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(1 - 16 of 16)
- Title
- SAW Correlator Temperature Compensation Using a Pulse Width Modulated Temperature Controller.
- Creator
-
Betancourt, Daniel, Weeks, Arthur, Malocha, Donald, Richie, Samuel, Gong, Xun, University of Central Florida
- Abstract / Description
-
A Surface Acoustic Wave (SAW) correlator built on a Lithium Niobate substrate is temperature compensated in order to maintain a constant center frequency. Frequency shifts as a result of temperature variations limit device performance. An Arduino(&)#174;-based PWM temperature controller is developed to read the device temperature from a resistance temperature detector located on the SAW wafer and to regulate its temperature to a specified setpoint by providing current to a heater which is co...
Show moreA Surface Acoustic Wave (SAW) correlator built on a Lithium Niobate substrate is temperature compensated in order to maintain a constant center frequency. Frequency shifts as a result of temperature variations limit device performance. An Arduino(&)#174;-based PWM temperature controller is developed to read the device temperature from a resistance temperature detector located on the SAW wafer and to regulate its temperature to a specified setpoint by providing current to a heater which is co-located with the temperature sensor on the SAW correlator substrate. The final temperature controller achieves frequency shifts of 0.013 MHz from room temperature with a worst-case PPM experienced over 30(&)deg;C of temperature variation of 0.48 PPM/(&)deg;C. Linear and non-linear plant models are developed successfully to predict the device's temperature based on any input setpoint. Although there are alternatives to limit temperature drift at different temperatures, this thesis presents a simple method that works on a standard Lithium Niobate substrate.
Show less - Date Issued
- 2019
- Identifier
- CFE0007787, ucf:52331
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007787
- Title
- ANALYSIS AND DESIGN OF MINIATURIZED RF SAW DUPLEXER PACKAGE.
- Creator
-
Dong, Hao, Wu, Thomas, University of Central Florida
- Abstract / Description
-
This dissertation provides a comprehensive methodology for accurate analysis and design of miniaturized radio frequency (RF) surface acoustic wave (SAW) duplexer package. Full-wave analysis based on the three dimensional (3-D) finite element method (FEM) is successfully applied to model the package. The die model is obtained by combining the acoustics and die busbars parasitics models. The acoustics model is obtained using the coupling-of-models (COM) technique. The die busbars, bonding wires...
Show moreThis dissertation provides a comprehensive methodology for accurate analysis and design of miniaturized radio frequency (RF) surface acoustic wave (SAW) duplexer package. Full-wave analysis based on the three dimensional (3-D) finite element method (FEM) is successfully applied to model the package. The die model is obtained by combining the acoustics and die busbars parasitics models. The acoustics model is obtained using the coupling-of-models (COM) technique. The die busbars, bonding wires and printed circuit board (PCB) are modeled using full-wave analysis. After that, the models of package, die, and bonding wires are assembled together to get the total response. To take into account the mutual couplings, the methodology is extended to model the package, die busbars, and bonding wires together. The advantages and disadvantages of the methodology are also discussed. Based on the methodology, the Korea personal communication system (KPCS) duplexer is analyzed and designed. The isolation of KPCS duplexer package is significantly improved by redesigning inner ground plane, bonding wire scheme and ground via. A KPCS duplexer package is designed and excellent transmitter to receiver isolation in the transmission band is achieved. Simulation and measurement results are compared, and excellent agreement is found. Although we focus on investigating the methods to improve the isolation, the passband performance is also improved. The methodology is also successfully used for flip chip duplexer. The simulation results from our assembling method match the measurement results very well. Optimization method is applied to improve the transmit band isolation. With the new package and die design, the transmit band isolation can be improved from -53.6 dB to -65.2 dB. Based on the new package, the effect of the Rx ground trace on the isolation is investigated and the transmit band isolation can achieve -67.3 dB with the modification of the Rx ground trace. The technique developed in this dissertation reduces the design cycle time greatly and can be applied to various RF SAW device packages.
Show less - Date Issued
- 2005
- Identifier
- CFE0000688, ucf:46493
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000688
- Title
- PASSIVE WIRELESS SAW SENSORS WITH NEW AND NOVEL REFLECTOR STRUCTURES: DESIGN AND APPLICATIONS.
- Creator
-
Kozlovski, Nikolai, Weeks, Arthur, University of Central Florida
- Abstract / Description
-
Surface acoustic wave (SAW) devices are a solution for today's ever growing need for passive wireless sensors. Orthogonal frequency coding (OFC) together with time division multiplexing (TDM) provides a large number of codes and coding algorithms producing devices that have excellent collision properties. Novel SAW noise-like refector (NLR) structures with pulse position modulation (PPM) are shown to exhibit good auto- and cross-correlation, and anti-collision properties. Multi-track, multi...
