Small Electrical Size Research Articles

Широкополосный элемент антенной решетки СВЧ диапазона с управляемой поляризацией

There is an increasing interest with domestic satellite communication and broadband access services [1]. An integral part of such systems are ground terminals, the operating frequencies of which includes centimeter and millimeter bands. These circumstances require timely development of client terminal antennas. The article is devoted to the study of a compact Orthomode transducer combined with radiating element of relatively small electrical size (up to ≈ 1 λ), which can be used as part of an antenna array of a terrestrial satellite communication terminal. The proposed solution will make it possible to create arrays with controlled polarization in a wide frequency range. According to the modeling results, the frequency overlap coefficient of 1.4 is achievable, which corresponds to 93% of the standard waveguide frequency range.

A Compact Low Profile, Wideband and High Gain Stacked Dielectric Resonator Antenna

ABSTRACT In this paper, a novel, compact, low-profile miniaturized stacked Dielectric Resonator Antenna (DRA) for wideband applications is proposed. The design consists of two dielectric resonators of different dielectric constant stacked together. The Dielectric Resonators (DRs) are fabricated on the top side of the substrate (Taconic RF-35) with an inverted-trapezoidal patch as a feeding mechanism. The proposed configuration offers a wide impedance bandwidth of about 76.8%, covering the frequency range from 4.85 GHz to 10.88 GHz with TE21δ mode and TE23δ second higher-order mode being observed at the resonant frequencies of 6.14 GHz and 10.52 GHz, respectively. Peak gain of 8 dBi at 10.2 GHz is observed. The proposed antenna provides a wide impedance bandwidth, high radiation efficiency with smaller electrical size, and low profile of 0.19λg , where λg is the wavelength of the lower cut-off frequency.

Dynamically tunable multimodal vortex beam generator based on reflective metasurface

How efficiently generating a multi-mode vortex beam is the key to the new system of wireless communication technology based on orbital angular momentum. Due to the advantages of simple structure and flexible tunability of the metasurface, in recent years, people have been devoted to generating dynamic orbital angular momentum more simply and efficiently using programmable metasurfaces. To address the current problem of a single number of modes for generating orbital angular momentum vortex beams from metasurface, the programmable reflective metasurface structure has been designed to realize the function of dynamically tunable multi-mode of vortex beams. By loading two varactor diodes inside each metal patch to construct eight digital coding units, and using the programmable bias circuit to modulate the coding distribution and resonance characteristics on the metasurface in real-time, the metasurface obtains low reflection loss and stable reflection phase, and finally obtains vortex beams with mode numbers of ℓ = ±1, ℓ = ±2, and ℓ = ±3, respectively. The designed metasurface also has the advantages of a simple structure, small electrical size, and low profile, which has a large potential value in the communication of vortex beams and a perfect application in wireless transmission.

An active microfluidic sensor based on slow-wave substrate integrated waveguide for measuring complex permittivity of liquids

In this paper, a microfluidic sensor based on slow-wave substrate integrated waveguide (SW-SIW) is proposed to measure the complex permittivity of liquids and it achieves an ultrahigh quality factor of 51156, which is much higher than previous reported designs. The proposed sensor consists of three-layer dielectric substrates and an active circuit. The traditional SIW has the fundamental mode of TE101, whose electric field is concentrated inside the SIW structure. The SW-SIW, which is evolved from traditional SIW structure, has the characteristic of relatively small electrical size due to large equivalent capacitance and the capability to confine the electrical field density further. The internal rows of blind via holes are connecting the top layer of second substrate to the bottom layer of third substrate. In order to further reduce the electrical size, an air cavity is formed in second substrate around blind via holes as it can increase the equivalent capacitance of SW-SIW resonator. The air cavity has an important impact on the resonant frequency of the sensor, and the electrical size could be reduced by enlarging the air cavity. In this paper, an appropriate air cavity is adopted with comprehensive consideration of detection sensitivity and electrical size. The polydimethylsiloxane (PDMS) microfluidic substrate is embedded in first substrate. When the resonator is excited, the electric field is confined above the surface of blind vias. The electric field varies with the volume fraction of aqueous solution injected into the microfluidic channel, and the resonant frequency and quality factor alter correspondingly. The variations in the resonant frequency and quality factor are applied to retrieve the complex permittivity of liquid samples. The proposed sensor is fabricated and tested, it has a dimension of 0.678λ0 × 0.432λ0 (λ0 is the wavelength in free space at 3.7 GHz), and the peak sensitivity and unloaded quality factor are about 2.5 % and 51156, which are improved by 67 % and 5015 % than traditional SIW sensor, respectively. In particular, the sensitivity of measuring loss tangent of liquid sample is improved by several times to hundreds of times with the loss tangent range from 0.1 to 0.9 than other reported sensors. The measured data has a good agreement with the reference complex permittivity.

