A successful case of railway interference signal detection

About the Institute of Communications and Signaling

The Communication and Signal Research Institute is a high-tech enterprise affiliated to the China Academy of Railway Sciences (CARS) in the field of railway communication and signal technology with integrated functions of scientific research, development, production, sales and service.

The Communication and Signaling Institute has seven professional divisions, including train control automation, station computer interlocking, train operation automatic control, marshaling yard automation, communication, optics, lightning and interference protection, and urban rail transit. It has three railway central laboratories for lightning protection, optics, and wireless communication, more than ten professional laboratories, and a comprehensive test base for circular railway communication and signal systems. It is mainly engaged in the research of lightning interference protection and urban rail transit safety.

Main test questions

The institute had purchased a DPO3000 oscilloscope to view the waveform of the signal. It was very inconvenient to simply view its spectrum using the oscilloscope's FFT function, as more spectrum details could not be seen. If a spectrum analyzer was used, the time domain waveform could not be viewed at the same time.

Problem Solution

In response to the above problems reported by the Institute of Communication and Signal Engineering of the China Academy of Railway Sciences, we visited the institute on November 8, 2011 and conducted an on-site demonstration. We recommend using the Tektronix mixed domain oscilloscope MDO4104-3 and using the channel (CH1, RF channel) for test demonstration.

Test steps:

1. The antenna picks up interference signals and uses the three-way interface to connect CH1 and RF channels.

2. Open CH1 and RF channels

3. Set CH1 to edge trigger

4. Set the frequency range and center frequency of RF

5. Open the RF channel frequency trajectory over time

6. Set the oscilloscope to single sampling

Center frequency 500MHz, bandwidth 1GHz, test results: time domain and frequency domain waveforms of interference signals

Center frequency 125MHz, bandwidth 250MHz, CH1 bandwidth limit 250MHz, test results: time domain and frequency domain waveforms of interference signals

Case summary

Through the test demonstration, the new cross-domain analysis function of MDO4104-3 was demonstrated, and the Communication Signal Research Institute of the Railway Science Institute was very satisfied. The feedback from the Communication Signal Research Institute of the Railway Science Institute was: the MDO4000 series oscilloscope is both an MSO oscilloscope and a spectrum analyzer, with powerful functions and high cost performance; the cross-domain analysis function of the MDO mixed domain analyzer is appreciated, which solves the time synchronization problem of the oscilloscope and the spectrum analyzer. These features are exactly the test instruments they need at this stage, which can meet their test needs and greatly improve work efficiency.