View All Items
(1 - 5 of 5)
- 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
- 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
- DESIGN OF A WIDEBAND DUAL-POLARIZED CAVITY BACKED SLOT ANTENNA.
- Creator
-
Paryani, Rajesh, Wahid, Parveen F, University of Central Florida
- Abstract / Description
-
A new technique for designing wideband dual-polarized cavity-backed slot antennas is presented. The structure is in the form of a double-resonant, dual-polarized slot antenna backed by a shallow substrate integrated cavity with a depth of approximately one tenth the free space wavelength. The presence of the cavity behind the slot enhances the antennaÂÂ's directivity and reduces the possibility of surface wave propagation in the antenna substrate when the element is...
Show moreA new technique for designing wideband dual-polarized cavity-backed slot antennas is presented. The structure is in the form of a double-resonant, dual-polarized slot antenna backed by a shallow substrate integrated cavity with a depth of approximately one tenth the free space wavelength. The presence of the cavity behind the slot enhances the antennaÂÂ's directivity and reduces the possibility of surface wave propagation in the antenna substrate when the element is used in an array environment. Moreover, the dual-polarized nature of this radiating element may be exploited to synthesize any desired polarization (vertical, horizontal, RHCP, or LHCP). The double-resonant behavior observed in this substrate-integrated cavity-backed slot antenna (SICBSA) is utilized to enhance its bandwidth compared to a typical cavity-backed slot antenna. A prototype of the proposed antenna is fabricated and tested. Measurement results indicate that a bandwidth of 19%, an average gain of 5.3 dB, and a wideband differential isolation of 30 dB can be achieved using this technique. The principles of operation along with the measurement results of the fabricated prototype are presented and discussed in this dissertation. The SICBSA is investigated as a candidate for use as an array element. A uniform two element phased array is demonstrated to locate the main beam from boresight to thirty degrees. The potential effects of mutual coupling and surface wave propagation are considered and analyzed.
Show less - Date Issued
- 2010
- Identifier
- CFE0003066, ucf:48295
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003066
- Title
- Customizable Antenna Array Using Reconfigurable Antenna Elements.
- Creator
-
Shirazi, Mahmoud, Gong, Xun, Wahid, Parveen, Jones, W Linwood, Abdolvand, Reza, Kuebler, Stephen, University of Central Florida
- Abstract / Description
-
A shared-aperture reconfigurable slot-ring antenna array switching between different frequency bands and polarizations is presented for phased array applications. PIN diode switches are incorporated into the slots of the antenna to change the state of the reconfigurable slot-ring antenna array. Each frequency band has its own feeding lines which allows for the use of high-performance narrow-band transmit/receive (T/R) modules instead of ultra wideband (UWB) T/R modules. Furthermore, the...
Show moreA shared-aperture reconfigurable slot-ring antenna array switching between different frequency bands and polarizations is presented for phased array applications. PIN diode switches are incorporated into the slots of the antenna to change the state of the reconfigurable slot-ring antenna array. Each frequency band has its own feeding lines which allows for the use of high-performance narrow-band transmit/receive (T/R) modules instead of ultra wideband (UWB) T/R modules. Furthermore, the spacing between the elements in each frequency band is less than half free-space wavelength (?0) over the frequency band of operation which enables grating-lobe-free beam scanning. This is the first shared-aperture reconfigurable dual-polarized antenna with separate feeding for each band which is scalable to a larger array with element spacing of less than 0.5?0 in all frequency bands of operation.First, a switchable-band reconfigurable antenna array switching between L and C bands is presented. This antenna operates at 1.76/5.71 GHz with a fractional bandwidth (FBW) of 8.6%/11.5%, realized gain of 0.1/4.2 dBi and radiation efficiency of 66.6%/80.7% in the L-/C- band operating states, respectively. Second, a wideband version of the reconfigurable antenna element using fractal geometries is presented. This dual-polarized antenna element is switching between S and C bands with wide bandwidth in each operating state. In the S-/C-band operating state, this antenna shows 69.1%/58.3% FBW with a maximum realized gain of 2.4/3.1 dBi. Third, the wideband antenna element is extended to an antenna array. The reconfigurable dual-polarized antenna array with vertical coaxial feeding switches between S- and C-band states with full-band coverage. A 2(&)#215;2 S-band antenna array can be reconfigured to a 4(&)#215;4 C-band antenna array by activating/deactivating PIN diode switches. This antenna array shows 64.3%/66.7% FBW with 8.4/14.3 dBi maximum realized gain in the S-/C-band operating states, respectively. Finally, a reconfigurable antenna element covering three adjacent frequency bands is presented. The FBW of this tri-band antenna element is 75%/63%/26% in the S/C/X band state.
Show less - Date Issued
- 2018
- Identifier
- CFE0007373, ucf:52092
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007373
- Title
- Ultra-wideband Spread Spectrum Communications using Software Defined Radio and Surface Acoustic Wave Correlators.
- Creator
-
Gallagher, Daniel, Malocha, Donald, Delfyett, Peter, Richie, Samuel, Weeks, Arthur, Youngquist, Robert, University of Central Florida
- Abstract / Description
-
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
