This paper presents a low insertion loss low-pass filter based on the spoof surface plasmon polariton (SSPP) with single comb-shape. Compared with traditional ones, the proposed filter provides lower insertion loss and return loss by optimizing the structural parameters of the mode conversion and SSPP parts. According to the measurement results, the average insertion loss of the fabricated filter is 0.41 dB and the return loss of which at the near-zero-hertz band is <−25.9 dB. The S parameter comparison result between the unoptimized and optimized filters demonstrates that the optimized filter provides lower insertion loss and return loss, smaller size, and better out-of-band rejection. The dispersion comparison result reveals the reasons behind the improved performances. The better performances of the optimized filter proves that breaking the regularity of traditional SSPP filters is beneficial to the filter's performances.

A four-element wide-band octagonal ring-shaped antenna is proposed for human interface device and S-band applications. The isolation structure comprises a parasitic element and a T-shaped structure. The antenna has −10 dB impedance bandwidth 63% (2.1–4.0 GHz) with miniaturized dimension of 54.98 mm × 76 mm. The multiple input multiple output (MIMO) antenna gain is 2.83 dBi at the 2.4 GHz resonant frequency. The designed MIMO has envelop correlation coefficient of 0.026 in the 2:1 VSWR band. The −10 dB total active reflection coefficient bandwidth of 1.2 GHz has been achieved in the entire frequency band, and has MEG value of ≤−3 dB. The specific absorption rate has found below the safety limit near the human head, palm and wrist.

A planar inverted F-Antenna with the dual band-dual polarization property is presented for medical body area networks applications. The designed antenna covers the 2.45 GHz industrial, scientific and medical, 4 G long term evolution (2.5–2.69 GHz) bands for ON body communication and Wi-Fi and WLAN (3.5–3.6 GHz) bands for OFF body communication. At the lower band, an equivalent offset fed magnetic microstrip type dipole has been utilized that generate field parallel to the surface of the body for supporting ON body communication. The broadside radiation pattern has been realized using the slotted patch counterpart for supporting OFF body communication. This technique has resulted in a design of dual band dual mode property using a single radiator. The footprint of the antenna is only 0.35λg × 0.17λg × 0.08λg. Owing to its compactness, lightweight, and easy mountable property (due to foam substrate), the proposed antenna is found to be robust for MBAN applications. The maximum permissible transmitted power for the 1st band is 25.78 and 20.3 dBm for the 2nd one to maintain standard specific absorption rate limitations of 1.6 W/Kg. Experimental investigations over human body showed minimal deviations from the free space conditions which makes it a potential candidate for body-centric communications.

This Paper reveals a novel single layer five band frequency selective surface (FSS). Novelties of the proposed FSS lie in its five closely spaced stop bands at 2.4, 3.38, 4.82, 6.32, and 7.75 GHz as well as the reduced single layer structural thickness (0.0016 λ0) and the miniaturized unit cell size (0.0656 λ0) at lower resonant frequency as compared to the existing multiband FSS. The unit cell structure consists of six octagonal concentric interconnected loops. Adjacent loop interconnection technique reduces the cell size by more than 44%. Furthermore, arrow-shaped rings are also introduced on each corner of the outermost octagonal loop, and using this technique approximate 23% cell miniaturization can be achieved. In addition, the proposed FSS exhibits excellent angular stability.

In this paper, a novel decoupling technique for closely spaced E-plane patch antennas using defect ground structure (DGS) is proposed. The electric field coupling between the antennas is suppressed by etching DGS which consists of a pair of rectangular slots and four stubs on the ground plane. Moreover, unlike the other methods, the DGS is not etched in the middle of the antennas but loaded along the outer edge of the radiated patch. Thus, through the adopted technology the distance between the antenna elements is reduced and the isolation is increased. To validate the improvements by adopting the proposed technology, the array with DGS loading has been fabricated and then measured. The measurement results show that designed antennas have 95 MHz 10-dB impedance bandwidth, which is 25 MHz higher than that of the antenna without DGS. More importantly, isolation improvements have been increased from 8.5 to 31.3 dB by using the decoupling technique when the antennas are placed with a 0.032 λ0 edge-to-edge distance, where λ0 is the free-space wavelength. Therefore, this technique can be widely applied to improve isolation in a compact and low profile antenna system.

