Simple internal multiband monopole antenna with low specific absorption rate (SAR) for most wireless communication applications is presented in this paper. The proposed antenna is an unequal arms monopole antenna with a meander stripoin the other substrate side. The antenna has a simple structure and it is sufficiently small in size to be easily fitted on the housing of a mobile phone or a universal serial bus (USB) dongle with size 20 × 50 × 0.8 mm3. The antenna is designed to operate in different bands to cover most of allocated wireless communication bands in the frequency range from 0.9 to 6 GHz. The proposed antenna has an acceptable average gain of about 2.75 dBi and an average efficiency of about 85% while providing a monopole radiation pattern in both horizontal and elevation planes, with average half-power beam width of 65° in the elevation plane. The simulation and the experimental results of the antenna are in agreement. The SAR in the human head is investigated by using CST 2012 Microwave Studio Hugo Voxel Model.

A wideband antipodal Vivaldi antenna has been designed and optimized. A slight improvement is obtained by employing multiple metalense based on circular split-ring resonators to maximize the antenna gain with the maximum bandwidth. The designed antennas have been fabricated and characterized, showing good agreement with simulations. The maximum measured gain is $G = 12\;{\textrm{dB}}$, and the −10 dB bandwidth is from $f = 3\;{\textrm{GHz}}$ to $f = 13\;{\textrm{GHz}}$.

This paper proposes planar antennas with quadri-polarization diversity using a pair of orthogonal linear polarizations and a pair of orthogonal circular polarizations (CP). A novel feeding network with four input ports and four output ports is presented, allowing antenna polarization diversity by selecting different input ports, which can generate right-handed CP, left-handed CP, horizontal linear polarization, and vertical linear polarization. The first design uses two square patch resonators to synthesize the four polarizations; the second design comprises four circularly polarized patches to synthesize the four polarizations with an improved axial-ratio (the ratio of orthogonal components of an E-field) bandwidth. The proposed designs do not require for embedding PIN diodes and DC-biasing circuits, making them suitable for use in higher-frequency applications where using lump elements would be difficult. The novel antennas provide potential polarization diversity features which can be used for many applications. Details of the antenna design are shown, and the measurement and simulation results are also provided to validate the proposed concept.

Specifications of the substrates are among the most important and problematic parameters that still do not have proper models in the design procedures of metasurfaces. In this paper, a new fast and exact algorithm based on artificial neural networks (ANNs) is presented, which makes it possible to design frequency-selective surfaces (FSSs) on various kinds of standard substrates. Also for the first time, designing FSSs on uniaxial anisotropic substrates can be easily done in short time and without any optimization algorithms. During this paper, first equivalent geometry approach (EGA) is demonstrated as a new method of preparation the ANNs. Then EGA is used to train geometry transformation ANNs. The advantage of this approach is to reduce the size of training datasets by about 98% and prevent from superfluous simulations. Hence, the time needed for training of the networks is much less than before. Numerical results are used to show that the required time for developing FSSs is <200 ms on average, and errors are <2%. For the final validation, a prototype sample of FSS is fabricated on the RO4003 substrate with 20 mil thickness. Both analytical and experimental results confirm the correctness of the predicted values.

This study presents a simple switched-band impedance transformer using microstrip lines. The proposed circuit is suitable for loads with frequency-dependent complex impedances at two arbitrary operating frequencies. The transformer comprises two cascaded microstrip lines and two detachable shunt stepped-impedance stubs, which are separately connected to the main line via switching diodes such that provide good matching at one of the two operating frequencies and suppress unwanted signal at the other frequencies. The structure contains several user-set parameters such that designers can create a smaller circuit. The circuit parameters, except the user-set ones, are obtained using the derived design formula. The numerical simulations and experimental results agree well such that validate the proposed structure and the design formula.

In this paper, the design and test of a single-chip RF pulse-width modulator and driver (PWMD) aimed at exciting a high-power class-E GaN high-power stage at 435 MHz is described. For the required buffer size, avoiding potential ringing of the pulses within the buffer structure presents a major challenge in the design process. Therefore, a smaller test chip capable of driving capacitive loads of up to 5 pF was initially designed, fabricated, and tested. An approach based on three-dimensional electromagnetic simulations was used to validate the test results and offers excellent simulation accuracy. Based on the results obtained for test chip an enlarged PWMD chip capable of driving a 40 W high-power stage has been designed and tested on passive loads representing the targeted final stage.

