Inter national J our nal of Adv ances in A pplied Sciences (IJ AAS) V ol. 15, No. 1, March 2026, pp. 372 ∼ 383 ISSN: 2252-8814, DOI: 10.11591/ijaas.v15.i1.pp372-383 ❒ 372 Miniaturized cir cular fractal patch antenna with defected gr ound structur e f or high-selecti vity dual-band X-band applications Raju Thommandru, Rengaraj Sara v anakumar Department of Electronics and Communication Engineering, Sa v eetha School of Engineering, Sa v eetha Institute of Medical and T echnical Sciences, Sa v eetha Uni v ersity , Chennai, India Article Inf o Article history: Recei v ed Sep 2, 2025 Re vised No v 17, 2025 Accepted Jan 1, 2026 K eyw ords: Circular fractal patch antenna Defected ground structure Dual-band operation Miniaturization X-band ABSTRA CT Microstrip patch antennas are easily f abricated and ha v e a lo w prole, making them widely used in radar , satellite, and defence applications. Achie ving high selecti vity and miniaturization in X-band dual-band operation remains a challenge. Con v entional designs using simple patch geometries and defected ground structures (DGS) often e xhibit limited bandwidth, poor impedance matching, and reduced g ain. T o address these limitations, this w ork presents a miniaturized circular fractal patch antenna with an optimized DGS to enhance frequenc y selecti vity , impro v e impedance matchi ng, and maintain compact size. Circular fractal s lots are introduced in the radiating patch to e xtend the ef fecti v e current path while preserving the footprint. A centrally placed diamond-shaped slot pro vides capaciti v e loading that aids impedance tuning. Electromagnetic simulations were conducted in Ansys HFSS 2023 R2, and a prototype w as f abricated on an FR-4 subs trate with ε r = 4 . 4 , loss tangent = 0 . 02 , and thickness 1 . 6 mm . Measurements v erify tw o passbands: 8 . 637 – 9 . 173 GHz (center 8 . 80 25 GHz , return loss − 22 . 0267 dB , v oltage standing w a v e ratio (VSWR) 1 . 1720 , g ain 4 . 82 dB , ef cienc y 6 3 . 51% ) and 10 . 121 – 10 . 956 GHz (center 10 . 3700 GH z , return loss − 25 . 2864 dB , VSWR 1 . 1199 , g ain 3 . 4 2 dB , ef cienc y 72 . 58% ). The antenna sho ws steady radiation and impro v ed matching across both bands, supporting use in compact X-band front ends. This is an open access article under the CC BY -SA license . Corresponding A uthor: Reng araj Sara v anakumar Department of Electronics and Communication Engineering, Sa v eetha School of Engineering Sa v eetha Institute of Medical and T echnical Sciences, Sa v eetha Uni v ersity Chennai, India Email: sara v anakumarr .sse@sa v eetha.com 1. INTR ODUCTION Microstrip patch antennas ha v e emer ged as one of the k e y components in contemporary wi reless technologies because of their lo w prole, light weight, and easy-to-inte grate features with radio frequenc y (RF) front ends. This cl ass of antennas supports use in satellite links, weather monitoring, remote sensing, radar , and defense. The X-band ( 8 GHz to 12 GHz ) is particularly important for surv eillance radars, space missions, and military communications, where compact, ef cient, and multi-functional radiators are essential. Despite these adv antages, microstrip patches f ace constraints that include narro w impedance bandwidth, moderate g ain, and reduced ef cienc y under miniaturization. Achie ving a compact dual-band response in the X-band is dif cult because size reduction, impedance matching, radiation ef cienc y , and J ournal homepage: http://ijaas.iaescor e .com Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Adv Appl Sci ISSN: 2252-8814 ❒ 373 selecti vity often pull in dif ferent directions. Bandwidth enhancement is commonly pursued through parasitic elements, multiple resonators, or defected ground structures (DGS), b ut these methods may enlar ge the footprint, introduce unw anted modes, or disturb pattern stability . Fractal geometries such as Sierpinski, K och, and Mink o wski can lengthen the current path for multiband beha vior and smaller size. Ho we v er , man y fractal designs tar get lo wer