We have previously proposed an indoor monitoring and security system with an array sensor. The array sensor has some advantages, such as low privacy concern, easy installation with low cost, and wide detection range. Our study is different from the previously proposed classification method for array sensor, which uses a threshold to classify only two states for intrusion detection: nothing and something happening. This paper describes a novel state classification method based on array signal processing with a machine learning algorithm. The proposed method uses eigenvector and eigenvalue spanning the signal subspace as features, obtained from the array sensor, and assisted by multiclass support vector machines (SVMs) to classify various states of a human being or an object. The experimental results show that our proposed method can provide high classification accuracy and robustness, which is very useful for monitoring and surveillance applications.

A one-dimensional ad hoc network with a single active source–destination pair is analyzed in terms of transport capacity, where each node uses multiple antennas. The analysis is based on using a multi-hop opportunistic routing transmission in the presence of fading. Specifically, the lower and upper bounds on the transport capacity are derived and their scaling law is analyzed as the node density, λ, is assumed to be infinitely large. The lower and upper bounds are shown to have the same scaling (ln λ)1/α, where α denotes the path-loss exponent. We also show that using multiple antennas at each node does not fundamentally change the scaling law.

This paper describes very compact MIC magic-Ts and their integration with planar array antennas to realize the advanced antenna modules. The orthogonal transmission modes are effectively used to arrange the preferable port layout of magic-Ts. This flexible port layout of magic-Ts is a practical feature for integration with planar array antennas. The integration of magic-Ts and planar array antennas can easily create advanced functions. A couple of array antennas based on the integration advantages are introduced to materialize this technical concept. This integration approach is of big worth to originate various kinds of advanced antennas and the wireless modules in the ubiquitous society.

This paper investigates the use of cooperative spectrum sensing (CSS) to detect primary user (PU) signals during spectrum sharing between the PU and the secondary user (SU). In particular, we employ a variant of CSS (which achieves space diversity), called weighted gain combining CSS (W-CSS), which has the potential to achieve increased diversity gain and enhance detection performance. In a typical W-CSS system, the SU needs to obtain the PU signal power information in order to set the proper weight value. However, as it is hard for the SU to ascertain whether the PU is present or absent, this is difficult to obtain. To address this problem, a PU signal power estimation algorithm is introduced. In addition, we also analyze the statistics of the estimator and derive the detection probability of the W-CSS when the PU signal power estimation algorithm is applied. The analysis and related simulation results reveal that the detection probability of the proposed W-CSS under time-variant Rayleigh fading asymptotically approaches the detection probability in an additive white Gaussian noise channel as the number of antennas is increased. This also follows results from our Monte Carlo simulations, showing that multiple antenna elements could suppress the effect of Rayleigh fading. In short, the accuracy of the estimation algorithm is affected by channel variation (especially in the case of fast Rayleigh fading). Hence, to address this problem, we employ multiple antenna elements with a square-law combining energy detector in the W-CSS.

This paper presents a simple 3-D array configuration for high-resolution 2-D Direction-Of-Arrival (DOA) estimation. Planar array structures like Uniform Rectangular Array (URA) or Uniform Circular Array (UCA) often well estimate azimuth angle but cannot well estimate elevation angle because of short antenna aperture in elevation direction. One may put more number of array elements to improve elevation angle estimation accuracy, however it will require very large hardware and software cost. This paper presents a simple 3-D array structure for high-resolution 2-D DOA estimation only by modifying the height of some array elements in a planar array. Based on the analysis of Cramer-Rao Lower Bound (CRLB) formulation and its dependency on the height of array elements, we develop a simple 3-D array structure which improves elevation angle estimation accuracy while preserving azimuth angle estimation accuracy.

A folded monopole antenna fed by a CPW-to-trident transition feeder for compact wireless USB dongle devices is proposed. The antenna's dimensions are 1644.83.5 mm3, so it is suitable for low-profile wireless USB dongles. The proposed, compact monopole antenna resonates from 2.28 GHz to 10.8 GHz; hence, it can cover all wireless bands including WiBro (2.3–2.4 GHz), Bluetooth (2.4–2.484 GHz), WiMAX (2.5–2.7 GHz and 3.4–3.6 GHz), satellite DMB (2.605–2.655 GHz), 802.11b/g/a WLAN (2.4–2.485 GHz and 5.15–5.825 GHz), and UWB (3.1–10.6 GHz). A fabricated antenna is tested on a laptop to investigate the effects of the keypad and LCD screen on the resonant frequency and radiation pattern. The measured average gain of the fabricated antenna ranges from -2.76 dBi to 0.72 dBi.

