Synthetic aperture radar (SAR) system has inherent constraints between high azimuth resolution and wide swath width. Achieving more phase center samples is one of the key solutions to resolve this limitation. By multiple N transmitting and N receiving channel concept, an increased resolution or a widened swath width could be obtained. In this paper, comprehensive analysis for shifting multiple-input multiple-output (MIMO) SAR system is presented. System resolution enhancement has been demonstrated based on the distributed target simulation by a factor of N compared to conventional displaced phase center antenna (DPCA) system.
This paper presents the design and development of Koch fractal dipole antenna for wearable applications at 450 MHz. Common jeans cotton is used as a flexible substrate material having a dielectric constant of 1.6 for the design and fabrication of the proposed antenna. Increasing the number of iterations increases the number of sections, which eventually results in 32% reduction in size. Size miniaturization is obtained using second iteration Koch geometry with the antenna bandwidth of 10%, and the return loss of -25 dB is achieved under the flat condition. The investigations are to characterize the antenna not only in flat condition, but also under different bendings and crumpling conditions. The proposed Koch fractal antenna is close to the proximity of the body, and the absorption of electromagnetic power on human body is also examined. It is found that the Specific Absorption rate (SAR) is much below a safety level of 0.119 W/kg and hence suitable for wearable applications.
A fully printable and conformal antenna array on a ﬂexible substrate with a new Left-Handed Transmission Line (LHTL) phase shifter based on a tunable Barium Strontium Titanate (BST)/polymer composite is proposed and computationally studied for radiation pattern correction and beam steering applications. First, the subject 1×4 rectangular patch antenna array is conﬁgured as a curved conformal antenna, with both convex and concave bending proﬁles, and the effects of bending on the performance are analyzed. The maximum gain of the simulated array is reduced from the ﬂat case level by 34.4% and 34.5% for convex and concave bending, respectively. A phase compensation technique utilizing the LHTL phase shifters with a coplanar design is used to improve the degraded radiation patterns of the conformal antennas. Simulations indicate that the gain of the bent antenna array can be improved by 63.8% and 68% for convex and concave bending, respectively. For the beam steering application, the proposed phase shifters with a microstrip design are used to steer the radiation beam of the antenna array, in planar conﬁguration, to both negative and positive scan angles, thus realizing a phased array antenna.
The resonant characteristics of superconducting rectangular microstrip patch antenna with a superstrate layer are investigated using a full-wave spectral analysis in conjunction with the complex resistive boundary condition. The complex surface impedance of superconducting patch is determined using London's equation and the two-fluid model of Gorter and Casimir. Numerical results using the full-wave analysis presented here are in excellent agreement with theoretical and experimental results available in the open literature. Numerical results show that the effect of the superstrate layer on the resonant frequency and half-power bandwidth of the superconducting rectangular patch is stronger than that of the structure without superstrate layer as both the thickness and permittivity of the superstrate increase. Finally, numerical results concerning the effects of the parameters of superstrate-substrate and superconducting patch on the antenna performance are also presented and discussed.
A compact multiband omnidirectional antenna for the reception of GNSS signals on artillery projectiles is designed in this paper. The proposed antenna consists of a metallic cone comprising a T-shaped monopole. It exhibits a broad bandwidth from 1.22 GHz to 1.28 GHz and from 1.44 GHz to 1.75 GHz, covering GPS L1, Galileo E2-L1-E1, GLONASS G1 and G2, CNSS B1 and B3. Measured results show that an omnidirectional radiation pattern is achieved, and the non-circularity in the azimuthal plane (xy-plane) is less than 2 dB for all the desired bands. Then the measured 6 dB beamwidth is about 110° in the presence of a finite 20 millimeters (mm) radius ground plane. Such an antenna has the potential to be easily used for small artillery projectiles.