frequenc y services (for e xample, GSM and WLAN), and reported X-band implementations frequently sho w limited ef cienc y or insuf cient frequenc y selecti vity . Recent studies ha v e in v estig ated h ybrid strate gies that inte grate fractal geometries with ground modications or slotting to achie v e dual-band or multiband functionality . F or e xample, K och and Mink o wski fractal patches coupled with DGS ha v e sho wn impro v ed impedance bandwidth and reduced size, b ut often at the cost of comple x geometries and f abrication c h a llenges. Other w orks relying solely on DGS-based enhancements tend to impro v e impedance characteristi cs b ut lack suf cient frequenc y selecti vity or compactness for X-band applications. These g aps moti v ate the need for a design that combines miniaturization, ef cienc y , and high selecti vity within a single, compact architecture. T o o v er come these limitations, a miniaturised circular fractal patch antenna with an inte grated DGS for dual-band X-band operation has been proposed in this w ork. The proposed antenna uses circular fractal slotting to lengthen the ef fecti v e current path length and introduce multiple resonances, the central diamond-shaped slot to realize capaciti v e loading to impro v e impedance matching, and optimized rectangular DGS with symmetric notches to suppress surf ace w a v es and impro v e the frequenc y selecti vity of the antenna. The no v elty of this design is the syner gistic combination of fractal slotting and DGS to achie v e dual-band operation with deep return loss notches, stable broadside radiation and high radiation ef cienc y in an ultra-compact footprint. The contrib utions of this w ork are threefold: − De v elopment of a compact circular fractal antenna geometry optimized for dual-band X-band performance. − Inte gration of a mid-diamond slot and DGS to simultaneously enhance impedance matching, radiation ef cienc y , and selecti vity . − Experimental v alidation of the proposed antenna, demonstrating dual resonances in the X-band with superior return loss, v oltage st anding w a v e ratio (VSWR), g ain, and ef cienc y compared to con v enti on a l fractal or DGS-only counterparts. Se v eral recent w orks ha v e e xplored dual-band and fractal antenna designs rele v ant to X-band applications. R ajpoot et al. [1] presented an aperture-coupled diagonal square fractal antenna with a lo w prole operating at 5.9 GHz and 9.5 GHz, deli v ering g ains of 2.43 dBi and 7.88 dBi. The design att ains good ef cienc y b ut occupies a comparati v ely lar ger footprint, and the notable g ain increase appears mainly in the higher band. P ande et al. [2] introduced a dual-band metasurf ace patch with v aractor and PIN-diode tuning at 2.6 GHz and 3.4 GHz, achie ving a g ain of 7.5 dBi; these operating bands are belo w the X-band. Cheng et al. [3] presented a dual-band shared-aperture antenna spanning 2.09–11.61 GHz and 21.6–29.6 GHz. Although the rst range includes the X-band, the wide co v erage constrains tar geted dual-band optimization. K umar et al. [4] designed a e xible coplanar w a v e guide (CPW)-fed antenna for 10.5–12 GHz with 6 dBi g ain, focusing on circular polarization rather than compact dual-band performance. Mianji et al. [5] reported a fractal triangular microstri p antenna at 3.0 GHz and 5.8 GHz with e xcellent return loss, b ut outside X-band. Jenath et al. [6] presented multi-band h ybrid fractal antenna co v ering 2.12–2.95 GHz and 4.82–5.95 GHz, lacking X-band operation. Attioui et al. [7] presented a Sierpinski carpet fractal antenna at 4.88, 9.62, and 10.03 GHz, close to the desired X-band range though with weak er matching in rst band. Marzouk et al. [8] de v eloped a printed multiband fractal triangular antenna (1.84–5.79 GHz), not tar geting X-band. La v an ya and K umari [9] designed a dual-band fractal patch with reacti v e impedance surf ace (RIS) and Mushroom unit cell (MUC) at 2.4 GHz and 3.35–3.71 GHz, unsuitable for X-band. Al-Ra we et al. [10] presented a dual band fractal rectenna for ener gy