Show moreSurface acoustic wave (SAW) devices are a solution for today's ever growing need for passive wireless sensors. Orthogonal frequency coding (OFC) together with time division multiplexing (TDM) provides a large number of codes and coding algorithms producing devices that have excellent collision properties. Novel SAW noise-like refector (NLR) structures with pulse position modulation (PPM) are shown to exhibit good auto- and cross-correlation, and anti-collision properties. Multi-track, multi-transducer approaches yield devices with adjustable input impedances and enhanced collision properties for OFC TDM SAW sensor devices. Each track-transducer is designed for optimum performance for loss, coding, and chip reflectivity. Experimental results and theoretical predictions confirm a constant Q for SAW transducers for a given operational bandwidth, independent of device and transducer embodiment. Results on these new NLR SAW structures and devices along with a new novel 915 MHz transceiver based on a software radio approach was designed, built, and analyzed. Passive wireless SAW temperature sensors were interrogated and demodulated in a spread spectrum correlator system using a new adaptive filter. The first-ever SAW OFC four-sensor operation was demonstrated at a distance of 1 meter and a single sensor was shown to operate up to 3 meters. Comments on future work and directions are also presented.
Show less - Date Issued
- 2011
- Identifier
- CFE0003636, ucf:48851
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003636
- Title
- DESIGN, ANALYSIS AND IMPLEMENTATION OF ORTHOGONAL FREQUENCY CODING IN SAW DEVICES USED FOR SPREAD SPECTRUM TAGS AND SENSORS.
- Creator
-
Puccio, Derek, Malocha, Don, University of Central Florida
- Abstract / Description
-
SAW based sensors can offer wireless, passive operation in numerous environments and various device embodiments are employed for retrieval of the sensed data information. Single sensor systems can typically use a single carrier frequency and a simple device embodiment, since tagging is not required. In a multi-sensor environment, it is necessary to both identify the sensor and retrieve the sensed information. This dissertation presents the concept of orthogonal frequency coding (OFC) for...
Show moreSAW based sensors can offer wireless, passive operation in numerous environments and various device embodiments are employed for retrieval of the sensed data information. Single sensor systems can typically use a single carrier frequency and a simple device embodiment, since tagging is not required. In a multi-sensor environment, it is necessary to both identify the sensor and retrieve the sensed information. This dissertation presents the concept of orthogonal frequency coding (OFC) for applications to SAW sensor technology. OFC offers all advantages inherent to spread spectrum communications including enhanced processing gain and lower interrogation power spectral density (PSD). It is shown that the time ambiguity in the OFC compressed pulse is significantly reduced as compared with a single frequency tag having the same code length and additional coding can be added using a pseudo-noise (PN) sequence. The OFC approach is general and should be applicable to many differing SAW sensors for temperature, pressure, liquid, gases, etc. Device embodiments are shown and a potential transceiver is described. Measured device results are presented and compared with COM model predictions to demonstrate performance. Devices are then used in computer simulations of the proposed transceiver design and the results of an OFC sensor system are discussed.
Show less - Date Issued
- 2006
- Identifier
- CFE0001205, ucf:46952
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001205
- Title
- SAW REFLECTIVE TRANSDUCERS AND ANTENNAS FOR ORTHOGONAL FREQUENCY CODED SAW SENSORS.
- Creator
-
Santos, Bianca Maria, Malocha, Donald, University of Central Florida
- Abstract / Description
-
Passive sensors that vary its impedance per measured parameter may be used with surface acoustic wave (SAW) reflective transducers (SRT) for wireless acquisition of the measurand. The device is composed of two transducers, where one, which may be attached to an antenna, is used to launch the wave within the device substrate, and the other is where the sensor load is attached to. The latter is able to reflect the incident wave. How much power is reflected is determined by the attached sensor...
