Broadband Microstrip Research Articles

A Broadband Microstrip Antenna With Improved Gain for Noncontact Vital Sign Radar Detection

A 4.37 GHz broadband microstrip antenna with improved gain was designed and fabricated. Compared to a partial ground plane single-patch reference antenna, the proposed broadband antenna shows better directivity and improved gain performance. In addition, its radiation pattern was designed for a vital sign radar application. This antenna was implemented in a portable 4.46.7 GHz radar sensor, which can be used for noncontact vital sign detection for security or healthcare applications. The wide frequency tuning range allows the system to be tuned for an optimum transmission frequency.

Wideband microstrip antennas with sandwich substrate

A broadband microstrip antenna with low–high–low (sandwich) dielectric constant substrate combination using a microstrip line-via feed is presented for ultra-wideband applications. The proposed antenna consists of three dielectric substrates; low dielectric constant substrates that contain the microstrip feed line as well as parasitic patches and a high dielectric constant substrate that contains the driven patch. To achieve a large impedance bandwidth, parasitic patches and microstrip line-via combination feed to the driven patch in the multilayered microstrip antenna are used. The proposed antenna designed, fabricated and measured on the sandwich substrate. The antenna has measured 10 dB return loss bandwidth of 46.9% and directive gain >5.2 dBi at boresight across the impedance bandwidth. The total height of antenna is 5.77 mm or 0.077λo at 4 GHz.

Design of a compact broadband microstrip patch antenna with probe feeding for wireless applications

In this paper the design and development of a compact broadband probe-fed Microstrip patch antenna for bandwidth improvement and antenna size reduction in a single design is proposed. The well-known technique of effective substrate thickness increment is performed to improve the impedance bandwidth, whereas for size reduction the electrical length of the conducting patch has been increased. A compact probe-fed inverted U-shaped microstrip patch antenna with a W-shaped ground plane has been designed and the experimental results are presented.

Broadband Via-Free Microstrip Balun Using Metamaterial Transmission Lines

A novel metamaterial broadband microstrip balun design is proposed. The broadband balun consists of a pair of identical metamaterial transmission lines. In the odd mode, a virtual ground is formed between the symmetric plane. The odd mode is allowed while the even mode is rejected. No vias are required to realize the shunt inductors of the metamaterial lines, and no power divider is used. Baluns with good performance can be achieved. In this letter, two baluns are fabricated and measured. For the balun with seven units, the output amplitude difference is less than 0.7 dB, and the differential phase is 181deg plusmn 3deg from 1.6 to 3.6 GHz, while the input return loss is greater than 10 dB.

Analysis of a compact and broadband microstrip patch antenna

AbstractA broadband microstrip patch antenna with U‐shaped parasitic elements is proposed and analyzed using equivalent circuit theory concept. The effects of gap between the main patch and the U‐shaped parasitic elements, substrate thickness, and the feed point location are analyzed to obtain the optimum conditions for broadband operation of the antenna. The antenna shows an operational frequency band from 4.88 to 6.44 GHz with 28.36% bandwidth at center frequency 5.5 GHz. The radiation patterns of the proposed antenna are similar to that of a rectangular patch. The antenna shows 3‐dB beam width of 98.6° at lower resonance frequency whereas it is 77.6° at higher resonance frequency. The theoretical results are in good agreement with experimental results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2059–2063, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23573

Broadband bandpass filters using slotted resonators fed by interdigital coupled lines for improved upper stopband performances

This paper proposes new broadband microstrip bandpass filters based on slotted linear tapered-line resonator (SLTR) and slotted step impedance resonator (SSIR) structures for size reduction and improved stopband performances. A comprehensive treatment of slotted resonators and both ends of the resonator with interdigital coupled lines is described. The design concept is demonstrated by two filter examples including one with an SLTR and another one with an SSIR. These filters have not only compact size but also a wider upper stopband resulting from resonator bandstop characteristics. The simulated and experimental results of stopband performances are better than 15 dB for a frequency range up to 25 GHz.

