High-speed Rail EMU CIR New Band-pass Filter Design And Implementation

In recent years, with the rapid development of high-speed railway, special450MHzmore and more difficult to satisfy the complex transport requirements. Therefore, therailway wireless communication system to the original450MHz (457-469MHz) frequencyband to add new bands individually used for train tail wind pressure braking system toensure traffic safety. The original small CIR filter has three operating bands, respectively,for scheduling457-469MHz band,821-869MHz for data and voice band for885-934MHz.This means that the filter in addition to the small size, high selectivity, lowinsertion loss, but also to meet the450MHz adjacent in the band-pass sufficient attenuation.Usually, this type of filter are adopted the Generalized Chebyshev filter to realize thecommunication of the system requirements.This paper analyzes the polynomials, the Generalized Chebyshev filter, S parameterequivalent circuit and the coupling matrix, to achieve the above requirements by using theGeneralized Chebyshev filter.Generalized Chebyshev filter can take an arbitrary position isarranged in the through out of band transmission zero, so you can filter more flexibleadjustment in the condition of not increasing the loss under the out of band rejection, andachieves very high rectangular coefficient. In addition, by increasing the cross couplingbetween the non adjacent to the cavity, the transmission zero of General Chebyshev filtercan become complex, so can optimize the pass band of the group delay and reduce thedistortion of the signal characteristics. This paper focuses on the research of the structuralprinciple, the Generalized Chebyshev filter realization form and test methods, in order tofolding topology design of a novel band-pass Chebyshev filter. The design of the filter hasfour operating bands, respectively, for the446.5-451.5MHz train tail, for scheduling 457-469MHz band,821-869MHz for data and voice band for885-934MHz band.Experimental results show that, the combiner for each frequency band reached theinsertion loss is less than or equal to1.2, the out of band rejection is more than75, lessthan1.5of these parameters in Bobbi. The use of the new filter in wireless traindispatching system work normally, by the railway administration on the road test.Afterimprovement, new filter can also be used in subway800MHzTETRA digital trunkingsystem.