Showing papers on "Microstrip published in 2020"
TL;DR: In this paper, a dual-band dual-polarized filtering antenna with high selectivity is proposed, where four slots at each side of a square radiating patch are etched with a microstrip line with open-circuit stepped-impedance resonators (OCSIRs).
Abstract: In this communication, a novel dual-band dual-polarized filtering antenna with high selectivity is proposed. By etching four slots at each side of a square radiating patch, dual operation bands as well as a natural radiation null between the two bands are observed. Another two radiation nulls are generated by introducing a novel feeding structure, which is composed of a microstrip line with open-circuit stepped-impedance resonators (OCSIRs). Thus, a dual-band bandpass filtering response of the realized gain is obtained. Each polarization of the antenna is differentially fed, and the differential port isolation is better than 37 dB. A prototype of the antenna element and a $1\times 4$ array is fabricated and tested to validate our design. Measured results show that the antenna element has dual operation bands of 3.28–3.71 and 4.8–5.18 GHz for VSWR < 1.5. Besides, a high out-of-band gain-suppression level which reaches 17.7 dB is also obtained. Good performance of the proposed antenna makes it a promising candidate for 5G sub-6 GHz base station systems.
113 citations
TL;DR: A broadband mmWave rectenna, the first rectenna realized on a flexible textile substrate for wearable applications, is presented, with a minimum radiation efficiency of 67% up to 30 GHz, over 3-dB improvement compared with a standard patch.
Abstract: Millimeter-wave (mmWave) bands, a key part of future 5G networks, represent a potential channel for RF energy harvesting, where the high-gain antenna arrays offer improved end-to-end efficiency compared with sub-6-GHz networks. This article presents a broadband mmWave rectenna, the first rectenna realized on a flexible textile substrate for wearable applications. The proposed novel antenna’s bandwidth extends from 23 to 40 GHz, with a minimum radiation efficiency of 67% up to 30 GHz, over 3-dB improvement compared with a standard patch. A stable gain of more than 8 dB is achieved based on a textile reflector plane. The antenna is directly connected to a textile-based microstrip voltage doubler rectifier utilizing commercial Schottky diodes. The rectifier is matched to the antenna using a tapered line feed for high-impedance matching, achieving broadband high voltage sensitivity. The rectifier has a peak RF–dc efficiency of 12% and a 9.5-dBm 1-V sensitivity from 23 to 24.25 GHz. The integrated rectenna is demonstrated with more than 1.3-V dc output from 12 dBm of mmWave wireless power across a 28% fractional bandwidth from 20 to 26.5 GHz, a 15% half-power fractional bandwidth, and a peak output of 6.5 V from 20 dBm at 24 GHz.
73 citations
TL;DR: In this article, a dual-polarized magnetoelectric (ME) dipole antenna with the feeding structure consisting of two orthogonal L-shaped probes with different heights is presented based on the low-temperature co-fired ceramic (LTCC) technology.
Abstract: A Ka -band wideband dual-polarized magnetoelectric (ME) dipole antenna with the feeding structure consisting of two orthogonal L-shaped probes with different heights is presented based on the low-temperature cofired ceramic (LTCC) technology. A simulated overlapped impedance bandwidth of 42.5% is achieved together with an isolation of higher than 24 dB between the two input ports and stable radiation characteristics over the operating band. By combining the radiating elements with a single-layered feed network composed of microstrip lines, a $4\times 4$ dual-polarized ME dipole antenna array is designed, fabricated, and measured. An overlapped impedance bandwidth of 45% that can cover the entire Ka -band, a gain up to 16.1 dBi, and stable symmetrical radiation patterns in the two orthogonal planes with cross polarization of less than −15 dB are experimentally confirmed. With advantages of the compact geometry, wide operating band, and promising radiation performance, the proposed antenna array with dual polarization would be attractive for millimeter-wave wireless applications in Ka -band.
68 citations
TL;DR: In this paper, the authors investigated the feasibility of designing a high gain on-chip antenna on silicon technology for subterahertz applications over a wide-frequency range, which achieved high gain by exciting the antenna using an aperture fed mechanism to couple electromagnetics energy from a metal slot line, which is sandwiched between the silicon and polycarbonate substrates, to a 15-element array comprising circular and rectangular radiation patches fabricated on the top surface of the poly carbonate layer.
