In radar receivers, the low noise amplifier (LNA) must provide very low noise figure and high gain to successfully receive very low signals reflected off of illuminated targets. Obtaining low noise figure and high gain, unfortunately, is a well-known trade-off that has been carefully negotiated by design engineers for years. This paper presents a fundamental solution method for the source reflection coefficient providing the maximum available gain under a given noise figure constraint, and also for the lowest possible noise figure under a gain constraint. The design approach is based solely on the small-signal S-parameters and noise parameters of the device; no additional measurements or information are required. This method is demonstrated through examples. The results are expected to find application in design of LNAs and in real-time reconfigurable amplifiers for microwave communication and radar receivers.

We introduce a new technique for the design of an output combiner for Doherty power amplifier (DPA) and its effective exploitation for the development of a wideband laterally diffused metal oxide semiconductor (LDMOS) DPA. The design is enabled by a two-line impedance inverter for the DPA back-off operation, which is capable of 52% of fractional bandwidth. The technique is validated by the development of a DPA prototype for Ultra high frequency terrestrial digital video broadcast (DVB-T) applications, with optimized peak power and efficiency over 470–806 MHz. The prototype delivers between 40 and 53% of average efficiency across the band, at 49 dBm output power in average across the bandwidth, and supporting DVB-T signals with 8 MHz bandwidth and a peak-to-average power ratio of 10.5 dB. It achieves the target adjacent channel power ratio of −52 dBc at 750 MHz if digital pre-distortion is applied, and provides 47.8 dBm of output power with a drain efficiency of 44.3%.

In this paper, a novel microwave oscillator incorporating miniaturized nested split-ring resonators is proposed. The high-quality (Q) factor and wide spurious-free band of the NSRR contribute to low-phase noise and high-harmonic suppression of the proposed oscillator circuits. In addition, the NSRR is featured by compact size of 0.12λg × 0.12λg, where λg is the guided wavelength of resonance frequency. The fabricated 2.4 GHz oscillator has an output power of 11.7 dBm with 5 V DC supply and 10 mA current consumption. The second harmonic suppression is −45.49 dBc, the phase noise is −110 dBc/Hz @100 kHz, and the DC–RF conversion efficiency is measured as 30%.

The paper experimentally investigates indoor visible light communication (VLC) channels. The disturbances come from the light bulbs and other VLC systems. The paper demonstrates that the noisiest light bulbs are the fluorescent lamps which emit high frequency disturbances. Different light bulbs are examined to make an optimal carrier choice for the transmitted signal. In the next part of the paper several modulation schemes and two kinds of detector systems are compared. The paper represents also the advantages and disadvantages of receiver constructions with and without a lens. The optimum modulation for different application is investigated.

This paper presents a novel experimental simulation of ramp-time current control with fuzzy bandwidth for wireless power transmission (WPT) systems. A fuzzy logic control algorithm was designed based on the structure of ramp-time current control in active power filters through simulation of ramp-time bandwidth variation to dynamically adjust the loop width of the ramp-time comparator. Ramp-time current control is the most suitable over other current control techniques and is thus selected for the experiment. Implementation of this approach prevents over-limit of switching frequency and enhances dynamic responses, resulting in long lifespan of power switches and smooth output for WPT systems. Finally, the hypothesis and simulation results were verified by analyzing the prototype model and experiment results.

A multilayer bandpass filter with ultra-wideband passband is presented in this paper. The filter is designed to have a very wide passband with a fractional bandwidth of about 180% at a center frequency of 10.5 GHz. The filter consists of two sections of parallel-coupled lines loaded at the center with short-circuited stub. Each of the coupled line sections and short-circuited stubs is designed to be a quarter-wavelength long at the desired center frequency. As a result, the filter exhibited a selective filtering characteristic equivalent to a five-pole Chebyshev filter with a very low insertion loss. The proposed filter is realized and fabricated using multilayer liquid crystal polymer substrate. The design is successfully realized in theory and verified by full-wave electromagnetic simulation of the full layout and the experiment where excellent agreement is obtained.

This paper describes a concept of stepped impedance resonators (SIR) built from two coaxial structures fitted inside one another. The resonator is built out of a succession of two coaxial sections in cascade, where the ground conductor of the first one is the central core of the next, or vice-versa. An advantageous property of SIR is that they allow a substantial reduction in size, while keeping away the first harmonic and without strongly degrading the quality factor. After describing the theoretical behavior of the resonator, we will then present the specific properties of this approach in second order filter, conceived, and realized in the UHF band. With this example, we will also address flexibility and tunability aspects, which are the other potentially useful properties of the structure. Measurements and simulations are presented and discussed. The architecture resembles a set of two Russian dolls that fit inside one another.

