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In this paper, a hybrid continuous inverse class‐F high‐efficiency power amplifier based on phase shift analysis is proposed. A broadband and high‐efficiency microwave power amplifier are designed by adopting load pull, source pull technique, and low‐pass filter matching structure. The measured results show that the drain efficiency ranges from 67.5% to 77.8%, the saturated output power ranges from 40.2 to 42.4 dBm, and the saturated power gain ranges from 10.2 to 12.4 dB in the working frequency band from 2 to 3 GHz. The power amplifier proposed in this paper fits the current broadband microwave communication technology and plays an important role in the transmission of high data flow signals by wireless transmitters. [ABSTRACT FROM AUTHOR]

Metamaterial structure‐based terahertz absorbers all are passive, once the preparation is complete, their absorption properties are also determined unable to adapt to the increasingly complex electromagnetic environment. In this paper, a kind of phase change film‐based tunable terahertz metamaterial absorber is proposed. And on the basis of current three‐layer type terahertz absorber on present metamaterial structure, a layer of vanadium dioxide (VO2) phase change film is added to change the conductivity of VO2 by controlling ambient temperature, so as to trigger the insulator metal transition characteristics of VO2 film, which can control the absorption rate of terahertz metamaterial absorber. Theoretically, design scheme in this paper has 80% modulation depth to the amplitude of absorption. That is, tunable terahertz electromagnetic absorber has potential application value in electromagnetic stealth in terahertz band, radiation detectors, and broadband communication fields. [ABSTRACT FROM AUTHOR]

A broadband antenna array for 28 GHz 5G communications is presented in this paper. The antenna array has dimensions of 45 × 20 mm2 and has a measured operating band in 25.052‐34.923 GHz frequency range. A 4‐way feed network to excite its array elements was designed and optimized for the operating band. The single element consists of two co‐centric wire hexagons backed by another hexagonal ground loop of larger radius. The resulting monopole is surrounded by vias arranged in an inverted U‐shape manner for better performance. The antenna array has a minimum radiation efficiency of 85% with peak gain of 12.15 dBi. The antenna has narrow beam‐widths of 44.3° and 12.5° in two of its respective planes. The antenna is fabricated on an ultra‐thin Rogers substrate. The proposed antenna is deemed suitable for future 5G communication systems due to its simple design, compact size and low fabrication cost. [ABSTRACT FROM AUTHOR]

This paper presents a design procedure for a phased array feed network. The procedure is validated by designing and fabricating a set of 28 GHz 8‐element beam steerable antennas. Within the feed, a Taylor n‐bar amplitude taper is implemented using unequal power dividers. At boresight, the taper reduced the sidelobe level by 2.84 dB to −15.2 dB. Beam steering from 0° to 48° is achieved using meanders. An empirical formula for the meander widths is proposed, enabling independent control of amplitude and phase. Empirical formulae for the initial parameters of the unequal dividers are also proposed. The wide transmission lines in this feed network are compatible with low‐cost PCB fabrication techniques. [ABSTRACT FROM AUTHOR]

A compact broadband ambient RF energy harvester operating from 1800 MHz up to 2.5 GHz is proposed in this paper. This work is motivated by the huge amount of free and continuously available RF energy in the surroundings that can be utilized into useable energy. Harvest performance is investigated using two antennas in this work, a circular polarized and an array antenna. Due to low ambient power densities, a multistage rectifier is utilized to improve the output dc voltage of the proposed system. Measurements indicate the system is capable of harvesting up to 1.8 Vdc output from nondedicated ambient RF energy sources in an urban area, which is significant in the absence of other energy sources. [ABSTRACT FROM AUTHOR]

In this paper, we propose a newly enhanced Doherty combiner by adding a 180° transmission line to the stage of the peaking amplifier of a typical Doherty combiner such that the designer can easily construct a combiner having a phase deviation to be turned on within the intended bandwidth. Given such characteristics, the proposed structure provides wider phase bandwidth and better performance with respect to power combining rate than the conventional structure does. We introduce formulas for the design variables of the added transmission line and also demonstrate its validity through circuit design and experiment. [ABSTRACT FROM AUTHOR]

