Search

We propose a drone classification method for polarimetric radar, based on convolutional neural network (CNN) and image processing methods. The proposed method improves drone classification accuracy when the micro-Doppler signature is very weak by the aspect angle. To utilize received polarimetric signal, we propose a novel image structure for three-channel image classification CNN. To reduce the size of data from four different polarization while securing high classification accuracy, an image processing method and structure are introduced. The data set is prepared for a three type of drone, with a polarimetric Ku-band frequency modulated continuous wave (FMCW) radar system. Proposed method is tested and verified in an anechoic chamber environment for fast evaluation. A famous CNN structure, GoogLeNet, is used to evaluate the effect of the proposed radar preprocessing. The result showed that the proposed method improved the accuracy from 89.9% to 99.8%, compared with single polarized micro-Doppler image. We compared the result from the proposed method with conventional polarimetric radar image structure and achieved similar accuracy while having half of full polarimetric data.

Radiation leakage of a global positioning system (GPS) module was investigated for a drone detection system by measuring the attenuation effect and long-range detection on the outside of a building. The GPS module consisting of the radio frequency components is essential to control the flight of a drone. There is an unavoidable leakage in the GPS module during operation, and the leakage signal from the GPS module was analyzed and detected with a high-sensitivity receiver. To analyze the leakage from the GPS module during operation, we obtained the whole frequencies of leakage signals and the radiation pattern of a drone with the GPS module in an anechoic chamber. From the data, we measured the leakage signals in an outdoor space. Through outdoor measurement, it was confirmed that the theoretical attenuation effect was consistent with the measured value with a distance variation. Finally, the GPS leakage in the drone was measured up to 950 m with a high signal-to-noise ratio (SNR) of 25 dB.

Given the rapidly growing drone market, the development of drone detection radars has become highly important to prevent drones from damaging lives and property. Frequency-modulated continuous-wave (FMCW) radars have been frequently used for drone detection. Among the architectures of FMCW radar, a heterodyne architecture that involves different local oscillators and produces beat signals at the IF stage has often been chosen. The FMCW radar, however, has a chronic problem called leakage. In an earlier study, we proposed the stationary point concentration (SPC) technique to improve the signal-to-noise ratio (SNR) of small drones by reducing the increase in noise floor caused by leakage. We demonstrated that the proposed technique increases the SNR of small hovering drones in the 1-D power spectrum. In this article, we newly analyze the practical problems in the heterodyne FMCW radar system. One is the 2-D noise floor increase in the range-Doppler (r-D) map due to the leakage, and the other is unwanted Doppler shifts. Then, we propose an upgraded theory and realization method of the SPC technique for the detection of the small moving drone by improving the r-D map. We prove that the proposed method not only reduces the 2-D noise floor by mitigating the leakage but also removes the unwanted Doppler shifts by the phase calibration. Consequently, we show that the proposed method increases the SNR of the small moving drone and corrects its velocity information at the same time in the r-D map.

This paper introduces a sparse scene reconstruction algorithm for automobile frequency-modulated continuous-wave synthetic aperture radar (FMCW SAR) through scaled compressed sensing (CS). An FMCW radar leads to low manufacturing cost, compact realization, and low transmission power. An automobile SAR is more economical and easier to implement than typical SAR platforms (e.g., satellites and aircraft). We apply CS to randomly subsampled raw data of automobile FMCW SAR for sparse reconstruction. We exploit the fact that the velocity of an automobile is significantly lower than that of the SAR platforms, which leads to a vastly narrow bandwidth of an azimuth-matched filter in the azimuth compression of the range-Doppler algorithm (RDA). Low-frequency azimuth data have a fundamental effect on azimuth compression. We propose a new reconstruction scheme, scaled CS, which specializes in low-frequency information recovery for automobile SAR. The scheme is based on basis pursuit denoising (BPDN). A Ku-band FMCW SAR system is developed to verify the performance of the proposed algorithm. We mount our system on an automobile and collect FMCW SAR raw data in the stripmap mode with a van maintained a constant speed on a highway. The proposed reconstruction algorithm shows improved recovery performance for automobile FMCW SAR, which is validated by processing a high-resolution real SAR image.

