With usable spectrum becoming increasingly more congested, the need for robust, adaptive communications to take advantage of spatially-separated signal sources is apparent. Traditional phased array beamforming techniques used for interference removal rely on perfect calibration between elements and precise knowledge of the array configuration; however, if the exact array configuration is not known (unknown or imperfect assumption of element locations, unknown mutual coupling between elements, etc.), these traditional beamforming techniques are not viable, so a blind beamforming approach is required. A novel blind beamforming approach is proposed to address complex narrow-band interference environments where the precise array configuration is unknown. The received signal is decomposed into orthogonal narrow-band partitions using a polyphase filter-bank channelizer, and a rank-reduced version of the received matrix on each sub-channel is computed through reconstruction by retaining a subset of its singular values. The wideband spectrum is synthesized through a near-perfect polyphase reconstruction filter, and a composite wideband spectrum is obtained from the maximum eigenvector of the resulting covariance matrix.The resulting process is shown to suppress numerous interference sources (in special cases even with more than the degrees of freedom of the array), all without any knowledge of the primary signal of interest. Results are validated with both simulation and wireless laboratory over-the-air experimentation. / M.S. / As the number of devices using wireless communications increase, the amount of usable radio frequency spectrum becomes increasingly congested. As a result, the need for robust, adaptive communications to improve spectral efficiency and ensure reliable communication in the presence of interference is apparent. One solution is using beamforming techniques on digital phased array receivers to maximize the energy in a desired direction and steer nulls to remove interference. However, traditional phased array beamforming techniques used for interference removal rely on perfect calibration between antenna elements and precise knowledge of the array configuration. Consequently, if the exact array configuration is not known (unknown or imperfect assumption of element locations, unknown mutual coupling between elements, etc.), these traditional beamforming techniques are not viable, so a beamforming approach with relaxed requirements (blind beamforming) is required. This thesis proposes a novel blind beamforming approach to address complex narrow-band interference in spectrally congested environments where the precise array configuration is unknown. The resulting process is shown to suppress numerous interference sources, all without any knowledge of the primary signal of interest. Results are validated with both simulation and wireless laboratory experimentation conducted with a two-element array, verifying that proposed beamforming approach achieves a similar performance to the theoretical performance bound of receiving packets in AWGN with no interference present.

Use of Slotted Waveguide Antenna Stiffened Structures (SWASS) in future commercial and military aircraft calls for the development of an airworthiness certification procedure. The first step of this procedure is to provide a computationally low-cost method for modeling waveguide antenna arrays on the scale of an aircraft skin panel using a multi-fidelity model. Weather detection radar for the Northrop Grumman X-47 unmanned air system is considered as a case study. COMSOL Multiphysics is used for creating high-fidelity waveguide models that are imported into the MATLAB Phased Array Toolbox for large-scale array calculations using a superposition method. Verification test cases show that this method is viable for relatively accurate modeling of large SWASS arrays with low computational effort. Additionally, realistic material properties for carbon fiber reinforced plastic (CFRP) are used to create a more accurate model. Optimization is performed on a 12-slot CFRP waveguide to determine the waveguide dimensions for the maximum far-field gain and separately for the maximum critical buckling load. Using the two separate optima as utopia points, a multi-objective optimization for the peak far-field gain and critical buckling load is performed, to obtain a balance between EM performance and structural strength. This optimized waveguide is then used to create a SWASS array of approximately the same size as an aircraft wing panel using the multi-fidelity modeling method that is proposed. This model is compared to a typical conventional weather radar system, and found to be well above the minimum mission requirements. / Master of Science / Antennas used in military and commercial aircraft have traditionally been designed independently from the aircraft structure. Increasingly, e↵ort has been made to integrate these processes, in order to create more efficient, dual-purpose structures. Slotted waveguide antennas, hollow rectangular tubes with slots cut in one face, are commonly used to create arrays for aircraft on-board weather radar. A type of structurally embedded antenna, slotted waveguide antenna stiffened structures (SWASS), consists of slotted waveguides that are sandwiched between two layers of a composite material. This sandwich structure can be used in place of the conventional structure used for aircraft skin, allowing the slotted waveguides to function not only as antennas, but also as part of the aircraft’s load-bearing structure. Because of the geometric complexity of the slotted waveguides, generating accurate models of the antenna performance can be difficult and requires a great deal of computational power. This thesis presents and validates a method for reducing the complexity of modeling the antenna performance of SWASS arrays. Additionally, optimizations are performed to improve both the waveguide’s performance as an antenna and as a load-bearing part of the aircraft structure. Finally, the optimized SWASS array is compared to the actual mission requirements of the Northrop Grumman X-47 unmanned aircraft, and is found to perform above the required levels.