Abstract: This letter investigates the feasibility of designing a high gain on-chip antenna on silicon technology for subterahertz applications over a wide-frequency range. High gain is achieved by exciting the antenna using an aperture fed mechanism to couple electromagnetics energy from a metal slot line, which is sandwiched between the silicon and polycarbonate substrates, to a 15-element array comprising circular and rectangular radiation patches fabricated on the top surface of the polycarbonate layer. An open ended microstrip line, which is orthogonal to the metal slot-line, is implemented on the underside of the silicon substrate. When the open ended microstrip line is excited it couples the signal to the metal slot-line which is subsequently coupled and radiated by the patch array. Measured results show the proposed on-chip antenna exhibits a reflection coefficient of less than −10 dB across 0.290–0.316 THz with a highest gain and radiation efficiency of 11.71 dBi and 70.8%, respectively, occurred at 0.3 THz. The antenna has a narrow stopband between 0.292 and 0.294 THz. The physical size of the presented subterahertz on-chip antenna is 20 × 3.5 × 0.126 mm3.
67 citations
TL;DR: The results show that the proposed model can predict the frequency response of the designed WPD, accurately, and results in a performance improvement of the proposed divider.
Abstract: In this paper, a novel miniaturized microstrip Wilkinson power divider (WPD) using squared resonators and open-ended stubs is designed, fabricated, and measured. The proposed divider is designed at 1.9 GHz, which suppresses 2nd, 3rd, and 4th harmonics with high attenuation levels. Moreover, the size of the proposed divider is only 0.1 λg × 0.07 λg, which reduces the circuit size by more than 55%, compared to the conventional Wilkinson divider. In the design process, the neural network model and LC-equivalent circuit model are used to predict the transmission zeros of the circuit. These transmission zeros are used to provide the suppression at the desired harmonics. Also, the main circuit elements could be predicted with the neural network model, which results in a performance improvement of the proposed divider. The results show that the proposed model can predict the frequency response of the designed WPD, accurately.
65 citations
TL;DR: In this article, a differential microwave microfluidic sensor based on the microstrip complementary split-ring resonator (MCSRR) structure for liquid characterization is presented, which exhibits a high sensitivity of 0.626% on average and is capable of suppressing unwanted environmental influences.
Abstract: This paper presents a differential microwave microfluidic sensor based on the microstrip complementary split-ring resonator (MCSRR) structure for liquid characterization. At the resonance, the electric field concentrates along the slot, where the microfluidic channel is located. As the liquid sample is injected, the corresponding reflection coefficient is changed, while the reference response is unaffected. The relative permittivity and loss tangent of the liquid can be extracted from the variations in the resonant frequency and quality factor. A prototype of the proposed sensor is fabricated and measured for functionality validation. The proposed sensor exhibits a high sensitivity of 0.626% on average and is capable of suppressing unwanted environmental influences.
64 citations
TL;DR: In this paper, a microstrip patch antenna was designed and fabricated using cold sintered CaTiO3-K2MoO4 (CTO-KMO) dielectric composites.
63 citations
TL;DR: The specific absorption rate (SAR) value was found that its impact on the human body SAR value is 1.68 W/kg, which indicates the safer limit to avoid radiation effects, and the proposed method is promising for telemedicine and mobile health systems.
Abstract: A compact textile ultra-wideband (UWB) antenna with an electrical dimension of 0.24λo × 0.24λo × 0.009λo with microstrip line feed at lower edge and a frequency of operation of 2.96 GHz is proposed for UWB application. The analytical investigation using circuit theory concepts and the cavity model of the antenna is presented to validate the design. The main contribution of this paper is to propose a wearable antenna with wide impedance bandwidth of 118.68 % (2.96-11.6 GHz) applicable for UWB range of 3.1 to 10.6 GHz. The results present a maximum gain of 5.47 dBi at 7.3 GHz frequency. Moreover, this antenna exhibits Omni and quasi-Omni radiation patterns at various frequencies (4 GHz, 7 GHz and 10 GHz) for short-distance communication. The cutting notch and slot on the patch, and its effect on the antenna impedance to increase performance through current distribution is also presented. The time-domain characteristic of the proposed antenna is also discussed for the analysis of the pulse distortion phenomena. A constant group delay less than 1 ns is obtained over the entire operating impedance bandwidth (2.96-11.6 GHz) of the textile antenna in both situations, i.e., side by side and front to front. Linear phase consideration is also presented for both situations, as well as configurations of reception and transmission. An assessment of the effects of bending and humidity has been demonstrated by placing the antenna on the human body. The specific absorption rate (SAR) value was tested to show the radiation effect on the human body, and it was found that its impact on the human body SAR value is 1.68 W/kg, which indicates the safer limit to avoid radiation effects. Therefore, the proposed method is promising for telemedicine and mobile health systems.
