Bandstop Filter Synthesis Scheme for Reactively Loaded Microstrip Line Based 1-D Periodic Structures

A 1-D finite electromagnetic bandgap (EBG) periodic structure is studied. In the structure, EBG behaviour arises from a unit cell comprised of a metallic patch sandwiched between microstrip line and ground plane. Reactive loading offered by patch size determines the bandgap position. A detailed parametric study of various physical structure parameters is presented as a basis to develop a interrelation between physical parameters of the structure and cutoff frequencies. Closed-form synthesis equations are then formulated using curve fitting techniques. Subsequently, a step-by-step design methodology is presented to get a close first pass approximation of structure dimensions for a given specification. This design method reduces the effort required for a designer to perform extensive electromagnetic simulations at early stages of the design. The proposed synthesis method is tested for a variety of commercially available substrates and different frequency ranges for validation. Comparison with electromagnetic (EM) simulations and measurement show that the proposed synthesis method provides first pass approximation of the physical structure dimensions with 94% accuracy

Composite Right/Left-Handed Leaky-Wave Antennas for Wide-Angle Beam Scanning with Flexibly Chosen Frequency Range

© 2019 IEEE. A composite right/left-handed (CRLH) leaky-wave antenna (LWA) can effectively scan the radiation beam from backward-to-forward direction. However, in most cases, a large range of frequency sweep is required to achieve a wide-angle beam scan, which could limit their applications. An in-depth study is conducted on an equivalent circuit model for a CRLH LWA unit cell to find the controlling parameters on the frequency sweeping range. A systematic design guideline is given for a CRLH LWA for a wide-angle beam scan in a flexibly chosen frequency range. It is shown that beam scanning by sweeping frequency in a target range can be achieved by systematically designing the unit cell parameters. To verify our approach, a novel CRLH unit cell is developed and used to design an LWA for a wide-angle beam scan in a narrow frequency range. Finally, the concept is validated through realization of the antenna and its measurement. The measured results show that the antenna prototype can scan its beam from -56° to +51° when frequency sweeps from 5.1 to 6.11 GHz (i.e., 18.02% of fractional bandwidth)

One Dimensional Leaky-Wave Antennas with Continuous Scan of Radiating Beam

Leaky-wave antennas (LWAs) have the ability to scan beam with frequency. However, the major limitation faced by most of the LWAs, particularly uniform LWAs, is their inability to scan beam through broadside. A method to achieve a continuous beam scan from backward to forward is discussed here. A substrate-integrated waveguide (SIW)-based structure is used for the study. The SIW-based LWA with only horizontal (longitudinal) slots is unable to scan the beam through the broadside due to an open stopband (OSB). The OSB is closed by using additional vertical (transverse) slots and groups of shorting vias. The simulated results show that the LWA can scan beam continuously from -47 to +27when frequency sweeps from 8.75 to 13 GHz

Wide-Angle Wideband Frequency-Independent Beam-Scanning Leaky Wave Antenna

© 2019 IEEE. Frequency-independent beam scanning leaky-wave antennas (LWAs) that can operate over a specific frequency band are highly desirable for future wireless systems. A composite right/left-handed (CRLH) LWA is developed in this paper that facilitates these functionalities. It utilizes two groups of varactor diodes to realize the frequency-independent beam scanning capability. The optimized reconfigurable CRLH LWA and its simple DC biasing network achieves a simulated frequency-independent beam that scans over 100° at each frequency point between 4.75 and 5.25 GHz. An antenna prototype was fabricated and tested. The measured results at 5.0 GHz confirm its simulated performance characteristics

Polarization-Reconfigurable Leaky-Wave Antenna with Continuous Beam Scanning through Broadside

