Presentation on theme: "DESIGNING OF A SMALL WEARABLE CONFORMAL PHASED ARRAY ANTENNA FOR WIRELESS COMMUNICATIONS By Sayan Roy Major Advisor: Dr. Benjamin D. Braaten Dept. of ECE,"— Presentation transcript:
1DESIGNING OF A SMALL WEARABLE CONFORMAL PHASED ARRAY ANTENNA FOR WIRELESS COMMUNICATIONS BySayan RoyMajor Advisor: Dr. Benjamin D. Braaten Dept. of ECE, NDSU, Fargo, ND, USA
2Contents Introduction Defining the Problem Phased Array Antenna Realization of Conformal Phased Array AntennaDesigning of Phased Array Antenna Test PlatformScanning Properties of Phased Array Antenna Test PlatformFour Element SELFLEX Array DesignScanning Properties of SELFLEX ArrayConclusion
3Introduction to Array Antenna Conformal Antenna Phased Array Antenna
4AntennaFor any communication device, an antenna system serves the purpose for external communication wirelessly.
6Array Antenna Array means a collection of similar entities. Set of individual antenna elements connected together to behave as a single unitAdvantagesHigher GainBeam Steering CapabilityReliableHigher SNR
7Beam steered 45° from Broadside direction Beam SteeringIn any Antenna system, the transmitting or receiving signal has two attributes:Amplitude (A) andPhase (φ).Beam Steering can be achieved in an array antenna by changing the progressive phase differences between antenna elements.Beam steered 45° from Broadside direction
9ConformalityConformality can be described as a map projection which has the property of preserving relative angles over small scales.In Mathematics, a conformal map is a function which preserves angles.
10Conformal AntennasOften mechanical design of a communication system requires that the associated antenna should be mounted on a curved surface.ApplicationsAerospace DesignsWearable AntennaSpacesuitMobile DevicesFor last couple of years, designers have been showing interest in simulating conformal antenna performance to optimize antenna parameters in presence of conformal surface.
12Relation between Conformality and Beam Steering A conformal surface changes its curvature with time and may be planar or non-planar.When an antenna system lies on a planar conformal surface, the field pattern of the antenna behaves normally.
13Relation between Conformality and Beam Steering (cont.) However, when the surface of the antenna becomes non-planar, the performance of the antenna starts to degrade.
14Relation between Conformality and Beam Steering (cont.) Beam Steering concept can be implemented to recover the field pattern of the antenna system by proper correction in relative phases between elements of the array.This type of antenna is known as Phased Array Antenna.
15Defining the Problem: Can we recover the radiation pattern of a conformal array ?
16Phased Array Antenna. Defining Co-ordinate. Theory of Array Factor Phased Array Antenna Defining Co-ordinate Theory of Array Factor Concept of Phase Scanning Phase Compensation Technique of a Conformal Array Antenna
17Defining Co-ordinate(θ,φ) is the direction in space
18Array Factor (AF)The array factor due to isotropic point sources is the weighted sum of the signals received by the elements.Mathematically,where N = number of elementsis the complex weight for element nk=2π/λ is the wave number(xn, yn, zn) is the location of element n
19Array Factor (AF) (cont.) Unique for each arrayDepends onnumber of elements,relative magnitude and phase of current on each element,relative inter-element spacing andgeometrical orientation of the elements.UsePattern Multiplication RuleIf the response of a single element of a linear array is 𝑬 𝒔then the total response of the array 𝑬 total can be written as,𝑬 total = 𝑬 𝒔 𝑨𝑭
20Concept of Phase Scanning Phase Scanning CircuitryWhy?Electronic Beam SteeringTechniqueTime Delay ScanningFrequency ScanningPhase ScanningWhy Phase Scanning?Ease of ImplementationCheaper Digital Control CircuitryFast Response TimeHigh Sensitivity
21Concept of Phase Scanning (cont.) How?By controlling the progressive phase difference between each individual elements of an array.ImplementationDiode Phase ShifterFerrite Phase ShifterIndustrial SolutionDigitally controlled fixed step phase shifterAnalog controlled continuous phase shifter
22Phase Scanning Technique ImplementationSeries PhasersAdvantage:Sharing Equal PowerDisadvantages:Unequal Inter-element Phase Shift,so complex control circuitry.Summed up AttenuationParallel PhasersAdvantages:Phase Shifters act independentlySimpler Control CircuitDisadvantage:Each phase shifter does not share equal powerExampleSwitched Line Phase ShifterFerrite Phase Shifter
23Conformal Antenna- Challenges and Solution For a conformal antenna, the surface of the substrate changes with time during operation.When the surface remains planar, the antenna behaves normally.However for non-planar orientation, the radiation pattern gets distorted.SolutionBy applying the concept of phase steering, correct radiation pattern can be recovered.