This paper presents the design of an elliptical shape ultra-wide band antenna for imaging of wood. The antenna is constructed comprising an elliptical shape of patch loaded by a stub to resonate at lower bands, strip loading at the back, and chamfered ground. Despite having miniaturized dimensions of 20 mm × 20 mm, the proposed antenna shows better results compared to recent studies. The simulation results depict a good ultra-wide bandwidth from 2.68 to 16 GHz, and 18.2–20 GHz. Besides, the proposed antenna has two low-frequency bands at 0.89–0.92 and 1.52–1.62 GHz, maximum gain of 5.48 dB, and maximum directivity of 6.9 dBi. The measurement outcomes are performed in air, plywood, and high-density wood and show a good agreement with the simulated results done using electromagnetic simulator CST. In addition to that, the measurement results of S-parameters, transmitted and received signals show a good agreement with the simulated results. Besides, the measured results illustrate a good isolation and uniform illumination among arrays as well as the received signals' shapes do not change in different environments, but only the amplitude. Hence, the proposed antenna seems to be adequate for microwave imaging of wood.

The next generation mobile communication systems impose challenging performance, size, and cost requirements on the power amplifiers (PAs). This paper presents novel DC-biasing circuits, which are compact and yet can control the harmonics almost arbitrarily. The proposed circuit consists of a composite right-/left-handed (CRLH) transmission line (TL) stub, of which the size and harmonics-control function can be tuned by modifying the dispersion diagram of the stub line. As a proof of concept, a compact 2-GHz 7-W GaN HEMT class-F PA using the versatile CRLH-TL stubs was fabricated, demonstrating 85.8% drain efficiency and 77.3% power-added efficiency.

This paper presents a compact microstrip antenna using FR-4 substrate for dual band circularly polarized operation using a modified square ring slot in the ground plane with microstrip line feed. Simulation of the impedance characteristic and radiation characteristic for the proposed antenna is carried out using commercially available HFSS software. The simulated data validate measured results and shows good agreement. Proposed antenna shows an impedance bandwidth (return loss >10 dB) of 50.88% at 5.9 GHz of center frequency and 29.92% at 12.8 GHz of center frequency for lower and upper band, respectively. The 3 dB axial ratio bandwidth for lower and upper band is 26.4 and 3.0%, respectively and measured peak gain for the lower and upper band is found as 3.2 and 3.4 dBic, respectively. The proposed antenna can be suitable for wireless communication in C and Ku bands.

The pulse radiating characteristic of a wrapped bow-tie antenna (WBA) and wrapped resistively loaded bow-tie antenna (WRLBA) is presented for impulse radar applications in this paper. The numerical analysis of the WRLBA is performed by comparing that of the WBA. The wrapped antennas are realized on a flexible substrate. The antennas are fed by an impedance tapered balun, which has an overall transmission loss of −1.4 dB over the balun length. The characteristics of the resistive loading to the wrapped antenna, such as reflection coefficient, reflected pulse in the time domain, voltage standing wave ratio, and input impedance, are experimentally investigated and compared with simulated results. The fidelity factor of the radiated electric field on the boresight direction for the WBA and WRLBA is calculated as 0.82 and 0.96, respectively. The wireless communication ability is evaluated by the transmission coefficient, group delay, boresight gain, and received waveform. The calculated fidelity factor of the received waveform for the WBA and WRLBA is 0.79 and 0.85, respectively. The average and variations of the group delay of both wrapped antennas are observed to be around 2.5 ns and less than 1.5 ns, respectively.

This paper describes a method to analyze open or closed elliptical structures with constant axial ratio by a Body-of-Revolution (BoR) Finite Element Method (FEM). The method is based on Transformation Optics, a coordinate transformation that maps the elliptical shape to a circular shape, for which BoR-FEM represents a greatly efficient tool for the analysis.

