Research On Key Technology Of Pseudo - Code Radio Altimeter

Radio Altimeter, one of the modern aircraft navigation electronic equipments, has a splendid prospects in the following fields:aircraft’s approach and landing, military aircraft’s bombing and attacking to ground, missile’s flying at extreme low altitude, as well as detonation of cluster bombs, etc. In order to meet Unmanned Aerial Vehicle (UAV) and cruise missile’s terrain matching needs, a subject for pseudo-random-code-based Radio Altimeter will be fully researched. It has certain advantages over the traditional ones in high dynamic range, high-precision range, strong anti-jamming capability and low transmission power. Based upon the Xilinx ISE Design Suite 13.1 software and an Atlys Spartan(?)-6 LX45 FPGA (Atlys) hardware development platform, this paper pays special attention to some key technology, important theories and algorithms related to the pseudo-random-code-based Radio Altimeter. The system is a hierarchical, software-based design with an interactive design methods of MATLAB and FPGA. It employs an Atlys FPGA board to implement the whole design, including the transmitter intermediate frequency module design implement and the receiver intermediate frequency module design implement, which proves the algorithms and codes to be practicable.In the first place, a brief introduction is made to the program architecture for the transmitter and the receiver of the pseudo-code-based Radio Altimeter in this paper. Besides, a thorough discussion is devoted to the Nyquist lowpass sample theory, bandpass sample theory and lowpass filter theory, etc. As is stated above, great emphasis is put on these fundamental theory for Software Radio.In the second place, choice for pseudo random code and generation theory for the "I" (In-Phase) channel and "Q" (Quadrature phase) channel pseudo code is introduced. Then, a combination range methods of pseudo random code and carrier phase is proposed to improve its range accuracy, and great importance is attached to several major theories and algorithms on the pseudo-random-code-based Radio Altimeter, including phase acquisition, digital phase locked loop, acquisition and tracking for pseudo code, Costas loop and square loop carrier synchronization technology.Last but not least, range capability of the Radio Altimeter is briefly analyzed.In addition, MATLAB simulation is done to the pseudo-code-based Radio Altimeter with the traditional PSK (phase shift keying) modulation and I/Q modulation schemes. It is used to verify whether or not the whole FPGA circuit can work properly and to generate the filter coefficients and test data for FPGA use, which improves the design efficiency and reduces the risk of the design.Finally, a hardware debugging and verification is conducted on the Atlys board, which realizes the major function of the pseudo-random-code-based Radio Altimeter medium-frequency module, tests and verities the key-techniques-based algorithm and the effectiveness of the software. It is thought to be of great significance to practical application.