A lossy ferrite core/dielectric shell structure effectively miniaturizes an axial-mode helical antenna (AM-HA) without sacrificing the antenna gain in the range of 2.85–3.45 GHz. Co2Z hexaferrite-glass composite was used as an inner core and acrylonitrile butadiene styrene as an outer shell. The volume of the AM-HA was reduced by 29% while maintaining realized gain of 9.0 dBic, compared to air-core AM-HA. The simulation also confirmed that further miniaturization of the AM-HA up to 43% is achievable with a slight decrease in realized gain from 9 to 8.7 dBic. The designed magnetic core/dielectric shell structure offers a vast selection of lossy ferrite for miniaturization of the AM-HA.

A novel electromagnetic (EM) lens with high gain, suppressed side-lobe level (SLL) and low profile is designed using thin planar metasurfaces. The proposed design consists of a source patch antenna and an EM lens based on two thin planar metasurfaces. The two thin metasurfaces with an air gap are placed at the focal distance H of about λ /2.25 above the source patch antenna. This configuration forms a thin planar lens in which the source patch antenna emitted quasi-spherical wave in order to transform into plane wave. The total size of source antenna and an EM lens is same. The miniaturised EM lens antenna faces high SLL, which can be reduced by maintaining the uniform transmission phase coefficient and tunable transmission amplitude coefficient of metasurface unit cells. By implementing this topology on metasurfaces, the SLL of the proposed EM lens can be reduced without affecting the boresight gain of source patch antenna. The measured results of the proposed EM lens achieve 7 dB gain enhancement at designed frequency (5.8 GHz) with the SLL suppression of -24 dB. The total volume of planar lens antenna is 1.17 λ × 1.17 λ × λ /2.25 mm 3 , which is very compact compared with other reported planar lens designs.

This paper presents a theoretical model of the rectangular-shaped microstrip patch antennas on liquid crystal (LC) substrates in order to accurately derive the resonant frequencies and radiation performances. The model is based on the solution of the mode matching about an LC loaded cavity. The calculation results of the theoretical model are compared with the experiment and simulation results. The discrepancy between calculation and simulation results is merely 2.7%. In addition, a tuning mechanism of the patch antenna on the LC substrate is verified depending on the strength of a biasing voltage. The calculated results of the theoretical model indicate that the resonant frequency is shifted toward lower direction and 3-dB beamwidth of radiation pattern increases as the bias voltage increases. Although the calculated maximum directivity decreases with the increment of voltage, the realized gain increases due to the radiation efficiency of the antenna.

We designed and fabricated a multiple-ferrite-cored patch antenna (MFC-PA) to suppress harmonic radiation over the frequency range of 1–10 GHz and obtain wide suppressing bandwidth. Its suppression performance was compared to those of the conventional PA, photonic bandgap PA (PBG-PA), and defected ground structure PA (DGS-PA). Simulated and measured results show that MFC-PA effectively suppresses harmonic radiation up to $5.6f_{0}$ , where $f_{0}$ is 0.9 GHz, while the harmonic radiation of PBG-PA and DGS-PA is suppressed up to $3f_{0}$ . It is suggested by the antenna performance simulation that MFC-PA can further suppress harmonic radiation up to $11f_{0}$ . In principle, the harmonic radiation of MFC-PA is suppressed by dissipating the unwanted signals in ferrite materials, whereas PBG-PA and DGS-PA suppress harmonic radiation by reflecting or redirecting unwanted signals, which is not desired. Ferrite loading is a unique approach to suppress any harmonic radiation.

Our laboratory has developed a drone detection radar that involves a mechanical scanning antenna. Radar and antenna systems that have mechanical scanning require an additional component called a rotary joint (RJ). The purpose of RJ in scanning assemblies is to provide an uninterrupted link between the antenna and the transceiver. In our system, antenna and transceiver are linearly polarized and use TE10 mode along the rectangular waveguide section. TE10 modes are asymmetric in nature making them incompatible with the rotating motion of the antenna. An RJ is presented with back-to-back mode transitions using symmetric modes along the circular waveguide and contactless branch line joint. The mode used along the circular waveguide for symmetry purpose is TM01. An I-type linear RJ topology is selected due to lack of space along the lateral directions and system configuration. The problem of antenna matching while scanning was solved at 14.0–14.5 GHz at Ku -band using single-channel linear RJ.

A performance comparison of $2 \times 2$ multiple-input multiple-output (MIMO) antenna arrays with different configurations and polarizations in a reverberation chamber (RC) is presented at the 28-GHz band. Eight types of antenna arrays are proposed according to different configurations and polarizations. The measured results of the antenna arrays show that they have similar antenna performance with respect to the same array size except for those concerning with the polarization. Based on these antenna arrays, we propose twelve cases of $2 \times 2$ MIMO antenna arrays with dual-separated polarizations between top and bottom side. A 28-GHz channel sounder and a vector network analyzer were used to measure complex channel transfer functions at the specific position of the rotating mode stirrer in the RC. The proposed MIMO antenna arrays were measured in the RC without and with absorbers. To clarify the channel performance for each case, a wideband channel capacity is calculated from the measured result.