In this paper, a small ultra-wideband (UWB) antenna with two stop bands by a compact electromagnetic bandgap (EBG) cell loaded with two new open meander slots is presented. With the coupling of the EBG cell to the feedline, the stop bands are formed. The designed EBG cell is a mushroom type that has the advantages of being able to independently control the stop bands, high responsiveness selectivity of stop bands, easy switching, the need for fewer EBG cells, and low impact on the working characteristics of the antenna. To have a better understanding of the proposed EBG mechanism, characteristic mode analysis is used. The size reduction of the suggested antenna is obtained by halving the reference antenna relative to the axis of symmetry. The measurement results for −10 dB adaptation are from 2.73 to 13 GHz with stop bands at 3.51 GHz (12.9%) and 5.34 GHz (14.1%). The radiation behavior of the minimized antenna is similar to that of a reference antenna. Minimized UWB antenna with transmission function and group delay with small variations in the operating frequency range is suitable for small multiple-input and multiple-output (MIMO) and diversity systems.

By introducing an L-shaped metal plate connecting with the spiral monopole antenna, a planar compact ultra-high-frequency (UHF) tag antenna for radiofrequency identification system is proposed. With the overall antenna size of only 13 × 9 × 1.6 mm3, the proposed tag antenna provides the measured impedance bandwidth of 12 MHz to comply with Taiwan UHF operating band (922–928 MHz). The measured peak gain and antenna efficiency are approximately −1.1 dBi and 27% for Taiwan UHF band, respectively. Meanwhile, the measured reading distance can approach 250 m. Good tag sensitivity is obtained across the desired frequency band.

In urban target localization, the presence of walls creates virtual radars (VRs), which can be exploited to aid in localization process. The fact that multipath changes with the radar locations, which are referred to as aspect dependence property, enable us to find a radar location, which reduces wall uncertainties. This paper proposes single-antenna target localization in an enclosed structure taking advantage of VRs. Using ultra-wideband signals, we can resolve the target returns and estimate the correct location by solving monostatic loci at real and VR locations. Simulation results show that the method can precisely and accurately localize the target for a wide range of timing errors.

In this paper, we present the results of using a frequency-stepped continuous-wave radar system to estimate the position of overlapping and electrically good conductive plates. We especially focus on polarimetric scattering effects caused by the step of a lap joint, which is a common welding-geometry. To model the step's contribution to the overall scattered signal, we use a two-dimensional combined field integral equation (CFIE) approach. For demonstrating its practical applicability, the implemented scattering model is verified by measurements. To emphasize the improvements of position estimation by using a CFIE approach, the outcomes of the model are compared to a commonly used point scattering model. Finally, the numerical signal is utilized to precisely estimate the position of the lap joint.

This paper addresses the study of the variation effects of incident plane wave on a multiconductor transmission line (MTL), using a coupling circuit model of MTL line with plane wave based on the method of characteristics (Branin method). This model is valid in the time and frequency domains. It has also an advantage of not presupposing the conditions of the charges applied to its ends, which allows it to be easily inserted in circuit simulators, such as SPICE, SABER, and ESACAP. We confirm the validity of this model by comparing our simulation results under ESACAP with other results, and we discuss the variation effects of the incident plane wave on an MTL line.

We present the results obtained on a multi-mode multi-band 20 W Monolithic Microwave Integrated Circuit (MMIC) power amplifier. The proposed two-stage circuit is based on the silicon Laterally Diffused Metal Oxide Semiconductor (LDMOS) technology. Thanks to dedicated design techniques, it can cover the Digital Cellular Service (DCS), Personal Communications Service (PCS), and UMTS bands (ranging from 1.805 to 2.17 GHz) and deliver more than 20 W of output power, 30 dB of gain and 50% of power added efficiency. When combined in a Doherty configuration with an incremental 40 W MMIC in a dual-path package, the resulted asymmetric MMIC (an industry first) can deliver an unprecedented LDMOS MMIC efficiency of up to 44% at 8 dB back-off in the UMTS band. Then, the DPA has been optimized in conjunction with a novel RF pre-distortion technique, leading to 33–80% energy saving at the system level.

The present paper presents a novel method to cope with the difficulty that an N-order filter can introduce a maximum number of transmission zeros (TZs) – no more than N. The method is described by a coupling topology and realized by a regular fully canonical filter structure to increase one more TZ for an N-order filter without any filter size increase. Besides, the TZ shift property, as another advantage of the proposed topology, is investigated. The coupling topology consists of a group of fully canonical coupling nodes with the harmonic node (non-resonating node (NRN)) excited by a λ/4 resonator. Owing to the unique coupling topology and coupling node distribution as well as the inclusion of an NRN, N + 1 TZs are generated by an N-order bandpass filter, while all the TZs are close to the passband and far away from the harmonic passband resulting the highly selective passbands. For demonstration, two-, three-, and four-order filters are designed and measured with the experimental results that confirm the proposed technique.