62 citations
TL;DR: Numerical comparisons show that the proposed antenna is superior to other published designs, which makes the proposed single antenna an excellent candidate for a multiple-input multiple-output (MIMO) system constructed from a number of properly allocated elements for 5G mobile communications with excellent diversity schemes.
Abstract: A compact dual-frequency ( 38 / 60 GHz ) microstrip patch antenna with novel design is proposed for 5G mobile handsets to combine complicated radiation mechanisms for dual-band operation. The proposed antenna is composed of two electromagnetically coupled patches. The first patch is directly fed by a microstrip line and is mainly responsible for radiation in the lower band ( 38 GHz ). The second patch is fed through both capacitive and inductive coupling to the first patch and is mainly responsible for radiation in the upper frequency band ( 60 GHz ). Numerical and experimental results show good performance regarding return loss, bandwidth, radiation patterns, radiation efficiency, and gain. The impedance matching bandwidths achieved in the 38 GHz and 60 GHz bands are about 2 GHz and 3.2 GHz , respectively. The minimum value of the return loss is − 42 dB for the 38 GHz band and − 47 for the 60 GHz band. Radiation patterns are omnidirectional with a balloon-like shape for both bands, which makes the proposed single antenna an excellent candidate for a multiple-input multiple-output (MIMO) system constructed from a number of properly allocated elements for 5G mobile communications with excellent diversity schemes. Numerical comparisons show that the proposed antenna is superior to other published designs.
60 citations
TL;DR: In this paper, a dual-polarized microstrip antenna with a capacitive blind-via fence is proposed for compact size, wide beamwidth, and high isolation for MIMO systems.
Abstract: A dual-polarized microstrip antenna loaded with capacitive via fence is proposed for compact size, wide beamwidth, and high isolation. By exploring a capacitive blind-via fence near the radiating apertures, the field is concentrated between the fence and ground, achieving obvious dimension miniaturization and wide beamwidth for regular dual-polarized microstrip antennas. The proposed blind-via fence is constituted by four rows of metallic wires with subwavelength diameter, period, and gap to the ground. Thanks to the field concentration brought by the blind-via fence, high isolation is realized by suppressing the radiation from the feeding probes, similar to two disk-loaded monopole antennas, and forcing the fundamental mode of the patch. To validate the proposed concept, a prototype is fabricated and characterized with the size of 0.19 $\lambda _{0} \times 0.19\,\,\lambda _{0} \times 0.07 \lambda _{0}$ ( $\lambda _{0}$ is the free-space wavelength at the center frequency). The simulated and measured results agree well, with wide half-power beamwidth of 107° and 105° in the E- and H-planes, respectively. Meanwhile, the port isolation is higher than 32 dB within the operating bandwidth of 2.48–2.56 GHz. The proposed antenna is with the merits of compact size, wide beamwidth, and high isolation, exhibiting potential usage in diversity or multiple-input and multiple-output (MIMO) systems with wide-coverage applications.
59 citations
TL;DR: In this article, a 34×34 array antenna for operation at Terahertz over a frequency range of 125-300 GHz for S11 ≤ -10dB, which corresponds a fractional bandwidth of 82.35%.
TL;DR: In this paper, a simple analytical method useful to optimize the sensitivity in differential sensors based on a pair of meandered microstrip lines is presented, where sensing is based on the phase difference of the transmission coefficients of both lines, when such lines are asymmetrically loaded.
Abstract: A simple analytical method useful to optimize the sensitivity in differential sensors based on a pair of meandered microstrip lines is presented in this paper. Sensing is based on the phase difference of the transmission coefficients of both lines, when such lines are asymmetrically loaded. The analysis provides the combination of operating frequency and line length (the main design parameters) that are necessary to obtain the maximum possible differential phase (±180°) for a given level of the differential dielectric constant (input dynamic range). The proposed sensor is useful to detect tiny defects of a sample under test (SUT) as compared to a reference (REF) sample. It can also be applied to the measurement of the complex dielectric constant of the SUT, where the real part is inferred from the differential phase, whereas the imaginary part, or the loss tangent, is derived from the modulus of the transmission coefficient of the line loaded with the SUT. It is experimentally demonstrated that the proposed device is able to detect the presence of few and small (purposely generated) defects in a commercial microwave substrate, as well as subtle variations in their density, pointing out the high achieved sensor sensitivity. Sensor validation is also carried out by determining the dielectric constant and loss tangent of commercial microwave substrates.
