help to better and easier input/output matching. Since the input
impedance of a patch is often large, we usually use inset-fed method for input
impedance matching with the line characteristic impedance. In this method
how much we move from the edge toward the patch center, patch impedance is
reduced, so that in patch center is equal to zero[3].
2. PATCH ANTENNA DESIGN
Fig.1 shows the patch geometry of an inset-fed rectangular patch. Basic
parameters include length of patch( L ) , width of patch ( W ) , the notch width
p p
(g), the inset distance from the radiating edge(d) and width of feed line (w).
Approximate equations related on the rectangular antenna analysis and design
can be calculated as follows:
The width of the antenna can be determined by [4]:
vo 2
WP =
2 fr εr +1 (1)
The effective dielectric constant is given by [5],[6]:
−1/2
εr +1 εr −1  h 
ε ref f = + 1 + 12  for W p / h > 1
2 2 (2)
 Wp 

Normalized extension of the length, ∆L, which is due to open ended
transmission line can be obtained by [7]:
 Wp 
(ε ref f + 0.3)  + 0.264 
∆L
= 0.412  h 
h  Wp  (3)
(ε ref f − 0.258 )  + 0.8 
 h 
The actual length of the patch, Lp , can be expressed by [3]:
νo
Lp = − 2∆L
2 f r ε reff (4)
The notch width, g, can be obtained by using [8]:
νo 4.6 × 10 − 14 f
fr = +
2 × ε ref f g 1.01
(5)
νo 4.65 × 10−12
g=
2 × ε ref f
f (6)
In this equations, is resonant frequency and f is operating frequency.
We can calculate the value of Z as: 0
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3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME
π 
Z o = Rin cos 2  d 
L 
 p  (7)
Where, d , is the inset distance from the radiating edge, and Rin is the resonant
input resistance when the patch is fed at a radiating edge.
We can calculate R as [9]: in
1
Rin =
2 ( G1 + G12 ) (8)
Where, G1 , is the conductance of a single slot and can be obtained by:
2
  koW p 
 sin 
π
Cos θ  
1   2   sin 3 θ dθ
120 π 2 ∫ 
G1 =

0

cos θ
 (9)

 

and , G , is the mutual conductance and can be calculated using:
12
2
  koW p 
 sin 
π
Cos θ  
1   2   J k L sin θ sin 3 θ dθ
120 π 2 ∫   o( o p
G12 =
cos θ
)
0
 

 

(10)
J0 , is the Bessel function of the first kind of order zero.
Fig.1 Geometry of a microstrip patch antenna
Also the width of feed line assuming ZC = Z 0 can be calculated using [1]:
120π
ZC = (11)
W W 
ε reff  h + 1.393 + 0.667 ln  h + 1.444  
  
The final values are determined through extensive numerical simulations.
2. AMPLIFIER DESIGN
Application is an essential factor in amplifier part design of an active
antenna. For example, for transmitter applications, the design goals are to
achieve higher gain and more bandwidth. For reception applications, problem
about noise figure is design goal. This is a criterion for transistor selection, so
that for transmitter antenna, HBT transistors are preferred because of their high
gain. Whereas for reception application, HEMT transistors are good choices
because of their low noise.
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4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME
Various stage of amplifier design for the active antenna is shown in the
following flow diagram.
Fig.2 Amplifier design flow diagram
The final stage is integration amplifier part with the passive antenna.
4. DESIGN EXAMPLE
In this section, an active microstrip patch antenna is designed and we will
review the effect of using active part beside a passive antenna. Designing is
done for X-band with 10 GHz center frequency. The substrate is RT/DUROID
5880 that its characteristics are given in Table.1.
Table 1 RT/DUROID 5880 characteristics
Substrate εr h, mm T,mm
RT/DUROID
2.2 1.588 0.035
5880
ADS software is used to simulate. Using equation [1]-[11], we can calculate
the physical dimensions of microstrip patch antenna as shown in Table.2.
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5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME
Table 2 The physical dimensions of microstrip patch antenna
Length of the patch,LP, in mm 9.6
Width of the patch,WP, in mm 11.86
Position of inset fed point,d,in mm 2.5
Width of the microstrip feed
2
line,W,in mm
Notch width,g,in mm 0.2
The simulation results of the designed patch are given in Fig.3.As shown in
this figure, the antenna has a good matching performance.
200 0
m1
indep(m1)= 1.000E10
plot_vs(real(Zin), freq)=49.374 -5
150
dB(S(1,1))
-10
real(Zin)
100
m2
-15 freq=10.05GHz
m1 dB(S(1,1))=-22.399
50
-20
m2
0 -25
8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0
freq, GHz freq, GHz
(a) (b)
Fig.3 The simulation results (a) The Input Impedance (b) The S11 .
Using given flow diagram for the design of the amplifier and connect to the
passive part and overall circuit layout extraction we reach to following strucure
.
Fig 4 Final layout of receiver active antenna
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6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME
Simulation results are shown in the following
0.665
1.330
1.325 0.660 m2
m1 freq=10.00GHz
freq=10.00GHz nf(2)=0.650
1.320 VSWR2=1.312 0.655
m2
VSWR2
nf(2)
1.315
m1 0.650
1.310
0.645
1.305
0.640
1.300
0.635
1.295
9.90 9.92 9.94 9.96 9.98 10.00 10.02 10.04 10.06 10.08 10.10
9.90 9.92 9.94 9.96 9.98 10.00 10.02 10.04 10.06 10.08 10.10
freq, GHz
freq, GHz
(a) (b)
1.8
12 m3
m4
1.7
freq=10.00GHz
VSWR1=1.391
9
1.6
VSWR1
dB(S(2,1))
6
1.5
3 m3 m4
1.4
freq=10.00GHz
dB(S(2,1))=11.132
0 1.3
9.90 9.92 9.94 9.96 9.98 10.00 10.02 10.04 10.06 10.08 10.10 9.90 9.92 9.94 9.96 9.98 10.00 10.02 10.04 10.06 10.08 10.10
freq, GHz freq, GHz
(c) (d)
Fig.5 Results of active antenna simulation (a) VSWRout (b) NFout (c) The S21 (d) VSWRin
A comparison between active and passive antennas is shown in Table.3.
Table 3 A comparison between active and passive antennas
Characteristic Preferable
Antenna
Structure Simplicity Passive Antenna
Design Simplicity Passive Antenna
Reliability Passive Antenna
Pattern Characteristic Similar
EIRP & Output Power Active Antenna
Bandwidth Active Antenna
Gain Active Antenna
Noise Figure Active Antenna
5. CONCLUSION
In this paper a procedure of designing active microstrip patch antenna was
presented. Also an X-band active antenna is designed. Finally a comparison
between passive and active structure is examined.
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7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 1, January- June (2012), © IAEME
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