Show morePassive sensors that vary its impedance per measured parameter may be used with surface acoustic wave (SAW) reflective transducers (SRT) for wireless acquisition of the measurand. The device is composed of two transducers, where one, which may be attached to an antenna, is used to launch the wave within the device substrate, and the other is where the sensor load is attached to. The latter is able to reflect the incident wave. How much power is reflected is determined by the attached sensor load. Amplitude variations as well as peak frequency variations of the SRT reflectivity response are explored in this thesis. SAW passive temperature sensors with an orthogonal frequency coded (OFC) time response were previously investigated and prove to be ideal for use in harsh environments. Each sensor is distinguishable from the other due to the OFC code embedded within its time response. However, this coding technique poses a difficulty in designing antennas for the sensor due to its inherently wide bandwidth, and capacitive, non-uniform input impedance. This work covers antenna design and testing for the 250MHz wireless temperature acquisition prototype with a 28% fractional bandwidth, and for the 912MHz system which has 10% fractional bandwidth. Apart from the tag, antennas for the transmitter and receiver were designed for 50 Ohm matching with the required bandwidth maintained. Wireless temperature acquisition runs for the 250MHz prototype were successfully performed and show good agreement with measurements made by a thermocouple. Since a transceiver for the 912MHz system is not complete, the performance of the antennas was gauged by observing the signal transmitted wirelessly by the SAW tag and by comparing this with the sensor time response measured directly by a vector network analyzer.
Show less - Date Issued
- 2009
- Identifier
- CFE0002649, ucf:48199
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002649
- Title
- FATE OF NITROGEN AND PHOSPHORUS SPECIES FROM A BLACK AND GOLDTM NUGGET MIX IN A LABORATOY COLUMN SIMULATED SEPTIC TANK DRAINFIELD.
- Creator
-
Shah, Timir, Wanielista, Martin, University of Central Florida
- Abstract / Description
-
The presence of nitrates and phosphorus in ground water is a worldwide problem. A septic tank with drainfield that is conventionally designed does not typically remove nitrogen in the form of nitrates. The main risks are in "Blue baby" syndrome and suspected carcinogenic effect of nitrates on humans and the nutrient enrichment of receiving waters. In some areas nitrate and phosphorus removal are essentially required. Thus the information in this report concentrates on using media in the...
Show moreThe presence of nitrates and phosphorus in ground water is a worldwide problem. A septic tank with drainfield that is conventionally designed does not typically remove nitrogen in the form of nitrates. The main risks are in "Blue baby" syndrome and suspected carcinogenic effect of nitrates on humans and the nutrient enrichment of receiving waters. In some areas nitrate and phosphorus removal are essentially required. Thus the information in this report concentrates on using media in the drainfield for the removal of nitrogen and phosphorus. Extensive work has been conducted in the past few decades in order to find suitable media for denitrification with high selectivity towards nitrogen. Column experiments were conducted at the University of Central Florida to simulate the actual septic tank drainfield using mixes of fine sand. In one of the columns Sawdust and Tire Crumb were added to the Sand (STS) and in the other column Paper and Tire Crumb were added to the Sand (STP). Tire crumb was added as a carbon source required for better denitrification and for sorption. The columns were dosed daily using regular septic tank effluent and it was a continuous batch system. Samples were taken after a hydraulic retention time (HRT) of 24 hours and comparisons were made of the effluent with the influent to show percentage removal of nitrogen (nitrates, ammonia and total nitrogen), phosphorus (ortho-phosphorus and total phosphorus) and BOD. STS and STP columns showed more than 90% removal for all parameters (nitrates, ammonia, total nitrogen, ortho-phosphorus, total phosphorus, BOD). The results indicate that the investigated media blend (Black and GoldTM Nugget Mix) has the potential for successful application in full scale operations. It is recommended that Black and GoldTM Nugget Mix be used to achieve the required removal of the nutrients.
Show less - Date Issued
- 2007
- Identifier
- CFE0001824, ucf:47335
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001824
- Title
- DESIGN AND SIMULATION FOR ENCODED PN-OFC SAW SENSOR SYSTEMS.
- Creator
-
Pavlina, John, Malocha, Donald, University of Central Florida
- Abstract / Description
-
Surface acoustic wave (SAW) sensors provide versatility in that they can offer wireless, passive operation in numerous environments. Various SAW device embodiments may also be employed for retrieval of the sensed data. Single sensor systems typically use a single carrier frequency and a simple device embodiment since tagging is not required. However, it is necessary in a multi-sensor environment to both identify the sensor and retrieve the information. Overlapping sensor data signals in time...
Show moreSurface acoustic wave (SAW) sensors provide versatility in that they can offer wireless, passive operation in numerous environments. Various SAW device embodiments may also be employed for retrieval of the sensed data. Single sensor systems typically use a single carrier frequency and a simple device embodiment since tagging is not required. However, it is necessary in a multi-sensor environment to both identify the sensor and retrieve the information. Overlapping sensor data signals in time and frequency present problems when attempting to collect the sensed data at the receiver. This dissertation defines a system simulation environment exclusive to SAW sensors. The major parameters associated with a multi-device system include the transmitter, the channel, and the receiver characteristics. These characteristics are studied for implementation into the simulation environment. A coupling of modes (COM) model for SAW devices is utilized as an accurate software representation of the various SAW devices. Measured device results are presented and compared with COM model predictions to verify performance of devices and system. Several coding techniques to alleviate code collisions and detection errors were investigated and evaluated. These specialized techniques apply the use of time, frequency, and spatial diversity to the devices. Utilizing these multiple-access techniques a multi-device system is realized. An optimal system based on coding technique, frequency of operation, range, and related parameters is presented. Funding for much of this work was provided through STTR contracts from NASA Kennedy Space Center.
