Transmission Line Feed Research Articles

Tunable bandpass filter with low insertion loss based on electrically controlled liquid crystal

This paper presents a low loss electrically tunable bandpass filter based on liquid crystal. By utilizing structure of transmission line and direct-connected feeding lines without coupling gaps which eliminate mismatch and radiation losses, then the proposed filter gets a low insertion loss. And the tunability of the filter is realized by utilizing electrically controlled liquid crystal (LC) material as the substrate. In order to verify the design concept, a liquid crystal tunable prototype filter is designed, fabricated and measured. Measured results agree well with the simulated results. With no bias voltage applied, the filter operates at center frequency of 11.5GHz with fractional bandwidth of 11.3%. And with voltage tuning from 0V to 10V, the filter gets a tuning range of 500MHz and the insertion losses are 2–3.1dB, respectively.

A Rectangular Microstrip Patch Antenna for Wireless Communications Operates in Dual Band

A single layer substrate compact dual band rectangular micro-strip patch antenna with transmission line feeding is designed for Wireless Local Area Networks (WLAN) implementation. The desired antenna consists of a rectangular patch having two I-slots and a dielectric material with dielectric constant of 2.4. The use of cavity model with transmission line feed has the favor of low profile, high gain and wide bandwidth of the antenna. The antenna has overall size of 46.9 mm by 38.01 mm and gives bandwidth of about 90 MHz at resonance frequency of 2.45 GHz and that of 115 MHz at 4.1 GHz frequency with Defected Ground Structure (DGS). The antenna with DGS has return losses -21.25 dB at 2.45 GHz and -27.5 dB at 4.1 GHz where the gains are 6.70 dB for 2.45 GHz and 6.80 dB for 4.1 GHz. Finally the designed antenna has been simulated using Computer Simulation Technology (CST) microwave studio 2009 and it is comparable with manual computation results which are found to be suitable for WLAN applications.

Varactor-Tuned Compact Dual-Mode Tunable Filter With Constant Passband Characteristics

This paper presents a second-order Chebyshev constant fractional bandwidth (CFBW) tunable bandpass filter with compact size and frequency invariant-passband characteristics using tunable external quality factors. The filter is designed using a stub loaded dual-mode resonator and two sets of varactors for tuning the center frequency and the return loss level. The design is featured with the net-type filter of a short grounded-stub so that the CFBW property can be assured. In addition to the conventional design, a pair of varactors is included at the ends of feeding transmission lines to keep the external quality factors constant while tuning. Within the tunable range of the varactors, the proposed filter is tunable from 1.7 to 2.1 GHz with a 5% CFBW. The measurement results show a 20-dB return loss and insertion loss below 2.9 dB over the entire tuning range.

Harmonic Suppression Rectangular Patch Antenna with Circularly Polarized

The rectangular patch antenna with proximity coupling at 2.45 GHz is designed and printed on FR-4 substrate with dielectric constant 4.3 and loss tangent 0.019. The overall size of proposed antenna gives 36 % reduction of substrate area as compared to conventional designs. The symmetrical arm of inverted U-stub and U-slot embedded on the transmission feed line suppress harmonic signal effectively at second and third order with minimum reflection coefficients of –0.51 dB and -2.28 dB respectively while circularly polarization was obtained by corner truncated and U-slot on the patch element. The return loss is -23.95 dB at fundamental modes with gain 4.61 dB and axial ratio of 1.48 dB.

A two port UWB‐dual narrowband antenna for cognitive radios

ABSTRACTA two port ultra wideband(UWB) and dual narrowband antenna for cognitive radio(CR) applications is reported. In this letter an elliptical patch is used as an UWB sensing antenna which is coplanar waveguide (CPW)‐fed transmission line with elliptically tapered ground plane. A rectangular slot is etched from the radiating patch to integrate the narrow band communication antenna where basically the surface current density is effectively low. Within the slot a triangular monopole with meander line LC (inductance–capacitance) resonator in the feed helps to realize dual narrowband (NB) communication antenna. This proposed antenna is a potential candidate for cognitive radio application where the elliptical patch antenna covers the UWB frequency range (3.1–10.6 GHz) with stable radiation patterns for spectrum sensing and the triangular monopole with meander lines LC resonator in the feed behaves as dual band communication antenna with first band operating at WLAN 5.04 GHz (4.48–5.4 GHz) and second band operating at X band satellite communication at 7.6 GHz (7.4–7.76 GHz) with isolation less than −10 dB in the whole operating band between the two antenna ports. The prototype of the proposed antenna has been fabricated and its S‐parameters in terms of S11, S22, S21 as well as radiation patterns were measured that shows good agreement with simulated results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1973–1978, 2016

