Frequency diversity array: theory and design.
Doctoral thesis, UCL (University College London).
This thesis presents a novel concept of beam scanning and forming by employing frequency diversity in an array antenna. It is shown that by applying a linear frequency shift to the CW signals across the elements, a periodically scanning beam pattern is generated and the main beam direction is a function of time and range. Moreover, when transmitting a pulse signal, the frequency diversity array (FDA) can be used for beam forming in radar applications. These properties offer a more flexible beam scanning and forming option over traditional phase shifter implementations. The thesis begins with the discussion on FDA’s array factor. It is mathematically proven that the array factor is a periodic function of time and range and the scanning period itself is a function of the linear frequency shift. Then further discussion is made when a pulsed signal is transmitted by an FDA. The requirement on the pulse width for a certain linear frequency shift is specified and corresponding signal processing technique is provided for the frequency diverse signal receiver. The thesis subsequently goes on to an electromagnetic simulation of FDA. The CST Microwave Studio is utilized to model the FDA and simulate its transient field, which allows one to verify the relationship between the scanning period and the linear frequency shift. Finally, the implementation of FDA is considered with the focus laid on the generation of the required frequency diverse signals complying with the two basic assumptions. The PLL frequency synthesis technique is introduced as an effective approach of generating the frequency diverse signals. One low cost and profile design of integer-N frequency synthesizer is presented to illustrate the basic design considerations and guidelines. For comparison, a Σ − Δ fractional-N frequency synthesizer produced by Analog Device is introduced for designs where more budget is available.
|Title:||Frequency diversity array: theory and design|
|Open access status:||An open access version is available from UCL Discovery|
|UCL classification:||UCL > School of BEAMS > Faculty of Engineering Science > Electronic and Electrical Engineering|
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