ULTRA WIDEBAND

CHAPTER-I
INTRODUCTION

OVERVIEW OF ULTRA WIDEBAND
Ultra-wide band (UWB) or digital pulse wireless radio communication system has become an area of interest of researchers and scholars. The FCC (federal communications commission) is report order for U.S department for approved commercial use of UWB in 2002, 14 Feb. The Band is used for bandwidth 7500 MHz spectrum are the authorized use of unlicensed devices UWB (Ultra wideband) in the frequency range 3.1- 10.6 GHz band for Indoor and handheld systems. The new possibilities to open up the allocation to develop technologies of UWB (Ultra wide band) from other approaches based on impulse radios. The transmission of UWB (Ultra-wideband) has received significant attention both industry and academia for wireless communications application. The wireless technology of UWB transmits very high digital data rate, using very low power. It is suitable for short range with high-speed data transmission for wireless personal area network (WPAN) application. Low power per mega-bit of data transfer (data over distance 230-feet at very low power less than 0.5 MW). UWB is not considered a technology any more, but, instead, is available spectrum for unlicensed use [1].
A level of emission operates with common digital devices such as pocket calculator, palm pilots and laptop. It is a very low data rate is 802.15.4a IEEE standard and high data rates is 802.15a IEEE standard for industry standards by introducing for ranging UWB technology. It is a system of UWB is DOD (Department of Defense) in different types of system is a commercial use to significant jamming concern. In recent years the UWB radio effort of R&D for the solution of promising are wireless communication to the range of moderate, ranging and short range, high rate. The development, experimentation and investigation are to produce efficient and effective communication system of UWB. A new application found for UWB in the range of moderate wireless communication for the data rate is low by 802.15.4a IEEE standard for the system of the department of defense (DOD) with communication joint and capabilities unique range of UWB. The WPAN technology is 802.15.3a to the environment of indoor and the new sensor of environment is 802.15.4a IEEE standard. It is the system of DOD is different, ranging from dense foliage to urban obstruction is given [2].
Key benefits of UWB as follows:
1. High data rate,
2. Low equipment cost
3. Less power consumption,
4. Multipath immunity
5. Ranging and communication at the same time.

1.2 FCC LIMITS
All radio communication is subject to different laws and regulations about power output in certain frequency bands. This prevents interference to other users in nearby or the same frequency bands. UWB systems cover a large spectrum and interfere with existing users. In order to keep this interference of the minimum FCC and other group of regulatory specify spectral masks for different applications which show the power output allowed for specific frequencies. In fig 1.1 shown the FCC spectral mask for indoor UWB systems. A large contiguous bandwidth of 7.5GHz is available between 3.1 to 10.6 GHz at a maximum power output of-41.3dBm/MHz
It is extremely low power output allowed in the frequency bands 0.96GHz-1.61GHz is due to pressure from representing group service are existing, such as mobile telephony, global positioning system (GPS), and military usage. It is defined FCC in UWB signal to occupy the bandwidth is more than 500Mhz spectrums in the frequency 3.1-10.6 GHz band meets the mask of spectrum by far longest spectrum unlicensed use allocation for the FCC band. It is technology of wireless is defined by the FCC scheme to occupy a fractional bandwidth 20%. Now the transmission bandwidth ‘w’ and the center frequency ‘Fc’ or the bandwidth is 500 MHz. The ruling essence of the PSD (Power spectral density) of UWB signal modulated to satisfy the masks of spectral specified for the regulating spectrum agencies. The PSD is measured to the bandwidth is 1MHz and not to specify the FCC limit. The PSD is proportional to the UWB signal amplitude, bandwidth, and duty cycle. This channel model was mainly aimed for short range applications (i.e. <10m) [2
Figure 1.1 FCC Indoor Limit

1.3 TYPES OF UWB APPLICATION
It is a low-power sensor, low-cost to the promise of UWB application. The accuracy of centimeter is communication and ranging to provide a unique solution of UWB application is as follows:

A Military application
Medical application
Control of home application
Security application
Rescue and search
Including logistics
The supervision of children and family communication

It is related explanation to the application are as follows:

1.3.1. MILITARY APPLICATIONS
As with many wireless communication technologies the military has been the major driving force behind the development of UWB. Radar applications have been developed by the military for many years.

