Battery-Less RFID-Based Wireless Sensors: Comparison
Please note this is a comparison between Version 2 by Beatrix Zheng and Version 1 by Nabil Khalid.

Wireless sensors are becoming increasingly popular in the home and industrial sectors and are used for a range of applications, from temperature or humidity monitoring to food-quality inspection of products being sold on the market. One of the main reasons for using wireless technology is that it affords non-contact, non-invasive sensing. This ability eliminates the need for long cables required for information transfer and reduces the spread of germs and brings comfort to the users.

  • battery-less
  • IoT
  • radio frequency identification (RFID)
  • sensor
  • zero-power

1. Introduction

Wireless sensors are becoming increasingly popular in the home and industrial sectors and are used for a range of applications, from temperature or humidity monitoring to food-quality inspection of products being sold on the market. One of the main reasons for using wireless technology is that it affords non-contact, non-invasive sensing. This ability eliminates the need for long cables required for information transfer and reduces the spread of germs and brings comfort to the users. To fully exploit the capabilities of wireless sensors and automatic processes, the future generation of wireless communication, 5G, and the evolving Industry 4.0 aims to incorporate them on a massive scale. Research on wireless sensors is on a dramatic rise [1,2,3][1][2][3].

A sensing element may be incorporated in any of the aforementioned categories to design an RFID sensor. Using active or semi-passive technology requires a power source, which makes the wireless sensor bulky and expensive, whereas passive technology is much cheaper, but incorporating sensing elements in it is quite challenging due to the limited available power and flexibility. Hence, passive technology must be carefully engineered to address these challenges [3,11,13,14,15,16,17,18,19,20][3][4][5][6][7][8][9][10][11][12].

RFID is now a widely used technology for tracking and inventory management services and, as such, is governed by several design standards [21][13]. However, wireless sensors, especially RFID-based sensors, are still an emerging technology and might be referenced using different names in the community. Particularly, passive wireless sensors are sometimes also termed battery-less, self-powered, or even zero-power [8,11,12,22,23,24,25,26,27,28][14][4][15][16][17][18][19][20][21][22].

Battery-less RFID-based wireless sensors

The remainder of this article is organized as follows. In Section 2, we discuss the individual components of RFID-based wireless sensors to develop a basic understanding of how they may be engineered to meet the requirements, e.g., complexity, cost, size, read range, and accuracy of a given application. In Section 3, the system topologies of different categories of battery-less RFID-based wireless sensors are discussed in the context of their complexity, cost, size, read range, and accuracy. Finally, potential future directions are presented in Section 5, and then, the paper is concluded in Section 6.

2. Individual Components of an RFID-Based Wireless Sensor System

An RFID-based wireless sensor consists of several components. A block diagram of all the key components is shown in the figure below, and details of each component are discussed in the following paragraphs.

An antenna is a transducer that converts free space electromagnetic energy to guided electromagnetic energy and vice versa to enable wireless communication in an RFID system. Although any radiating structure can be termed as an antenna, the efficiency with which it can transform the electromagnetic energy plays a major role in determining its amenability for use in sensor communication [29][23].

A rectifier in an RFID tag is the main circuit that converts the incident electromagnetic energy received by the antenna into a DC supply voltage. This voltage is required to operate all the internal circuitry of the tag, which includes the analog circuitry, base-band DSP circuitry, and memory of the tag [66,67,68,69,70][24][25][26][27][28].

If standard threshold voltage CMOS devices are used, the rectifier cannot be turned on when the voltages at its terminals are lower than its turn-on voltage, which affects the read range of the RFID tag. Solutions using near differential-drive rectifier, photovoltaic-assisted rectifier, and zero threshold-based technologies such as Silicon-on-Sapphire and Hetero-junction Tunnel FET provide a significant improvement to the read range [44,76,77,78,79,80,81,82,83,84][29][30][31][32][33][34][35][36][37][38].

