IEEE Antennas and Propagation Society International Symposium. 2001 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.01CH37229)
IEEE Antennas and Propagation Society International Symposium. Digest. Held in conjunction with: USNC/CNC/URSI North American Radio Sci. Meeting (Cat. No.03CH37450)
Generating a plane wave in the near field is important for antenna measurements in confined space... more Generating a plane wave in the near field is important for antenna measurements in confined spaces, This paper shows how to create an approximate plane wave in the near field from a planar array of isotropic point sources using two approaches, a least square fit and a genetic algorithm, to find the complex amplitude weights.
The genetic algorithm has proven useful in the design of conventional, static beamforming network... more The genetic algorithm has proven useful in the design of conventional, static beamforming networks. It is also quite useful as an adaptive algorithm for smart antennas. This paper demonstrates two uses of the genetic algorithm to adaptively control antenna characteristics. The first is a phaseonly implementation in which nulls are adaptively placed using the least significant bits of the phase shifters. The second application adaptively controls the currents on crossed dipoles to improve the link budget in a satellite communications system. In both cases, the genetic algorithm quickly improves the antenna performance.
Utah State University is building a nanosatellite that will cooperate with satellites built by th... more Utah State University is building a nanosatellite that will cooperate with satellites built by the University of Washington and Virginia Tech to perform important ionospheric investigations, as well as test various aspects of formation flying around the earth. These satellites must be able to communicate with each other as well as communicate with the ground stations. This paper describes the nanosatellite program at Utah State University (USUsat). In addition, the communication link budget and antenna designs for this satellite are described in detail. The ground station will have an array of helical antennas, while the antennas on the satellites will be circularly polarized microstrip patches.
This paper presents some types of adaptive antennas and the historical development of adaptive an... more This paper presents some types of adaptive antennas and the historical development of adaptive antennas. It explains some of the common algorithms associated with digital beamforming then presents techniques for adaptation using conventional arrays with corporate feeds, including the use of reconfigurable antenna elements.
Reflector antennas confine most of the electromagnetic energy captured over their apertures into ... more Reflector antennas confine most of the electromagnetic energy captured over their apertures into a focal plane or redirect the radiated field of the feed into far field. This paper presents a concise history of reflector antenna developments over an extended time span. Representative examples are provided for different periods that impacted various developments of reflector antennas covering past, present, and future. Due to page limitations, not all worldwide aspects of reflector antenna developments are touched upon in this paper, and the authors have confined themselves to the areas that have influenced their research activities.
This paper shows how certain photoconductive materials can be used to design an adaptive array el... more This paper shows how certain photoconductive materials can be used to design an adaptive array element with a center frequency of 2 GHz. The resonant frequency of the patch gradually shifts to a lower frequency as the conductivity off its gap filled with photonic material increases. The resulting increase in the reflection coefficient at the center frequency and decrease in gain acts as a continuous amplitude weight. This approach offers continuous variation of the conductive portions of the patch rather than an "on" or "off' approach offered by the switches. Varying the amplitude of the elements allows dynamic control over the array sidelobe levels.
2015 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP), 2015
Near-field focusing characteristics of transmitarray antennas are investigated. The design proced... more Near-field focusing characteristics of transmitarray antennas are investigated. The design procedure is summarized and a Ku-band focused transmitarray antenna is presented where the elements are aperture-coupled patches interconnected with stripline delays. The focusing performance of the transmitarray is compared with classic far-field designs. It is shown that a near-field focused reflectarray can be a good candidate for applications requiring high microwave power.
International Symposium on Antennas and Propagation, Jul 3, 2011
Time-modulated arrays open and close switches in order to connect and disconnect elements from th... more Time-modulated arrays open and close switches in order to connect and disconnect elements from the feed network and generate an "average" low sidelobe array. This paper presents an analysis of the instantaneous array factor, and its effect on received signals in order to demonstrate how timemodulation causes significant fluctuations in the directivity and does not reject sidelobe interference as well as standard static low sidelobe approaches.