An active, broadband antenna module amenable for use in low cost phased arrays is proposed. The module consists of a Vivaldi antenna integrated with a frequency conversion integrated circuit. A method of orthogonally mounting endfire antennas onto an array motherboard is developed using castellated vias. A castellated active isolated Vivaldi antenna package is designed, fabricated, and measured. An 8x1 phased array of castellated, active Vivaldi antenna packages is designed and assembled. Each element has approximately one octave of bandwidth centered in X-band, and each is mounted onto a coplanar waveguide motherboard. Radiation patterns of the array are measured at several frequencies and scan angles.

New mobile communication generations need electromagnetic sensors capable of steering their high-directive beams towards the users. Conventional base stations use square lattice phased arrays to accomplish this task. These arrays are composed of a large number of radiating elements to achieve the required high directivity and scanning capabilities. These systems are of high complexity and cost because after each element there is a large electronic chain. Therefore, it is of high interest to reduce the element count in the aperture of the array while maintaining its performance. Instead of using a square lattice to place the radiating elements, a triangular lattice can be used. It is proven that a triangular lattice optimally samples the aperture and reduces the element count by up to a 15.5%, hence reducing the cost and complexity of the complete antenna system. However, dual-polarized Vivaldi elements do not conform naturally to this kind of lattice and, consequently, they have not been thoroughly studied in the literature despite this well-known advantage. In this work, a novel dual-polarized fully-metallic Vivaldi element is presented. Also, the feeding network for this element is designed in the form of a suspended stripline. This technology presents low loss in comparison with a conventional stripline or microstrip. The radiating elements can be manufactured in a single piece, and they are easily integrated with the stripline feeding by just placing one on top of the other. An infinite array analysis, i.e. unit cell analysis, was performed to show the correct performance of the triangular lattice array and the proposed dual-polarized Vivaldi antenna design. A good matching was achieved over the entire band from 6 to 15 GHz for all the scanning planes and up to 60◦ scanning angle. The active element patterns show the good behaviour of the array, i.e. the absence of scan blindness and grating lobes. Finally, the unit cell analysis is compared to a finite 11×11 array for verification. / Nya generationer av mobilkommunikation behöver elektromagnetiska sensorer som kan styra sin högriktade signalenergi mot användarna. Konventionella basstationer använder kvadratiska gitterfasuppsättningar. Dessa arrayer är sammansatta av ett stort antal strålningselement för att uppnå den erforderliga höga riktningsförmågan och avsökningskapaciteten. Dessa system är av hög komplexitet och kostnad eftersom det efter varje element finns en lång elektronisk kedja. Därför är det av stort intresse att minska antalet element i arrayens apertur samtidigt som dess prestanda bibehålls. Istället för att använda ett kvadratiskt gitter för att placera de strålande elementen, kan ett triangulärt gitter användas. Det är bevisat att ett triangulärt gitter optimalt samplar aperturen och minskar elementantalet med upp till 15.5%, vilket minskar kostnaden och komplexiteten för hela antennsystemet. Dubbelpolariserade Vivaldi-element överensstämmer dock inte naturligt med denna typ av triangulära symmetri och följaktligen har de inte studerats grundligt i litteraturen trots denna välkända fördel. I detta arbete presenteras ett nytt dubbelpolariserat fullt metalliskt Vivaldi-element. Matningsnätverket för detta element är också utformat i form av en upphängd stripline. Denna metod ger låga förluster i jämförelse med en konventionell stripline eller mikrostrip. En oändlig array-analys, d.v.s. enhetscell, utfördes för att visa den korrekta prestandan för den triangulära gittermatrisen. En bra matchning uppnåddes över hela bandet från 6 till 15 GHz för alla skanningsplan och upp till 60° utstyrningsvinkel. Aktiva elementstrålnings diagrammet visar konfigurationens lovande egenskaper, d.v.s. ingen skanningsblindhet eller gallerlober. Slutligen jämförs enhetscellanalysen med en ändlig 11x11 array för verifiering.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Employment of the retro-directive technique described in Reference 1 describes a totally Autonomous Ground Station providing hemispheric coverage and continuous tracking. This System establishes communications between the satellite and ground station without human intervention or moving parts. When a satellite is in view, the ground station beacon antenna, using CDMA, enables the desired satellite transmitter and directs its beam to the ground station. The ground station, using the satellite’s transmitted signal, directs it’s receive and transmit arrays to point the ground station beams to the satellite, establishing two-way communications. The process is automatic and provides continuous horizon to horizon tracking.