TL;DR: In this paper, a filter patch antenna and a bandstop filter with complementary transfer functions are used for absorbing the incident energy in the passband but largely absorbed by the resistor in the stopband.
Abstract: This article presents a compact absorptive filtering patch antenna. It consists of a filtering patch antenna and a bandstop filter (BSF), with their transfer functions being complementary to each other. A slot is fabricated in each of the patch and ground, giving a total of two radiation nulls for the lower bandedge. By using a dual-stub feed, two radiation nulls are also obtained for the upper bandedge. For the BSF, a $\lambda _{\mathrm {g}}$ /2 defected ground structure (DGS) and a $\lambda _{\mathrm {g}}$ /4 defected microstrip structure (DMS) are used in the design. It is terminated by a chip resistor. Since the filtering patch antenna and BSF have complementary transfer functions, the incident energy can be radiated effectively in the passband but largely absorbed by the resistor in the stopbands. As a result, only little energy will be reflected over a wide frequency range, giving a reflectionless characteristic. To demonstrate this idea, an absorptive filtering antenna operating at 5.8 GHz was designed, fabricated, and tested. Its impedance is matched from 5 to 6.5 GHz, with the measured out-of-band suppression being higher than 17 and 20 dB for the lower and upper stopbands, respectively. The measured peak realized gain is 7.28 dBi.
TL;DR: In this article, a substrate-integrated gap waveguide (SIGW)-fed metasurface antenna (metantenna) array with nonuniform excitation is proposed for wideband operation and sidelobe-level (SLL) reduction at millimeter-wave Ka-band.
Abstract: substrate-integrated gap waveguide (SIGW)-fed metasurface antenna (metantenna) array with nonuniform excitation is proposed for wideband operation and sidelobe-level (SLL) reduction at millimeter-wave Ka -band. To achieve wideband and low profile, a $2 \times 2$ square patch-based metasurface is introduced based on characteristic mode analysis (CMA). The ridged microstrip-fed slot is employed to excite the metasurface, while the mushroom-like patches are positioned around feeding lines to operate as the SIGW for suppressing the undesired modes. Due to the compactness of the proposed SIGW, the amplitude of each element is controllable using unbalanced T-junctions. A nonuniformly excited $4 \times 4$ antenna array is designed and fabricated for validation. The measured results show an impedance bandwidth ( $\vert \text{S}_{11}\vert dB) of full Ka -band with a 3 dB gain bandwidth of 28–40 GHz (35.3%) and SLLs less than −12.1 and −15.6 dB in the E- and H-planes, respectively.
TL;DR: In this paper, the authors presented a new concept for sensitivity enhancement of dielectric sensors by loading a microstrip line with multiple coupled resonators based on the interresonator coupling mechanism.
Abstract: This article presents a new concept for sensitivity enhancement of dielectric sensors by loading a microstrip line with multiple coupled resonators The concept is based on the interresonator coupling mechanism, which is represented as a mutual capacitance in an equivalent lumped circuit model This mutual capacitance increases the sensitivity of the sensor (in terms of a shift in the resonance frequency) to detect the presence of dielectric materials (ie, detecting changes in the real-relative permittivity of dielectric laminates) Complementary split-ring resonators (CSRRs) are utilized and coupled to a splitter-combiner microstrip section to design a 2CSRR and a 4CSRR sensor The new sensors provided an appreciable enhancement in the sensitivity when detecting dielectric material The concept is tested using full-wave numerical simulations to detect variations in the dielectric constant of a slab Finally, full experimental validation is provided using fabricated sensors
TL;DR: In this paper, the authors proposed a low-cost, easy-to-fabricate, contactless microwave sensor for dielectric characterization of liquids based on a multiple complementary split-ring resonator (MCSRR) fabricated on a low cost FR-4 substrate.
Abstract: We propose a low-cost, easy-to-fabricate, contactless microwave sensor for dielectric characterization of liquids. The design of the proposed sensor is based on a multiple complementary split-ring resonator (MCSRR) fabricated on a low-cost FR-4 substrate. A glass capillary tube having an inner diameter of $0.008\lambda _{{0}}$ is inserted in the high electric field region of the MCSRR to carry the liquid under test. The sensor is designed to operate at a resonant frequency of 2.45GHz for an empty tube and shifted resonant peaks are utilized for the dielectric characterization of different liquids. The maximum observed shifts in resonant frequency and Q factor are up to 400MHz and 31, respectively. The numerically established relations are experimentally verified through fabricated sensor for various binary mixtures of water and ethanol. The percentage errors between the calculated and reference permittivity of different samples are noticed to be less than 5%. The proposed device promises to be a cost-effective and convenient solution for accurate dielectric characterization of liquids and their binary aqueous solutions.