Standing-Wave Feeding for High-Gain Linear Dielectric Resonator Antenna (DRA) Array.

A novel feeding method for linear DRA arrays is presented, illuminating the use of the power divider, transitions, and launchers, and keeping uniform excitation to array elements. This results in a high-gain DRA array with low losses with a design that is simple, compact and inexpensive. The proposed feeding method is based on exciting standing waves using discrete metallic patches in a simple design procedure. Two arrays with two and four DRA elements are presented as a proof of concept, which provide high gains of 12 and , respectively, which are close to the theoretical limit based on array theory. The radiation efficiency for both arrays is about 93%, which is equal to the array element efficiency, confirming that the feeding method does not add losses as in the case of standard methods. To facilitate the fabrication process, the entire array structure is 3D-printed, which significantly decreases the complexity of fabrication and alignment. Compared to state-of-the-art feeding techniques, the proposed method provides higher gain and higher efficiency with a smaller electrical size.

An Approximation of 2-D Inverse Scattering Problems From a Convex Optimization Perspective

We present a two-step strategy to solve an inverse scattering problem in 2-D geometry. The first step approximates the inverse scattering as a convex optimization problem and provides an estimation of the total field inside the domain under investigation without <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> knowledge or tuning parameters. In the second step, the previously estimated total field is used to reconstruct the unknown contrast permittivity, which is represented by a superposition of level-1 Haar wavelet transform basis functions. Subject to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\ell _{1}}$ </tex-math></inline-formula> -norm constraints of the wavelet coefficients, a least absolute shrinkage and selection operator (LASSO) problem that searches for the global minimum of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\ell _{2}}$ </tex-math></inline-formula> -norm residual is exploited by accounting for the sparsity of the wavelet-based permittivity representation. Numerical results are presented to assess the effectiveness of the proposed formulation against objects with relatively small electric size. Finally, the approach is validated against experimental data.

Coplanar Waveguide-fed Electrically Small via-less Antenna for Dual Band Applications

In this paper, a simple coplanar waveguide fed compact electrically small antenna for dual-band operations without the use of via is presented. The resonances of the structure are obtained by spiraling one of the ground planes of an open-ended CPW transmission line with a short length center feed. The proposed antenna has a geometrical dimension of 0.079λ 01 × 0.079λ 01 mm2 (λ 01 is the free space wavelength of first resonant frequency) with a small electrical size (ka) of 0.35. The experimental studies on the fabricated prototype of the proposed antenna show a 2:1 VSWR bandwidth up to 2.53% and 4.12% for 2.3 and 5.3 GHz, respectively. The simulated antenna reflection and radiation characteristics are demonstrated with physical measurements.

A 28-GHz Reconfigurable SP4T Switch Network for a Switched Beam System in 65-nm CMOS

A 28-GHz SP4T absorptive switch (SAS) and reconfigurable switch network (RSN) in the 65-nm CMOS process are presented for a switched beam antenna array. The proposed SAS has the smallest electrical size among the previous millimeter-wave SASs. The length of the $t$ -line used in the proposed SAS is only 1/3 of that of the conventional quarter-wave $t$ -line-based absorptive switch. The proposed RSN is the first CMOS millimeter-wave switch-based RSN for a $4\times 4$ Butler matrix-based switched beam transceiver. The RSN is designed based on the SAS in order to operate in both the switch and divider modes. In the switch mode for single-port excitation, the RSN acts as an SAS. In the divider mode for dual-port excitation, the RSN operates as a Wilkinson power divider. Furthermore, the proposed RSN is realized in 2/3 the size of the conventional SAS. The measured insertion loss and isolation of the SAS are 3.8 and 22 dB, respectively. All return losses of the SAS input, output, and absorptive ports are better than 10 dB from 26 to 31 GHz. The silicon area and electrical size of the SAS is 0.9 mm2 ( $0.0078\lambda _{0}^{2}$ ), including pads. The measured insertion losses of the RSN in the switch and divider modes are 4.1 and 4.3 dB, respectively. The isolation of the switch and divider modes is 24 and 25 dB, respectively. All return losses of the RSN are better than 10 dB from 21 to 31.2 GHz. The silicon area of the RSN is 0.78 mm2 ( $0.0068\lambda _{0}^{2}$ ).