1.3.1 (A) PRECISION ASSET LOCATION SYSTEM (PAL SYSTEM):-
This system has immediate commercial applications, since it is neither an offensive device, but rather a wireless system to improve logistics by knowing the location of containers and other large objects within a navy ship at all times. It is a system consisted of UWB tags which were placed on the devices whose location was to be measured and receivers which were placed at fixed locations in the cargo hold where object location were to be measured the UWB tag consisted of short-pulse transmitter with a measured peak output power of approximately 250mW. The information are burst of consisted of 40bits was repeated in 5-s intervals. The transmitted pulse was approximately bandwidth 400MHz [2].

1.3.2. COMMERCIAL APPLICATIONS
Many consumer electronics companies are actively developing chipsets and wireless applications which will use a UWB physical layer.

1.3.2 (A) HOME NETWORKING AND HOME ELECTRONICS:-
The manufacture of electronics is investigating UWB as a wireless means to connect devices, such as televisions, DVD players, camcorders, and the audio systems to remove some of the wiring clutter in the living room. This is consider to the high definition television are important bit rate needed in excess of 30Mbps at least a few meters over a distance [2].

1.3.2 (B) PRECISION ASSET LOCATION SYSTEM (PAL SYSTEM):-
The PAL system was extended from the military to use in hospitals and factories. The UWB PAL system enables hospital administration to track the utilization of assets and patient flow accurately within the hospital tracking of patients and equipment is expected to increase hospital efficiency. Particularly in the case of terrorist attack or mass disasters, where hospitals see four or five times the normal load of patients.
The National Institute of Standard and Technology (NIST) in the U.S. for precision tracking of robotic vehicles for search and rescue the system will initially be used to evaluate robotic vehicle performance during international search and rescue tournaments [2].

1.3.2 (C) COMMUNICATION RESEARCH LABORATORY:-
In Japan the Communication Research Laboratory (CRL) has recently established a project group devoted to UWB in order to promote the R & D of UWB Technologies.
The aim of this follows:

R & D of all technologies for UWB wireless access systems.
Implementation and experimental investigation of a test bed using a microwave and sub millimeter waveband system
R & D of UWB system in unused high frequency band, such as the sub millimeter waveband over 60 GHz.
Establishment of transmission system based on UWB, with low-cost and high speed transmission over 100 MB/s
Contribution to the standardization of UWB systems, both in Japan and overseas.

1.4 ADVANTAGES OF UWB
UWB technology used to the nature of short duration pulses. It is described in the following points:

The share of ability is frequency spectrum
The channel capacity is large
It is work of ability with signal-to-noise ratio is low
The detection and intercept are low probability
It is a jamming of resistance
The multipath channel are the performance is high
It is a property of superior penetration
It is an architecture of simple transceiver

1.5 AIM OF PROJECT
The project is aimed at the design and development of an Ultra Wideband Band-pass Filter for Indoor and hand held systems for an FCC limit from 3.1 to 10.6 GHz. The designed filter used the parallel coupled microstrip lines, multiple mode resonators (single line resonator) and aperture backed technique for achieving the wide band and good out of band performance. The designed filter is fabricated on the GML substrate. The Design of UWB band-pass Filer for indoor and handheld system is not common and having any difficulties to get the full in-band and out-band performance, some basic requirement to a UWB band pass filter are as follows.

A UWB band-pass filter is used for requirement wave:
The UWB BPF is a full band of primary requirement is listed below:-
1. Ultra bandwidth: It is an example of frequency range 3.1-10.6 GHz (spectrum mask of FCC [1]).
2. It is a loss of low insertion (same as conventional BPF).
3. The group delay is flat and low (the impulse radio system is important).
4. The Filter is out of band performance (the regulation for strongly meet to FCC spectrum).
First is the Ultra bandwidth should be from 3.1 to 10.6 GHz this is about 110 percent fractional bandwidth, for getting such band some broadband design techniques are used. Second is Low insertion loss and less and flat group delay in the whole band from 3.1 to 10.6 GHz, which is impulse system radio are strong to distort for minimum pulse short. The arises of third FCC limit at the end of frequency low. It is restricted limit for the lower spectrum range is 3.1 GHz to the use of intensive frequencies. So it would be a considerable challenge to make a working model. The emphasis has been on the practical work related to realization and testing of the hardware.