A Successive Geometric Segmentation Approach Applied to Double-Circuit Transmission Lines Fault Classification and Location

This paper presents a new approach to address both fault classification and location in double-circuit power transmission lines. Fault diagnosis is achieved by using an algorithm based on the successive geometric segmentation approach. The proposed technique is able to generate both the topology and the weighting of neural networks. The input parameters are the magnitudes of phase voltages and currents measured in only one bus of a double-end fed transmission line. In order to validate the methodology, a comprehensive dataset of cross-country faults was simulated using a mathematical model. The results indicate high accuracy rate to fault diagnosis in double-circuit transmission lines compared to other ANN-based approaches found in the literature.

Non-Foster Matching of a Resistively Loaded Vee Dipole Antenna Using Operational Amplifiers

A non-Foster matching network using negative impedance converters (NICs) is proposed for a resistively loaded vee dipole antenna (RVD). The RVD suffers from considerable reflection at the feeding transmission line at low frequencies because of its large negative input reactance. To reduce the reflection, a non-Foster matching network, which is composed of NICs based on operational amplifiers (op-amps), is proposed. For the practical design, the effects of input parasitic capacitances of the op-amp and the finite open-loop gain are considered. The stability analysis is performed according to the Barkhausen stability criterion. The non-Foster matching network is implemented with the RVD as a load. The measured impedance demonstrates that the matching network significantly reduces the input reactance of the RVD. In the time-domain analysis, the matched RVD is shown to reflect significantly less incident pulse. A target was imaged through a series of radar echo experiments. The images show that the non-Foster matching network enhances the performance of the RVD as an antenna for the ground-penetrating radar.

Flexible printed chipless RFID tag using metamaterial–split ring resonator

An 8-bit passive chipless RFID using metamaterial structure with dimension of 25 × 50 mm which operates between 3.4 and 7.4 GHz is proposed. The chipless RFID is designed using complementary split ring resonator (SRR) with a transmission line feeding network of 50 Ω. The modified complementary split ring resonator (MCSRR) is located at the backside of the substrate. The MCSRR has narrow bandwidth which can maximize the amount of bit capacity. To enhance the bit capacity, the frequency shifting is introduced by the allocation of bit conditions (00, 01, 10 and 11) at the specific resonance frequency. The polyethylene terephthalate material with e r = 3.0 and tan δ = 0.002 is a suitable candidate for body identification due to the flexibility and the robustness of the material.

Bandpass filter based on novel‐coupled half‐wavelength microstrip ring resonators

ABSTRACTA microstrip bandpass filter (BPF) based on centre‐coupled cylindrical microstrip ring resonator (MRR) for wireless application in ISM frequency band of applications is presented. The proposed is a combination of two identical bended half‐wavelength (λ/2) MRR, and centre‐coupled by an end‐coupled transmission feed line. The equivalent circuits of the MRR, the end‐coupled feed, and the effects of various spacing between them were investigated based on the even‐ and odd‐mode theory. The mechanism of resonant mode splitting is investigated with the possibility of enhancing the coupling effect, while suppressing spurious resonances in order to achieve sharp rejection skirts. Findings indicates that the proposed equivalent circuit are influenced by capacitances due to resonator – transmission feed line gap (d), the gap between each ring (g), the feed line gap (i), the radius of MRR (r), and the resonator head (m). The operation mechanism of the structure was investigated first theoretically to the intent of design a circuit model, then using numerical 3D EM based on finite integration technique (FIT) method, and finally, through 2D equivalent circuit modeller. The derived equivalent circuit model have been validated both by analytical formulae and numerical simulations. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:911–918, 2016

Design and characterization of a resonator-based metamaterial and its sensor application using microstrip technology

Design of a metamaterial based on an S-shaped resonator surrounded by a ground frame and excited by using a feeding transmission line on microstrip technology is presented. Since the resonator, ground frame, and its excitation mechanism are all realized on a microstrip, its characterization can be carried out using common laboratory equipment without needing any waveguide components or plane-wave-illumination techniques. The structure presented here may be realized on any microstrip and does not require special materials. The resonator and ground frame are both on the same side of the microstrip, thus the proposed topology may also be populated with active and passive microwave components, and hybrid active, passive, or reconfigurable microwave circuits may be realized. In metamaterial designs that require plane wave illumination, usually many numbers of periodic unit cells are needed; however, in our design, only one cell is capable of achieving metamaterial properties. The constitutive parameters of the metamaterial are retrieved and compared to demonstrate the agreement between simulations and measurements. The proposed topology is also demonstrated in a sensor application, where simulated and measured results agree well. Thus, it can be realized using standard microwave technology and used for numerous applications where metamaterial properties are needed.