harv esting at 2.45 GHz and 5.8 GHz, which does not tar get the X-band. Bui et al. [11] reported a dual band, dual polarised slotted patch operating at 2.45 GHz and 5.25 GHz. Sood and Rai [12] reported a compact fractal patch co v ering 8.62 GHz to 22.4 GHz; ho we v er , the achie v ed g ain is lo wer than typical X–band designs. Srikanta and P ac h i yaannan [13] introduced a dual-band fractal antenna through truncated he xagonal rings (4.6–6.7 GHz, 12–14.2 GHz, missing desired X-band points). Shankar and Upadh yay [14] proposed a fractal monopole antenna (7.95–12.64 GHz) with dual polarization, co v ering X-band b ut without return loss data. K umar et al. [4] designed a e xible CPW antenna for X-band (10.5–12 GHz) with 6 dBi g ain and AR < 3 dB on a compact 27 × 28 mm polyimide substrate, ideal for conformal uses. Ho we v er , the operational band is narro w compared to wideband needs. Miniaturized cir cular fr actal patc h antenna with ... (Raju Thommandru) Evaluation Warning : The document was created with Spire.PDF for Python.
374 ❒ ISSN: 2252-8814 Raja v el and Ghoshal [15] proposed a compact multiband recongurable antenna with art icial magnetic conductor (AMC), co v ering 8.7, 10.5, and 11.4 GHz, achie ving 3.29 dB g ain enhancement, 87% ef cienc y , and SAR as lo w as 0.0594 W/kg. The lar ger size and PIN diode biasing netw ork are dra wbacks. Singh et al. [16] de v eloped an articial neural netw ork (ANN)-based O-shaped slotted microstrip patch antenna with –26.44 dB return loss at 1.68 GHz and accurate bandwidth pre diction (1.308% error), b ut it tar gets L-band rather than X-band. Y aminisasi et al. [17] reported a sh- tail fractal monopole with defected partial ground structure (DPGS) that operates o v er 2 . 5 – 4 . 2 GHz and 7 – 9 . 8 GHz with g ains approaching 5 dBi . The design is compact, yet it does not align precisely with the tar geted X-band centers at 8 . 8025 GHz and 10 . 3700 GHz . Elsalam et al. [18] introduced a lo w specic absorption rate (SAR) semicircular slot antenna with DGS co v ering 1 . 8 – 3 . 7 GHz and 4 . 05 – 5 . 5 GHz and achie ving a peak g ain of 8 . 5 d B i ; its focus is 5G rather than X-band. Mohini and Sar a v a nakumar [19] presented a wearable high-g ain DGS antenna tailored to 6 GHz body-area links, which remains under X-band. Dharani et al. [20] report that mo ving from a full ground to a restricted ground in a multiband patch impro v es matching and bandwidth by altering the current paths beneath the ra d i ator . Chakraborty et al. [21] apply similar ground engineering in a compact unied S-band monopole multi-input multi-output (MIMO) to raise isolation b ut the g ain can come with ef cienc y loss and sensiti vity to de vice ground and user proximity . Xu and W ang [22] reduce coupling in dual-band WLAN MIMO using a WM-shaped DGS which achie v es isolation impro v ement through slot design that operates as a frequenc y-selecti v e current lter at dif ferent bands. The structure of the w ork is detai led as follo ws. Section 2 presents the antenna geometry and the design w orko w . Section 3 pro vides simulation and measurement results. Section 4 distills design insights and salient observ ations. Section 5 concludes with application conte xts and brief directions for future in v estig ation. 2. SYSTEM METHODOLOGY This w ork de v elops a compact circular fractal patch antenna with a DGS for dual-band operation within the X-band. The methodology co v ers three stages: i) geometric formulation of the radiating element and ground plane, ii) full-w a v e electromagnetic modeling, and iii) simulation-dri v en as sessment of impedance and radiation characteristics. The patch emplo ys circular fractal slotting to lengthen the surf ace current path, while a centrally placed diamond-shaped aperture introduces capaciti v e loading that assists impedance matching. The ground plane incorporates a DGS to suppress surf ace w a v es and to widen the usable bandwidth. The o v erall conguration appears in Figure 1; the circular fractal patch is highlighted in Fi