CHAPTER-II
LITERATURE REVIEW

There are many ways to design Ultra wideband band-pass filter using electromagnetic band gap (EBG). Chapter two is the review of the literature on filter design. The different filter design is compared and contrasted. The filters are implemented using various schematics like to couple line concepts, end-coupled and resonator based filters. The theory required for the design and implementation of the ultra wideband band-pass filters using EBG is detailed in this chapter are:

By using Parallel-coupled band-pass filter
By using Electromagnetic band gap (EBG)
By using Defected ground structure (DGS)
By using Multiple-Mode Resonators (MMR)
By using Ground Plane Aperture Technique
By using Coplanar Waveguide structure (CPW)

2.1 PARALLEL-COUPLED BAND-PASS FILTER:
Parallel-coupled line band-pass filter was first proposed by Cohn in 1958 and has been considered as one of the most useful band-pass filters over the decades. It is consists of two transmission lines placed parallel to each other’s and in close proximity. In such a case there is a continuous coupling between the electromagnetic field of two lines. Because of the coupling of electromagnetic fields, a pair of coupled lines can support two different modes of propagation. The velocity of propagation is different characteristic impedance of two equal modes for the lines are embedded in a homogeneous dielectric medium. For couples microstrip lines the dielectric medium is not homogeneous. A filter design technique has been presented by the researchers; parallel-coupled line filter is one of the filter topologies in many practical applications due to its matured design procedure and well-documented design parameters [3]. The transmission line can be used to implement various filter circuits. A coupled line can be modeled by two transmission lines and an admittance inverter in between as shown the figure below.

Figure 2.1: a) parallel coupled line b) even and odd mode currents

Figure 2.2: A Coupled Line Structure
Figure 2.2 shows the cross section of a coupled line, widely used in the construction of filters. They support two modes of excitation are as follows.
1. Even mode
2. Odd mode

1. Even Mode:-
In even mode excitation both the microstrip coupled lines have the same voltage potential resulting in a magnetic wall in the symmetry plane.

Figure 2.3: Quasi-TEM, Even Mode of a Pair of Coupled Microstrip Lines

Even mode capacitance is given by,

Where, Cp is the parallel plate capacitance between the microstrip line and the ground plate. Hence,

It is given by the equation,

Where, cf is fringe capacitance,

C’f is the modified fringe capacitance, with the effect of the adjacent microstrip included.

Where,

The even mode characteristic impedance can also be obtained from the capacitance.

Where is the even mode capacitance with air as a dielectric and the effective.

Dielectric constant for even mode is given as:

2. Odd Mode:-
In odd mode the microstrip coupled line is opposite potential. This results into an electric wall at the symmetry.

Figure 2.4: Quasi-TEM, Odd Mode of a Pair of Coupled Microstrip Lines
The resulting odd mode capacitance is given as

and represent fringe capacitance between the two microstrip line over the air and over the dielectric.

Where,

Parallel coupled microstrip filter design uses a cascade of half-wave resonator, each quarter wave parallel coupled to its neighbors. This type of filter yields a narrow to moderate bandwidth. Maximum coupling is obtained between physically parallel microstrip, when the length of the coupled region is λg/4, or some odd multiple thereof. To achieve resonance each resonator element has to be λg/2 in length, or any multiple thereof. The general layout is shown in Fig.2.5.

Figure 2.5 General Microstrip configuration for a five section, Parallel coupled band-pass Filter
For designing a, Parallel coupled band-pass Filter four basic steps are:

1. Determine the one type resonator network, to realize the specification, from the original prototype.
2. From the network parameter evaluate the even and odd ordered characteristic impedance Z00 and Z0E, applicable to the parallel coupled microstrip
3. Relate the values of Z00 and Z0E to microstrip width and separations (w, s), after getting these values use the transmission line calculator for getting w and s.
4. Calculate the whole resonator length 2l, slightly less than λg/2 and therefore of the coupled-section length l which is slightly less than λg/4, here λg is the mid-band and average microstrip line wavelength.

In the following expressions the first coupling structure is that formed by W1, S1, W1 and the final coupling structure consist also of W1, S1, W1 at the opposite end of the filter. The quantities ‘g’ refers to the prototype element values, from the table of Chebyshev prototype [3] the admittance inverter parameters (J) are given by:

For first coupling structure:

For the intermediate coupling structure:

For the final coupling structure:

The fractional bandwidth:

Even and odd mode coupled line impedances Z00 and Z0E these are given by

Where,

Z0 is the system characteristic impedance.

