In this paper, two compact multi-layer four-way substrate integrated waveguide (SIW) power combiners/dividers operating at W-band are analyzed and demonstrated experimentally/numerically. Based on the double-layer SIW broadside slot directional coupler, a four-way power combiner/divider is proposed for the first time. And a four-layer four-way SIW power combiner/divider is demonstrated experimentally, by using the transition structure between high-performance multi-layer SIWs and rectangular waveguide. Both SIW power combiners/dividers show the high port-isolation, low loss, high efficiency, wide-band, and small lateral size.
In this paper, we report the design and evaluation of a compact 108-element base station antenna array for massive multi-input multi-output (MIMO) system using a 3-port multimode antenna as a unit element. Of these three ports, port 1 and port 2 have orthogonally polarized broadside radiation pattern with measured peak gain of 6.5 dBi and impedance bandwidth of 254 MHz (2.268 GHz-2.522 GHz) and 238 MHz (2.248 GHz-2.486 GHz), respectively, while port 3 has monopole-like radiation pattern having measured peak gain of 1.21 dBi and impedance bandwidth of 102 MHz (2.376 GHz-2.478 GHz). Mutual coupling among all the ports is kept as less than -14 dB. Design of 108 elements massive MIMO antenna array is evaluated as a base station antenna for multiuser urban street grid scenario in MIMO-OFDM downlink system, which is further modeled using Wireless World Initiative New Radio II (WINNER II) Channel models in MATLAB. Parameters like Singular value spread and Dirty Paper Coding (DPC) sum capacity was calculated and compared with i.i.d channel model. For 4 users case using same frequency and time resource, singular value spread and DPC sum capacity for presented antenna array converges to 7 dB and 11.6 bps/Hz at 10 dB SNR, respectively.
Design and development of a novel dual-band microstrip patch array antenna suitable for WLAN and WiMAX applications are presented. The proposed array configuration is obtained by employing two parasitic patches gap coupled to the driven elements of a single layer proximity fed 2x1 microstrip patch array configuration. The proposed dual-band array has the advantages of enhanced bandwidth and gain. The feed patches are excited by proximity feeding method and the parasitic patches are excited by gap-coupling. This microstrip patch array provides resonances at two frequencies of 2.584 GHz (2.412-2.629 GHz) and 3.508 GHz (3.469-3.541 GHz). This novel configuration has a measured gain of 8.51 dBi and 5.8 dBi in lower and upper bands with an impedance bandwidth of 8.16% and 2.05% respectively. Additionally, to enhance the front to back ratio at the upper resonant frequency, a metal plate is placed at the back side of the array antenna. This modified proximity fed gap coupled array provides directional radiation patterns with improved gains. Re-configurability in the form of beam steering is obtained in the modified array configuration by varying the air gap between the ground plane and metal plate. The simulated results are in good agreement with the experimental ones.
In this paper, a miniaturized dipole antenna operating at 100 MHz frequency for Ground Penetrating Radar (GPR) application is presented. A conventional dipole antenna length is half of its lowest operating frequency wavelength. As low frequency GPR system is vital for high depth penetration, the size of the antenna used reduces its handling and portability. Therefore, the technique of miniaturizing a dipole antenna by adding extra radiating arms is presented here. The antenna design and analysis is carried out using Advanced Digital System (ADS) software, and a network analyser is used to validate antenna performance. The antenna of 66.5 cm × 22 cm dimension, fabricated on an FR4 substrate exhibits a frequency resonance at 104 MHz with 8 MHz -10 dB bandwidth. The proposed antenna radiates in omnidirectional pattern and features 55 % reduction in length compared to a conventional dipole antenna of same frequency operation.
