Showing papers on "Return loss published in 2014"

Wide-Band Slot Antenna Arrays With Single-Layer Corporate-Feed Network in Ridge Gap Waveguide Technology

Abstract: Single-layer, wideband, and low-loss corporate-feed networks for slot antenna arrays are described. The antenna is built using ridge gap waveguide technology, formed between two parallel metal plates without the requirements of electrical contact between these plates. The corporate-feed network is realized by a texture of pins and a guiding ridge in the bottom plate, and the radiating slots are placed in the smooth top plate. The paper describes two test antennas: a 4 $\,\times\,$ 1 linear slot array and a 2 $\,\times\,$ 2 planar slot array. Both have been fabricated and tested at Ku- band. The linear array shows more than 20% bandwidth and the 2 $\,\times\,$ 2 array shows a bandwidth of 21% for 10-dB return loss. There are good agreements between measured and simulated patterns for both antennas. Measured gain for the planar array is found to be at least 12.2 dBi over 12–15 GHz band.

A low-cost microwave rotary joint

Abstract: A simple and cheap coaxial microwave rotary joint covering frequencies from 1 to 21 GHz is described Measured typical insertion loss is 07 dB, return loss stays better than 10 dB and the rotating torque requirement is 26 mNm Maximum variation of attenuation as a function of rotating angle is 05 dB Operation up to 37 GHz has been tried with loss values around 2 dB, typical

Slow-Wave Substrate Integrated Waveguide

Abstract: This paper describes a new concept of substrate integrated waveguide (SIW): a slow-wave substrate integrated waveguide (SW-SIW). Compared to a conventional SIW, the proposed topology requires a double-layer substrate with a bottom layer including internal metallized via-holes connected to the bottom conductive plane. The slow-wave effect is obtained by the physical separation of electric and magnetic fields in the structure. Electromagnetic simulations show that this topology of SIW allows decreasing the longitudinal dimension by more than 40% since the phase velocity is significantly smaller than that of a classical SIW. Simultaneously, the lateral dimension of the waveguide is also reduced. By considering a double-layer technology, SW-SIWs exhibiting a cutoff frequency of 9.3 GHz were designed, fabricated, and measured. The transversal dimension and the phase velocity of the proposed SW-SIW are both reduced by 40% as compared to a classical SIW designed for the same cutoff frequency, leading to a significant surface reduction. Moreover, an original kind of taper is proposed to achieve a good return loss when the SW-SIW is fed by a microstrip transmission line.

Bandwidth Enhancement of SIW Horn Antenna Loaded With Air-Via Perforated Dielectric Slab

Abstract: A substrate integrated waveguide (SIW) horn antenna loaded with air-via perforated dielectric slab for bandwidth enhancement is proposed in this letter. The narrow impedance bandwidth of the planar horn antenna is mainly resulting from the discontinuity between the substrate and air. By simply drilling air-vias with different diameters in the substrate extended from the horn aperture, a smooth transition from substrate to air can be achieved, which can enhance the impedance bandwidth of the antenna in much degree. Measured results show that the enhanced impedance bandwidth of 40% from 16 to 24 GHz is obtained with the return loss |S11| below -10 dB. In addition, stable radiation patterns are observed over the entire operating band.

Planar Dual-Mode Horn Array With Corporate-Feed Network in Inverted Microstrip Gap Waveguide

Abstract: The gap waveguide technology was recently introduced as an alternative to hollow waveguides and substrate integrated waveguides for millimeter-wave applications. This paper presents the design of a 4 x 4 planar dual-mode horn array with low loss corporate feed network realized by using an inverted microstrip gap waveguide. The dual-mode horns are compact and designed to reduce the power losses in grating lobes. It is because the diameters of the horn apertures are larger than two wavelengths to allow more space for the feed network and thereby lower conductive losses. The measurements show very good agreement with simulations, with 10% bandwidth of the return loss, 25 dBi realized gain and about 60% aperture efficiency.