This paper presents a low‐profile wideband pattern reconfigurable dual circular patch antenna. The basic unit of the antenna is based on the mathematical model of a circular patch antenna design. Although to optimize the large size of the structure, an innovative way of introducing slots is presented that effectively reduces the overall size. Two different types of slotted circular structures are proposed with optimized sizes. The first design is based on L‐slots, while the second is the dual vertical slotted antenna. Both structures are designed and simulated on FR4 and RT‐Duriod 5880 substrates using the EM simulators, IE3D, and HFSS. The optimized antenna structure among the proposed ones has dual circular patches and the pattern reconfigurability is achieved by only two PIN diode switches. Thus, a steering capability of the antenna beam in two different directions at the same resonant frequency is achieved. The antenna covers a wideband of 500 MHz (ie, 1.3‐1.8 GHz) with a high gain of 3.95 and 4.05 dB for both switching cases. To validate the designs, the antennas are fabricated on FR4 epoxy substrate. The measured results are closely related to the simulated results, thus making the design suitable for recent and upcoming multistandard wireless communication systems. [ABSTRACT FROM AUTHOR]

Abstract: For a frequency‐division duplex (FDD) wide‐band code‐division multiple‐access (WCDMA) system, transmit (TX) signal leakage at the receiver input degrades the receiver performance. To cancel this TX leakage, a frequency selective feedback was previously proposed, but it had an unpredictable feedback loop characteristic due to the uncertainty of the duplexer impedance. This paper presents a new method to achieve TX leakage cancellation regardless of the duplexer impedance. In addition, a local oscillator (LO) phase shift technique is proposed to apply this method for multi‐band. A receiver adopting these proposed techniques is implemented using a 0.18‐μm CMOS process to prove the concept. The measured TX attenuations of the high‐ and low‐band are 17‐dB and 20‐dB, respectively, and the measured noise Figure (NF) degradations of the high‐ and low‐band are 0.6‐dB and 0.5‐dB, respectively. The measurement results demonstrate effectiveness of the proposed techniques. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a wideband single‐pole double‐throw (SPDT) switch using the traveling‐wave concept was demonstrated. Realized in 0.5 μm AlGaN/GaN HEMT process, it achieves good performance at Ku‐band despite the process being intended for low‐frequency applications. This type of switch combined the off‐state shunt transistors and series coplanar waveguide (CPW) lines to form an artificial transmission line. CPW is also used to eliminate parasitics associated with through‐substrate microstrip vias and coupling of adjacent transmission lines. An accurate switch HEMT model was extracted and used in the design. A 9–25 GHz single‐pole double‐throw (SPDT) switch in conjunction with quarter‐wavelength impedance transformers demonstrates an insertion loss of less than 6 dB, return loss better than 10 dB and an isolation of better than 25 dB. [ABSTRACT FROM AUTHOR]

