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A re-configurable meta surface based linear to linear polarization converter is presented.

International audience; This paper describes the design and development of a highly directive planar end-fire array using arc dipoles as the array elements. The inter element spacing, shape, and size of the array elements are optimized for maximum directivity and gain. The array is printed on a substrate whose dimensions are also optimized for better performance. The overall length of the proposed six element array is 1.9λ, giving directivity and gain values as 12.0 dBi and 10.2 dB respectively at 5.8 GHz.

The performance of printed wideband antennas has to be optimized both in frequency and time domains, to qualify for UWB applications. This is especially true in multi-resonant antenna topologies where the excitation of different modes can change phase centers and radiation patterns with frequency. The study presented in this chapter intends to demonstrate the simulation and experimental design for the time domain characterization of UWB antennas. Modeling the antenna as a linear time-invariant system with transfer function and impulse response, distortion caused to a nanosecond pulse is analyzed. Two planar monopole antenna designs are considered for the comparative study: the SQMA and RMA. SQMA is a traditional CPW-fed monopole design with ground modifications for ultra wide-bandwidth. RMA is a rectangular CPW-fed monopole with an impedance transformer arrangement at the antenna feed. RMA maintains constant impedance over the entire UWB and contributes towards maintaining uniformity in the radiation patterns over the entire frequency band by its design. Transfer function measurements are performed for both the azimuthal and elevation planes and the impulse responses are deduced by performing IFFT. Parameters such as FWHM and ringing are computed from the impulse response for the performance comparison. To evaluate the influence of the antenna geometry on a transmitted/received pulse, the impulse responses are convoluted with a standard UWB pulse. The time-domain distortion for the designs is then compared by computing the Fidelity parameter.

Obtaining the large statistically independent training datasets for effective classification in through-wall radar studies is always remaining as a challenging task due to the practical and monetary difficulties in the collection of real -time experimental data. Therefore, the development of accurate but computationally less complex simulation models that combine human micro-Doppler data with through-wall propagation effects is instrumental in generating such large training datasets, which can improve the classification accuracy. The proposed research work has presented a simple and accurate simulation methodology which combines human Radar Cross Section (RCS) modeling using primitive based techniques and Finite Difference Time Domain (FDTD) simulation of walls. The human radar scatterings are analyzed in the Line of Sight (LOS) conditions and through-wall scenarios. The simulated spectrograms in the LOS conditions are corroborated by measurement data collected using a monostatic continuous wave Radar. The simulated spectrograms in through-wall conditions shows that the distortions in the Doppler frequencies from different body segments are minimal but the magnitude response of the doppler spectrogram is affected due to attenuation and fading

This paper describes a method to achieve superdirectivity in dipole array by employing only two elements, a driven element and a shorted parasitic element. To maximize the directivity, initially the array is assumed to be fully driven and the required current excitation coefficients are calculated. Then the parasitic elements are added such that the parasitic array achieves almost the same directivity as the fully driven array when optimal loads (inductive, capacitive, short) are connected to the parasitic element. It is observed that a shorted parasitic element placed very near to the driven element could enhance the directivity to a high value. The directivity can be further enhanced by placing the elements on a trapezoidal shaped substrate. A two element parasitic dipole antenna array with a directivity of 9.17 dBi is presented.

Design of a multi-port compact antenna for RF energy harvesting systems is presented in this paper. It consists of an E-shaped coaxial-fed microstrip antennas operating at 958MHz and 2.35GHz each placed on all sides of a cube. The advantage of this approach is that power can be received from all directions and at different polarizations, thereby enhancing the total harvested power. The overall size of the antenna is only 60mm x 60mm x 50mm. The isolation between various ports is below −30 dB ensuring minimum interference between them.