A novel broadband and high-gain microstrip reflectarray antenna with variable polarization

This article proposes a new kind of microstrip reflectarray antenna, of which the polarization could be reconfigured among all the polarization states instead of some fixed states in a dual-or multi-polarized antenna. The mechanism for polarized variability is so simple that only mechanical rotation is needed. Theoretical analysis shows that the reflected polarization covers all states and that the dual-or multi-layered unit structure sandwiched with air-gaps can broaden the bandwidth efficiently. Moreover, it is demonstrated that adopting more elements can enhance antenna gain. With these advantageous features, this kind of antenna has the potential significance for engineering applications in radar, communication, etc. In this article, a complete theoretical analysis as well as a specific design sample is given to verify this method.

High Efficiency and Broadband Microstrip Leaky-Wave Antenna

A novel layout of leaky-wave antennas based on tapered design has been proposed and investigated. The new tapered leaky-wave antenna (LWA) was designed running a simple procedure which uses an FDTD code, and using a suitable metal walls down the centerline along the length of the antenna connecting the conductor strip and the ground plane, which allows to use only half of the structure, the adoption of a simple feeding, and the reduction of sidelobes. The good performance of this new tapered microstrip LWA, with reference to conventional uniform microstrip LWAs, is mainly the wider band of 33% for VSWR<2, higher gain (12 dBi), and higher efficiency (up to 85%). Furthermore, from the theoretical analysis we can see that, decreasing the relative dielectric constant of the substrate, the bandwidth of the leaky-wave antenna becomes much wider, improving its performance.

Miniaturized Dual-Mode Filter Using Fractal Slot and Snaky-Shape Spur-Line

In this paper, miniaturized dual-mode filters using Koch fractal slot and snaky-shape spur-line are proposed. Compared to conventional dual-mode bandpass filter (BPF), fractal slot and snaky-shape spur-line provides more current distribution distortions which improve the electrical length and realize a compact design. A size reduction of about 61.1% is obtained compared to the traditional design. In addition, the relative 3-dB bandwidth is improved by about 20.7% after adopting the second-order Koch fractal shape. This dual-mode BPF has a good prospect in compact and broad-band microstrip circuit applications.

A 4×1 L-probe fed Inverted Hybrid E-H Microstrip Patch Antenna Array for 3G Application

This paper presents a compact and broadband microstrip patch antenna array (BMPAA) with uniform linear array configuration of 4x1 element for 3G applications. The 4A—1 BMPAA was designed and developed by integrating new patch shape Hybrid E-H shape, L-probe feeding, inverted patch structure with air filled dielectric microstrip patch antenna (MPA) element. The array was constructed using two dielectric layer arrangement with a thick air-filled substrate sandwiched between a top-loaded dielectric substrate (RT 5880) with inverting radiating patch and a ground plane. The Lprobe fed inverted hybrid E-H (LIEH) shaped BMPAA achieves an impedance bandwidth of 17.32% referenced to the center frequency at 2.02 GHz (at VSWR ≤ 1.5), maximum achievable gain of 11.9±1dBi, and 23 dB crosspolarization level.

Design considerations of a broad band microstrip antenna with embedded negative capacitor loading

AbstractIn this article, effects of negative capacitor loading on the bandwidth (BW) and efficiency of a rectangular microstrip antenna (RMSA) have been investigated. The active negative capacitor is made of a field‐effect transistor that exhibits negative resistance as well as capacitance. It can, therefore, compensate the loss of an inductor having antenna. A single negative‐capacitor‐loaded RMSA gives broadband frequency operation with broadband radiation. A microstrip patch operating at 10.5 GHz having 12.22% BW has been utilized as a reference antenna. Theoretical results for the impedance and the radiation patterns have been presented. It is also shown that the impedance BW of the antenna has been enhanced by using active negative capacitance networks from 12.22% to 16.96%, respectively. In addition, it has been shown that active compensation significantly improves the radiation pattern. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2651–2656, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22806

Gradient-based adjoint-variable optimization of broadband microstrip antennas with mixed-order prism macroelements

This paper describes a new finite element method (FEM)-based adjoint-variable approach to design and optimization of planar microwave circuits using sensitivity analysis, with respect to small variations of their design parameters. The implementation is based on a specially developed class of mixed-order prismatic macroelements, suitable for an efficient analysis of planar microwave structures. Their use, combined with a simple probe feed model, not only reduces the overall computational effort but also facilitates a straightforward derivation of port parameter sensitivities. Explicit expressions are given for the adjoint solution and S-parameter sensitivity and the process is verified through the design and optimization of two slotted broadband microstrip patch antennas.