A compact low profile dual-polarized filtering antenna with metamaterial for wideband base station applications is proposed in this paper. The antenna is fed by two inverted L type coupled line, artificial magnetic conductor is utilized as the reflector. Meanwhile, a stepped impedance resonator is introduced into the inverted L type feedline to suppress the radiation of the antenna outside the operating band and achieve compact structure. The mentioned antenna has 11.5 mm (0.0958λ0) profile and two frequency doubling suppression characteristics. The return loss of the antenna is <-10 dB from 2.5 to 3.2 GHz. The gain of the proposed antenna is greater than 6.5 dB over the operation band. The filtering antenna is processed and fabricated, and the measured results are consistent with the simulation results. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, an ultra-wideband (UWB) antenna with reconfigurable performance is proposed. The antenna consists of a U-shaped radiation patch and a ground plane which is symmetric with the edge of the radiation patch. By using two open-ended L-shaped slots (OEL-S) and one U-shaped slot Defected Ground Structure, the dual notched bands at 3.5 GHz for WiMAX and 5.5 GHz for WLAN are obtained. Three switches are embedded in both L-shaped and U-shaped slots in order to achieve four switchable modes by switching them between ON and OFF states. There are three modes that the antenna can be switched in, which are dual, single and no band-notched modes. The measured result illustrates that the operation frequency band is from 2.7 GHz to 12 GHz (VSWR < 2). Moreover, the conceptual circuit model and time-domain characteristics of the antenna are also proposed to investigate the dual band-notched performance. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1326-1332, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT A 6-18 GHz wideband substrate integrated waveguide (SIW) H-Plane dual-ridged end-fire antenna is presented in this paper for conformal application. The dual-ridged configuration is used to reduce the cut-off frequency and the characteristic impedance of the SIW. Three groups of air-vias applied in the front of the dielectric slab can improve the impedance matching. And two bending air slots are integrated in the top metallic layer of the SIW to correct the phase disorder and to further improve the impedance matching performance. With these novel improved designs, the proposed antenna shows experimentally a good impedance matching (|S11| < −7 dB) and exactly end-fire gain (>4.2 dBi) performances in the frequency range of 6-18 GHz. The proposed antenna also keeps low-profile and easy flush-mounted characteristic which is suitable for conformal applications of high speed moving objects. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:286-292, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT The analysis and design methods of a broadband coplanar Wilkinson power divider are proposed in this paper. The novelty is that cascaded two sections of coupled asymmetrical coplanar strips (ACPSs) are utilized to obtain broadband performance over X-band and two resistors are used for isolation. The design equations are derived using even- and odd-mode analysis. The specific structure parameters for broadband performance over X-band are obtained through electronic design simulation tool and quasi-static conformal mapping technique. The power divider is fabricated on GaAs substrate and is compatible with GaAs MMIC process. The measured results of the power divider show close agreement with the simulation. The measured return loss S11 is better than −15 dB across the entire X-band, 8-12 GHz. Good dividing and high isolation properties are also revealed through measurements. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:307-312, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT Compact super wideband (SWB) patch antenna using diversities of reactive loaded technique is presented in this paper. The antenna is consists of two U-slots in the radiating patch with two inverted U-slot and a triangular slit on the ground plane. By having those structures, a super wide operating bandwidth is produced from 2.43 GHz to 32.93 GHz with a fractional bandwidth of 172.5%. Moreover, while only having a compact dimension of 25 × 26 mm2, the proposed antenna still can produced an acceptable gain from 2.73 dBi to 7.35 dBi over the frequency range. This compact SWB antenna is very potential to be used for SWB applications because it provides sufficient impedance bandwidth, high gain and stable radiation pattern that are near omni-directional pattern. The performance of the proposed antenna is observed and analyzed comprehensively in this letter. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2811-2814, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT This paper reports an investigation into the effect of carbon dioxide (CO2) gas on various ultra wideband channel coefficients. Measurements were conducted using apparatus consisting of a rubberized tube (6 mm diameter) connected to a source of CO2 or nitrogen (N2). For support, the rubberized tube was wrapped twice around a PVC pipe (160 mm diameter). The rubberized tube was flushed with 100% CO2 several times before being sealed in the tube at atmospheric pressure. In between measurement trials, removal of CO2 was achieved by flushing with pure nitrogen. A Vector Network Analyzer (VNA) using two identical directional antennas, with the wrapped section of tubing placed in-between, measured the channel coefficients over ultra wideband frequency spans of (0.3-8) GHz and (1-2) GHz. Significant magnitude differences between the baseline condition and that of CO2 were observed. We found the same signature of difference curves over the same frequency spans for different measurements. Difference in shape in the frequency band of (1-2) GHz is the same as that of the measured difference over 1-2 GHz in entire frequency band of 300 MHz to 8 GHz for the measured channel coefficients. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1543-1546, 2016 [ABSTRACT FROM AUTHOR]

This paper presents results for a novel active transmit-receive antenna and designing a high port isolation dual frequency orthogonally polarized inset rectangular patch antenna. Measurements show an improvement of 20 dB in port isolation relative to the conventional antenna, operating at 2.4 and 2.6 GHz. An inset microstrip patch antenna operating at 10.5 GHz having 12.22% bandwidth has been used as a reference antenna. It is also shown that the return loss level of the antenna has been enhanced by using active matching with RC mutator networks from -10.62 dB to -14.76 dB respectively. In addition, this paper presents the design of an integrated 2.4/2.6 GHz full duplex dual-band antenna transceiver for WLAN 802.11 a/b/g applications. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2843–2848, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22845 [ABSTRACT FROM AUTHOR]

In this paper, the regular microstrip dipole antenna shape is modified by adding upper and lower triangular patches, which makes it look like a rhombus. The rhombus shape is chosen because of its wideband characteristics over the rectangular one. The presented antenna provides a wide bandwidth of more than 100%. The measured and computed VSWR and radiation patterns for one element and the mutual coupling for two elements are presented in the paper. The proposed antenna provides endfire radiation patterns with wide beamwidth and low cross polarization level which make it a good candidate for phased arrays and radar systems. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2461–2464, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21978 [ABSTRACT FROM AUTHOR]

