Research On Modulation Technology Based On Frequency Diverse Array

In 2006, Antonik and Wicks proposed the frequency diverse array radar concept for the first time and applied for a US patent. The frequency diverse array radar has a linear increasing frequency offset between the array elements, which produces a range-angle dependent beampattern. In this thesis, we mainly study how to introduce the range-angle dependent beam characteristic of frequency diverse array into the traditional wireless communication model, and realize the safe transmission of the signal.The main work of this thesis includes the following three aspects:1. A method using time varying weight to realize static frequency diverse array beam is presented. Beam of traditional frequency diverse array is time variant, if loading the base-band information of the traditional modulation to each array element directly, the signal received by the receiver would be time varying and irregular in the symbol period and it would be difficult for the receiver to recover useful information. In this thesis, based on the study of time-independent frequency diverse array beam with time-dependent frequency offset, a method using time varying weight to realize time-invariant frequency diverse array beam is presented, simulation result show that this method is able to stay a longer time in target location and its project implementation is more simple.2. A range-angle modulation algorithm based on frequency diverse array is proposed. The direction modulation technology of the phased array used to realize secure communication is only based on receiver angle information. Frequency diverse array of time varying frequency offset is used to achieve the correct reception at the desired location and signal distortion at the non-desired position. The computer simulation results show that whether the receiver can demodulate the signal rightly is dependent on not only angle information but also the range information of the receiver,and it is a better physical layer security communication method.3. A range-angle modulation spread-spectrum signal is proposed using a switched antenna array. Based on time-varying frequency offset frequency diverse array, transmit antenna number is controlled by spread-spectrum sequence, the harmonic component produced by antenna high speed switching extended spectrum of transmitted signal inthe frequency domain, correct demodulation of received signal is not only related to the spreading sequence but also the spatial position information of receiver. Simulation results show that the modulation spread spectrum signal transmitted by the frequency diverse array model has the advantages of traditional spread spectrum technology and range direction modulation technology in secure communication.