Compact rat-race ring coupler with modified T type capacitor loading

A compact slow-wave microstrip rat-race ring coupler is presented. The new structure effectively reduces the occupied area to 8% of the conventional rat-race ring coupler due to the slow-wave effect. The design is validated both by using the full-wave electromagnetic simulator and by measurement.

In this paper, a compact hybrid ring coupler is designed, simulated, and fabricated to achieve both size reduction and unwanted harmonic suppression in the L-band frequency range. As the demand for miniaturized and high-performance microwave components increases, reducing the footprint of passive devices such as couplers has become a key objective in modern electronic design. The proposed coupler integrates a specially designed resonator between its ports to effectively suppress unwanted harmonics, ensuring improved signal integrity and enhanced operational efficiency. Through this approach, 2nd to 10th harmonics are successfully eliminated, minimizing interference and improving overall system performance. The proposed design operates at a center frequency of 1.4 GHz, achieving an exceptionally low insertion loss of 0.3 dB. Additionally, it demonstrates a remarkable 70% reduction in size compared to conventional couplers while maintaining excellent isolation and phase balance. The design and simulation of the rat-race coupler were conducted using Advanced Design System (ADS) software, and the device was fabricated using a Rogers RT/duroid 5880 substrate with a thickness of 20 mil and a dielectric constant of 2.2. Experimental validation confirms strong agreement between simulated and measured results, highlighting the effectiveness of the proposed structure in achieving compactness and superior performance. This novel design presents a promising solution for modern microwave applications requiring highly efficient, compact, and low-loss couplers.

A microstrip differential-mode (balanced) bandpass filter covering the frequency spectrum assigned for ultra-wideband (UWB) communications (3.1 GHz-10.6 GHz) is presented. The main relevant characteristics of the proposed filter are: (i) the good stop band performance above the band of interest, with high selectivity, harmonic suppression and broad rejection bandwidth, achieved thanks to the embedded capacitive electromagnetic bandgap (EBG) structure; and (ii) the intrinsic (and efficient) common-mode noise rejection (covering the differential filter pass band), related to the controllable transmission zeros provided by the reactively loaded transmission lines present between the pair of differential lines. Additional advantages are low cost, easy fabrication (vias are not required and layout dimensions are not critical), backside isolation (defect ground structures are not present), and compact size (due to the slow-wave effect of the EBG). The combination of performance and size makes the approach very competitive.

We propose a novel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i>-fold spoof surface plasmon polaritons (SSPPs) unit with independently tunable high-order rejection bands. The dispersion characteristics of the proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i>-fold SSPPs are analyzed. The results show that the cutoff frequencies of Modes 2 and 3 can be precisely adjusted through structural parameters, enabling independent control of the stopband position formed by these two modes, without affecting the fundamental mode (Mode 0) or Mode 1. Therefore, the passband number, bandwidth, and stopband width can be flexibly manipulated for the design of multiple passband filters. For verification, a tri-passband, quad-passband filter, and wide stopband filter are designed, fabricated, and measured. The wide stopband filter achieves a 547% increase in the stopband width compared to the tri-passband filter. Good agreement between the simulations and measurements confirms the feasibility of the proposed structure and design method.

This paper proposes a compact UHF microstrip divider with wideband harmonic suppression. A combined resonator, formed by a T-shaped resonator and a pair of coupled compact microstrip resonant cells (CCMRCs), is embedded into each divider branch to replace the conventional quarter-wavelength transmission lines. The divider is designed on an FR4 substrate (εr = 4.4, thickness = 60 mil) for a center frequency of 570 MHz. Full-wave electromagnetic simulations indicate equal power division at 570 MHz with return loss better than 39 dB and output-port isolation higher than 47 dB. Moreover, a wide stopband from 1.5 GHz to 3.5 GHz is obtained, yielding strong attenuation for the third-to-sixth harmonics. The proposed layout occupies 19.6 mm × 21.6 mm, which is about 76% smaller than a conventional 570 MHz divider (42.7 mm × 41 mm). The proposed design is suitable for modern wireless communication systems.

