Four-element Antenna Array Research Articles

Noncontact Measurement of the Instantaneous Heart Rate in a Multi-Person Scenario Using <inline-formula> <tex-math notation="LaTeX">${X}$ </tex-math> </inline-formula>-Band Array Radar and Adaptive Array Processing

A noncontact measurement of the heart rate of a specific person using an X -band radar system with a four-element antenna array is presented. The system comprises a 2-D planar wide-beam antenna array with a four-channel network analyzer. The direction of arrival is estimated using the Capon method, and the directionally constrained minimization-of-power algorithm is then applied to the received signals. Signals from the four channels are adaptively combined to enhance the accuracy in estimating the instantaneous heart rate in a multi-person scenario. Measurement results indicate that the proposed system with the adaptive array processing technique is effective for the noncontact measurement of the heart rate of a specific person when there is more than one person in the scene.

Millimetre‐wave dielectric resonator antenna array based on directive LTCC elements

The study deals with the application of low-temperature co-fired ceramic (LTCC) technology for design of a higher-order mode dielectric resonator antenna element operating at centre frequency 25.7 GHz. The LTCC material that the authors use provides very low dielectric losses and enables us to design an antenna element with very high radiation efficiency. The authors follow by examining the mutual coupling between two resonators and the authors propose a small (1 × 4) one-dimensional antenna array composed of such elements. In order to minimise the dimensions of the ground plane and to place the connector at a convenient location, the authors design a parallel feed network in substrate integrated waveguide technology, thus reducing the radiation losses of the feeding structure. The experiments verify the four-element antenna array concept with maximum measured gain of 16.3 dBi.

Switched-Beam 60-GHz Four-Element Array for Multichip Multicore System

This paper presents the design of a switched-beam four-element antenna array operating at 60 GHz for wireless data transfers between chips in a multichip computing system. The antenna-in-package uses a patterned artificial magnetic conductor to enhance antenna performance. The four-element array has a switchable pattern and shows improved transmission gain compared to previous designs used for data communication between chips. The impact of the array configuration on the switching of the antenna pattern is presented. The wireless link power received between TX and RX nodes is used to evaluate the four-element array antenna design.

Novel Microwave Tomography System Using a Phased-Array Antenna

In this paper, a novel microwave tomography (MWT) system that utilizes a phased-array transmitter antenna is presented. In contrast to contemporary MWT systems, the system presented herein consists of a single transmitter and multiple receivers. The single transmitter is a four-element array antenna; by varying the phase for each element in the array, the field distribution inside the imaging chamber varies, which produces a different set of measurements per phase configuration. Furthermore, the individual elements of the transmitting array antenna and the receiving antennas are of different types; the receiving antenna type is selected to maximize the coupling between the transmitter and the receiver. Due to the system’s complexity, the system is modeled using a neural network; the trained network is used as the forward solver for an inversion algorithm based on a Bayesian regularized Levenberg–Marquardt algorithm. The system along with the inversion algorithm is tested using several targets. Furthermore, the performance of the algorithm against various levels of experimental noise is analyzed and evaluated.

Design and evaluation of symmetric space–time adaptive processing of an array antenna for precise global navigation satellite system receivers

The most effective method for overcoming the interference vulnerability of global navigation satellite system (GNSS) receivers is to use an adaptive array antenna which has the capability of nulling or beamforming to a certain direction. The space–time adaptive processing (STAP) algorithm, which is very effective in signal processing of the array antenna for anti-interference, is studied. The phenomenon of pseudorange error in STAP is analysed with a new superposition method of linear line correlation functions. From this analysis, a new symmetric STAP algorithm, which uses an appropriate constraint condition for GNSS signals, is proposed to completely prevent this pseudorange error. The new STAP algorithm performance is verified and confirmed by simulations and experiments with a four-element array antenna. According to the simulation results, the new STAP algorithm has no pseudorange error, whereas the already existing STAP algorithm has an error of 1.6 m. Also experiments with four RF channels analogue-to-digital converter data and a real-time receiver confirm the effectiveness of their precise STAP algorithm which is easy to implement.