This paper discusses a novel drone-based external radar calibration technique, which utilizes a metal sphere hanging from a drone. The advantages of drone-based calibration are introduced and applied to a dual intermediate-frequency frequency-modulation continuous-wave (FMCW) radar system, which was developed to detect a low radar cross section (RCS) target like a drone with high sensitivity. The developed radar system operates in 150-MHz bandwidth with a frequency sweeping time of $500~\mu \text{m}$ at Ku-band frequencies. A 75- $\Omega $ coaxial cable was utilized in the radar system to physically separate the transmitter (Tx) and receiver (Rx) modules for better isolation. The physical separation with a coaxial cable helps in reducing Tx leakage signal effect, which is a critical concern of typical FMCW radar system, and also it helps the proposed radar system to have higher sensitivity. The designed radar system is a wired system that is fully synchronized with an internal reference clock generator. Offset frequency and other compensation factors were calculated for the calibration of the radar system using a big size metal sphere hanging from a drone. We observed that the theoretical calculations using the standard radar equation and the measurement results on calibration are in good agreement with each other. Furthermore, the RCS value of a small size drone is also investigated using the calibrated radar system. The RCS value estimated for the drone was about −22 dBsm.

We report a simple wireless power charging (WPC) antenna system (50 mm $\times40$ mm $\times0.1$ mm) for use in simulating power transfer efficiency ( $\eta $ ) with and without ferrite and a metallic object (battery case), thereby identifying suitable magnetic parameters and ferrite sheet thickness. The simulation results suggest that magnetic loss tangent (tan $\delta _{\mu }$ ) and permeability ( $\mu '$ ) need to be less than 0.05 and higher than 125 at 13.56 MHz, respectively, to achieve at least 75% of the transfer efficiency ( $\eta _{\mathrm {max}}$ ) of the WPC antenna without ferrite and the metallic object. Accordingly, we have fabricated Ni x Zn0.85– x Cu0.15Fe2O4 (x = 0.32 – 0.38) spinel ferrites using a one-step sintering process and obtained relatively high $\mu '$ of 169 and low tan $\delta _{\mu }$ of 0.1 with a nickel (Ni) concentration of 0.38. This magnetic loss is still too high to achieve 75% of the $\eta _{\mathrm {max}}$ value. In order to further reduce the magnetic loss, a two-step sintering process was used. The two-step sintered Ni0.38Zn0.47Cu0.15Fe2O4 shows $\mu '$ of 132 and a tan $\delta _{\mu }$ of 0.03 at 13.56 MHz, respectively. Therefore, this ferrite meets criteria identified by the transfer efficiency simulation and is a good candidate for 13.56-MHz wireless power transfer charging antenna system. In addition, our designed WPC system is capable of evaluating other magnetic materials that are suitable for WPC antenna applications.

This paper presents a theoretical model of a cylindrical hybrid resonator antenna. The hybrid resonator consists of an annular ring ferrite and a cylindrical dielectric with a dc magnetic bias field, applied in direction parallel to the antenna height. The ${HE}_{11\delta }$ mode splitting behavior caused by tensor nature of the permeability of a biased ferrite is investigated. To validate the proposed approximate analysis, an experimental investigation of an antenna loaded with a biased ferrite is also presented. The presented theory is shown to demonstrate the measured results. The antenna is found to be used as frequency, bandwidth, and polarization tunable antenna. The operating frequency can be chosen in the range from 9.07 to 9.84 GHz. In addition, the bandwidth can be extended from 7.3% to 12.7%. The polarization can be switched from linear to circular. The features mentioned earlier can be achieved by applying the appropriate magnetic field due to the ${\mathbf {HE}}_{\mathbf {11\delta }}$ mode splitting behavior. The theoretical model, the design process, and the measured results are presented in detail. The antenna is also found to be capable of tuning the operating frequency as well as the frequency tuning range without changing the overall size of the resonator.

