2022 19th International Computer Conference on Wavelet Active Media Technology and Information Processing (ICCWAMTIP) | 978-1-6654-9389-5/22/$31.00 ©2022 IEEE | DOI: 10.1109/ICCWAMTIP56608.2022.10016577
DESIGN OF 2-12 GHZ ULTRA-WIDEBAND BAND PASS FILTER USING
GAAS INTEGRATED PASSIVE DEVICE TECHNOLOGY
TAKELE YONAS MIRETE1, GEBRE FISEHATSION MESFIN2, MERESA GIRMA NIGUS1, TEGEGNE
SOLOMON ESHETIE3, MENGESHA YARED GETACHEW1, MOLLA ELDANA BEYENE4
1
School of Information and Communication Engineering, University of Electronic Science and Technology of China
2
School of Electronic Science and Engineering, University of Electronic Science and Technology of China
3
School of Computer Science, China West Normal University
4
School of Information Science and Engineering, South East University
E-MAIL: mihretieyonas23@gmail.com, mesfinfisehatsion@gmail.com, meresa.girma@gmail.com,
solomoneshetie8@gmail.com, yarget1921@gmail.com, eldanabeyene27@gmail.com
Abstract:
An Ultra-Wideband band pass filter (UWB-BPF) based on
GaAs Technology is considered in this article. It is designed by
cascading the High pass filter (HPF) and Low pass filters (LPF)
with a transmission-zero out band rejection method. The two
filters were designed with 5th order Chebyshev approach
separately and then cascaded to get the desired band pass filter.
To have a fast roll-off attenuation, out-of-band transmission
zero is applied. Thus, a parallel resonance circuit is used.
Moreover, L-network impedance matching has been
introduced to enhance the input return loss. The design has
been successfully realized in theory and also verified by its full
layout
EM simulation. The resulting UWB-BPF with
𝟑. 𝟐𝟑 𝐦𝐦𝟐 compact size provides 1.2 dB insertion loss, 134.6%
fractional bandwidth, 78% selectivity factor, 0.094 ns group
delay, and 16.2 dB return loss.
Keywords:
Ultra-wideband Band Pass Filter; Transmission Zero; Lnetwork; GaAs-IPD; Fractional Band Width
1.
Introduction
Currently, wireless microwave communication systems
are playing vital roles in our daily activities. In Radio
Frequency (RF) front end sections, the band width of out
going and incoming signals need to be limited for a certain
range of frequencies. And this can be handled by a band pass
filter RF circuit. Ultra-wideband wireless technologies use a
wireless system that can transmit data over a large range of
frequency bands for a very short distance with very low
power and high data rates. According to the Federal
Communications Commission (FCC) proclamation in 2002,
the UWB was fixed in the range of frequency 3.10–10.60
GHz for commercial use [1]. From then on, the application
of UWB bandwidth (3.1–10.6 GHz) and corresponding BPF
filter design on this spectrum are getting immense attention
for the past few decades [2]. Researchers and industries have
given attention to UWB circuits. Numerous works
and strategies showed up to cover the desires of UWB-BPF
in terms of insertion loss, selectivity, out-of-band dismissal,
and highlights like compactness and implementable
structures. It has been designed using Inductively
Compensated parallel-Coupled Lines (ICPCL) [1], by
incorporating Defective Ground Structures (DGSs) [3],
based on (GaAs-IPD) [4] using microstrip lines [5], using
Parallelcoupled Lines and Circular Open-circuited Stubs [6],
by a capacitor loaded coupled line [7] and by adopting a
modified multiple-mode resonator (MMR) and annular
structures [8].
In this design, cascading an HPF and LPF based on
GaAs-IPD technology is proposed. LPF is constructed to
attenuate higher-frequency signals for those beyond the
higher cut-off frequency whereas HPF is to reject a signal
below the lower limit frequency of the proposed work. To
ensure, the attenuation of the signal out of the specified
frequency range, 5th order Chebyshev filter design approach
[9] collaborating with the transmission zero out band
rejection method is considered. Increasing the number of
orders is another way of having a fast roll-off. But as the
number of orders gets increases, the size also increases too.
And this in turn, affects the compactness of the proposed
work. Therefore, in this design, out-of-band transmission
zero is applied. GaAs-IPD technology is used to realize the
proposed UWB-BPF. Because of their integrity ability,
compact size, and small parasitic effects, IPD techniques are
developing fast compared to other standard discrete systems
[10]. Electrons move more quickly in GaAs than in silicon.
Compared to silicon and glass, it has a higher breakdown
voltage [11]. GaAs circuits are very versatile in mobile
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phone and microwave communication applications, as well
as in radar systems [12]. Thus, in this work, we used it to
realize our proposed filter design.
The key contribution of the proposed method is the
ways it approached achieving a higher selectivity factor,
higher fractional bandwidth and good in-band phase
response. Because of the wide frequency range, we faced
slow roll-off problem at transistion region. As a result, the
selectivity factor gets down too. To have a fast transition
region and so as to boost the selectivity factor, a transmission
zero is applied. It is a way of making an infinite impedance
at resonance frequency. Detail is given in sections 3 and 4.