A novel coaxial-fed E-shaped microstrip patch antenna is proposed in this paper. The proposed antenna is found to have a much broader impedance bandwidth as compared to the conventional U-slot antenna. An impedance bandwidth of about 33.8% is achieved for the proposed E-plane antenna. Through the use of a washer on the proposed antenna, the probe inductor is compensated, and an impedance bandwidth of 40% is thus obtained. The E-plane radiation pattern for both the proposed antenna and the one incorporated with the washer remains relatively constant through the band. A comparison between the U-slot antenna and our proposed antennas is made in the paper. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 348–352, 2000. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, a compact reconfigurable single/dual notch band ultrawideband (UWB) antenna with triple notch band characteristics is presented for portable UWB applications. The desired compactness and wideband is achieved using fractals in antenna design. It has the compact dimensions of 24.5 mm × 20 mm. The single/dual notch band reconfigurability is demonstrated in WiMAX band as well as in X-band using two p-i-n diodes for efficient utilization of UWB bands in case of no interference scenarios. The band rejections are obtained by introducing two C-shaped slots in the fractal monopole, whereas band rejection in WLAN band is achieved by placing two C-shaped single split ring resonator on either sides of feed line. In addition, the time-domain characteristic of antenna is also evaluated in terms of fidelity factor, which is more than 0.71. These results illustrates that the presented antenna is appropriate candidate for portable UWB applications. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:509-514, 2016 [ABSTRACT FROM AUTHOR]

ABSTRACT This paper presents a novel design for an optimized circularly polarized microstrip antenna. Circular polarized microstrip antennas have many uses due to its low profile design. However, one of the microstrip antenna's main limitations arises from its narrow frequency bandwidth. Therefore, it is necessary to use special design techniques in order to increase the operating frequency bandwidth while maintaining all of the other respectable optimum radiation characteristics. The proposed design involves using a dual-feed square patch, which is gap coupled with two parasitic patches in a mirrored L-shaped configuration. This design resulted in an axial ratio bandwidth of 11%, S11 bandwidth of 14% and a gain of 9 dB at the 2.15 GHz center frequency. The proposed design was built, and the measured results were in agreement with the simulation results. Additionally, this antenna design was used in an array structure in order to increase the gain, while maintaining a good axial ratio. These enhanced radiation results allow the use of the proposed antenna design in many domains such as wireless and military applications without facing the limitations of the narrow frequency bandwidth. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:597-603, 2016 [ABSTRACT FROM AUTHOR]

This paper presents the concept of using a harmonic trap to design a wideband reconfigurable antenna. The reconfigurable antennas can be used to select one of a number of operating frequency bands. If these bands cover a very wide frequency range, then one of the higher-frequency bands can be a harmonic of a lower band. When the antenna operates at the lower band, it can have a good match at the high frequency. This paper proposes a technique for designing a wideband reconfigurable printed dipole antenna so as to select only one of the operating frequency bands by using a harmonic trap. The antenna is designed, fabricated, and measured. It is shown that by using switches and harmonic traps, a reconfigurable printed dipole antenna can be designed over a frequency range of 3:1. The antenna is thus suitable for frequency switching in the FCC ultra-wideband allocation. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 927–929, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21521 [ABSTRACT FROM AUTHOR]

This paper presents the design simulation, implementation, and measurement of a miniaturized GPS/K-PCS/ISM (2.4-GHz) triple-band LTCC meander-chip antenna for mobile-communication handsets. The dimensions of the LTCC chip antenna is 8.6 × 15 × 1.5 mm. In this paper, the bottom meander radiating patch is tuned to the GPS-band, the middle meander antenna with via-hole connection contributes to the K-PCS-band operation and the top radiating patch is tuned to the ISM-band (2.4 GHz). With 2.0:1 VSWR impedance bandwidth definition, the lower, middle and upper bands have impedance-bandwidth values of 110, 140, and 60 MHz, covering the bandwidth of the GPS/K-PCS/ISM (2.4-GHz) bands. Satisfactory agreement between the simulated and measured results for the antenna patterns and impedance bandwidth are achieved. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 160–162, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21292 [ABSTRACT FROM AUTHOR]