2.2 ELECTROMAGNETIC BAND GAP (EBG):
The conventional EBG structure has a wide band gap and compact nature. The inductor L results from the current flowing through the connecting devices. The gap between the conductor edges of two adjacent cells introduces equivalent capacitance C. Thus a two dimensional periodic LC network is realized which results in the frequency band-gap and the center frequency of the band-gap is determined by the formula,

ω = 1/√LC
From the above equation, it can be seen that in order to achieve an even more compact EBG structure, the equivalent capacitance C and inductance L should be increased. But in the EBG design procedure if the dielectric material and its thickness have been chosen, the inductance L cannot be altered. Therefore, only the capacitance C can be enlarged. It is compared UWB Band-pass filter and another UWB Band-pass filter based on electromagnetic band-gap (EBG) structures. Mainly the focus is on the compactness and performance of the filter design which will be compared with conventional wideband filter. In this EBG structure is investigated and applied to UWB BPFs. The UC–EBG cell is divided into four sectors by the cross line, and added to parallel coupled line to obtain a simple band-pass filter. The performance of the filter is compared with their insertion loss and return loss [4].

2.2.1 TYPES OF EBG STRUCTURE:-
EBG structures are periodic in nature, which may be realized by drilling, cuffing, and etching on the metal or dielectric substrates. They may be formed in the ground plane or over the substrate. On the basis of dimensions EBG structures are categorized as one dimensional (1-D), two dimensional (2-D), and three dimensional (3-D) periodic structures that satisfies Bragg’s conditions, i.e., inter-cell separation (period) is close to half guided wavelength (λg/2). They are capable of forbidding electromagnetic propagation in either all or selected directions [5].

(1) 3-Dimensional Volumetric structure
(2) 2- Dimensional planar surface and
(3) 1- Dimensional Transmission line
The three types of Electromagnetic Band Gap (EBG) structure are presented. This paper analyzes the parametric performance of different factors that influence band gap properties of EBG structures. Planer Electromagnetic Band Gap (EBG) structures are considered very promising in microwave engineering. It is found that EBG structures used to reduce interference, surface wave and mutual coupling. This paper includes three designs of EBG structures, including Fractal shaped, Fork shaped and Spiral shaped. The array of theses EBG structures has been also analyzed to investigate the Band Gap Properties of these structures. Finally the comparison of band gap properties of all three EBG structures has been compared discussed and concluded [5].
2.3 DEFECTED GROUND STRUCTURE:
DGS is an etched periodic or non-periodic cascaded configuration defect in the grounds of a planar transmission line (e.g., microstrip, coplanar and conductor backed coplanar waveguide) which disturbs the shield current distribution in the ground plane cause of the defect in the ground. This disturbance will change the characteristics of a transmission line such as line capacitance and inductance. In a word, any defect etched in the ground plane of the microstrip can give rise to increased effective capacitance and inductance. It is shown in figure 2.6. It focuses on a tutorial overview of the defected ground structure (DGS). The basic conceptions and transmission Characteristics of DGS are introduced and the equivalent circuit models of varieties of DGS units are also presented. Finally, the main applications of DGS in microwave technology field are summarized and the evolutionary trend of DGS is given [6].

Figure 2.6 defected ground structure

2.4 MULTIPLE-MODE RESONATORS:
The two Parallel coupled microstrip line structure sections are introduced at the two sides of a line resonator. Multi-pole band-pass filter with a single line broad and multi-pole band-pass filtering behavior resonator may be realized over an ultra-broad frequency band range from the fundamental to first-order harmonic resonant frequency, if a tightly coupling degree can be achieved. The length of the resonator is approximately λg/2. at the center frequency [7].