TL;DR: A low-profile and efficient substrate integrated waveguide (SIW) based self-triplexing antenna for Worldwide Interoperability for Microwave Access (WiMAX), fifth-generation (5G) and wireless LAN (WLAN) applications is proposed in this brief.
Abstract: A low-profile and efficient substrate integrated waveguide (SIW) based self-triplexing antenna for Worldwide Interoperability for Microwave Access (WiMAX), fifth-generation (5G) and wireless LAN (WLAN) applications is proposed in this brief. The antenna consists of two SIW cavities, out of which one is embedded in the other. The outer SIW cavity is excited with $50\Omega $ microstrip lines while the inner cavity inside the outer one is excited through a $50\Omega $ coaxial probe. The proposed triplexing-antenna works at three different frequencies [3.5 GHz (WiMAX band), 4.8 GHz (5G band) and 5.4 GHz (WLAN band)]. The outer SIW cavity provides two resonances at 4.8 and 5.4 GHz, while the inner cavity generates resonance at 3.5 GHz. High isolation (>26 dB) between the three ports is observed upon excitation of one cavity mode ( $TE_{101}$ ) and one patch mode ( $TM_{10}$ ). The antenna posses high gain and efficiency for all three bands along with >16.1 dB front-to-back ratio (FTBR). The proposed model is fabricated for validation of the simulated results. A reasonable matching between the simulated and measured results is observed.
TL;DR: This paper presents the design and realization of a compact ultra-wideband antenna with a rectangular notch wireless area network (WLAN) band that has controllable notched bandwidth and center frequency and the results show that the bandwidth and frequency could be controlled according to the on-demand rejection band applications.
Abstract: This paper presents the design and realization of a compact ultra-wideband (UWB) antenna with a rectangular notch wireless area network (WLAN) band that has controllable notched bandwidth and center frequency. The UWB characteristics of the antenna are achieved by truncating the lower ends of the rectangular microstrip patch, and the notch characteristics are obtained by using electromagnetic bandgap (EBG) structures. EBGs consist of two rectangular metallic conductors loaded on the back of the radiator, which is connected to the patch by shorting pins. A rectangular notch at the WLAN band with high selectivity is realized by tuning the individual resonant frequencies of the EBGs and merging them. Furthermore, the results show that the bandwidth and frequency of the rectangular notch band could be controlled according to the on-demand rejection band applications. In the demonstration, the rectangular notch band was shifted to X-band satellite communication by tuning the EBG parameters. The simulated and measured results show that the proposed antenna has an operational bandwidth from 3.1-12.5 GHz for |S11| < -10 with a rectangular notch band from 5-6 GHz, thus rejecting WLAN band signals. The antenna also has additional advantages: the overall size of the compact antenna is 16 × 25 × 1.52 mm3 and it has stable gain and radiation patterns.
TL;DR: In this paper, a high-efficiency broadband microwave rectifier with an extended range of input power is proposed for energy harvesting, where a novel broadband impedance-matching network is employed to reach high radio frequency (RF) to dc conversion efficiency.
Abstract: In this letter, a compact high-efficiency broadband microwave rectifier with an extended range of input power is proposed for energy harvesting. In the proposed structure, a novel broadband impedance-matching network is employed to reach high radio frequency (RF) to dc conversion efficiency. The reduction in mismatching loss over a wide bandwidth and input power range is achieved by impedance transformation from three segments of microstrip lines, which leads to a compact design to realize broadband impedance matching. A theoretical analysis and simulations of the proposed rectifier are presented. For validation, a broadband rectifier operating between 2.1 and 3.3 GHz is implemented and tested. The proposed rectifier shows a bandwidth of 44.4% for efficiency over 70% at an input power of 14 dBm. The measured efficiency remains above 50% from 2 to 3.3 GHz with an input power from 4 to 16 dBm. Moreover, the proposed rectifier has a compact size of 31 mm $\times18$ mm.
TL;DR: In this article, a modified complementary split-ring resonator (CSRR) was used to detect angular displacement and direction of rotation with high resolution and sensitivity over a wide dynamic range.