Printed wideband antennas, if not optimised both in frequency and time domain, often fail to qualify for UWB applications. This is primarily observed in designs based on multiple resonances. The excitation of different modes causes variation in the position of the antenna phase centre and radiation patterns with frequency. In this paper, we propose a novel compact UWB antenna design with optimised resonances within the 3.1 – 10.6 GHz band. The design comprises of a rectangular CPW-fed monopole. The novelty in the design lies in the impedance transformer arrangement at the antenna feed which not only maintains constant impedance over the wide band but contributes towards maintaining uniformity in the radiation patterns over the frequency band. The proposed antenna is characterized, both in the frequency and time domain, confirming its suitability for UWB operation. The impedance bandwidth of the antenna is from 2.9-11.5GHz with an omni–directional radiation pattern over the full band, unlike most of the planar UWB antennas reported in literature whose pattern deteriorates particularly at the upper end of the band. It also exhibits appreciable polarization purity and radiation efficiency. The time domain parameters, Full Width Half Maxima (FWHM) and Ringing, are computed from the measured antenna transfer function. The computed Fidelity of the transmitted pulses indicates superior pulse handling capabilities. The antenna is suitable for commercial hand held devices as its PCB area is just 30 x 12mm2 when fabricated on the FR4 substrate with permittivity 4.4 and height 1.6mm.

Memristors have been recently proposed as an alternative to incorporate switching along with traditional CMOS circuits. Adaptive impedance and frequency tuning are an essential and challenging aspect in communication system design. To enable both, a matching network based on switchable capacitors with fixed inductors is proposed in this paper where the switching is done by memristive switches. This paper analyzes the operation of memristors as a switch and a matching network based on memristors which adaptively tunes with impedance and frequency. With three capacitor banks of each 0.5 pF resolution and two fixed inductors, matching for antenna impedance ranging from 20 to 200[Formula: see text]Ohms and for frequencies ranging from 0.9 to 3.2[Formula: see text]GHz is reported. Thereafter, an adaptive planar band-pass filter is implemented on CMOS technology with two metal layers. This adaptive frequency tunable band-pass filter uses a [Formula: see text] network with resonator tanks in both arms that operates at 2.45 GHz. It is tunable from 2.8[Formula: see text]GHz to 7.625[Formula: see text]GHz range. This tunability is achieved using tunable spiral inductor based on memristive switches. The proposed filter layout is implemented and simulated in ANSYS Designer. The initialization and the programming circuitry to enable adaptive switching of the memristive devices has to be addressed. Since RF memristive devices are not commercially available, circuit level simulations are done as a proof of concept to validate the expected results.

RF energy harvesting is the process of acquiring ambient RF energy and converting it into a suitable form for storage for powering low power devices. This paper describes a low cost rectifier operating at 1.8 GHz for energy harvesting applications. Rectifier is fabricated on lossy FR4 substrate and better impedance matching is achieved by incorporating a short stub and two open stubs. It has an efficiency of 63% and an output voltage of 0.8V at 0dBm input power. Source pulling technique is used to optimize the design. Compactness as well as low cost make this rectifier attractive for RF energy harvesting

A novel J shaped slot antenna for ultra-wide band (UWB) WiMedia is presented. The proposed antenna is designed using a microstrip to slot line cross transition on FR4 substrate with permittivity 4.4. Return loss of the antenna is from 2.8- 13GHz and occupies just 28x10 mm 2 on the PCB. Radiation patterns are stable and omni-directional. Antenna transfer function and impulse response are analyzed to study the pulse handling capability of the antenna.

Memristors have been recently proposed as an alternative solution to incorporate switched behavior along with traditional CMOS circuits. Furthermore, with the advent of technology, adaptive impedance and frequency tuning is essential in communication devices. To enable both tuning, a matching network based on switchable capacitors with fixed inductors is proposed in this paper. Here, switching is done by means of memristive switches. This paper analyzes the working of memristor as a switch and a matching network based on memristors which adaptively tunes with impedance and frequency. With 3 capacitor banks of each 0.5 pF resolution and 2 fixed inductors, matching for antenna impedance ranging from 20 to 200 Ohms and for frequencies ranging from 0.9 to 3.2 GHz is reported.