In this paper, an ultra-wideband (UWB) planar monopole antenna with impedance bandwidth from 2.83 to 11.56 GHz and dual band-notched characteristics is presented. The antenna consists of a small rectangular ground plane, a bat-shaped radiating patch, and a 50-Ω microstrip line. The notched bands are realized by introducing two different types of structures. The half-wavelength spiral-slots are etched on the radiating patch to obtain a notched band in 5.15 5.925 GHz for WLAN, HIPERLAN, and DSRC systems. Based on the single band-notched UWB antenna, the second notched band is realized by etching a folded stepped impedance resonator as defected ground structure on the ground plane for WiMAX and C-band communication systems. The notched frequencies can be adjusted by altering the length of resonant cells. Surface current distributions and equivalent circuit are used to illustrate the notched mechanism. The performance of this antenna both by simulation and by experiment indicates that the proposed antenna is suitable and a good candidate for UWB applications.

A single-feed dual-band circularly polarized stacked microstrip patch antenna with a small-frequency ratio is presented. Two pair of orthogonal slits is cut on the lower circular patch for achieving circular polarization and truncated corner square patch is used as the upper parasitic element. The frequency ratio of the dual-band is 1.03. The 3 dB axial ratio bandwidth is 1.3% for the upper band and 1.1% for the lower band. Proposed structure is fabricated on the FR-4 epoxy substrate and fed by SMA connector. The measured results are in good agreement with the theoretical and simulated results. The antenna shows stable radiation characteristics in both bands of operation.

A single-fed circularly polarized microstrip antenna is proposed where the antenna structure exhibits truncated corners in the radiating square patch. The truncated corners square patch structure is loaded with a circular slot and is resonating at 2.25 GHz with circular polarization. Furthermore, the proposed antenna is stacked using an upper circular patch thus achieving a dual-band circularly polarized pattern. The dual-band antenna resonates at 2.25 GHz in the first band and with impedance bandwidth ranging from 4.4 to 5.5 GHz in the second band. The size of the proposed stacked structure is compact compared with the conventional circularly polarized stacked antenna designs. Proposed structures are fabricated and fed using Subminiature version A (SMA) connector. The measured results are in good agreement with the simulated. The antenna shows stable radiation characteristics for the entire band of operation.

In this paper, a new antenna has been proposed with dimensions of 28 × 28 × 0.8 mm3 and the ability of operating in ultra-wideband (UWB) frequency and switching three notched bands. In the structure, to achieve the removal of characteristic of three frequency bands, a rectangular patch with an H-shaped slot on its surface and two C-shaped arms on its sides have been used. In addition, the designed antennas have the ability of operating in five different modes. To achieve the performance of reconfiguring, three pin diodes are used on the slots of rectangular patch and those two C-shaped arms. Also, with the defect ground structure and creating two rectangular slots and two L-shaped slots on the ground plane we make the excite of additional resonances and thus increase antenna bandwidth. Simulation and measurement results show that the designed antenna is able to cover the range of frequencies 3–12 GHz and a controllable frequency band rejection in the three frequency bands 3.2–3.75 GHz (WiMAX), 5.05–5.9 GHz (WLAN), and 8–8.45 GHz (ITU). The proposed antenna decreases the interference of the mentioned wireless systems with the UWB frequency.

This paper presents a compact broadband printed monopole antenna with U-shaped slit in the partial ground plane and rectangular parasitic patches adjacent to the microstrip line for multiple applications. The optimal dimensions of the proposed antenna are 35 × 25 × 1.5 mm3 and is fabricated on commercially available low-cost FR4 substrate with εr = 4.3 and 0.025 loss tangent. Due to introduction of rectangular parasitic patches and U-shaped slit large bandwidth has been achieved. The impedance bandwidth (return loss, magnitude of S11 < 10 dB) of the proposed antenna is 139% (2.9–16.3 GHz). The proposed antenna covers ultra wide band applications, 5.2/5.8 GHz WLAN bands, 3.5/5.5 GHz WiMAX bands, X band (8–12 GHz), satellite communication, and other wireless communication services. The study shows that there is good agreement in simulated and measured results. Nearly stable radiation patterns have been obtained throughout the operating band. Antenna results and details are discussed and elaborated.

In this paper, a novel circularly polarized square slot microstrip antenna is proposed for radio frequency identification (RFID) applications. The circular polarization is achieved by incorporating an arc-shaped strip in the square slot antenna. This antenna is fed by deformed bent feeding line to achieve a broad bandwidth (BW). The key parameters of the antenna are used for parametric study to understand the influence on the antenna performance. To validate simulation results of the design, a prototype is fabricated on the commercially available FR4 material. Measured results show a good agreement with the simulated results. It is found that the antenna shows an impedance BW of 170 MHz (844–1014 MHz) and axial-ratio BW of 170 MHz (834–1004 MHz), which shows that the proposed antenna is a good candidate to be used as a RFID antenna.