2.5 GROUND PLANE APERTURE TECHNIQUE:
An aperture compensation technique is proposed and developed for an effective enhancement of coupling strength in the Parallel coupled Microstrip line (PCML) structure. By the means of forming a wide aperture on the ground plane, an alternative PCML structure is used to achieve a tight coupling by effectively weakening the coupling between each conductor strip and the ground plane. This PCML structure is used to make up a novel multi-pole and ultra wideband band-pass filter. Ground Plane Aperture Technique can be used for manipulation of coupling coefficient between a pair of microstrip resonators, an aperture in the ground plane is placed under the coupling region of each pair of resonators. We propose to use aperture in the ground plane for significant increasing of coupling coefficient between all resonators. In this case microstrip resonator can be considered as quasi-lumped resonators, which give a chance to improve out-of-band rejection of the filter. In [7-8], the back side aperture in the ground plane is formed not only to tighten the coupling degree of coupled lines, but also to realize the specified impedance ratio of side of the central section in the MMR.
2.6 COPLANAR WAVEGUIDE STRUCTURE:
CPW (Coplanar waveguide) consists of a center strip with two ground planes located parallel to and in the plane of the strip i.e. on the same surface of the dielectric slab. The electric and magnetic field configuration for this quasi-static approximation is shown in fig. 2.7. At higher frequencies the mode of propagation in CPW becomes non-TEM because CPW has an elliptically polarized magnetic field in the slots at the air-dielectric interface and becomes suitable for non-reciprocal ferrite devices. In this structure metallization is formed on one side of the substrate alone, each side plane conductor is grounded and the center strip carries the signal thus much less field enters the substrate when compared with Microstrip. The advantage of coplanar line is that the mounting of lumped (active or passive) components in shunt or series configuration is much easier. Drilling or holes or slots through the substrate is not needed [9]. The dimensions of the center strip, the gap, the thickness and permittivity of the dielectric substrate determine the effective dielectric constant eff, characteristic impedance Zc and the attenuation constant  of the line as shown in figure.

Figure 2.7 (a) coplanar waveguide (CPW) geometry (b) Electric and Magnetic Field distributions in CPW

(c) Waveguide structure

CHAPTER-III
DESIGN AND IMPLEMENTATION

3.1DESIGN OF ULTRA WIDEBAND BAND-PASS FILTER USING ELECTROMAGNETIC BAND GAP (EBG) STRUCTURE:
The basic design structure of ultra wideband band-pass filter using electromagnetic band gap as shown in figure 3.1, by attributing three pairs of rectangular shaped impedance-stepped stubs in shunt to a simple micro-strip line which has high impedance. The schematic layout of the parallel coupled line ultra wide band band-pass filters with center frequency 6.85 GHz. It is discussed EBG structure with the unit cell of N=3 are internally embedded into the middle of the Multimode resonator [10, 11], to replace the uniform low impedance section. The two filters consist of the distinctive parts, that is, an EBG-embedded Multimode resonant in the center and two identical λg=4 inter-digital coupled lines on both sides. It needs to be emphasized that all the traditional synthesis design approaches or methodologies are established under the assumption of a narrow pass band and a single-mode operation. There is no reported circuit-model-based synthesis approach available for efficient optimization of such a wideband filter with the 110% bandwidth. Our optimization is carried out in the HFSS software following the three main steps:

The EBG structure 3 unit lines are ultra wide band band-pass filter using center frequency 6.85 GHz. It is composed of the 3 line EBG with microstrip line. At the central frequency of the proposed UWB pass band, the two side lines are same to one quarter-wavelength and the central line are selected equal to one half-wavelength (λg0/2).
And the calculation of width and length of transmission line having the characteristic impedance of 50Ω can be calculated by the equation given in [12] or can be calculated by transmission line calculator.
Gap and width of the coupled line can be calculated by the equations described previously in section 2.1. The ground plane aperture width is approximately λg0/4 and the length of the aperture is λg0/2 + 2 G1 [13]. The structure was analyzed and optimized with EBG.
The parameters are optimized to design a basic EBG structure is listed in Table 3.1.
Table 3.1: Optimized dimensions of the proposed filter

The parallel coupled lines are introduced with a maximum coupling at the central frequency; two ultra-wide band-pass filters based on single stage resonators are designed, implemented. The design of ultra wide band band-pass filter using EBG is four types of design in the given HFSS structure fig. 3.2.

First unit line EBG modified is minimum width 0.4mm, or length0. 7mm and other unit line width 0.8mm, length same as first unit line EBG.
First, second and third unit line EBG modified width 0.4mm, or length 0.7mm used in HFSS software design.
First and last line EBG modified width or length same as the previous section.
First and last line EBG modified is patched are connected to slot 0.25mm height, minimum distance EBG width 0.25mm or length is 0.6mm as compared to given figure 3.2.