A novel low profile dual band patch antenna is presented. It consists of a composite right/left-handed transmission line (CRLH TL) unit cell gap coupled with the radiating edge of a rectangular patch antenna. The dual band behavior is achieved by coupling the zeroth order resonance mode of CRLH TL and TM10 mode of the patch antenna. It is shown that frequency ratio can be changed by varying the gap between the patch and CRLH TL unit cell. The proposed configuration enables frequency reconfigurability by changing the CRLH TL unit cell using a switch. A prototype of the antenna having frequency ratio f2/f1 = 1.08 is designed and fabricated. The proposed antenna shows measured S11 ≤ −10 dB bandwidth of 100 and 50 MHz at resonance frequencies of f1 = 4.84 and f2 = 5.22 GHz, respectively. A 2 × 2 dual band CRLH TL coupled patch array is also presented, showing more than 12.7 dBi gain at both resonance frequencies.

A compact low-pass filter (LPF) with wide rejection band based on T-type circuit of an enhanced dual composite right-/left-handed (D-CRLH) resonator is presented in this paper. The resonator has only one cell with series and parallel tank circuit. The parallel LC tank circuit has been realized by an interdigital capacitor and one shorted finger, whereas its series LC tank circuit is realized by an air gap capacitance and a short circuit stub. The filter has wide rejection band bandwidth with three transmission zeros (TZs). The filter bandwidth and TZs frequencies are controlled by the D-CRLH element values. The results of the proposed filter demonstrate minimum insertion loss in passband, high roll-off rate, and good figure of merit. The measured results are in good agreement with the simulated results. The detailed filter design is discussed in terms of circuit modeling, dispersion analysis, and full-wave simulation. Finally, the filter size is compact (0.10 λg × 0.15 λg) at cut-off frequency.

A 6–18 GHz high-power amplifier (HPA) design in GaN on SiC technology is presented. This power amplifier consists of a two-stage corporate amplifier with two and four transistors, respectively. It has been fabricated on UMS using their 0.25 µm gate length process, GH25. A study of the suitable attachment method and measurement on wafer and on jig are detailed. This HPA exhibits an averaged output power of 39.2 dBm with a mean gain of 11 dB in saturation and a 24.5% maximum power added efficiency in pulse mode operation with a duty cycle of 10% with a 25 µs pulse width.

This paper presents a novel artificial magnetic conductor (AMC) loaded dipole above FR4 substrate. The proposed AMC consists of two metal layers that shield the wave from the lossy substrate leading to a significant increase in the dipole efficiency over a wide bandwidth. The dipole is fed through vias that are connected to a wideband balun placed on the opposite side of the ground plane. The proposed assembly is fabricated and characterized. Measurements, which are in a very good agreement with the electromagnetic simulations, show that the operating fractional bandwidth achieves the value of 16.2%, 1.927–2.267 GHz, with peak radiation efficiency of 72.5%.

In this article, a multiband antenna for various wireless communications is proposed for WWAN, Bluetooth, WiMAX, WLAN, and Downlink satellite system. The antenna consists of a radiating patch and a rectangular ground plane with four L-shaped stubs which are embedded as side arms to obtain a resonating band for WWAN (1.9GHz), Bluetooth (2.4 GHz), WiMAX (2.5, 3.5, and 5.5 GHz), and WLAN (5.5 GHz) wireless systems and a C-shaped stub is etched on the radiating patch to obtain a higher WLAN band (2.4, 5.2, and 5.8 GHz) and a satellite downlink system (7.5 GHz). The proposed antenna exhibits circular polarization at WWAN band and linear polarization for remaining applications. Also, the proposed antenna exhibits an omnidirectional radiation pattern.

A bottom-feed omni-directional CP (circularly polarized) antenna array is proposed in this letter. The antenna array is composed of four elements (two printed ZPS (zero-phase-shift) line loops and two half-wavelength dipoles). The four elements are fed with the same phase and amplitude. The ZPS line loops provide the horizontal polarization while the dipoles provide the vertical polarization. Therefore, omni-directional circular polarization is formed in the far field. The feeding network consists of a 1–4 T-shaped power divider formed by parallel strip lines. In order to balance the amplitude of the feeding coaxial cable, the structure is used in the bottom to transfer parallel strip line to micro-strip line. Besides, the loops and the dipoles are placed on the different side of the network to guarantee the omni-directional radiation property. The measured impedance bandwidth of the fabricated antenna is 0.13 GHz (2.40–2.53 GHz) and the measured maximum CP gain at 2.45 GHz is 4.8 dBic.