A new simple compact ultra-wideband (UWB) dielectric resonator antenna is presented. The antenna consists of a modified stepped microstrip-fed monopole printed antenna loaded with a rectangular dielectric resonator, truncated ground plane, and a parasitic strip underneath the dielectric resonator (DR). Using an optimized truncated ground plane and a combination of stepped feed line with DR an ultra-wide impedance bandwidth of 153% for (∣S11∣ ≤ −10 dB), covering the frequency range of (3.7–28 GHz) is achieved. The added parasitic strip can improve the radiation pattern, especially at high frequencies. The proposed antenna covers almost the entire UWB (3.1–10.6 GHz), Ku (12.4–18 GHz), and K (18–26.6 GHz) frequency bands. Also this antenna has an omnidirectional and stable radiation pattern over the whole operating frequency range and a compact size of (15 × 20 × 5.8 mm3) that make it suitable for wideband wireless system applications. This structure is light weight and can be easily fabricated. A prototype is built and measured. The simulated and measured results are in good agreement.

In this article, we propose three-dimensional antenna systems for determining the position of electromagnetic radiation source at an unknown location. Received signal power at different antennas and position of radiation source are used as training data for Artificial Neural Network (ANN). It is found that, a well-trained ANN is computationally efficient and capable of predicting the unknown location of the source, from the received power pattern. Two multi-antenna systems with geometry in three dimensions, namely the cube and frustum, are considered in this paper. Further, test results of the proposed method for random positions of electromagnetic source, spanning a hemisphere, are presented for the geometries considered.

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.

In this paper a novel compact multi-band printed coplanar waveguide (CPW)-feed antenna for wireless local area network (WLAN)/WiMAX/RFID applications is proposed. The proposed antenna is composed of a multi-triangular structure as metal ground plane and the radiation element with four different branches, both of the structures are printed on the same side of a substrate and the antenna is fed by a CPW. By carefully tuning the locations and the sizes of these four branches, the antenna can yield three different resonating frequencies to cover the desired bands for WLAN/WiMAX/RFID applications. The simulated and measured results demonstrate that the proposed antenna has the impedance bandwidth (for return loss less than −10 dB) of 700 MHz (2.2−2.9 GHz), 540 MHz (3.16–3.7 GHz), and 850 MHz (5.05–5.9 GHz), respectively, which can cover the WLAN 2.4/5.8 GHz bands, the WiMAX 2.5/3.5 GHz bands, and the RFID 2.45/5.8 GHz bands.

A new quad-band bandpass filter for Global System for Mobile Communications, Wireless Local Area Network, and Worldwide Interoperability for Microwave Access is designed and fabricated using the stub-loaded resonator (SLR) technology without complex fabrication process, such as via-hole or multi-layer substrate. Owing to the embedded SLR, the proposed quad-mode resonator is compact. Equivalent circuits of the proposed quad-mode resonator are analyzed in detail, and high design freedom is shown because of shifting the passband frequencies individually. Good passband selectivity and isolation of the each passband at 1.8, 2.4, 3.5, and 5.2 GHz can be well achieved due to the transmission zeros appeared near the each passband edges. Experimental results show good agreement with the simulated results.

A circularly polarized (CP) broadband antenna is proposed for wireless applications in the range of 2–3 GHz frequency. It consists of asymmetrical Koch fractal boundary patch over a reactive impedance surface (RIS) substrate. The simulations of single-layer Koch fractal antenna, dual layer with square and fractal RIS elements are carried out in a systematic way for broadband CP radiation and corresponding results are presented. For better CP characteristics, properties of fractal curves and dimensions of RIS elements are optimized. The antenna with fractal RIS iteration order one (iteration1) is experimentally studied. The 10-dB return loss bandwidth is 50.35%, whereas 3-dB axial ratio bandwidth is 7.45%, which indicate that by applying fractals concept to RIS technique, with a single probe feed, broadband CP radiation can be obtained.

In this paper, a new methodology to compare the robustness of sensor structures employed in radiofrequency design for test (RF DFT) architectures for RF integrated circuits (ICs) is proposed. First, the yield loss and defect level of the test technique is evaluated using a statistical model of the Circuit under Test (obtained through non-parametric statistics and copula theory). Then, by carrying out the dispersion analysis of the sensor architecture, a figure of merit is established. This methodology reduces the number of iterations in the design flow of RF DFT sensors and makes it possible to evaluate process dispersion. The case study is a SiGe:C BiCMOS LNA tested by a single-probe measurement.