Figure 3.2 Proposed ultra wide band band-pass filter using EBG structure
3.1.1 OPTIMIZATION OF THE FILTER:
Figure 3.1 illustrates the schematic design of ultra wide band band-pass filter with center frequency 6.85 GHz. It is composed of a non-uniform multiple-mode resonator (MMR) in the central part and the 3 unit line EBG structure is multiple mode resonators. The optimization of the filter by change in different EBG structure is as follows:

The first unit line EBG modified rectangular EBG patch is connected parallel to the two slot height 0.25mm and 0.5mm as shown in figure 3.1. The two coupled-line sections on either side of the MMR as shown in Fig.3.1. It is a center part of MMR filter are two parallel-coupled microstrip lines on either side. Instead of a single quarter wavelength long parallel-coupled line, we have cascaded two such lines on either side of the MMR. It makes the overall length of the filter is one and half guided wavelength long as shown in Fig. 3.3. The slot width of EBG is approximately λgo/4 and it is one half wavelengths long. The structure was analyzed and optimized with HFSS [14] [appendix].
The parameters of optimized are listed in Table 3.2. MMR introduces the seven transmission poles. It is useful for making the ultra wideband filter design successes. As shown in figures are as follows:

The Ist line, IInd line and IIIrd line EBG of the length 3mm as shown in figure 3.3 and height 2.6mm.
The patch length for First line EBG are 0.7mm and width of 0.4mm, second or third line EBG length is 0.7mm and width of 0.8mm.
The slot height 0.25mm and 0.5mm for first line and second or third line slot height are 0.5mm is connected to patch.
The distance of parallel coupled line 4.25mm.
The total overall length is 19.7mm
The length of microstrip line 11.2mm, strip width 0.1mm and gap width 0.05mm.
The gap width for slot line EBG is 0.45mm.

The implement for three unit lines EBG modified rectangular shapes are connected to the slot width 0.25 and 0.5mm as shown figure 3.4. The slot width of EBG is approximately λgo/4 and it is one half wavelength as long as shown in the figure are as follows:
The Ist line, IInd line and IIIrd line EBG of the length 3mm as shown in figure 3.4 and height 2.6mm.
The patch length is 0.7mm and patch width 0.4mm.
The slot height 0.25mm and 0.5mm are connected to patch.
The distance of parallel coupled line 4.25mm.
The total overall length is 19.7mm.
The length of microstrip line 11.2mm, strip width 0.1mm and gap width 0.05mm.
The gap width for slot line EBG is 0.45mm.
The implement of first and last unit line EBG modified rectangular shapes are connected to the slot width 0.25 and 0.5mm as shown figure 3.5. The slot width of EBG is approximately λgo/4 and it is one half wavelength as long as shown in the figure are as follows:

The Ist line, IInd line and IIIrd line EBG of the length 3mm as shown in figure 3.5 and height 2.6mm.
The patch length is 0.7mm and patch width 0.4mm.
The slot height 0.25mm and 0.5mm are connected to patch.
The distance of parallel coupled line 4.25mm.
The total overall length is 19.7mm.
The length of microstrip line 11.2mm, strip width 0.1mm and gap width 0.05mm.
The gap width for slot line EBG is 0.4
The implement of first and last line EBG modified rectangular shapes are connected to the slot width 0.25 and 0.5mm as shown figure 3.6. The slot width of EBG is approximately λgo/4 and it is one half wavelength as long as shown in the figure are as follows:

The Ist line, IInd line and IIIrd line EBG of the length 2.7mm as shown in figure 3.6 and height 2 mm.
The patch length is 0.6mm and patch width 0.25mm.
The slot height 0.25mm and 0.5mm are connected to patch.
The distance of parallel coupled line 4.25mm.
The total overall length is 19.4mm.
The length of microstrip line 10.9mm, strip width 0.1mm and gap width 0.05mm.
The gap width for slot line EBG is 0.45mm.