A Novel Approach for Millimeter-Wave Dielectric Resonator Antenna Array Designs by Using the Substrate Integrated Technology

This communication describes a novel concept of designing millimeter-wave (mm-wave) dielectric resonator antenna (DRA) arrays, in which the DRA element and part of its feeding network can be codesigned and cofabricated using the printed circuit board technology. Conventionally, the DRA and its feed are designed and fabricated using different dielectric materials. As a result, a large error might take place when mounting the DRA to its feed, which will result in significant influences to the performance of the antenna, especially to those operating in the mm-wave band. The proposed concept of the substrate integrated DRA provides a possibility to minimize the above mounting errors, by shaping the DRA and its feed together using the same material and fabrication process. Two kinds of antenna element, which separately exhibits linear and circular polarization, are designed at Ka-band. In order to demonstrate the feasibility of the proposed elements for array applications, two four-element antenna arrays in cooperation with different feeding networks and transitions are also designed, fabricated, and measured. Investigations show good agreement between simulation and measurement. The proposed substrate integrated DRA array can be easily extended to larger scales and has great potential to be integrated into mm-wave transceiver modules.

A 30-MHz–3-GHz CMOS Array Receiver With Frequency and Spatial Interference Filtering for Adaptive Multi-Antenna Systems

A 30-MHz–3-GHz wideband complementary metal–oxide–semiconductor phased array receiver with interference suppression capability in the frequency and spatial domains is presented. A frequency filtering function is provided by a two-stage harmonic rejection mixer with 16-phase local oscillator (LO) signals that are generated by frequency dividers and phase interpolators. The developed IC suppresses third- to seventh-order harmonic interference by more than 55 dB in a wide range from 30 MHz to 3 GHz. The 16-phase LO signal generator combined with a 2-b baseband phase shifter (PS) also works as a 6-b PS. Equipped with a 6-b amplitude control in addition to the 6-b phase control, the array receiver enables analog null steering that can reduce a spatial interference coming from a specific direction. The multi-chip synchronization needed for the null steering function is realized with pre-set circuits in the frequency dividers. Space propagation measurements made on a four-element array antenna system using the developed ICs indicated that the null steering function reduces spatial interference by 20 dB and reduces the error vector magnitude of a 2-GHz radio frequency, 20-MHz bandwidth, and 64-quadrature amplitude modulation signal from −12.7 to −26.3 dB even when a strong interferer exists.

A Broadband Dual-Polarized Base Station Antenna With Sturdy Construction

A broadband dual-polarized base station antenna with sturdy construction is presented in this letter. The antenna mainly contains four parts: main radiator, feeding baluns, bedframe, and reflector. First, two orthogonal dipoles are etched on a substrate as main radiator forming dual polarization. Two baluns are then introduced to excite the printed dipoles. Each balun has four bumps on the edges for electrical connection and fixation. The bedframe is designed to facilitate the installation, and the reflector is finally used to gain unidirectional radiation. Measured results show that the antenna has a 48% impedance bandwidth with reflection coefficient less than –15 dB and port isolation more than 22 dB. A four-element antenna array with 6° ± 2° electrical down tilt is also investigated for wideband base station application. The antenna and its array have the advantages of sturdy construction, high machining accuracy, ease of integration, and low cost. They can be used for broadband base station in the next-generation wireless communication system.

Reconfigurable Antenna for Jamming Mitigation of Legacy GPS Receivers

We propose a simple solution for jamming mitigation of L1 band GPS by electronically switching antenna beam for wide and narrow beamwidths. Assuming the jamming signal is directed from low elevation angles, antenna reception can be made significantly lower at these angles by electronically reconfiguring the antenna beamwidth. Four-element antenna array and one of the elements of the array are designated as antijam (array) mode and normal mode of the antenna. The antenna is placed on a degenerate-ground with symmetric slots in the ground. Front-end configuration for this antenna is also discussed. Simulations and measurements are performed to validate the proposed design. The antenna achieves more than 15 dB rejection in measurements and more than 20 dB cross-polarization improvement compared to standalone (normal mode) antenna. The system can easily be replaced with existing active antenna to improve antijam capability of the receiver.

