Ahmet Oncu

An Ultra Low-Power Dual-Band IR-UWB Transmitter in 130-nm CMOS

In this brief, a 0-960-MHz/3.1-5-GHz dual-band ultra low-power impulse-radio ultrawideband transmitter is presented. The pulse transmitter integrated circuit is fabricated using a 130-nm CMOS process with the core die area of 0.1 mm2. At 1-MHz pulse repetition frequency, the power consumption values are measured in the lower and the upper bands as 5.6 and 31 μW, respectively. The lower and the upper band “off-time” power consumptions of the transmitter are 0.36 and 1.7 μW, respectively. The dc-to-radio-frequency conversion efficiencies are 11.1% in the lower band and 4.8% in the upper band.

An Optically Powered CMOS Receiver System for Intravascular Magnetic Resonance Applications

This paper presents a low-power optically powered receiver system designed in 0.18 μm triple well UMC complementary metal-oxide-semiconductor (CMOS) technology. Optical transmission is used for both power delivery and signal transmission. The power of the whole system can be supplied in two different configurations, namely continuous and intermittent mode configurations. In the continuous mode configuration, the optical power of a 650-nm laser source is received and delivered to the electronic circuits by a set of on-chip CMOS photodiodes. In the intermittent mode configuration, a low voltage DC-DC converter is used to boost a single on-chip CMOS photodiode voltage of 0.65 V up to 1.8 V. Additionally, in this configuration, optical switching is used for charging and discharging of a storage capacitor to obtain currents in milliampere range for the proper operation. The front-end part of the receiver consists of a fully differential low noise amplifier (LNA), a fully differential gain stage, a single output double balanced Gilbert-cell mixer, and a laser driver. The front-end part can operate properly by one on-chip photodiode voltage of 0.65 V . System performance is demonstrated for a sample 1.5 T magnetic resonance imaging (MRI) application. Experiments show that LNA of the receiver has a low input referred noise voltage density of 4 nV/√{Hz} at the supply voltage of 0.65 V . The receiver transmits the signal via a fiber-coupled infrared (IR) laser diode (λ = 1310 nm). The results show that the system can continuously process a minimum detectable signal (MDS) of -70 dBm at an incident optical power of 20 mW while the total power consumption of the receiver and the IR diode is 700 μW . In the intermittent mode configuration, the system gain is measured to be 6 dB greater, and the average power consumption is measured as 214 μW when the incident laser is modulated with a rectangular pulse wave of 40 ms period with 95% duty cycle.

Design of a 1.26 GHz high gain microstrip patch antenna using double layer with airgap for satellite reconnaissance

In this paper, we introduce a method using double layer with airgap to design a high gain single element microstrip rectangular patch antenna operating at 1.26 GHz. Double layer technique provide us easy fabrication, besides, under layer consisted of double-sided copper ensure using one side as ground plane and other side as feed network for higher gain array antenna. Low cost fabrication also has been taken into account. To do that, we used a widely available FR4 material and instead of using low-loss and expensive substrates, we inserted an air gap between radiating and ground planes. This air gap reduces both the electric field concentration on the lossy epoxy and the effective dielectric constant of the radiating plane. Therefore, a low-loss and high-gain single element rectangular patch antenna is obtained. The simulation results conducted by CST Microwave Studio and measurement results carried out in an anechoic chamber of the proposed antenna are included in this study. The close similarity between simulation results and measurement results has been observed. This proposed antenna is appropriate to use in especially global position satellite systems, life detection radar systems and wireless communication systems.

Vital signs modeling for Doppler radar cardiorespiratory monitoring

Microwave Doppler radar system is utilized to sense breathing and heartbeat of human beings to monitor their vital conditions. The Doppler radar not only receives vital sign signals but also acquires different additive and unwanted waves such as the signal of the extra motion of the body, clutter and electromagnetic noise. Making a mathematical model of received signal by a Doppler radar will be helpful to analyze vital conditions. In this paper we simulated the signal received by a Doppler radar system, and the results were compared with the vital signals obtained from a human by both a custom designed 24 GHz radar and a commercial respiratory transducer attached around the chest; in both time and frequency domains.