In human body communication (HBC), the human body is used as a medium for transmitting data between devices as a replacement for wired and wireless technologies. The human body functions as an antenna in the low-frequency band used by HBC. Owing to this antenna function, electromagnetic waves radiating from electronic devices or wireless services cause electromagnetic interference (EMI) in HBC devices. This paper addresses such EMI in HBC devices. The interference signal caused by EMI was measured while the human subject, who was using an HBC device, was exposed to a general EMI environment at multiple sites. Using the interference model obtained from the measured interference signals, bit-error-rate degradation caused by the interference signal was simulated. The interference model presented in this paper can be effectively used to achieve reliable data communication in various HBC devices.

This paper discusses a distributed frequency modulation continuous wave radar system. This K-band radar system has high sensitivity, linearity, and flatness to detect low-radar cross section targets and measure their range and velocity. To reduce the leakage between a transmitter and a receiver, the system uses not RF cables but fiber-optic links that have low distortion characteristics and low propagation loss. The transmitter and the receiver are each mounted on a designed fixture to reduce the ground reflections. In addition, they are located on different platforms to reduce the leakage signal flowing directly from the transmitter to the receiver. Measurements in terms of the range and the velocity of a small drone have been carried out to evaluate the proposed distributed radar system. The results show that we can clearly detect the small drone within a 500 m range, which demonstrates the high sensitivity of the system and high isolation between the transmitter and the receiver.

Left-hand and right-hand circularly polarized (LHCP and RHCP) substrate integrated waveguide (SIW) antenna arrays are presented at the 28-GHz band for millimeter-wave (mm-wave) applications. Two types of circularly polarized (CP) antenna elements are designed to achieve respective LHCP and RHCP performance. Eight-element LHCP and RHCP antenna arrays have been implemented with feeding networks and measured. Based on the measurement, the LHCP and RHCP antenna arrays have impedance bandwidths of 1.54 and 1.7 GHz within $| S_{\rm{11}}| , whereas 3-dB axial-ratio bandwidths are 1.1 and 1.3 GHz, respectively. Each of the fabricated LHCP and RHCP antenna arrays is accomplished with a gain up to 13.09 and 13.52 dBi. Most of the measured results are validated with the simulated ones. The proposed CP antenna arrays can provide low-cost, broadband characteristics, and high-gain radiation performance with CP properties for mm-wave applications.

A theoretical model of a cylindrical ferrite resonator antenna with a dc magnetic bias, applied in the direction parallel to the antenna height, is proposed. ${\mathrm {HE}}_{\mathrm {11\delta }}$ mode splitting behavior caused by tensor nature of the permeability of a biased ferrite is investigated. The proposed model is validated through an experimental investigation of the HE $_{{\mathrm {11\delta }}}$ mode antenna. This communication utilizes a Li-ferrite suitable for the antenna applications. The presented theory is shown to correlate well with the measured results. It is also found that HE $_{{\mathrm {11\delta }}}$ mode splitting behavior of the antenna involves frequency and polarization, and bandwidth tuning performances. Therefore, the antenna is a good candidate for a multifunctional antenna.

A novel substrate integrated waveguide (SIW) cavity backed slot antenna with low back radiation is proposed in this study. This newly proposed meta-mushroom antenna uses a SIW cavity to decrease the back radiation. It is fed by the SIW cavity backed slot and radiates by meta-mushroom structure. This antenna exhibits broadband characteristics due to the meta-mushroom structure and a bow-tie slot on the SIW. The back radiation of the proposed antenna is considerably diminished by the SIW cavity located at the back side maintaining high gain performance. After all, its front-to-back ratio is increased and maintained over 19.2 dB in the operating frequency band, 4.5–5.6 GHz. Full-wave simulation and experiments results of the proposed antenna are demonstrated.

As an alternative standard electromagnetic (EM) field generator, a 4-port TEM (transverse EM) cell can be used for an EM compatibility (EMC) emission and immunity test. However, unwanted EM fields generated in a TEM cell deteriorate the results and accuracy of critical EMC tests. A new method to suppress unwanted field components in a 4-port TEM cell is proposed. To reduce the unwanted EM field, the narrow slits in internal septa are inserted, which are transverse with respect to the direction of wave propagation. By introducing the slits, the 4-port TEM cell can provide improved standard EM field distribution with the much-lowered unwanted field component inside the usable test volume.

In this paper, a wide beam scanning high gain compact metasurface lens antenna for 5th generation mobile communication system operating at 28 GHz using a wide band transparent linear graded index metasurface lens is designed. First, a highly transmissive metamaterial unit cell with wide 3 dB transmission band of more than 10 GHz transmission bandwidth with maximum resonance at 27.5 GHz is designed. A graded index metasurface lens is designed by using modulated modified double circular ring resonator unit cell. The designed lens causes a gain enhancement of 5 dB in the broad side direction by placing over a microwave radiator operating at 28 GHz. The mechanical movement of linear graded index metasurface lens results in to wide beam steering in a conical plane of apex angle 60° with stable gain variation in the direction of + 30° to - 30° with maximum gain of 11.5 dBi and reduced side lobe levels.