Abstract: This article presents a technique based on a modified complementary split-ring resonator (CSRR) to detect angular displacement and direction of rotation with high resolution and sensitivity over a wide dynamic range. The proposed microwave planar sensor takes advantage of the asymmetry of the sensor geometry and measures the angle of rotation in terms of the change in the relative phase of the reflection coefficients. The sensor consists of a movable modified CSRR (the rotor) and a microstrip line with a circular defect in the ground plane (the stator). By selecting the substrate material and the rotor thickness, the sensor can be designed to work at different operating frequencies. A theoretical model of the sensor is proposed and is followed by a detailed numerical analysis involving equivalent circuit simulations, full-wave computations, and measurement results. Using positioning error estimation and air-gap analysis, a technique based on phase-change measurements is found to be better than those based on magnitude measurements alone. The maximum sensitivity for measuring the angular rotation is found to be a 4.3° change in the relative phase of the reflection coefficient per 1° of rotation. The sensor has an angular measurement range from −90° to +90°. The sensor—a stator fabricated on a 0.5-mm-thick Rogers RT5880 substrate and three rotors fabricated on a 1.5-mm-thick Rogers RT5880, a 1-mm-thick FR4, and a 0.5-mm-thick Rogers RT5880—can effectively detect the direction of rotation, measure the angle of rotation and angular velocity with reasonable accuracy.
TL;DR: In this article, a differential-mode sensor based on a pair of electroinductive wave transmission lines (EIW-TLs) is proposed, which is implemented by etching a chain of complementary split-ring resonators (CSRRs) in a metallic plate.
Abstract: A differential-mode sensor based on a pair of electroinductive wave transmission lines (EIW-TLs) is proposed in this article. The EIW-TLs are implemented by etching a chain of complementary split-ring resonators (CSRRs) in a metallic plate. Such metallic plate acts as the ground plane of the microstrip (access) lines, necessary for feeding each EIW-TL and collecting the transmitted power at the output ports. The working principle of the sensor is mode conversion, caused when the EIW-TLs are asymmetrically loaded. Thus, one of the lines is loaded with the reference (REF) sample, whereas the other one is loaded with the sample under test (SUT). If both samples are identical and the pair of EIW-TLs is fed by a common-mode signal, a pure common-mode signal is collected at the differential output port. Conversely, mode conversion arises when the lines are unequally loaded, due to the different propagation characteristics (particularly the phase velocity) of the lines. Due to the typical dispersion relation of the EIW-TLs, with strong variation in the phase velocity (or phase constant) with frequency, the structure is very sensitive to dielectric constant differences between the REF and SUT samples. Thus, the proposed structure is useful for the accurate measurement of dielectric constants (sensor functionality) and the detection of tiny differences between the REF and SUT samples (comparator functionality).
TL;DR: In this article, the authors presented a microwave sensor for simultaneous measurement of permittivity and thickness in dielectric materials, which is made of a dual-mode magnetic-LC$ resonator coupled to a microstrip transmission line.
Abstract: This paper presents a microwave sensor for simultaneous measurement of permittivity and thickness in dielectric materials. The sensor is made of a dual-mode magnetic- $LC$ resonator coupled to a microstrip transmission line. Due to a dual-mode resonance of the magnetic- $LC$ resonator, the transmission response of the sensor shows two zero frequencies. By applying dielectric materials of various permittivities and thicknesses to the resonator, both of the transmission zero frequencies are modified. The alterations of the two transmission zero frequencies are used to characterize the permittivity and thickness of the dielectric samples under test. A prototype of the sensor is fabricated and measured for verifying the proposed sensing principle.
TL;DR: Experimental results obtained using a Vector Network Analyzer demonstrate a sensitivity performance of about 6.2 dB/(mg/ml) for the developed triple-pole sensor that significantly outperforms the conventional single-pole and other proposed sensors in the literature in terms of the resonance amplitude resolution.
