Showing papers on "Microstrip published in 2017"

Microwave Microfluidic Sensor Based on a Microstrip Splitter/Combiner Configuration and Split Ring Resonators (SRRs) for Dielectric Characterization of Liquids

Abstract: A microwave microfluidic sensor for dielectric characterization of liquids in real time is presented in this paper. The sensor is implemented in microstrip technology and consists of a symmetric splitter/combiner configuration loaded with a pair of identical split ring resonators (SRRs) and microfluidic channels placed on top of them (gap region). The sensor works in differential mode and sensing is based on frequency splitting. Thus, if the structure is unloaded or if it is symmetrically loaded with regard to the axial plane, only one transmission zero (notch) in the frequency response appears. However, if the axial symmetry is disrupted (e.g., by the presence of different liquids in the channels), two transmission zeros arise, and the difference in magnitude (notch depth) and frequency between such transmission zeros is indicative of the difference in the dielectric properties (complex dielectric constant). A circuit schematic, including transmission line sections to describe the distributed components, lumped elements to account for the SRRs and their coupling to the lines and lumped elements to model the liquid properties, is presented and validated. After proper calibration, the functionality of the proposed sensor is demonstrated by measuring the complex permittivity in solutions of deionized water and ethanol as a function of the ethanol content.

A Dual-Port Triple-Band L-Probe Microstrip Patch Rectenna for Ambient RF Energy Harvesting

Abstract: A dual-port triple-band L-probe microstrip patch rectenna design for ambient RF energy harvesting using the GSM-900, GSM-1800, and UMTS-2100 bands is described. The compact dual-port L-probe patch antenna is implemented by stacking two single-port patch antennas back to back. Each port can independently harvest RF signal from a half-space with gain greater than 7 dBi, and together with both ports in a dc combining configuration, the antenna can acquire RF energy from nearly all directions. We also provide a design for a high-efficiency triple-band rectifier operating at GSM-900, GSM-1800, and UMTS-2100, which is replicated on each port and concatenated together to allow dc combining and near doubling of the output dc voltage. Measurement results show that our prototyped dual-port triple-band rectenna can receive RF power from nearly all directions with an efficiency of greater than 40% and an output voltage of more than 600 mV when the power density is greater than 500 $\mu \mathrm{W}/\mathrm{m}^{2}$ .

Mixer-Duplexer-Antenna Leaky-Wave System Based on Periodic Space-Time Modulation

Abstract: We present a mixer-duplexer-antenna leaky-wave system based on periodic space-time modulation. This system operates as a full transceiver, where the upconversion and downconversion mixing operations are accomplished via space-time transitions; the duplexing operation is induced by the nonreciprocal nature of the structure, and the radiation operation is provided by the leaky-wave nature of the wave. A rigorous electromagnetic solution is derived for the dispersion relation and field distributions. The system is implemented in the form of a spatio-temporally modulated microstrip leaky-wave structure incorporating an array of subwavelengthly spaced varactors modulated by a harmonic wave. In addition to the overall mixer-duplexer-antenna operation, frequency beam scanning at fixed input frequency is demonstrated as one of the interesting features of the system. A prototype is realized and demonstrated by full-wave and experimental results.

A Low-Profile Aperture-Coupled Microstrip Antenna With Enhanced Bandwidth Under Dual Resonance

Abstract: A low-profile aperture-coupled microstrip patch antenna (MPA) using the TM10 and TM30 resonant modes to enhance the impedance bandwidth is proposed in this paper. Based on the cavity model for a square MPA, the TM10 and TM30 modes as well as both higher odd-order and even-order modes between them can be characterized. In order to combine the dual radiative resonant modes for a wide impedance bandwidth, a rectangular radiating patch with an aperture-coupled feeder is employed and theoretically investigated at first, aiming to demonstrate that all of the undesired modes between them can be removed effectively. After that, by loading the shorting pins properly underneath the patch, the resonant frequency of TM10 mode is shown to progressively turn up with slight effect on that of TM30 mode. As a result, these two radiative modes can be allocated in proximity to each other, resulting in a wide impedance bandwidth with a stable radiation pattern and the same far-field polarization. Moreover, the principal parameters of the MPA have been extensively studied in order to investigate the sensitivity in input impedance of the aperture-fed patch antenna. Finally, the proposed antenna is fabricated and measured. Simulated and measured results are found in good agreement with each other and illustrate that the antenna achieves a wide impedance bandwidth of about 15.2% in fraction or 2.32–2.70 GHz under $\vert \text{S}_{\mathrm {\mathbf {11}}}\vert dB, while keeping a low profile property with the height of 0.032 free-space wavelength. Besides, a stable gain varied from 3 to 6.8 dBi within the whole operating band is also obtained.