The detailed study of a planar asymmetrical dipole, realized on a ε = 4.50 substrate, with a rectangular slit etched on one of the two dipole arms, is described in this paper. The measured prototype fulfills the bandwidth requirements of both ultrawideband and WLAN communications at 2 and 5 GHz. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26185 [ABSTRACT FROM AUTHOR]

Recently, wideband antennas with band-notched behavior have attracted increasing interest. This paper presents a conical monopole antenna with four C-shaped slots to achieve improved band-rejection behavior with at least 28 dB of gain suppression. Compared to previous work reported in the literature, the antenna provides a relatively wide rejection band with increased gain suppression, at the notch-band center frequency. The antenna also provides an omnidirectional radiation pattern at frequencies within the operating band. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26132 [ABSTRACT FROM AUTHOR]

A compact broadband patch antenna is proposed in this paper for global ultra-high-frequency (UHF) RF identification (RFID) applications. The antenna is composed of four synchronous shorted patches that resonate at four different frequencies, broadening its impedance bandwidth. A central loop is incorporated to feed the four patches simultaneously, which provides the required input reactance for matching to the chip as well. Since the current of neighboring patch is vertical to each other that they can radiate well without canceling each other, the gain is stable over the whole frequency band. Prototype is fabricated and tested, which shows that the impedance bandwidth can cover the whole UHF RFID band (840 MHz - 960 MHz), and the read range is over 3 meters when EIRP is set to 30 dBm at the reader. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2653-2657, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25560 [ABSTRACT FROM AUTHOR]

This paper analyzes the influence of amplitude and phase error of different path on single sideband modulator (SSB) which can be used as an upconverter. Unwanted sideband suppression expression and error variables equation for maximum output sideband suppression are also deduced. The simulation curve shows the variation of sideband suppression with the amplitude and phase error of the components of SSB is given. Simulation results show that components of the amplitude and phase of the highly consistent or inconsistent amplitude and phase which meet the relationship can achieve higher sideband suppression for the SSB. The completed modulator used as an upper sideband upconverter shows -11 dB typical conversion gain with 22-dB sideband suppression. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2590–2594, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23721 [ABSTRACT FROM AUTHOR]

This paper presents a dual-band bandpass filter by introducing transmission zeroes in the passband of a broadband bandpass filter using square-loop dual-mode resonators. The transmission zeroes are achieved by using a dual-mode resonator. The dual-mode resonator is attached to two transmission lines of same length. These lines are coupled to similar transmission lines that are attached to the I/O ports. The filter has a compact size, low losses, and good rejection between the two bands. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1567–1570, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23427 [ABSTRACT FROM AUTHOR]

Conventional techniques for designing waveguide-to-finline taper transitions are based on the design of a suitable impedance transformation profile used for pure TEM lines. Change of finline/slotline gap not only causes change in impedance but also correspondingly change in propagation constant. Thus the existing analysis, used for purely TEM lines, is inadequate in dealing with finline tapers. Analysis has also been carried out by varying the propagation constant using closed-form expressions. Comparison of various taper profiles has been presented in this paper. Further in the present work, the width of the finline contour itself has been varied according to the function profiles as exponential, parabolic, cosine, and cosine squared forming the tapers. Broadband tapered transition from rectangular waveguide to offset slot asymmetric finline has been realized by gradually increasing the slot width using exponential taper profile. The designed asymmetric finline taper (two transition with one lambda spacing) using impedance variation with width exponential profile showed a very good result of 0.15–0.25 dB in the entire Ka-band. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2254–2257, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22688 [ABSTRACT FROM AUTHOR]

A spiral antenna with a helix loaded is investigated in this paper. Through combining the spiral with a helix together, circular polarization can be achieved in dual bands. Since the helix is loaded in the lower part of the spiral, this technique doesn't increase the antenna's volume but at the same time introduces another CP band. The experimental result shows that the lower band and upper band are 4.0% and 62.07% respectively. The characteristics of impedance, current distribution and radiation pattern will also be presented. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1939–1942, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22596 [ABSTRACT FROM AUTHOR]

