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  1. 1. Mr.Bhushan R. Vidhale, Dr. M.M.Khanapurkar / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.2340-2345 Design of Low Cost and Efficient Strip Line Band Pass Filter for Bluetooth Application. Mr.Bhushan R. Vidhale, Dr. M.M.Khanapurkar Electronics and Telecommunication Department, G.H. Raisoni College of Engineering, NagpurAbstract— In this paper, low cost and efficient strip zero frequency, such as a signal that comes out of aline band pass filter is implemented. The new band pass filter.structure does not only reduce the size of the An ideal bandpass filter would have a completelyfilters, but also provides good gain for pass band flat passband (e.g. with no gain/attenuation throughout)and better attenuation for the stop band and would completely attenuate all frequenciescharacteristics. A designed filter provides outside the passband. Additionally, the transition outbandwidth which is needed for Bluetooth of the passband would be instantaneous in frequency.transmission. It can be mounted on Bluetooth In practice, no bandpass filter is ideal. The filter doestransceiver system which has broad application not attenuate all frequencies outside the desiredarea. The designed band pass filter has 2.4 Ghz of frequency range completely; in particular, there is afrequency band and has about 150 MHz of region just outside the intended passband wherebandwidth. The design of filter has been done on frequencies are attenuated, but not rejected. This issimulation software and successfully tested on known as the filter roll-off, and it is usually expressedspectrum analyzer. in dB of attenuation per octave or decade of frequency. Generally, the design of a filter seeks to make the roll-Keywords— Band pass filter, Strip line, Bluetooth. off as narrow as possible, thus allowing the filter to perform as close as possible to its intended design.I. INTRODUCTION Often, this is achieved at the expense of pass-band or Filters of some sort are essential to the stop-band ripple.operation of most electronic circuits. It is therefore inthe interest of anyone involved in electronic circuitdesign to have the ability to develop filter circuitscapable of meeting a given set of specifications. In circuit theory, a filter is an electricalnetwork that alters the amplitude and/or phasecharacteristics of a signal with respect to frequency.Ideally, a filter will not add new frequencies to theinput signal, nor will it change the componentfrequencies of that signal, but it will change therelative amplitudes of the various frequencycomponents and/or their phase relationships. Filtersare often used in electronic systems to emphasizesignals in certain frequency ranges and reject signalsin other frequency ranges. Such a filter has a gainwhich is dependent on signal frequency. Fig.1 A diagram showing magnitude transfer A band-pass filter is a device that passes function versus frequency for a band-pass filterfrequencies within a certain range and rejects(attenuates) frequencies outside that range. An example of an analogue electronic band-passfilter is an RLC circuit (a resistor–inductor–capacitorcircuit). These filters can also be created by combininga low-pass filter with a high-pass filter. Bandpass is an adjective that describes a typeof filter or filtering process; it is frequently confusedwith passband, which refers to the actual portion ofaffected spectrum. Hence, one might say "A dualbandpass filter has two passbands." A bandpass signalis a signal containing a band of frequencies away from Fig.2 A medium-complexityexample of a Band Pass Filter band-pass filter 2340 | P a g e
  2. 2. Mr.Bhushan R. Vidhale, Dr. M.M.Khanapurkar / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.2340-2345 a) Stripline be routed from one part of the assembly to another Stripline is a transverse electromagnetic with minimal distortion, and avoiding high cross-talk(TEM) transmission line medium, that was invented and radiation.by Robert M. Barrett of the Air Force Cambridge Microstrip is very similar to stripline andResearch Centre in the 1950s. coplanar waveguide and it is possible to integrate all A stripline circuit uses a flat strip of metal three on the same substrate.which is sandwiched between two parallel ground The electromagnetic wave carried by aplanes. The insulating material