| Radio compass is one of the most important airborne navigation equipment, which canindicate the relative azimuth angle of the radio beacon station continuously and guide theaircraft toward or back the beacon. The pros and cons of its performance directly affect thescheduled flights of the aircraft. Therefore, testing of the performance and sensitivity of theradio compass is a very important part in the aviation maintenance work. The traditionalsensitivity detection system of radio compass adopts the electromechanical FM phasemodulation techniques, which are not only too large and inconvenient to carry, but also proneto interference and has the shortcomings of low precision and poor reliability.In recent years, as the rapid development of DDS technology, its applications havebecome more and more widely in modern frequency synthesis. DDS has the advantages ofrelatively large bandwidth, short frequency conversion time, continuous high frequencyresolution, output phase modulation signal variety, strong programmability and convenientcontrol. At present, it has been widely used in electronics and played important roles in thedevelopment of navigation, radar and electronic countermeasures. Therefore, integrate theDDS into the radio compass detection system and use it for the synthesis of radio compasssensitivity test signal can not only improve the stability and precision of the detection signalbut also greatly reduce the volume of the detection system and power consumption, which hasvery good practical values and development prospects.This dissertation puts forward a new kind of radio compass test signal generator designbased on DDS technology. The design uses PC as the man-machine interface and useAtmega32as communication control unit to control the DDS for the generation of signalsused in receiver sensitivity and directional sensitivity detection of the radio compass. Thesignal generator is so powerful that it can produce many kinds of modulation waveform andachieve the accurate regulation of amplitude and frequency. It can be applied to the radiocompass system, which can simulate the ground navigation signal received by radio compassaccording to the certain phase, frequency and amplitude, and then, it will cooperate with othermeasuring instrument for the test of radio compass receiving sensitivity and directionalsensitivity. Finally, we make the actual circuit according to the design plan and then carry onthe experiments and simulations.The experiment results showed that the test signal produced by the scheme can fullysatisfy the requirements of the testing for the radio compass detection system. Farther more, itcan greatly reduce the cost and power consumption and improve the accuracy of the wholesystem stability after its application to the radio compass detection system. |