Microstrip antennas with loaded trapezoidal slots for broadband tactical wireless communications

AbstractIn this letter, a broadband microstrip antenna suitable for tactical wireless communication at 1.35–1.75 GHz was proposed by loading trapezoidal slots. Compared with rectangular slotted patch antennas, the proposed design achieved a smaller size and a larger bandwidth. In addition, due to more design parameters, better antenna performances can be obtained by optimizing these parameters. Simulated and measured results validate the proposed design. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1210–1212, 2007; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.22400

A broadband microstrip Marchand balun with vertical coupling structure

AbstractIn 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

Wideband Dual-Polarized Patch Antenna With Broadband Baluns

A pair of novel 180deg broadband microstrip baluns are used to feed a dual-polarized patch antenna. The 180deg broadband balun delivers equal amplitude power division and consistent 180deg (plusmn5deg) phase shifting over a wide bandwidth (>50%). We demonstrate that for a dual-polarized quadruple L-probe square patch antenna, the use of the proposed 180deg broadband balun pair, in place of a conventional 180deg narrowband balun pair, provides improved input port isolation and reduced H-plane cross-polarization levels over a wider frequency range, while maintaining low E-plane cross-polarization levels and stable E- and H-plane co-polarization patterns throughout the impedance passband

Broadband Microstrip Patch Antenna Fed by a Novel Coupling Device

Two broadband microstrip patch antennas are designed here. Both are fed by the CPW with an H-shape coupling slot which is modifled by the conversion idea. The former has a bandwidth of 26.5% and a gain of more than 8dBi in the operating frequency band, while the latter attain 40% impedance bandwidth and 20% gain bandwidth above 6dBi. All result data prove the validity of designed models. DOI: 10.2529/PIERS060904222938

Broadband microstrip branch-line coupler with defected ground structure

The design and measured performances of a broadband branch-line coupler are presented. The broadband coupler was designed by using a four-section branch line topology with a structure of the defected ground. Such a structure can make the impedance of the microstrip line much larger than that without defected structure, even using a normal PCB process. More than 231 Omega was easily achieved by such a defected structure. The measured performance of the broadband coupler agrees well with the results from simulation

A novel wideband microstrip‐fed elliptical slot array antenna for Ku‐band applications

AbstractThis study presents a broadband microstrip slot array structure with a novel feeding technique, which offers enhanced bandwidth and very low cross‐polarization levels, targeting the satellite reception application market in the Ku‐Band. The single element module and the antenna array formulations of two, four, and eight elements are examined, fabricated, and experimentally characterized. Details of the design procedure and experimental results are discussed. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1824–1828, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21791

A compact and broadband microstrip antenna design using a geometrical-methodology-based artificial neural network

A new artificial neural-network-based methodology for a microstrip antenna design was studied and presented. The methodology is applicable to DCS, GSM, WLL, WLAN, large band planar antennas, and fractals. In this paper, we present five applications of this methodology, three of which are applicable in the WLL, 802.11a, and 802.11b antenna standards. The two others are broadband designs with 500 MHz and 1 GHZ bandwidth, respectively. All the antennas radiate an end-fire beam, and have compact sizes of 29 mm /spl times/ 25 mm, 10 mm /spl times/ 13.5 mm, 10.3 mm /spl times/ 17.2 mm, 35 mm /spl times/ 25 mm, and 35 mm /spl times/ 25 mm, respectively.

MAMA: a new methodically designed broadband microstrip antenna using off-the-shelf components

The current paper proposes a new, simple, methodical approach to broadband microstrip antenna design. The approach relies on a reformulation of the antenna-design problem as an impedance-matching problem, in which the antenna is considered to be the matching device required to match the feed line to air. Thus, impedance-matching techniques, such as Chebyshev transformers and a Klopfenstein taper, are employed to determine the antenna parameters necessary to satisfy a set of specifications. Simulation results as well as measured results show that the proposed matched-to-air microstrip antennas (MAMAs) qualify as a new class of broadband microstrip antennas, which have the advantages of relying on a systematic approach (as opposed to the usual trial-and-error procedures that are now prevalent), as well as being very easy to fabricate, using inexpensive off-shelf components.