In this paper, a dual beam high gain compact metasurface lens antenna for 5th generation mobile communication system operating at 28 GHz using a wide band transparent metasurface is designed. First, a single layer thin highly transmissive metasurface lens with wide 3 dB transmission band of more than 10 GHz transmission bandwidth with maximum resonance at 27.5 GHz is designed. This single layer MS lens is used to achieve gain enhancement of about 5 dB in the broad side direction by placing over a microwave radiator operating at 28 GHz. A dual beam high gain antenna is designed by placing a double layer stacked same metasurface lens on the top of radiator resulting in to broad side gain of 13.5 dBi with gain enhancement of about 7 dB in the direction of ± 10° at 28 GHz.

A transmitting planar electromagnetic (EM) lens using frequency-selective surface (FSS) for millimeter-wave (mm-wave) communication is presented. The proposed EM lens composed of numerous FSS unit cells on a dielectric sheet. The topology of each cascaded FSS unit cell is based on sub-wavelength high-pass filters distributed over a planar surface. The planar lens design has a low-profile with a thickness of 0.32λo and FSS has a dimension of 0.42λ o x 0.42λ o mm2, (λ o =28 GHz). Planar lens antenna is placed about 20 mm of focal distance from a mm-wave probe antenna as a feeding source. The results shows that the proposed planar lens successfully transformed emitted quasi spherical waves to plan waves.

Human body communication (HBC) is a new technology for mobile and wearable devices operating over body area networks. In HBC, the body is used as a medium for transmitting data between devices to replace wired and wireless technologies. This study examines the bit error rate (BER) degradation experienced by HBC systems under the presence of co-channel interference. A degradation model is proposed to estimate the change in BER, and a selective simulation method is proposed to obtain the BER performance with a small exceedance probability and a small number of BER samples.

A low side-lobe substrate-integrated-waveguide (SIW) antenna array is presented at the 28-GHz band using broadband unequal feeding network for millimeter-wave (mm-wave) handset devices. The ground-plane size of the proposed antenna is fixed to half of the size of the Samsung Galaxy Note 4. The antenna array has been implemented with a multilayer structure created by stacking three substrates and a copper plate. An 8-way SIW feeding network with broadband 4-stage T-junction dividers and a cavity-backed antenna are investigated to obtain broadband performance. The proposed unequal T-junction dividers with phase compensation are introduced and designed for various output ratios. Applying Taylor beam-pattern synthesis in the 8-way SIW feeding network, low side-lobe performance is achieved. The measured result of the fabricated antenna has 2.3 GHz bandwidth within $\text{S}_11\,{ . The fabricated antenna can be performed with a gain up to 13.97 dBi with a low cross-polarization and symmetrical fan beam radiation patterns with low side-lobe levels. Most of the measured results are validated with the simulated results. The proposed antenna array provides low cost, broadband performance, and good radiation performances with low side-lobe levels for mm-wave handset devices.

In human body communication (HBC), the human body is used as a medium for transmitting data between devices in order to replace wired and wireless technologies. This paper presents the measurement results on the transmission properties of an HBC channel and an impulse response model for the HBC channel. The HBC channel was measured with respect to multiple subjects, and the channel parameters were then obtained to analyze the subject dependency of the HBC channel. The HBC channel was modeled using impulse responses that were obtained from the measured channels. The measurement results and the impulse response model can be effectively used to estimate the performance of HBC devices, which is significantly influenced by an HBC channel.

In this letter, a multiband full-metal-rimmed antenna covering 10 frequency bands for personal wireless communication terminals is presented. The design antenna is based on simple and effective techniques that are used for metal-rimmed smartphone applications. The proposed antenna with full metal rim is designed on RO4350B substrate within the volume of 130 × 70 × 5 mm3. We employed RO4350B substrate with inserted vias as metal rim with height of 5 mm, which surrounds the inner circuit board. The circuit board substrate has a ground plane, which is connected to the metal rim via extended substrate patch. This connection divides the rim into two metal rim strips. The combination of these two strips allows the design to operate on 10 bands. Performing perturbation on the ground plane further adds more operating bands and makes the design an excellent candidate for multiband operation. The designed antenna can be used to serve on GSM850/900, GPS, DCS, PCS, UMTS, WiBro at 2.35 GHz, Bluetooth, ISM, SDM-B at 2.65 GHz, WiMAX at 3.5 GHz, and C-band at 4 GHz wireless communication bands. A prototype antenna was fabricated and tested for input reflection coefficient, radiation performances, antenna gain, and efficiency. The measured and simulated results have been presented and discussed.