Reflectionless Adaptive RF Filters: Bandpass, Bandstop, and Cascade Designs

Abstract: A class of frequency-reconfigurable input-reflectionless/absorptive RF/microwave filters is presented. They consist of tunable complementary-duplexer architectures that are composed of a main and an auxiliary channel with opposite filtering transfer functions. By loading the auxiliary channel with a reference-impedance resistor and by taking the output node of the main channel as the output terminal of the overall circuit, a filtering network of the same type of the main channel with theoretically perfect input-reflectionless behavior at all frequencies can be realized. This technique can be applied to design spectrally agile completely input-reflectionless filters with any kind of transfer function, such as low-pass, high-pass, and single/multiband bandpass/bandstop filters. The theoretical analysis of the first-order absorptive bandpass/bandstop filtering sections based on a coupling-matrix formulation is detailed. Furthermore, the synthesis of high-selectivity reflectionless filters either by cascading multiple first-order cells or using high-order channels in a single complementary duplexer is also described. For practical-demonstration purposes, frequency-tunable lumped-element and microstrip prototypes are manufactured and characterized. They correspond to first- and second-order bandpass/bandstop filters. In addition, their in-series cascade connection is used to implement a bandpass filter with spectrally controllable passband and out-of-band notches.

A New Technique to Design Circularly Polarized Microstrip Antenna by Fractal Defected Ground Structure

Abstract: A new technique to design single-feed circularly polarized (CP) microstrip antenna is proposed. The CP radiation is obtained by adjusting the dimension of the etched fractal defected ground structure (FDGS) in the ground plane. Parameter studies of the FDGS are given to illustrate the way to achieve CP radiation. The CP microstrip antennas with the second and third iterative FDGS are fabricated and measured. The measured 10-dB return-loss bandwidth of the CP microstrip antenna is about 30 MHz (1.558 to 1.588 GHz), while its 3-dB axial-ratio bandwidth is 6 MHz (1.572 to 1.578 GHz). The gain across the CP band is between 1.7 and 2.2 dBic.

Design of filtering microstrip antenna array with reduced sidelobe level

Abstract: For the requirements of efficient integration and simple fabrication, a new codesign approach for a microstrip filter with an antenna array with reduced sidelobe level is introduced in this communication. The microstrip patch antennas and the stub-loaded resonators are used to illustrate the synthesis of a bandpass filtering antenna array. By controlling the coupling strength between the resonators, a uniform or nonuniform power divider network can be obtained. A nonuniform power division is used to reduce the sidelobe level. The equivalent lumped circuit model is developed and analyzed in detail. Two types of eight-element filtering antenna array with uniform and tapered power-distribution among the elements have been designed. Simulated and measured results provide a good verification for the theoretical concepts.

Dual-Polarized, Differential Fed Microstrip Patch Antennas With Very High Interport Isolation for Full-Duplex Communication

Abstract: This communication presents two dual-polarized microstrip patch antenna systems based on a single radiating element with 180° ring hybrid coupler for differential feeding to achieve high interport RF isolation. One of the implemented single-layer patch antennas provides more than 67 dB isolation between transmit (Tx) and receive (Rx) ports at 2.4 GHz while the second fabricated antenna with slot coupled Tx port along with differential feeding for Rx operation provides more than 90 dB RF isolation at 2.41 GHz between dc isolated Tx–Rx ports. Moreover, the single-layer antenna provides better than 62 dB interport isolation for 10 dB-return loss impedance bandwidth (BW) of 50 MHz. Measured interport isolation for implemented antenna with slot coupled Tx port achieves around 70 and 79 dB port to port RF isolation for 50 and 20 MHz BWs, respectively, and these are the highest amounts of isolation for a single antenna to best of our knowledge. The antenna with slot coupled Tx port provides more interport RF isolation as compared to single-layer antenna due to low coupling between slot coupled and co-planar quarter-wave microstrip fed ports. Both antenna structures have the capability to remove in-band nonlinear self-interference (SI) components without complex SI cancellation circuits.