A Low-Profile Dual-Polarized Microstrip Antenna Array for Dual-Mode OAM Applications

A dual-polarized dual-mode orbital angular momentum (OAM) microstrip antenna array is presented. The OAM radio beams are generated by employing a four-element antenna array with specific excitation. Each antenna element is an aperture-coupled microstrip patch antenna with a low profile of $0.1\lambda _{{\rm{0}}}$ . The quasi-cross-shaped aperture is excited by a U-shaped and an M-shaped microstrip feedline, which leads to two orthogonal polarizations. By adopting two types of phase-shifting schemes, the antenna array can be used to produce dual-mode OAM waves ( ${\rm{l}} = \pm 1$ ). The measured results show that the proposed antenna array has achieved good impedance matching over the band of 5.4–5.6 GHz, and a port-to-port isolation better than 25 dB. Moreover, the rotational phase fronts indicate waves properly bearing OAM with different states.

Compact transmit receive hybrid electromagnetic isolation in antenna array transceiver system for full duplex applications

This study presents a hybrid electromagnetic isolation mechanism in a transceiver array antenna operating at 5.8 GHz. Maximum isolation between transmitting and receiving array antennas, at a very close spacing (3 mm = 0.058 λ 0 ), and minimum mutual coupling between each array elements is achieved without antenna radiation pattern degradation. The achieved separation is equivalent to 44% size reduction compared with conventional half wavelength spacing criterion. Each of the transmitting and receiving array antennas is a four-element linear microstrip patch array antenna. The employed hybrid isolation technique is composed of defected ground structure, to minimise coupling between array elements, and uniplanar electromagnetic bandgap, to minimise the coupling between the transmitting and receiving antennas. The resulting transceiver array antenna system fulfils -35 dB mutual coupling between array elements, and 60 dB isolation between opponent transmitting and receiving array antennas. The proposed design procedures are discussed and analysed using electromagnetic full wave simulations. Results were verified through experimental measurements for reflection coefficient, mutual coupling and radiation characteristics in which a good agreement with simulated results is granted.

MFOA-integrated modified inverted F-based adaptive array Antenna for 2.4 GHz band applications

This research has proposed a modified fruit fly optimization algorithm (MFOA)-integrated adaptive array antenna (AAA) for the 2.4–2.5 GHz WLAN system. The principal components of the array antenna system encompass four array elements, four band pass filters (BPF), four digital phase shifters, a four-way power combiner/splitter, a directional coupler, a radio frequency (RF) detector, and a microcontroller unit (MCU). In the realization of the adaptive antenna system, the modified inverted F antenna with a finite ground plane was first innovated and subsequently deployed as the element of the four-element array antenna. In the study, simulations and experiments were carried out with the four-element AAAs of two configurations, i.e. the linear and planar array configurations. The simulation and experimental results revealed that the MFOA algorithmic scheme could determine the direction of the maximum arrival signal in an efficient and accurate manner and also was capable of manipulating the radiation pattern in the desired direction. In addition, the MFOA-integrated four-element AAA is of compact size (20 mm × 35 mm × 1.8 mm) and operable in the 2.31–2.55 GHz frequency band with omnidirectional radiation pattern and a gain of 1.6 dBi. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2016.