A novel microstrip patch antenna is proposed for automotive application. The antenna design has been investigated through both the parametric study and the demonstration of surface currents on the antenna structure. The surface currents related to the co-polarisation increased, and those related to the cross-polarisation is reduced by attaching shorted parasitic element. The four types of single antenna are designed to compare of gain and cross-polarisation level. The cross-polarisation level of proposed antenna has been reduced by 5.9 dB compared with the rhombic antenna. The rhombic array antenna and proposed array antenna were fabricated and tested for input reflection coefficient and radiation performance. The measured and simulated results have been presented and discussed.

Recently, as the drones have become smaller and smarter, they are emerging as new threats to the military and the public. To prevent the threats, the development of the radar to detect the small drones is needed. The frequency modulated continuous wave (FMCW) radar is one of the radar types for the drone detection. The heterodyne architecture for the FMCW radar is often applied to resolve the dc offset problem. However, the leakage from a transmitter into a receiver, the notorious problem of the FMCW radar, is still a challenging problem. Especially, the phase noise of the leakage increases the noise floor and deteriorates the signal to noise ratio. In order to mitigate this problem, in this paper, the stationary point concentration technique is proposed. Without additional hardware, the proposed technique can be implemented through frequency planning and digital signal processing. The results show that the proposed technique significantly lowers the noise floor over the desired range domain., Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible. arXiv admin note: text overlap with arXiv:1807.06324

This paper proposes a reverberation chamber structure consisting of new reflectors and mode stirrers for electromagnetic compatibility and wireless terminal measurements. The key design considerations for them are determined through a reasonable approach to analyze the eigenmode for a reverberation chamber and the standard deviation of its working volume based on 3D simulation. The final designs are expected to improve the standard deviation performance of the initial structure of the reverberation chamber and provide a better mode stirring environment. The results measured in the fabricated chamber demonstrate that these predictions are clearly realized. The results satisfy the main requirements of this paper, which are defined in consideration of the specifications of commercial reverberation chamber products. Therefore, the reverberation chamber of this paper is expected to be useful for performance measurement and evaluation of commercial wireless terminals. To verify this logical approach to obtain a good design and its results, the results measured in the actual fabricated reverberation chamber are described along with analytical and computational results.

Human body communication (HBC) is being recognized as a new communication technology for mobile and wearable devices in a body area network (BAN). This paper presents co-channel interference experienced by HBC supporting the physical layer in the IEEE 802.15.6 BAN standard. To analyze the co-channel interference, a co-channel interference model is introduced, and spacedomain and time-domain parameters representing an interference environment are generated using the cochannel interference model. A new signal-to-interference ratio (SIR) parameter depending on the peak amplitudes of the data signals causing co-channel interference is defined; co-channel interference can be easily analyzed and modelled using the newly defined SIR. The BER degradation model derived using the co-channel interference model and SIR in this paper can be effectively used to estimate the performance.

A feasibility study on the adoption of human body communication (HBC) for medical service is presented. The electrical specifications of HBC for medical service were reviewed. The ratio of the leakage current into the heart to the output current of a capsule-type transmitter and the propagation loss in the channel were simulated using an anatomical body model. The in-body to on-body channel loss for HBC was provided by electromagnetic simulation from the capsule-type transmitter in the stomach to receiving electrodes on the abdominal region. An analog front end with a sensitivity of 37 μVpp was developed, which showed an improvement of 21 dB against the best report. The 14 mm × 26 mm capsule-type transmitter was implemented, and preclinical experiment was conducted using a live pig. The proposed system successfully transferred data from the capsule-type transmitter in a stomach to the electrodes on the butt and the low jaw of the pig at a high rate of 2 Mb/s at a distance of 90 cm without packet error.

A novel antenna with both horizontal and vertical polarizations is proposed for 1.7–2.1 GHz LTE band small cell base stations. Horizontal polarization is achieved by using the Vivaldi antennas at the main PCB board in azimuth plane, whereas the vertical polarization is obtained using the rectangular monopole with curved corners in proximity of the horizontal elements. A prototype antenna associated with 8-elements (four horizontal and four vertical) is fabricated on the FR4 substrate with the thickness of 0.2 cm and 0.12 cm for Vivaldi and monopole antennas, respectively. Experimental results have validated the design procedure of the antenna with a volume of 14 $\times $ 14 $\times $ 4.5 cm $^{3}$ and indicated the realization of the requirements for the small cell base station applications.

