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Remote detection and tracking of wingtip generated wake vortices is important for hazard avoidance especially near airports. Aircraft that fly through these hazardous vortices experience sudden induced roll. Experiments have demonstrated that there is sufficient radar cross section for remote detection at frequencies ranging from VHF to C band (100 MHz to 5 GHz). The mechanism that yields this radar cross section is Bragg scattering from the index of refraction variations due to the atmospheric water vapor and potential temperature fields being mixed by the wake vortex system. Refractive index variations of the size that correspond to half the operating radar wavelength produce the observed radar return. Previous analysis has postulated turbulence within the wake vortex to be the generator of the index of refraction variations. In this work, a new mechanism is identified that does not assume turbulence within the wake vortex system. This "laminar flow mechanism" causes refractive index structuring that stretches into successively smaller spirals over time as the wake vortex system swirls and descends through the stratified atmosphere. The results are quantitatively consistent with experimental data. Results indicate that this new mechanism has a sharply peaked doppler spectrum which is encouraging for coherent detection by doppler radar. / Ph. D.

This report presents a general procedure for estimating the average clutter power received by an airborne Doppler radar as a function of time and frequency. Its purpose is to construct the received power waveform at the output of a matched filter for use in the development of clutter maps related to Doppler signal processing. In developing the algorithm, several of its features are given close examination; this includes a numerical and analytical justification for the azimuth to Doppler coordinate transformation, and the power spectrum returned to the airborne Doppler radar from the surface it illuminates. This algorithm produces a continuous power returned waveform versus time. Hence, this algorithm has the flexibility to accept any surface radar cross section, antenna gain, and pulse type (a matched filter receiver is assumed) as a function of range and azimuth. It was discovered that the algorithm could be executed with significantly less computer time if the integration surface area was reduced by exploiting some physical insight. In addition, it was discovered through example that the refracting effects of the Earth's atmosphere become important as the radar's beam approaches the horizon. Finally, return power waveforms are studied for two different situations: near nadir pointing, and near horizon pointing. The manner in which the matched filter ambiguity function and the spectrum of backscattered power combine to produce these waveforms is examined. / Master of Science

Doppler tracking of the Navy Navigation Satellite System (NNSS) gives solutions for polar motion as a by-product of the orbital computation process. The polar motion estimation process at the Defense Mapping Agency is reviewed and comparisons of the Doppler results with the polar motion series of the newer techniques, Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI), and the Bureau International de l'Heure (BIR) Circular-Dare made. TwoChandler periods of data are analyzed beginning with the start of the Main MERIT Campaign in September 1983. The two major components, annual and Chandler wobble, are removed. The resulting residuals, as well as those obtained by differencing all combinations of Doppler series and the three reference series, are smoothed by different techniques. The 'seven-point moving average' and the Vondrak smoothing algorithm are the two smoothers applied. A computational spectral analysis is presented that determines which periods dominate the residuals. / M.S.

Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2008. / This thesis discusses the design, development and measured results of a phase-locked loop based frequency synthesiser for X-band Doppler radar. The objective is to obtain phase noise comparable or lower than that typically achieved with direct analogue frequency synthesis techniques. To meet this objective, a theoretical study of the noise contributions of individual components of the synthesiser and their effect on the total phase noise within and outside the loop bandwidth of the PLL is performed. The effect of different phase margins on the closed-loop frequency response of the PLL, and hence the total phase noise, is investigated. Based on the results, an optimal phase-frequency detector reference frequency, loop bandwidth, adequate phase margin, and suitable components are chosen for optimal phase noise performance. The total phase noise at the output of the synthesiser is calculated and it is shown that the phase noise specification can be met. A significant part of this thesis is devoted to the design, modelling and characterisation of a frequency multiplier, as well as to a combline and interdigital bandpass filter required for the frequency synthesiser. In the first case, a piecewise linear circuit model is used to model the behaviour of the nonlinear multiplier circuit. Fourier theory is used to calculate the large-signal driving point input and output impedances of the nonlinear circuit, enabling the computation of the circuit elements for the input and output matching networks. The measured response of the frequency multiplier under various different operating conditions is presented and discussed. The design of the microwave bandpass filters is based on the theory of coupling and external quality factors. To aid in the verification and optimisation of the design, a software simulation tool is used. The presented S-parameter measurements of the filters show how well the theory matches with what is obtained in practice. The measured spectral and phase noise response of various components comprising the synthesiser, are discussed. These measurements provide insight into the response of individual components under different operating conditions and show the behaviour of important subsystems of the synthesiser. The thesis culminates in the presentation of the measured phase noise of the complete synthesiser. It is shown how well the measured phase noise correlates with the calculated phase noise. In addition, the measured spectral content and transient behaviour of the synthesiser are investigated and discussed. High power spurious components at some output frequencies are indentified and reduced. The feasibility of using the developed prototype phase-locked loop based frequency synthesiser for coherent X-band Doppler radar is discussed and demonstrated.