This dissertation introduces new technologies and techniques for low-cost phased arrays and scanning antennas. Special emphasis is placed on new approaches for low-cost millimeter-wave beam control. Several topics are covered. A novel reconfigurable grating antenna is presented for low-cost millimeter-wave beam steering. The versatility of the approach is proven by adapting the design to dual-beam and circular-polarized operation. In addition, a simple and accurate procedure is developed for analyzing these antennas. Designs are presented for low-cost microwave/millimeter-wave phased-array transceivers with extremely broad bandwidth. The target applications for these systems are mobile satellite communications and ultra-wideband radar. Monolithic PIN diodes are a useful technology, especially suited for building miniaturized control components in microwave and millimeter-wave phased arrays. This dissertation demonstrates a new strategy for extracting bias-dependent small-signal models for monolithic PIN diodes. The space solar-power satellite (SPS) is a visionary plan that involves beaming electrical power from outer space to the earth using a high-power microwave beam. Such a system must have retrodirective control so that the high-power beam always points on target. This dissertation presents a new phased-array architecture for the SPS system that could considerably reduce its overall cost and complexity. In short, this dissertation presents technologies and techniques that reduce the cost of beam steering at microwave and millimeter-wave frequencies. The results of this work should have a far-ranging impact on the future of wireless systems.

This thesis presents a novel monolithic phased array implemented using the RF MEMS technology. The structure, which is designed at 15 GHz, consists of four linearly placed microstrip patch antennas, 3-bit distributed RF MEMS low-loss phase shifters, and a corporate feed network. The RF MEMS phase shifter employed in the system consists of three sections with a total of 28 unit cells, and it occupies an area of 22.4 mm &amp / #61620 / 2.1 mm. The performance of the phase shifters is improved using high-Q metal-air-metal capacitors in addition to MEMS switches as loading elements on a high-impedance coplanar waveguide transmission line. The phased array is fabricated monolithically using an in-house surface micromachining process, where a 1.2-&amp / #61549 / m thick gold structural layer is placed on a 500-&micro / m thick glass substrate with a capacitive gap of 2 &amp / #61549 / m. The fabrication process is simple, requires only 6 masks, and allows the implementation of various RF MEMS components on the same substrate, such as RF MEMS switches and phase shifters. The fabricated monolithic phased array occupies an area of only 6 cm &amp / #61620 / 5 cm. The measurement results show that the phase shifter can provide nearly 20&amp / #61616 / /50&amp / #61616 / /95&amp / #61616 / phase shifts and their eight combinations at the expense of 1.5 dB average insertion loss at 15 GHz. The phase shifters can be actuated with 16 V, while dissipating negligible power due to its capacitive operation. It is also shown by measurements that the main beam can be steered to 4&amp / #61616 / and 14&amp / #61616 / by suitable settings of the RF MEMS phase shifters.

