Applied Research To Restrain Electromagnetic Interference Based On The Two BTM Antennas

Receiving antenna is a very important part in Balise Transmission Module, which is responsible for the receive and send functions of 4.234MHz frequency signal. This paper have finish an impedance matching receiving antenna, and add using the Chebyshev second-order bandpass filter to the antenna’s filter circuit. in which the design center frequency is 4.234MHz, the bandwidth is 0.6MHz. so it can receive 4.234MHz frequency signal more effectively. according to the test result of antenna S11 parameter, the lowest point-18.5dBm is in the 4.2MHz frequency, VSWR is 1.27dB.For the test of the receiver system performance, first use the surge signal to simulate the interference signal of BTM, and find that the surge signal in frequency domain is a certain spectrum interference distribution at the band of 4.234MHz frequency. But in practical experiments. It is find that the test copper conduction surge waveform test signal out is not a standard waveform but a ringing waveform. In order to reduce the ringing phenomenon, we are trying series resistance, shunt resistance, pressure sensitive resistance to reduce it, eventually find in the load end parallel varistor can realize ringing weakened to a certain extent, but there are still ringing. Finally, we propose a transmission material diameter showed exponential form of further weakens the surge signal ringing.In the end, we test the actual antenna, and found that the anti-interference ability of a single antenna is weak. In order to improve the receiving antenna system anti-interference ability, we use the two antennas series to achieve interference on passive way. And in the 1MHz to 5.5MHz every 0.5MHz frequency interference signal to receive the test. Finally we find that interference cancellation method antennas results are less than the single antenna resultsaboutl6dB.According to this article, the realization of the receiving antenna design and the transmission line surge signal ringing weakened, but these are only in the laboratory to complete the design of experiment, is also a lack of practical field test. there must be more noise in the real environment test. and conditions are more complex, So in the future we need to further improve the responder receiving unit. Combined with other control parts of the locomotive when test, so that we can design a better receiving antenna unit.