gure 1(a) and the corresponding ground topology in Figure 1(b). (a) (b) Figure 1. Proposed antenna conguration: (a) circular fractal patch with a mid-diamond slot that increases the ef fecti v e current path and aids matching and (b) DGS that mitig ates surf ace w a v es and enlar ges bandwidth Figure 2 summarizes the design e v olution of the ground plane that is used to tune input impedance and radiation beha vior . P anels illustrate the proposed ground, a full ground, a half ground, and a ring–type DGS. A fully metallized ground serv es as the reference and e xhibits limited frequenc y selecti vity with stronger surf ace-w a v e content. Reducing the ground to a partial layout impro v es matchi ng, b ut it can raise inter -modal coupling. Introducing a ring-type DGS adds periodic stopbands and perturbs ground currents, which lo wers surf ace-w a v e ener gy and enhances i solation. The nal design combines a partial ground clearance with patterned DGS apertures so that the return path is shaped and the ef fecti v e electrical length increases. This Int J Adv Appl Sci, V ol. 15, No. 1, March 2026: 372–383 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Adv Appl Sci ISSN: 2252-8814 ❒ 375 sequence from simple to patterned grounds steers the current distrib ution, enables rob ust dual-band e xcitation, and maintains a stable main lobe without e xcessi v e intrusion into the ground re gion. Figure 2. Design e v olution of the ground plane 2.1. Antenna geometry and design principle The radiating patch in Figure 1(a) adopts a circular fractal layout that lengthens the ef fecti v e cur rent path while preservi ng the footprint, which f acilitates multiple resonances within the X-band. A centrally placed diamond-shaped slot pro vides capaciti v e loading that impro v es input matching and allo ws ne control of the resonant frequencies. The defected ground in Figure 1(b) consists of a rectangular aperture of 12 mm × 8 mm with tw o symmetric notches of 4 mm × 3 mm . This pattern perturbs the ground currents, reduces surf ace-w a v e content, and broadens the impedance bandwidth. The antenna is realized on a substrate of 26 mm × 22 mm with thickness 1 . 6 mm . The circular patch has an ef fecti v e radius of 7 . 5 mm , fed by a 3 mm wide and 10 mm long microstrip line for 50 Ω matching. These optimized dimensions ensure compactness while maintaining stable dual-band resonance. The antenna is realized on an FR-4 subs trate with relati v e permitti vity ε r = 4 . 4 and loss tangent 0 . 02 . The fundamental resonance of the circular patch is estimated using (1). Optimized geometric parameters are summarized in T able 1 to support reproducibility and design transparenc y . f r = 1 . 8412 · c 2 π a e √ ε r (1) T able 1. Optimized dimensions of the proposed antenna P arameter V alue (mm) Substrate length ( L sub ) 26 Substrate width ( W sub ) 22 P atch radius ( a p ) 7.5 Diagonal of mid-diamond slot 3.0 Ground-plane slot length ( L g ) 12 Ground-plane slot width ( W g ) 8 Feed notch length ( L n ) 4 Feed notch width ( W n ) 3 Microstrip width ( W f ) 3.0 Microstrip length ( L f ) 10 Substrate thickness ( h ) 1.6 Miniaturized cir cular fr actal patc h antenna with ... (Raju Thommandru) Evaluation Warning : The document was created with Spire.PDF for Python.
376 ❒ ISSN: 2252-8814 2.2. Defected gr ound structur e integration After xing the circular patch geometry , a DGS is etched beneath the radiator to control guided currents on the ground plane . The perturbation weak ens surf ace-w a v e channels, which reduces dielectric loss and increases the usable impedance bandwidth. The modied current paths also raise radiation ef cienc y and help limit back-lobe le v els. The slot pattern reshapes the return path and introduces an equi v alent inductance L and capacitance C set by the slot length, g ap spacing, and coupling to the patch. The DGS therefore acts as a resonant cell with a band-stop response. Its cut-of f frequenc y is (2). f c = 1 2 π √ LC (2) Where L and C summarize the electromagnetic storage produced by the defect geometry . By selecting the slot dimensions to tar get the undesired spectral re gion, the band-stop action suppresses parasitic harmonics and impro v es isolation between the dual resonant bands. 