An analog closed loop feedback system for improving the transmit to receive isolation of a generic circulator is described. The RF section of the circuit utilizes barium strontium titanate (BST) varactors to realize an antenna port tuner that reflects transmit power back into the circulator at the correct amplitude and phase to cancel the transmit signal leaking into the receiver port. Closed loop operation of the tuner is demonstrated using an Op Amp controller and a logarithmic detector at the receiver port. More than 33dB of additional self-interference cancellation was observed over that of the circulator for a 30MHz bandwidth QPSK transmit signal centered at 930MHz.

While there have been many years of research on the acoustoelectric effect, there has not been a successful approach or demonstration to provide a manufacturable, continuous wave (CW) acoustoelectric amplifier (AEA) with insertion gain. This letter will present the results of a 169.5-MHz surface acoustic wave (SAW) delay line on 128YX lithium niobate with an embedded monolithic coupled AEA (CAEA) demonstrating a terminal gain of 1.2 dB. The impedance-matched delay line without the CAEA has an insertion loss of 4.6 dB, and with the operational CAEA, the measured gain is 1.2 dB, yielding a net insertion gain of 5.8 dB. The CAEA uses approximately 137 mW dc power at the current peak operational gain. This letter will present experimental results of device performance and discuss the new embodiment for achieving the net insertion gain.

Technology advances provide new processes for the fabrication and application of novel materials to acoustoelectric devices. An important advancement would be the ability to produce practical integrated SAW AE amplifiers. Notably for practical applications, devices will need to be capable of operating with a continuous drift field applied rather than the most often-cited timed pulse approach and be cheaply manufacturable. With ultra-high mobility materials, such as graphene, power reduction can be achieved with the asymmetrical AE effect under a constant applied drift field. This paper will present a new embodiment of a graphene-based AE structure on LiNbO3. The first part of the paper will discuss the theory behind the SAW AE amplifier, including the critical film parameters for the maximum gain. The second part will present a new design and results from recent research efforts to conform graphene to have more ideal thin film parameters for the AE effect

Surface acoustic wave (SAW) sensors provide wireless and passive operation within small embodiments. With the recent adoption of the 4.2 to 4.4 GHz band for Wireless Avionics Intra-Communication (WAIC), SAW sensors are a promising solution for current and future demands of this application. Although some experiments on SAW sensors have been done at GHz frequencies, very little is known about SAW propagation, important parameters, and properties at these frequencies. No SAW sensors have been demonstrated at WAIC frequencies up to date. This paper presents the design and analysis of SAW delay lines, and reflector devices at 4.3 GHz. Unmatched SAW delay line response having 33 dB loss has been achieved; even though this may seem high - it is acceptable for SAW sensors within near-field ranges expected in air- and space-craft frames. SAW device simulation using the coupling of modes (COM) model [1], device fabrication feasibility, preliminary measurements, and a demonstration of wireless sensor operation at 4.3 GHz will be given. Transducer design topologies explored are shown with validation of transduction coupling at harmonics. Device embodiment and antenna design will also be presented.

The unwanted double transit echo (DTE) of a passive wireless reflective delay-line SAW device is efficiently suppressed by using a 3 rd harmonic-operating single phase unidirectional transducer (SPUDT). The frequency dependence of the DTE suppression level is shown by comparing devices with a Walsh-Hadamard-like reflector and a single-frequency Bragg reflector. A tunable dipole antenna is used to precisely tune the impedance required for the echo suppression.

Programmable surface acoustic wave (SAW) correlator filters are demonstrated for use with simultaneous transmit and receive (STAR) radios. Programmable binary phase shift keying (BPSK) is implemented using electronic switches in conjunction with fixed OFC codes. The prototype devices presented have moderate insertion loss, but using methods previously demonstrated, insertion loss can be reduced to make programmable correlator filters that are useable in practical communication systems.

Low loss orthogonal frequency coded (OFC) surface acoustic wave (SAW) correlator filters are demonstrated for use in conjunction with simultaneous transmit and receive (STAR) radios. Single phase unidirectional transducers (SPUDTs) are used to decrease insertion loss of conventional SAW correlators to facilitate use in the transmitter and receiver of STAR radios.

Surface acoustic wave (SAW) acoustoelectric (AE) theory and device embodiments have been demonstrated from the 1960s to the present. Technology has greatly advanced in new materials, growth and deposition, and nano films offering new opportunities for AE effects. The ability to produce a practical integrated SAW AE amplifier in filters and resonators would provide new opportunities for SAW RF filters and oscillators. In particular, the AE amplifier is one component of producing a SAW-based simultaneous transmit and receive (STAR) radio at approximately 1 GHz using spread spectrum RF filtering. This paper will present research efforts on development of a thin film AE amplifier on LiNbO 3 . The first part of the paper will discuss the boundaries and coupled-interactions of the many design parameters for practical AE thin film amplifiers. The second part of the paper will provide the most recent results of the AE amplifier research efforts using graphene on lithium niobate.