Transparent Microstrip Patch Antennas With Multilayer and Metal-Mesh Films

Abstract: This letter presents transparent microstrip patch antennas made of two types of transparent conductive films, which are multilayer film (MLF; IZTO/Ag/IZTO) and metal-mesh film (MMF; Cu). The sheet resistance levels of the MLF and MMF are 2.52 and 0.18 Ω/□. The transparencies of the MLF and MMF are over 80% and 60% at a 550-nm wavelength, respectively. The design and dimensions of the antennas follow the conventional simple microstrip patch antenna. A transparent acryl substrate is used for the proposed transparent antennas. The conductive parts of the proposed antennas are also made of copper sheets (CS; case 1) for the performance comparison to two types of transparent antennas made of MLF (case 2) and MMF (case 3). The resonance frequency band of the antennas is 2.4–2.5 GHz for Wi-Fi service. The case-1, case-2, and case-3 antennas have peak gains of 4.75, −4.23, and 2.63 dB and have radiation efficiencies of 66.32%, 7.76%, and 42.69% at the center frequency of the Wi-Fi service band (2.45 GHz), respectively.

Design of SRR-Based Microwave Sensor for Characterization of Magnetodielectric Substrates

Abstract: A novel split-ring resonator (SRR)-based microwave sensor for accurately determining the real parts of the complex permittivity and the complex permeability of magnetodielectric composites is proposed. The proposed sensor is realized using the microstrip technology, where two SRRs coupled magnetically with the microstrip line are printed on two sides of the line. The sensor is designed using the full-wave electromagnetic solver and its equivalent circuit model is obtained. A numerical model of the proposed sensor is developed for extracting the magnetic and the dielectric properties of the sample under test in terms of change in resonance frequency after loading the device with the test specimen. The proposed methodology is validated by fabricating the sensor on RT/duroid 6006 substrate and testing various standard dielectric and magnetodielectric samples viz. Teflon, Poly vinyl chloride, Plexiglas, Polyethylene, Carbonyl iron, Ni0.6Co0.4Fe2O4, and Cobalt (30%)/Polystyrene composite in S-band. The measured relative permeability and the relative permittivity of the test specimens are found to be in close agreement with their values available in literature with maximum error of less than 8%.

A Novel Broadband Dual Circularly Polarized Microstrip-Fed Monopole Antenna

Abstract: A broadband dual circularly polarized (CP) planar monopole antenna is presented in this communication. The antenna is fed by dual orthogonal microstrip lines for polarization diversity. Circular polarization is achieved with a modified ground-plane structure and the isolation between the ports is improved by extending a protruded strip between the feed lines. L-shaped strips (LSSs) and inverted LSSs are designed along the radiating edges of the monopole. The combination of these two strips maximizes the axial ratio (AR) bandwidth, when they are placed $\lambda _{g}$ /4 apart at center frequency of the CP band. This principle is verified by fabricating the prototype on a 1-mm-thick FR4 substrate with 32 mm $\times32$ mm lateral dimension. From the experimental results, it is observed that the 3-dB AR bandwidth of the proposed antenna is 80.7% (3.74–8.8 GHz). The gain, return loss, and port isolation are higher than 1, 10, and 20 dB, respectively, within the CP band.

Microwaves-Based High Sensitivity Sensors for Crack Detection in Metallic Materials

Abstract: This paper presents a highly sensitive sensor for crack detection in metallic surfaces. The sensor is inspired by complementary split-ring resonators which have dimensions much smaller than the excitation’s wavelength. The entire sensor is etched in the ground plane of a microstrip line and fabricated using printed circuit board technology. Compared to available microwave techniques, the sensor introduced here has key advantages including high sensitivity, increased dynamic range, spatial resolution, design simplicity, selectivity, and scalability. Experimental measurements showed that a surface crack having 200- $\mu \text{m}$ width and 2-mm depth gives a shift in the resonance frequency of 1.5 GHz. This resonance frequency shift exceeds what can be achieved using other sensors operating in the low GHz frequency regime by a significant margin. In addition, using numerical simulation, we showed that the new sensor is able to resolve a 10- $\mu \text{m}$ -wide crack (equivalent to $\lambda $ /4000) with 180-MHz shift in the resonance frequency.

