In this paper, we introduce a new high-resolution reflectometry technique that operates simultaneously in both the time and frequency domains. The approach rests upon timefrequency signal analysis and utilizes a chirp signal multiplied by a Gaussian time envelope. The Gaussian envelope provides time localization, while the chirp allows one to excite the system under test with a swept sinewave covering a frequency band of interest. This latter capability is of particular interest when testing communication cables and systems. Sensitivity in detecting the reflected signal is provided by a time-frequency cross-correlation function. The approach is verified by experimentally locating various types of faults, located at various distances, in RG 142 and RG 400 coaxial cables.

Abstract-In this paper, RFID reader-to-reader interference is analyzed from the point of view of interrogation range. To evaluate RFID interference quantitatively, the new figure-of-merit, interrogation range reduction ratio (IRRR), is defined. In order to show the usefulness of IRRR, its value is calculated in various environments. Additionally, the calculated IRRR values are verified by measurements using two RFID readers and an RFID tag. IRRR can be referred to an important design parameter to analyze more complex interfering problems in instances of actual RFID system deployment.

This paper presents the development of a non-contact, nonintrusive wrist pulse sensor based on the near-field variation of an array resonator. A compact resonator and its array were designed and fabricated on flexible substrate. The reflection coefficient of the resonator can vary as a function of the distance between the resonator and the walls of the major arteries, and the corresponding variation is utilized to obtain heart rate information at the wrist. To detect very weak pulse signals from the main arteries, a sensitivity enhancement technique was devised using a radio frequency (RF) array resonator. The sensor system was implemented with an RF switch to combine or select appropriate signals from the resonator element and was tested using the 2.4 GHz ISM band. The results demonstrated the sensor system's excellent performance in both sequential and simultaneous detection schemes. The measurement results showed that a heartbeat pulse can be detected from both radial and ulnar arteries via the array resonators. Considering the high sensitivity and characteristics, the proposed detection system can be utilized as a wearable, long-term health monitoring device.

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