of the substrate forms a microstrip line exists partly in the dielectric substrate,dielectric. The width of the strip, the thickness of the and partly in the air above it. In general, the dielectricsubstrate and the relative permittivity of the substrate constant of the substrate will be different (and greater)determine the characteristic impedance of the strip than that of the air, so that the wave is travelling in anwhich is a transmission line. As shown in the diagram, inhomogeneous medium. In consequence, thethe central conductor need not be equally spaced propagation velocity is somewhere between the speedbetween the ground planes. In the general case, the of radio waves in the substrate, and the speed of radiodielectric material may be different above and below waves in air. This behaviour is commonly describedthe central conductor. by stating the effective dielectric constant (or effective To prevent the propagation of unwanted relative permittivity) of the micro strip, this being themodes, the two ground planes must be shorted dielectric constant of an equivalent homogeneoustogether. This is commonly achieved by a row of vias medium (i.e. one resulting in the same propagationrunning parallel to the strip on each side. velocity). Like coaxial cable, stripline is non-dispersive, andhas no cutoff frequency. Good isolation betweenadjacent traces can be achieved more easily than withmicrostrip. Stripline provides for enhanced noiseimmunity against the propagation of radiated RFemissions, at the expense of slower propagationspeeds. b) Microstripline Microstrip is a type of electrical transmissionline which can be fabricated using printed circuit Fig.3 Micro strip separated from ground plane byboard technology, and is used to convey microwave- a dielectric materialfrequency signals. It consists of a conducting stripseparated from a ground plane by a dielectric layer II. LITERATURE SURVEYknown as the substrate. Microwave components suchas antennas, couplers, filters, power dividers etc. can A paper on ―An Interdigital Band pass Filterbe formed from microstrip, the entire device existing Embedded in LTCC for 5-GHz Wireless LANas the pattern of metallization on the substrate. Applications‖ given by Gangqiang Wang, SeniorMicrostrip is thus much less expensive than traditional Member, IEEE, Minh Van, Fred Barlow, Member,waveguide technology, as well as being far lighter and IEEE, and Aicha Elshabini, Fellow, IEEE [1]more compact. Microstrip was developed by ITT presented a compact interdigital stripline bandpasslaboratories as a competitor to stripline (first published filter embedded in low temperature cofired ceramicby Grieg and Engelmann in the December 1952 IRE for 5-GHz wireless LAN applications, includingproceeding.). design, simulation, fabrication, and measurements. The disadvantages of microstrip compared The filter measures 8 mm 7 mm 1.1 mm and exhibitswith waveguide are the generally lower power an insertion loss of 3.6 dB, is turn loss of 20 dB, and ahandling capacity, and higher losses. Also, unlike 212-MHz pass band with the midband frequency atwaveguide, microstrip is not enclosed, and is therefore 5.28 GHz. The filter is highly reproducible with goodsusceptible to cross-talk and unintentional radiation. tolerance. A low noise amplifier (LNA) built on the For lowest cost, microstrip devices may be top of the LTCC substrate with an embedded filter hasbuilt on an ordinary FR-4 (standard PCB) substrate. the same bandwidth and midband frequency as thoseHowever it is often found that the dielectric losses in of the filter. Using this filter and an integrated chip, aFR4 are too high at microwave frequencies, and that small RF front-end receiver has been achieved.the dielectric constant is not sufficiently tightly A paper on ―Cross-Coupled Suspendedcontrolled. For these reasons, an alumina substrate is Stripline Trisection Bandpass Filters with Open-Loopcommonly used. Resonators‖, given by,E.Hanna, P.Jarry, Senior On a smaller scale, microstrip transmission Member, IEEE, E.Kerherve, Member, IEEE,[2]lines are also built into monolithic microwave presented two bandpass trisection filters withintegrated circuits.Microstrip lines are also used in asymmetrical characteristics in the suspendedhigh-speed digital PCB designs, where signals need to substrate technology. The open-loop resonators are 2341 | P a g e