A Tunable Metamaterial Resonator Using Varactor Diodes to Facilitate the Design of Reconfigurable Microwave Circuits

In this brief, we designed, constructed, and analyzed a frequency-tunable metamaterial resonator. The proposed design consists of an S-shaped resonator, a ground frame, and a feeding transmission line. First, the structure is designed as a nontunable resonator and then tunability is achieved by employing varactor diodes. In order to verify and demonstrate its tunable metamaterial properties, reflection and transmission parameters, group delay, electric and magnetic field distributions, and permittivity and permeability at each tuned frequency were analyzed. Simulation and measured results agree well and show that a high transmission and reflection peak occurs at each resonance frequency that may be tuned with the applied control voltage. Therefore, the proposed tunable metamaterial resonator may be used to realize reconfigurable microwave circuits such as reflection/transmission filters, antennas, and sensors, and for achieving flexibility in many other microwave circuits.

Wideband Circular Polarization Reconfigurable Antenna

This communication introduces a polarization reconfigurable wideband circularly polarized (CP) antenna, which consists of four radiating arms connected to a reconfigurable feeding network. The four radiating arms excited by the feeding network are able to generate wideband CP waves with bidirectional radiation patterns in free space. In order to increase the gain and obtain a broadside radiation pattern, the proposed antenna is placed above a metallic reflector with the distance of quarter wavelength at the center frequency. In addition, polarization reconfigurability is realized by utilizing PIN diodes in the feeding transmission lines such that left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) modes can be selectively excited by controlling the on / off states of the PIN diodes. The proposed antenna exhibits a wide impedance bandwidth of 80% and an overlapped axial ratio (AR) bandwidth of 23.5% for both modes. The antenna gain is stable across the operating bandwidth with the peak gain of 4.8 dBic. The antenna has a wide AR beamwidth of 90°. The presented work is suitable for GPS, CNSS, or RFID applications.

Performance Comparison of Differential Evolution, Particle Swarm Optimization and Genetic Algorithm in the Design of Circularly Polarized Microstrip Antennas

Performance evaluation of evolutionary optimization techniques is done with respect to the design of circularly polarized microstrip antennas. The optimization techniques include conventional differential evolution, particle swarm optimization and genetic algorithm along with their advanced schemes. The optimization is done for impedance matching over a predefined frequency range, circular polarization, and high gain at a center frequency. The control parameters of all the algorithms are tuned using meta-level particle swarm optimization algorithm. Three cases are considered with three conventional feeding techniques, namely probe feed, transmission line feed, and the cross-aperture coupled feed. A fuzzified cost function is developed for optimization to ensure proper outcome from each optimization algorithm. The antenna parameters obtained from the algorithm producing best results are fabricated and their performances measured.

Radiation-rejection band inserted dual-band antenna using a split ring resonator for beyond 4G applications

We propose a very simple but effective method to switch a single-band antenna into a dual-band antenna by inserting a narrow radiation-prohibited band in the middle of the single pass band. To insert the radiation-rejection band, we intentionally induce strong resonance on a metamaterial-motivated split ring resonator (SRR) by placing it near a signal feeding transmission line of a proximity-coupled microstrip patch antenna, which blocks out flow of electromagnetic waves through the line. To maximize the blockage, we cut the SRR into a quadrangular loop that is exactly interlocked with the two sides of the right-angled microstrip line. Consequently, we show that we can split one pass band into two separated pass bands with an inserted sharp stop band in-between. Good agreements between the prediction and the measurement prove the validness of our approach. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:961–965, 2014

T-SHAPED ANTENNA LOADING T-SHAPED SLOTS FOR MULTIPLE BAND OPERATION

The method of a T-shaped antenna loading T-shaped slots for multiple band operation is presented in this paper. Inspired by the fractal antenna, the proposed method is intended to be used for designing multiple band antennas. Through loading T-shaped slots in the terminals of a T- shaped antenna, dual or triple operating bands can be achieved. In order to validate the feasibility of this method, this type of antenna is designed and simulated. The antennas are respectively fed by two difierent feeding transmission lines (microstrip transmission line and coplanar waveguide (CPW) transmission line) for the purpose of identifying the method that can be commonly used. The parametric analysis in detail has been given to explain the efiects of the key parameter variations. For WLAN and WiMAX applications, the antennas are fabricated and measured. Both simulated and measured results are presented to demonstrate the feasibility of these designs.