The paper presents an overview of compact microstrip antennas for RF energy harvesting systems. A detailed literature review of several compact antennas suitable for energy harvesting systems is discussed along with different antenna polarizations. Various size reduction techniques for antennas along with trade-offs are summarized and compared

The Weaver technique or the third method of generation of single sideband modulation with suppressed carrier (SSB-SC) amplitude modulation (AM) signals is one such algorithm which looks deceptively simple when compared with the more analytically tractable phase-shift method. With the advent of digital signal processing (DSP) techniques such as the CORDIC (coordinate rotation digital computer) algorithm, an elegant low-complex implementation of the Weaver technique is now feasible, which necessitates a better understanding of the underlying principle. However, despite its popularity, it is not explained in detail in conventional text books on communication engineering and in general literature. Using the background theory of complex signals (I and Q), in this paper, we have depicted the entire operation graphically. Combined with necessary mathematics and implementation ideas, this will be a comprehensive tutorial on the third method of SSB-SC generation and should motivate students to look at the ...

Agriculture remains the sector which contributes the highest to India's GDP. But, when considering technology that is deployed in this field, we find that the development is not tremendous. After consulting with the Kerala Agricultural University, Mannuthy and Kerala Rice Research Station, Vytilla, we identified a few fundamental issues that are faced by the paddy farmers today. It includes the problem of over or under watering and the need for regular manual irrigation. Furthermore, when it comes to rice, which is the staple crop of Kerala, there does not exist a system for automatically monitoring the diseases associated with the rice species, and checking whether the crop is supplied with ample amount of nutrients. In this paper, we have devised a means for cost-effective automated irrigation and fertigation along with MATLAB based image processing for identifying the rice diseases and nutrient deficiencies. Here, we are focusing on two important nutrients, namely magnesium and nitrogen. The hardware consists of a Raspberry Pi, DHT11 temperature and humidity sensor and solenoid valves. Furthermore, the proposed model enables the farmer to monitor weather conditions using an Android Application, with which he also has a choice to override the system if required.

This paper proposes and analyses a circularly polarized square patch antenna with an improved axial ratio bandwidth covering a frequency of 1.665GHz to 1.845GHz. The antenna attains circular polarization using the perturbations — truncated corners and well-shaped slots embedded on the patch. The results indicate that the antenna attains desirable axial ratio (below 3dB) for a wide elevation range of −134° to 47°. When compared to conventional truncated corner circularly polarized square patch antenna, the axial ratio bandwidth of the proposed antenna is increased by 30MHz. The antenna model is fabricated, tested and the measured results show a high correlation with the predicted ones.

Analysis of a series-parallel coaxial stub type balun having a wider operating bandwidth is discussed in this paper. The balun, operating for a frequency range of 180 to 400MHz, is made using a pair of RG58C/U coaxial cables and is integrated with a simple dipole antenna. Simulations are done in ANSYS HFSS and the results of coax fed dipole with and without balun are compared. Results show that the balun is successful in cancelling or choking off the imbalance current. The SPCS type balun fed dipole antenna is fabricated at 180MHz and measurements are carried out.

A compact fractal antenna which is both frequency and polarization reconfigurable is presented in this paper. The proposed paper presents a Minkowski fractal microstrip antenna loaded with slots operating at a frequency of 1.7GHz. Frequency and polarization re-configurability is achieved by introducing four slots on the fractal shaped patch with PIN didoes as switches across them. By varying the ON and OFF conditions of PIN diodes, the antenna is able to operate in 5 different frequencies and as well as for two different polarization.