24Realization of Conformal Phased Array Antenna Realization of Conformal Phased Array Antenna Equation for Phase Correction Proposed System Block
25Determining possible conformal surfaces in terms of application Conformal Antennas are used basically as wearable antennas which may be shaped as wedge or cylindrical in non-planar orientation.
26A linear conformal array antenna placed on a Wedge shaped surface
27A linear conformal array antenna placed on a Cylindrical surface
28Equation for Phase Correction An x- and z- translation is incurred from the original flat position for each array element.Fields arriving at the reference plane associated with A±2 lagged from fields arriving at the reference plane associated with A±1.So, the phases of current at A±2 should be positive enough to compensate the phase delay by that free space propagation to maintain equivalent planar orientation.As the phase has being corrected towards the source, the phase correction will be additive in nature.For wedge shaped surface, this correction can be achieved by introducing phase 𝚫 𝜱 𝒏 𝒘 to each element where𝜱 𝒏 𝒘 = +𝒌𝑳|𝒏|𝐬𝐢𝐧 𝜽 𝒃For cylindrical surface, this correction can be achieved by introducing phase 𝚫 𝜱 𝒏 𝒄 to each element where𝜱 𝒏 𝒄 =+𝒌𝒓 𝒔𝒊𝒏 𝜱 𝒏 − 𝒔𝒊𝒏 𝜱 𝒏−𝟏
314-element antenna array with connectors g=2.0 mm, h=35.6 mm, t=1.3 mmw=43.6 mm.Rogers 6002(εr=2.94) 60 mil substrate.Resonant Frequency: 2.46 GHz
32Four port Receiver RF Circuit Board Consists ofVoltage controlled Analog Phase ShiftersVoltage Controlled AttenuatorsAmplifier andPower CombinerIndustry AvailableEach component was tested and verified prior to application with single prototype
33Control Voltage vs. Normalized Phase of the Phase Shifter
34Four port Receiver RF Circuit Board (cont.) Multiple Input Single Output SystemRT/duroid mil (εr=2.94)Controlled by DAC Circuit through LabVIEW GUI
35DAC Circuit 12 bit, octal, 64 pin, low power DAC Output ranges from 0V to 33 V for unipolar operationAllows programmable gain of x4 or x6 w.r.t the applied reference voltageFeatures Serial Peripheral Interface that can be operated at 50 MHz and is logic compatible with 1.8V, 3V or 5VThe register consists of a R/W bit, 5 address bits and 12 data bitsOperated in both synchronous and asynchronous modeTQFP(Thin Quad Flat Package)-64 (10 x 10mm) used
36LabVIEW GUINational Instrument LabVIEW USB 6008 peripheral device was used to communicate with the GUI4 phase shifters and 4 attenuators can be controlled by 8 separate output channels from DAC with precision up to 300 mV
45Gain CalculationThe primary objective through this correction is to recover the gain.If the reference gain of the system for a particular orientation is Gr(θ,Φ) and the compensated gain after the correction is Gc(θ,Φ), then for ideal conditionGr (θ,Φ) = Gc (θ,Φ)However, the projected spacing between the elements deviates from λ/2 value for any non-planar orientation.Due to this geometrical limitation, compensated gain can never be achieved to be equal to the reference gain. This gain shift (Gs) has been measured for all conformal cases and compared with analytical result.
47Test Platform Results Advantages Disadvantages Practically validates the theory of beam steeringAbility of recovering the radiation pattern has been demonstrated for a general arrayGain Calculation has been presented showing low loss of gainDisadvantagesManual control required for any changes of conformal surfaceThe array was formed by individual element with separate feeding points. But an array should be acting as an individual element.Gain shift
49SELFLEX Array Design Challenges Solution Can we design a conformal array on a single substrate with phase correction capability?Can we achieve radiation pattern recovery for a conformal array in an autonomous manner?Can we reduce the gain shift?SolutionBy designing a SELFLEX (SELF-adapting FLEXible) array antenna.
51Corporate Feed Network Why?Matching.TechniqueCorporate Feed Structure by using quarter-wave transformerExampleBifurcated T waveguide orcoaxial T-junctions.
52SELFLEX Array Design Features: Single feed point Insertion of phase shifters into corporate feed networkIntroduce the sensor circuit as the feedback network with autonomous controller circuitry for radiation pattern recovery
54How it WorksA flexible resistor senses the amount of curvature of the surface each time and feed that value to the controller circuit.The controller circuit consists of an instrumentation Op-Amp AMP04 that offers the phase shifter with necessary voltage correction for any conformal orientation.The phase shifters placed on the corporate feed network then process the signals from each array element resulting correction of radiation pattern of the array autonomously.
61Conclusion Conformal Phased Array Antenna Theory of Beam Steering Implementation of RF blockDesigning, printing and testing of a primitive conformal array that has the ability to compensate phase on each element with external manual control by the userDesigning, printing and testing of a 1x4 self-adapting antenna that can autonomously preserve its radiation field during conformal application