Moreover, cascading HPF and LPF results an UWB-BPF
having higher fractional bandwidth. As shown in the
simulation result Fig. 4c, at 3 dB bandwidth, 2.2-12.3 GHz
bandwidth is obtained. Thus, based on Equation 7, 134.6%
fractional bandwidth performance was achieved. This paper
has four main design sections. A brief introduction about the
UWB-BPF including its usage and impact on the current RF
and Microwave industries is given in the first section. In the
second section, the theoretical and schematic simulations of
LPF and HPF are presented. Thirdly, the schematic design
and simulations of UWB-BPF using non-ideal components
are stated. Finally, the desired UWB-BPF is verified by its
layout simulations. Advanced Design Software (ADS) is
used as a designing software.
2.
Theory and design of HPF and LPF
2.1. Design of Low Pass Filter
The Low Pass Filter denies the higher frequency signal
beyond the cut-off frequency and allows low frequency
signals below its cut-off frequency 𝑓𝑐 . To achieve a bandpass
filter at the proposed frequency range, it is needed to cascade
a low pass filter and high pass filter at 12 GHz and 2 GHz
cut-off frequencies respectively. For N order low pass filter
with cut-off frequency 𝑤𝑐, impedance 𝑍𝑜 and normalized
values 𝑔𝑛, the 𝑛𝑡ℎ series inductor 𝐿𝑛, and shunt capacitor
𝐶𝑛 can be obtained by;
Z0 gn
c
(1)
gn
c Z 0
(2)
Chebyshev is a good choice because of its sharp roll-off at
stop band and its compact size. Therefore, the filter is
designed based on chebyshev prototype. Thus, for 5th order
of 0.5 db ripple Chebyshev filter, 𝑍𝑜 = 50, 𝑓𝑐 = 12 𝐺𝐻𝑧
and the normalized parameters of low pass filter 𝑔𝑛 , the
designing elements 𝐿𝑛 and 𝐶𝑛 can be calculated using
Equations 1 and 2. Where c = 2 * pi * f c .
2.2. HPF design
As explained earlier, high pass filter only allows high
frequency signals from its cut-off frequency, ƒc point. Based
on the specifications given above in low pass filter, the series
capacitor 𝐶𝑛 and parallel inductor 𝐿𝑛 of HPF are given by:
Z0
c g n
1
Cn =
c Z 0 g n
Where f c = 2 GHz then, c = 2 * pi * f c .
Ln =
3.
In this article, the proposed work aims to achieve an
UWB-BPF with pretty low insertion loss, high enough return
loss, compact size, higher than 100% fractional bandwidth
and high selectivity factor at the transition frequency region.
Ln =
Cn =
(3)
(4)
Circuit design of UWB-BPF
As stated previously, the proposed UWB-BPF is
designed by cascading HPF and LPF filters. Fig. 1 is the
schematic design circuit of the proposed UWB-BPF. The
two HPF and LPF circuits are designed based on 5th order
Chebyshev design approach. The LPF has 2 series capacitors
and 3 shunt inductors (5th order). The capacitor values are
calculated by Equation 2 whereas the shunt inductances are
obtained using Equation 1. It rejects a signal with a
frequency beyond the higher cut-off frequency (12 GHz). On
the other hand, HPF is built up with 2 shunt inductors and 3
series capacitors where their values are calculated using
Equations 3 and 4 respectively. It is cascaded with LPF to
form the proposed UWB-BPF by suppressing a signal
having low frequencies beyond the lower cut-off frequency
such that 2 GHz.
The resonated capacitors are to enhance the out band
attenuation at resonance frequency. Because of the wide
frequency range, a slow roll-off problem is noticed at the
transition region. As a result, the selectivity factor gets
affected too. To higher the steepness of the transition region,
and so as to boost the selectivity factor, two ways
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Resonated capacitors
L-network
HPF
LPF
Fig.1 Schematic of the proposed UBW-BPF
of stopband attenuation improvement methods are
considered namely, increasing the filter order and applying
a transmission zero at the region out of passband. But,
increasing the filter order enlarges the size of the device [12].
Thus, in this design, applying the transmission zero point is
considered. It is a way of making an infinite impedance at
resonance frequency. Then, higher insertion loss and lower
return loss will be obtained. This in turn, enhances the
steepness of the transition region at stop band attenuation
area. The LC resonant circuit can be used in series or
shunt during implementation to achieve transmission zero
at resonance [12]. The shunt resonant admittance is shown
in Fig. 3(a) and its corrsponding admitance is given by
Equation 5. According to equation (5), when the admittance
is zero, implies that the circuit is in open state, and this is the
point where resonance occurs. As a result, energy is
completely reflected, creating a
transmission
zero
with pretty high insertion loss. On the otherhand, the series
resonance circuit with zero impedance is depicted in Fig.
