1 research outputs found
Frequency diversity array: theory and design
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