Broadband Filter Design and Optimization for Perimeter Intrusion Detection Systems

Aiming at the problem of large insertion loss and bad in鄄band flatness of traditional m-derived filter, an improved design method of band pass filter is proposed. In this paper, the design method of the filter is introduced first, and the parameters of the filter are optimized by ADS and the band pass filter samples were prepared by PCB process for the measurement of transmission characteristics. Finally, the filter is applied to the perimeter detection systems of the leakage cable to improve the signal to noise ratio of hardware front end. The measurement results show that in the pass band range of 25.75 ~ 36. 25 MHz, the insertion loss is less than 1. 5 dB, the flatness is better than 0. 5dB, the reflection coefficient is less than -15 dB, and the transitional band is ideal. At the notch points of 20 MHz and 45 MHz, attenuation is greater than -50dB. At the end of this paper, it provides the preliminary measurement of missing report rate, false detection rate and correct rate for perimeter intrusion detection system, the results show that the false alarm rate reduces from 1 per hour to no alarm within 2 days. The structure of this filter effectively reduces false alarm rate and improves system stability.