This paper presents the improved isolation property of the signals among transmitter and receiver antennas. The separation wall is laid at the center of the antennas to improve the isolation level between them. The introduced separation wall has serrated edges mounted on three sides, i.e., top, left and right sides. These mounted serrated edges are implemented to reduce the diffraction which may occur due to the linear edge of the wall. The Fresnel diffraction problem has been solved using analytical method in order to get the optimized structure of the serration. The Fresnel diffraction patterns due to different sizes of the serration are obtained, and their relative powers are compared to each other. The implemented antenna system with the serration wall is composed of corrugated feed horn, orthogonal mode transducer, and offset dual-reflector parabolic antennas. The effect of serration is well demonstrated by the measurement of isolation level of the antenna system. The measured results show that the serrated edges enhanced the isolation property among transmitter and receiver antennas.

In this letter, an empirical channel model for human body communication (HBC) is presented based upon impulse response. For a channel model over a wide range of frequencies between 5 and 80 MHz, the amplitude of an impulse response is modeled with a random variable at each sampling point; the random variable is found using empirically obtained impulse responses with respect to multiple subjects of 70 human subjects. This empirical channel model is obtained when a signal transmitter and receiver are located on opposite hands. However, it provides a practical way to estimate the performance of HBC systems within an environment of multiple users and various devices.

A new broadband electromagnetic wave absorber based on a periodic surface and a method to increase its absorption bandwidth is proposed. The proposed absorber structure shows broadband characteristics, and its bandwidth is improved by generating additional resonances through a reasonable approach. To provide an understanding of the logical design procedure, an analytical method to determine the sheet resistance and new equivalent circuit models for analysing the impedance are both presented. From the analysis, it is shown that the exact range of the sheet resistance corresponding to the desired absorption level can be efficiently estimated for the resonance of the structure. For the verification of this approach to obtain an efficient design, as well as the functionality of both the absorber and the proposed method, experimental results are demonstrated along with analytical and computational results. The final measured results using the proposed method show a broadband reflectivity response, with a fractional bandwidth of approximately 93% below −10 dB and a bandwidth increase of 17%.

This article investigates the slotted bow-tie dual-polarization antenna with achieving the wide band. The proposed antenna consists of upper antenna and lower antenna in one PCB substrate. This antenna achieves a −10 dB return loss within the operating band of 1.6–2.3 GHz, which has a 700 MHz bandwidth. Isolation between antenna 1 and antenna 2 is about −30 dB within the operating frequency band. Antenna 1 and 2's gains are above 8 dBi in the entire frequency bandwidth. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:22–26, 2015

This article proposes a new design approach to an ultracompact composite right-/left-handed transmission line (CRLH-TL) bandpass filter with good passband and very broad stopband performances. In order to reduce the size, a series connection of the interdigital capacitor and shorted spiral inductor for realizing CRLH-TL is adopted and optimized to create the target Terrestrial-Digital Multimedia Broadcasting (T-DMB, 174–216 MHz) bandpass filtering. T-DMB was developed in South Korea. The results of a Bloch impedance analysis suggest that the proposed approach generates good impedance matching. The proposed filter has overall dimensions of λg/19 by λg/34 in terms of a center frequency of 180 MHz, a 3 dB fractional bandwidth of over 28%, an insertion loss of much lower than 2 dB, and a good return loss performance in the predicted and measured results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:694–697, 2016

An investigation of a novel cylindrical dielectric resonator antenna (DRA) configuration has been carried out. It is shown that two resonances including the full- and half-cylindrical HE(11δ)-like modes can coexist simultaneously at different frequencies by placing a metallic post array in the resonator. Moreover, compared with the conventional HE(11δ) mode cylindrical DRA having the same size, the proposed antenna operates in lower frequency band and shows improved bandwidth. The experimental results including the return loss and the radiation patterns are demonstrated.

This paper proposes a new down-conversion method to attenuate leakage signal in frequency modulated continuous wave (FMCW) radar. The proposed method reduces the effect of phase noise in the leakage signal. It can be simply realized through digital signal processing without additional hardware. Specifications of practical FMCW radar and the phase noise which is bad enough were assumed and simulations in these conditions were performed. Power spectral density (PSD) results show that while a target signal is buried by the phase noise tail of the leakage signal, the proposed method detects the target signal by attenuating the tail.