Radiation from free space TEM transmission lines

This work derives exact expressions for the radiation from two conductors non-isolated transverse electromagnetic (TEM) transmission lines of any small electric size cross-section in free space. The cases of infinite, semi infinite and finite transmission lines are covered and it is shown that while an infinite transmission line does not radiate, there is a smooth transition between the radiation from a finite to a semi-infinite transmission line. The present analysis is in the frequency domain and the authors consider transmission lines carrying any combination of forward and backward waves. The analytic results are validated by successful comparison with ANSYS commercial software simulation results, and successful comparisons with other published results.

Differential Shorted Patch Antennas

The design of a novel differential shorted patch antenna (DSPA) from a normal single-ended shorted patch antenna (SPA) is presented. It is shown that the DSPA has a smaller electrical size than the SPA. A transmission-line model is proposed to explain the reduced resonant size of the DSPA. A size reduction ratio of the DSPA to the SPA is defined and evaluated. It is found that the size reduction ratio mainly depends on the substrate thickness and the patch shape and slightly on the substrate dielectric constant. The simulated and measured results are given for both DSPA and SPA. The size reduction of the DSPA with respect to the SPA was experimentally validated.

A broadband negative refractive index meta‐atom for quad‐band and sensor applications

AbstractA new modified hexagonal design structure with broadband‐negative refractive index metamaterial was proposed in this manuscript. The proposed structure was composed of two symmetrical metallic layers which had same thickness and an FR4 dielectric layer that was sandwiched between these metallic layers. Frequency domain solver of CST microwave studio, which is commercially available was utilized to observe the results of the design structure. The design structure was analyzed by two orientations with respect to the incident plane wave. For normal wave incidence, the suggested structure displays broadband negative refractive index (3.18 GHz) and (0.9 GHz) with a higher effective medium ratio (17.26) that was indicated small electrical size of the structure, whereas for parallel wave incidence, broadband negative refractive index (2.45 GHz), (1.22 GHz), and (1.93 GHz) bandwidth with a higher effective medium ratio (28.01) was obtained. The negative refractive index was verified by simulation and measurement for quad‐band applications. Furthermore, the effective medium ratio (λ/a) of the proposed broadband negative refractive index metamaterial was considerably improved compared to previous suggested multiband metamaterials. In addition, the design structure can also be utilized as a pressure sensor.

A Novel Compact Wideband Patch Antenna for GNSS Application

As it is well known, the bandwidth of antenna will decrease with the decrease of antenna size and this feature limits the design of compact Global Navigation Satellite System (GNSS) patch antenna (1.1–1.6 GHz). In this communication, a novel wideband technique based on the mode analysis on the shorting load patch antenna is proposed. By adjusting the position and the size of the shorting load structure, the dominant resonant mode of patch antenna(TM10) is divided into two secondary modes and these two modes are combined together to form a wide operating band. It is proved that this new method has better bandwidth enhancement effect than the traditional methods. By utilizing this proposed method, a compact circularly polarization wideband patch antenna is designed for GNSS application, which has a small electrical size of only $0.2\lambda _{0}\times 0.2\lambda _{0}\times 0.05\lambda _{0.}$ ( $\lambda _{0}$ is the wavelength of low band in free space.) The simulated and measured results show that the proposed antenna has good and stable performance over the whole operating band, which means that it is quite an ideal compact antenna used for GNSS satellite navigation applications.

Small-sized body influence on the quality factor increasing of quasioptical open resonator

The results of an experimental study of electromagnetic waves scattering are described for small electric size bodies in the long-focus open resonator, whose quasioptical approximations are satisfied. It is shown that the effect of the Q factor increase is characteristic for such resonators, and for scatterers, not only spherical, but also of other geometrical forms whose sizes are small in comparison with a wavelength.

