UNILATERALLY INJECTION-LOCKED GUNN OSCILLATOR PAIR ACTING AS A MICROWAVE ACTIVE NOTCH FILTER

Transcription

1 Internatonal Journal of Electroncs and Communcaton Engneerng & Technology (IJECET) Volume 7, Issue, March-Aprl 016, pp. 5-, Artcle ID: IJECET_07_0_004 Aalable onlne at Journal Impact Factor (016): (Calculated by GISI) ISSN rnt: and ISSN Onlne: IAEME ublcaton UNILATERALLY INJECTION-LOCKED GUNN OSCILLATOR AIR ACTING AS A MICROWAVE ACTIVE NOTCH FILTER Santosh Kumar Dawn Dept. of hyscs, Va-Bharat, Santnketan, West-Bengal, Inda Taraprasad Chattopadhyay Dept. of hyscs, Vsa-Bharat, Santnketan, West-Bengal, Inda ABSTRACT In ths paper, we present the theory and desgn of a noel mcrowae acte notch flter operatng at X-band (8 GHz-1.4 GHz). The notch flter has a notch frequency of 10. GHz and a db calculated bandwdth of 87 MHz, the correspondng db expermental bandwdth s 10 MHz. The flter s desgned usng a magc tee and two tunable X-band Gunn oscllators njecton-locked to the nput nterference to be elmnated. The specal features of ths flter are that t s of low nose, tunable and sgnal trackng character and possesses consderable power handlng capacty. Key words: Gunn Oscllator, Injecton lockng, Mcrowae, Notch flter, Notch Frequency. Cte ths Artcle: Santosh Kumar Dawn and Taraprasad Chattopadhyay. Unlaterally Injecton-Locked Gunn Oscllator ar Actng As A Mcrowae Acte Notch Flter, Internatonal Journal of Electroncs and Communcaton Engneerng & Technology, 7(), 016, pp INTRODUCTION Notch flters are essental components of a mcrowae communcaton system. Mcrowaes, accordng to IEEE conenton, span oer the frequency range GHz-0 GHz of the electromagnetc spectrum. Notch flters are used to elmnate monotone or narrowband nterference n a receer. Ths nterference can appear automatcally from adjacent channels and t can also be man-made when the nterference s ntroduced delberately for jammng a communcaton receer. A good notch flter must hae low nserton loss, neglgble radaton loss and hgh power handlng capacty whch are of major concern at mcrowae frequences. A notch flter can be treated as a specal case of band reject flter where the stop band becomes ery narrow 5 edtor@aeme.com

2 Santosh Kumar Dawn and Taraprasad Chattopadhyay and the attenuaton becomes hgh. Desgn of mcrowae notch flters [1-6] s beng nestgated oer a few decades. To make the notch flters reconfgurable and to operate at hgher mcrowae frequences, research work s gong on the desgn of notch flter all oer the globe tll now. Jackowsk et al., hae proposed a frequency agle, constant bandwdth, reconfgurable notch flter wth a tunng range of an octae [7, 8]. A notch flter has been desgned at 1. GHz wth a bandwdth of 50 MHz and 5 db rejecton at the notch frequency by Narayana et al.,. Notch flters hae been desgned [10] usng Barum strontum Ttanate thn flm aractor technology by Ramadugu. The low frequency notch flter dscussed aboe are all passe, n general. Acte notch flters [4-6] ncorporate one or more amplfyng deces such as negate resstance oscllators. These negate resstance oscllators when operated n the njecton-locked mode possess ampltude nose reducton property as well as hgher power handlng capacty. In ths paper, we hae used a par of unlaterally njecton locked Gunn oscllator operatng at X-band. The Gunn oscllators are locked to the nput nterference receed at the receer and follows the nterferng sgnal. The Gunn oscllator par s thus made coherent and ther outputs are subtracted at the E-arm of the magc tee resultng n a cancellaton of the nterference accompanyng the nput sgnal assumng the Gunn oscllator par to be dentcal. The desred sgnal falls outsde the rejecton band of the notch flter and passes through t.. MECHANISM OF OERATION The schematc crcut dagram of the notch flter s shown n n Fg. 1. It ncorporates a magc tee and two coherent Gunn Oscllators connected wth the collnear arms of the magc tee. The nput of the notch flter s the H-arm and the output port s the E- arm of the magc tee. The schottky dode detector s not any part of the notch flter. It only detects the mcrowae power and delers an output oltage proportonal to the nput mcrowae power. It ges a method of ndrect measurement of output mcrowae power. The detector output oltage s measured n an osclloscope (CRO). Fgure.1. Schematc crcut dagram of an acte mcrowae notch flter. 6 edtor@aeme.com