© 2019 IEEE. A simple single-layer reconfigurable leaky-wave antenna (LWA) is presented that has polarization agility and beam-scanning functionality. This LWA system realizes a scanned beam that can be switched between all of its linear polarization (LP) and circular polarization (CP) states using only one dc biasing source. A slot-loaded substrate-integrated waveguide (SIW)-based LWA is first explored to attain CP performance with continuous beam scanning through broadside. This CP LWA realizes a measured CP performance with a 3 dB gain variance within 2.75-3.35 GHz for scan angles ranging from -28.6° to +31.5°. A row of shorted stubs is then incorporated into the CP LWA to obtain similar LP performance. Finally, by introducing p-i-n diodes into this LP LWA configuration to facilitate reconfigurable connections between the main patch and the shorted stubs, the radiated fields can be switched between all of its CP and LP states. The measured results of all three antennas confirm their simulated performance. It is demonstrated that the main beam of the polarization-reconfigurable LWA can be scanned from -31.5° to +17.1° with gain variations between 9.5 and 12.8 dBic in its CP state and from -34.3° to +20° with them between 7.8 and 11.7 dBi in its LP state

A Compact Reconfigurable 1-D Periodic Structure in GaAs MMIC With Stopband Switching, Dual-Band Operation and Tuning Capabilities

This paper presents a systematic study of a compact and reconfigurable periodic structure in GaAs MMIC technology. Compactness is achieved by the introduction of spiral inductors in a conventional unit cell without disturbing the reactive loading mechanism. The proposed architecture exhibits a 28.3% wider stopband with 62.6% smaller footprint compared to a conventional structure. The compactness and bandwidth improvement in the proposed structure is explained with the help of dispersion and circuit analysis. The reconfigurability built into the design using PIN diodes allows stopband switching, dual-band operation and tuning capabilities with the mere use of a single reactive load in its unit cell. To the best of the authors knowledge, it is the first time a reconfigurable MMIC implementation is realized using the proposed structure or even the conventional design. As a guide to design, sensitivity analysis to filter performance is presented for important structure parameters. Switching element parasitics are discussed in two ways: firstly, with the design and measurement of structures with idealized switching conditions and in second, with the circuit and full-wave EM modelling of the finite periodic structure with the actual PIN diodes. The on-chip measurements of the fully reconfigurable filter show excellent agreement with simulations

Simple composite right/left-handed leaky-wave antennas for continuous beam scanning from backward to forward direction

© 2016 IEEE. Microstrip leaky-wave antennas (MLWAs) are presented for continuous beam scanning from backward to forward directions. The antenna is implemented by cascading composite right/left-handed (CRLH) unit cells. Each unit cell consists of two outer shorted patches and an open patch between the shorted patches. Series capacitance is implemented by using gaps between the patches, and shunt inductance is achieved by using metallic vias. Two antennas with different numbers of unit cells are considered for the analysis. An antenna with 8 unit cells covers an impedance bandwidth from 6.12 to 9.075 GHz and the main beam scans continuously from -52° to 47° when the frequency is swept from 6.25 to 9.25 GHz

Fixed-frequency leaky-wave antenna for simultaneous forward and backward scanning

© 2014 IEEE. A half-width microstrip leaky-wave antenna (HW-MLWA) is presented for simultaneous beam scanning in forward and backward directions at a fixed frequency. The directions of two main beams are controlled by changing the admittance between the radiating edge of the microstrip line and the ground plane. This is achieved by using gap capacitors at the radiating edge of the microstrip line and controlling their connection to the ground plane using digital switches. Two main beams of the proposed antenna can be steered from broadside (0°) to 33° in both forward and backward directions simultaneously at 6.25 GHz

A composite right/left-handed leaky-wave antenna with gap capacitors for backward to forward beam scanning

© 2015 IEEE. This paper presents a simple composite right/left-handed (CRLH) leaky-wave antenna (LWA) for continuous beam scanning from backward to forward direction through the boresight. The proposed CRLH LWA has the ability to scan the main beam from-40° to 40° by sweeping the operating frequency from 7.5 GHz to 10 GHz, with a boresight beam at 8.58 GHz. The peak gain of the antenna is 12.45 dBi and its 3dB gain bandwidth is 2 GHz (8-10 GHz)