New Wideband Transition From Microstrip Line to Substrate Integrated Waveguide

Abstract: A new wideband transition from microstrip line to substrate integrated waveguide (SIW) is introduced. Unlike most transitions that show reduced return loss over significant parts of a regular waveguide band, the presented configuration achieves return losses better than 30 dB in standard waveguide frequency bands from X to E. The new aspect of this transition is the addition of two vias to the widely used microstrip taper transition. Moreover, the influence of the substrate height is demonstrated. The results in each frequency band are compared with the data for the regular microstrip taper alone. A design formula for the placement of the vias and taper dimensions is presented and demonstrated to provide excellent results. The structures are simulated and optimized with CST Microwave Studio. Measurements performed on a Ku-band back-to-back prototype transition demonstrate a minimum return loss of 26.05 dB and maximum insertion loss of 0.821 dB over the entire Ku-band, thus validating the design approach.

Compact Circularly Polarized Asymmetrical Fractal Boundary Microstrip Antenna for Wireless Applications

Abstract: Compact fractal boundary microstrip antenna is proposed for circular polarization (CP). By replacing the sides of a square patch with asymmetrical prefractal curves, two orthogonal modes are excited for CP operation. The structure is asymmetric along the principal axes (x, y). The indentation parameter of the fractal boundary curve is optimized to design compact CP antennas. Experimental results show that 10-dB return loss and 3-dB axial-ratio bandwidths of the proposed fractal boundary Ant 2 are 162 and 50 MHz, respectively, at operating frequency of around 2540 MHz. Results show that an excellent CP is achieved with a single probe feed, besides reduction in the antenna size by applying fractal boundary concept.

Compact Eight-Band Frequency Reconfigurable Antenna for LTE/WWAN Tablet Computer Applications

Abstract: A novel eight-band LTE/WWAN frequency reconfigurable antenna for tablet computer applications is proposed in this communication. With a small dimension of 40 × 12 × 4 mm3, the proposed antenna comprises a loop feeding strip and a shorting strip in which a single-pole four-throw RF switch is embedded. The RF switch is used to change the resonant modes of lower band among four different working states, so that the antenna can provide a multiband operation of LTE700/GSM850 /900/1800/1900/UMTS2100/LTE2300/2500 with return loss better than 6 dB. Reasonably good radiating efficiency and antenna gain are also achieved for the practical tablet computer.

300-GHz Step-Profiled Corrugated Horn Antennas Integrated in LTCC

Abstract: This paper presents 300-GHz step-profiled corrugated horn antennas, aiming at their integration in low-temperature co-fired ceramic (LTCC) packages. Using substrate integrated waveguide technology, the cavity inside the multi-layer LTCC substrate and a surrounding via fence are used to form a feeding hollow waveguide and horn structure. Owing to the vertical configuration, we were able to design the corrugations and stepped profile of horn antennas to approximate smooth metallic surface. To verify the design experimentally, the LTCC waveguides and horn antennas were fabricated with an LTCC multi-layer process. The LTCC waveguide exhibits insertion loss of 0.6 dB/mm, and the LTCC horn antenna exhibits 18-dBi peak gain and 100-GHz bandwidth with more than 10-dB return loss. The size of the horn antenna is only 5×5×2.8 mm 3 , which makes it easy to integrate it in LTCC transceiver modules.

Design of Compact 4 × 4 UWB-MIMO Antenna with WLAN Band Rejection

Abstract: A compact 4 × 4 UWB-MIMO antenna with rejected WLAN band employing an electromagnetic bandgap (EBG) structure is presented in this paper. The MIMO antenna is electrically small (60 mm × 60 mm), printed on a FR4_epoxy substrate with the dielectric constant of 4.4 and a thickness of 1.6 mm. A mushroom-like EBG structure is used to reject the WLAN frequency at 5.5 GHz. In order to reduce the mutual coupling of the antenna elements, a stub structure acting as a bandstop filter is inserted to suppress the effect of the surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than −10 dB in a bandwidth ranging from 2.73 GHz to 10.68 GHz, which entirely covers UWB frequency band, which is allocated from 3.1 to 10.6 GHz. The antenna also exhibits a WLAN band-notched performance at the frequency band of 5.36–6.34 GHz while the values of all isolation coefficients are below −15 dB and the correlation coefficient of MIMO antenna is less than −28 dB over the UWB range. A good agreement between simulation and measurement is shown in this context.