3 Unlaterally Injecton-Locked Gunn Oscllator ar Actng as a Mcrowae Acte Notch Flter. ANALYSIS For njecton lockng at mcrowae frequences, there must exst a free runnng mcrowae oscllator, called the slae oscllator, whch s njected by the output power of another mcrowae oscllator, called as the master oscllator. Dependng upon the frequency detunng of the njecton sgnal frequency from the free runnng slae oscllator frequency and the relate power of the njecton sgnal, the slae oscllator gets njecton locked to the master oscllator. Under locked condton, the slae oscllator frequency becomes dentcal wth that of the master oscllator and the nputoutput phase error assumes a constant alue. If the njecton sgnal power s much less than the free runnng slae oscllator power, the latter s sad to be under dren. On the other hand, the locked oscllator s sad to be oerdren f the njecton sgnal power s comparable or greater than the free runnng slae oscllator output power. The njecton locked Gunn oscllators (GO# and GO#) hae ampltude lmtng property. Any ampltude modulaton of the njecton sgnal s shaked-off by the locked oscllators. So, we wll not use ampltude modulaton as modulaton format of the nput sgnal. Rather, we wll consder FM sgnal nput and study the response of the sub-system to such frequency modulated sgnal. The nterference to be remoed from the receer s assumed to be monotone n nature. We wll make a statc analyss of the sub-system consderng a slow araton of nput master sgnal frequency. The nput sgnal s delered by a tunable Gunn oscllator (not shown n Fg. 1). Let the mcrowae oltage of the nput sgnal be wrtten as 1 V1 sn 1t (1) where V 1 s the oltage ampltude and 1 s the radan frequency. The njecton sgnal oltage to Gunn oscllators (GO# and GO#) s obtaned through half-power ( ) dson of the nput sgnal at the magc tee juncton and s gen by 1 t. The Gunn oscllator GO# and GO# are taken of the same type whch oscllate at the same mcrowae frequency. The oltages of the free-runnng GO# and GO# are descrbed by the equatons and f 0 V sn t () f 0 V sn t () respectely. Here, 0 0 where 0 and 0 are the radan frequences of the Gunn oscllators GO# and GO# respectely. The free runnng output powers are f and f where f V f and f V f respectely. The output oltages of the njecton-locked Gunn oscllators are assumed to be of the form ( 1 t) V sn ( t ) (4) for =,. V s the oltage ampltude and s the nput-output phase error of the - th slae Gunn Oscllator. Neglectng any asymmetry n lockng, the phase equaton of the njected Gunn oscllator (GO# and GO#) are gen [11] by 7 edtor@aeme.com

4 Santosh Kumar Dawn and Taraprasad Chattopadhyay d nj sn dt 0 (5) 1 QL o for =,. (t) s the nput-output phase error for the - th Gunn oscllator, Q L s the loaded Q-factor and o s the output power of the - th njecton locked Gunn d ( ) oscllator. Under steady state condton of lockng, t 0. Then, dt sn o 1 0 QL (6) nj 0 assumng and o V s the output power of the -th locked oscllator. The ampltude goernng equatons [11] of the njected Gunn oscllators are wrtten as da dt where =, and R1 0 0 nj a 1 a cos (7) Q Q V a V f L L. The parameter 0 L Rd R RL R1. Here R d s the R magntude of the negate resstance of the Gunn dode, R s the caty resstance and da R L s the load resstance. In the steady state of lockng, 0. The frequency dt response of the njected Gunn oscllator s obtaned by elmnatng from (5) and da (6) wth 0 dt as nj 0 QL a R a (8) 0 for =,. For a gen alue of, equaton (8) s numercally soled to get the frequency response of the njecton-locked Gunn oscllator. The araton of a and a wth frequency detunng 1 0 s shown n Fg. and Fg. respectely. 8 edtor@aeme.com

5 Unlaterally Injecton-Locked Gunn Oscllator ar Actng as a Mcrowae Acte Notch Flter Fgure.. lot of a wth Frequency detunng 1 0 Fgure.. lot of a wth frequency detunng 1 0 Usng the scatterng matrx of the magc tee [11], the total nput oltage of the Schottky dode detector connected wth arm-4 (E-arm) of the magc tee s expressed as Dn sn 1t (9), The detector characterstcs as obtaned from earler work [11] s expressed as Dout n Dn (t) where Dout s the detector output oltage, Dn (t) s the effecte mcrowae nput oltage of the dode detector, n s the nput mcrowae power of the dode detector and s the responsely of the detector. From equaton (9), we can wrte 1 cos 1 Dn (11) 4 (10) 9 edtor@aeme.com