2.3. Impedance matching and r etur n loss W ith the DGS in place, the input impedance Z in is tuned to w ard the 50 Ω feed. An y departure from Z 0 = 50 Ω produces a reected component quantied by the v oltage reection coef cient (3). Γ = Z in − Z 0 Z in + Z 0 (3) The return loss in decibels follo ws from the magnitude of Γ (4). R L (dB) = − 20 log 10 | Γ | (4) T w o geometric le v ers are used to meet the match. First, circular fract al slotting increases the e f fecti v e current path, which shifts the resonant poles and balances the resisti v e and reacti v e parts of Z in . Second, the mid-diamond aperture adds capaciti v e loading that of fsets the inducti v e content introduced by the fractalization. The DGS pro vides a third le v er by altering ground-plane currents, which enables ne control of the input reactance. T ogether these elements yield stable multi-resonant beha vior across the tar geted X-band subranges with lo w | Γ | and impro v ed R L . 2.4. Radiation efciency Radiation ef cienc y η rad quanties the fraction of the input po wer that emer ges as radiated po wer . It is dened as (5). η rad = P rad P in (5) W ith P rad the radiated po wer and P in the accepted input po wer . In printed antennas the dominant loss channels arise from nite conductor conducti vity , dielectric loss t angent, and ener gy bound to surf ace w a v es. The present layout mitig ates these channels by tw o mechanisms. First, the circular fractal slot redistrib utes surf ace currents and lo wers current cro wding near fe ed transitions, which reduces ohmic loss. Second, the DGS weak ens surf ace-w a v e propag ation so that a lar ger share of the stored ener gy couples into space w a v es rather than being guided within the substrate. T ogether these ef fects raise η rad across the operating band. 2.5. Gain and dir ecti vity Antenna g ain combines directi vity and ef cienc y . It is written as (6). G = η rad · D (6) Where D denotes the directi vity that follo ws from the angular po wer distrib ution independent of loss. In the proposed patch, the circular fractal motif guides the current to w ard a balanced aperture eld, which impro v es D and limits pattern distortion. The mid-diamond slot contrib utes capaciti v e loading that renes the phase of the aperture eld. The DGS complements these actions by reducing po wer leakage into the substrate and by trimming back radiation, so the realized g ain impro v es without sacricing beam stability . Int J Adv Appl Sci, V ol. 15, No. 1, March 2026: 372–383 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Adv Appl Sci ISSN: 2252-8814 ❒ 377 2.6. Simulation and e v aluation The design w as e v aluated in Ansys HFSS 20 23 R2. Simulations e xtracted S 11 , VSWR, g ain, radiation ef cienc y , impedance bandwidth, and f ar -eld patterns. The w orko w used adapti v e meshing with con v er gence on the comple x input impedance to ensure mesh independence of the reported gures. The simulated resonant frequencies were compared with the analytical estimate in (1), and the DGS notch beha vior w as assessed ag ainst the cut-of f prediction in (2). The tw o checks were consistent within the e xpected limits set by substrate dispersion and fringe elds, which indicates that the equi v alent models capture the go v erning ph ysics of the radiator and ground. The resulting dataset pro vides a reproducible reference for subsequent f abrication and for studies that seek to retune the dual-band response by modifying the slot geometry or the DGS cell dimensions. 3. RESUL TS This section reports the measured performance of the antenna within the X-band. The discussion links input impedance metrics to f ar -eld beha vior and ef cienc y . These parameters are used to assess suitability for selecti v e dual-band operation. 