Dual Band-Notch UWB Antenna With Single Tri-Arm Resonator

Abstract: A microstrip line-fed planar antenna with dual notched bands is designed and prototyped for ultrawideband (UWB) communication applications. The dual band-notch characteristic is achieved by etching a single tri-arm resonator below the patch. The simulated and experimental results show that the designed antenna has achieved a wide bandwidth (return loss ≤ -10 dB) ranging from 2.98 to 10.76 GHz with two notched bands operating at 3.5 and 5.5 GHz. The proposed antenna uses only one simple filter element to create and control dual notched bands, which give it advantages over the recently proposed band-notch antennas. In addition, the designed antenna achieved a good gain and exhibits omnidirectional radiation patterns except at notched bands, which make it a suitable candidate for UWB applications.

CPW Center-Fed Single-Layer SIW Slot Antenna Array for Automotive Radars

Abstract: A compact co-planar waveguide (CPW) center-fed substrate-integrated-waveguide (SIW) slot antenna array is proposed to achieve narrow H-plane beamwidth and low sidelobe levels for automotive radars such as across-the-road (ATR) radar. The antenna consists of an array of SIW slot elements, a CPW-SIW transition, and a CPW power divider. A new type of CPW-SIW transition is proposed to minimize the blockage aperture of the slot antenna array for suppressing the sidelobe levels of the array. A parallel center feeding configuration is applied to avoid beam squinting. The antenna prototype printed onto a single-layer Rogers 5880 is with 32 ×4 slot elements and an overall size of 195 mm×40 mm×0.79 mm. Measured results show that the proposed antenna exhibits a gain of > 22.8 dBi, an efficiency of > 67%, a return loss of > 10 dB, a sidelobe level of <;-21 dB, and a fixed boresight beam of <;4.6° in H-planes over 24.05-24.25 GHz, suitable for ATR radar.

Wideband Single-Layer 90 $^{\circ}$ Phase Shifter Using Stepped Impedance Open Stub and Coupled-Line With Weak Coupling

Abstract: This letter proposes a novel design approach of wideband 90 ° phase shifter, which comprises a stepped impedance open stub (SIOS) and a coupled-line with weak coupling. The result of analyses demonstrates that the bandwidths of return loss (RL) and phase deviation (PD) can be expanded by increasing the impedance ratio of the SIOS and the coupling strength of the coupled-line. For RL > 10 dB, insertion loss (IL) 1.1 dB, and PD of ±5°, the fabricated microstrip single-layer phase shifter exhibits bandwidth of 105% from 0.75 to 2.4 GHz.

Wideband harmonic rejection filtenna for wireless power transfer

Abstract: Two novel, compact, simple 2nd and 3rd harmonic rejection coplanar waveguide (CPW) feeding mechanisms for a 5.8 GHz rectenna are proposed. Both of them make use of the CPW compact microstrip resonant cell (CMRC). In the first topology, the blockage is realized by a CMRC in combination with a U-slot. In the second topology a pair of strongly coupled CMRCs is optimized. Both these new feeding mechanisms are realized in prototypes and experimentally validated, first in two back-to-back configurations, and then in combination with two CPW fed wideband monopole antennas. The measured antenna return loss at the 2nd and 3rd harmonic is in the order of 0.5 dB and 1.5 dB, respectively, which corresponds to a return loss suppression of about 4 -5 dB compared to a reference monopole antenna. Both antennas reach an 18% 10 dB return loss bandwidth, which is the highest working bandwidth reported in literature for harmonic rejection antennas. Bandwidth could become an issue when wireless power transfer systems would be implemented with a reconfigurable working frequency in order to minimize interference with local telecom equipment.

Design of novel compact anti-stiction and low insertion loss RF MEMS switch

Abstract: A novel torsional RF MEMS capacitive switch design on silicon substrate is presented. The optimized switch topology such as reduction in up-state capacitance results in insertion loss better than ź0.1 dB till 20 GHz. Off to on state capacitance ratio is also improved by 18 fold and isolation is better than ź43 dB at 9.5 GHz. The achieved on state return loss is ź38 dB as compared to ź21 dB at 9.5 GHz. An optimized reduction in contact area and use of floating metal layer increases the switching speed from 56 to 46 μsec. It also increases the switch reliability by alleviating the stiction.