Experimental results of the measured surface acoustic wave (SAW) acoustoelectric effect (AE) using single-layer thin-film graphene on 128°, -cut, and -propagating lithium niobate (128-LN) are presented. The use of an AE amplifier in SAW communication devices, especially in gigahertz bands, could make fundamental advancements in radios, sensors, and other applications. Experimental results at 1350 MHz show the delay line asymmetry of 3 dB, given as the ratio of the forward versus reverse peak SAW frequency response, with an applied dc voltage on the graphene film.

Passive, wireless surface acoustic wave (SAW) sensor systems can be approached from a radar perspective, where the SAW device is thought of as a cooperative target. This paper investigates the use of a commercial-off-the-shelf software defined radio to interrogate wireless SAW sensors with a randomly generated interrogation pulse. The USRP B200mini is utilized as the transceiver platform with custom field-programmable gate array (FPGA) modifications to generate the random interrogation waveform and provide synchronization and buffering to the received signal. Each transmit sample bit in the FPGA is fed by an independent linear-feedback shift register, which generates pseudo-random I and Q samples for the interrogation pulse. An RF daughterboard has also been developed and integrated with the B200mini to increase the transmit power, provide filtering of the RF signals, and switch a signal antenna between the transmit and receive channels. Radio control and matched filter correlator post-processing are accomplished using Python. Design and implementation details for the FPGA modifications, RF daughterboard, and post-processing are discussed. The system is demonstrated by wirelessly interrogating SAW temperature sensors at 915 MHz.

Over the past 15 years, our group has been developing passive wireless multi-sensor systems based on surface acoustic wave (SAW) encoded delay line sensors. The work has been principally developed through NASA SBIR/STTR programs, NASA developmental contracts, and NASA graduate fellowships. This period of effort has resulted in the development of orthogonal frequency coded RFID sensor devices, specialized transceiver (reader) technology, and adaptive filter correlator post processing techniques. Operational systems and devices were demonstrated from 250 MHz to 1 GHz.

Over the last 13 years, our group has been developing passive, wireless SAW device technology and the system has been continually evolving, providing gains in all aspects of the technology. Initial system proof-of-concept moved from 250 MHz to the current 915 MHz, which is a good choice from device and antenna size, and wireless RF component availability. Range has increased from less than a meter, to over 25 meters, and current testing is moving towards 100 meters for a NASA application. Several successful custom transceivers were developed and delivered to NASA and the US government. From custom-made systems, current efforts use a software defined radio (SDR) Universal Software Radio Peripheral (USRP) transceiver approach as the interrogator-receiver. This commercially off the shelf (COTS) hardware greatly reduces development time and cost and ensures rapid future improvements. The advantageous and SDR approach will be discussed, which include RF parameter adaptability in center frequency and bandwidth. The current status of the SAW wireless temperature sensors sensitivity and range will be used as the performance parameter measure, since it is the most ubiquitous of all sensor applications.

The universal software radio peripheral (USRP) is a versatile software defined radio (SDR) platform, developed by Ettus Research™, which is intended for a wide variety of applications ranging from communication links to RADAR. We have investigated another application of the USRP by implementing a transceiver capable of interrogating passive, wireless surface acoustic wave (SAW) sensors centered at 915MHz. Interrogation of wideband orthogonal frequency coded (OFC) SAW sensors imposes strict requirements on the timing and synchronization of the transceiver. In the standard mode of operation, samples are generated and streamed between the USRP and host computer, introducing latency and bandwidth limitations due to the sampling bus. To achieve the performance required for this application, the USRP FPGA has been modified to introduce new functionality. Extraction of the sensor temperature is accomplished with a custom matched filter correlator. The system is capable of interrogating multiple sensors and can quickly reconfigure the USRP. Demonstration of the USRP wireless sensor system is achieved by interrogating wireless SAW OFC sensors at 915MHz and extracting the sensor temperature.

Modern software defined radio (SDR) technologies have enabled surface acoustic wave (SAW) sensor interrogation systems that are small, inexpensive, and fully integrated. The universal software radio peripheral (USRP) is available as a commercial-off-the-shelf (COTS) SDR that can be programmed to fit a wide variety of applications and needs. Recent work at the University of Central Florida has demonstrated the USRP B200 as a SAW sensor interrogator. This paper expands upon previous efforts by implementing a standalone interrogation platform which utilizes the USRP B200 and embedded microcomputer. Recent advances in embedded processing platforms have enabled full Linux environments to be run, enabling high performance computation in a compact package. One such embedded platform, the MinnowBoard MAX, has been employed to perform the complex matched filter correlator post processing techniques as well as handle programming and communication with the USRP. The unit is self contained and can be operated without a traditional Desktop or Laptop. Performance of the interrogator has also been improved by adding and external RF switch and amplifier. The system is demonstrated by interrogating orthogonal frequency coded (OFC) SAW sensors at 915MHz and extracting the sensor temperature.

