Mohammad Hossein Zarifi

Microbead-assisted high resolution microwave planar ring resonator for organic-vapor sensing

A microbead-assisted planar microwave resonator for organic vapor sensing applications is presented. The core of this sensor is a planar microstrip split-ring resonator, integrated with an active feedback loop to enhance the initial quality factor from 200 to ∼1 M at an operational resonance frequency of 1.42 GHz. Two different types of microbeads, beaded activated carbon (BAC) and polymer based (V503) beads, are investigated in non-contact mode for use as gas adsorbents in the gas sensing device. 2-Butoxyethanol (BE) is used in various concentrations as the target gas, and the transmitted power (S21) of the two port resonator is measured. The two main microwave parameters of resonance frequency and quality factor are extracted from S21 since these parameters are less susceptible to environmental and instrumental noise than the amplitude. Measured results demonstrate a minimum resonance frequency shift of 10 kHz for a 35 ppm concentration of BE exposure to carbon beads and 160 kHz for the polymer based ad...

Detection of Volatile Organic Compounds Using Microwave Sensors

A microwave (MW)-based sensing platform for detection of acetone vapor is demonstrated. The sensing platform comprises of an MW resonator coated with a thin layer of polydimethylsiloxane (PDMS) that acts as a sorbent layer for acetone. Absorption-induced swelling of PDMS changes the permittivity and results in reproducible variations in the resonance frequency of the resonator. Here, we demonstrate the detection of acetone, as the model analyte, with the concentrations of 0-265 ppt. In addition, since the technique is based on electromagnetic fields spilling into space, we show the ability of the sensor to detect acetone in a noncontact fashion.

A novel technique for rapid vapor detection using swelling polymer covered microstrip ring resonator

A state of the art technique is presented to enable the use of a planar RF resonator in Volatile Organic Compound (VOC) vapors detection as a simple and low cost sensor platform. In the proposed solution, swelling polymer (polydimethylsiloxane; PDMS) film is deposited on top of a Microstrip ring resonator. At the exposure of the PDMS layer to various concentrations of VOCs such as ethanol and acetone, the PDMS layer adsorbs the vapors. This results in a change in the PDMS thickness and permittivity, which is then detected by a shift in the resonance frequency of the resonator. It is believed that the combination of swelling polymers and the Microstrip resonators can pave the way towards application of planar RF resonators for gas phase detection.

Liquid Sensing Using Active Feedback Assisted Planar Microwave Resonator

A novel electromagnetic sensor operating at microwave frequencies with quality factor of 22,000 at 1.4 GHz for real-time sensing of fluid properties is presented. The core of the sensor has a planar microstrip resonator, which is enhanced using an active feedback loop. The resonance frequency and quality factor of the sensor show clear differentiation between analytes composed of common solvents. To evaluate the sensor for water based concentration detection, we have demonstrated that KOH dilutions as low as 0.1 mM are detectable. The proposed sensor has advantages of inexpensiveness and high resolution as well as capability for miniaturization and CMOS compatibility.

A low-power small-area 10-bit analog-to-digital converter for neural recording applications

In vivo neural recording systems require low power and small area, which are the most important parameters in such systems. This paper reports a new architecture for reducing the power dissipation and area, in analog-to-digital converters (ADCs). A time-based approach is used for the subtraction and amplification in conjunction with a current-mode algorithm and cyclical stage, which the conversion reuses a single stage for three times, to perform analog-to-digital conversion. Based on introduced structure, a 10-bit 100-kSample/s time-based cyclical ADC has been designed and simulated in a standard 90-nm Complementary Metal Oxide Semiconductor (CMOS) process. Design of the system-level architecture and the circuits was driven by stringent power constraints for small implantable devices. Simulation results show that the ADC achieves a peak signal-to-noise and distortion ratio (SNDR) of 59.6 dB, an effective number of bits (ENOB) of 9.6, a total harmonic distortion (THD) of −64dB, and a peak integral nonlinearity (INL) of 0.55, related to the least significant bit (LSB). The ADC active area occupies 280µm × 250µm. The total power dissipation is 5µW per conversion stage and 20µW from an 1.2-V supply for full-scale conversion. Copyright