3.2 DESIGN OF ULTRA WIDEBAND BAND PASS FILTER USING EBG STRUCTURE WITH DEFECTED GROUND:

The filter design consists of two main part divided in fig.3.7 is as follows:
Top view
Bottom view
It is proposed geometry structure of UWB BPF using EBG with DGS (Defected ground structure) as shown in figure 3.7. It is composed a UWB BPF using EBG are two coupled resonator step impedance to open loop DGS as a BPF .It is part of BPF as a DGS.
It is a double step impedance resonator is simulated HFSS software design on the same side of microstrip Input/output port.
The three unit EBG line and slot line located to the ground structure defected as shown in figure 3.7

Fig 3.7 EBG structure with DGS layout

The Ist line, IInd line and IIIrd line EBG of the length 3mm as shown in figure 3.7 and height 2 mm.
The patch length is 0.7mm and patch width 0.25mm.
The slot height 0.25mm and 0.5mm are connected to patch.
The distance of parallel coupled line 4.25mm.
The total overall length is 19.7mm.
The length of microstrip line 11.2mm, strip width 0.1mm and gap width 0.05mm.
The DGS (defected ground structure) is length 11.2mm and width 2.2mm.
The gap width for slot line EBG is 0.45mm.

The parameters optimized are listed in Table 3.6.

The dimension are listed in Table 3.6 in fig 3.7
Dielectric substrate Thickness of substrate: 0.635 mm, r: 10.8, loss tangent 0.0023, and Metal film:

CHAPTER-IV
SIMULATION/EXPERIMENTATION

The different type of designing EBG structures is simulated using the HFSS software. The analysis of the result is as follows:

4.1 ANALYSIS OF SIMULATION RESULT:

The analysis of simulation result are as follows:-

In this section ultra wide band band-pass filter using EBG embedded Multimode resonator are design, implement and simulation used for this HFSS software. The proposed structure shown in Fig.3.1 is optimized on a substrate with relative permittivity ∈ r = 10.8, and thickness h = 0.635mm. Simulated results of optimization in the width of the unit cell EBG structure by transversely attaching a pair of uniform open-circuited stubs in the middle of a microstrip line section of length (T1) is shown in Fig.3.2, from these results we can easily understand the effect of change are 3 line EBG structure is connected to the slot with microstrip line, the band is increasing with increase in width but the S11 is increasing and crossing the -11.50dB. So we can see from this analysis, the best results found at W=3mm, S21 is almost same but the change in S11 is considerable, the simulated results at W=2. 528mm is shown in Fig.3.1 along with indoor and outdoor limits which specified by FCC [1]. The simulated result shows insertion loss is almost 0.01dB, but the upper and lower cutoff is not sharp and not following the FCC limit.

It can be seen that the out of band performance of this filter is not good. The simulated bandwidth of the filter is from 2.72GHz to 12.6GHz (Fig.4.1). This result is not satisfying the UWB bandwidth and total band is only 10.02 GHz, whereas UWB bandwidth should be 8.1 GHz. So this filter is not fulfilling the requirement of bandwidth of the FCC, but it is a good wideband filter. For widening the band and sharpening the lower and upper cutoff of the filter using the cascading of the whole section and these two similar sections are connected by the single line resonator. This modified filter is proposed are the next step.

Figure 4.1 simulated result

The new filter concept and demonstrate its performance, the filter has been designed and developed at center frequency 6.85 GHz. Effect of varying physical dimensions like width and length of first line patch and height of slot, length and width of second or third line patch and length and width of the single line resonator was also studied, table 2.In Fig 4.2 shows Simulated results for different patch length with fixed first line EBG structure width W=0.4mm,second or third line width =0.8.mm,length of 3 cell of EBG structure L=0.7mm and coupled line length is 4.25mm and single line resonator is half wavelength long as shown in figure 3.2

It shows when length increase or decrease from length (λg0/2 + 2G1=L), S21 decreases, and S11 is going to increase. From the analysis of length we can set the length of microstrip line is equal to the L=11.2 mm and from the fig. 4.2 we can also analyze the insertion loss in the whole band has been decreased. Then the next analysis is the effect of first line EBG width with the fixed microstrip line length of 11.2mm and fixed coupled line as shown in fig 4.2, it shows when width decreases from 3.40 to 0.4mm the S21 (transmission coefficient) is decreased, but not linear and S11 (reflection coefficient) is increased and center frequency is also decreased but this decreases is very small. And when width increases from 3.40 to 0.8mm the S11 is increasing and S21 is nearly same as for 3.40mm width.