This letter proposes a monopole multi-sector antenna with dielectric cylinder, and shows some results of simulations that examined the antenna characteristics. The dependency of radiation characteristics on relative permittivity εr shows the lens effect with increase of εr. Furthermore, the characteristics of the proposed antenna are improved by optimizing the termination conditions at the quiescent antennas. The backlobe level is lower than -10 dB. Also, the vertical HPBW and the conical HPBW are around 70.5° and 63.4°, respectively. The optimization improved the actual gain by 2 dB. It is found that the diameter of the proposed antenna is 1/3rd that of the conventional one.

Slotted-waveguide array antennas are attractive because of their low-loss characteristics at high frequencies. Several types of slotted arrays whose polarization angles are inclined to the waveguide axis have been reported. In this paper, we propose a new type of slot array antenna on a rectangular coaxial line for minimizing the waveguide width. As opposed to a conventional waveguide, there is no “cut-off” concept in our proposal because the coaxial line is a transverse electromagnetic (TEM) line. Therefore it is possible to guide the wave even if the diameter of the line is much smaller than that of the waveguide. Moreover, the proposed antenna is a resonant slot array antenna that is based on standing-wave excitation and is thus different from traveling-wave antennas (such as a leaky coaxial cable (LCX)).

In this letter, a post-detection signal to noise ratio (SNR) is considered for transmit antenna selection, when a sorted QR decomposition (SQRD) algorithm is used for signal detection in spatial multiplexing (SM) ultra-wideband (UWB) multiple input multiple output systems. The post-detection SNR expression is obtained using a QR factorization algorithm based on a sorted Gram-Schmidt process. The employed antenna selection criterion is to utilize the largest minimum post-detection SNR value. It is shown via simulations that the antenna selection significantly enhances the BER performance of the SQRD-based SM UWB systems on a log-normal multipath fading channel.

This paper presents the basic characteristics of a beam tilting slot antenna element whose forced resonance is realized by reactance loading; its structure complements that of a dipole antenna element. The radiation pattern is tilted using a properly determined driving point position; a single loading reactance is used to obtain the forced resonance without great changes in the tilt angle. Numerical results show that the reactance element needs to be loaded near the driving point in order to obtain the forced resonance of the antenna and the minimum changes in the beam tilt angle at the same time. When the proposed forced resonant beam tilting slot antenna with a 0.8 λ length is driven at -0.2 λ from the center, the main beam tilt angle of 57.7 degrees and the highest power gain of 3.8 dB are obtained. This slot element has a broad bandwidth, unlike the complementary dipole element.

Large-signal-based nonlinear models are developed to analyze a variety of dynamic performances in a resonant tunneling diode (RTD) with peripheral circuits such as an integrated broad band bow-tie antenna, a bias circuit and a bias stabilizer circuit. Dynamic modes of the RTD are classified by the time-domain analysis with the model. On the basis of our model, we suggest a possibility to discuss a terahertz order oscillation mode control, and the ASK modulation in several tens Gbit/sec in the RTD with the broad band antenna. Validity of the model and analysis is shown by explaining measured results of modulated oscillation signals in fabricated triple-barrier RTDs.

High frequency bands such as the 3-GHz band have received much attention as frequency resources for broadband mobile communication systems. Radio Frequency (RF) integrated antennas are considered to be useful as base station antennas in decreasing the feeding loss that is otherwise inevitable in high frequency bands and they ensure sufficient power for broadband transmission. One problem in actualizing RF integrated antennas is miniaturizing the duplexer, which is generally large, among the RF circuitry components. To downsize the duplexer, we consider separately locating the transmitter (Tx) and receiver (Rx) antennas. To suppress further the mutual coupling between the Tx and Rx antennas, we investigate a filter integrated antenna configuration. In this paper, we consider an aperture coupled patch antenna as the base antenna configuration and propose a new filter integrated antenna that comprises multiple rectangular elements installed between the coupling slot and radiation element of the Rx antenna. The simulation and measurement results confirm that the new antenna reduces the mutual coupling in the transmission frequency band up to 5.7 dB compared to the conventional slot coupled patch antenna configuration.

This paper presents a method to improve field uniformity using two TX antennas in a reverberation chamber with less steps of a stirrer. A mode-stirred reverberation chamber (MSRC) is considered as an alternative to the semi-anechoic chamber for an electromagnetic compatibility test because it provides a large test volume, a statistically uniform field, and a high maximum electric field. To improve field uniformity, we introduce two transmitting antennas for excitation in an MSRC, and predict statistical distribution of the complex reflection coefficients (scattering parameters). To prove the validation of our theory and the reliability of measurement results, three kinds of stirrers with different shape and sizes were fabricated and their efficiencies were measured in an MSRC, and then field uniformities have been investigated for 1–3 GHz frequency within the maximum number of independent samples that stirrers can provide. The measurement results show that the average received power is about 1.5 times as high as when using one transmitting antenna, and field uniformity is improved. Use of two transmitting antennas in an MSRC is regarded as a useful method to improve field uniformity at less stirrer steps, for radiated immunity tests.