A compact ultra-wideband (UWB) printed slot antenna is described, suitable for integration with the printed circuit board (PCB) of a wireless, universal, serial-bus dongle. The design comprises of a near-rectangular slot fed by a coplanar waveguide (CPW) printed on a PCB of size 20 30 mm 2 . It has a large bandwidth covering the 3.1- 10.6 GHz UWB band, with omnidirectional radiation patterns. Further, a notched band centered at 5.45 GHz wireless local area network bands is obtained within the wide bandwidth by inserting a narrow slot inside the tuning stub. Details of the antenna design are described, and the experimental results of the constructed prototype are presented. The time domain studies on the antenna shows a linear phase response throughout the band except at the notched frequency. The transient analysis of the antenna indicates very little pulse distortion confirming its suitability for high speed wireless connectivity. © 2009 Wiley Peri

A printed semi-elliptic monopole slot antenna for use in ultrawideband (UWB) communication systems is presented. The antenna features a coplanar waveguide signal strip terminated with a semi-elliptic stub and a modified ground plane to achieve wide bandwidth from 2.85-20 GHz. An exhaustive study of the radiation characteristics of this antenna in the frequency and time domains are presented. Design equations are derived and experimentally validated. Transient analysis indicates linear phase response and minimum dispersion to the transmitted pulse. The proposed radiator is omnidirectional with appreciable gain throughout the band.

The design and performance of a stepped slot printed monopole antenna in the ultrawideband is presented in this article. Mul- tiple resonances generated by the stepped slot geometry are matched in the ultrawideband using a modified microstrip feed. The impedance bandwidth (SWR 2) of the antenna is from 3 to 11 GHz. Radiation patterns are stable and omnidirectional with appreciable gain through- out the band. Performance of the antenna is also analyzed in the time domain, which reveals good pulse handling capabilities. Compact geom- etry of the antenna allows easy commercial deployment. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1126 -1129, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24262

Design of a compact dual frequency microstrip antenna is presented. The structure consists of a slotted circular patch with a dielectric superstrate. The superstrate,not only acts as a radome, but improves the bandwidth and lowers the resonant frequency also. The proposed design provides an overall size reduction of about 60% compared to an unslotted patch along with good efficiency,gain and bandwidth. The polarization planes at the two resonances are orthogonal and can be simultaneously excited using a coaxial feed. Parametric study of this configuration showed that the frequency ratio of the two resonances can be varied from 1.17 to 1.7 enabling its applications in the major wireless communication bands like AWS, DECT,PHS,Wi.Bro,ISM,and DMB. Design equations are also deduced for the proposed antenna and validated.

A dual wide-band CPW-fed modified Koch fractal printed slot antenna, suitable for WLAN and WiMAX operations, is proposed in this paper. Here, the operating frequency of a triangular slot antenna is lowered by the Koch iteration technique resulting in a compact antenna. Studies on the impedance and radiation characteristics of the proposed antenna indicate that a modified Koch fractal slot antenna has an impedance bandwidth from 2.38 to 3.95 GHz and 4.95-6.05 GHz covering 2.4/5.2/5.8 GHz WLAN bands and the 2.5/3.5/5.5 GHz WiMAX bands. The antenna exhibits omnidirectional radiation coverage with a gain better than 2.0 dBi in the entire operating band. Empirical relations are deduced and compared with the results.

A coplanar waveguide-fed planar elliptical monopole antenna suitable for use in ultra-wide band communication systems is presented. Antenna exhibits a wide impedance bandwidth from 2.64–10.9 GHz with an omni-directional radiation pattern. Further, a notched band centered at 5.45 GHz is obtained within the wide bandwidth by inserting a narrow horizontal slit inside the patch. The notched frequency can be easily tuned by varying the slit parameters. The slit provides significant reduction in gain in the notch band with little effect on the antenna operation at other frequencies. The time domain studies on the antenna shows a linear phase response throughout the band except at the notched frequency. The transient analysis of the antenna indicates very little pulse distortion confirming its suitability for pulsed systems.