A triple-band dipole antenna for UMTS/LTE and UWB applications

ABSTRACTIn this paper, an ultra-wideband (UWB) dipole antenna with integrated Universal Mobile Telecommunications Service and long-term evolution 2.5 GHz band has been presented. The design process involves loading L-shaped and meandered line slots on UWB dipole antenna for achieving triple-band characteristics. The proposed antenna offers a small electrical size of 0.18λo * 0.23λo * 0.01λo with impedance bandwidths (|S11| < −10dB) of 11%, 6.5% and 127.7% centred at 2 GHz, 2.6 GHz and 10.8 GHz, respectively. The designed antenna shows good radiation characteristics with appreciable gain and omnidirectional radiation patterns over the operating bandwidth with satisfactory time domain performance. A prototype has been fabricated and tested in order to validate the simulation results.

Vertical Split Ring Resonator Using Vias With Wide Bandwidth and Small Electrical Size

In this letter, we propose a vertically inserted split ring resonator (SRR) in microstrip lines. Since the top and bottom layers of the resonator are electrically connected by using via holes and it has a 3-D shape, it occupies a small electrical size. Through numerical simulations and measurement, it is shown that it can provide a wider range variation of bandwidth than conventional planar SRRs and the resonant frequency and the bandwidth can be adjusted by its length and width, respectively.

Compact Dual-Band Textile PIFA for 433-MHz/2.4-GHz ISM Bands

A textile planar inverted-F antenna (PIFA) is proposed. By co-designing the PIFA antenna and the ground plane, a wide matching bandwidth is achieved around 433 MHz for a relatively small electrical size (0.202 × 0.115 × 0.01 λ 03). A slot within the PIFA patch enables the 2.4-GHz operating band. The measured bandwidths are 35 and 309 MHz in the lower and upper bands, respectively. The corresponding radiation efficiencies are 48% and 64%. The analysis of the effect of bending and the on-body characterization show the robust performance of the antenna.

Wide-Band High-Frequency Antennas for Military Vehicles: Design and testing low-profile half-loop, inverted-L, and umbrella NVIS antennas

The design of low-profile, wide-band (WB), high-frequency (HF), vehicular, on-the-move (OTM) antennas is associated with a number of challenges, including their small electrical size, mounting constraints, and the diverse environment in the near field, to name a few. This article considers antennas for near vertical incidence skywave (NVIS) operation from 2 to 15 MHz with a wide tunable bandwidth of at least 24 kHz. The minimum gain at the zenith of -25 dBi is comparable to that of state-of-the-art 3-kHz channel OTM NVIS antennas. The baseline configuration is a two-arm half loop operating in NVIS mode, designed such that it can be easily reconfigured into either an inverted-L or an umbrella-loaded monopole. Each arrangement has its own advantages in terms of radiation patterns, impedance, and practicality. Two arms are used to satisfy the performance requirements and keep the overall profile under 1 m. A full-scale prototype is fabricated and integrated with a specific military vehicle. The stand-alone measurements confirm the expected impedance behavior, whereas the tests with an experimental WB HF radio prove the validity of the design approach. Because of the diverse operation modes, the antenna is flexible and can readily adapt to various communication conditions.

(Invited) Scaled Magnetic Tunnel Junctions for High-Density Nonvolatile Memories

We report scaled magnetic tunnel junction (MTJ) for high-density nonvolatile cache memory. Under the same clock frequency, CPU performance can be improved by increasing its embedded cache memory capacity because the probability of cache misses decreases as cache memory capacity increases. Our motivation is to realize small magnetic tunnel junctions which enable high density embedded STT-MRAM cache. We have already proposed a unique fabrication technique which we call it as “shrink process” for reducing the size of a MTJ and realized MTJs with 20 nm in diameter [2014 Symposium on VLSI Technol. pp.212-213].In this paper, in order to realize scaled MTJs with an MgO barrier, two major issues have to be solved. One is to realize a very thin barrier to keep moderate MTJ resistance from the point of a 1-transistor and 1-MTJ memory cell configuration. Another is to fabricate small MTJs without increasing their size variation. In this paper, in order to realize the thin MgO barrier, its leakage mechanism was studied precisely, and proposed its model and possible solutions which will leads to much reduced leakage current and enough write endurance. The shrink process for small MTJs was also investigated from the point of scalability without increasing MTJ size variation. After the MTJ etching, various plasma treatments were done. During this treatment, the sidewall surface of the MTJ was modified, which resulted in the small electrical MTJ size of around 20 nm. Proposed techniques are scalable and promising for sub-20 nm MTJ generations. This work was funded by ImPACT Program of Council for Science, Technology and Innovation.