A novel uniplanar compact WLAN band-notched printed ultrawideband (UWB)-multiple-input-multiple-output (MIMO) antenna with dual polarization for high data-rate wireless communication is proposed. The antenna consists of two CPW-fed floral radiating elements along with a decoupling structure to ensure high isolation. The band notch at the WLAN frequency band is achieved by etching one single U-shaped slot on each antenna element. Results show that the proposed antenna gives impedance bandwidth from 2.7 GHz to 10.9 GHz with notched frequency band from 5.1 GHz to 5.9 GHz. The proposed antenna provides nearly omnidirectional radiation pattern, low envelope correction coefficient [ECC], moderate gain, efficiency, fidelity factor and pattern stability factor [PSF]. Furthermore, diversity characteristics such as mean effective gain [MEG] and diversity gain [DG] are also studied. Moreover, the time-domain analysis displays minimum dispersion to the radiated pulse. All these features make the proposed antenna a good candidate for future high data-rate wireless communication systems with polarization-diversity operation, where the challenge of multipath fading is a major concern.
In this paper, a development of compact wideband antenna for L-Band Applications is presented. The proposed antenna is developed based on Modified Sierpinski Based Fractal geometry for the antenna patch with additional meandered structure in the antenna transmission line. The designed antenna is printed on a 10 x 10 cm of substrate with a relative permittivity of 4.3 and thickness of 1.6 mm. The antenna is fed by a 50 Ω microstrip line. The proposed antenna is characterized both in numerical and experimental analysis. The antenna characteristics are analyzed in terms of return loss, bandwidth, antenna gain, radiation pattern and radiation efficiency. From the experimental analysis, the fabricated antenna exhibits reasonable agreement to numerical design. The proposed antenna has an operating frequency from 0.94 GHz to 2.25 GHz with the lowest return loss of -36dB and maximum gain around 5.49 dBi, as well as radiation efficiency of 97%, approximately.
This paper presents compact dual/tri-band bandpass filters (BPFs) with controllable frequency and high selectivity for WLAN applications. A stepped impedance resonator with a shorting stub and a uniform impedance resonator with an open stub are applied in the designs. Several techniques that can generate transmission zeros are combined, to improve the frequency selectivity. The resonators and the proposed filters are characterized by full-wave simulations. To validate the design strategies, a dual-band BPF centered at 2.4 GHz and 5.2 GHz was first designed. With a minor modification, a tri-band BPF centered at 2.4 GHz, 5.2 GHz and 5.8 GHz was then developed. Both simulations and measurements were carried out to demonstrate the effectiveness of the designs. Good agreements are achieved.
A compact triplet inline substrate integrated waveguide (SIW) bandpass filter is presented with sharp lower skirt and deep lower-stopband performance. The filter is composed of two SIW rectangular cavities and an embedded short-ended microstrip line on the top surface of two adjacent SIW cavities. A transmission zero can be generated by the cross coupling near the lower passband edge, which allows the filter implementation in inline with sharp lower skirt. Deep lower stopband performance is inherited from SIW. To validate the concept, a filter prototype with fractional bandwidth (FBW) of 4% at 5.75 GHz is designed, fabricated and measured. Good agreement can be obtained between the measured and simulated results.
This paper presents a compact, low-profile, wearable dual-band antenna operating in the Wireless WLAN band of 5.15~5.25 GHz and 5.72~5.83 GHz. The proposed antenna is composed of a planar monopole and underneath three by three array arrangement of Jerusalem Cross (JC) structure metasurface. The simulated results show that the integrated antenna express 4.09% and 4.14% impendence bandwidths, increased gain up to 7.9 dB and 8.2 dB, front to back (FB) ratio achieved to 20 dB and 18 dB at the two frequencies, respectively. The measured results agree well with simulations. In addition, the metasurface not only is equivalent to a ground plane for isolation, but also acts as the main radiator, which enables a great reduction in the specific absorption rate (SAR). Furthermore, because of a compact solution, the proposed integrated antenna can be a promising device for various wearable systems.