Show less - Date Issued
- 2010
- Identifier
- CFE0003124, ucf:48630
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003124
- Title
- ULTRA-WIDEBAND ORTHOGONAL FREQUENCY CODED SAW CORRELATORS.
- Creator
-
Gallagher, Daniel, Malocha, Donald, University of Central Florida
- Abstract / Description
-
Ultra–wideband (UWB) communication new technology with ability to share the FCC allocated frequency spectrum, large channel capacity and data rate, simple transceiver architecture and high performance in noisy environments. Such communication advantages have paved the way for emerging wireless technologies such as wireless high definition video streaming, wireless sensor networks and more. This thesis examines orthogonal frequency coded surface acoustic wave (SAW) correlators for use in...
Show moreUltra–wideband (UWB) communication new technology with ability to share the FCC allocated frequency spectrum, large channel capacity and data rate, simple transceiver architecture and high performance in noisy environments. Such communication advantages have paved the way for emerging wireless technologies such as wireless high definition video streaming, wireless sensor networks and more. This thesis examines orthogonal frequency coded surface acoustic wave (SAW) correlators for use in advanced UWB communication systems. Orthogonal frequency coding (OFC) and pseudo-noise (PN) coding provides a means for UWB spreading of data. The use of OFC spectrally spreads a PN sequence beyond that of CDMA because of the increased bandwidth; allowing for improved correlation gain. The transceiver approach is still very similar to that of the CDMA approach but provides greater code diversity. Use of SAW correlators eliminates many of the costly components that are needed in the IF block in the transmitter and receiver, and reduces much of the signal processing requirements. The OFC SAW correlator device consists of a dispersive OFC transducer and a wideband output transducer. The dispersive filter was designed using seven contiguous chip frequencies within the transducer. Each chip is weighted in the transducer to account for the varying conductance of the chips and to compensate for the output transducer apodization. Experimental correlator results of an OFC SAW correlation filter are presented. The dispersive filter is designed using seven contiguous chip frequencies within the transducer. SAW correlators with fractional bandwidth of approximately 29% were fabricated on lithium niobate (LiNbO3) having a center frequency of 250 MHz and the filter has a processing gain of 49. A coupling of modes (COM) model is used to predict the experimental SAW filter response. Discussion of the filter design, analysis and measurements are presented. Results are shown for operation in a matched filter correlator for use in an UWB communication system and compared to predictions.
Show less - Date Issued
- 2007
- Identifier
- CFE0001820, ucf:47338
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001820
- Title
- Programmable Low Loss Orthogonal Frequency Coded Surface Acoustic Wave Correlator Filters.
- Creator
-
Smith, Marshall, Malocha, Donald, Weeks, Arthur, Sundaram, Kalpathy, Richie, Samuel, Youngquist, Robert, University of Central Florida
- Abstract / Description
-
Simultaneous Transmit and Receive (STAR) communication is being developed as a means of improving spectral efficiency in wireless communication systems. If the obstacle of self-interference can be sufficiently overcome, it is possible to double the spectral efficiency of an equivalent time or frequency division duplexed system. Spread spectrum techniques can reduce self-interference by using orthogonal or pseudo-orthogonal codes to encode the transmit signal and decode the receive signal...
Show moreSimultaneous Transmit and Receive (STAR) communication is being developed as a means of improving spectral efficiency in wireless communication systems. If the obstacle of self-interference can be sufficiently overcome, it is possible to double the spectral efficiency of an equivalent time or frequency division duplexed system. Spread spectrum techniques can reduce self-interference by using orthogonal or pseudo-orthogonal codes to encode the transmit signal and decode the receive signal.Hardware correlator filters are developed for use with STAR radio systems using orthogonal frequency coded (OFC) surface acoustic wave (SAW) devices. OFC is a type of spread spectrum communication that can be implemented using SAW transducers to create a correlator filter, also known as a matched filter. OFC allows code division multiple access and processing gain, similar to other spread spectrum techniques, but is more well-suited to low loss inline SAW design due to the use of multiple orthogonal carriers.The development of low loss fixed code OFC SAW correlator filters is documented, including design criteria and multiple approaches that progressively reduce insertion loss. Using the results from progressive designs and experiments, a pair of correlator filters with matched codes are presented with approximately 6 dB insertion loss at 950 MHz.A second development focusing on OFC SAW correlator filters with programmable codes using RF switches is also described. The programmable correlators use a fixed OFC code with programmable binary phase shift keying (BPSK), and demonstrate positive results. The programmable correlators presented require less than 1 mW of DC power.