Ultra-Wideband Impedance Matching Technique for Resistively Loaded Vee Dipole Antenna

The resistively loaded vee dipole (RVD) antenna has many advantages as an ultra-wideband (UWB) radar antenna, especially ground-penetrating radar. However, it has the drawback of having considerable reflections at the feed point due to an impedance mismatch between the antenna and the feeding transmission line. In this communication, a matching network is proposed to reduce the reflection and the design procedure is presented. The network is composed of two L-sections in cascade: an inductive L-section for high frequency matching and a high-pass type L-section for low frequency matching. It is demonstrated that the high-pass type L-section hardly destroys the high frequency matching. The RVD with the proposed matching network is implemented and the performance is measured. The results show that the RVD is matched over the desired band of 500 MHz-3 GHz, and more energy is radiated in the main pulse.

A New Compact Dual-Band Bow-tie Microstrip Antenna for WLAN Applications

In this paper, we propose a novel microstrip antenna for 2.4 GHz (2.4-2.484 GHz) and the 5.8GHz (5.725–5.825 GHz) bands complying with IEEE 802.11b and IEEE 802.11a WLAN standards, respectively. The proposed Antenna occupies an area of 27 mm × 27 mm, when printed on FR4 substrate (εr = 4.4, h = 0.8 mm). The antenna comprises of a bow-tie section, an L-shaped slot on the ground plane, and a 50Ωmicrostrip transmission feed line. Prototype of the proposed antenna has been fabricated and tested. The compact size, low cost, ease of fabrication, and good radiation parameters in comparison with previously published designs are the most advantages of the proposed antenna.

Investigation of a compact coaxially fed switched oscillator

To generate a relative high frequency mesoband microwave, a compact coaxially fed transmission line switched oscillator with high voltage capability is investigated. The characteristic impedance and voltage capability of the low impedance transmission line (LITL) have been analyzed. It is shown that the working voltage of the oscillator can reach up to 200 kV when it is filled by pressurized nitrogen and charged by a nanosecond driving source. By utilizing a commercial electromagnetic simulation code, the transient performance of the switched oscillator with a lumped resistance load is simulated. It is illustrated that the center frequency of the output signal reaches up to ~0.6 GHz when the spark gap practically closes with a single channel. Besides, the influence of the closing mode and rapidity of the spark gap, the permittivity of the insulator at the output end of the LITL, and the load impedance on the transient performance of the designed oscillator has been analyzed in quantification. Finally, the good transient performance of the switched oscillator has been preliminarily proved by the experiment.

Novel Phased-Array Scanning Employing a Single Feed Without Using Individual Phase Shifters [AMTA Corner

Phased arrays afford many advantages over mechanically steered systems. However, they are also more complex, heavy, and, most of all, costly. The high cost mainly originates from the complex feeding structure. This paper proposes a novel feeding scheme to eliminate phase shifters and achieve scanning using a single control parameter. Beam scanning is achieved via a series-fed array, incorporating feeding transmission lines the wave velocity of which can be mechanically adjusted. Practical designs are shown that achieved scanning up to ±30° from boresight. Finally, a prototype was fabricated and measured, demonstrating the concept.

Design of Parallel-Plate Transmission Line Feeding Differentially Driven Patch Antenna for GPS application

In this paper a newly developed patch antenna, designated as the parallel-plate transmission line feeding differentially driven patch antenna is presented. The parallel-plate transmission line will not introduce inductance to the input impedance of a patch antenna, thus the height of the patch can be largely increased. Measurements show that the 3-dB-gain bandwidth can be obtained to 65% (0.86–1.93 GHz), return loss is -20dB, VSWR is 1.3 and impedance is 51 ohm at resonant frequency of 1.58GHz. The radiation pattern is stable and this antenna is designed for GPS application.