This article presents a new compact, low‐insertion loss, wide stopband, and narrow‐band microstrip bandpass filter using a step‐impedance resonators. A compact filter operated at 2.13 GHz is designed. Experimental results show that the insertion loss of the filter is 1.08 dB and the upper stopband is extended over 8.5 GHz. The effect of varying the width and shape of the couple line to the performance of the filter has been studied. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2071–2074, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22647

This paper presents a compact substrate integrated waveguide cavity-based bandpass filter with a wide stopband. The resonators are heavily capacitively-loaded to miniaturize the structures at the fundamental resonant mode. However, the heavy loading affects the resonant frequency of higher-order modes. This degrades the upper stopband rejection and narrows the spurious-free range. To mitigate the effect of closer spurious passbands, the structure of the filter is modified to incorporate stepped-impedance resonators (SIR). Compared to uniform-impedance resonators (UIR), the fields distribution in the SIRs are altered accordingly, which extends the spurious-free range of the response. To prove the concept, a compact second-order bandpass filter prototype, with capacitive loading and using stepped-impedance cavity resonators, is fabricated and measured. Measurements are shown to be in good agreement with simulations, demonstrating the validity of the proposed technique.

Compact bowtie-shaped microstrip patch antennas with low cross-polarization and wideband harmonic suppression

A novel compact low-temperature-cofired ceramic (LTCC) bandpass filter with sharp rejection and wide stopband is presented in this paper. Semi-lumped resonant cells composed of multilayer ceramic capacitors and via-hole inductors are utilized with source–load coupling, thus two transmission zeros (TZs) can be generated near both sides of the passband, resulting in a high skirt selectivity and wide harmonic suppression. A LTCC bandpass filter works from 2.1 to 2.3 GHz has been designed and fabricated in a four-layer substrate to verify the proposed topology. With an extremely compact size of 2.0 mm × 1.25 mm × 0.9 mm, the design is highly integrated and suitable for miniaturized modern wireless communication applications.

Compact microstrip lowpass filter with high harmonics suppression using defected structures

A novel bandpass filter with excellent harmonic suppression performance based on dual-plane defected ground structure (DGS) is proposed. The DGS slot structure consists of two folded square loop slots and two J-shaped slots. Using this structure, the filter has a good selectivity and exhibits a wide upper stopband characteristic. The equivalent circuit is also presented in this letter. Measured results show that the filter centred at 1.575 GHz has a fractional bandwidth of about 9.2%. The attenuation is below 20 dB over a wide band from 2.2 to 20 GHz.

A planar lowpass filter designed using two resonators of different shape and four high-low impedance transmission lines being used as suppressing cells is realized with wide stopband and compact size. The proposed filter is found to remove up to seventh harmonics. The influence of each resonator on the design is studied separately. The cutoff frequency of the proposed filter is 2.57 GHz and its physical size is 14.6 mm x 9.6 mm. The selectivity is 92.5 dB/GHz. The measured stopband at 18 dB attenuation level is observed from 2.78 GHz to 20 GHz. Simulated results are validated with the measurement results and a good matching is observed between them.

In this work, CMOS compatible hybrid insulator metal insulator (HIMI) planar plasmonic waveguide based components such as, racetrack ring resonator, y-splitter, coupler and dual parabolic profile nano antenna have been proposed and investigated at 1.55 μm operating wavelength for the first time. The proposed components are analyzed at various parametric variations using CST microwave studio. The proposed racetrack ring resonator offers 153.88 nm free spectral range, 0.3232 nm FWHM and 46.57 dB extinction ratio at 0.40 μm radius and 0.49 μm separation length. Y-splitter divides equal power of 46.85% in both output arms and coupler couples till 86.5% power in coupled arm. The dual parabolic profile nano antenna offers a gain, bandwidth and efficiency of 7.99 dB, 203 THz and 84.56 % respectively. Using all the components, HIMI plasmonic integrated circuits have also been designed and investigated for on chip applications. Proposed components work very efficiently in chip scale integrated circuit. This investigation provides groundwork for future chip scale applications.

The design and simplifled analysis of a compact and wide band (16%) negative permittivity complementary split ring resonator metamaterial is introduced. The proposed metamaterial component was applied to reduce the size of the feeding line fllter of microstrip patch antenna for the sake of higher order harmonic suppression. The reduction has been done using only one element of complementary split ring resonator, while maintaining the antenna's performance. Simplifled theoretical study and design of the proposed circuits has been presented. Moreover, experimental results have been done for validation and conformation purpose. Results conflrm that almost 95% of the antenna noise harmonics power has been removed.

This paper presents a novel microwave oscillator incorporating a simple microstrip ring-type resonant cell as its terminating resonance component. Reduced chip size, higher DC-AC power efficiency, and superior harmonic characteristics can be achieved from the introduction of this type of compact microstrip ring resonator cell. The oscillator provides a second harmonic suppression of 26.51 dB and an output power of 2.046 dBm, with 28% efficiency at an oscillation frequency of 2.11 GHz. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 413–415, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21366