This paper presents different reconfigurable antennas with frequency, polarization, and pattern diversities. All the antennas have a very simple, novel, and compact structures, which are used for different wireless communication applications. These antennas employ switching for obtaining different reconfigurations. At first, an E-shaped antenna is designed for multi-band frequency reconfigurability. Second, circular and rectangular-shaped patch antennas are designed for achieving diversity in polarization. At last, a pattern reconfigurable antenna is designed with multiport excitation. These antenna performances are analyzed using various parameters such as return loss, radiation pattern, voltage standing wave ratio (VSWR), and gain. The prototypes of the antennas are fabricated and measured results along with simulated ones are presented. Both the results are in good agreement.

This paper presents a new optically controlled reconfigurable ultra-wideband antenna using reconfigurable optical router with photonic crystal substrate. The proposed antenna has three optical switches. The optical switches are made by placing silicon wafers over three slots etched on the resonator. The coplanar fed microstrip antenna can work at eight modes using optically controlled switches. This design proposes triple narrow notched bands at center frequencies 3.5 GHz “WiMAX”, 5.5 GHz “WLAN” and 8.4 GHz “X-band satellite communication”. The proposed antenna satisfies the voltage standing wave ratio requirement of <2 in the frequency band between 2.6 and 11.8 GHz except for the three rejected bands. According to the incident light, the physical properties of these switches can be changed from an insulator state (OFF state) to a near-conducting state (ON state). The incident light is coupled to the optical switches using a reconfigurable optical router. The proposed antenna provides high gain, and high efficiency all over the frequency band excluding the rejected bands.

Wideband dipole antennas are proposed using the multi-mode resonance concept. By symmetrically introducing one-pair or two-pair of stubs at the nulls of current distribution of the second odd-order mode, two radiation modes are excited in a single, center-fed dipole resonator. Using these stubs, the second odd-order mode gradually moves down to its first counterpart, resulting to achieve a wideband radiation with two resonances. Prototype antennas are then fabricated to experimentally validate the design approach. Compared with a reference dipole with a bandwidth of 17%, the proposed dipole's bandwidth can be effectively increased to 49.7%.

This paper proposes a unique, first of its kind fabrication technique for the making of textile antennas. A novel method that provides scope for automation in textile antenna production is presented here. A completely integrated textile antenna fabrication method that eliminates the tasks of positioning and fastening of the various components of a patch antenna is discussed. The technique employs multilayer weaving for the production of a wearable antenna on a cotton substrate. Silver yarn is used for the conductive regions of the textile antenna. Two layers of woven cotton serve to isolate the radiating patch from the ground plane of the antenna. The designed antenna was chosen to operate at the frequency of 2.45 GHz for Wireless Local Area Network. The built prototype resonated at 2.43 GHz with a |S11|of −18.62 dB. The integrated textile antenna exhibited a gain of 1.06 dBi at 2.43 GHz.

In this paper, a microstrip diplexer composed of two similar resonators is designed. The proposed resonator is consisting of four microstrip cells, which are connected to a coupled lines structure. In order to select a suitable geometric structure, first, all cells are assumed as undefined structures where there is a lack of basic information about their geometry and dimensions. Then, an equivalent LC circuit of the coupled lines is introduced and analyzed to estimate the general structure of the resonator respect to a requested resonance frequency. The proposed diplexer is designed to operate at 2.36 and 4 GHz for wireless applications. The insertion losses (S21 and S31) are decreased significantly at the resonance frequencies, so that they are 0.2 and 0.4 dB at 2.36 and 4 GHz, respectively. The designed diplexer is fabricated and measured and the measurement results are in a good agreement with the simulations.

In this paper, a compact tri-band asymmetric coplanar strip (ACS)-fed meander-line antenna for wireless communications is proposed. Two inverted-L-shaped resonators are added to a simple meandered radiator for standard tri-band operation. Parametric studies indicate that operating frequencies of the proposed antenna are determined by the dimensions of the two inverted-L-shaped resonators. The measured results show that the proposed antenna can achieve three frequency bands; i.e. 1.48–1.63, 2.25–2.48, and 4.22–6.0 GHz. These bands can successfully cover the global positioning system L1, wireless local area network (WLAN), and HIPERLAN/2 operation bands, respectively. The proposed antenna exhibits good radiation patterns with reasonable gain and high radiation efficiency across the operating bands. In addition, the proposed antenna has compact size and simple feeding scheme, which make it suitable to be integrated within the portable device for wireless communications.