3.1. Retur n loss analysis Figure 3 sho ws the measured input reection coef cient from 8 GHz to 12 GHz. A dual-band response is obtained. The rst operat ing band e xtends from 8 .637 GHz to 9.173 GHz, with a resonance at 8.8025 GHz where the return loss reaches − 22 . 0267 dB. This le v el is well under the − 10 dB criterion and indicates a strong impedance match. The second operating band co v ers 10.121 GHz to 10.956 GHz, with a resonance at 10.3700 GHz and a return loss of − 25 . 2864 dB. The tw o deep notches reect high frequenc y selecti vity , while the fractional bandwidths of each band support multi-channel operation. The circular fractal slotting and the DGS contrib ute to these results by enlar ging the ef fecti v e current path and suppressing surf ace w a v es, which impro v es the impedance locus around both resonances. The comparison in Figure 4 indicates good alignment between simulation and measurement. Minor shifts in the notch frequencies are consistent with f abrication tolerances, substrate parameter spread, and connector parasitics. The preserv ation of both resonances conrms that the modeled mechanisms go v erning the dual-band response are realized in hardw are. 3.2. VSWR analysis The VSWR w as measured o v er same 8 to 12 GHz range and is sho wn in Figure 5. The rst resonance at 8.8025 GHz yields a VSWR of 1.1720, which corresponds to S 11 = − 22 . 0267 dB. The second resonance near 10.3750 GHz records a VSWR of 1.1199, consistent with S 11 = − 25 . 2864 dB. Across 8.637–9.173 GHz and 10.121–10.956 GHz the VSWR remains under 2, indicating rob ust impedance matching throughout both passbands. The close correspondence between the VSWR minima and the return loss notches v alidates the matching strate gy that combines fractal slotting on the patch with a patterned ground. Figure 3. Measured S 11 with resonances at 8.8025 GHz ( − 22 . 0267 dB) and 10.3700 GHz ( − 25 . 2864 dB) Miniaturized cir cular fr actal patc h antenna with ... (Raju Thommandru) Evaluation Warning : The document was created with Spire.PDF for Python.
378 ❒ ISSN: 2252-8814 Figure 4. Simulated and measured S 11 sho wing close agreement at 8.8025 GHz and 10.3700 GHz Figure 5. Measured VSWR across 8–12 GHz with minima of 1.1720 at 8.8025 GHz and 1.1199 at 10.3750 GHz 3.3. Gain and dir ecti vity analysis f or plot 1 The three-dimensional radiation beha vior at 8.8025 GHz is summarized in Figure 6. From Figure 6(a), the realized peak g ain i s 4.81698 dB, which indicates ef cient con v ersion of a ccepted po wer into radiation in the preferred look direction. From Figure 6(b), the corresponding directi vity is 6.22480 dB, which reects a concentrated main beam. The dif ference between directi vity and g ain follo ws from conductor and dielectric losses in the FR4 substrate with loss tangent 0 . 02 . The three-dimensional patterns e xhibit a clean broadside main lobe with lo w sidelobe le v els, so the transmitted po wer is lar gely conned to the intended co v erage sector . 3.4. Gain and dir ecti vity analysis f or plot 2 Figure 7 reports the radiation characteristics at the second resonance of 10.3700 GHz. The peak g ain equals is 3.41829 dB as sho wn in Figure 7(a), referenced to an isotropic radiator . The peak directi vity is 5.39011 dB as sho wn in Figure 7(b), which conrms a focused broadside beam. The g ap between directi vity and g ain is consistent with residual ohmic and dielectric loss. The radiation surf aces sho w smooth beam contours with lo w sidelobes, which supports short to medium range X-band links where pattern stability and limited interference are required. 3.5. T w o-dimensional gain and dir ecti vity tr ends Figure 8 presents t he frequenc y e v oluti on of g ain and directi vity o v er 8–12 GHz. At 8.8025 GHz, the measured peak g ain is 4.81698 dB and the dir ecti vity is 6.22480 dB. The g ap is about 1.41 dB and follo ws from conductor and dielectric loss. At 10.3700 GHz, the g ain is 3.41829 dB and the directi vity is 5.39011 dB, gi ving a g ap of about 1.97 dB. Across the scanned band the curv es are smooth, with directi vity abo v e 5 dB near both resonances and g ain abo v e 3 dB, which satises the selecti vity requirements for the intended X-band operation. Int J Adv Appl Sci, V ol. 15, No. 1, March 2026: 372–383 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Adv Appl Sci ISSN: 2252-8814 ❒ 379 (a) (b) Figure 6. Three-dimensional patterns at 8.8025 GHz: (a) g ain = 4 . 