A theoretical model of a cylindrical ferrite resonator with a DC magnetic bias, applied in the direction parallel to the antenna height, is proposed HE 11δ mode splitting behavior caused by tensor nature of the permeability of a biased ferrite is investigated. Calculation results of the proposed model are analyzed to verify the mode splitting phenomenon.

In this letter, we present a multiframe L-slot planar dipole loaded with a single microstripline for multiband antenna systems. The multiband is achieved by creating a multiframe L-slot on a host dipole and also by loading the host dipole antenna with a single microstripline to generate a couple of shunts and series of capacitive gaps with an inductive strip, eventually forming $LC$ -like resonators. The antenna supports several wireless communication bands including: LTE bands at $1.7 \sim 1.8$ and $2.3 \sim 2.6~\hbox{GHz}$ ; WLAN bands at $2.4 \sim 2.5$ , 5.2, and 5.8 GHz; WiBro/WiMAX bands at $3 \sim 4~\hbox{GHz}$ . In addition, to validate the multiband behaviors, we also proposed a simple equivalent circuit for the designed antenna in which biconical transmission lines were adopted to model the host dipole sections. The simulation, fabrication, and measurement of the proposed antenna were implemented. As a result, its reflection coefficients $\vert { S}_{11}\vert$ were found to be better than ${-}$ 7 dB for most operating frequencies along with a sufficiently large bandwidth and good radiation patterns.

In this study, a quad-band folded slot antenna with a monopole feed line embedded in a conductive housing structure (the LCD bracket of a mobile phone) is proposed. The performance of the proposed antenna is evaluated through simulation and measurement, demonstrating that it can provide total radiation e-ciencies of more than 40% in the EGSM900, DCS, PCS, and WCDMA1 bands. Over these four bands, the total radiated power (TRP) of a prototype mobile phone using the antenna is 28.5, 27.1, 27.5, and 21dBm, respectively, while the total isotropic sensitivity (TIS) is 102.7, 104.3, 103.8, and 107.3dBm, respectively; all of these values satisfy Cellular Telecommunication and Internet Association (CTIA) requirements for over-the-area-(OTA) testing standards. The radiation performance of the proposed antenna in the calling mode is tested and shown to be within satisfactory limits; similarly, the speciflc absorption rates (SARs) of the prototype mobile phone are also found to be within standard SAR limits.

A compact multiband internal antenna covering LTE/GSM/GPS/DCS/PCS/UMTS bands (748-960 and 1575.42-2690 MHz) is presented for mobile terminals. The antenna combines a coupled-fed scheme and a magneto-dielectric material, which has low loss properties (magnetic loss tangent ) up to 3 GHz, thereby achieving not only reduced antenna size but also improved bandwidth. In addition, a T-shaped monopole feeding line generating parasitic capacitance is applied to the proposed antenna. It plays an important role to shift the resonances, especially in the low band. The overall size of the antenna is only 35 ×15 ×4 mm 3 , corresponding to 0.0875λ0 ×0.0375 λ0 ×0.01 λ0 ( λ0 is the wavelength at 750 MHz). The design process and the measured results of the proposed antenna are presented in detail.

A miniaturized microstrip-to-coplanar strip transition and its antenna application are presented in this letter. A composite right/left-handed transmission line and planar artificial transmission lines are used to design the transition in the 2.4-GHz band and to balance the output of the transition over a wider frequency range. In addition, the occupied area of the transition is only 0.087λg 2 . The 3-dB back-to-back insertion loss bandwidth is around 84%. Based on the proposed transition, a quasi-Yagi antenna is demonstrated. The impedance bandwidth is 30.3%. The antenna offers excellent endfire radiation performance. The maximum gain and front-to-back ratio are 5.1 dBi and 21 dB, respectively, at the endfire direction in the operating band. The design process and the measured results of the proposed design are presented in detail.

A null-filling antenna for automotive radar is investigated using the genetic algorithm. The single column of the proposed antenna consists of four gap-coupled antenna elements and 14 direct-coupled antenna elements. The radiating elements are inclined 45 ° from the feedline. The proposed antenna has 19.67 dBi gain with a -20.19-dB sidelobe level in the elevation and a -25.08-dB sidelobe level in the azimuth direction. The blind zone is reduced from 19.03 to 2.38 m using the proposed antenna for sensing the obstacle. The proposed antenna is a good solution for both short- and long-range automotive radar.