Demands for very high-speed wireless communication access is rapidly growing with respect to the increasing data rates for the use of rich multimedia content in various applications of defense, enterprise, industrial, and public domains. To serve these gigabit fidelity (Gi-Fi) uses for various wireless applications, millimeter wave (MmW) wireless technology with huge bandwidth in licensed/unlicensed bands is triggering boundless avenues. In this research, the concept of substrate-integrated waveguide (SIW) and exponentially tapered slot (ETS) antenna are used together design a high-gain, efficient planar dielectric-loaded antenna for MmW-based Gi-Fi wireless communications using unlicensed 60 GHz band in the MmW family. The SIW is used to feed the antenna and a dielectric is utilized increasing the gain. The dielectric-loaded ETS antenna and compact SIW feed are fabricated on a single substrate, resulting in low cost and easy fabrication utilizing printed circuit board process. The measured gain of single-element antenna is 11.4 dB, with radiation efficiency of 96.84% at 60 GHz. Then indoor radio wave propagation studies are carried out using elliptically dielectric-loaded ETS antenna with radio frequency measurement equipment to measure and model propagation channels at 60 GHz. The attained simulations are compared with the experimental results.

A circularly polarized (CP) and high gain Microstrip antenna is designed in this paper using metamaterial concepts. The antenna, built on a metamaterial substrate, showed significant size reduction and less mutual coupling in an array compared with similar arrays on conventional substrates. Demonstrated to have left-handed magnetic characteristics, the methodology uses complementary split-ring resonators (SRRs) placed horizontally between the patch and the ground plane. In order to reduce mutual coupling in the array structure, hexagonal-SRRs are embedded between antenna elements. The procedure is shown to have great impact on the antenna performance specifically its bandwidth which is broadened from 400 MHz to 1.2 GHz for X-band and as well as its efficiency. The structure has also low loss and improved standing wave ratio and less mutual coupling. The results show that a reduction of 26.6 dB in mutual coupling is obtained between elements at the operation frequency of the array. Experimental data show a reasonably good agreement between simulation and measured results.

Design and fabrication of a traveling-wave printed planar composite right/left-handed (CRLH) antenna are presented in this paper. The proposed traveling-wave antenna constructed of four unit cells with b-shaped geometries, which each occupy 2.49 mm length, 6.32 mm width, and 0.8 mm height. In this paper, with designing the optimized b-shaped printed planar structure by the standard manufacturing techniques on the printed circuit boards, which perform the roles of the series left-handed (LH) capacitances (CL), the antenna size, bandwidth, and radiation specifications may be improved to the desirable range. Also, to obtaining the desired results the spiral inductors have been used, which play the roles of the shunt LH inductances (LL). The fabricated antenna with the proposed structure can be covered more from 2 GHz measured impedance bandwidth with minimum of the measured gain and radiation efficiency equal to 6.1 dBi and 52.3%, respectively, which happen at 9 GHz. According to the provided results, the proposed compact ultra-wideband traveling-wave antenna is a potential candidate to use in the embedded electronic systems and portable wireless communication devices.

In this article, a new construction of a small planar dual-band fed printed monopole antenna based on coplanar waveguide is suggested. Impedance matching for dual-band operations is obtained by embedding three vertical strips with different sizes in the U-shaped conductor-backed plane. The main problem of the designed antenna is the measuring of the specifications with the Agilent 8722ES Vector Network Analyzer, when the coaxial cable is connected to the antenna. Hence, in this paper a new method for decoupling the cable from the antenna is presented. This method is based on using the ferrite bead. The ferrite bead reduces the cable radiation, so that its position plays the important part in the antenna radiation characteristics. The fabricated antenna includes the benefits of the miniaturized size and dual-band operating specifications, so that the mentioned properties have been achieved without modifying the coplanar-waveguide-ground surface or radiator patch. The antenna has the small size of 15 × 15 × 0.8 mm3and bandwidths with S11 < −10 dB about 2.2 GHz (5.05–7.25 GHz) for WLAN-band or IEEE 802.11a-band and 5.2GHz (7.6–12.8 GHz) for X-band, which correspond to 36 and 51% practical bandwidths, respectively. The antenna measured peak gains are about 1.8 dBi at WLAN-band and 4.3 dBi at X-band.

In this article, the interesting constructions of the notch-loaded rectangular patch S-shaped antennas with L-strip feeding for multiband operations are presented. Implementing the L-strip feeding leads to creation of good benefits including several resonating frequencies, no cross-sectional area, simplicity in designing and constructing, stable gains and efficiencies, and the impedance matching. The proposed antennas are realized on the different substrate materials and the dramatic changes in characteristics are reported. These antennas are simulated, tooled, fabricated, and tested to provide the better performances in terms of return loss and bandwidth. Through the proper selection of the dimensions as well as the arrangement of the L-strip, the desired resonant modes of the antennas are excited in between 6–45, 3–20, and 2–16 GHz. Results of the radiation patterns, gains, and efficiencies of the constructed antenna on the foam substrate are studied and discussed. The maximum and minimum values of the gains and radiation efficiencies of this antenna are 10 dBi and 93%, and 1 dBi and 30%, respectively. The simulation results are obtained using method of moment based on the electromagnetic solver IE3D and are in good agreements with the experimental results, which were obtained from the spectrum analyzer.