Abstract: Planar microwave sensors are considered an attractive choice to noninvasively probe the dielectric attributes of biological tissues due to their low cost, simple fabrication, miniature scale, and minimum risk to human health. This paper develops and measures a novel microwave biosensor for non-invasive real-time monitoring of glucose level. The design comprises a rectangular plexiglass channel integrated on a triple-pole complementary split ring resonator (TP-CSRR). The proposed sensor operates in the centimeter-wave range 1–6 GHz and is manufactured using PCB on top of an FR4 dielectric substrate. The sensor elements are excited via a coupled microstrip transmission-line etched on the bottom side of the substrate. The integrated CSRR-based sensor is used as a near-field probe to non-invasively monitor the glucose level changes in the blood mimicking solutions of clinically relevant concentrations to Type-2 normal diabetes (70–120 mg/dL), by recording the frequency response of the harmonic reflection and transmission resonances. This indicates the sensor's capability of detecting small variations in the dielectric properties of the blood samples that are responsive to the electromagnetic fields. The proposed sensor is verified through practical measurements of the fabricated design. Experimental results obtained using a Vector Network Analyzer (VNA) demonstrate a sensitivity performance of about 6.2 dB/(mg/ml) for the developed triple-pole sensor that significantly outperforms the conventional single-pole and other proposed sensors in the literature in terms of the resonance amplitude resolution.
TL;DR: In this article, a hexagonal fractal super wideband antenna operating at terahertz frequencies is presented, which consists of three iterations of a Hexagonal slot loaded hexagonal radiator fed by a microstrip line, defected irregular partial ground plane along with a backed plane rectangular ring resonator.
TL;DR: In this article, a flat-layered lens based on gradient-refractive-index (GRIN) metamaterials is proposed for small-scale satellite technologies, which consists of multilayer double-sided microstrip square-rings units of variable sizes distributed on planar dielectric substrates.
Abstract: With the advent of small-scale satellite technologies, there has been significant interest in developing low-profile antennas. This article presents a novel collapsible flat-layered lens based on gradient-refractive-index (GRIN) metamaterials. The 3-D lens consists of multilayer double-sided microstrip square-rings units of variable sizes distributed on planar dielectric substrates to satisfy the required refractive index distribution. Adjacent layers can be stored compressed in a stacked configuration with minimal height, then deployed to an operational arrangement to their full dimensions and capabilities. The key factor in this design is the judicious choice of the discretized metamaterial unit cell such that neighboring layers are separated by an air gap, which allows the lens to collapse. A proof-of-concept prototype operating at 13.4 GHz with a 11.2 cm diameter and a height of 0.4 and 2.1 cm in collapsed and operational arrangement, respectively, was manufactured within fabrication tolerances. A resonant patch array feed was used and the lens antenna was measured in the UCLA Plane Bi-Polar Near-Field measurement range achieving a 23 dBi directivity and 22.2 dBi gain. The numerical and experimental results agree well and demonstrate that this new lens is advantageous in terms of low packaging height without compromising high-performance.
TL;DR: In this paper, a compact-balanced bandpass filter (BPF) and filtering crossover are proposed with intrinsic common-mode (CM) suppression by using a single-layered substrate-integrated waveguide (SIW) cavity.
Abstract: In this letter, compact-balanced bandpass filter (BPF) and filtering crossover are proposed with intrinsic common-mode (CM) suppression by using a single-layered substrate-integrated waveguide (SIW) cavity. The SIW cavity with low profile is TEn0m mode resonator, which has only one nonzero electric field component. Hence, it is also a natural frequency selection device of the differential signal. Meanwhile, the CM signal cannot excite the cavity due to the characteristics of perfect electric conductor (PEC) and perfect magnetic conductor (PMC). For the design of the balanced SIW BPF, the differential-mode (DM) equivalent half circuit is a single-ended SIW filter with height halved. Furthermore, the microstrip differential transition structure is designed to excite the SIW cavity and has little conversion between DM and CM. On this basis, a compact SIW-balanced filtering crossover is proposed using the degenerate modes TE102 and TE201. Finally, compact third-order SIW-balanced BPF and filtering crossover are designed and fabricated, and the measured results show good agreement with the simulated ones.
TL;DR: In this paper, a microwave microfluidic sensor for detecting binary liquid mixtures with a dielectric method at RF/microwave frequencies is presented, which is based on a split-ring resonator (SRR) that is implemented in a microstrip transmission line, with interdigitated electrodes (IDEs) being integrated into the ring for liquid detection.
Abstract: A microwave microfluidic sensor for detecting binary liquid mixtures with a dielectric method at RF/microwave frequencies is presented in this article. The sensor is based on a split-ring resonator (SRR) that is implemented in a microstrip transmission line, with interdigitated electrodes (IDEs) being integrated into the ring for liquid detection. Based on the equivalent circuit of the IDE-SRR device and with a series of finite element simulations, the detection theory is developed, and the device design optimization is investigated. The validation measurements on water–isopropanol liquid mixtures with various concentrations show that the proposed IDE-SRR sensor has higher sensitivity than the previous standard SRR sensor. The IDE-SRR sensor is then used to detect two binary liquids, i.e., water–methanol mixtures and water–tetrahydrofuran mixtures. The measured effective permittivity results of the binary mixtures at RF/microwave frequency range are compared with the existing mixing models for binary dielectric mixtures at zero frequency.