  3. 3. Mr.Bhushan R. Vidhale, Dr. M.M.Khanapurkar / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.2340-2345based on a meandered half-wavelength line topology validate the feasibility. Low temperature co-firedthus allowing a significant size reduction. The design ceramic (LTCC) technology is employed toof these filters follows two steps: A synthesis based on manufacture the filters. Experimental results of thethe extraction of the general cross-coupled folded two manufactured filters are presented. The effects ofnetwork parameters and coupling matrix, then the LTCC manufacturing procedure on the filterrelationship between the resonators’ spacing’s and performance are also discussed.coupling coefficients is obtained thanks to fullwave A paper on ―Quasi-Lumped—Open-Loopelectromagnetic simulations. Transmission zeros on Suspended Stripline Bandpass Filters― ,given by,both sides of the pass band can be achieved. Atallah Balalem,Wolfgang Menzel, and Abbas Omar,Chair of Microwave and Communications A paper on ―Multilayered Stripline Engineering, University of Magdeburg,Germany,[6]Interdigital-Hairpin Bandpass Filters with Small-Size presents a combined quasi-lumped-openloop resonatorand Improved Stopband Characteristics‖, given (QL-OLR) is introduced and applied for filter design.by ,Yani Mu1, Zhewang Ma2, and Deming Xu1 [3] The resonator can have single and dual-band behavior.School of Communication and Information Two bandpass filters as well as two dual-bandEngineering, Shanghai University,China presents a bandpass filters have been designed, fabricated, andmultilayered stripline interdigital-hairpin bandpass tested, that consist of two resonators each. Thefilters are proposed. The new structure can not only bandpass filters show the behavior of four return lossreduce the size of the filters, but also provide poles (fourth order filter), and by slitting thesetransmission zeros to improve the stopband resonators a dual-band bandpass filter can be achievedcharacteristics. As design examples, a four-pole and (each band has two return loss poles). Transmissionan eight-pole bandpass filters using the proposed zeroes can be easily introduced into the filter responsestructures are provided. Moreover, the novel four-pole as well by utilizing the properties of both quasi-bandpass filter is fabricated and measured. The lumped and open-loop resonators.experimental results agree very well with the A paper on ― A Fully Integrated Scanning Receiversimulated data. Array ―,given by,Wolfgang Menzel, Ziqiang A paper on ―Design of a Tri-Section Folded Tong,Microwave Techniques, University ofSIR Filter‖,given by, D. Packiaraj, M. Ramesh, and A. Ulm,Germany,[7] presents, an integrated antennaT. Kalghatgi, Member, IEEE, [4] presents the design receiver array is presented. The RF signal is receivedof a suspended substrate stripline bandpass filter with by open waveguide ports connected to finline mixers.relocatable second pass band using tri-section folded A chain of suspended stripline bandpass filters is usedstepped impedance resonators (TFSIRs). Resonance as LO feed network where phase shifting occurs as aconditions for the TFSIR in terms of impedance ratios function of frequency. Combining the IF signal in ahave been derived. Location of the second pass band fixed equal-phase network, the antenna arrayas a function of impedance ratios (of TFSIRs) has characteristic is scanned varying the LO frequencybeen studied in detail. Experimental results of a filter from -35° to +35° while the RF frequency is keptdesigned at 2.95 GHz with 31% bandwidth have been constant. The overall very compact arrangement iscompared against the simulation results. Index integrated on a single substrate and placed in aTerms—Bandpass filter (BPF), suspended substrate compact metal mount.stripline (SSS), tri-section folded stepped impedanceresonator (TFSIR). III. MATERIAL USED A paper on ― Miniature Broadband Bandpass Material with Good Dielectric Constant (FR4)Filters Using Double-Layer Coupled Stripline FR-4 (or FR4) is assigned to glass-reinforced epoxyResonators ―,given by,Yunchi Zhang, Student laminate sheets, tubes, rods and printed circuit boardsMember, IEEE, Kawthar A. Zaki, Fellow, IEEE, (PCB). FR-4 is a composite material composed ofAndrew J. Piloto, and Joseph Tallo, [5] presents a woven fibreglass cloth with an