"July 2003." Includes bibliographical references (leaves 459-484) Electronic publication; full text available in PDF format; abstract in HTML format. Details the application of a medium frequency Doppler radar to observations of meteorites entering the Earth's atmosphere. Techniques were developed that verified system performance was to specification Electronic reproduction.[Australia] :Australian Digital Theses Program,2001. xx, 485 leaves : ill. ; 30 cm.

A passive radar systems opportunistic ability to exploit ambient radio signal reflections makes it ideal for covert target tracking. This strategy, referred to as passive covert radar (PCR) or passive coherent location (PCL), typically exploits FM radio or television signals from powerful local transmitters. In addition to covertness, the absence of a dedicated transmitter helps reduce costs and overall system complexity. While a variety of measurements can be used to estimate a targets position and velocity, such as time difference of arrival (TDOA) and direction of arrival (DOA), this thesis focuses on using only Doppler shift measurements to estimate a targets state. The work presented in this thesis examines the use of Doppler shift measurements from multiple receivers to solve the target tracking and association problem. A nonlinear least squares error (NLSE) estimation technique, called the Levenberg-Marquardt (L-M) algorithm, is used to determine a targets state (position, velocity) from these Doppler shift measurements. More than one target state can potentially produce identical Doppler shift profiles. In a single-receiver, single-target scenario, it is shown that three additional ghost targets caused by symmetry produce the same Doppler shift response. These ghosts may make state estimation impossible if receive antennas are not physically positioned to block out ghost targets. While the NLSE technique tends to give an accurate solution in one quadrant, three other solutions will symmetrically exist in each of the remaining three quadrants. The addition of either another receiver or another measurement (such as DOA) is needed to break this quadrant ambiguity. This thesis considers adding multiple receivers to accurately associate and track multiple targets. Two target association methods (sequential and simultaneous) are developed, and their computational requirements and accuracy are compared. A grid-aided L-M search technique is investigated in an attempt to provide a better initial target state guess to these association and tracking algorithms. The analysis and simulation results suggest it is feasible to perform multi-target association and tracking using Doppler shift as the sole measurement. Both of the proposed methods gave optimal target association and converged to reasonably accurate state estimates in most of the Monte Carlo runs.

Active integrated antennas (AIAs) are divided into oscillator type AIAs, amplifier type AIAs and frequency-conversion type AIAs. The AIAs designed in this master thesis are oscillator type. Instead of using lumped component like inductors and capacitors, I use a half-wavelength antenna as resonator. In this design, antenna is also treat as a radiated loading. According to reciprocity, antenna receives the reflection signal affected by human body movement and vital sign at the same time. This behavior is regarded as a self-injection locking oscillator. In this master thesis, active antenna is used in monitoring and contacting measurement. In monitoring measurement, active antenna and subject keep their distance. Subject random body movement affects the measured result. Contacting measurement means active antenna pastes on the subject, thus there is no relative displacement between active antenna and subject. Random body movement affect iscancelled in theory. In contacting measurement design some different body motions to test the tolerance of this measurement structure, and use correlation to cancel random body movement. The sensitivity of active antenna structure is enough to detect the vocal vibration in contacting measurement.

abstract: Doppler radar can be used to measure respiration and heart rate without contact and through obstacles. In this work, a Doppler radar architecture at 2.4 GHz and a new signal processing algorithm to estimate the respiration and heart rate are presented. The received signal is dominated by the transceiver noise, LO phase noise and clutter which reduces the signal-to-noise ratio of the desired signal. The proposed architecture and algorithm are used to mitigate these issues and obtain an accurate estimate of the heart and respiration rate. Quadrature low-IF transceiver architecture is adopted to resolve null point problem as well as avoid 1/f noise and DC offset due to mixer-LO coupling. Adaptive clutter cancellation algorithm is used to enhance receiver sensitivity coupled with a novel Pattern Search in Noise Subspace (PSNS) algorithm is used to estimate respiration and heart rate. PSNS is a modified MUSIC algorithm which uses the phase noise to enhance Doppler shift detection. A prototype system was implemented using off-the-shelf TI and RFMD transceiver and tests were conduct with eight individuals. The measured results shows accurate estimate of the cardio pulmonary signals in low-SNR conditions and have been tested up to a distance of 6 meters. / Dissertation/Thesis / M.S. Electrical Engineering 2013