Wideband Harmonic Rejection Filtenna for Wireless Power Transfer

Abstract: Two novel, compact, simple 2nd and 3rd harmonic rejection coplanar waveguide (CPW) feeding mechanisms for a 5.8 GHz rectenna are proposed. Both of them make use of the CPW compact microstrip resonant cell (CMRC). In the first topology, the blockage is realized by a CMRC in combination with a U-slot. In the second topology a pair of strongly coupled CMRCs is optimized. Both these new feeding mechanisms are realized in prototypes and experimentally validated, first in two back-to-back configurations, and then in combination with two CPW fed wideband monopole antennas. The measured antenna return loss at the 2nd and 3rd harmonic is in the order of 0.5 dB and 1.5 dB, respectively, which corresponds to a return loss suppression of about 4 -5 dB compared to a reference monopole antenna. Both antennas reach an 18% 10 dB return loss bandwidth, which is the highest working bandwidth reported in literature for harmonic rejection antennas. Bandwidth could become an issue when wireless power transfer systems would be implemented with a reconfigurable working frequency in order to minimize interference with local telecom equipment.

Tunable Bandpass Filter With Two Adjustable Transmission Poles and Compensable Coupling

Abstract: In this paper, tunable microstrip bandpass filters with two adjustable transmission poles and compensable coupling are proposed. The fundamental structure is based on a half-wavelength (λ/2) resonator with a center-tapped open-stub. Microwave varactors placed at various internal nodes separately adjust the filter's center frequency and bandwidth over a wide tuning range. The constant absolute bandwidth is achieved at different center frequencies by maintaining the distance between the in-band transmission poles. Meanwhile, the coupling strength could be compensable by tuning varactors that are side and embedding loaded in the parallel coupled microstrip lines (PCMLs). As a demonstrator, a second-order filter with seven tuning varactors is implemented and verified. A frequency range of 0.58-0.91 GHz with a 1-dB bandwidth tuning from 115 to 315 MHz (i.e., 12.6%-54.3% fractional bandwidth) is demonstrated. Specifically, the return loss of passbands with different operating center frequencies can be achieved with same level, i.e., about 13.1 and 11.6 dB for narrow and wide passband responses, respectively. To further verify the etch-tolerance characteristics of the proposed prototype filter, another second-order filter with nine tuning varactors is proposed and fabricated. The measured results exhibit that the tunable fitler with the embedded varactor-loaded PCML has less sensitivity to fabrication tolerances. Meanwhile, the passband return loss can be achieved with same level of 20 dB for narrow and wide passband responses, respectively.

Development of a compact rectenna for wireless powering of a head-mountable deep brain stimulation device

Abstract: Design of a rectangular spiral planar inverted-F antenna (PIFA) at 915 MHz for wireless power transmission applications is proposed. The antenna and rectifying circuitry form a rectenna, which can produce dc power from a distant radio frequency energy transmitter. The generated dc power is used to operate a low-power deep brain stimulation pulse generator. The proposed antenna has the dimensions of 10 mm $\times\,$ 12.5 mm $\times\,$ 1.5 mm and resonance frequency of 915 MHz with a measured bandwidth of 15 MHz at return loss of ${-}{\rm 10}~{\rm dB}$ . A dielectric substrate of FR-4 of $\varepsilon _{r}=4.8$ and $\delta=0.015$ with thickness of 1.5 mm is used for both antenna and rectifier circuit simulation and fabrication because of its availability and low cost. An L-section impedance matching circuit is used between the PIFA and voltage doubler rectifier. The impedance matching circuit also works as a low-pass filter for elimination of higher order harmonics. Maximum dc voltage at the rectenna output is 7.5 V in free space and this rectenna can drive a deep brain stimulation pulse generator at a distance of 30 cm from a radio frequency energy transmitter, which transmits power of 26.77 dBm.

