A Compact 3D-microwave holographic pointer system using a size reduced microstrip planar array

Transcription

1 A Compact D-mcrowave holographc ponter system usng a sze reduced mcrostrp planar array Hala Elsadek, Hesham Eldeeb, Franco De-Flavs, Lus Jofre, Esmat Abdallah* and Essam Hashsh** Department of Electrcal and Computer Engneerng, Unversty of Calforna, Irvne, Irvne, CA-, helsadek@uc.edu. *Mcrostrp Department, Electroncs Research Insttute, Dokk, Gza, Egypt,. **Electroncs and Communcaton Department, Faculty of Engneerng, Caro Unversty, Egypt. Abstract A compact system for a three dmensonal (D) ponter (mouse) s possble by combnng mcrowave holography wth mcrostrp antenna arrays to enter D coordnates of a pont n space nto computer memory. To reach the practcal reduced sze system, new solutons are proposed n both, the recevng planar array antenna for constructng the pont hologram mage and the holographc algorthms for reconstructng the mcrowave hologram. Key words Mcrowave holography, D ponter (mouse), planar mcrostrp array antenna, antenna sze reducton, slt nserton. Introducton More than forty years have passed snce the frst mcrowave hologram was done at Bell laboratores n. Mcrowave hologram proves that t has several advantages over the optcal one that was nvented by Gabor 8[]. We utlze ths dea to desgn an nteractve system for a D ponter. Usng ths new ponter, the operator can create and draw, pont by pont or n a multpont bass, any D object that exsts physcally or even vrtually and save t n computer memory. Afterwards ths can be used n nformaton reducton, scalng, nterpolaton, mage compresson, and D data acquston, generatng a body ftted grd system for computer smulaton, data anmaton or pattern recognton of objects n D space. We can magne applyng ths D mage processng n many felds of applcatons such as computer-aded desgn n medcne and robotcs where true spatal nformaton renders mportant assstance. For practcal purposes an nvestgaton volume of m x m x m s defned, and the dfferent electrcal and geometrcal system parameters are consdered. As a workng frequency, we propose -band or C-band operaton as a good compromse between postonng accuracy and antenna array number of elements. Usng a conventonal planar magng system wth FFT technque, a holographc plate surface of about m x m had to be consdered, makng the system sze unsutable practcally for many applcatons []. Instead, usng the reduced system proposed here, a planar antenna of.m x.m could be used whle keepng the system locaton capabltes of about ( λ /.) n accuracy unchanged. To check the dfferent parameters of the system, a prototype of mcrostrp planar array wth a lmted number of elements (x) has been fabrcated and measured. The prototype has been tested at dfferent frequences wth a reduced holographc plate sze of (cmxcm) and ts postonng capabltes have been nvestgated n the reconstructon volume of cm x cm. In ths paper, we llustrate the results at -band (.GHz). The reconstructon here s done by correlaton technque, whch s free from λ / hologram s grd sze crteron that exsts n conventonal FFT technque []. Excellent results are reached. Needless to say that the extenson of our system represented here has no lmtatons nether n array surface nor n reconstructon volume. New correlaton algorthm for hologram reconstructon The dgtal hologram data s retreved by a new computer smulaton model [] called correlaton technque, whch s based on the followng equaton: Proceedngs of the IEEE ystems, Man, and Cybernetcs Conference Copyrght@