In this paper, we present a detailed study of a printed square monopole antenna for Ultra Wide Band (UWB) communication applications. The 2:1 VSWR bandwidth of the proposed antenna is from 2.87–14 GHz. The antenna can be made to reject particular frequency bands by introducing narrow slits on the patch. In addition, the rejection band can be easily tuned for centre frequency, VSWR and rejection bandwidth by adjusting the slit parameters. In the proposed antenna, slits are introduced to reject the IEEE802.11a and HIPERLAN/2 bands used for WLAN applications. The antenna is analyzed in both frequency and time domains. Radiation patterns of the antenna are omnidirectional with appreciable gain throughout the band. Transient analysis indicates linear phase response and minimum pulse distortion.

A printed ultrawideband (UWB) monopole antenna with an overall size of 32x26mm2 with triple band-notches is presented in this paper. The antenna has an inverted T-shaped stub introduced in the monopole patch, two C-shaped parasitic strips and a pair of rectangular split-ring resonators close to the feed line and patch junction to introduce the desired frequency notches. The ground plane is beveled for wideband performance. The three band notches are 3.3-3.6 GHz, 5.05-5.90 GHz and 7.25-7.75 GHz for IEEE 802.16 (WiMAX) band, the wireless area network (WLAN) band and the downlink of X-band satellite communication systems respectively. The frequency band over which the antenna radiates is between 2.8 and 11.8GHz with a VSWR

In this work, we have presented a study of various antennas used in mobile phones in terms of their Specific Absorption Rates (SARs). Conventional antennas such as a half wavelength dipole antenna (0.835 GHz), rectangular patch antenna (0.8 GHz) and Planar Inverted F Antenna (PIFA) (0.8 GHz) are designed and simulated. In order to reduce their SAR values, Electromagnetic Band Gap (EBG) structure is placed near the dipole antenna. The various plots such as the S-parameter, radiation patterns and SAR values are generated to investigate results. The human head model with six layers having the appropriate material properties is designed to have a realistic approach in the detailed study on the SAR. All simulations are done in Ansys HFSS.

This paper presents a hybrid-log periodic dipole antenna (H-LPDA) which is a cost effective alternative to the regular planar-log periodic dipole antenna (PLPDA). In case of a PLPDA, required substrate dimensions increases with bandwidth as we have to accommodate dipoles of shortest dimensions to the longest. In order to make the antenna more cost effective in terms of the high frequency substrates used, a 3D structure is incorporated with the PLPDA while keeping the overall dimension as well as the performance same as the original PLPDA. In this paper, a PLPDA designed to operate over 700MHz - 4.5GHz is replaced by the proposed H-LPDA design. The design is simulated, fabricated and measured. The antenna is found to have performance similar to that of the original PLPDA antenna with good impedance matching (VSWR

A novel, compact suspended semicircular patch with a half U-slot antenna is proposed for dual frequency operation. Parametric study of this new configuration is carried out by varying length and width of the slot and the coaxial feed probe radius and its position. The dual frequency ratio from about 1.18 to 1.66 has been achieved by varying the slot parameters, position, and radius of feed probe. Experiments have been carried out with good agreement with simulated results. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2021–2024, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21844

Design of a dual-port circular patch antenna with a sector-slot for dual-frequency operation is presented. The antenna resonates at two distinct frequencies with orthogonal polarizations and broad radiation characteristics. Unlike the conventional circular patch, this antenna can be microstrip-fed to operate at either of the resonances. The two polarizations can be simultaneously excited using two electromagnetically coupled ports with an isolation better than −30 dB between the ports. This antenna has the added advantage of size reduction of 44% compared to the conventional circular patch without any reduction in gain. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 505–508, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21393

A compact asymmetric coplanar strip (ACS) fed dual-band antenna suitable for DCS/WLAN applications is presented. Dual-band operation is achieved by modifying the signal strip of the ACS monopole. Parametric studies indicate that operating frequencies of the antenna are determined by the dimensions of the strip monopole. Measurements on the optimized antenna printed on an FR4 substrate with er = 4.4 and height = 1.6 mm indicate good radiation characteristics with moderate gain. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1087–1089, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26731