In this paper, a novel design of a triangular-slot antenna with rectangular tuning stub for 2.4/5.2/5.8 GHz triple-band applications is presented. The prototype consists of a triangular slot and rectangular tuning stub. Results show that the impedance matching of the proposed antenna is greatly affected by the feed gap width. Experimental results indicate that the impedance bandwidth (VSWR 1:2) of the proposed antenna is about 423 MHz for the 2.4-GHz band and 1.92 GHz for the 5-GHz band. The simulated and experimental results for the return loss, radiation patterns, and gains are presented and discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1793–1797, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22621 [ABSTRACT FROM AUTHOR]

In this paper, compact L-shaped notched printed antennas with dual slits for multiband and wideband applications are presented. Here, an L-shaped notch is cut on one side of the nonradiating edge of the rectangular patch with dual narrow slits cut on the other side. This patch is kept 2 mm away from the ground plane. The size of the ground plane is taken to be 38 × 10.8 mm2. Here, the study consists of the study of the proposed antenna with two types of ground planes, one with rectangular ground plane and the other with modified ground plane. Using rectangular ground plane, wideband and multiband operation is achieved with overall bandwidth of 6.84 GHz (110%). Again, by using modified ground plane, the overall bandwidth of the antenna is further increased to 7.86 GHz (114.5%). Moreover, the overall size of the proposed antennas is quite compact i.e., 38 × 38 mm2. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2022–2026, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22638 [ABSTRACT FROM AUTHOR]

A novel wideband CP helix antenna with exponential spacing is presented in this paper. Since traveling wave current over a wide range of frequencies has been excited, it possesses better performance. Both numerical results and experimental results show that the axial ratio bandwidth of the exponential spacing helix (ESH) antenna is 58.6% greater than that of the linear spacing helix (LSH) antenna in the same conditions. The characteristics of impedance, power gains, and radiation patterns for the ESH antenna are also investigated and compared with LSH antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1525–1530, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22485 [ABSTRACT FROM AUTHOR]

This paper presents the design approach and test results of a four-stage 1.6-W K-band MMIC power amplifier developed for point-to-point radio applications. The design of the power amplifier was based on a small signal low loss matching technique. The MMIC was fabricated employing GaAs based high-performance 0.4 μm multifunction self-aligned gate MESFET technology. We achieved a minimum PAE of 22%, output power of 1.6 W (0.53 W/mm power density) and associate gain of 18 dB over the 17.5–20 GHz frequency range. Thus, we successfully applied a small signal technique in a four-stage K-band MMIC power amplifier to achieve bandwidth, power output and PAE performance objectives. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1521–1525, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22486 [ABSTRACT FROM AUTHOR]

A printed monopole with coplanar waveguide-fed antenna for ultra-wideband applications is proposed. The proposed antenna includes a rectangle-shaped patch as a radiator, two ground planes with symmetrical notch, and feed excitation. It covers the all ultra wideband (UWB 3.1–10.6 GHz) and has 7.8 GHz (2.8–10.6 GHz) measured return loss bandwidth. In modifiable design, we choose to design the notches on the ground plane, the height of the proposed antenna, and the width of the radiator, and have to obtain broad impedance bandwidth and accessible measurement parameters. The experiment results have shown acceptable omnidirectional radiation pattern and fine gain in this paper. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1435–1438, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22420 [ABSTRACT FROM AUTHOR]

In this paper, a surface-mountable, reconfigurable monopole antenna was designed for array antenna operations in the DCS-1800 and PCS-1900 bands. First, the elementary structure was obtained by folding a metallic strip into a V-shape, and then soldered to a 50-Ω microstrip feed line printed on a metallized substrate. For the optimized structure, an impedance bandwidth of 22.7%, corresponding to the frequency range 1560–1960 MHz, was obtained. Measured radiation patterns are similar to that of a monopole antenna, and the maximum measured gain is about 1.8 dBi at 1.6 GHz. Next, this elementary antenna was used for realization of both linear- and planar-array antennas. The linear-array shows a dual and wideband behavior with good impedance matching and asymmetric radiation patterns, whereas the planar-array presents a unique resonant band with moderate adaptation and symmetric radiation patterns. The measured gain for the two arrays is about 5 dBi. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1486–1491, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22437 [ABSTRACT FROM AUTHOR]

In this paper, a simple design cylindrical dielectric resonator antenna (CDRA) with wide aperture-coupled for broadband applications has been proposed. For improving impedance matching, microstrip feed-line was designed as a fork-like to obtain two resonant modes excitation and lead to a wider impedance bandwidth. Experimental results indicate that the measured bandwidth is 10.6% (S11 < -10 dB) with broadside radiation pattern. Additionally, the proposed antenna gain is near 7.9 dBi. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49:1064–1067, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22359 [ABSTRACT FROM AUTHOR]

