Design and Fabrication of Miniaturized Diplexer for Antenna Applications

Transcription

1 14 IJEDR Volume, Issue ISSN: Desin and Fabrication of Miniaturized Diplexer for Antenna Applications A.Anand PG Scholar, Department of ECE SSN Collee of Enineerin, Kalavakkam 63 11, Tamil Nadu, India Abstract - there is a rowin need of microwave systems to meet the emerin communication challenes with respect to reduction in size, cost and performances. This paper presents the desin of miniaturized diplexer for antenna applications. The diplexer is a combination of two filters, Lowpass filter (LPF) (7-96MHz) and Bandpass filter (BPF) (1.5-.5GHz). It is used for combinin and splittin RF fees, so they can be used by multiple receivers and possibly on different frequencies. The ADS Simulation tool is used to desin the filters. The simulation results shows that the filter works on 9MHz (LPF) and GHz (BPF) at the center frequency. Compared to other filter desin types, this desin works very well in recent challenes. Index Terms - Diplexer,Lowpass filter, Bandpassfilter, microstrip, dielectric constant,fractional bandwidth, diplexer, substrate, insertion loss, return loss. I.INTRODUCTION A Diplexer is a three port network that splits the incomin sinal on one end and directs it throuh two outputs to different lines, dependent on frequency. A diplexer is the simplest form of a multiplexer, which can split the sinals from one common port into many different paths. There are no of ways to desin a diplexer which involves use of filters. In this way, the route for the different transmitters and receivers can be divided, accordin to the frequency they use.[1] The simplest way to implement a diplexer is to use a lowpass and hihpass filter. In this work, bandpass filter is used instead of hihpass filter. In this way, the diplexer routes all sinals at frequencies below the cut-off frequency of the lowpass filter to one port, and sinals containin band of frequencies not adjacent to zero frequency, such sinals that comes out of a bandpass filter to another port. There is no path connection between the filters. All the sinals that can pass throuh the lowpass filter will not be able to pass throuh bandpass filter and inversely. When desinin a diplexer, number of parameters must be studied. One is the deree of isolation required between two ports for low and hih frequency transmitter/receiver. If the diplexer is to be used entirely for transmittin, then the requirements of hih level of isolation is not so hih. Comparatively each filter ive enouh isolation to protect each receiver with perfect impedance and the sinalsare routed for correct input without any perceptible losses.[1] Fi.1 Block diaram for diplexer Return loss and insertion loss are considered to be the performance measurement parameters for low frequency filter desin. Our proposed work focuses on the desin of miniaturized diplexer for antenna applications. Diplexer is widely used in communication systems to transmit radio sinals throuh an antenna that could otherwise only handle a limited number of sinals.it consists of array of coupled resonator structures. Each resonator has a direct round connection at one end and rounded with capacitor at other end. Antenna diplexer is used in many broadcast applications allowin a sinle RF antenna to be used for more number of transmitters.[] The filter desin frequency is chosen by radio frequency of audio and video sinals for both the filtersand the simulation is done for different frequency usin ADS simulation tool. The filter performance parameters are simulated in terms of insertion loss and return loss. Simulation results are represented in terms of S-parameters such as transmission coefficient (S 1 ) and reflection coefficient (S 11 ). IJEDR1487 International Journal of Enineerin Development and Research ( 186

2 14 IJEDR Volume, Issue ISSN: II. DESIGN METHODOLOGY Conventional microstrip lowpass and bandpass filters such as stepped-impedance filter are widely used in many RF/microwave applications. In this proposed work,stepped-impedance filter type is used. In eneral desin of microstrip lowpass filter involves two main steps. The first step in the desin of microwave filter is to select a suitable approximation of the prototype model based on the specifications. Second is to calculate the order of the filter from the necessary roll off as per the iven specifications.[3] In eneral, the structure of stepped-impedance lowpass filter,uses a cascaded structure of alternatin hih and low transmission lines. The hih impedance lines act as series inductors and the low impedance lines act as shunt capacitors. Lowpass filter Based on the desin specifications iven in Table I, prototype values are calculated for lowpass filter. Some theoretical desin information must contribute to the microstrip lines, because the expression for inductance and capacitance depend upon both the characteristics impedance and lenth. By initially fixin the characteristic impedances based on hih and low impedances lines by studyin, c<<l, where C and L indicates the characteristic impedances of low and hih-impedance lines, appropriately and is the source impedance, which is commonly 5Ω for microstrip filters. Result of lower C is the leadin approximation of lumped-element capacitor. Result of hiher L is the leadin approximation of lumped- element inductor. Desin Equations Low pass prototype element values are iven in Table II. A lowpass prototypewith a Chebyshev response is chosen. Usin, 1.. 3, lumped element values for lowpass filter have been calculated. Whose elements values for the normalized cut-off ΩC=1.. Usin the element transformation it is explained, we have Filter type Table 1 Desin Specifications Chebyshev Order of filter (n) 5 Center frequency (f ) Substrate Thickness H 9MHz 1.54mm Dielectric constants ( r ).55 Conductor Thickness T.3mm Filter Order (n) Table Low Pass Prototype Element Values Usin these prototype the lowpass filter desin can be desined. This filter can be act as miniaturized lowpass filter i.e., desinin a filter itself they can be miniaturize by means of low frequency(9mhz) values for the filter. The filter performance can be act as more than -1dB rane for S1 and less than -.5dB for S11 rane. Fi. Circuit diaram for Lowpass filter Fi. shows the desired filter structure usin discrete components and fi.4 layout shows the structure of stepped-impedance filter. Our next step is to determine the physical structure of these section so that it can be definitely act as resistors, inductors and capacitors. For this type Butterworth desin, the equation is iven by(1)and () used in[4], L R n ln ( ind) (1) hih IJEDR1487 International Journal of Enineerin Development and Research ( 187

