International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering

International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering

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ISSN ONLINE(2278-8875) PRINT (2320-3765)

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Non periodic EBG unit cell Structure based UWB Band pass filter

Sridhar Raja. D
Asst. Professor, Department of Electronics & Instrumentation, Bharath university, Chennai – 600073, India
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International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering

Abstract

In this paper microstrip bandpass filter as been proposed for UWB application using uniplanar compact– electromagnetic bandgap (UC–EBG) are used here to improve passband obtained in UWB region,also to improve the good out-of-band performances and the EBG structure to reduce the overall size of the filter



Keywords
Bandpass filter, electromagnetic bandgap (EBG), ultra wideband (UWB), wideband filter.

INTRODUCTION
The Ultra-wideband (UWB) technology is being reinvented recently with many promising modern applications. In particular, the UWB radio system has been receiving great attention from both academy and industry since the Federal Communications Commission (FCC) release of the frequency band from 3.1 to 10.6 GHz for commercial communication on applications in February 2002[1]. In an UWB system, an UWB band pass filter (BPF) is one of the key passive components to keep the spectrum of the signals to meet the FCC limits, or used in the UWB pulse generation and reshaping.
In such a system, an UWB filter is one of the key components, which should exhibit a wide bandwidth with low insertion loss over the whole band. In order to meet the FCC limit, good selectivity at both lower and higher frequency ends and flat group-delay response over the whole band are required .Over the last years, thedesign of wide and ultra-wide Bandpass filters is generating a great interest due to the fast development of broadband wireless communication systems. Traditional methods to implement ultra-wide bandpass filters usually introduce spurious bands .These undesired bands become an important drawback for ultra-wide bandpass filters performance due to their proximity to the pass-band of interest.
The recent research and development practical applications of EBG structures have improved realizing compact EBG structures filters. EBG structure recently is developed rapidly due to its unique properties to suppress the propagation of surface wave in microstrip filters. EBG structure is also known as a high impedance surface due to its ability to suppress the propagation of surface wave at the certain operational frequency. This structure is also has ability to block the effect of mutual coupling effect in array application.

FILTER THEORY
In designing a filter, the following important parameters are generally considered.
• Pass bandwidth
• Stop band attenuation and frequencies
• Input and output impedances
• Return loss
• Insertion loss
• Group delay
The most important parameters among the above is the amplitude response given in terms of the insertion loss Vs frequency characteristics. Let Pi be the incident power at the filter input , Pr is the reflected power, PL is the power passed on to the load. The insertion loss of the filter is defined by,
image
Where PL=Pi - Pr, if the filter is lossless and Г is the voltage
reflection coefficient given byimage
The return loss of the filter is defined by
image
which quantifies the amount of impedance matching at the input port.
The group delay is important for the multi-frequency or pulsed signals to determine the frequency dispersion or deviation from constant group delay over a given frequency band and is defined by
image
Where Фt is the transmission phase.

PROPOSED EBG STRUCTURE
The conventional EBG structure has a wide band-gap and compact nature. The inductor L results from the current flowing through the connecting via. 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
image
From 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 .
Below fig.1 shows the proposed EBG structures for filter design.

DESIGN OF PROPOSED UWB FILTERS
In this proposed model two uwb band pass filter are designed and simulated also compared with performance of EBG Embedded Multi Mode Resonator BPF. All BPFs are fabricated with thickness of 0.635 mm on an RT/Duroid substrate with a dielectric constant of10.2 . The schematics of uniplanar compact–EBG (UC–EBG) structure and a periodic UC–EBG (PUC–EBG) structure are shown in fig 2. The inter digital coupled lines used in all BPFs have a coupling peak at the center frequency of 6.85 GHz. Simple EBG Embedded Multi Mode Resonator UWB BPF is also shown in fig 2. There simulation as been done using ADS Momentum simulator

SIMULATION RESULTS
image
image

CONCLUSION
In this, EBG structures are investigated and applied to UWB BPFs. The UC–EBG cell ,used here as improved passband obtained in UWB region,also improving the good out-of-band performances and the EBG structure to reduce the overall size of the filter. There results have been compared by simulated using ADS Momentum simulator.

Figures at a glance
Figure Figure
Figure 1 Figure 2

References