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A single-layered slot antenna system working at 5.8 GHz Industrial, Scientific and Medical (ISM) band is proposed for in-band full duplex (IBFD) operation applications without the use of a coupler. First, high isolation is achieved by strong separation of even- and odd-mode feeds. The microstrip-coupled coplanar waveguide (CPW) is used at Port 1 (TX port) to excite a stepped-slot antenna in the CPW odd mode. On the opposite side, a microstrip T-junction power divider is employed at Port 2 (RX port) to feed two offset-fed stepped-slot antennas in even mode. Second, isolation is further improved by 30 dB by using a lumped capacitor at the termination of the CPW. The measured isolation between the two ports is about 50 dB across the bandwidth. The measured −10 dB bandwidth of Port 1 is 0.49 GHz (8.5%), while that of Port 2 is 1.06 GHz (18.3%). The gains of TX and RX antennas are 5.4 and 5.8 dBi at 5.8 GHz. The proposed antenna can also be deployed as a dual-polarized antenna. Mathematical analysis and equivalent transmission line circuit models are provided to give physical insight into the working principals of the antenna with validation from ANSYS HFSS simulation. [ABSTRACT FROM AUTHOR]

This paper presents a microwave sensor for simultaneous measurement of permittivity and thickness in dielectric materials. The sensor is made of a dual-mode magnetic- $LC$ resonator coupled to a microstrip transmission line. Due to a dual-mode resonance of the magnetic- $LC$ resonator, the transmission response of the sensor shows two zero frequencies. By applying dielectric materials of various permittivities and thicknesses to the resonator, both of the transmission zero frequencies are modified. The alterations of the two transmission zero frequencies are used to characterize the permittivity and thickness of the dielectric samples under test. A prototype of the sensor is fabricated and measured for verifying the proposed sensing principle. [ABSTRACT FROM AUTHOR]

The conventional resonant-type microwave microfluidic sensors made of planar resonators suffer from limited sensitivities. This is due to the existence of several distributed capacitors in their structure, where just one of them acts as a sensing element. This article proposes a very high-sensitivity microwave sensor made of a microstrip transmission line loaded with a shunt-connected series LC resonator. A large sensitivity for dielectric loadings is achieved by incorporating just one capacitor in the resonator structure. Applying sample liquids to the microfluidic channel implemented in the capacitive gap area of the sensor modifies the capacitor value. This is translated to a resonance frequency shift from which the liquid sample is characterized. The sensor performance and working principle are described through a circuit model analysis. Finally, a device prototype is fabricated, and experimental measurements using water/ethanol solutions are presented for verification of the sensing principle. [ABSTRACT FROM AUTHOR]

This letter presents a differential microwave permittivity sensor based on the reflection coefficient of microstrip lines terminated with series $LC$ resonators. A $50~\Omega $ resistor is considered in series with the resonator. At resonance, the transmission line experiences a matched load causing a reflection zero. Two identical sensing elements are used for differential sensing, providing the possibility of simultaneous two samples detection. A prototype of the sensor is fabricated and measured around 2 GHz for validation of the differential sensing principle. [ABSTRACT FROM AUTHOR]

A varactor-based tunable bandstop filter has been proposed in this letter. The proposed filter is based on a dual-mode circuit developed by introducing inductive and capacitive couplings into a notch filter. The frequency tunability is achieved by using varactor diodes instead of the lumped capacitors in the circuit. Next, the equivalent circuit model has been implemented in planar microstrip technology using thin inductive traces and varactor diodes. The fabricated filter prototype shows a continuous center frequency tuning range of 0.66–0.99 GHz with a compact size of 0.12\lambda g \times 0.16\lambda g , where \lambda g is the guided wavelength at the middle frequency of the tuning range. [ABSTRACT FROM PUBLISHER]

A new metamaterial-inspired microwave microfluidic sensor is proposed in this paper. The main part of the device is a microstrip coupled complementary split-ring resonator (CSRR). At resonance, a strong electric field will be established along the sides of CSRR producing a very sensitive area to a change in the nearby dielectric material. A micro-channel is positioned over this area for microfluidic sensing. The liquid sample flowing inside the channel modifies the resonance frequency and peak attenuation of the CSRR resonance. The dielectric properties of the liquid sample can be estimated by establishing an empirical relation between the resonance characteristics and the sample complex permittivity. The designed microfluidic sensor requires a very small amount of sample for testing since the cross-sectional area of the sensing channel is over five orders of magnitude smaller than the square of the wavelength. The proposed microfluidic sensing concept is compatible with lab-on-a-chip platforms owing to its compactness. [ABSTRACT FROM PUBLISHER]

This letter proposes a microstrip filter based on a dual-mode complementary split-ring resonator (DMCSRR). For the input/output coupling, a dual C-shaped feed structure is implemented together with the DMCSRR to acheive a wideband response. The resonator offers a wide fractional bandwidth of 62% at the central frequency of 2.23 GHz and a very compact structure with a footprint of 0.0625\lambdag\times 0.18\lambdag, where \lambdag is the guided wavelength at the midband frequency. A comprehensive lumped element circuit analysis accompanies the simulation and measurement results. [ABSTRACT FROM PUBLISHER]