A low cost, ultra small Radio Frequency (RF) transceiver module with integrated antenna is one of the key technologies for short range millimeter-wave wireless communication. This paper describes a 60 GHz-band transmitter module with integrated dipole antenna. The module consists of three pieces of low-cost organic resin substrate. These substrates are vertically stacked by employing Cu ball bonding 3-dimensional (3-D) system-in-package (SiP) technology and the MMIC's are mounted on each organic substrates by using Au-stud bump bonding (SBB) technique. The planer dipole antenna is fabricated on the top of the stacked organic substrate to avoid the influence of the grounding metal on the base substrate. At 63 GHz, maximum actual gain of 6.0 dBi is obtained for fabricated planar dipole antenna. The measured radiation patterns are agreed with the electro-magnetic (EM) simulated result, therefore the other RF portion of the 3-D front-end module, such as flip chip mounted IC's on the top surface of the module, does not affect the antenna characteristics. The results show the feasibility of millimeter-wave low cost, ultra small antenna integrated module using stacked organic substrates.

In the work we introduce novel approach to remote sensing from space for the estimation of sea wave heights with a spaceborne high precision two-frequency radar altimeter with nadir synthesis antenna aperture. Experiments show considerable reduction of the decorrelation factor of the correlation coefficient and so significant enhancement of the sensitivity of the altimeter for the estimation for the sea wave status.

This report focuses on a design method for gradient index (GRIN) lens antennas with controllable aperture field distributions. First, we derive differential equations representing optical paths in a gradient index medium with two optical surfaces by using geometrical optics, and then we formulate a novel design method for GRIN lens antennas based on these equations. The Levenberg-Marquardt algorithm is applied as a nonlinear least squares method to satisfy two conditions-focusing and shaping the aperture field distribution-thus realizing a prescribed radiation pattern. The conditions can be fulfilled by optimizing only the index (or permittivity) distribution, whereas the shapes of the optical surfaces remain as free parameters that can be utilized for other purposes, such as reducing reflection losses that occur on the surfaces, as illustrated in this report. A plano-concave GRIN lens is designed as an example, applying the proposed method, to realize a sidelobe level of -30 dB pseudo Taylor distribution, and a maximum sidelobe level of -29.1 dB was observed, indicating it is sufficiently accurate for practical use. In addition, we discuss the convergence of this method considering the relationship between the number of the initial conditions and the differential order of the design equations, factoring in scale invariance of the design equations.

This paper presents a new type of electromagnetic interference (EMI) measurement system. An EMI Camera LSI (EMcam) with a 124 on-chip 25050 µm2 loop antenna matrix in 65 nm CMOS is developed. EMcam achieves both the 2D electric scanning and 60 µm-level spatial precision. The down-conversion architecture increases the bandwidth of EMcam and enables the measurement of EMI spectrum up to 3.3 GHz. The shared IF-block scheme is proposed to relax both the increase of power and area penalty, which are inherent issues of the matrix measurement. The power and the area are reduced by 74% and 73%, respectively. EMI measurement with the smallest 3212 µm2 antenna to date is also demonstrated.

Joint transmit and receive antenna selection (JTRAS) is proposed for the multiple-input multiple-output (MIMO) two-way relaying channel. A simple and closed-form lower bound on the outage probability of JTRAS is derived. Furthermore, asymptotic analysis reveals that JTRAS can attain the maximum achievable diversity order of the MIMO dual-hop relaying channel.

This letter considers problems with an efficient link layer multicasting technique in a wireless personal area network environment using a directional antenna. First, we propose an adaptive directional multicast scheme (ADMS) for delay-sensitive applications in mmWave WPAN with directional antenna. Second, the proposed ADMS aims to improve throughput as well as satisfy the application-specific delay requirements. We evaluate the performances of legacy Medium Access Control, Life Centric Approach, and adaptive directional multicast schemes via QualNet 5.0. Our results show that the proposed scheme provides better performance in terms of total network throughput, average transmission time, packet delivery ratio and decodable frame ratio.

Miniaturized broadband antennas combining a fractal pattern and a self-complementary structure are demonstrated for UWB applications. Using four kinds of fractal patterns generated with an octagon initiator, similar to a self-complementary structure, we investigate the effect of the fractal pattern on broadband performance. The lower band-edge frequency of the broad bandwidth is decreased by the reduced constant input impedance, which is controlled by the vacant area size inside the fractal pattern. The reduced constant input impedance is shown to be produced by the extended current distribution flowing along the vacant areas. Given the results, miniaturized broadband antennas, impedance-matched to 50 Ω, are designed and fabricated. The measured return loss was better than 10 dB between 2.95 and 10.7 GHz with a size of 2712.5 mm. The lower band-edge frequency was reduced by 28% compared with the initiator.