In this paper, a novel compact micro strip antenna, designed on FR4 substrate, is proposed. Here, a compact square patch antenna is designed in such a way that the radiating patch is loaded by a layer of metal between the patch and the ground which makes the antenna operate at a lower frequency. The antenna design is optimized to obtain a resonant frequency of 2.45GHz. Miniaturization of the antenna is obtained by using meta-material based structures inscribed on the metal layer. The meta-material structure used here is a square-shaped complementary split ring resonator (CSRR). On varying the number and size of inclusions, high levels of miniaturization are observed.

A compact band-notched CPW fed Ultra Wideband (UWB) antenna for portable UWB applications is proposed. The antenna is designed with the intention of reducing the dimensions of the radiating element without deteriorating its performance over the UWB range so that it can be incorporated within the physical limit specification of the USB plug footprint of Type-A. Also an electronically switchable quarter-wavelength notch filter designed for IEEE 802.11a has been incorporated into the system to avoid interference with existing WLAN communication. The antenna, fabricated on FR4 substrate (er=4.4, thickness=1.6mm) with a compact physical dimension of 9×30mm2, offers a good impedance bandwidth from 3.0 to 11.4GHz. The radiation patterns were found to be omnidirectional. The gain and efficiency of the antenna are also reported. The antenna was looked upon for its behavior at the notch frequency (5.45GHz) which showed a good VSWR >>2 affirming excellent filtering of the WLAN band starting from 5.1-5.8GHz.

A millimeter wave antenna using Half Mode Substrate Integrated Waveguide (HMSIW) is presented. Narrow rectangular patch is used as radiating element fed by the open end of the HMSIW. Simulation results are presented for antenna array designed on Alumina substrate for 24GHz and 60GHz band.

A compact coplanar waveguide-fed (CPW) printed inverted cone antenna suitable for Ultra Wide Band (UWB) wireless systems is proposed. The antenna design consists of an inverted cone as the radiating patch and a tapered ground plane with a U-shaped slot near the feed. It has a compact dimension of 30×14mm2 printed on a substrate of permittivity 4.4 and operates over a wide impedance bandwidth from 2.9GHz–11GHz for VSWR 2∶1. The radiation patterns are stable, omnidirectional with an average gain of 2dBi. The measured transfer functions at different antenna orientations shows that the proposed antenna possess excellent transient characteristics. The pulse preserving properties of the antenna is also studied and the measured results indicate excellent pulse fidelity.

The design and testing of a planar semi-elliptic monopole slot antenna to operate in the 3.1-10.6 GHz ultra wide band (UWB) is proposed in this paper. The coplanar fed antenna has a 2:1 VSWR bandwidth from 2.85-20 GHz in which the 5.15-5.825 GHz IEEE802.11a and HIPERLAN/2 band is notched. Empirical relations connecting the resonances and the geometric parameters of the antenna are deduced and experimentally verified. Radiation patterns of the antenna are omni directional and there is appreciable gain throughout the band except at the notch. The antenna features excellent transient characteristics.

A CPW-fed planar monopole antenna for triple band operation is presented. The antenna consists of an elliptical radiating patch with a curved ground plane with embedded slots. When two narrow slots are introduced on a wideband elliptical monopole antenna (2.2-7 GHz), two bands are rejected without affecting the antenna properties at the rest of the operating frequencies. By properly choosing the length and location of the slots, a triple band antenna design is achieved. Impedance and radiation characteristics of the antenna are studied and results indicate that it is suitable for the 2.5-2.69 GHz, 3.4-3.69 GHz, and 5.25-5.85 GHz WiMAX applications and also the 2.4-2.484 GHz, 5.15-5.35 GHz, and 5.725-5.825 GHz WLAN applications. The antenna exhibits omnidirectional radiation coverage with its gain significantly reduced at the notched frequency bands.