In this paper, microstrip-line-fed rectangular microstrip antenna with open-end meandering slots in the ground plane for compact broadband operation is presented. The proposed design consists of a rectangular patch which is fed by a 50-Ω center fed microstrip-line feed. Three identical narrow open-end meandering slots were embedded in the antenna's ground plane parallel to the rectangular patch's radiating edge. Experimental study is carried out by varying the length of the open-end meandering slots. Using open-end meandering slots in the ground plane, the resonant frequency of the antenna is greatly lowered with large enhancement in bandwidth when compared with conventional microstrip antenna. With the proposed design, an extreme reduction of 82.9% in the antenna size is obtained with a wide bandwidth of 40%. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 824–827, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22267 [ABSTRACT FROM AUTHOR]

In this paper, a broadband microstrip Marchand balun is presented. It is implemented by new vertical coupled structure, which is suggested to improve the coupling effect in the conventional coupler. Using this vertical coupling structure, the Marchand balun shows broad bandwidth of larger than 115% at the center frequency of 2.3 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 752–755, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22281 [ABSTRACT FROM AUTHOR]

Design of an ultra wide band (UWB) filter using tightly coupled lines in micro strip medium suitable for UWB communications has been presented in this paper. Coupled lines with centrally loaded open circuited stubs have been appropriately chosen to locate the two attenuation poles, close to either side of the desired pass band. Experimental results of a 3.1–5.3 GHz filter designed using the present method have been verified against the results obtained from circuit model. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 436–439, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22166 [ABSTRACT FROM AUTHOR]

This paper presents the theoretical and simulation investigations of an E-shaped patch antenna applicable in modern mobile communications. It shows marked improvement in the bandwidth when compared with rectangular patch antenna with acceptable radiation pattern. Further, the bandwidth is optimized with respect to notch length, width, and position. Typically, the antenna shows an enhanced impedance bandwidth of 32.5%. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 4–7, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22024 [ABSTRACT FROM AUTHOR]

Reconfigurability in an antenna system is a desired characteristic that has been the focus of much research in recent years. The paper demonstrates miniature re-configurable antenna designed and fabricated on the high resistivity Si substrate. This antenna can integrate with a novel microelectromechanical systems actuator for reconfiguring the operating frequency and is used for SoC (System on the chip). The switching between the two different frequency bands is achieved through the use of RF-MEMS switches. According to the open/closed experiment results, when switch is on and off, the antenna operating frequency is 12.3 GHz and 13.1 GHz with low return loss, respectively. The final model radiates at two widely separated frequencies with very similar radiation patterns. The proposed concept can be extended to reconfigurable linear antenna arrays or to more complex antenna structures with large improvements in antenna performance. It is important for the next generation wireless communications and integrated antenna system on the chip. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2413–2416, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21979 [ABSTRACT FROM AUTHOR]

A numerical and experimental study of a circular-slot antenna, fed by a coplanar waveguide with a rectangular stub, is proposed in this paper for ultra-wideband communications. The antenna impedance bandwidth, phase linearity, gain and radiation patterns are presented, together with the time-domain impulse response. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2272–2277, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21900 [ABSTRACT FROM AUTHOR]

This paper presents a dual-band internal WLAN PIFA for 2.4/5 GHz laptop applications in consideration of the influences of laptop housing and LCD. The prototype antenna is modified when installed along the perimeter of the display panel of the laptop housing. The proposed antenna has a small ground plane and achieves an impedance bandwidth of 250 MHz (2.37–2.62 GHz(in Bluetooth band and 950 MHz (4.98–5.93 GHz(near 5 GHz in WLAN band within 2:1 voltage standing wave ratio (VSWR(. It also shows good antenna gain with small volume. These features make it an alternative for use in dual-band WLAN antennas. Design details for the proposed antenna in the case of the antenna itself, and the application of laptop PC housing are described, and experimental results of the antenna achievements are investigated and discussed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48:2349–2354, 2006;Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.21943 [ABSTRACT FROM AUTHOR]