Non-contact liquid sensing using high resolution microwave microstrip resonator

Here, non-contact liquid sensing using high-resolution microwave sensor is reported. The proposed sensor is based on a passive ring resonator with an active feedback loop to generate negative resistance and compensate for the resonators loss, which in return significantly increases the quality factor of the system. High quality factor offers high-resolution readout with large field penetration depth and thus enables distant, non-contact sensing of liquid materials in a career tube. The active loop technique increases the quality factor of the resonator from 240 to 200000 in air. It also provides flexibility of adjusting the quality factor by varying DC voltage. To our knowledge, this is the first time that a non-contact liquid measurement technique using such high quality factor is reported.

A low-power, low-noise neural-signal amplifier circuit in 90-nm CMOS

A fully-differential low-power low-noise preamplifier for biopotential and neural-recording applications is presented. This design, which has been simulated in a standard 90-nm CMOS process, consumes 30 μW from a 3-V power supply. The simulated integrated input-referred noise is 2.3 μV over 0.1 Hz to 20 kHz. The amplifier also provides an output swing of ± 0.9 V with a THD of less than 0.1%

Wide dynamic range microwave planar coupled ring resonator for sensing applications

A highly sensitive, microwave-coupled ring resonator with a wide dynamic range is studied for use in sensing applications. The resonators structure has two resonant rings and, consequently, two resonant frequencies, operating at 2.3 and 2.45 GHz. Inductive and capacitive coupling mechanisms are explored and compared to study their sensing performance. Primary finite element analysis and measurement results are used to compare the capacitive and inductive coupled ring resonators, demonstrating sensitivity improvements of up to 75% and dynamic range enhancement up to 100% in the capacitive coupled structure. In this work, we are proposing capacitive coupled planar ring resonators as a wide dynamic range sensing platform for liquid sensing applications. This sensing device is well suited for low-cost, real-time low-power, and CMOS compatible sensing technologies.

Design and implementation of MP3 decoder using partial dynamic reconfiguration on Virtex-4 FPGAs

Dynamic reconfiguration has always constituted a challenge for embedded systems designers. Nowadays, technological developments make possible to do it on Xilinx FPGAs, but setting up a dynamically reconfigurable system remains a painful and complicated task. This architecture can benefit from being able to load and unload modules at run-time and using this feature, significant reduction in hardware resources and power dissipation of a chip can be achieved. In this paper, the design and implementation of a MP3 decoder is presented in which IMDCT and antialias blocks are implemented as reconfigurable blocks. In this work, slice based bus macros have been designed and implemented on a XC4VLX25 FPGA using the Xilinx FPGA-Editor software. The reconfiguration time of this design is 19 ms.

Noncontact and Nonintrusive Microwave-Microfluidic Flow Sensor for Energy and Biomedical Engineering

A novel flow sensor is presented to measure the flow rate within microchannels in a real-time, noncontact and nonintrusive manner. The microfluidic device is made of a fluidic microchannel sealed with a thin polymer layer interfacing the fluidics and microwave electronics. Deformation of the thin circular membrane alters the permittivity and conductivity over the sensitive zone of the microwave resonator device and enables high-resolution detection of flow rate in microfluidic channels using non-contact microwave as a standalone system. The flow sensor has the linear response in the range of 0–150 µl/min for the optimal sensor performance. The highest sensitivity is detected to be 0.5 µl/min for the membrane with the diameter of 3 mm and the thickness of 100 µm. The sensor is reproducible with the error of 0.1% for the flow rate of 10 µl/min. Furthermore, the sensor functioned very stable for 20 hrs performance within the cell culture incubator in 37 °C and 5% CO2 environment for detecting the flow rate of the culture medium. This sensor does not need any contact with the liquid and is highly compatible with several applications in energy and biomedical engineering, and particularly for microfluidic-based lab-on-chips, micro-bioreactors and organ-on-chips platforms.