The Design And Implementation Of The Major Control Coding Unit For Traffic Collision Avoidance System

With the rapid development of civil aviation, air traffic is becoming increasingly busy, and the routes are also becoming crowded. Preventing collision between aircrafts and ensure the safety of aircrafts has become increasingly important. However, only rely on ATC system, we can not guarantee the safety of the aircraft completely. In order to realize the better communication between aircrafts, people of aerospace industry dedicated many years to develop the airborne collision avoidance system that TCAS system, it can effectively reduce the possibility of collisions, and avoid collision. This paper focuses on the design and implementation of Major Control Coding Unit of traffic collision avoidance system. This device can not only create inquiry signals, but also create many control signals that used to communicate with other parts of TCAS.In this paper, FPGA is chosen as the control unit. The design of hardware circuit and the inner logic of FPGA are two main parts. The hardware circuit is the platform of logic design. Among this paper, the design of mode C inquiry and mode S inquiry are the key points.The design of the hardware circuit includes FPGA core circuit, power management module, clock module, bidirectional bus transciver circuit, configuration and download circuit, etc.In the design of mode C, this paper uses whisper mode to reduce the interfered response signals that will be received from other aircrafts, and improve the efficiency of inquiries. When transmitting interrogation signals, the frame pulse is divided into two sections to make full use of the 4-beam directed antenna to form sum and difference beam by using the separability between C-mode inquiry pulses and sidelobe suppress pulse in time.Mode C inquiry signal is mainly produced by ASK modulation. The modulation of mode S interrogations includes two methods: ASK and DPSK. This paper also joins the cyclic redundancy check code to DPSK modulation method to improve the reliability of transmitting signals and anti-interference ability. Various informations can be transmitted such as the identity of aircrafts, address, height, e.t.c.This paper also designs the control and coordination with other parts, including the communication and control with the front device, the connection and control with decoding unit, e.t.c. This paper finally realizes the functions of coding module, and can meet the requirements of various inquiry times.