This paper describes a method for placing nulls in a reflector antenna pattern by incorporating e... more This paper describes a method for placing nulls in a reflector antenna pattern by incorporating elements which have a reflectivity that can be varied over a wide range using electrical or optical control.
Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation, 2012
An 8 beam planar phased array can transmit 8 signals in 8 different directions. The array is assu... more An 8 beam planar phased array can transmit 8 signals in 8 different directions. The array is assumed to have 8 corporate feeds. The signal transmitted by a beam consists of the desired signal that is coherently combined from all the elements plus small amounts from the other 7 signals. These other signals distort the desired signal. This paper shows examples of these distortions. I.
This paper presents a review of recent developments in the design of planar microwave lenses capa... more This paper presents a review of recent developments in the design of planar microwave lenses capable of operating over broad bandwidths in a true-time-delay fashion. The lenses discussed in this paper consist of planar apertures populated with miniature, sub-wavelength time-delay units. Each time delay unit is the unit cell of an appropriately-designed Frequency Selective Surface (FSS) with non-resonant, sub-wavelength constituting unit cells and is designed to provide a constant time-delay unit over the frequency range at which the lens operates. Designs that exploit both band-pass and low-pass FSSs are presented and discussed. Because of the non-resonant nature of their constituting unit cells and their small dimensions, such lenses can operate over broad bandwidths with wide fields of views. When used in conjunction with appropriately designed feed antennas, these lenses can be used in multi-beam, high-gain, broadband antenna apertures.
This paper describes the design, construction, and testing of an 8 element broadband array with p... more This paper describes the design, construction, and testing of an 8 element broadband array with photoconductive attenuators at each broadband monopole element. The photoconductive attenuators are controlled by an IR LED and vary between on and off with a small reflection coefficient and small insertion loss. Test results for the elements and array are presented. Low sidelobe Chebyshev amplitude tapers are demonstrated by controlling the illumination of the photoconductive weights.
2014 IEEE Conference on Antenna Measurements & Applications (CAMA), 2014
The fundamentals of ultra-wideband (UWB) focused phased array antennas are reviewed, and some bas... more The fundamentals of ultra-wideband (UWB) focused phased array antennas are reviewed, and some basic limitations are outlined. It is shown that when phase shifters are used within the architecture of the array, the focal point moves as a function of frequency, which degrades the focusing performance of the antenna. To mitigate these limitations, time-delay units are proposed, and it is revealed that perfect focusing across a wide bandwidth can be achieved by this approach. To validate this concept, an UWB Vivaldi focused antenna array using time delays is designed which demonstrates good focusing capability across the UWB spectrum.
Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation, 2012
Phase shift commands to steer a phased array beam are sent to the phase shifters sequentially. In... more Phase shift commands to steer a phased array beam are sent to the phase shifters sequentially. In a radar system, the phase shifters simultaneously change when they receive a strobe signal. In a communications phased array, the phase shifters can either change simultaneously or sequentially as they receive the commands. The sequential approach causes the beam to gradually move from one position to another. This paper shows this behavior and effects the element sequence. I.
An adaptive antenna places nulls in its antenna pattern in the direction of the interfering sourc... more An adaptive antenna places nulls in its antenna pattern in the direction of the interfering sources. shifters. Adaptive antennas are a subset of smart antennas, and have received considerable interest in the recent wireless revolution. This paper presents a successful application of a genetic algorithm with an experimental antenna for placing a null in the direction of an interference source. every element in addition to beam steering phase Cause the main beam to move from its desired Significantly raise the sidelobe levels of a low pointing direction. sidelobe array. The experiment took place at the Air Force Research Laboratory (AEXL)/Sensors Directorate, Hanscom AFB, MA. Results show that a null can be placed down to the noise floor of the measurement system within 20 to 50 power measurements. Thus, the approach to adaptive nulling is a viable means of quickly placing a null in the sidelobes of a phased array antenna.