6 Santosh Kumar Dawn and Taraprasad Chattopadhyay Under locked condton, both GO# and GO# hae the same oscllaton frequency, 1. The njecton power s same for both the Gunn oscllators GO# andgo#. When, Dun 1 V (1) max 4 V Ths ges the maxmum output oltage of the detector. The detector s not a part of notch flter. It s only used to measure the output power of the notch flter n terms of oltage. The normalzed output power of the notch flter usng equaton (10) s gen by f = Dout Dout a max. f f a V V V V cos V V a a a f f a a a f f cos The calculated frequency response of the proposed notch flter s obtaned from equaton (1) and s plotted n Fgure. 4. The normalzng factor s 15 m. The Theory and experment show a good ft. f (1) Fgure. 4. Theoretcal and Expermental frequency response of the proposed notch flter. 0 edtor@aeme.com

7 Unlaterally Injecton-Locked Gunn Oscllator ar Actng as a Mcrowae Acte Notch Flter 4. EXERIMENT The Gunn oscllators hang model no. XG-11 hae been procured from M/S SICO Ltd; Inda. Magc tee and drectonal couples used for mcrowae power measurement and arable attenuator for nput sgnal power attenuaton hae been purchased from M/S Vdyut Yantra Udyog Lmted, Inda. Schottky barrer dode and the mcrowae power meter hae been procured from M/S Salcon Nanotechnology Lmted, Inda. The measured lock band for Gunn oscllator GO# wth free runnng frequency of 10. GHz and free runnng power of 8.75 mw s 118 MHz for an njecton power of 4.5 mw. Ths corresponds to a loaded Q factor. Q L =60. GO# has a free runnng power of 7.5 mw at the free runnng frequency of 10. GHz. It has a Q-alue of 59. The notch Frequency can be tuned by tunng the free runnng frequences of slae oscllators GO# and GO#. 5. CONCLUSION The theory and desgn of an acte mcrowae notch flter has been presented n ths paper. The notch frequency s 10. GHz wth a -db expermental bandwdth of 10 MHz. Ths flter has neglgble nserton loss and consderable power handlng capacty. Besdes, snce njecton lockng has been used n the desgn, the notch flter wll strongly reduce ampltude nose [11] of the receed sgnal. The notch flter has also nput sgnal trackng property. 6. REFERENCES [1] I.C. Hunter and J.D. Rhodes, Electroncally tunable mcrowae band stop flters, IEEE Transactons on Mcrowae theory and Technques, ol. MTT-0, pp , Sept [] R. Ley, R.V. Snyder and G. Mathal, Desgn of mcrowae flters, IEEE Transactons on Mcrowae theory and Technques, ol. MTT-50, no. pp , Mar 00. [] T-Ln. Wu, Mcrowae flter desgn, Chap.6, Department of Electrcal Engneerng, Natonal Tawan Unersty, John Wley & Sons, Inc., 001. [4] R.V Snyder, Ealuaton of of passe and acte mcrowae flters, Mcrowae Symposum Dgest, pp. 1-, 01. [5] B.Y. Kaplech, Varety of approaches to desgnng mcrowae acte flters, 7 th European Mcrowae Conference, Jerusalem, Israel, ol. 1,pp , 8-1 Sept [6] C.Y. Chang and T. Itoh, Mcrowaes acte flters based on coupled negate resstance method, IEEE Trans. On Mcrowae Theory and Technques, ol. MTT-8, no. 1, pp , Dec [7] D.R. Jackwosk and A.C. Guyette, Sub-octae-tunable mcrostrp notch flter, IEEE EMC Socety Symposum on Electromagnetc Compatblty, pp , Astn, Texas, VSA, Aug. 17-1, 009. [8] D.R. Jackwosk, asse enhancement of resonator Q n mcrowae notch flters, 004 IEEE MTT-s Internatonal Mcrowae Symposum Dgest, pp , June 004. [9] M.S. Narayana and N. Goga, Accurate Desgn of a notch flter usng electromagnetc smulators, Appled Mcrowae and Wreless, pp , ol. 1,art 11, edtor@aeme.com

8 Santosh Kumar Dawn and Taraprasad Chattopadhyay [10] J.C. Ramadugu, Desgn of mcrowae bandstop and bandpass flters on Barum Strontum Ttanate thn flm aractor technology, h. D. Thess, Unersty of Dayton, Dayton, Oho, USA, Dec. 01. [11] Arnd Kumar, A Bhattacharya and D K Sngh. Mcrowae Image Reconstructon of Two Dmenson Delectrc Scatterers Usng Swarm artcle Optmzaton, Internatonal Journal of Electroncs and Communcaton Engneerng & Technology, 4(6), 01, pp [1] rof. B.N. Bswas, S. Chatterjee and S al. Laser Induced Mcrowae Oscllator, Internatonal Journal of Electroncs and Communcaton Engneerng & Technology, (1), 01, pp [1]. Bhattacharyya, S. K. Dawn and T. Chattopadhyay, Low nose bandpass flter usng an X-band njecton locked Gunn oscllators, Internatonal Journal of Research n Engneerng and Technology, ol. 04, ssue-1, pp. 1-6, Dec edtor@aeme.com