epoxy resin binder thatdouble-layer coupled stripline resonator structure is is flame resistant (self-extinguishing).introduced to realize miniature broadband bandpass FR-4 glass epoxy is a popular and versatile high-filters. Filters with relative bandwidth up to 60% and pressure thermo set plastic laminate grade with goodsize less than 8 8 ( is wavelength at the midband strength to weight ratios. With near zero waterfrequency; is the substrate height, which is much absorption, FR-4 is most commonly used as ansmaller than 8) can be fulfilled using such resonators. electrical insulator possessing considerableTwo possible filter configurations are proposed in this mechanical strength. The material is known to retainpaper: combline and interdigital. The filter synthesis its high mechanical values and electrical insulatingprocedure follows the classical coupling matrix qualities in both dry and humid conditions. Theseapproach that generates very good initial responses. attributes, along with good fabrication characteristics,Optimization by the mode-matching method and fine lend utility to this grade for a wide variety of electricaltuning in Ansoft’s High Frequency Structure and mechanical applications.Simulator are combined to improve the filter NEMA is the regulating authority for FR-4 andperformance. Two filter design examples are given to other insulating laminate grades. Grade designations 2342 | P a g e
  4. 4. Mr.Bhushan R. Vidhale, Dr. M.M.Khanapurkar / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.2340-2345for glass epoxy laminates are: G10, G11, FR4 and 120°CFR5. Of these, FR4 is the grade most widely in use Youngs Modulus – 3.5x10^6 psitoday. G-10, the predecessor to FR-4, lacks FR-4s LWself-extinguishing flammability characteristics. Hence, Youngs Modulus – 3.0x10^6 psiFR-4 has since replaced G-10 in most applications. CW FR-4 epoxy resin systems typically employ CTE x-axis 14ppm/°Cbromine, a halogen, to facilitate flame-resistant CTE y-axis 13ppm/°Cproperties in FR-4 glass epoxy laminates. Some CTE z-axis 175ppm/°Capplications where thermal destruction of the material Poissons Ratio – LW 0.136is a desirable trait will still use G-10 non flame Poissons Ratio – CW 0.118resistant. FR-4 is the primary insulating backbone uponProperties:- which the vast majority of rigid printed circuit boards Typical physical and electrical properties of (PCBs) are produced. A thin layer of copper foil isFR-4 are as follows. LW (length wise, warp yarn laminated to one, or both sides of an FR-4 glass epoxydirection) and CW (cross wise, fill yarn direction) panel. These are commonly referred to as "coppercladrefer to fiber orientations in the board that are laminates."perpendicular to one another. FR-4 copper-clad sheets are fabricated with TABLE I circuitry etched into copper layers to produce printed MATERIAL SPECIFICATIONS circuit boards. More sophisticated and complex FR-4 printed circuit boards are produced in multiple layers,Parameter Value Alternate aka "multilayer circuitry". unitsSpecific 1850 kg/m³ IV. METHODOLOGYGravity/Density Initially survey has been done for fine quality pcb material having high dielectric constant and highWater Absorption -.125" value of characteristic impedance. Higher values of < .10 % dielectric constant ensure precise results and properTemperature Index 140 °C 284 °F wavelength propagations through the band pass filter.Rockwell Hardness 110 M scale As design consideration is for low cost so Finally,Bond Strength > 1000 kg 2200 lbs after a deep survey selected a FR4(having dielectricFlexural Strength- > 448 MPa 65,000 psi constant = 4) PCB material. For perfect results oneLW-A-.125" can use RT Duroid pcb material having dielectricFlexural Strength- > 345 MPa 50,000 psi constant equal to 10.But Duroid is quite costlyCW-A-.125" compared to FR4 and is rarely available in India.Tensile Strength > 310 MPa 45,000 psi Hence, FR4 was the best option.(.125") LW After designing the schematic of the band pass filterIzod Impact > 54 Nm/m we fabricated the layout on double sided PCBStrength-LW (FR4).One side of pcb contains designed copper tracksIzod Impact > 44 Nm/m 8 ft-lbs/in and the other side is used as ground.Strength-CWCompressive > 415 MPa 60,000 psiStrength-FlatwiseDielectric > 50 kVBreakdown-ADielectric > 50 kVBreakdown-D48/50Dielectric strength 20 kV/mmPermittivity-A 4.8Permittivity-D24/23 4.8Dissipation Factor-A 0.017Dissipation Factor- 0.018D24/23Dielectric constant 4.70 max,permittivity 4.35 @ 500 MHz, 4.34 @ 1 GHzGlass Transition Can vary, butTemperature is over 2343 | P a g e