3. System Topologies

Different arrangements and utilization of the RFID tag’s components can result in different topologies. There are five principal topologies used, each offering different levels of complexity, cost, read range, and accuracy.

The simplest form of RFID sensor requires no integrated circuits (ICs) and communicates sensed data by simply varying the radar cross-section (RCS) of the tag at a certain frequency. To read data from a chip-less RFID sensor, a reader transmits a frequency sweep signal of a specific bandwidth and analyzes the backscattered signals that it receives. These backscattered signals are affected by the physical location of the sensor and its RCS. If the physical location and distance between the sensor and the reader are fixed, then the effect of the physical location can be easily factored out to determine the RCS, specifically of the sensor [103,104,105,106][39][40][41][42].

To address the challenge of multi-path propagation and to support multiple sensors in close proximity, wireless sensors must incorporate digital communication techniques. This is achieved in chip-based RFID tags, where the backscattering is digitally controlled and acts as a digitally modulated signal. This topology ensures that the power-up signal reaches the RFID tag without any significant loss. The backscattered signal is sent to the sensing element where an additional phase delay is introduced. Chip-based RFID tags based on this protocol can be modified in several ways to integrate sensors inside them. These modifications generally include an antenna-resonance shifting-based sensor, a multi-port architecture to remove the sensing element from the incoming signal path, a digitally integrated sensor using digital circuitry, and an ambient energy-harvesting block to get additional power from the surroundings.

Amongst all, multi-port architecture-based wireless sensors are very promising as the sensor utilizes a hybrid of digital and analog communications. Maximum received signal power is ensured by removing the sensor from the incident signal path and information is incorporated in the phased of the backscattered digital signal. Although having a sensor circuit introduces extra loss in the backscattered signal, the reader is connected to a power source and can interpret and demodulate a fairly low-power signal. Therefore, this topology provides an improvement in terms of read range compared to other topologies. Since the sensor information is a hybrid of digital and analog communication, the required bandwidth is low. However, having a multi-port device requires components that may increase the cost by a few dollars. Sensors with medium accuracy operating at a range of 7 m have been reported in [39,40,41][43][44][45].

The sensor information may also be digitally integrated along with the identification however the main challenge is having digital circuitry that operates at very low voltage and uses a minimum amount of power to read the sensed value with suitable accuracy. This added circuitry can significantly reduce the read range of an RFID chip and can slightly increase its cost. Currently, sensors utilizing this topology have been demonstrated with read ranges of around 0.7–2.2 m [42,43][46][47]. It should be noted that, since the sensor information is communicated digitally, the accuracy is high and the bandwidth is the same as a regular RFID chip.

4. Future Directions

Although a vast amount of research has already been carried out on battery-less RFID-based wireless sensors, it is clear that a great deal of potential remains for future discoveries. Among the several sensor parameters discussed in this review (e.g., read range, accuracy, cost, and size), it is evident that an improvement in sensor read ranges is still of prime interest to the community. By looking at the aforementioned topologies, we can deduce that a combination of chip-based multi-port and ambient energy harvesting can yield a much higher range—theoretically, up to 50 m.

We also saw that the size and cost of the multi-port topology are not optimal but may be significantly improved through the use of highly miniaturized antennas employing novel matching techniques to enable compact, long-range RFID-based battery-less wireless sensors [60,61][48][49].

If accuracy is a concern, digitally integrated sensor topologies with ambient energy harvesting show a great deal of promise. To increase the read range, ambient PV and RF energy may be combined. Moreover, the fabrication of the rectifier circuitry must be engineered to achieve better results. This involves using detailed models of the fabrication process that produce more accurate results and higher consistencies between different batches.

Lastly, we observed that there is a scarcity of sensor components operating in the low GHz range. Research that seeks high-frequency sensing component designs is also needed. This will allow RFID-based battery-less sensors to be used in many new applications, readying them for deployment in the future Internet-of-Things.