Show less - Date Issued
- 2018
- Identifier
- CFE0007768, ucf:52372
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007768
- Title
- Surface Acoustic Wave (SAW) Cryogenic Liquid and Hydrogen Gas Sensors.
- Creator
-
Fisher, Brian, Malocha, Donald, Gong, Xun, Likamwa, Patrick, Richie, Samuel, Youngquist, Robert, University of Central Florida
- Abstract / Description
-
This research was born from NASA Kennedy Space Center's (KSC) need for passive, wireless and individually distinguishable cryogenic liquid and H2 gas sensors in various facilities. The risks of catastrophic accidents, associated with the storage and use of cryogenic fluids may be minimized by constant monitoring. Accidents involving the release of H2 gas or LH2 were responsible for 81% of total accidents in the aerospace industry. These problems may be mitigated by the implementation of a...
Show moreThis research was born from NASA Kennedy Space Center's (KSC) need for passive, wireless and individually distinguishable cryogenic liquid and H2 gas sensors in various facilities. The risks of catastrophic accidents, associated with the storage and use of cryogenic fluids may be minimized by constant monitoring. Accidents involving the release of H2 gas or LH2 were responsible for 81% of total accidents in the aerospace industry. These problems may be mitigated by the implementation of a passive (or low-power), wireless, gas detection system, which continuously monitors multiple nodes and reports temperature and H2 gas presence. Passive, wireless, cryogenic liquid level and hydrogen (H2) gas sensors were developed on a platform technology called Orthogonal Frequency Coded (OFC) surface acoustic wave (SAW) radio frequency identification (RFID) tag sensors. The OFC-SAW was shown to be mechanically resistant to failure due to thermal shock from repeated cycles between room to liquid nitrogen temperature. This suggests that these tags are ideal for integration into cryogenic Dewar environments for the purposes of cryogenic liquid level detection. Three OFC-SAW H2 gas sensors were simultaneously wirelessly interrogated while being exposed to various flow rates of H2 gas. Rapid H2 detection was achieved for flow rates as low as 1ccm of a 2% H2, 98% N2 mixture. A novel method and theory to extract the electrical and mechanical properties of a semiconducting and high conductivity thin-film using SAW amplitude and velocity dispersion measurements were also developed. The SAW device was shown to be a useful tool in analysis and characterization of ultrathin and thin films and physical phenomena such as gas adsorption and desorption mechanisms.?
Show less - Date Issued
- 2012
- Identifier
- CFE0004536, ucf:49258
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004536
- Title
- A Novel Nonlinear Mason Model and Nonlinear Distortion Characterization for Surface Acoustic Wave Duplexers.
- Creator
-
Chen, Li, Wahid, Parveen, Malocha, Donald, Richie, Samuel, Briot, Jean-Bernard, University of Central Florida
- Abstract / Description
-
Surface acoustic wave (SAW) technology has been in use for well over one century. In the last few decades, due to its low cost and high performance, this technology has been widely adopted in modern wireless communication systems, to build filtering devices at radio frequency (RF). SAW filters and duplexers can be virtually found inside every mobile handset. SAW devices are traditionally recognized as passive devices with high linear signal processing behavior. However, recent deployments of...