A low-profile dual-polarized omnidirectional antenna is presented. The antenna is a combination of a vertically-polarized (VP) antenna and a horizontally-polarized (HP) antenna. The VP antenna is composed of a circular ground plane, a cross-shaped metal patch with four shorted legs and a top-loading circular ring. The printed dipoles of the HP antenna are fed through a three-way power divider etched on an FR4 substrate. To maintain stable radiation and reflection characteristics, the HP feed coaxial cable is soldered on one patch of the VP antenna to reduce the parasitic current on the feed cable. The VP antenna covers the frequency bands for GSM/2G/3G/4G LTE, and the HP antenna works in an overlapping frequency bands for 3G and TD LTE communication systems with high isolation. The VP antenna achieves a wide bandwidth of 108% from 800 MHz to 2700 MHz, and its gains are larger than 2 dBi in 800~960 MHz band and greater than 4 dBi in 1710~2700 MHz band, respectively. The HP antenna works in the frequency band from 1700 MHz to 2700 MHz, and its gains are greater than 3 dBi. The proposed dual-polarized antenna is simulated, fabricated and measured. Measured results are in good agreement with the simulated ones.
A compact 2×2 dual-band MIMO antenna is proposed with polarization diversity technique for present wireless applications. The proposed design combines the horizontally and vertically polarized radiating elements. The effect of mutual coupling between radiating elements is reduced by partially stepped ground (PSG) and by the orthogonal placement of antenna elements. The whole configuration is designed over a substrate of size 70×70 mm2. The measured frequency bands extend from 2.408-2.776 GHz, and 4.96-5.64 GHz frequencies with SWR < 2. The measured isolation is more than 21 dB between adjacent and diagonal ports. The measured peak gains at 2.54 GHz, and 5.26 GHz resonant frequencies are 3.98 dBi and 4.13 dBi, respectively. The designed MIMO covers LTE bands (7/38/41), WLAN bands (2.4/5.2/5.5 GHz), and WiMAX band (2.5 GHz). The diversity performances in terms of peak gain, MEG, ECC, and directivity have also been reported.
Flexible substrates have been increasingly studied in recent years. This paper proposes natural rubber as a new substrate material for flexible antennas. In our work, prototype antennas were built using rubber formulated with different filler contents. Carbon black was used as the filler where its amount was varied to yield different dielectric properties. Prototype inset-feed microstrip patch antennas with outer dimensions 7.52 mm × 10.607 mm × 1.7 mm and copper as its conducting material were fabricated to operate at 2.45 GHz. The prototypes were measured and their performance analyzed in terms of the effects of filler content on Q, return loss and bending effects on their gain and radiation characteristics. The return loss and gain were found to be comparable to those built on existing synthetic substrates, but these new antennas offer an added feature of frequency-tunability by varying the filler content. Under bending conditions, these new antennas were also found to perform better than existing designs, showing less changes in their gain, frequency shift and beamwidth, in addition to less impedance mismatch when bent.
This paper proposes two rectangular ring planar monopole antennas for wideband and ultra-wideband applications. Simple planar rectangular rings are used to design the planar antennas. These rectangular rings are designed in a way to achieve the wideband operations. The operating frequency band ranges from 1.85 GHz to 4.95 GHz and 3.12 GHz to 14.15 GHz. The gain varies from 1.83 dBi to 2.89 dBi for rectangular ring wideband antenna and 1.89 dBi to 5.2 dBi for rectangular ring ultra-wideband antenna. The design approach and the results are discussed.
In this contribution, the On-body propagation measurements at 40 m underground mine gallery and their statistical analysis are presented. Monopole antennas were installed on the body in order to form three on-body channels, namely belt-chest, belt-wrist and belt-head. The channel parameters of a 2 × 2 Multiple-Input Multiple-Output (MIMO) On-body system are evaluated and compared to the single-input single-output (SISO) system parameters. It was shown that the RMS delay spread and capacity values of the MIMO channels are higher than those of the SISO channels. The average value of the Ricean K-factor shows little difference between the MIMO and SISO belt-chest measurements. The calculated capacity values for a constant signal to noise ratio (SNR) and those calculated at a constant transmitted power demonstrate that the propagation performance is significantly improved by using the MIMO compared to the conventional SISO scheme. Hence, MIMO technology is a suitable candidate for On-body underground communications.
