Composite Right/left-handed Resonator Research Articles

Compact dual-band balanced bandpass filter using CRLH resonator with intrinsic common-mode suppression and multiple transmission zeros

In this paper, a newly composite right-/left-handed (CRLH) resonator is presented and applied to constitute a compact dual-band balanced bandpass filter (BPF). The proposed CRLH resonator contains two spiral coupled line segments. By imposing the differential-mode (DM) and common-mode (CM) excitation, the DM and CM equivalent circuits of the presented resonator and their lumped-element circuit models are built for investigating the resonant property. The CRLH resonator has two DM resonances and are adopted to design two DM passbands. Also, the CM resonances are all far away from DM resonances, achieved intrinsic desirable CM rejection within DM frequency range without any auxiliary elements. Attributing to the mixed electric and magnetic coupling between two coupled resonators and the introduced source-loaded coupling, multiple transmission zeros are obtained and therefore enhance the selectivity and attenuation in stopband. Finally, a well-designed dual-band balanced BPF is fabricated. Verification of the presented structure and design method’s validity is evidenced by the measured results, which are in agreement with the simulations.

A Compact 3.3–3.5 GHz Filter Based on Modified Composite Right-/Left-Handed Resonator Units

In the RF (Radio Frequency) front-end of a communication system, bandpass filters (BPFs) are used to send passband signals and reject stopband signals. Substrate-integrated waveguides (SIW) are widely used in RF filter designs due to their low loss and low cost and the flexibility of their integration properties. However, SIW filters under 6 GHz are still too large to meet the requirement of portable communication devices due to their long wavelength. In this paper, a very compact fully integrated SIW filter is proposed and designed with RT6010 dielectric material to meet the small size requirement of portable devices for next-generation sub-6 G applications. The proposed filter contains two sawtooth-shaped composite right-/left-handed (CRLH) resonator units, instead of traditional rectangular-shaped CRLH resonator units, which makes the filter more compact and cost effective. The filter is designed and fabricated on an RT6010 substrate, with a size of only 10 mm × 7.4 mm. The measurement results illustrated that the proposed BPF shows a passband covering the frequency range of 3.25–3.45 GHz; the minimum passband insertion loss is only 2.4 dB; the stopband rejection is better than −20 dB throughout the frequencies below 3.0 GHz and above 3.8 GHz; S11 is as low as −37 dB at 3.35 GHz; and the group delay variation is only 1.4 ns throughout the operation bandwidth.

Design of Compact Balanced-to-Balanced Diplexer Using Dual-Mode CRLH Resonator for RFID and 5G Applications

A compact balanced-to-balanced diplexer based on composite right/left-handed (CRLH) resonator is presented in this paper. The proposed compact CRLH resonator is used to design two balanced channels, which are connected by T-junction to construct the balanced-to-balanced diplexer. Under differential-mode (DM) operation, the proposed CRLH resonator can provide two adjacent DM resonant modes to produce one passband of the balanced-to-balanced diplexer. Under common-mode (CM) operation, the CRLH resonator also generate two CM resonant modes, whose locations are far away from DM resonant modes, resulting in a perfect CM suppression level. To verify the design methodology, a compact balanced-to-balanced diplexer operated at 2.45 GHz and 3.47 GHz is designed and fabricated for multi-service system integrated with microwave RFID and 5G applications. The proposed balanced-to-balanced diplexer shows high CM suppression level and channel-to-channel isolation performance. The measured results are agree well with the simulated ones.

Dual-Band and Polarization-Flexible CRLH Substrate-Integrated Waveguide Resonant Antenna

A dual-band and polarization-flexible substrate-integrated waveguide (SIW) resonant antenna based on composite right-/left-handed (CRLH) structure is presented in this letter. The proposed antenna consists of a CRLH SIW resonator and dual feeding lines. A slot and surface-mount technology capacitors on the top metallic layer of SIW resonator provide necessary reactance to realize multiresonance CRLH structure. Due to the intrinsic multiband characteristic of a CRLH structure, the proposed antenna can provide dual-band broadside radiations. Polarization flexibility is realized by two orthogonal feedlines. Utilizing the CRLH resonator instead of the conventional square resonator, such as patch antenna, allows antenna miniaturization. The electrical lengths of the sidewalls for the proposed square SIW resonant antenna are 75% (for first resonant mode) and 44% (for second resonant mode) shorter than that of the previously proposed dual-band polarization-flexible SIW antenna. To highlight the unique advantages, the dual-band circularly polarized antenna array based on the proposed antenna element is presented. Dual-band circularly polarized radiation is supported by the dual-band CRLH transmission-line-based feeding network.

Miniaturized Active Metamaterial Resonant Antenna With Improved Radiation Performance Based on Negative-Resistance-Enhanced CRLH Transmission Lines

In this letter, a miniaturized microstrip resonant antenna (MRA) based on the active metamaterial resonator is presented. Unlike the passive composite right/left-handed (CRLH) resonators, the presented active metamaterial resonators are realized using the negative-resistance-enhanced CRLH transmission line that incorporates active circuits for loss compensation. The active circuit uses bipolar junction transfer in its inverted-common-collector configuration to provide a negative resistance for the proposed active MRA. The presented passive and active antennas both operate in the negative-first-order resonance mode and thus have reduced dimensions compared to the conventional planar MRAs. The integration of the active elements delivers higher radiation gain compared to the passive negative-order CRLH resonator antenna. The passive and active antennas were fabricated, and the measured results are presented to validate the concept.

Compact filtering antenna using CRLH resonator and defected ground structure

A compact filtering antenna with high band-edge gain selectivity using a composite right-/left-handed (CRLH) resonator and a defected ground structure is presented. The CRLH resonator resonates at the zeroth-order mode and acts as the first stage of the corresponding filter; an octagonal patch acts as a radiator as well as the last stage of the filter. The design procedure follows the circuit approach - synthesis of bandpass filters. The filtering antenna has two poles in the passband and two radiation nulls (zeros) at the band edges. Compared to the conventional patch antenna, the proposed filtering antenna, with little extra circuit area, has flat gain response within the passband, good selectivity at the passband edge and wider bandwidth. Measurement results show that the filtering antenna can operate at 5.29 GHz, has a 430 MHz bandwidth and a 2.5 dBi antenna gain in the broadside (+ Z ) direction within the passband.

Zero-Index Terahertz Quantum-Cascade Metamaterial Lasers

We propose a new one-dimensional composite right/left-handed (CRLH) transmission line active metamaterial based upon a sub-wavelength metal waveguide loaded with quantum-cascade material that provides terahertz gain via stimulated emission. Finite element simulations were performed to design and characterize a one-dimensional CRLH metamaterial supporting ¿backward¿ waves in the range of 1-2 THz. The addition of capacitive gaps in the top metal and inductive virtual current paths from top contact to the ground plane of a metal-metal quantum-cascade waveguide introduces propagating negative index and zero-index modes. We evaluate the feasibility of a zero-index terahertz quantum-cascade laser, based on a CRLH resonator, which exhibits a uniform spatial mode that is immune to spatial hole burning. An alternate balanced design for traveling-wave applications is also discussed.