2 φ = cos( kr = φ I () R Where φ s the retreved mage, I s the ntensty of a grd pont on hologram plane and R s the dstance between hologram plane s grd pont ( ) and reconstructon pont (). The procedure n equaton () merely nspects whether the pont () s a part of the orgnal object or not. Ths s accomplshed by usng the correlaton between the hologram ntensty and the factor: ( P = cos( kr ) / R ) whch represents the hologram of pont source. If the hologram I concdes wth the pattern P generated by the pont source at (), the correlaton φ becomes large and hence the pont () has a large probablty to be ncluded n the orgnal object. On the contrary, f I doesn t concde wth P then φ becomes very small and hence the pont () s not ncluded n the orgnal object. Wth changng () over the D space and drawng the structure of φ, t should concde wth the orgnal object pattern. Ths method doesn t suffer from the FFT lmtatons so the hologram samplng grd separaton can be less than λ / and the number of ponts n doesn t need to be n the form of. D ponter system The proposed D ponter system s llustrated n Fg. []. The ponter unt tself works as hand agent that contans a passve reflectng dpole antenna wth a modulatng dode at low frequency n range of KHz. Ths unt s attached to the operator s hand to locate ts movements. The llumnator (transmtter dpole antenna) s fxed n a certan corner wthn the reconstructon volume. When the user clcks on the hand agent at the requred poston n space, the swtch s closed allowng modulatng the llumnaton sgnal at the dode marked pont at low ) frequency level. Modulatng the dode results n modulatng the scattered feld whch s proportonal to the local feld at the correspondng ponter locaton The ponter s plate contans the recever (mcrostrp antenna array) that measures the modulated object scattered sgnal (whch carres the ampltude and phase nformaton of the pont poston). The object sgnal nterferes wth the reference sgnal n the panel unt to form the nterference pattern (hologram). The hologram data s de-modulated and dgtzed n the same unt. Dgtal data s nterfaced to computer and retreved n t through a hologram reconstructon drver (t can be software or hardware []) that s called a D ponter card. Fnally the retreved pont s drawn on the screen, f needed, wth any graphcs software. Note that the dode modulaton step can be replaced by drectly connectng the transmttng dpole antenna to the operator s hand mouse unt, whch wll be connected to the generator through RF cable wth the cost of movable RF connecton. In ths case, the mcrostrp antenna receves drectly the mouse radated sgnal. The selecton between the two models depends on the applcaton. Needless to say that our ponter system can work n a sngle pont bass as dscussed or n a mult pont bass where each pont has a modulatng dode wth dfferent frequency level. Ths can be utlzed n detectng an object movement or n defnng dfferent selected propertes snce each modulatng dode can refer to certan property lke color, materal type, etc. It s worth here to menton that f we add two llumnatng dpoles, one wth lnear vertcal polarzaton and the other wth lnear horzontal polarzaton n the requred reconstructon volume, we can detect from the recevng sgnal not only the pont poston but also ts orentaton n space. Ths could be done f dfferent polarzaton drectons are used for the adjacent elements of the mcrostrp array antenna. The D ponter (mouse) system s llustrated n Fg. Proceedngs of the IEEE ystems, Man, and Cybernetcs Conference Copyrght@

3 Fg.:D ponter prototype system ze Reduced Planar Mcrostrp antenna wth slt nserton procedure We reduce the ndvdual antenna element surface by cuttng a slt at an adequate poston of the patch surface wth adequate length and wdth. We select an nverted H shape slt because t can effectvely mnmze the sze of the mcrostrp antenna from, a half wavelength to a quarter wavelength, wthout any overlap wth the feed aperture or feed lne []. The slt decreases the resonant frequency because the current has to flow around the slt so the electrcal equvalent length of the current path gets longer. The drawback of addng slts s the decrease n the mpedance bandwdth whch becomes less than %. Ths s not sutable for practcal applcatons. tackng technque wth short crcut pns (vas) s used to mprove the bandwdth up to %, whch s accepted from most array applcatons pont of vew as n our case of hologram recordng. Fg. shows the antenna element s layout and the return loss response for the orgnal rectangular patch, patch wth slts and wth addng stackng layer and vas to mprove the bandwdth. n db orgnal patch patch wth slt patch wth slts and pns Frequency n GHz Proceedngs of the IEEE ystems, Man, and Cybernetcs Conference Copyrght@ (b) Fg.. a) Antenna layout for orgnal rectangular patch wth aperture coupled feed, wth H shape slt