A Dual Circularly Polarized Waveguide Antenna With Bidirectional Radiations of the Same Sense

Abstract: A dual circularly polarized waveguide antenna with bidirectional radiations of the same sense is proposed in this communication. Bidirectional circular polarization (Bi-CP) of the same sense was obtained by two identical rectangular metal slices installed on one lateral side of the waveguide with an intersection angle of 45°. These two metal slices were horizontally perpendicular to each other and vertically spaced by a quarter guided wavelength. A rat-race coupler was employed to excite the two metal slices with the same amplitude, but with a 0° or 180° phase difference depending on the selection of two inputs. One sense of Bi-CP was realized when the two metal slices were fed in phase and the opposite sense of Bi-CP could be obtained when they were fed out of phase. A prototype for 2.4-GHz WLAN application was tested to verify our design. The measured common bandwidth for 10-dB return loss and 3-dB axial ratio at the two feed ports was 230 MHz (9.6%, 2.29-2.52 GHz) and 210 MHz (8.6%, 2.35-2.56 GHz), respectively. The measured isolation between the two feed ports was better than 30 dB over the whole operating band.

Compact in-phase power divider integrated filtering response using spiral resonator

Abstract: A compact in-phase power divider with filtering response is presented in this study. Spiral resonators are meant to realise compact size and bandpass-filtering response. To improve the frequency selectivity of the presented power divider, a source–load cross-coupling is introduced by placing input and output coupling lines. An in-phase power divider with passband-filtering response has been designed, fabricated and measured. The measured return loss and insertion loss of the fabricated power divider are 22 and 1.3 dB at 2.45 GHz, respectively. The 3 dB operating bandwidth of the fabricated power divider is 175 MHz. The total area of the fabricated power divider is 0.15λ g × 0.3λ g. The measured results verify the predicted attractive features.

A compact broadband microstrip patch antenna with defective ground structure for C-Band applications

Abstract: A novel design of a circular patch antenna having defected ground structure is presented in this communication. The antenna is designed for C-band applications. A wide bandwidth of 60.3% (4.04–7.28) GHz is obtained in the C-band frequency range 4–8 GHz. It is also found through parametric analysis that shape and dimensions of the finite ground plane and slots in the patch are the key factors in improving the bandwidth of the proposed geometry. The antenna is fabricated using FR-4 substrate and parameters like return loss, VSWR and input impedance are measured experimentally.

Substrate Integrated Waveguide (SIW) to Microstrip Transition at X-Band

Abstract: Substrate integrated waveguide (SIW) is a new form of transmission line. It facilitates the realization of non- planar (waveguide based) circuits into planar form for easy integration with other planar (microstrip) circuits and systems. This paper describes the design of an SIW to microstrip transition. The transition is broadband covering the frequency range of 8 - 12GHz. The measured in-band insertion loss is below 0.6dB while the return loss is less than 10dB. The circuit is simulated in HFSS and results are measured on vector network analyzer (VNA).

Wideband rectangular printed monopole antenna for circular polarisation

Abstract: A wideband printed rectangular monopole antenna for circularly polarised wave is proposed. The radiation characteristics of the wideband circular polarisation are achieved by designing the antenna asymmetrically. With simulations, the relationships between the antenna's geometrical parameters and the antenna's characteristics (axial ratio of circularly polarised wave and return loss) are clarified. The operational principle for wideband circular polarisation is explained by the simulated electric current distributions. Moreover, the simulated axial ratio, return loss, radiation patterns and gain are compared with the measured results. The simulated and measured bandwidths (3 dB axial ratio with a 10 dB return loss) are ∼56.2% (1.78–3.17 GHz) and 51.4% (1.82–3.08 GHz), respectively.

Three-Pole Tunable Filters With Constant Bandwidth Using Mixed Combline and Split-Ring Resonators

Abstract: A novel three-pole tunable bandpass filter using mixed varactor-tuned combline and split-ring resonators is proposed in this letter. A tuning range of 1.1-1.88 GHz (70.9%) with an almost constant 3 dB absolute bandwidth of 90 ±8 MHz (7.4%-4.4% fractional bandwidth) is demonstrated. The filter shows its insertion loss varying from 6.8 dB to 4.3 dB and return loss better than 13.5 dB within the tuning range. The rejection levels at both the lower and upper stopbands are > 30 dB. The measured results show good agreement with the simulated ones.