3 14 IJEDR Volume, Issue ISSN: Cn ln ( cap) R low () We now computethe values of the effective dielectric constant of the substrate materials usin above equations. Thus next we compute the values and β. (5) r1 r1 reff 11x The values of β from the above equations, which ives l l n n ( ind) (6) n ln ( cap) (7) By usin these equations we find correspondin L and C values. (3) (4) Table 3Calculated Values For L And C Prototype element values Correspondin L and C values 1=5=3.48 =4=.76 3=4.538 By substitutin all these L and C values in the network desin, we have, reff L1=L5=.6964 C=C4=.54 L3=.937 Fi.3 Schematic circuit diaram for lowpass filter usin lumped components From above these equations and lowpass prototype elements to found out schematic circuit diaram for eneral circuit. By usin this correspondin width and lenth values the eneral layout can be desined. Fi.4 Layout structure of stepped-impedance lowpass filter For the above schematic, the layout can be iven as follows, IJEDR1487 International Journal of Enineerin Development and Research ( 188

4 14 IJEDR Volume, Issue ISSN: Fi.5 Layout structure usin ADS tool The filter desin is then optimized with respect to its lenth to obtain the desired cut-off characteristics. Thus the filterperformance is minimized compare with lenth andwidthofthe layout. Thus the filter performance is some ideal stae and we et sharpest attenuation of -5dB. Usin this stepped-impedance type and cut-off frequency of 9MHz applications to personal mobility and mobile terminoloies. Hence the filter allows to pass the frequencies less than 9MHz and rejects those frequencies more that that. Fi.6 Performance of the lowpass filter Bandpass filter Bandpass filter is a passive component, which is able to allow a certain rane of frequency and rejects the frequency in another reion. It can reduce the transmitters, harmonic and spurious emission and it improve the rejection of interference for receivers. Microstrip line is a well platform for desinin a filter, due to its advantaes of liht weiht, low cost, compact size and it is ease of interation with other components on a sinle PC board. In this work, we have desined a bandpass filter for antenna applications usin microstrip line for GHz. Our main aim is to achieve hih accuracy in obtainin the required desined parameters(like Insertion loss, return loss and center frequency). The desined and simulation are performed usin ADS simulation and response of the filter is also verify by usin Network Analyzer. used in[1],[5],[8] Table4Desin Specifications Filter Type Chebyshev Order of filter(n) 3 Upper Cutoff frequency(f1) 1.5GHz Lower cutoff frequency(f).5ghz Ripple in passband.5 Dielectric constant( r).55 Filter order (n) Table 5Prototype Values For Bandpass Filter The lumped values of the bandpass filter after frequency and impedance scalin are iven by, used in[7] L1 L 1 (8) L (9) IJEDR1487 International Journal of Enineerin Development and Research ( 189

5 14 IJEDR Volume, Issue ISSN: L3 The followin schematic circuit diaram for bandpass filter, L 3 (1) C C C 1 3 L1 (11) C (1) L (13) 3 Fi.6 Schematic circuit diaram for Bandpass filter From this above schematic circuit diaram the bandpass filter has been desined and plotted for GHz rane. Fi.7 Schematic output for Bandpass filter Desin steps The filter desin steps are reported as: 1. We have started the desin methods for bandpass filter with a three-pole (n=3) ladder type lowpass prototype (i.e., Chebyshev response ) which is taken by the normalized value i.e., 1,, 3.. The normalized values of the lowpass prototype filter transformed into L-C element for the source frequency 5Ω and mid band frequency f. 3. The next main step is the desin of microstripbandpass filter to find a appropriate filter realization.the filter is fabricated on a FR-4 substrate. 4. We use the followin equations for desinin a bandpass filter iven by, the followin equations used to calculate width and lenth as used in[5][8], j 1 j n 1 N 1 N (14) (15) IJEDR1487 International Journal of Enineerin Development and Research ( 183