3(b). And Equation 6 is its equivalent mathamtical
expression. In this resonance circuit, the ground absorbs all
energy and it act as a short circuit. In this design, since
inductors a little larger than capacitors, 3 capacitors are
connected parallel to each inductor. The circular inductor is
used in this design. As proved in [13] the circular inductor
has lower resistance than the square inductor. The
transmission lines are to obtain the layout.
In filter and other circuit designs, impedance matching
is another important issue [14]. Impedance mismatching
results poor performance circuit design having high insertion
loss and low return loss in the passband region. And this in
turn causes abnormal power loss, biased information and
signal reflection. Maximum power transfer occurs when the
load has an optimum impedance value equal to the complex
conjugate of the source impedance [15].To overcome this
obstacle, we proposed different matching techinques such as
L-network, pi-network, T-network and graphical analysis
(smith chart). In this design, L-network is used to match the
load and source impedances. It has L-shape made from a
series capacitor and shunt inductor. In another word, it’s 2nd
order high pass filter which attenuates lower frequencies and
allows higher frequency signals.
Fig.2 Layout
1
)
L
1
Z = j ( L −
)
C
Y = j ( C −
(a)
(5)
(6)
(b)
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Fig.2 (a) parallel resonance (b) series resonance
4.
Simulation results and analysis
Fig. 4a, is the performance of the proposed UWB-BPF
without the transmission zero and L-network circuits. Input
and output return losses are less than 10 dB. Very low
(b)
(a)
(a)
(d)
(c)
Fig. 3. simulation (a) before transmission zero and L-networks applied (b) after transmission zero and L-networks applied
(c) layout simulation (d) Group delay
selectivity factor was obtanied. However, after the
transmission zero and L-network impedance matching
circuits get applied, at 3 dB pass band, the bandwidth runs
from 2.2 to 12.3 GHz (Fig. 4b). The return loss and
selectivity factor get improved well. This is because of the
transmission zero at resonance frequency and the return loss
impedance matching network. The parallel capacitors are to
enhance the out-band attenuation at resonant frequency.
Equation 5 proves that the circuit admittance gets zero at
resonance point, and of course with infinite impedance. This
implies that all signals get reflected back and in turn, the out
band rejection gets improved as depicted in the Fig. 4b.
Therefore, the transmission zero method is more
advantageous to increase the selectivity factor and since it’s
applied at the point out of the pass band, doesn’t affect the
insertion loss of passband. L-network impedance matching
is added to improve the input return loss. As shown from the
Fig. 4a, the return losse was less than 10 dB. However, after
L-network is applied, it turned out to be 16.2 dB (Fig. 4c).
Fig. 2 is the layout version of the proposed UWB-BPF and
its EM simulation is given in the Fig. 4c. It’s found that the
EM simulation performances of the layout version exactly
agree with that of the schematic one. It also demonstrated a
UWB reject band from 12.3 GHz to more than 18 GHz at 40
dB. As depicted in the simulation Fig. 4c, the resulting
UWB-BPF with 3.23 mm2 compact size provides 78%
selectivity factor (S.F), 1.2 dB insertion loss and 2.2-12.3
GHz bandwidth at 3 dB bandwidth. Thus, based on equation
7, 134.6% fractional bandwidth is obtaned. At 30 dB,
bandwidth runs from 1.1 to 14 GHz. Then, from equation 8,
78% S.F is obtained. The measured group delay of the
proposed work is 0.4–0.09 ns as shown in the Fig. 4d, and its
fluctuation is only 0.31 ns, which shows a good phase
response.
FBW =
BW @ 3 dB
*100
(7)
BW 3.1−10.6 GHz
S .F =
BW @ 3 dB
*100
(8)
BW @ 30 dB
The performance analyses of the proposed filter with state of
the arts are listed in Table1.
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Table 1 comparision with other works
Ref
[1]
Pass
band(GHz
)
2.9-10.9
FB
W(
%)
107
[6]
3.1-10.6
[10]
0.99-2.0
110.
2
70.5
9
134.
6
(S2
1)
Size(
mm2)
GD
(ns)
Publishi
ng year
0.4
9
0.3
5
0.5
3
1.2
6
121.4
8
NA
NA
2021
0.4
2
NA
2020
1.224
[7]
[8]
2022
[This 2.2-12.3
3.23
0.0
2022
work
9
]
GD:group delay; FBW:fractional bandwidth; NA:not available
[9]
[10]
5.
Conclusion
In this paper, a UWB-BPF using HPF and LPF is
designed. Transmission zero and L-matching networks are
applied to enhance the out-band rejection and return loss of
the proposed design respectively. The schematic simulation
performance has been verified by the layout and its EM
simulation results.To conclude, the HPF and LPF cascading
method provides a high FBW BPF and the capacitor
resonating out band rejection enables to obtain fast roll-off
at transistion region.
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