Design of Microstrip Antenna for 2.4/5.8 GHz RFID Applications

Abstract: In this paper, a novel design of dual-band monopole antenna for radio frequency identification (RFID) systems is proposed. The proposed antenna is designed to operate at 2.45 GHz and 5.8 GHz (ISM frequency range) and it is fabricated on an FR4 substrate with dielectric constant of 4.4. The measured impedance bandwidth for l0dB return loss is from 1.82 to 2.92 GHz (49%) and 5.53 to 6.36 GHz (13.0%), covering the 2.4/5.8 GHz RFID operating bands.

Miniaturized 3-bit Phase Shifter for 60 GHz Phased-Array in 65 nm CMOS Technology

Abstract: The letter presents a compact 3-bit 90 ° phase shifter for phased-array applications at the 60 GHz ISM band (IEEE 802.11ad standard). The designed phase shifter is based on reflective-type topology using the proposed reflective loads with binary-weighted digitally-controlled varactor arrays and the transformer-type directional coupler. The measured eight output states of the implemented phase shifter in 65 nm CMOS technology, exhibit phase-resolution of 11.25 ° with an RMS phase error of 5.2 °. The insertion loss is 5.69 ± 1.22 dB at 60 GHz and the return loss is better than 12 dB over 54-66 GHz. The chip demonstrates a compact size of only 0.034 mm2.

A 1.1 THz micromachined on-wafer probe

Abstract: This paper presents a micromachined probe for on-wafer measurements of circuits in the WR-1.0 waveguide band (0.75 - 1.1 THz). The probe shows a measured insertion loss of less than 7 dB and return loss of greater than 15 dB over most of the band. These are the first reported on-wafer measurements above 1 THz.

Compact EBG Structures for Reduction of Mutual Coupling in Patch Antenna MIMO Arrays

Abstract: Electromagnetic band gap (EBG) structures are usually realized by periodic arrangement of dielectric materials. These periodic structures can help in the reduction of mutual coupling in array antennas. In this paper a new arrangement of EBG structures is presented for reducing mutual coupling between patch antenna MIMO arrays. The patch antennas operate at 5.35 GHz which is defined for wireless application. Here 2 × 5 EBG structures are used to reduce mutual coupling more than 20 dB. The total size of the antenna is 36 mm × 68 mm × 1.6 mm. So it is more compact in than pervious research. Experimental results of return loss and antenna pattern have been presented for 5.4 GHz and compared with HFSS simulation results. Also the EBG structures have been designed with numerical modeling and dispersion diagram. New EBG model is compared with conventional EBG model, and equivalent circuit model is given for new structure.

TEM Horn Antenna Loaded With Absorbing Material for GPR Applications

Abstract: A novel exponentially tapered TEM horn antenna is presented. It is fed directly by a coax through a compact transition section and possesses a wide bandwidth, good radiation characteristic, and easy integration with microwave circuits. Two specially tapered metal flares have been designed to make a wideband characteristic and reduce the reflection. To overcome aperture reflections at low frequencies and unbalanced aperture field at higher frequencies, an arc surface is added at the end of the flare plates, and an absorbing material is loaded on the outer surface of the flare section. Measured results show that the presented antenna has a wide bandwidth from 0.83 to more than 12.8 GHz under a return loss <;-10 dB, small input reflection, a moderate gain from 0 dBi at 0.83 GHz to 10 dBi at 12 GHz, and a good radiation characteristics in the time domain, which can be suitable for ground penetrating radar (GPR) applications.

An Optimized Isolation Network for the Wilkinson Divider

Abstract: We propose an isolation network to simultaneously improve the input return loss, output return loss and isolation of the Wilkinson power divider in a wide bandwidth. The required even mode and odd mode reflection coefficients of the isolation network are calculated. Constructed even and odd mode circuits are combined to give the desired isolation network. Analytical expressions for the optimal component values for a single-section divider are given. Compared with the single-section Wilkinson divider, the final design can triple the bandwidth for an input-output return loss and isolation of greater than 25 dB. Broadband characteristic is achieved without increasing the number of sections hence extra length and insertion loss are avoided. Wide operation bandwidth of the new divider is verified by experimental results. The proposed method can be applied to a two-section divider, also broadening its bandwidth.