In this paper, we propose an effective waveform diversity scheme that can be applicable to synthetic aperture radar (SAR) operations affected by interfering signals. A novel approach is taken to achieve fully adaptive SAR waveform diversity that generates sufficient number of orthogonal signals with modest performance trade-off. To this purpose, multiple phased-code waveforms are arbitrarily generated with mutually low cross-correlations. They exhibit a highly flexible characteristic as their code lengths are not limited and Doppler tolerance is well preserved throughout SAR imaging. Various SAR jamming simulations are carried out to demonstrate that the proposed waveform diversity has a good potential for electronic counter-countermeasures applications.

In this paper, a miniaturized coaxial feed curved-slotted microstrip patch antenna over a fractalized uniplanar compact electromagnetic bandgap (F-UC-EBG) ground plane is proposed and investigated. Compact size is achieved by cutting the curved slots along the orthogonal directions of the patch radiator. The curved-slotted microstrip patch antenna is 38.30% miniaturized as compared with the conventional microstrip patch antenna resonating at 2.38 GHz. Furthermore, the ordinary ground plane of the curved slotted patch antenna is replaced by the F-UC-EBG ground plane. Due to the slow wave phenomenon created in the F-UC-EBG structure and the better impedance matching at the lower frequency further miniaturization and improved performance are obtained. The proposed antenna shows 74.76% miniaturization as compared with the conventional microstrip patch antenna resonating at 1.57 GHz and has 2.61% 10-dB fractional bandwidth, 1.49 dB gain, and 81.59% radiation efficiency. The proposed antenna is fabricated on a low-cost FR4 substrate having an overall volume of 0.184λ0 × 0.184λ0 × 0.0236λ0 at 1.57 GHz GPS band. The measured and simulated results are in good agreement and predicting appropriateness of the antenna in portable and handheld communication systems for GPS applications.

This paper presents application of split ring resonators (SRR) in conventional waveguide slot array antenna to achieve performance improvement and multiband characteristics. Three SRRs have been placed on the transverse plane of a conventional slotted waveguide and has been simulated and measured. The measured results show that the antenna has dual band response with respective 10 dB return loss bandwidth 8.23–9.23 GHz (11.45%) and 9.68–11.01 GHz (12.87%). The measured gain and radiation pattern reveal that the proposed antenna has higher gain and front to back radiation ratio as compared with a conventional slotted waveguide antenna. Equivalent circuit of the proposed antenna also has been presented.

This paper presents the behavior of three iterations of a coplanar waveguide fed CANTOR Set fractal antenna. This kind of antennas allows having a broadband behavior and important gains. Also, the setup of slots allows having more lower resonant frequencies and therefore designing miniaturized antennas with good performances. The proposed antennas are suitable for 2.5/3.3/5/5.5 GHz worldwide interoperability for microwave access and for 2.4–2.5/4.9–5.9 GHz wireless local area networks applications. The simulations were performed in FEKO 6.3. The measurements were performed with Vector Network Analyzer HP 8719C.

An analysis about the effects of various bi-isotropic (BI) coatings and BI background media upon the gain characteristics of an axially slotted cylinder using numerical simulations is presented. It is investigated that chirality and Tellegen parameters of a coating and a background medium play a significant role in modifying the gain properties. It is further studied that an axially slotted cylinder when coated with a strong BI material and embedded in a free space background significantly enhances the gain in the forward direction. On the other hand, a strong Tellegen coating guides most of the radiated field from an axial slot toward rear side of the cylinder.

A new class of 3-dB impedance transforming directional couplers has been proposed in which the recently published coupled-line couplers, consisting of coupled-line sections having different electrical lengths, have been utilized. The main advantage of the proposed directional couplers is the possibility of obtaining high impedance transformation ratio, thus the known limiting condition of realizable impedance transformation in 3-dB couplers is overcome. Moreover, the proposed directional couplers feature significantly wider operational bandwidths. The theoretical analysis of the proposed impedance-transforming directional couplers has been shown and is fully supported by the measurements of the manufactured model operating in 0.5–1.5 GHz frequency range.