This paper presents an alternate microwave imaging system that greatly reduces design and operation complexities compared to traditional imaging systems. At the heart of this novel system lies an electronically reconfigurable beam-scanning reflectarray antenna. The high tuning capability of the reflectarray provides us a broad steering range of ±60˚. The beam is steered across this range and the scattered field is recorded. The collected data are used for image reconstruction by means of the time reversal signal processing technique. Experimental results of the detection of various dielectric targets are presented.
A circular microstrip patch antenna design is proposed for applications that require suppression of surface waves and lateral waves. The proposed design is composed of a circular patch loaded with a single shorting pin on a grounded inhomogeneous dielectric substrate with a desired effective permittivity. The modal equation for the normalized resonance frequency of this design is solved numerically. Simulated and measured radiation patterns show that a good reduction of surface waves and lateral waves is achieved. A comparison between the present work and an alternative design in the literature is presented in this paper. The proposed design could find applications in large patch antenna arrays where mutual coupling needs to be eliminated and in high-precision global positioning system receivers where multipath interfering signals associated with low-angle reflection affect position accuracy.
In this paper, a compact multiple-input-multiple-output (MIMO) antenna is proposed for ultra wideband (UWB) communication. The UWB MIMO antenna consists of two identical monopole antenna elements with a comb-line structure on the ground plane to improve impedance matching and enhance isolation. Simulation and measurement have been analysed in terms of reflection coefficient, mutual coupling, dispersion diagram, radiation pattern, peak gain, efficiencyand envelope correlation coefficient. Results show that the antenna has an impedance bandwidth larger than 3.1-10.6 GHz, mutual coupling between the two ports lower than -25 dB and envelope correlation coefficient less than 0.001 across the UWB band. The proposed antenna has a compact size of 26×31 mm2. All the measured and calculated results show that the proposed UWB MIMO antenna is a good candidate for UWB MIMO systems.
In this paper, a new compact coplanar waveguide (CPW) ultrawideband (UWB) antenna with an electronically tunable notched band is proposed for an overlay onto cognitive radio (CR) systems. The proposed antenna utilized a rectangular microstrip resonator in the bottom layer to create a single notched band and to realize tunability and miniaturization using varactors. The center frequency of the notched band can be electronically tuned by changing the effective electrical length of the microstrip resonator, which is achieved by employing two varactor diodes at the resonator edges. Moreover, the simple biasing of the varactor diodes has a small effect on the antenna performance. Experimental results show that the proposed antenna can selectively have a band notch over a continuous operating band about 1.44 GHz from 4.77 to 6.21 GHz to prevent the interference to the primary users that are operating in this band such as the WLAN (5.15-5.35 GHz; 5.725-5.825 GHz) and the WiMAX (5.25-5.825 GHz). Good agreement is found between the simulated and the measured data.
In this paper, an ultra compact dual-band metamaterial antenna based on a new asymmetric generalized negative refractive index transmission line is introduced. The antenna is designed to support the 900 MHz GSM and 2400 RFID/WiFi bands. Moreover, the antenna size is only (15×20 mm2) which is only less than (0.08λg× 0.1λg) at the center frequency of the first resonance and (0.22λg× 0.29λg) at the center frequency of the second resonance. The theoretical design steps of the antenna are explained. The dual-band antenna design has been validated using equivalent circuit modelling, electromagnetic full wave simulations and practical measurement. The results illustrate that the antenna has the first resonance centred at 0.9 GHz and the second at 2.4 GHz with 15 dB return loss in the two bands. Good agreements among the circuit modelling, electromagnetic full wave simulation and practical measurements have been achieved.
Static charging of an aircraft surface can lead to electromagnetic disturbances on aircraft radio and avionic systems. This phenomenon is called Precipitation Static. Arc discharges are the main causes, and they often occur when there is a bonding defect on the surface of the aircraft. In order to find these bonding defects, often the whole aircraft has to be scanned. This paper presents a method that aims at reducing the time needed for the search of outer bonding issues. The system is composed of an instrumentation to be used in-flight, that measures the electromagnetic emissions of P-Static sources using several sensors placed on the surface of the aircraft. Then, given several signals measured from sensors and using a time domain location method based on delay estimation, it is possible to compute the source position. The method is validated on a simplified fuselage mock-up with satisfying location performance.