6 14 IJEDR Volume, Issue ISSN: j N 1 N N 1 (16) Where =(ω-ω1)/ω = characteristic impedance=5ω 5. Then the values of odd and even mode impedances can be calculated as follows, e 1 j j (17) o 1 j j (18) e o Calculate the even and odd mode impedance values & of the bandpass filter usin the desin procedure iven above. Synthesize the physical parameters (Lenth & Width) for the microstrip lines for a substrate thickness of 1.54mm and a dielectric constant of Now usin the sinle line equations to find out the (w/h)so and (w/h)se from oso and ose, For, w h Where, w 8exp( A) A h e (19) A B r r1 / r1 r1.11 (.3 ) r () (1) (w/h)so and (w/h)se by applyin oso and ose as applyin for makin a sinle line microstrip equations. 7. Now it the point to specify the family of appropriate equations where it reach the w/h and s/h for the desired microstrip equations as followin, w h s h cosh 1 s ( cosh 1 cosh s h cosh whse sh h cosh cosh se cosh so h h cosh so cosh se h h (3) () 8. Effective dielectric constant is iven by, reff reff r1 r1 11x (4) (5) (6) IJEDR1487 International Journal of Enineerin Development and Research ( 1831

7 14 IJEDR Volume, Issue ISSN: Thus the lenth of the required microstrip is, L (7) 4 Table 6 Calculated Values Of Even And Odd Resistance Stae o(ohm) e(ohm) Table 7 Calculated Dimensions Of Transmission Line Section Stae W(mm) S(mm) L(mm) A simulation was performed to verify the above dimensions in millimeter rane. For this simulation purpose we used ADS simulation tool for verify and testin. Fi.8 Schematic circuit diaram for bandpass filter usin Microstrip lines By usin microstrip schematic circuit diaram need to chane the structure usin desired even and odd mode impedances. Fi.9 Layout filter structure for Bandpass filter Finally, the performances of the filter is moderately miniaturize for GHz rane its center frequency is 1.5GHz for this rane we et S11 as more than -3dB and S1 as less than -.5dB rane. IJEDR1487 International Journal of Enineerin Development and Research ( 183

8 14 IJEDR Volume, Issue ISSN: Fi.1 Performance of Bandpass filter III.DESIGN AND SIMULATION RESULTS ADS simulation tool is used to simulate the schematic and layout of micro strip filters for low frequency values used for antenna applications. The simulated results show that the return loss and insertion loss with hiher dielectric constant ives better performance. Our next step is to desin a diplexer by usin these two microstrip filters. By interatin these filters we make a miniaturized diplexer. The performance of interation testin is to verify functional, performances and reliability requirements placed on major desin items. Table 8 Diplexer Parameter No S-Parameter Frequency(dB) 1 S11 -.8,-.5 S S Normally, a diplexer is a three port network. Here in this diplexer desin we are created a three port network layout for different frequencies. Our main aim to desin a miniaturized diplexer for mobile terminoloy and personal mobility. By interatin the filter itself it can perform like an antenna. Fi.11 Layout structure of Diplexer Finally, the miniaturized diplexer can be desined and modulated usin ADS simulation tool. For diplexer the input and output port was relatively same i.e.,5ω. IV. CONCLUSION AND FUTURE WORK The proposed work involves desinin of miniaturized diplexer with hih level of isolation. The miniaturized diplexer is desined by the interation of LPF(9MHz) and BPF(GHz), where LPF and BPF separately acts as an miniaturized filter in many other applications. Thus the desined miniaturized diplexer acts as an antenna in the applications where it is used. The proposed circuit and layout was carefully implemented and the measured and simulated results are in favourable areement. The fabrication for the diplexer can also be done usin FR-4 substrate with a thickness of 1.54mm, relative dielectric constant of.55 and.3mm loss of tanent. The fabrication of diplexer accounts to future modification. REFERENCES [1] [] Pu-Hua Den, Jen-Tse Tsai, Desin of microwave Lowpass- Bandpass Diplexer, IEEE microwave and wireless components letters, vol. 3, no.7, July 13. IJEDR1487 International Journal of Enineerin Development and Research ( 1833

9 14 IJEDR Volume, Issue ISSN: [3] K.Rajasekaran, J,Jayalakshmi, T. Jayasankar, Desin and analysis of stepped impedance microstrip lowpass filter usin ADS simulation tool for wireless applications International Journal of scientific and research publications, volume 3, Issue 8, Auust 13. [4] Jia-shen Hon and M. J. Lancaster, Microstrip filters for RF/Microwave Applications, John Wiley & sons, 1. [5] SayantikaBhattacharjee, Debabratapoddar, sandeepmukherjee, Desin of microstrip parallel coupled bandpass filter for lobal positionin system, Journal of enineerin, computers & Applied science Volume, No.5, May 13. [6] D.Budimir and L.Athukorala, Miniaturized filters and Diplexers for wireless Broadband communication systems, Wireless communication research roup /8/$ Dec 8. [7] David M Pozar, Microwave and RF desin of wireless systems, John Wiley & sons, 1. [8] Matthaei, Geore. L., Comblinebandpass filters of narrow or moderate bandwidth, The Microwave Journal, [9] Annapurna Das and Sisir K Das, Microwave Enineerin, Tata McGraw Hill Education Private Limited, second edition,9. IJEDR1487 International Journal of Enineerin Development and Research ( 1834