IEEE Antennas and Propagation Society International Symposium. 2001 Digest. Held in conjunction with: USNC/URSI National Radio Science Meeting (Cat. No.01CH37229)
IEEE Antennas and Propagation Society International Symposium. Digest. Held in conjunction with: USNC/CNC/URSI North American Radio Sci. Meeting (Cat. No.03CH37450)
Generating a plane wave in the near field is important for antenna measurements in confined space... more Generating a plane wave in the near field is important for antenna measurements in confined spaces, This paper shows how to create an approximate plane wave in the near field from a planar array of isotropic point sources using two approaches, a least square fit and a genetic algorithm, to find the complex amplitude weights.
The genetic algorithm has proven useful in the design of conventional, static beamforming network... more The genetic algorithm has proven useful in the design of conventional, static beamforming networks. It is also quite useful as an adaptive algorithm for smart antennas. This paper demonstrates two uses of the genetic algorithm to adaptively control antenna characteristics. The first is a phaseonly implementation in which nulls are adaptively placed using the least significant bits of the phase shifters. The second application adaptively controls the currents on crossed dipoles to improve the link budget in a satellite communications system. In both cases, the genetic algorithm quickly improves the antenna performance.
Utah State University is building a nanosatellite that will cooperate with satellites built by th... more Utah State University is building a nanosatellite that will cooperate with satellites built by the University of Washington and Virginia Tech to perform important ionospheric investigations, as well as test various aspects of formation flying around the earth. These satellites must be able to communicate with each other as well as communicate with the ground stations. This paper describes the nanosatellite program at Utah State University (USUsat). In addition, the communication link budget and antenna designs for this satellite are described in detail. The ground station will have an array of helical antennas, while the antennas on the satellites will be circularly polarized microstrip patches.
This paper presents some types of adaptive antennas and the historical development of adaptive an... more This paper presents some types of adaptive antennas and the historical development of adaptive antennas. It explains some of the common algorithms associated with digital beamforming then presents techniques for adaptation using conventional arrays with corporate feeds, including the use of reconfigurable antenna elements.
Reflector antennas confine most of the electromagnetic energy captured over their apertures into ... more Reflector antennas confine most of the electromagnetic energy captured over their apertures into a focal plane or redirect the radiated field of the feed into far field. This paper presents a concise history of reflector antenna developments over an extended time span. Representative examples are provided for different periods that impacted various developments of reflector antennas covering past, present, and future. Due to page limitations, not all worldwide aspects of reflector antenna developments are touched upon in this paper, and the authors have confined themselves to the areas that have influenced their research activities.
This paper shows how certain photoconductive materials can be used to design an adaptive array el... more This paper shows how certain photoconductive materials can be used to design an adaptive array element with a center frequency of 2 GHz. The resonant frequency of the patch gradually shifts to a lower frequency as the conductivity off its gap filled with photonic material increases. The resulting increase in the reflection coefficient at the center frequency and decrease in gain acts as a continuous amplitude weight. This approach offers continuous variation of the conductive portions of the patch rather than an "on" or "off' approach offered by the switches. Varying the amplitude of the elements allows dynamic control over the array sidelobe levels.
2015 IEEE MTT-S International Microwave Workshop Series on Advanced Materials and Processes for RF and THz Applications (IMWS-AMP), 2015
Near-field focusing characteristics of transmitarray antennas are investigated. The design proced... more Near-field focusing characteristics of transmitarray antennas are investigated. The design procedure is summarized and a Ku-band focused transmitarray antenna is presented where the elements are aperture-coupled patches interconnected with stripline delays. The focusing performance of the transmitarray is compared with classic far-field designs. It is shown that a near-field focused reflectarray can be a good candidate for applications requiring high microwave power.
International Symposium on Antennas and Propagation, Jul 3, 2011
Time-modulated arrays open and close switches in order to connect and disconnect elements from th... more Time-modulated arrays open and close switches in order to connect and disconnect elements from the feed network and generate an "average" low sidelobe array. This paper presents an analysis of the instantaneous array factor, and its effect on received signals in order to demonstrate how timemodulation causes significant fluctuations in the directivity and does not reject sidelobe interference as well as standard static low sidelobe approaches.