Figure 4.2 simulated result

The major effects shown when First line width and slot connected to EBG changes, when EBG line width increases and other dimension are fixed then the total band is decreases but there is same center frequency 6.85 and S11 is almost same as for the L=11.2mm and frequency shifted from 3.4 to 11.4 GHz, and band crosses the limit of FCC, so selection of parallel-coupled line length L=4.25mm is good agreement shown in Fig 4.2.When single line resonator length is 11.2mm but it is a good wide band and it having the sharp upper and lower cutoff and having good out of band performance. Some changes have been considered in this first line EBG at the time of simulation the width of the EBG patch is decreased from 0.8 to 0.4 mm and slot connected to patch 0.25mm height, then it performs better, its simulated results are shown in fig 4.2 along with the indoor and outdoor limits specified by the FCC. This shows the line resonator behave like a multiple mode resonator when it is half wavelength long. Measured and simulated results are shown in fig 4.2, the bold line shows the measured result and the red line shows the simulated result. The simulated results are better than the measured one. The S11 in less than -10dB in the measured results and the band is also wide and having well out of band performance.

It can be seen that the out of band performance of this filter is not good. The simulated bandwidth of the filter is from 3.4GHz to 11.4GHz (Fig.4.2). This result is not satisfying the UWB bandwidth and total band is only 8GHz whereas UWB bandwidth should be 5.1GHz. So this filter is not fulfilling the requirement of bandwidth of the FCC, but it is a good wideband filter. For widening the band and sharpening the lower and upper cutoff of the filter using the cascading of the whole section and these two similar sections are connected by the single line resonator. This modified filter is proposed in the next step.

The second filter concept and demonstrate its performance, the filter has been designed and developed at center frequency 6.85 GHz. Effect of varying physical dimensions like width and length of first, second or third line patch and height of slot, changes length and width of the single line resonator was also studied, table 3.In Fig 4.3 shows Simulated results for different patch length with fixed first, second or third line EBG structure width changes W=0.4mm,length of 3 cell of EBG structure L=0.7mm, band gap EBG is 0.45mm and coupled line length is 4.25mm and single line resonator is half wavelength long as shown in figure.3.3

First of all, introduce rectangular EBG patch structure are connected to 3 cell EBG structure and keep top surface is same as discussed in section 4.1. The changes in the response are shown in fig. 4.3, it shows S21 is sharpest at the upper cutoff in comparison with the slot at the ground and S11 is lower than approximately -10dB from (3.5 to 12.3GHz). It can be seen that the out of band performance of this filter is not good. The simulated bandwidth of the filter is from 3.5GHz to 12.3GHz (Fig.4.3). This result is not satisfying the UWB bandwidth and total band is only 7.7GHz, whereas UWB bandwidth should be 8.8GHz. So this filter is not fulfilling the requirement of bandwidth of the FCC, but it is a good wideband filter. For widening the band and sharpening the lower and upper cutoff of the filter using the cascading of the whole section and these two similar sections are connected by the single line resonator. This modified filter is proposed in the next step.

Figure 4.3 simulated result

The third filter concept to the performance of HFSS software designed and developed to center frequency 6.85 GHz. It is effectively of verifying physical dimensions like width and length of first, and the third line EBG patch is minimum for the basic structure. The height of slot changes is 0.25 mm and length and width of the single line resonator are l=11.2 mm length or width 0.1 mm. In table 4 Fig 3.4 shows the HFSS Simulated results Fig 4.4 for same EBG patch length with first, second or third line EBG structure as shown in figure 3.4. The 3 unit cells of EBG structure length are L=3mm, band gap EBG is 0.45mm and Parallel-coupled line length is 4.25mm and single line resonator is the half wavelength as shown in figure. 3.4

First of all, introduce rectangular EBG patch structure are connected to 3 cell EBG structure and keep top surface is same as discussed in section 4.1. The changes in the response are shown in fig. 4.4, it shows S21 is sharpest at the upper cutoff in comparison with the slot at the ground and S11 is lower than approximately -10dB from (3.5 to 12.3GHz). It can be seen that the performance of this filter is good. The simulated bandwidth of the filter is from 3.3GHz to 10.6GHz (Fig.4.4).

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