Three horizontally-polarized (HP) omnidirectional antennas are proposed and discussed in this paper. The antennas are composed of 3, 4 or 5 printed dipoles with corresponding wideband 3-, 4- or 5-way feeding networks. The feeding networks are simple in structure and easy to be matched with the printed dipoles. All of the proposed antennas operate in the frequency band of 1.7-2.7 GHz, covering the DCS1800, WiFi2700 and 4G-LTE bands with reflection coefficients less than -15 dB. Effects of the number of the printed dipoles on omnidirectional characteristics are discussed. Crossed strips are applied to improve their cross-polarization performance. The proposed antennas are simulated, fabricated and measured. Both simulated and measured cross-polarization levels are lower than -15 dB from θ=60° to θ=120° conical cuts. The antennas demonstrate good omnidirectional patterns in the whole frequency band, which can be widely used for indoor 4G-LTE indoor distributed antenna system (DAS) applications.
Microwave induced thermo-acoustic tomography (MITAT) is a developing technique for biomedical applications, especially for early breast cancer detection. In this paper, impacts of short microwave pulse on thermo-acoustic (TA) signals are analyzed and verified through some experimental comparisons. In these experiments, short microwave pulses with widths of 10 ns and 500 ns are employed as radiation resources. TA signals generated from a cubic sample are analyzed in both time- and frequency-domain. A trapezoid sample is also performed for experimental comparing. Different from previous literature, the effects of rising edge of radiation microwave pulse have been intensively studied. Experimental results demonstrate that shorter rising edge duration conducts broader bandwidth of TA signal, which give rise to better spatial resolution for tomography imaging.
An X-band radiator as an open-ended waveguide with a hybrid dielectric insert is proposed. The insert is in the form of a parallelepiped, which fills the entire cross section of the waveguide and constitutes a Teflon matrix with local inhomogeneities in the form of dielectric cylinders with a different permittivity. The design allows for forming various near-field distributions and, hence, the radiator performance by means of definite combinations of the local inhomogeneities can be modified. A number of configurations in the location of air and quartz cylinders are investigted. The calculated and experimental results are in good agreement. The proposed approach to the near-field formation of the aperture antenna is promising, because the variety of possible configurations in the location of local inhomogeneities with different permittivity provides new opportunities in terms of designing both single radiators and antenna arrays.
For wideband common-mode noise suppression in high-speed differential signals, a low-cost compact filter is proposed and designed by etching two coupled C-slotlines on the ground plane. It is found that the bandwidth of the common-mode stopband over -10 dB is from 2.4 GHz to 6.35 GHz with no degradation of the differential-mode insertion loss and group delay within the wide common-mode stopband. In time domain, the differential signal eye diagram is not deteriorated as well. In addition, an equivalent circuit model is developed and provides a quickly prediction of the common-mode stopband. The results show a good consistency between the simulations and measurements.
This paper presents a compact 2.45 GHz single feed directional circularly polarized (CP) microstrip antenna for radio frequency identification (RFID) applications. The proposed antenna comprises a dodecagonal microstrip patch embedded with an irregular polygonal slot, fabricated on an FR4 substrate. Two antennas, one with right-handed circular polarization (RHCP) and the other with left-handed circular polarization (LHCP), both resonating at a frequency of 2.45 GHz are presented. The measurement results show a 3 dB axial ratio bandwidth of 5.5%, a 10 dB impedance bandwidth of 5.7% for both the antennas, a peak gain of 4.82 dBi for RHCP antenna and 4.67 dBi for LHCP antenna. In addition, the antennas provide symmetrical patterns with 88˚ half-power beam width. The overall size of the antenna is 50 mm × 50 mm × 1.6 mm and offers an area reduction of 21.17%.
A new design of dual-band L1/L2 GPS antenna is proposed. The antenna generates dual-band circularly polarized radiation by exciting a cross-slot and ring-slot of a concentric circular aperture using a proximity-coupled feed. Parametric studies show that the matching and axial ratio bandwidth of L1 (1.575 GHz) and L2 (1.227 GHz) bands can be independently tuned by alternating the ring radius and slot length. The range of frequency ratio and 3 dB center frequency can be highly adjusted by slot's parameters. The size of the antenna is 73 mm × 73 mm × 6.4 mm including the ground, corresponding to 0.29λ × 0.29λ × 0.026λ at 1.227 GHz.