TL;DR: In this paper, a phase gradient metasurface (TGPMS) is proposed to extend the scanning range of planar phased arrays based on a phase gradients metamurface, which irregularly tailor the direction of propagation of the traversing electromagnetic waves.
Abstract: We propose a novel method to extend the scanning range of planar phased arrays based on a phase gradient metasurface. The phase gradient metasurface is developed by the generalized Snell’s law, which can irregularly tailor the direction of propagation of the traversing electromagnetic waves. The proposed transmission gradient phase metasurface (TGPMS) uses bidirectional expansion of the scanning range in a phased array application. The TGPMS consists of periodic and multilayer subwavelength elements that contribute to a wide range of transmission phase shift and multiple incident angular stability. The design is verified experimentally with a compact microstrip phased array that is integrated with the proposed TGPMS. Results demonstrate that the TGPMS extends the scanning range of the integrated array symmetrically, from [−36°, 38°] to [−56°, 60°]. The proposed TGPMS has additional desirable characteristics, such as high transmission, polarization insensitivity, tunable transmission phases in a wide range, and transmission phase stability for waves incident at different angles.
TL;DR: In this article, the authors present RTD oscillators that can employ one or two RTD devices of relatively large size, 9-25μm2, for high power and, at the same time, can oscillate at THz frequencies.
Abstract: Terahertz (THz) oscillators based on resonant tunneling diodes (RTDs) have relatively low output power, tens to hundreds of microwatts. The conventional designs employ submicron-sized RTDs to reduce the device self-capacitance and, as a result, realize higher oscillation frequencies. However, reducing the RTD device size leads to lower output power. In this article, we present RTD oscillators that can employ one or two RTD devices of relatively large size, 9–25 μm2, for high power and, at the same time, can oscillate at THz frequencies. This is achieved through low resonating inductances realized by microstrip or coplanar waveguide transmission line short stubs with low characteristic impedances ( Z 0), which have lower inductance values per unit length and so compensate the increase of the self-capacitance of large area RTD devices. Thus, fabrication using only photolithography is possible. It is also shown that device sizing, which is limited only by bias stability considerations, does not limit device bandwidth. Further, we report a new way to estimate the RTD oscillator output power with frequency. A series of oscillators with oscillation frequencies in the 245–309 GHz range and output powers from 0.1 to 1 mW have been demonstrated showing the feasibility of the proposed approach.
TL;DR: A compact wideband circularly polarized (CP) multiple-input multiple-output (MIMO) antenna with polarization diversity is proposed and characterized for off-body communication.
Abstract: Design of a compact wideband circularly polarized (CP) multiple-input multiple-output (MIMO) antenna with polarization diversity is proposed and characterized for off-body communication. The antenna is based on a simple coplanar waveguide (CPW)-fed monopole extension of the microstrip line. The orthogonal field components required by CP are induced using a simply modified right/left side ground plane. In particular, a stub extending from the ground plane along the length of the microstrip line generates the vertical component, whereas the current along the width of the ground plane contributes to the horizontal components. To obtain a unidirectional radiation pattern in the off-body direction and to reduce the sensitivity to the human body loading effects, a flat reflector printed on a high permittivity flexible substrate is applied. The simple topology of the antenna can be described by a few adjustable parameters, which facilitates its EM design closure. Prior to the experimental validation in the free space and on the body, the antenna is optimized at the full-wave level of description for all major performance figures. The overall footprint of the antenna radiator is only $L_{s}\,\,\times $ $W_{s} =0.24\lambda _{0} \times 0.64\,\,\lambda _{0} = 0.15\,\,\lambda _{0}^{2}$ . The proposed MIMO antenna features $\vert S_{11}\vert \le -10$ dB, average isolation $\vert S_{21}\vert \le -22$ dB, and axial ratio (AR) ≤3 dB from 5.2 GHz to 6.3 GHz with 100% bandwidth overlap between the impedance and axial ratio bandwidths. The envelope correlation coefficient (ECC) is less than 0.004 with the maximum diversity gain (DG) of approximately 9.99 dB. Moreover, the antenna maintains a high efficiency of up to 90% when loaded on the body, and a low specific absorption rate (SAR).