Alonso Corona-Chavez

Microstrip Switchable Bandstop Filter using PIN Diodes with Precise Frequency and Bandwidth Control

In this paper a switchable bandstop filter able to switch between two different central frequency states while precisely maintaining a fixed bandwidth is presented. The filter topology allows precise control over the design parameters frequency and bandwidth, achieved by choosing adequate resonator sections which are switched by PIN diodes to obtain two discreet states. The central frequency control was obtained by modifying resonator length. Bandwidth control was achieved by choosing a resonator width and controlling the normalized reactance slope parameter of a decoupling resonator by means of a switchable resonator extension. The filter was designed to have center frequencies of 2 and 1.5 GHz both having an 8% fractional bandwidth. The comparison between simulations and measurements showed a central frequency deviation of 4 MHz for the 2 GHz frequency response, and a deviation of 2 MHz for the 1.5 GHz frequency response. The fractional bandwidth deviation for the 2 GHz filter response was 0.67%, while at 1.5 GHz a 0.4% deviation was observed. The simulation and measured responses are in very good agreement.

Complex permittivity measurements using cavity perturbation technique with substrate integrated waveguide cavities

Cavity perturbation technique is widely used in the measurements of complex dielectric permittivity of materials due to its accuracy and ease of configuration. This paper presents the theoretical formulas for the evaluation of complex permittivity of materials using cavity perturbation technique with substrate integrated cavity resonators. With the proposed formulas, the use of various planar cavities is possible by taking into account the dielectric characteristics of the substrate in which the cavity is implemented. Simulations and measurements are performed on various dielectric samples to validate the proposed theory. The maximum deviation in the measured dielectric permittivity values is below 6% compared to the literature values. The implemented substrate integrated cavity is then analyzed in terms of sensitivity, showing a good performance.

Permittivity Measurements at Microwave Frequencies Using Epsilon-Near-Zero (ENZ) Tunnel Structure

A planar epsilon-near-zero (ENZ) tunnel structure implemented on substrate integrated waveguide (SIW) technology is used to evaluate the complex dielectric permittivity of various materials. Design, optimization, and fabrication of the ENZ tunnel structure are explained. Simulations and measurements on various dielectric samples using the cavity perturbation technique of the proposed structure are presented. Measured values of the permittivity are in good agreement with standard values. Sensitivity analyses are performed on the ENZ structure and the conventional SIW cavity techniques. The proposed structure has very high sensitivity, which yields more accurate results when compared to other techniques, such as perturbation of conventional cavities.

Micromachined Transmission Lines for Millimeter-Wave Applications

Several different fabrication techniques and materials have been proposed for making low loss high performance micromachined transmission lines. In this paper a review of several micromachined transmission lines that have been proposed over the last years are classified into four types according to their physical structure and their power losses addressed.

Microstrip Balanced Bandpass Filter With Compact Size, Extended-Stopband and Common-Mode Noise Suppression

In this letter, a novel balanced bandpass filter (BPF) with its simple design procedure are proposed. The filter is based on a novel balanced resonator which is composed by two closed-loop transmission lines of characteristic impedance Z_CL = 50 Ω and electrical length of 53.13° and one transmission line of characteristic impedance Z_HI = 100 Ω and electrical length of 53.13°. Also the differential-mode (DM) and common-mode (CM) equivalent circuits of the resonator are given for design purposes. A prototype with measured DM passband at 1.029 GHz and fractional bandwidth (FBW) of 9.833% is presented. The prototype exhibits compact size (0.149 λ_g × 0.228 λ_g), DM stopband with a 40 dB suppression level broadened up to 5.633 f_0d and CM suppression level better than -40 dB from 0 to over 3.7 f_0d and better than -30 dB from 0 to 5.91 f_0d.

Dielectric Properties of Beans at Different Temperatures and Moisture Content in the Microwave Range

Dielectric properties of common Mexican beans (Phaseolus vulgaris L.) were determined and analyzed at microwave frequencies (800–2500 MHz). The free-space transmission technique was employed for the measurements of three varieties (“Flor de mayo,” “Bayo,” and “Negro”) with different moisture content (8.8–12.3%, w.b.) at 20, 30, 40, 50, and 60°C. The dielectric constant and loss factor of beans decreased with increasing frequency for a fixed temperature, and increased with increasing temperature at a fixed frequency. The dielectric constant increased with increasing moisture content, while the loss factor remained nearly constant. With these results, disinfestation or quality control measurements can be proposed for beans using microwaves.

Wireless Sensing of Complex Dielectric Permittivity of Liquids Based on the RFID

A wireless sensing system for the evaluation of the complex dielectric permittivity of solvent liquids is presented. Two sensing tags are proposed for testing of the samples. The first tag is based on a cavity resonator and the second makes use of the epsilon-near-zero effect. Both circuits are designed over the planar substrate-integrated-waveguide (SIW) technology, and operate at 4 GHz. A quartz capillary tube is used for the liquid measurements where only a small amount of sample volume is required. With the addition of planar antennas at the input and output of the sensors, the complete system is implemented for wireless sensing of the materials following the RF identification scheme. The cavity perturbation technique for SIW structures is applied for the dielectric liquid characterization. The proposed sensing tags and system have high potentials for low-cost wireless measurements and real-time monitoring applications.

HTS Quasi-Elliptic Filter Using Capacitive-Loaded Cross-Shape Resonators With Low Sensitivity to Substrate Thickness

The design and implementation of a four-pole quasi-elliptic filter for X-band radar applications using high-temperature superconductors is presented. The resonators used consist of cross-shape ring resonators with additional interdigital capacitive loads that allow miniaturization with reduction of sensitivity to substrate thickness. The experimental and simulated results are shown together with the power dependence of the filter

Dual-Band Multi-Pole Directional Filter for Microwave Multiplexing Applications

A novel microstrip directional filter for multiplexing applications is presented. This device uses composite right-left-handed transmission lines and resonators to achieve dual-band frequency response. In addition, by cascading two or more stages using dual frequency immitance inverters, multi-pole configurations can be obtained. Simulation and experimental results are presented with good agreement.

Circular Aperture Slot Antenna With Common-Mode Rejection Filter Based on Defected Ground Structures for Broad Band

A novel system composed of a circular aperture slot antenna and a Common-Mode (CM) noise rejection filter is presented. This antenna is differentially fed by microstrip coupled transmission lines. In order to eliminate CM noise, a notch filter based on three non-periodical defected ground structures (DGS) was implemented. The whole system achieves a fractional impedance bandwidth of about 127%. Radiation patterns in E and H planes for different frequencies were obtained for the system. Finally, measurements in the transversal plane show attenuation up to 13 dB when the system with filter was compared against one without it. Good agreement between simulated and measured results can be observed.