A promising design of integrating a wideband printed monopole antenna in a system in package (AiSiP) for wireless local area network (WLAN) operation in the 2.4 GHz band is presented. The antenna is an inverted-F monopole antenna printed on the no-ground portion (6 × 18 mm2) of the module substrate of the AiSiP (total size 24 × 18 mm2). A parasitic shorted strip can also be added in the no-ground portion to double the operating bandwidth of the AiSiP. When mounted on the system ground plane of a wireless device, the AiSiP can provide a complete communication function, without the need of employing additional antennas in the wireless device. The proposed AiSiP is studied in the paper, and obtained results of the constructed prototype are presented. Effects of the system ground plane on the antenna performance of the AiSiP are also analyzed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2113–2117, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21868 [ABSTRACT FROM AUTHOR]

This paper describes a partially dielectric-loaded Vivaldi antenna (PDVA) structure that maintains ultra-wideband antenna characteristics over a bandwidth ratio greater than 25:1 so as to improve the impulse radiation characteristics for multisensor adaptive ground-penetrating Radar (GPR) operations. The PDVA is introduced for metal-detector-combined GPR head designs in order to avoid performance degradations based on the sensor interferences. It is shown that high gain, low input reflection, and signal-ringing levels over the wide operational bands are attainable for a PDVA with proper dielectric and absorber loadings. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 834–839, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21491 [ABSTRACT FROM AUTHOR]

In this paper, a new ultra-wideband slot antenna with a simplified feeding network is presented. This antenna is composed of a circular slot coupled to a circular patch fed with 50Ω microstrip line. A proper parametric investigation was carried out for optimization of the proposed structure. Simulations and measurements show that a large bandwidth from 2.13 to 11.11 GHz can be achieved, which represents a relative bandwidth of 136.4%. Furthermore, good agreement between simulated and experimental results is obtained. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 919–923, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21519 [ABSTRACT FROM AUTHOR]

The development of a small electrical antenna plays an important role in the rapidly growing mobile communication market. This paper presents the design of a novel small and wideband planar inverted F-antenna that simultaneously covers the GSM900/GPS/DCS1800/DCS1900/IMT2000/WLAN/DMB service bands. A very wide impedance-bandwidth characteristic was achieved by optimizing both the distance between the feed line and short strip and the width of a short strip. The commercial electromagnetic software CST Microwave Studio is used to design the structure. The maximum gains at the frequencies of 915, 1850, 2025, and 2450 MHz were 1.79, 3.56, 3.65, and 1.67 dBi, respectively. The overall radiation pattern is suitable for mobile application. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 947–950, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21528 [ABSTRACT FROM AUTHOR]

This paper presents a wideband variable gain amplifier (VGA) fabricated using the 0.18-μm CMOS process. An exponential CMOS triode transconductor scheme is proposed to achieve highly linear-in-dB characteristics of a VGA for ultra-wideband (UWB) systems. The proposed VGA achieves a linear-in-dB controllable gain range of 28.4 dB (7 to -21.4 dB) with a bandwidth of 1200 MHz, while drawing only 2.7 mA from a 1.8-V power supply. Measurements show a linear gain range with a linearity error of less than ±0.5 dB. P1dB varies from -8.5 to -6 dBm. The chip occupies an area of 0.2 × 0.2 mm2, excluding bond-pads. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 997–1000, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21546 [ABSTRACT FROM AUTHOR]

In this paper, a wideband dipole antenna with more than an octave of impedance bandwidth is presented. Enhancement is achieved by using an additional coplanar parasitic element and via optimization of the tapered feeding network. The prototype antenna demonstrates 87% impedance bandwidth (VSWR < 2), operating between 2.01 and 5.08 GHz. A sensitivity analysis reveals the possibility for a dual-band variant, covering both the 2.4- and 5.2-GHz WLAN operating bands, for use in IEEE 802.11a/b/g compliant systems. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 444–449, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21375 [ABSTRACT FROM AUTHOR]

The design of an FSS screen constructed using a circular fractal configuration to implement a broadband microwave absorber is presented in this paper. The decrement method is used to measure the microwave absorber's reflective response. The reflectivity representation recognizes the characterization of the microwave absorber. Simulation and measurement results are presented and analyzed. An FSS screen with a lotus-pod pattern is introduced in order to obtain a better bandwidth and absorption in this study. A broadband reflectivity response with 22% fractional bandwidth below -10 dB is presented. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 449–453, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21376 [ABSTRACT FROM AUTHOR]