In this paper, a microstrip-fed hexagonal shape ultra-wideband (UWB) monopole antenna with triple band-notched characteristics is presented. The antenna consists of a microstrip feed line, a regular hexagonal shape radiation patch with a complementary split ring resonator (CSRR) and a pair of inverted T-shaped conductor-backed planes embedded in the antenna backside. Notched bands can be easily controlled by geometry parameters of the CSRR and conductor-backed planes. The simulated and measured results show that this monopole UWB antenna can offer an operation frequency from 2.93 GHz to 10.04 GHz with -10 dB return loss bandwidth, except three notched bands at 3.31-3.78 GHz, 5.33-5.77 GHz and 7.24-7.72 GHz for rejecting the WiMAX and downlink of X band satellite communication system signals. A good agreement between the measured and simulated results is observed. The proposed antenna provides broadband impedance matching, appropriate gain and stable radiation patterns over its operating bandwidth and can be used in wireless UWB applications.
In this paper, a new printed ultra-wideband (UWB) power divider with notched band using square ring multiple-mode resonator (SRMMR) is presented. The characteristics of the proposed SRMMR are investigated by using even- and odd-mode analysis. Then, the initial UWB performance is achieved by introducing SRMMR to the basic Wilkinson power divider. Finally, a pair of parallel coupled lines is embedded into the SRMMR to achieve a desired notched band inside the UWB passband. The central frequency and the bandwidth of the notched band can be easily controlled by the electrical length and coupling coefficient of the coupled lines. To validate the design concept, a novel printed UWB power divider with notched band centered at frequencies of 5.8 GHz is designed and measured. The simulated and measured results indicate that it has a low insertion loss and good return loss performance at all the three ports, and a high isolation between the two output ports across the UWB bandwidth from 3.1 to 10.6 GHz with a small size of 0.46λg×0.69λg, where λg is the guided wavelength at 6.85 GHz.
This work presents a compact rectenna based on printed on paper electronics. The rectenna is printed using mass production technique on an environmental-friendly and flexible paper substrate. Only one ink layer is used. The characterized paper substrates present minimum tangent losses of 0.08. It shows at most 40 times higher tangent loss than commercial substrates (Rogers Ultralam2000). A reduction of 50% of dielectric losses can be achieved by a good selection of the paper type; the selected paper substrate is a corrugated cardboard with 0.04 loss tangent value. The designed rectenna is based on two series-mounted SMS7630 Schottky diodes. Co-design technique has been used in order to integrate different blocks for additional loss reduction. The goal of our work is the use of a recyclable cardboard substrate with low-losses compared to classical paper substrate and high losses compared to commercial substrates. The printed on cardboard rectenna presents similar performances to a rectenna etched on commercial substrates. This device aims to convert high voltage levels (1V) at low power levels (-15 dBm) for self-sustainable devices. For our application, an electrochromic display is supplied for anti-counterfeiting purposes. When a smartphone operating on Wi-Fi mode is close, the printed rectenna exhibits 970 mV DC which is sufficient to turn on the electrochromic display.
A wide bandwidth folded V-shaped patch antenna with high gain and low cross polarization is presented. The proposed antenna is composed of a folded V-shaped patch, an H-shaped coupling slot cut in the ground plane and a feed line with a stub printed on the bottom layer of the grounded substrate. By folding the V-shaped metallic patch, the proposed antenna can achieve a low profile structure and good performance in radiation patterns. The antenna element and the antenna array operating at 2 GHz were fabricated and tested. The prototypes with the single element can achieve a -10 dB return loss bandwidth of 28.5% (1.65 to 2.2 GHz) and a stable gain of 8.6 dBi, while 1×2 arrays exhibit a bandwidth of 34.1% (1.58 to 2.23 GHz) and a stable gain of 11.5 dBi.