A dual-polarized dual-layer wideband microstrip antenna is presented. Dual orthogonal linear polarization and enhanced isolation between two ports are achieved by employing two radiating patches perpendicular to each other and printed on two separate substrates. Broadband behavior of the antenna is realized by using two wideband double-sided printed strip dipole and angular ring as radiating patches along with wideband baluns as feeding system. The patches are connected to baluns with two separate twin-lead transmission lines. Moreover, to improve the impedance bandwidth of the strip dipole significantly, a diamond-shape parasitic patch is artily incorporated into the top side of the upper layer of the antenna. The proposed antenna can easily be employed in large-scale arrays thanks to the feeding system of the patches. A prototype is fabricated to verify the simulation results where the measurement results show the −10 dB impedance bandwidths of 40% (4.3–6.5 GHz) and 43% (4.2–6.5 GHz) at port #1 and port #2, respectively. Besides, the isolation between two ports and the radiation gain are obtained around 35 dB and 9 dBi, respectively, which are useful for WLAN applications.

In this paper, a flexible CPW fed ultrawide band (UWB) antenna with mu-negative (MNG) metamaterial is designed, fabricated, and tested for wearable applications. Initially, a UWB antenna of size 50 mm × 43 mm is fabricated on two different substrates, viz. flexible FR4 and semi-flexible Rogers RT/duroid 5880. A metamaterial structure fabricated on flexible FR4 shows a magnetic resonance from 7.2 GHz to 9.2 GHz with maximum stop band attenuation (−49 dB) and high MNG value (−2121.6) at 7.87 GHz. Then a (3 × 3) array of designed MNG metasurface is used as ground plane with flexible UWB antenna, which improves its overall gain and radiation pattern. The performance of the flexible antenna with/without metamaterial at various distances from flat and cylindrical three-layered human phantom of skin, fat, and muscle is studied. Further, the bending characteristics at different angles and performance over thin metallic sheet is also evaluated. Additionally, the peak specific absorption rate value averaged over 1 g of tissue at three chosen frequencies from UWB range (3, 5, 10 GHz) with/without metamaterial using 0.3 and 0.1 W of input power is also analyzed. The simulated and measured results are in good agreement which confirms that the designed antenna is a good candidate for wearable applications.

In this article, the material distributive topology-based design optimization of ultra-wide band (UWB) antenna is proposed by using improved binary particle swarm optimization (BPSO) with finite difference time domain (FDTD) method. In the improved BPSO implementation, the velocity of each particle is calculated based on complete set of bits of particle position vector. The V-shaped transfer function is employed to transform all real values of velocities to values in the interval [0,1]. The fitness function of all the particles in BPSO algorithm are computed parallely by using FDTD simulation. The usage of FDTD and the parallel computation helps in analyzing the broadband frequency characteristics of the antenna with a single simulation run. The return loss of the optimized UWB antenna obtained from FDTD, Computer Simulation Technology (CST) simulation and practical measurement are in good agreement and show good impedance matching.

This paper proposes a microstrip antenna with reduced in-band and out-of-band radar cross-section (RCS) by subtracting the area of weak scattered current on the ground plane. Fourteen square slots were subtracted from the ground plane, reducing in-band and out-of-band RCS while maintaining radiation performance. Modified and reference antenna surface current distributions were simulated and analyzed in radiating and scattering modes. Two antenna prototypes were fabricated and measured to verify the simulation. The proposed antenna RCS was reduced compared with the reference antenna in the frequency range 1–4.4 GHz, including in-band and out-of-band frequency bands. Maximum in-band and out-of-band RCS reduction was 16.3 dBsm at the working frequency, and 19.3 dBsm at 3.4 GHz, respectively