Dual-Band and Dual-Circularly Polarized Single-Layer Microstrip Array Based on Multiresonant Modes

Abstract: A planar dual-band array with orthogonal circular polarizations (CPs) in the two frequency bands is proposed in this communication. The array is implemented on a single-layer substrate and easy to be extended to the design of a larger array. A new antenna element for such an array is exploited by symmetrically loading stubs on the edges of a square patch. In this communication, two pairs of orthogonal modes of the patch, namely, TM10/TM01 and TM30/TM03, are excited simultaneously and used to realize different senses of CP radiation in the two bands. An equivalent transmission-line model of this patch is then developed to describe its working principle and design procedure. To validate its effectiveness, a $2 \times 2$ -element array prototype operating at 2.53 and 3.59 GHz is designed and fabricated. Both the left- and right-hand CPs are obtained simultaneously in the dual bands, and the measured results are found to be in good agreement with the simulated ones. The measured radiation gains in the lower and higher bands are 10.8 and 12.5 dBic, respectively.

Dual-Band Transmitarrays With Dual-Linear Polarization at Ka-Band

Abstract: Dual-band transmitarray antennas are demonstrated at Ka-band with the capability of forming independent linearly polarized beams with a given polarization in each frequency band, while sharing the same radiating aperture. The proposed three-layer unit-cell is based on identical narrow microstrip patches printed on both receiving and transmitting layers and connected by a metallized via hole. The metal layers are printed on two identical substrates bonded with a thin film, and the designed unit-cell exhibits a 180° phase resolution (i.e., 1-b phase quantization). The dual-band dual-polarized property of the transmitarray is achieved by interleaving unit-cells operating in the down-link and up-link frequency bands. Four different prototypes are characterized to demonstrate the relevance of the proposed concepts. A good agreement is obtained between the radiation patterns, gain curves, and cross-polarization levels measured and computed in both frequency bands and polarizations.

A Novel Single-Diode Microwave Rectifier With a Series Band-Stop Structure

Abstract: A single-diode compact microwave rectifier with a series band-stop structure is presented in this paper. The band-stop structure is connected to the diode in series to block the harmonics produced during rectifying. It replaces the cascading bandpass or low-pass filter between the input and the diode in a conventional microwave rectifier. A microwave rectifier at 2.45 GHz with an HSMS 282 Schottky diode is realized based on the proposed design method. A short-ended eighth-wavelength microstrip transmission line is applied to the rectifier in series with the diode as a band-stop structure. The short-ended microstrip transmission line presents an inductive impedance to compensate the diode capacitive impedance at fundamental frequency and turns to an open circuit to block the second harmonic for power recycling. The proposed circuit shows a novel schematic for compact microwave rectifiers. The fabricated rectifier is compact with a dimension of $0.15\lambda _{g} \times 0.2\lambda _{g}$ . A microwave-to-dc conversion efficiency of 80.9% is achieved at 20 dBm input power with a 580- $\Omega $ dc load.

Backward to Forward Scanning Periodic Leaky-Wave Antenna With Wide Scanning Range

Abstract: A new type of circularly polarized printed periodic leaky-wave antenna (LWA) structure with a wide scanning range and reduced sidelobe level (SLL) is presented Fifteen matched unit cells (UCs) are cascaded along the direction of propagation to provide seamless frequency scanning from 20 to 29 GHz with a scanning range of 95° from backward to forward quadrant The open-stopband has been suppressed around the broadside region by matching the input impedance of the UC to the characteristic impedance of the transmission line Two empirical transmission line models are presented to describe the behavior of the periodic LWA Parametric study using full-wave simulation is used to improve the SLL and minimize the axial ratio of the circular polarization leading to a fully optimized periodic leaky LWA

Bandpass Class-F Power Amplifier Based on Multifunction Hybrid Cavity–Microstrip Filter

Abstract: This brief presents a filter-integrated high-efficiency class-F power amplifier (PA). The hybrid cavity–microstrip filtering circuit is employed not only to realize output impedance matching and the third-harmonic manipulation but also to provide high-selectivity bandpass responses. To fulfill the requirements of high-efficiency class-F PAs, cavity resonators and microstrip feeding structures are involved, and their benefits are fully exploited. The metal cavity resonator features a high $Q$ value and, thus, low loss in the passband, resulting in high efficiency. Moreover, metal walls of cavities act as heat sink for the transistor. The microstrip feeding structures are used to improve the skirt selectivity and manipulate the third harmonic. Moreover, it features easy integration with the transistor, and thus, the transition between cavity and microstrip lines is eliminated. The hybrid filter is characterized based on filter synthesis theory. Complex impedance conversion analysis is carried out to guide the impedance transformation from 50 $\Omega$ to a complex one desired by the transistor. For demonstration, a filtering PA operating at 2.4 GHz is designed and measured. It exhibits both high-selectivity bandpass responses and good PA performance with maximum power-added efficiency of 70.9% at 40.8-dBm output power.

