Plasma-based microwave power limitation in a printed transmission line: a self-consistent model compared with experimental data

Plasma-based microwave power limitation in a suspended microstrip transmission line integrating a micro hollow cathode discharge (MHCD) in its center is experimentally and numerically studied. Transient and steady state microwave power measurements exhibit a limitation threshold of 28 dBm and time responses of 25 microseconds. Intensified charge-coupled device (ICCD) imaging shows that microwave breakdown occurs at the top of the MHCD. The plasma then extends towards the microwave source within the suspended microstrip transmission line. Besides, a self-consistent model is proposed to simulate the non-linear interaction between microwave and plasma. It gives numerical results in great agreement with the measurements, and show that the plasma expansion during the transient response is related to a shift between the ionization source term and the electron density maximum. The propagation speed, under the tested conditions, depends mainly on the stepwise ionization from the excited states.

High-Precision Complementary Metamaterial Sensor Using Slotted Microstrip Transmission Line

Metamaterial-based microwave sensor having novel and compact structure of the resonators and the slotted microstrip transmission line is proposed for highly precise measurement of dielectric properties of the materials under test (MUTs). The proposed sensor is designed and simulated on Rogers’ substrate RO4003C by using the ANSYS HFSS software. A single and accumulative notch depth of -44.29 dB in the transmission coefficient ( S 21 ) is achieved at the resonant frequency of 5.15 GHz. The negative constitutive parameters (permittivity and permeability) are extracted from the S -parameters which are the basic property of metamaterials or left handed materials (LHMs). The proposed sensor is fabricated and measured through the PNA-X (N5247A). The sensitivity analysis is performed by placing various standard dielectric materials onto the sensor and measuring the shift in the resonant frequencies of the MUTs. A parabolic equation of the proposed sensor is formulated to approximate the resonant frequency and the relative permittivity of the MUTs. A very strong agreement among the simulated, measured, and calculated results is found which reveals that the proposed sensor is a highly precise sensor for the characterization of dielectric properties of the MUTs. Error analysis is performed to determine the accuracy of the proposed sensor. A very small percentage of error (0.81%) and a very low standard deviation are obtained which indicate high accuracy of the proposed sensor.

DEVELOPMENT OF A RF BIOSENSOR DESIGN TO DETECT CHANGES IN SCATTERING PARAMETERS OF AQUEOUS MATERIALS DURING RADIO FREQUENCY WAVE EXPOSURE

The advancing field of biosensor design continues pushing for smaller, inexpensive, yet accurate sensor designs. A subset of biosensors operating in the radio frequency (RF) range of electromagnetic (EM) waves, called RF biosensors, offer appeal as a non-destructive, non-invasive form of sensing. A novel RF biosensor is proposed which detects changes in scattering parameter measurements of a microliter, aqueous material under test (MUT) held within a well adjacent to a microstrip transmission line. This sensing design measures scattering parameter data and changes in these measurements offer insight into the effects of RF wave exposure on dielectric materials within the well. The following paper describes design considerations and the sensing technique of the proposed RF biosensor. Simulations were run in incremental steps to first, establish the simulation design of a 50-ohm microstrip transmission line using two software packages ADS and Ansys HFSS. Next, experimental measurements were collected by milling the RF biosensor, first using air and then distilled water as the MUT, and finally comparing to simulations to establish validity of the novel sensing device. Next, experimental S-parameter measurements were obtained and compared between the two test cases to determine if a difference could be detected. Both simulated and experimentally obtained measurements suggest the designed RF biosensor can detect changes in the MUT loaded inside its etched well and therefore can be used as a sensing device.

Miniaturization of quadrature stub directional couplers.

The method of designing stub quadrature couplers with reduced dimensions relative to the standard design is considered. This technique is based on replacing quarter-wave sections of a microstrip transmission line (MTL) with low-pass filters (LPF), with equivalent frequency characteristics in the vicinity of the central frequency of the device. In addition, the circuit and design implementations of compact couplers with a controlled operating frequency and different wave impedances of the supply lines of the coupler are considered.