Microstrip band-stop filter based on double negative metamaterial

In this work, we present a novel miniature band stop filter based on double negative metamaterial, this circuit is designed on a low-cost substrate FR-4 of relative permittivity 4.4 and low tangential losses 0.002. The proposed filter has a compact and miniature size of 15 mm in length and 12mm in width without the 50 Ω feed lines. The resonator was studied and analyzed with a view to achieving a band-stop behavior around its resonant frequency. The band-stop characteristics are obtained by implementing the metamaterial resonator on the final structure. The obtained results show that this microstrip filter achieves fractional bandwidth of 40% at 2 GHz. Furthermore, excellent transmission quality and good attenuation are achieved. This filter is an adequate solution for global system for mobile communications (GSM).

Miniaturized Dual-Band Bandpass Filter Using T-Shaped Line Based on Stepped Impedance Resonator with Meander Line and Folded Structure

A stepped impedance resonator (SIR) is suitable for designing a dual-band bandpass filter (BPF) that can be adjusted to reject spurious bands. A BPF is proposed using an SIR T-shaped meander line and folded structure. The BPF mainly comprises a meander line, a folded structure, and a T-shaped line. A novel BPF is used for the T-shaped line, which operates as a band-stop filter connecting to the center of the BPF. As a result, the complete BPF enables dual-band operation. The insertion and return losses of the first frequency passband (f01) are 0.024 and 17.3 dB, respectively, with a bandwidth of 46% at a center frequency of 2.801 GHz (2.2–3.48 GHz). The insertion and return losses of the second frequency passband (f02) are 0.026 and 17.2 dB, respectively, with a bandwidth of 10% at a center frequency of 4.351 GHz (4.13–4.55 GHz). The proposed BPF provides low loss, a simple structure, and a small size of only 4.29 × 4.08 mm, and it can be integrated into mobile communications systems.

Development of a Microwave Sensor for Solid and Liquid Substances Based on Closed Loop Resonator

In this work, a compact dielectric sensor for the detection of adulteration in solid and liquid samples using planar resonators is presented. Six types of filter prototypes operating at 2.4 GHz are presented, optimized, numerically assessed, fabricated and experimentally validated. The obtained experimental results provided an error less than 6% with respect to the simulated results. Moreover, a size reduction of about 69% was achieved for the band stop filter and a 75% reduction for band pass filter compared to standard sensors realized using open/short circuited stub microstrip lines. From the designed filters, the miniaturised filter with Q of 95 at 2.4 GHz and size of 35 mm × 35 mm is formulated as a sensor and is validated theoretically and experimentally. The designed sensor shows better sensitivity, and it depends upon the dielectric property of the sample to be tested. Simulation and experimental validation of the designed sensor is carried out by loading different samples onto the sensor. The adulteration detection of various food samples using the designed sensor is experimentally validated and shows excellent sensing on adding adulterants to the original sample. The sensitivity of the sensor is analyzed by studying the variations in resonant frequency, scattering parameters, phase and Q factor with variation in the dielectric property of the sample loaded onto the sensor.

A Novel Band-Stop Filter with Band-Pass, High-Pass, and Low-Pass Negative Group Delay Characteristics

A band-stop filter with three different negative group delay functions in the passband, namely, band pass, high pass and low pass, is proposed, which has small insertion loss. The capacitance, inductance, and resistance meet different conditions, and the circuit can realize three different negative group delay characteristics. The theoretical calculation and equation derivation are given. A band-stop filter with negative group delay function is fabricated, and the measured results are basically consistent with the simulation results. The correctness of the design is verified.