Near-Field Chipless-RFID System With High Data Capacity for Security and Authentication Applications

Abstract: A high data capacity chipless radio frequency identification (chipless-RFID) system, useful for security and authentication applications, is presented in this paper. Reading is based on the near-field coupling between the tag, a chain of identical split-ring resonators (SRRs) printed on a (typically flexible) dielectric substrate (e.g., liquid crystal polymer, plastic, and paper), and the reader. Encoding is achieved by the presence or absence of SRRs at predefined (equidistant) positions in the chain, and tag identification (ID) is based on sequential bit reading. Namely, the tag must be longitudinally displaced, at short distance, over the reader, a microstrip line loaded with an SRR and fed by a harmonic signal. By this means, the harmonic signal is amplitude modulated, and the (ID) code is contained in the envelope function, which can be obtained by means of an envelope detector. With this system, tag reading requires proximity with the reader, but this is not an issue in many applications within the domain of security and authentication (e.g., secure paper for corporate documents and certificates). Several circularly shaped 40-bit encoders (implemented in a commercial microwave substrate), and the corresponding reader, are designed and fabricated as proof-of-concept demonstrators. Strategies for programming the tags and a first proof-of-concept chipless-RFID tag fabricated on plastic substrate through inkjet printing are included in this paper.

Enhanced Tunable Microstrip Attenuator Based on Few Layer Graphene Flakes

Abstract: This letter presents a voltage-controlled tunable attenuator based on few layer graphene flakes. The proposed structure exploits the variation of graphene resistance with an applied bias voltage. The attenuator consists of a microstrip line, connected to grounded metal vias through graphene pads: when no bias voltage is applied, the resistance of graphene is high and the pads behave as open circuits, causing minimum attenuation. By increasing the bias voltage, the resistance of the graphene pads decreases, connecting the metal vias to the microstrip, thus increasing the attenuation. A prototype operating in the frequency band from dc to 5 GHz has been designed and tested. The measured attenuation ranges from 0.3 to 15 dB at 3 GHz, with a bias voltage ranging from 0 (minimum attenuation) to 6.5 V (maximum attenuation).

An SIW Cavity-Backed Self-Diplexing Antenna

Abstract: A novel and simple design of a substrate-integrated waveguide (SIW)-based self-diplexing antenna is presented in this letter. The SIW cavity is fed by two individual microstrip feed lines. The two transverse slots of different lengths, which radiate at two distinct resonant frequencies, are etched on the top surface of the cavity. A high isolation (better than 27.9 dB) is achieved between two ports, which leads to obtaining the self-diplexing characteristic of the antenna. The proposed antenna offers a gain of 3.56 and 5.24 dBi at 8.26 and 10.46 GHz, respectively. The antenna exhibits independent frequency tunability at both the operating bands.

Single-Feed Dual-Band Circularly Polarized Dielectric Resonator Antenna for CNSS Applications

Abstract: A cross-slot-coupled dual-band circularly polarized rectangular dielectric resonator antenna (RDRA) with a small frequency ratio (123) based on compass navigation satellite system (CNSS) applications is designed, fabricated, and measured The RDRA is excited to resonate at two pairs of near-degenerate orthogonal modes of TE111 and TE113, and a cross slot is introduced to simultaneously achieve dual-band right-hand circular polarization The measured −10 dB impedance bandwidths of 114% and 84%, 3-dB axial ratio (AR) bandwidths of 21% and 22%, and antenna gains of over 54 and 43 dBic are obtained for CNSS B3 and B1 bands, respectively Reasonable consistency is achieved between measured and simulated results of reflection coefficients, ARs, and radiation patterns

Design a single band microstrip patch antenna at 60 GHz millimeter wave for 5G application