81698 dB and (b) directi vity = 6 . 22480 dB (a) (b) Figure 7. Three-dimensional patterns at 10.3700 GHz: (a) peak g ain = 3 . 41829 dB and (b) peak directi vity = 5 . 39011 dB Figure 8. T w o-dimensional g ain and directi vity across 8–12 GHz 3.6. Radiation efciency analysis The antenna radiation ef cienc y o v er the 8–12 GHz is sho wn in Figure 9. It sho ws stable perform ance in both w orking bands. At the rst resonance of 8.8025 GHz, t he measured ef cienc y is 63.51%, indicating that nearly tw o-thirds of the input po wer is con v erted into radiated ener gy , with the remainder lost mainly due to dielectric losses in the FR4 substrate ( tan δ = 0 . 02 ) and minor conductor losses in the feed and patch metallization. At the second resonance of 10.3750 GHz, ef cienc y impro v es to 72.58%, reecting reduced surf ace w a v e losses and a more f a v orable current distrib ution, which also e xplains the corresponding g ain increase in this band. Across the measured spectrum, ef cienc y remains abo v e 40%, e v en outside the Miniaturized cir cular fr actal patc h antenna with ... (Raju Thommandru) Evaluation Warning : The document was created with Spire.PDF for Python.
380 ❒ ISSN: 2252-8814 resonances, conrm ing that the antenna maintains funct ional radiation capability o v er a wide span. These results sho w that the design is al w ays ef cient in both bands with resonant points, a f act that matches the operational requirements of highly selecti v e X-band application. Figure 9. Measured radiation ef cienc y with 63.51% at 8.8025 GHz and 72.58% at 10.3750 GHz 3.7. F abricated pr ototype and measur ement setup The f abricated antenna is sho wn in Figure 10. A board on FR -4 w as etched using standard PCB steps, an SMA w as soldered to the microstrip feed, and measurements were tak en on a v ector netw ork analyzer . Figure 10(a) details t he top metallization with the circular fractal radiator and mid-diamond slot, while Figure 10(b) depicts the defected ground on the re v erse side. The measured S 11 follo ws the simulated curv e across the band, supporting the selected geometry . (a) (b) Figure 10. F abricated antenna prototype: (a) top vie w with circular fractal patch and mid-diamond slot and (b) bottom vie w with DGS 4. DISCUSSION The proposed miniaturized circular fractal patch antenna with DGS w as e xperimentally e v aluated across the 8–12 GHz X-band to establish its suitability for compact high-selecti vity dual-band operation. Measured return loss ( S 11 ) re v ealed tw o distinct resonances: 8.637–9.173 GHz (centered at 8.8025 GHz, –22.0267 dB) and 10.121–10.956 GHz (centered at 10.3700 GHz, –25.2864 dB), both e xceeding the standard –10 dB impedance-matching criterion. The combined act ion of the circular fractal slotting, which lengthens the current path, and the optimized DGS, which suppresses surf ace w a v es and e v ens the ground return, produces deep return-loss notches and stable dual-band beha vior . VSWR remains under 2 in both passbands, with minima of 1.1720 at 8.8025 GHz and 1.1199 at 10.3750 GHz, which conrms ef fecti v e impedance control. Radiation analysis yields a peak g ain of 4.82 dB with directi vity of 6.22 dB at 8.8025 GHz, and 3.42 dB Int J Adv Appl Sci, V ol. 15, No. 1, March 2026: 372–383 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Adv Appl Sci ISSN: 2252-8814 ❒ 381 g ain with 5.39 dB directi vity at 10.3700 GHz. The g ap between directi vity and g ain follo ws from dielectric and conductor losses in FR4 with loss tangent 0.02. Three-dimensional patterns at both resonances sho w a dominant broadside main lobe and lo w sidelobes, which maintains beam stability and concentrates radiated po wer . Using standard FR4 of thickness 1.6 mm and ε r = 4 . 