Jinsong Song

Optimization of Wireless Sensors Based on Intermodulation Communication

Intermodulation communication principle has been recently developed to wirelessly read-out passive sensors. Intermodulation communication sensors reply the sensor information at an intermodulation frequency when interrogated by a reader device with two tones. This paper derives an analytical expression for optimizing the electrical circuitry of such a sensor. The derived equations are verified by harmonic balance simulations. An optimized sensor is designed and fabricated and experimentally characterized. Results show that 1% change in the sensor capacitance can still be detected at a 13 m-distance and the read-out principle could enable an extreme resolution at shorter distances (less than per mille below 5 m). A wireless electrocardiography measurement is demonstrated.

Passive Wireless Sensor Platform Utilizing a Mechanical Resonator

This paper presents a new passive wireless sensor platform on the basis of the intermodulation communication principle. The platform utilizes a quartz crystal or other mechanical resonator and it enables a narrow bandwidth and ID-code to the sensor. A previously presented theory for predicting the intermodulation response of the sensor is elaborated and verified by a simulation. The concept is experimentally demonstrated at 1.2 GHz.

Maximum-Likelihood Estimation for Passive Wireless Intermodulation Communication Sensors

The intermodulation communication principle has recently shown several advantages over other passive wireless sensor readout techniques. The advantages include a large readout distance and the possibility of using generic sensor elements. In this paper, we derive an algorithm to estimate the quantity measured by the wireless sensor from its intermodulation response and verify the algorithm experimentally with a passive wireless inclinometer sensor operating at 860 MHz. The results can be further used to realize a reader device for intermodulation communication sensors, maximize its operational parameters, and optimize the sensor structure for the best readout resolution.

Optimization of RFID Sensor With Frequency Modulation

Sensing capabilities of radio frequency identification (RFID) have recently been investigated both theoretically and experimentally. Frequency-modulated sensors utilize the modulation frequency for carrying sensor information when interrogated by a reader device. This paper derives analytical expressions for optimizing the electrical circuitry of such a sensor, as well as a figure of merit for selecting a suitable diode for rectification. A novel design strategy for optimizing an RFID sensor based on frequency modulation is presented, and it is used to design, fabricate, and experimentally characterize an optimized sensor. The result of this paper shows that a change in the sensor capacitance can be detected across a distance of 15 m with low uncertainty.

Achieving long reading ranges with passive wireless intermodulation sensors

This paper presents a system architecture combining batteryless wireless intermodulation sensors and their associated reader, and analyses the achievable read range of such sensor-reader system. The computed read range is compared to those provided by harmonic and passive UHF RFID sensor systems. Effects of both reader thermal noise and third-order distortion by the reader itself on the read range of the system are considered, by means of theoretical analysis, simulations and measurements. The presented reader with a distortion-limited sensitivity of -70 dBm at the receiver input provides a 7 m measured and a 9 m simulated read range.

Review of passive wireless sensors utilizing the intermodulation communication

This paper reviews different kinds of passive wireless sensors utilizing the intermodulation communication principle. The reviewed sensor architectures are based either on a mechanical resonator, electrically non-linear sensing element, or on a separate mixer, low-frequency resonance circuit and a sensing element. The benefits and drawbacks of different architectures are compared and some experimental measurement results are presented.

Integrated passive wireless sensor transponders based on the intermodulation communication principle

This paper describes a passive wireless sensor platform where passive components are realized using the Integrated Passive Device (IPD) process. The sensor platform utilizes the intermodulation communication principle. The concept is experimentally verified with a MEMS accelerometer sensor used to measure the sensors inclination in a static gravitational field. Results show that inclination can be measured across a distance of several meters, hence demonstrating long range passive sensor reading while achieving high component integration level.