Abstract: This proposed paper, a single band microstrip patch antenna for 5G wireless application is presented. This proposed antenna is suitable for the millimeter wave frequency. The single band antenna consist of new H slot and E slot loaded on the radiating patch with the 50 ohms microstrip line feeding used. This single band antenna is simulated on a Rogers RT5880 dielectric substrate have relative permittivity 2.2, loss tangent 0.0009, and height 1.6mm. The antenna is simulated by Electromagnetic simulation, computer software technology Microwave studio. The proposed single band antenna and simulated result on return loss, VSWR, surface current and 3D radiation pattern is presented. The simulated antenna shows the return loss −40.99dB at 60 GHz millimeter wave 5G wireless application presented.

Planar Microstrip Ring Resonators for Microwave-Based Gas Sensing: Design Aspects and Initial Transducers for Humidity and Ammonia Sensing.

Abstract: A planar microstrip ring resonator structure on alumina was developed using the commercial FEM software COMSOL. Design parameters were evaluated, eventually leading to an optimized design of a miniaturized microwave gas sensor. The sensor was covered with a zeolite film. The device was successfully operated at around 8.5 GHz at room temperature as a humidity sensor. In the next step, an additional planar heater will be included on the reverse side of the resonator structure to allow for testing of gas-sensitive materials under sensor conditions.

Design Approach to a Novel Dual-Mode Wideband Circular Sector Patch Antenna

Abstract: A design approach to a novel wideband circular sector patch antenna is proposed. Design guidelines are laid down based on an approximate 1.5-wavelength, multimode magnetic dipole, and the cavity model. Then, the flared angle of the circular sector patch and the corresponding usable resonant modes for wideband radiation are determined. It is demonstrated that the resonant TM4/3,1 and the TM8/3,1 modes within a 270° circular sector patch radiator can be simultaneously excited, perturbed, and employed to form a wideband unidirectional radiation characteristic with two resonances. Prototype antennas are designed and fabricated to experimentally validate the dual-resonant wideband property on a single-layered substrate. It is further demonstrated that the antenna designed on a 5-mm-thick air substrate exhibits an available radiation bandwidth (ARB) of 14.5%, while the printed one designed on a 2-mm-thick modified Teflon substrate exhibits an ARB of 6.5%. It is evidently validated that the proposed approach can be employed to effectively enhance the operational bandwidth of microstrip patch antennas without increasing antenna profile, inquiring multiple radiators or employing reactance compensation techniques.

Broadband Printed-Circuit-Board Characterization Using Multimode Substrate-Integrated- Waveguide Resonator

Abstract: Broadband printed-circuit-board characterization using a multimode substrate-integrated-waveguide (SIW) resonator is proposed and investigated in this paper. The resonator sample is fed by two closed rectangular waveguides through two coupling slots positioned at two ends of the cavity. A series of TE $_{\mathrm {10}{k}}$ resonant modes with large mode index can be excited sequentially in the cavity. This design is able to perform an effective control of the frequency interval ( $\Delta f$ ) between two neighboring modes. Besides, $\Delta f$ approaches to be a constant with a large mode index $k$ . This feature is important to test dielectric materials at small and approximately uniform frequency intervals. The detailed design process is introduced to synthesize the dimensions of the resonator sample and the feeding structure for a given operation frequency band. As an example, the Taconic TLY-5 substrate is measured at $Ka$ -band firstly to validate the accuracy of this method. Two types of samples with different thicknesses are fabricated and tested to calibrate the conductor loss. After that, this SIW multimode measurement is employed to accurately test the same substrates over the whole $W$ -band with approximately uniform frequency intervals. This task cannot be implemented by conventional resonance methods based on microstrip lines because of the selection of resonant modes and the radiation leakage.

Experimental Synthetic Aperture Radar With Dynamic Metasurfaces

Abstract: We investigate the use of a dynamic metasurface as the transmitting antenna for a synthetic aperture radar (SAR) imaging system. The dynamic metasurface consists of a 1-D microstrip waveguide with complementary electric resonator (cELC) elements patterned into the upper conductor. Integrated into each of the cELCs are two diodes that can be used to shift each cELC resonance out of band with an applied voltage. The aperture is designed to operate at $K$ -band frequencies (17.5–20.3 GHz). We experimentally demonstrate imaging with a fabricated metasurface aperture using well-known SAR modalities, showing image quality comparable to traditional antennas. The agility of this aperture allows it to operate in spotlight and stripmap SAR modes, as well as in a third modality inspired by computational imaging strategies. We describe the dynamic metasurface antenna’s operation in detail, demonstrate high-quality imaging in both 2-D and 3-D, and examine various tradeoffs governing the integration of dynamic metasurfaces in the future SAR imaging platforms.