Adaptive Temporal Matched Filtering for Noise Suppression in Fiber Optic Distributed Acoustic Sensing

Distributed vibration sensing based on phase-sensitive optical time domain reflectometry (ϕ-OTDR) is being widely used in several applications. However, one of the main challenges in coherent detection-based ϕ-OTDR systems is the fading noise, which impacts the detection performance. In addition, typical signal averaging and differentiating techniques are not suitable for detecting high frequency events. This paper presents a new approach for reducing the effect of fading noise in fiber optic distributed acoustic vibration sensing systems without any impact on the frequency response of the detection system. The method is based on temporal adaptive processing of ϕ-OTDR signals. The fundamental theory underlying the algorithm, which is based on signal-to-noise ratio (SNR) maximization, is presented, and the efficacy of our algorithm is demonstrated with laboratory experiments and field tests. With the proposed digital processing technique, the results show that more than 10 dB of SNR values can be achieved without any reduction in the system bandwidth and without using additional optical amplifier stages in the hardware. We believe that our proposed adaptive processing approach can be effectively used to develop fiber optic-based distributed acoustic vibration sensing systems.

A K-band radar system for remote cardiorespiratory monitoring

A K-band radar system for detecting and monitoring cardiorespiratory signals of a human being is presented. The proposed radar system can be used in hospitals or homes to monitor the vital conditions of patients or elder people. If there is an abnormality, the radar system is capable of sending an alert signal to the remotely located monitoring terminal via the Internet. In this work, the settling time of the analog baseband signal is optimized. To increase the dynamic range of the K-band radar, an automatic gain control unit is successfully designed and implemented. Also, to avoid null points in measurements, both in-phase and quadrature signals are used in processing.

Field tests of a distributed acoustic sensing system based on temporal adaptive matched filtering of phase-sensitive OTDR signals

Distributed acoustic sensing (DAS) based on phase-sensitive optical time domain reflectometry (OTDR) is being widely used in several applications and attracting significant research interest. The main challenge in coherent detection-based phase-sensitive OTDR systems is the speckle-like background noise which impacts the detection performance and conventional techniques are not suitable for detecting weak vibrations under strong background noise. Recently, we proposed a temporal adaptive filtering (AMF) technique to reduce the background noise in phase-sensitive OTDR systems. The AMF method is based on linear filtering of the optical backscattered signals and the filter coefficients are computed from the observed data. In this study, after briefly reviewing the fundamental theory underlying the adaptive algorithm, we present the effectiveness and performance results of the AMF technique with the field tests. The impact of the diagonal loading level which is used to solve the ill-conditioning of the estimated noise covariance matrix is investigated. Performance dependence of the AMF technique on filter size and a comparison with the conventional trace averaging is presented. It is demonstrated that with the AMF technique, more than 10 dB of SNR values can be achieved without introducing additional optical amplifier stages in the DAS hardware. It is shown that intruder activities 25 m far away from a buried SMF-28 fiber underground can be detected with the proposed technique efficiently.

A 24-GHz Doppler sensor system for cardiorespiratory monitoring

In this paper, a 24-GHz Microwave band noninvasive sensor system for detecting and monitoring cardiorespiratory signals of patients is presented. The system consists of a sensor unit and a monitoring server. To demonstrate the proposal, a Doppler sensor unit operating at 24 GHz ISM band is fabricated. The fabricated radar unit shows below 6.2 % error for respiration rate when the distance between the patient and the radar system is below 1 m. The error increases to 7.3 % when the distance is increased to 2 m. To demonstrate the proposed medical sensor system, the life conditions of a subject is monitored. When an abnormality such as a stop breathing occurs, a warning signal is successfully generated automatically. In the case of an emergency, the health care workers can help the patients quicker.

A novel data adaptive detection scheme for distributed fiber optic acoustic sensing

We introduce a new approach for distributed fiber optic sensing based on adaptive processing of phase sensitive optical time domain reflectometry (Φ-OTDR) signals. Instead of conventional methods which utilizes frame averaging of detected signal traces, our adaptive algorithm senses a set of noise parameters to enhance the signal-to-noise ratio (SNR) for improved detection performance. This data set is called the secondary data set from which a weight vector for the detection of a signal is computed. The signal presence is sought in the primary data set. This adaptive technique can be used for vibration detection of health monitoring of various civil structures as well as any other dynamic monitoring requirements such as pipeline and perimeter security applications.

360° variable microwave phase shifter design for clutter cancellation circuitry of life detecting radar

The microwave lifesaving radar suffers from unwanted clutter signal from reflecting surrounding environment. To get rid of this problem, a microprocessor controlled clutter cancellation circuit is required. In this study, we designed a 360° microwave variable phase shifter to use in the clutter cancellation circuit. To cancel the incoming clutter, with this design the opposite phase and the same magnitude RF signal can be added to it at the radar receiver front-end. As a result, the detection capability and the range of the radar are increased.