  5. 5. Mr.Bhushan R. Vidhale, Dr. M.M.Khanapurkar / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.2340-2345 Fig 6: simulation output window Here graph of S(1,1) represents nature of INPUT RETURN LOSS which should be less at desired frequency i.e. 2.4 GHz and S(2,1) shows nature of TRANSMISSION COEFFICIENT (i.e. FORWARD GAIN) which is maximum at the desired frequency of 2.4 GHz. After successfully finishing of layout and fabrication of PCB testing established the testing setup Fig 4: Design Flow includes microwave frequency generator, detector and spectrum analyzer.The setup is as given below Then pcb based female SMA connector is attached to both the ends of the strip. At last, the setup was assembled that includes Spectrum analyzer, Microwave generator, male SMA connector, Detector and BNC cable.The snapshot of complete setup is shown below. Proper results were obtained from the spectrum analyzer and Band pass filter using stripline technology was prepared successfully. V. SIMULATIONS AND TESTING RESULTS The simulation setup and results for the bandpass filter are given below. Circuit design and simulation has been done on ADS schematic window and Layout design of filter is performed on Layout Fig 7: Testing Setup window of ADS. The testing results are examined with the help of spectrum analyzer the results is shown in fig.8Fig 5: simulation setup on circuit window The results for simulation are as follows Fig 8: Result on Spectrum analyzer Figure shows testing results of 2.4 GHz Stripline Band Pass Filter on Spectrum Analyser’s seen from figure graph shows minimum attenuation of around 25 dB at desired frequency of 2.4 GHz and much more attenuation at other frequencies.This 2344 | P a g e
  6. 6. Mr.Bhushan R. Vidhale, Dr. M.M.Khanapurkar / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue4, July-August 2012, pp.2340-2345implies that it is easily allowing the centre frequency Bandpass Filters with Small-Size andof 2.4 GHz to pass through it and restricts other Improved Stopband Characteristics‖2005.frequencies. [4] D. Packiaraj, M. Ramesh, and A. T. Kalghatgi, Final view of stripline bandpass filter after Member, IEEE, ―Design of a Tri-Sectioncompletion of framing is as follows Folded SIR Filter‖2005. [5] Yunchi Zhang, Student Member, IEEE, Kawthar A. Zaki, Fellow, IEEE, Andrew J. Piloto, and Joseph Tallo― Miniature Broadband Bandpass Filters Using Double- Layer Coupled Stripline Resonators ―,2006. [6] Atallah Balalem,Wolfgang Menzel, and Abbas Omar―Quasi-Lumped—Open-Loop Suspended Stripline Bandpass Filters― [7] Menzel, Ziqiang Tong, “A Fully Integrated Scanning Receiver Array‖,2006. Fig 9: Filter after assembly.VI. CONCLUSIONS Designing of bandpass filter withButterworth approach in combination withconcentrated components, i.e. inductors and capacitorsand its computational verification in form ofparallelcoupled microstrip lines with the program givevery good filter characteristics at the centre frequency2.4 GHz with frequency bandwidth of about 100 MHzas required at the specification stage. At the centerfrequency the insertion loss and reflection factor hasthe values about -2 dB and better than -15 dB,respectively. Micro strip Filters for RF/Microwave Applicationsis not only a valuable design resource for practitioners,but also a handy reference for students and researchersin microwave engineering. Various devices andcomplex circuits can be easily designed using Stripline technology. Micro strip gives sharp response i.e. passesparticular frequency bands and suppress otherfrequency. It is a low cost solution, easy to fabricate,gives accurate results once designed, rock solid androbust in designREFERENCES [1] Gangqiang Wang, Senior Member, IEEE, Minh Van, Fred Barlow, Member, IEEE, and Aicha Elshabini, Fellow ―An Interdigital Bandpass Filter Embedded in LTCC for 5- GHz Wireless LAN Applications” ,May 2005 [2] ,E.Hanna, P.Jarry, Senior Member, IEEE, E.Kerherve, Member, IEEE., “Cross-Coupled Suspended Stripline Trisection Bandpass Filters with Open-Loop Resonators”, 2005. [3] ,Yani Mu1, Zhewang Ma2, and Deming Xu1 1―Multilayered Stripline Interdigital-Hairpin 2345 | P a g e