4 supports lo w-cost PCB f abrication and straightforw ard inte gration with RF front ends and arrays. Measured radiation ef cienc y is 63.51% at 8.8025 GHz and 72.58% at 10.3750 GHz. Outside the resonant peaks the ef cienc y stays abo v e 40%. The compact footprint of 22 mm × 26 mm suits embedded X-band radar modules, satelli te terminals, and portable defense radios. A brief comparison with recent fractal and DGS designs highlights the distinct operating re gime of the present antenna. The Sierpinski carpet fractal with DGS in [23] tar gets 2.45 and 5.8 GHz for industrial, scientic, and medical (ISM) use. The K och fractal with DGS in [24] co v ers 1.9–4.3 GHz with 4 dBi g ain and 77% bandwidth. A lo w-prole wearable DGS antenna in [19] is optimized near 6 GHz. The K och–he xagonal combined circular radiator in [25] spans 2.38–5.80 GHz, and the sh-tail fractal monopole in [17] pro vides dual broadband around 3.22, 7.64, and 9.41 GHz. In contrast, the proposed layout operates in the X-band with resonances at 8.8025 and 10.3700 GHz, e xhibits deep return loss of − 22 . 0267 and − 25 . 2864 dB, deli v ers competiti v e g ains of 4.82 and 3.42 dB, and retains a compact 22 mm × 26 mm form f actor . As summarized in T able 2, this combination of selecti vity , ef cienc y , and size positions the design for high-frequenc y radar and satellite links that require miniaturization without comple x f abrication. Although the prototype meets the tar get specications, the FR4 substrate introduces dielectric los s that slightly lo wers realized g ain and radiation ef cienc y relati v e to lo w-loss laminates. The geometry is tuned to tw o X-band sub-bands, so broader mult iband co v erage w ould require systematic scaling and substrate renement. Future w ork will e xamine lo w-loss materials to raise ef cienc y , recongurable loading for tunable operation, and array-le v el inte gration to enable beam steering. En vironmental testing o v er temperature and humidity ranges will also be conducted to quantify long-term stability and to conrm readiness for eld deplo yment. T able 2. Optimized dimensions of the proposed antenna Author (year) Operating bands (GHz) Size (mm) Gain (dBi) Ef cienc y (%) Sierpinski carpet fractal + DGS [23] 2.45 / 5.8 40 × 40 3.2–5.1 70 K och fractal antenna + DGS [24] 1.9–4.3 38 × 34 4.0 77 Fish-tail fractal monopole [17] 3.22 / 7.64 / 9.41 30 × 28 5.0 68 Fle xible CPW -fed [15] 10.5–12 27 × 28 6.0 – Proposed w ork 8.64–9.17 / 10.12–10.96 22 × 26 4.82 / 3.42 63.5 / 72.6 5. CONCLUSION This research presented a compact circular fractal patch antenna with a DGS for selecti v e dual-band operation in the X-band. The geometry combines a circular fractal motif with a mid-diamond slot to lengthen the current path and to impro v e input matching within a 22 mm × 26 m m footprint. Measurements v erify tw o resonances. At 8.8025 GHz the antenna achie v es S 11 = − 22 . 0267 dB, VSWR = 1 . 1720 , g ain = 4 . 82 dB, and radiation ef cienc y = 63 . 51% . At 10.3700 GHz the results are S 11 = − 25 . 2864 dB, VSWR = 1 . 1199 , g ain = 3 . 42 dB, and radiation ef cienc y = 72 . 58% . Both passbands, 8.637–9.173 GHz and 10.121–10.956 GHz, e xhibit broadside patterns with lo w sidelobes and smooth g ain–directi vity beha vior . The data indicate strong impedance control, high ef cienc y for an FR4 substrate, and ef fecti v e miniaturization. In vie w of the measured performance and s ize, the design is well suited to X-band radar front ends, satellite links, and compact defense transcei v ers that require stable matching and controlled radiation within constrained form f actors. FUNDING INFORMA TION No funding w as recei v ed for this w ork. A UTHOR CONTRIB UTIONS ST A TEMENT This journal uses the Contrib utor Roles T axonomy (CRediT) to recognize indi vidual author contrib utions, reduce authorship disputes, and f acilitate collaboration. Miniaturized cir cular fr actal patc h antenna with ... (Raju Thommandru) Evaluation Warning : The document was created with Spire.PDF for Python.