An anisotropic dielectric resonator antenna (ADRA) with uniaxial and biaxial permittivity tensors is characterized by using the dielectric waveguide model. An approximate formula for the Q factor of ADRA is derived. Then, it is shown that by certain conditions a wideband ADRA can be designed. Samples of simulation results are shown to demonstrate the capabilities of the proposed anisotropic technique for enhancing the bandwidth of ADRA. The proposed antenna is simulated by two full wave packages, Ansoft HFSS and CST Microwave Studio, and a good agreement is observed among the results.
Tracking multiple maneuvering targets for automotive radar is a vital issue. To this end, a novel DS-UKGMPHD algorithm which combines diagraph switching (DS), unscented Kalman (UK) filter and Gaussian mixture probability hypothesis density (GMPHD) filter is proposed in this paper. The algorithm is capable of tracking a varying number of target cars detected by automotive radar with nonlinear measurement models in a cluttered environment. In addition, variable structure is used to accommodate various target motions in real world. Simulation results demonstrate the superiority of the presented algorithm to IMM-UKGMPHD filter in terms of estimation accuracy of both number and states.
Frequency diverse array (FDA) uses a small frequency increment at each antenna element to get a range, angle and time dependent beam pattern. Although linear frequency offset is used in most radar systems, nonlinear frequency offset is also very useful for analyzing FDA radar. A logarithmic frequency offsets based FDA (log-FDA) removes the inherent periodicity of FDA beam pattern to get a single maxima in area of interest. Multiple input multiple output frequency diverse array (MIMO-FDA) radar is also presented recently to provide some improvements compared to FDA radar. In this paper, a new hybrid scheme is proposed in which each subarray of MIMO-FDA uses a variable logarithmic offset. The resultant system, called MIMO-log-FDA, uses not only a different logarithmic offset, but also unique waveform in each subarray. Different logarithmic offsets contributed in terms of getting more control on width of beampattern, while the different waveforms provide diversity, which can be exploited at the receiver of the proposed system. Some improvements in transmit beam patterns have been shown for MIMO-log-FDA, followed by detailed signal model for better estimation of target at the receiving side. Performance analysis is also done in terms of signal to interference plus noise ratio (SINR) and Cramer-Rao lower bound (CRLB). Simulation and results verify the effectiveness of proposed scheme by comparing it with Log-FDA and MIMO-FDA radar.
A new microwave lens antenna suitable for ultra-high frequency (UHF: 300 MHz-3 GHz) band applications is proposed. An improved bow-tie antenna and a planar metamaterial lens design is presented. 5 dB improvement in boresight gain and a directive radiation pattern is achieved with the lens. The application of the designed antenna is demonstrated in a ground penetrating radar (GPR) experiment. The size of the antenna is very compact compared to other antennas found in the literature used for similar applications.
A lossy filter with resistive coupling is proposed based on substrate integrated waveguide (SIW) resonators, where nonresonating nodes are not required to simplify the realization. The sensitivity analysis of S-parameter to the resistive coupling coefficient is carried out to determine the parameters of coupling structure and mounted resistors. When resistive couplings are added to the structure, the measured 0.2-dB passband bandwidth increases from 198 to 256 MHz, compared with the case without resistive couplings. At a sacrifice on the additional insertion loss of 1.1 dB, the passband flatness and selectivity are improved significantly. The lossy SIW filter can provide a smaller in-band insertion loss than the microstrip counterparts, because the unloaded Q-factor of SIW resonators is higher than that of microstrip resonators. Moreover, a simpler topology and a less insertion loss are obtained in the proposed resistively coupled SIW filter than those of the lossy filter synthesized with lossy coupling matrix. Excellent agreement between the simulated and measured results is achieved to demonstrate our idea.