77-GHz Four-Element Phased-Array Radar Receiver Front End

A phased-array receiver module operating at 77 GHz is designed and manufactured to obtain beam-steering capability. The module has four patch antennas integrated with three active phase shifter (APS) chips on a single-layer Rogers 3003 printed circuit board PCB board. The W-band 1.65-mm2 novel APS chip is fabricated using 0.13- $\mu \text{m}$ SiGe Heterojunction Bipolar Transistor (HBT) technology. The APS consumes 100-mW dc power and achieves a peak gain of 9 dB at W-band and covers 360°. The phase shifter chips and PCB are packaged using low-cost wire-bond interconnections with insertion loss less than 7.5 dB. A novel method that exploits Klopfenstein tapering is also designed to connect coplanar waveguide to microstrip line with minimum insertion loss around 77 GHz. The measured gains of the phased-array receiver and passive four-element antenna array are compared. The module and passive array achieve the maximum gains of 9.7 and 10.4 dBi at 77 GHz. The simulated and measured results present well agreement at the W-band frequency. The beam can be steered to ±30°.

A Low-Cost and Complexity Multibeam RF Transmit Beamformer for Wideband LFM Radar

This letter presents a simple and efficient multibeam radio-frequency (RF) beamformer for wideband linear frequency modulation waveform transmission. A time-varying weighting method instead of the true time delay technique is proposed. The process of beamforming weighting is implemented by quadrature modulators in the transmit (TX) path. As the RF operation frequency changes, the modulating phase-shift coefficients in baseband vary in time series. Since this beamformer is easy to perform at the element level, the simultaneous and independent TX multiple beamforming has become achievable. Moreover, the quality of the output signal and the process of wideband equalization among multiple channels are considered. The channel imbalances over a broad frequency range are compensated by time-varying predistortion coefficients. To validate the practical feasibility of this method, a prototype system with four-element antenna array is designed and tested. Single-beam and simultaneous two-beam patterns steering between ± 30° over 500 MHz at the center frequency 2.45 GHz have been demonstrated experimentally.

Design of a Low-Profile Dual-Polarized Stepped Slot Antenna Array for Base Station

In this letter, a microstrip-fed dual-polarized stepped-impedance (SI) slot antenna element with a low profile is first proposed. The antenna is composed of two pairs of SI slots excited by two orthogonal stepped microstrip feedlines. The broadband characteristic is achieved by combining the fundamental and spurious resonances of the SI slot resonators, while the good cross polarization is mainly due to the introduction of the shorting pins. Secondly, based on the proposed antenna, a four-element antenna array is designed, constructed, and measured for base-station applications. Measured results demonstrate the bandwidths (return loss ) of the antenna array are 46.9% (1.55-2.5 GHz) and 38.7% (1.69-2.5 GHz) for Port 1 and Port 2, respectively. The isolation between the two ports is greater than 35 dB, whereas the cross-polarization level maintains lower than -27 dB across the entire operating band. In addition, the antenna array prototype achieves average gains of 13.5 and 13.9 dBi for horizontal polarization and vertical polarization, respectively.

Calibrated Layer-Stripping Technique for Level and Permittivity Measurement With UWB Radar in Metallic Tanks

A method to measure liquid level and electrical properties based on ultra-wideband pulsed radar is developed in this paper. Current methods of material property measurement using free-space radar typically use computationally intensive frequency-domain analysis or finite time-domain methods. The method presented is modified from layer-stripping algorithms and includes several improvements over previous techniques, such as an antenna array that allows measurement in a metallic tank environment and a method of calibration that characterizes path-loss and near-field effects for accurate amplitude-distance prediction. The method presented here also estimates the material loss properties and uses accumulated power with noise compensation to predict reflected pulse power. The method extends the use of pulsed radar for liquid-level measurement in tanks to the evaluation of liquid permittivity and the estimation of liquid height in liquids consisting of multiple layers. The accuracy of the presented method is evaluated using a transmitting single antenna element, a four-element antenna array, and an eight-element antenna array for measurement in a metallic tank environment. Accuracy is improved with larger antenna arrays, but the calibration becomes more critical. The accuracy for varying layer heights and materials is investigated to demonstrate the method reliability.