A compact CPW-fed wideband metamaterial-inspired antenna for GSM, WLAN/Wi-Fi, and WiMAX applications

A compact coplanar waveguide (CPW)-fed wideband metamaterial-inspired antenna is designed and developed in this paper. The proposed structure is an asymmetric structure in which three rectangular stubs are employed between signal patch and CPW ground plane. It is demonstrated that these stubs provides lumped parameters of conventional epsilon-negative transmission line (ENG-TL). As an advantage of these stubs proposed antenna operates on 1.67–2.76 GHz with −10 dB impedance bandwidth of 49.2%. The proposed antenna having small electrical size of 0.17λ0 × 0.35λ0 × 0.01λ0 at fo = 2.21 GHz. The simulated average gain and radiation efficiency of the proposed antenna is 1.61 dB and 96.33% respectively throughout the bandwidth. Properties such as smaller electrical size, simpler design, consistent radiation characteristics, and ease of fabrication are making this antenna suitable for GSM, WLAN/Wi-Fi, Bluetooth, and WiMAX applications.

RF System for Ultra-High Field Upper Extremity Imaging

INTRODUCTION: Imaging extremities in MR is an invaluable, non-invasive method widely used in orthopedic, hand surgery, post-transplant evaluation, variety of pathologic hand conditions.1 In order to address soft-tissue related challenges, UHF-MR imaging is the precise imaging tool which provides high signal/contrast-to-noise ratio (S/CNR), higher anatomic resolution, and reduced scan time.2 Due to the small electrical size (filling-factor) of the arm/hand, we use a TEM resonator in conjunction with eight channels receive (Rx)-only-insert array rather than the multi-channel transmit or transceiver approach at 7T. METHODS: A shielded design of an actively detuned TEM resonator has two ports driven by quadrature hybrid instead a T/R switch. It contains eight inductively decoupled surface loops (each 18x8 cm2 in size).3 A detailed method mentioned in Ibrahim et al4 was followed to simulate the TEM coil and human hand as a single system using FDTD in order to estimate RF power absorption for RF safety. All the MR experiments were conducted at 7T Siemens Magnetom scanner by recruiting volunteer under university approved IRB. RESULTS: For TEMcoil: S11:-21dB, S12:-16dB(<3%), Rxcoil: S11:-15dB, S12:-14dB(<3%). The mean/SD: 743/126(coverage area: 120sq.cm). The SNR:44, and CNR:33 for in-vivo coronal images (almost double compared to 3T throughout the volume measured and verified). At 7T, experimental B1+maps show a good agreement with the simulated B1+field distribution and average SAR/10g of tissue is 2.02W, and peak SAR/10g of tissue is 8.98W. T1VIBE shows exquisite anatomical detail identifying various nerve branches, cartilage delineation, brachial branches, nerve fascicles and vessel-wall imaging in forearm(and elbow); and palmer arch(PA), and proper digita palmer (PPD) arteries in hand. T2WDESS represents cartilage and ulnar nerve with high intensity signal delineation, synovial fluid (bright signal) in between very fine cartilage. SWI demonstrates forearm micro-vasculature; ToF depicts PA and PDP arteries; DTI shows FA (median:0.83, radian: 0.48) and Color-coded maps; vessel segmentation of brachial branches and venous vasculature. CONCLUSION: The actively detuned TEM coil now makes independent transmit-receive coil operation possible at 7T for extremities which surpasses the work of current 7T applications and it goes beyond head and body (torso) applications. Our ongoing work involves optimizing the coil design, musculoskeletal pulse sequence development, and in addition nerve and smaller vessel imaging for neuropathy and transplant patient populations.