4 and wth slt and shortng pns b) return loss value for sngle patch n the three cases of (a). The antenna physcal surface sze s reduced by rato of % from the orgnal rectangular patch as shown n fgure (a). The man problem of addng the slts wth ts nductance effect s the dffculty to match wth feed. To solve ths problem, short tunng stub of approprate length and wdth s connected to patch as llustrated n fg. (a)[]. The stub poston s on the patch edge wth offset from patch center of half feed lne wdth Ths perturbed cavty or short tunng stub s used n conjuncton wth the proxmty couplng to oppose the slt effect and provde enhanced element matchng. Ths element s ncluded n a x array. The array s fabrcated and measured. Fg. llustrates the comparson between the smulaton and expermental results wth nter-element dstance (center to center) λ /. dfferent ponts wthn the operator s hand reconstructon volume. Fg. shows two of these results. We use here software flter to clarfy the pont poston. As dscussed before, the holographc system n fgure can be used for smultaneously dentfyng multple ponts, colors or materals usng dfferent modulatng frequency for every selected feature. Fgure s a smulaton example for two ponts reconstructon wth hologram sze of mxm and ponts postons at (cm, cm, cm) and (cm, cm, cm) respectvely. The resoluton (mnmum object pont separaton) s found emprcally to be about λ whle the accuracy s related to the number of the array antenna elements _ n db ssm ssm ssm ssm sexp sexp sexp sexp 8 8 y cm Freqency n GHz (a) sm exp sm exp sm exp - j n db y cm Frequency n GHz Fg. Comparson between smulaton and Expermental results of x reduced sze antenna array at (.GHz) - band. Vrtual mage reconstructon results (x) and grd samplng λ / wth the pont poston at a) (,,) and b) (,,), cm). To valdate the D ponter system capabltes, the hologram s generated at Proceedngs of the IEEE ystems, Man, and Cybernetcs Conference Copyrght@ (b) Fg. Retreved mage of one pont holography at frequency of.ghz wth hologram sze of 8

5 smplfed ray-tracng approach, Computer n physcs, vol., No.,, pp:8-. [] Hala Elsadek, Hesham Eldeeb, Masazaku Ueda, Jun Horkush and Takash Yabe, Usng mcrowave holography and mcrostrp antenna for D mouse nvestgaton, Internatonal. Journal of electroncs, vol.8, No.,, pp: y cm []Xue Xa Zhang and Fan Yang, tudy of a slt cut n mcrostrp antenna and ts applcatons, Mcrowave and optcal technology letters, vol.8, No., 8, pp:- 8 Fg.: Reconstructed mage of two ponts hologram at.ghz wth pont s postons at (cm, cm, cm), (cm, cm, cm) and wth hologram sze mxm. Concluson A specal method for nvestgatng D mouse or D ponter was descrbed. By ths method, the hologram s easly establshed for any pont wthn the desgned reconstructon volume at low cost. Reducng the recevng antenna surface does an mprovement n the hologram plate sze. The mage s retreved by correlaton algorthm. Usng the reduced sze antenna wth the correlaton technque, the system sze can be reduced by about % of ts orgnal sze usng orgnal rectangular patch antenna wth conventonal FFT reconstructon technque. Retreved mages of a pont hologram at dfferent D postons verfy the dea. References []ng H. Lee, Computer generated holography:, an ntroducton, Appled optcs, vol., No., 8, pp:. [] Chrtan Pchot, Lus Jofre, Gullaume Peronnet and Jean Bolomey, Actve mcrowave magng of nhomogeneous bodes, IEEE transactons on antennas and propagaton, Vol. AP, No., Aprl 8, pp -. [] Alan D. ten, Zhyue Wang and John. Legh, Computer generated holograms, Proceedngs of the IEEE ystems, Man, and Cybernetcs Conference Copyrght@