Show moreSurface acoustic wave (SAW) technology has been in use for well over one century. In the last few decades, due to its low cost and high performance, this technology has been widely adopted in modern wireless communication systems, to build filtering devices at radio frequency (RF). SAW filters and duplexers can be virtually found inside every mobile handset. SAW devices are traditionally recognized as passive devices with high linear signal processing behavior. However, recent deployments of third generation (3G) and fourth generation (4G) mobile networks require the handsets to handle an increasing number of frequency bands with more complex modulation /demodulation schemes and higher data rate for more subscribers. These requirements directly demand more stringent linearity specifications on the front end devices, including the SAW duplexers. In the past, SAW duplexer design was based on empirically obtained design rules to meet the linearity specifications. Lack of predictability and an understanding of the root cause of the nonlinearity have limited the potential applications of SAW duplexers. Therefore, research on the nonlinearity characterization and an accurate modeling of SAW nonlinearity for mobile device applications are very much needed.The Ph.D. work presented here primarily focuses on developing a general nonlinear model for SAW resonators/duplexers. Their nonlinear characteristics were investigated by measuring the harmonic and intermodulation distortions of resonators. A nonlinear Mason model is developed and the characterization results are integrated into SAW duplexer design flows to help to simulate the nonlinear effects accurately and improve the linearity performance of the products.In this dissertation, first, a novel nonlinear Mason equivalent circuit model including a third order nonlinear coefficient in the wave propagation is presented. Next, the nonlinear distortions of SAW resonators are analyzed by measuring large-signal harmonic and intermodulation spurious emission on resonators using a wafer probe station. The influence of the setups on the measurement reliability and reproducibility is discussed. Further, the nonlinear Mason model is validated by comparing its simulation results with harmonic and intermodulation measurements on SAW resonators and a WCDMA Band 5 duplexer. The Mason model developed and presented here is the first and only nonlinear physical model for SAW devices based on the equivalent circuit approach. By using this new model, good simulation measurement agreements are obtained on both harmonic and intermodulation distortions for SAW resonators and duplexers. These outcomes demonstrate the validity of the research on both the characterization and modeling of SAW devices. The result obtained confirms that the assumption of the representation of the 3rd order nonlinearity in the propagation by a single coefficient is valid.
Show less - Date Issued
- 2013
- Identifier
- CFE0004967, ucf:49565
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004967
- Title
- Passive, Wireless SAW OFC Strain Sensor and Software Defined Radio Interrogator.
- Creator
-
Humphries, James, Malocha, Donald, Richie, Samuel, Weeks, Arthur, Sundaram, Kalpathy, Saha, Haripada, University of Central Florida
- Abstract / Description
-
Surface acoustic wave (SAW) devices have exhibited unique capabilities to meet the demands for many applications due to the inherent properties of SAW devices and piezoelectric materials. In particular, SAW devices have been adapted as sensors that can be configured to operate both passively and wirelessly. SAW sensors can be operated in harsh environmental extremes where typical sensor technologies are not able to operate. Because the sensors are passive, a radio transceiver is required to...
Show moreSurface acoustic wave (SAW) devices have exhibited unique capabilities to meet the demands for many applications due to the inherent properties of SAW devices and piezoelectric materials. In particular, SAW devices have been adapted as sensors that can be configured to operate both passively and wirelessly. SAW sensors can be operated in harsh environmental extremes where typical sensor technologies are not able to operate. Because the sensors are passive, a radio transceiver is required to interrogate the sensor and receive the reflected response that has been modulated by the SAW device. This dissertation presents the design of a passive, wireless SAW OFC strain sensor and software defined radio (SDR) interrogator.A SAW strain sensor has been designed and tested using orthogonal frequency coding (OFC) on YZ-LiNbO3. OFC for SAW devices has been previously developed at UCF and provides both frequency and time diversity in the RFID code as well as providing processing gain to improve the sensor SNR. Strain effects in SAW devices are discussed and two sensor embodiments are developed. The first embodiment is a cantilever structure and provides insight on how strain effects the SAW device. The second embodiment bonds the SAW die directly to a test structure to measure the strain on the structure. A commercial wired foil strain gage provides a performance comparison and shows that the wireless SAW sensor performs comparably. A commercial-off-the-shelf SDR platform has been employed as the SAW sensor interrogator. The Universal Software Radio Peripheral (USRP) is available in many embodiments and is capable of operation of to 6GHz and up to 160MHz of bandwidth. In particular, the USRP B200 is utilized as the RF transceiver platform. Custom FPGA modifications are discussed to fully utilize the USRP B200 bandwidth (56MHz) and synchronize the transmit and receive chains. External hardware has also been introduced to the B200 to improve RF performance, all of which are incorporated into a custom enclosure. Post-processing of the SAW sensor response is accomplished in Python using a matched filter correlator routine to extract sensor information. The system is demonstrated by interrogating wireless OFC SAW temperature and strain sensors at 915MHz.
Show less - Date Issued
- 2016
- Identifier
- CFE0006329, ucf:51560
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006329
- Title
- NANOCLUSTER THIN-FILMS FOR SENSOR APPLICATIONS.
- Creator
-
Serritella, Joseph, Malocha, Donald, University of Central Florida
- Abstract / Description
-
The ability to sense gas such as methane can provide an early warning system to protect human lives. High demand for the ability to sense the world around us has provided an extensive area of research for sensor technology. In particular, current sensor technology, specifically for methane, has provided sensors that require a heated environment to function. The majority of current methane sensors function at temperatures between 150[degrees]C and 450[degrees]C . This thesis will explore an...