This dissertation introduces new technologies and techniques for low-cost phased arrays and scanning antennas. Special emphasis is placed on new approaches for low-cost millimeter-wave beam control. Several topics are covered. A novel reconfigurable grating antenna is presented for low-cost millimeter-wave beam steering. The versatility of the approach is proven by adapting the design to dual-beam and circular-polarized operation. In addition, a simple and accurate procedure is developed for analyzing these antennas. Designs are presented for low-cost microwave/millimeter-wave phased-array transceivers with extremely broad bandwidth. The target applications for these systems are mobile satellite communications and ultra-wideband radar. Monolithic PIN diodes are a useful technology, especially suited for building miniaturized control components in microwave and millimeter-wave phased arrays. This dissertation demonstrates a new strategy for extracting bias-dependent small-signal models for monolithic PIN diodes. The space solar-power satellite (SPS) is a visionary plan that involves beaming electrical power from outer space to the earth using a high-power microwave beam. Such a system must have retrodirective control so that the high-power beam always points on target. This dissertation presents a new phased-array architecture for the SPS system that could considerably reduce its overall cost and complexity. In short, this dissertation presents technologies and techniques that reduce the cost of beam steering at microwave and millimeter-wave frequencies. The results of this work should have a far-ranging impact on the future of wireless systems.

The continual increase of wireless technologies in the world has motivated the use of phased arrays to mitigate radio frequency interference (RFI). There are many methods of performing beamforming for RFI rejection, but they are traditionally physically large and complicated solutions. Phased arrays need to be shrunk and made cheaper for them to see widespread use. This work presents several compact phased array receivers for different applications. The first part of this thesis presents a software GPS processor for a digital beamforming GPS receiver. The receiver is small enough to be flown on drones and enables GPS signals to be processed and a user’s position to be determined. Using digital beamforming, it can operate even under poor conditions such as intentional jamming, RFI, and large multipath effects. Next, this work builds a frontend RF chain for a true time delay phased array receiver. The receiver uses analog true delay delay chips to mitigate radio frequency interference in sensitive instruments. True time delay allows for analog beamforming over a wide bandwidth, but compact true time delay solutions are new and untested. The receiver allows these solutions to be properly vetted in a full system. The chain uses novel compact wideband antennas for L-band frequencies and traditional low cost amplifiers and filters. The last section of this thesis updates the open-source CASPER project to fully support RF system-on-chips. CASPER is an open-source framework for radio astronomy instruments. It speeds up the design and implementation of radio astronomy instruments on compact platforms and makes them easier to interact with. This work expands the framework to use the transmit abilities of advanced RF system-on-chip platforms. With this expansion, full duplex systems such as communications and radar can now also use CASPER. A full loopback beamforming test built on CASPER demonstrates both transmit and receive beamforming.

During this project we have designed a new type of antenna that uses an array of antenna elements in order to emit electromagnetic radiation as signals and to be able to control the beam. After an extended time the design yielded a simulation which had the correct characteristics. After printing and constructing a prototype of the antenna it was tested in an anechoic chamber at Uppsala University. The array was divided into two different sub-arrays: the upper and the lower sub-arrays. Each of these consisted in itself of two sides: the long and the short sides. Each side had seven radiating elements, during the tests only one of the two sub-arrays (upper or lower) was running. Both sub-arrays are excited via a rat-race or 90 degree coupler. While the antenna was running it had 14 radiating elements and two phase shifters, two per sub-array and two per side. The idea was for a signal to travel passing the radiating elements and the phase shifter which would steer the induced electromagnetic signal in one direction, a traveling-wave array. This direction could be changed since the phase shifters were configurable in three different states per phase shifter, hence the induced electromagnetic beam was steerable. The beam was also steerable through the feed which was re-configurable, since there were two feeds per sub-array a phase shift could be introduced between the long and the short side. The beam steering range was between -2 degrees and 11 degrees oriented as 0 degrees would be a perpendicular line from the array to the receiving end. The design itself worked which could be stated from the results in the upper part of the array, the test results from the lower part however did not match the simulated results. This is likely due to an error in the construction of the antenna rather than the theory since the upper and lower part of the array was mirrored versions of each other. The phase shifters worked as intended in the bigger picture but were slightly different in the simulations compared to the physical ones, likely due to the same type of error source as regarding the full antenna.