This paper describes a method for placing nulls in a reflector antenna pattern by incorporating e... more This paper describes a method for placing nulls in a reflector antenna pattern by incorporating elements which have a reflectivity that can be varied over a wide range using electrical or optical control.
Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation, 2012
An 8 beam planar phased array can transmit 8 signals in 8 different directions. The array is assu... more An 8 beam planar phased array can transmit 8 signals in 8 different directions. The array is assumed to have 8 corporate feeds. The signal transmitted by a beam consists of the desired signal that is coherently combined from all the elements plus small amounts from the other 7 signals. These other signals distort the desired signal. This paper shows examples of these distortions. I.
This paper presents a review of recent developments in the design of planar microwave lenses capa... more This paper presents a review of recent developments in the design of planar microwave lenses capable of operating over broad bandwidths in a true-time-delay fashion. The lenses discussed in this paper consist of planar apertures populated with miniature, sub-wavelength time-delay units. Each time delay unit is the unit cell of an appropriately-designed Frequency Selective Surface (FSS) with non-resonant, sub-wavelength constituting unit cells and is designed to provide a constant time-delay unit over the frequency range at which the lens operates. Designs that exploit both band-pass and low-pass FSSs are presented and discussed. Because of the non-resonant nature of their constituting unit cells and their small dimensions, such lenses can operate over broad bandwidths with wide fields of views. When used in conjunction with appropriately designed feed antennas, these lenses can be used in multi-beam, high-gain, broadband antenna apertures.
This paper describes the design, construction, and testing of an 8 element broadband array with p... more This paper describes the design, construction, and testing of an 8 element broadband array with photoconductive attenuators at each broadband monopole element. The photoconductive attenuators are controlled by an IR LED and vary between on and off with a small reflection coefficient and small insertion loss. Test results for the elements and array are presented. Low sidelobe Chebyshev amplitude tapers are demonstrated by controlling the illumination of the photoconductive weights.
2014 IEEE Conference on Antenna Measurements & Applications (CAMA), 2014
The fundamentals of ultra-wideband (UWB) focused phased array antennas are reviewed, and some bas... more The fundamentals of ultra-wideband (UWB) focused phased array antennas are reviewed, and some basic limitations are outlined. It is shown that when phase shifters are used within the architecture of the array, the focal point moves as a function of frequency, which degrades the focusing performance of the antenna. To mitigate these limitations, time-delay units are proposed, and it is revealed that perfect focusing across a wide bandwidth can be achieved by this approach. To validate this concept, an UWB Vivaldi focused antenna array using time delays is designed which demonstrates good focusing capability across the UWB spectrum.
Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation, 2012
Phase shift commands to steer a phased array beam are sent to the phase shifters sequentially. In... more Phase shift commands to steer a phased array beam are sent to the phase shifters sequentially. In a radar system, the phase shifters simultaneously change when they receive a strobe signal. In a communications phased array, the phase shifters can either change simultaneously or sequentially as they receive the commands. The sequential approach causes the beam to gradually move from one position to another. This paper shows this behavior and effects the element sequence. I.
An adaptive antenna places nulls in its antenna pattern in the direction of the interfering sourc... more An adaptive antenna places nulls in its antenna pattern in the direction of the interfering sources. shifters. Adaptive antennas are a subset of smart antennas, and have received considerable interest in the recent wireless revolution. This paper presents a successful application of a genetic algorithm with an experimental antenna for placing a null in the direction of an interference source. every element in addition to beam steering phase Cause the main beam to move from its desired Significantly raise the sidelobe levels of a low pointing direction. sidelobe array. The experiment took place at the Air Force Research Laboratory (AEXL)/Sensors Directorate, Hanscom AFB, MA. Results show that a null can be placed down to the noise floor of the measurement system within 20 to 50 power measurements. Thus, the approach to adaptive nulling is a viable means of quickly placing a null in the sidelobes of a phased array antenna.
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Papers by Randy Haupt