Show moreThe ability to sense gas such as methane can provide an early warning system to protect human lives. High demand for the ability to sense the world around us has provided an extensive area of research for sensor technology. In particular, current sensor technology, specifically for methane, has provided sensors that require a heated environment to function. The majority of current methane sensors function at temperatures between 150[degrees]C and 450[degrees]C . This thesis will explore an approach to produce a room temperature methane sensor. This research will investigate techniques to create a sensor that is responsive to methane at 23[degrees]C. The approach will use the integration of a very thin film, which changes its resistive properties when methane gas is applied, deposited atop the surface of a piezoelectric substrate. An aluminum thin film interdigital transducer will launch a surface acoustic wave (SAW) that travels under the sensor's gas-sensitive resistive thin film. The SAW/resistive film interaction changes the SAW amplitude, phase and delay. For this work, three films, tin dioxide (SnO2), zinc oxide (ZnO) and palladium (Pd) [1, 2] will be studied. Gas detection will be shown when combining ZnO and Pd, and, observable change in SAW propagation loss is measured when methane gas is present at the film.
Show less - Date Issued
- 2015
- Identifier
- CFH0004832, ucf:45481
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004832
- Title
- MODELING, DESIGN AND FABRICATION OF ORTHOGONAL AND PSUEDO-ORTHOGONAL FREQUENCY CODED SAW WIRELESS SPREAD SPECTRUM RFID SENSOR TAGS.
- Creator
-
Saldanha, Nancy, Malcoha, Donald, University of Central Florida
- Abstract / Description
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Surface acoustic wave (SAW) sensors offer a wireless, passive sensor solution for use in numerous environments where wired sensing can be expensive and infeasible. Single carrier frequency SAW sensor embodiments such as delay lines, and resonators have been used in single sensor environments where sensor identification is not a necessity. The orthogonal frequency coded (OFC) SAW sensor tag embodiment developed at UCF uses a spread spectrum approach that allows interrogation in a multi-sensor...
Show moreSurface acoustic wave (SAW) sensors offer a wireless, passive sensor solution for use in numerous environments where wired sensing can be expensive and infeasible. Single carrier frequency SAW sensor embodiments such as delay lines, and resonators have been used in single sensor environments where sensor identification is not a necessity. The orthogonal frequency coded (OFC) SAW sensor tag embodiment developed at UCF uses a spread spectrum approach that allows interrogation in a multi-sensor environment and provides simultaneous sensing and sensor identification. The SAW device is encoded via proper design of multiple Bragg reflectors at differing frequencies. To enable accurate device design, a model to predict reflectivity over a wide range of electrode metallization ratios and metal thicknesses has been developed and implemented in a coupling of modes (COM) model. The high coupling coefficient, reflectivity and temperature coefficient of delay (TCD) of YZ LiNbO3 makes it an ideal substrate material for a temperature sensor, and the reflectivity model has been developed and verified for this substrate. A new concept of pseudo-orthogonal frequency coded (POFC) SAW sensor tags has been investigated, and with proper design, the POFC SAW reduces device insertion loss and fractional bandwidth compared to OFC. OFC and POFC sensor devices have been fabricated at 250 MHz and 915 MHz using fundamental operation, and 500 MHz and 1.6 GHz using second harmonic operation. Measured device results are shown and compared with the COM simulations using the enhanced reflectivity model. Additionally, the first OFC devices at 1.05 GHz were fabricated on 128o YX LiNbO3 to explore feasibility of the material for future use in OFC sensor applications. Devices at 915 MHz have been fabricated on YZ LiNbO3 and integrated with an antenna, and have then been used in a transceiver system built by Mnemonics, Inc. to wirelessly sense temperature. The first experimental wireless POFC SAW sensor device results and predictions will be presented.
Show less - Date Issued
- 2011
- Identifier
- CFE0003594, ucf:48888
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003594
- Title
- Multi-transit echo suppression for passive wireless surface acoustic wave sensors using 3rd harmonic unidirectional transducers and Walsh-Hadamard-like reflectors.
- Creator
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Rodriguez Cordoves, Luis, Malocha, Donald, Weeks, Arthur, Abdolvand, Reza, Moharam, Jim, Youngquist, Robert, University of Central Florida
- Abstract / Description
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A passive wireless surface acoustic wave sensor of a delay-line type is composed of an antenna, a transducer that converts the EM signal into a surface acoustic wave, and a set of acoustic reflectors that reflect the incoming signal back out through the antenna. A cavity forms between the transducer and the reflectors, trapping energy and causing multiple unwanted echoes. The work in this dissertation aims to reduce the unwanted echoes so that only the main transit signal is left(-)the signal...