A PROPOSED DESIGN OF UWB MONOPOLE ANTENNA AND ITS LINEAR ARRAYS

A proposed design of ultra-wideband (UWB) monopole antenna has been presented to cover frequency range 2.49–14.42 GHz with small size. An equivalent circuit model with the parameter values of the optimized UWB antenna has been modeled. Moreover, a compatible lumped-elements utilized in equivalent circuit modeling for the proposed monopole antenna is established using the Advanced Design System (ADS). An UWB feeding network circuit has been designed in order to be used for exciting 2x1 and 4x1 linear antenna array. The measured and simulated results for the proposed feed network has a good return loss, isolation and power division ratio at all ports within the whole UWB frequency range. Two and four element UWB linear antenna arrays are presented. The average gain for the two-element antenna array is about 5.3 dBi and reaches to7.15 dBi for the four-element antenna array, over the whole UWB frequency range. A good agreement between the measured and the simulated results of all parameters for the antenna element and antenna arrays is appeared.

Compact antenna array receiver for robust satellite navigation systems

A compact navigation receiver comprising a decoupled and matched four-element L1-band antenna array with an inter-element separation of a quarter of the free-space wavelength is presented in this paper. We investigate the impact of the decoupling and matching network on the robustness of the navigation receiver. It is observed that in order to achieve high robustness with a compact antenna array, it is necessary to employ a decoupling and matching network, particularly in case of three spatially separated interferers. Furthermore, we study the influence of the polarization impurity of the compact planar antenna array on the equivalent carrier-to-interference-plus-noise ratio (CINR) of the receiver when impinged with different numbers of diametrically polarized interference signals. It is shown that the higher-order modes possess strong polarization impurity, which may halve the available degrees-of-freedom for nulling in the presence of linear-polarized interferers, using a conventional null-steering algorithm. We verify the robustness of the designed compact receiver by means of a complete global-navigation-satellite-system demonstrator. It is shown that the maximum jammer power that is allowed us to maintain the CINR above 38 dBHz with three interferers can be improved by more than 10 dB if a decoupling and matching network is employed.

Compact phased array antenna system based on dual‐band operations

ABSTRACTThis article presents a novel approach to shrink the size of the conventional phased array antenna fed by Butler matrix. The proposed size reduction of the phased array antenna is obtained by designing the whole system to operate at dual frequency bands. Due to the dual‐band operation, an N‐element phased array antenna can be used to generate 2N radiation beams, leading to a great size reduction. To verify this design concept, a dual‐band feed network is built based on a dual‐band 4 × 4 Butler matrix. By integrating this dual‐band feed network with a four‐element antenna array, eight distinct radiation beams can be realized. An experimental prototype operating at 5 and 8 GHz is designed and fabricated. It can achieve the same function as the conventional phased array antenna system using single‐band 8 × 8 Butler matrix, realizing a great size reduction. The simulated and measured results show good agreement with the design theory. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1391–1396, 2014

Wideband LTCC 60-GHz Antenna Array With a Dual-Resonant Slot and Patch Structure

This paper presents a wideband 60-GHz antenna array with a dual-resonant slot-patch structure. A multilayered low-temperature co-fired ceramic substrate was used for antenna fabrication. A half-wavelength resonant slot was designed with a backed substrate-integrated waveguide (SIW) cavity to enhance the front radiation. The inverted microstrip center-fed structure was designed for easy signal excitation and superior impedance matching. A parasitic patch was also applied to enhance for bandwidth and gain enhancement. The effects of the SIW cavity-backed slot antenna with and without parasitic patches were empirically examined. The simulated results show that adding parasitic patches increased the resonance of the poles and improved antenna gain by 1.85 dB and bandwidth by 9%. A 2 × 2 dual-resonant slot-patch antenna array was designed to further enhance the gain and bandwidth. The equipment setup for on-chip measurements of gain and radiation patterns was established. The measured S11 showed a wide bandwidth of 23%. The measured gain for the four-element antenna array was 9 dBi with slight fluctuations over the 57-64-GHz frequency range.