Discussion and Analysis of Dumbbell Defect-Ground-Structure (DB-DGS) Resonators for Sensing Applications from a Circuit Theory Perspective

Microstrip transmission lines loaded with dumbbell defect-ground-structure (DB-DGS) resonators transversally oriented have been exhaustively used in microwave circuits and sensors. Typically, these structures have been modelled by means of a parallel LC resonant tank series connected to the host line. However, the inductance and capacitance of such model do not have a physical meaning, since this model is inferred by transformation of a more realistic model, where the DB-DGS resonator, described by means of a resonant tank with inductance and capacitance related to the geometry of the DB-DGS, is magnetically coupled to the host line. From parameter extraction, the circuit parameters of both models are obtained by considering the DB-DGS covered with semi-infinite materials with different dielectric constant. The extracted parameters are coherent and reveal that the general assumption of considering the simple LC resonant tank series-connected to the line to describe the DB-DGS-loaded line is reasonable with some caution. The implications on the sensitivity, when the structure is devoted to operating as a permittivity sensor, are discussed.

Parametric Analysis of the Edge Capacitance of Uniform Slots and Application to Frequency-Variation Permittivity Sensors

This paper presents a parametric analysis relative to the effects of the dielectric constant of the substrate, substrate thickness and slot width on the edge capacitance of a slot-based resonator. The interest is to find the conditions (ranges of the previously cited parameters) compatible with the presence of a quasi-magnetic wall in the plane of the slot (or plane of the metallization). If such magnetic wall is present (or roughly present), the electric field in the plane of the slot is tangential (or quasi-tangential) to it and the edge capacitance can be considered to be the parallel combination of the capacitances at both sides of the slot. Moreover, variations in one of such capacitances, e.g., caused by a change in the material on top of the slot, or by a modification of the dielectric constant of the substrate do not affect the opposite capacitance. Under the magnetic wall approximation, the capacitance of certain electrically small slot-based resonators can be easily linked to the dielectric constant of the material present on top of it. The consequence is that such resonators can be used as sensing elements in a permittivity sensor and the dielectric constant of the so-called material under test (MUT) can be determined from the measured resonance frequency and a simple analytical expression. In this paper, the results of this parametric analysis are validated by considering several sensing structures based on dumbbell defect ground structure (DB-DGS) resonators of different dimensions.

Rancang Bangun Antena Semi Circular Dengan Teknik GDS (Defect Ground Structure) untuk Meningkatkan Bandwidth Antena Pada Aplikasi WIFI

Kebutuhan yang semakin meningkat akan banyaknya data yang dikirim dan kecepatan pengiriman data melalui teknologi wireless mengakibatkan tingginya minat terhadap perangkat dengan Bandwidth lebar. Memperbaiki desain antena adalah salah satu cara untuk meningkatkan Bandwidth. Antena didesain sedemikian rupa agar mendapatkan parameter antena yang bernilai efektif salah satunya untuk meningkatkan bandwidth antena. Salah satu teknik yang digunakan untuk memperbaiki parameter antena miksrostrip yaitu teknik Defect Ground Structure (DGS) dengan metode yang digunakan adalah perhitungan, simulasi dan pengujian. Hasil pengujian antena mikrostrip array semicircular tanpa DGS diperoleh nilai parameter return loss sebesar -13,7 dB dan nilai VSWR sebesar 1,518 serta memiliki gain bernilai 1,3 dBi pada frekuensi 2455 MHz. Antena ini memiliki bentuk pola radiasi bidirectional. Bandwidth antena yang diperoleh sebesar 14 MHz. Hasil pengujian antena mikrostrip array semicircular dengan DGS diperoleh nilai parameter return loss sebesar -14,4 dB dan nilai VSWR sebesar 1,469 serta memiliki gain bernilai 2,8 dBi pada frekuensi 2455 MHz. Antena ini memiliki bentuk pola radiasi directional. Bandwidth antena yang diperoleh sebesar 10 MHz. Kesimpulan dari penelitian ini adalah antena mikrostrip array semicircular tanpa DGS mempunyai bandwidth yang lebih kecil dibandingkan dengan antena mikrostrip array semicircular dengan DGS yaitu dengan selisih sebesar 3,5 MHz.

Differential Microfluidic Sensors Based on Dumbbell-Shaped Defect Ground Structures in Microstrip Technology: Analysis, Optimization, and Applications

A microstrip defect ground structure (DGS) based on a pair of dumbbell-shaped slots is used for sensing. The device is a differential sensor consisting of a pair of mirrored lines loaded with a dumbbell-shaped DGS, and the output variable is the cross-mode transmission coefficient. Such a variable is very sensitive to asymmetries in the line pair, e.g., caused by an asymmetric dielectric load in the dumbbell-shaped DGSs. Therefore, the sensor is of special interest for the dielectric characterization of solids and liquids, or for the measurement of variables related to complex permittivity changes. It is shown in this work that by adding fluidic channels on top of the dumbbell-shaped DGSs, the device is useful for liquid characterization, particularly for the measurement of solute concentration in very diluted solutions. A sensitivity analysis useful for sensor design is carried out in this paper.

A novel defect ground structure for decoupling closely spaced E-plane microstrip antenna array

In this paper, a novel decoupling technique for closely spaced E-plane patch antennas using defect ground structure (DGS) is proposed. The electric field coupling between the antennas is suppressed by etching DGS which consists of a pair of rectangular slots and four stubs on the ground plane. Moreover, unlike the other methods, the DGS is not etched in the middle of the antennas but loaded along the outer edge of the radiated patch. Thus, through the adopted technology the distance between the antenna elements is reduced and the isolation is increased. To validate the improvements by adopting the proposed technology, the array with DGS loading has been fabricated and then measured. The measurement results show that designed antennas have 95 MHz 10-dB impedance bandwidth, which is 25 MHz higher than that of the antenna without DGS. More importantly, isolation improvements have been increased from 8.5 to 31.3 dB by using the decoupling technique when the antennas are placed with a 0.032 λ0 edge-to-edge distance, where λ0 is the free-space wavelength. Therefore, this technique can be widely applied to improve isolation in a compact and low profile antenna system.