This paper will present current efforts on wireless passive surface acoustic wave (SAW) sensor transceiver development for aerospace applications. Our group's SAW sensor work has been sponsored by NASA for the past ten years in efforts to develop wireless sensing for ground base and space exploration in extreme environments. The devices are radiation hard and work from cryogenic to several hundred degrees centigrade with standard device processing. The focus of this paper will be on a synchronous, pulsed correlator transceiver for interrogation of SAW delay-line sensors. The 915-MHz system has a bandwidth of 15 MHz and uses a pulsed noise-generated signal of 1-mu s duration. The design principles, system analysis, and receiver measurements are given. The prediction of signal-to-noise ratio versus range is shown for given system parameters. The system development leading to the first testing of SAW liquid level sensors at NASA KSC will be discussed.

The interactive technical electronic book, TechEBook, currently under development at the University of Central Florida (UCF), provides a useful tool for engineers and scientists through unique features compared to the most used traditional electrical circuit textbooks available in the market. TechEBook has comprised the two worlds of classical circuit books and an interactive operating platform such as iPads, laptops and desktops utilizing Java Virtual Machine operator. The TechEBook provides an interactive applets screen that holds many modules, in which each had a specific application in the self learning process. This paper describes two of the interactive techniques in the TechEBook known as, Practical Relevance Modules (PRM) and Design Modules (DM). The Practical Relevance Module will assist the readers to learn electrical circuit analysis and to understand the practical application of the electrical network theory through solving real world examples and problems. The Design Module will help students design real-life problems. These modules will be displayed after each section in the TechEBook for the user to relate his/her understanding with the outside world, which introduces the term me-applying and me-designing, as a comprehensive full experience for self or individualized education. The main emphasis of this paper is the PRM while the DM will be discussed in brief. A practical example of applying the PRM and DM features is discussed as part of a basic electrical engineering course currently given at UCF and results show improved student performances in learning materials in Electrical Circuits. In the future, such modules can be redesigned to become highly interactive with illustrated animations.

Previous work has been presented on passive wireless surface-acoustic-wave (SAW) sensors using the orthogonal frequency coding (OFC) technique (Malocha et ah, Proc. Int. Soc. Opt. Eng. (SPIE), Aug. 23-27,2004, vol. 2, pp. 1082-1085), Pavlina et al., Proc. IEEE Int. Conf. RFID, 2009, pp. 110-115). This paper will present a SAW sensor correlator system and its key operational parameters. Description of the radio frequency (RF) transceiver system and the OFC SAW temperature sensors is provided for parameter characterization. The system is based on a software radio approach and an analysis of the analog-to-digital converter (ADC) parameters and receiver noise in temperature extraction is presented. Initial experimental results for a four-sensor system operating over a 280°C range are given.

Signal-to-noise ratio (SNR) is a valuable figure of merit in determining the operating scope of infrared detectors. Antenna-couple metal-oxide-metal diodes have been shown to detect infrared radiation without cooling or applied bias, but so far have been hampered by their SNR. This paper details a comprehensive study of the fabrication parameters that control the formation of the tunneling oxide barrier to optimize the performance of these detectors. Since the tunneling barrier affects both current-voltage and infrared detection characteristics, fabrication parameters can be optimized to improve device performance. The current-voltage characteristics of the devices are detailed in this paper; resistance, nonlinearity, and curvature coefficient are parameterized on fabrication procedures. Infrared detection characteristics are detailed and SNR is studied as a function of device nonlinearity and biasing conditions.

This study investigated the various methods involved in creating an intelligent tutor for the University of Central Florida Web Applets (UCF Web Applets), an online environment where student can perform and/or practice experiments. After conducting research into various methods, two major models emerged. These models include: 1) solving the problem for the student 2) helping the student when they become stymied and unable to solve the problem. A storyboard was created to show the interactions between the student and system along with a list of features that were desired to be included in the tutoring system. From the storyboard and list of features, an architecture was created to handle all of the interactions and features. After the initial architecture was designed, the development of the actual system was started. The architecture underwent a several iterations to conclude with a working system, EINO. EINO is an intelligent tutoring system integrated into the UCF Web Applets. The final architecture of EINO incorporated a case-based reasoning system to perform pattern recognition on the student’s input into the UCF Web Applets. The interface that the student interacts with was created using Flash™. EINO was implemented in three of the experiments from the UCF Web Applets. A series of tests were performed on the EINO tutoring system to determine that the system could actually perform each and every one of the features listed initially. The final test was a simulation of how the EINO would perform in “real life.” Test subjects with the same educational level as the target group were chosen to spend an unlimited time using each of the three experiments. A single experiment is designed to reinforce a topic currently being covered by the book. Each of the test subjects filled out a survey on every lab to determine if the EINO system produced a helpful output.

This chapter contains sections titled: Various Types of Noise that Appear in Images Spatial Filtering Spatial Frequency Filtering Image Restoration