Design of a Phased Array in Triangular Grid With an Efficient Matching Network and Reduced Mutual Coupling for Wide-Angle Scanning

Abstract: In this paper, a wide-scan angle planar patch phased array is proposed. The proposed array is composed of wideband probe-fed microstrip patches placed $0.087\lambda _{h} (\lambda _{h}$ is the wavelength of highest frequency) above individual ground planes and interlaced with parasitic decoupling walls. In order to cancel the feed probe inductance, the array elements comprise additional degrees of freedom to introduce controllable capacitance. Concurrently, individual ground planes and parasitic decoupling walls are proposed as an effective structure to considerably increase the E-plane scanning angle of the phased array by reducing the magnitude of near-field mutual coupling. A 544-element phased array prototype of the proposed element was designed, manufactured, and validated experimentally. The experimental results agree well with the numerical simulation ones and indicate effectiveness of the proposed design for mutual coupling reduction and wide-angle scanning. Because of the modifications, the measured mutual coupling between adjacent elements is reduced to lower than −32 dB at the center frequency. The proposed phased array has almost a constant active input impedance (active VSWR less than 2 over 20% bandwidth) up to scan angle of 65° in E-plane and 60° in H-plane, with a realized gain reduction of about 3.5 dB.

A Dual-Polarized Pattern Reconfigurable Yagi Patch Antenna for Microbase Stations

Abstract: A two-port pattern reconfigurable three-layered Yagi-Uda patch antenna with ±45° dual-polarization characteristic is presented. A driven patch (DP) and two large parasitic patches (LPPs) are printed on the top side of the middle layer, and the middle and bottom layers share a common metal ground. Two microstrip feedlines printed orthogonally on the bottom side of the bottom layer are used to feed the DP through two H-shaped slots etched in the ground. The LPPs are connected to/disconnected from the ground controlled by switches. By adjusting the connection states of the LPPs, one wide-beam mode and three narrow-beam modes can be obtained in both polarizations. A small parasitic patch is printed on the top side of the top layer to improve the pattern coherence of the two polarizations. This antenna is studied by both simulation and measurement. The measured common bandwidth of the four modes in both polarizations is 3.32–3.51 GHz, and the isolations between two polarizations in all the modes are higher than 20 dB. The low-profile antenna is very suitable for microbase-station applications.

Transparent and Nontransparent Microstrip Antennas on a CubeSat: Novel low-profile antennas for CubeSats improve mission reliability.

Abstract: This article reviews the development of some novel low-profile antennas for CubeSats. The integrated antennas were developed using microstrip-antenna technology, and the antennas were designed to be low profile while having minimal (or zero) blockage of the solar panels on the CubeSat. Two types of designs were investigated: 1) transparent antennas, which are placed above the solar panels (supersolar) and 2) nontransparent antennas, which are placed below the solar panels (subsolar). For past: using transparent metal and using a wire mesh design. The transparent metal indium tin oxide has a comparatively high sheet impedance, which makes an antenna design less efficient. Also, there is a tradeoff between conductivity and transparency [6]. However, a highly conductive thin mesh structure has demonstrated a reasonable efficiency and a high transparency [7]. The substrate must then also be transparent, e.g., glass or quartz.

Design of Compact Wide Stopband Microstrip Low-pass Filter using T-shaped Resonator

Abstract: In this letter, a compact microstrip low-pass filter (LPF) using T-shaped resonator with wide stopband is presented. The proposed LPF has capability to remove the eighth harmonic and a low insertion loss of 0.12 dB. The bandstop structure using stepped impendence resonator and two open-circuit stubs are used to design a wide stopband with attenuation level better than −20 dB from 3.08 up to 22 GHz. The proposed filter with −3-dB cutoff frequency of 2.68 GHz has been designed, fabricated, and measured. The operating of the LPF is investigated based on equivalent circuit model. Simulation results are verified by measurement results and excellent agreement between them is observed.