This paper proposes a planar monopole antenna with a parabolic edge shape. This antenna, which has notch characteristics in the wireless local area network (WLAN) band, can be miniaturized. To obtain the notch characteristics in the WLAN band, a slot with a parabolic edge shape identical to that of the monopole structure was implemented. Because the planar monopole antenna with a parabolic edge shape possesses characteristics similar to those in self-complementary structure conditions, it can be miniaturized by reducing the antenna components at the same proportion. For the antenna fabrication, an FR4 dielectric substrate with a dielectric constant of 4.7 was used. The size of the miniaturized antenna that satisfies the ultra-wide band requirement was 15.6 × 18.6 mm2, and the 10-dB band was 3.013–12.515 GHz. At each frequency, the radiation pattern was similar to that of a dipole antenna.

A microstrip transmission line fed fork-shaped planar antenna is proposed for Bluetooth, WLAN, and WiMAX applications. The antenna made of a microstrip feed line, fork-shape patch on one side and defected ground plane on the other side of dielectric substrate. A fork-shape is formed by two side circular arms and a rectangular central arm. The inverted T-shaped ground plane with a rectangular slot in the center arm is used to increase the bandwidth with better impedance matching of the lower band. The antenna is practically fabricated to validate the design. The antenna resonate dual band to cover an entire the WLAN and WiMAX bands. The antenna shows the measured bandwidth of 410 MHz (2.26–2.67) and 3.78 GHz (3.0–6.78 GHz) at lower and upper bands, respectively.

This paper presents the design, testing, and analysis of a clover structured monopole antenna for super wideband applications. The proposed antenna has a wide impedance bandwidth (−10 dB bandwidth) from 1.9 GHz to frequency over 30 GHz. The clover shaped antenna with a compact size of 50 mm × 45 mm is designed and fabricated on an FR4 substrate with a thickness of 1.6 mm. Parametric study has been performed by varying the parameters of the clover to obtain an optimum wide band characteristics. Furthermore, the prototype introduces a method of achieving super wide bandwidth by deploying fusion of elliptical patch geometries (clover shaped) with a semi elliptical ground plane, loaded with a V-cut at the ground. The proposed antenna has a 14 dB bandwidth from 5.9 to 13.1 GHz, which is suitable for ultra wideband (UWB) outdoor propagation. The prototype is experimentally validated for frequencies within and greater than UWB. Transfer function, impulse response, and group delay has been plotted in order to address the time domain characteristics of the proposed antenna with fidelity factor values. The possible applications cover wireless local area network, C-band, Ku-band, K-band operations, Worldwide Interoperability for Microwave Access, and Wireless USB.

A coplanar waveguide (CPW)-fed circular-shaped fractal antenna with third iterative orthogonal elliptical slot for ultra-wideband applications is presented. The bandwidth is enhanced by using successive iterations of radiating patch, CPW feedline, and tapered ground plane. An impedance bandwidth of 2.9–20.6 GHz is achieved. The designed antenna has omnidirectional radiation patterns along with average peak realized gain of 3.5 dB over the entire frequency range of operation. A good agreement is observed between the simulated and experimental results. This antenna structure has the advantages of miniaturized size and wide bandwidth in comparison to previously reported fractal structures.

The design of an analog frontend including a receiver amplifier (RX) and laser diode driver (LDD) for optical communication system is described. The RX consists of a transimpedance amplifier, a limiting amplifier, and an output buffer (BUF). An offset compensation and common-mode control circuit is designed using switched-capacitor technique to save chip area, provides continuous reduction of the offset in the RX. Active-peaking methods are used to enhance the bandwidth and gain. The very low gate-oxide breakdown voltage of transistors in deep sub-micron technologies is overcome in the LDD by implementing a topology which has the amplifier placed in a floating well. It comprises a level shifter, a pre-amplifier, and the driver stage. The single-chip frontend, fabricated in a 28 nm bulk-digital complementary metal–oxide–semiconductor (CMOS) process has a total active area of 0.003 mm2, is among the smallest optical frontends. Without the BUF, which consumes 8 mW from a separate supply, the RX power consumption is 21 mW, while the LDD consumes 32 mW. Small-signal gain and bandwidth are measured. A photo diode and laser diode are bonded to the chip on a test-printed circuit board. Electro-optical measurements show an error-free detection with a bit error rate of 10−12 at 20 Gbit/s of the RX at and a 25 Gbit/s transmission of the LDD.