Show moreA passive wireless surface acoustic wave sensor of a delay-line type is composed of an antenna, a transducer that converts the EM signal into a surface acoustic wave, and a set of acoustic reflectors that reflect the incoming signal back out through the antenna. A cavity forms between the transducer and the reflectors, trapping energy and causing multiple unwanted echoes. The work in this dissertation aims to reduce the unwanted echoes so that only the main transit signal is left(-)the signal of interest with sensor information.The contributions of this dissertation include reflective delay-line device response in the form of an infinite impulse response (IIR) filter. This may be used in the future to subtract out unwanted echoes via post-processing. However, this dissertation will use a physical approach to echo suppression by using a unidirectional transducer. Thus a unidirectional transducer is used and also optimized for 3rd harmonic operation. Both the directionality and the coupling of the 3rd harmonic optimized SPUDT are improved over a standard electrode width controlled (EWC) SPUDT. New type of reflectors for the reflective delay-line device are also presented. These use BPSK type coding, similar to that of the Walsh-Hadamard codes. Two types are presented, variable reflectivity and variable chip-lengths. The COM model is used to simulate devices and compare the predicted echo suppression level to that of fabricated devices. Finally, a device is mounted on a tunable antenna and the echo is suppressed on a wireless operating device.
Show less - Date Issued
- 2017
- Identifier
- CFE0006912, ucf:51697
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006912
- Title
- Ultra-wideband Spread Spectrum Communications using Software Defined Radio and Surface Acoustic Wave Correlators.
- Creator
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Gallagher, Daniel, Malocha, Donald, Delfyett, Peter, Richie, Samuel, Weeks, Arthur, Youngquist, Robert, University of Central Florida
- Abstract / Description
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Ultra-wideband (UWB) communication technology offers inherent advantages such as the ability to coexist with previously allocated Federal Communications Commission (FCC) frequencies, simple transceiver architecture, and high performance in noisy environments. Spread spectrum techniques offer additional improvements beyond the conventional pulse-based UWB communications. This dissertation implements a multiple-access UWB communication system using a surface acoustic wave (SAW) correlator...
Show moreUltra-wideband (UWB) communication technology offers inherent advantages such as the ability to coexist with previously allocated Federal Communications Commission (FCC) frequencies, simple transceiver architecture, and high performance in noisy environments. Spread spectrum techniques offer additional improvements beyond the conventional pulse-based UWB communications. This dissertation implements a multiple-access UWB communication system using a surface acoustic wave (SAW) correlator receiver with orthogonal frequency coding and software defined radio (SDR) base station transmitter.Orthogonal frequency coding (OFC) and pseudorandom noise (PN) coding provide a means for spreading of the UWB data. The use of orthogonal frequency coding (OFC) increases the correlator processing gain (PG) beyond that of code division multiple access (CDMA); providing added code diversity, improved pulse ambiguity, and superior performance in noisy environments. Use of SAW correlators reduces the complexity and power requirements of the receiver architecture by eliminating many of the components needed and reducing the signal processing and timing requirements necessary for digital matched filtering of the complex spreading signal.The OFC receiver correlator code sequence is hard-coded in the device due to the physical SAW implementation. The use of modern SDR forms a dynamic base station architecture which is able to programmatically generate a digitally modulated transmit signal. An embedded Xilinx Zynq (TM) system on chip (SoC) technology was used to implement the SDR system; taking advantage of recent advances in digital-to-analog converter (DAC) sampling rates. SDR waveform samples are generated in baseband in-phase and quadrature (I (&) Q) pairs and upconverted to a 491.52 MHz operational frequency.The development of the OFC SAW correlator ultimately used in the receiver is presented along with a variety of advanced SAW correlator device embodiments. Each SAW correlator device was fabricated on lithium niobate (LiNbO3) with fractional bandwidths in excess of 20%. The SAW correlator device presented for use in system was implemented with a center frequency of 491.52 MHz; matching SDR transmit frequency. Parasitic electromagnetic feedthrough becomes problematic in the packaged SAW correlator after packaging and fixturing due to the wide bandwidths and high operational frequency. The techniques for reduction of parasitic feedthrough are discussedwith before and after results showing approximately 10:1 improvement.Correlation and demodulation results are presented using the SAW correlator receiver under operation in an UWB communication system. Bipolar phase shift keying (BPSK) techniques demonstrate OFC modulation and demodulation for a test binary bit sequence. Matched OFC code reception is compared to a mismatched, or cross-correlated, sequence after correlation and demodulation. Finally, the signal-to-noise power ratio (SNR) performance results for the SAW correlator under corruption of a wideband noise source are presented.
Show less - Date Issued
- 2015
- Identifier
- CFE0005794, ucf:50054
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005794