  1. Wollschlaeger, M.; Sauter, T.; Jasperneite, J. The future of industrial communication: Automation networks in the era of the internet of things and industry 4.0. IEEE Ind. Electron. Mag. 2017, 11, 17–27.
  2. Sisinni, E.; Saifullah, A.; Han, S.; Jennehag, U.; Gidlund, M. Industrial internet of things: Challenges, opportunities, and directions. IEEE Trans. Ind. Inform. 2018, 14, 4724–4734.
  3. Mc Gee, K.; Anandarajah, P.; Collins, D. Current Progress towards the Integration of Thermocouple and Chipless RFID Technologies and the Sensing of a Dynamic Stimulus. Micromachines 2020, 11, 1019.
  4. Muratkar, T.S.; Bhurane, A.; Kothari, A. Battery-less internet of things—A survey. Comput. Netw. 2020, 180, 107385.
  5. Węglarski, M.; Jankowski-Mihułowicz, P. Factors affecting the synthesis of autonomous sensors with RFID interface. Sensors 2019, 19, 4392.
  6. Zhang, J.; Tian, G.Y.; Marindra, A.M.; Sunny, A.I.; Zhao, A.B. A review of passive RFID tag antenna-based sensors and systems for structural health monitoring applications. Sensors 2017, 17, 265.
  7. Marrocco, G.; Amato, F. Self-sensing passive RFID: From theory to tag design and experimentation. In Proceedings of the 2009 European Microwave Conference (EuMC), Rome, Italy, 29 September–1 October 2009; pp. 1–4.
  8. Ferdous, R.M.; Reza, A.W.; Siddiqui, M.F. Renewable energy harvesting for wireless sensors using passive RFID tag technology: A review. Renew. Sustain. Energy Rev. 2016, 58, 1114–1128.
  9. Ma, S.; Pournoori, N.; Sydänheimo, L.; Ukkonen, L.; Björninen, T.; Georgiadis, A. A Batteryless Semi-Passive RFID Sensor Platform. In Proceedings of the 2019 IEEE International Conference on RFID Technology and Applications (RFID-TA), Pisa, Italy, 25–27 September 2019; pp. 171–173.
  10. Rida, A.; Yang, L.; Tentzeris, M.M. RFID-Enabled Sensor Design and Applications; Artech House: Norwood, MA, USA, 2010.
  11. Merenda, M.; Felini, C.; Della Corte, F.G. Battery-less smart RFID tag with sensor capabilities. In Proceedings of the 2012 IEEE International Conference on RFID-Technologies and Applications (RFID-TA), Nice, France, 5–7 November 2012; pp. 160–164.
  12. Kantareddy, S.N.R.; Mathews, I.; Bhattacharyya, R.; Peters, I.M.; Buonassisi, T.; Sarma, S.E. Long range battery-less PV-powered RFID tag sensors. IEEE Internet Things J. 2019, 6, 6989–6996.
  13. Zhang, J.; Periaswamy, S.C.; Mao, S.; Patton, J. Standards for passive UHF RFID. GetMobile Mob. Comput. Commun. 2020, 23, 10–15.
  14. Cook, B.S.; Vyas, R.; Kim, S.; Thai, T.; Le, T.; Traille, A.; Aubert, H.; Tentzeris, M.M. RFID-based sensors for zero-power autonomous wireless sensor networks. IEEE Sens. J. 2014, 14, 2419–2431.
  15. Kim, S.; Mariotti, C.; Alimenti, F.; Mezzanotte, P.; Georgiadis, A.; Collado, A.; Roselli, L.; Tentzeris, M.M. No Battery Required: Perpetual RFID-Enabled Wireless Sensors for Cognitive Intelligence Applications. IEEE Microw. Mag. 2013, 14, 66–77.
  16. Yi, X.; Wu, T.; Wang, Y.; Leon, R.T.; Tentzeris, M.M.; Lantza, G. Passive wireless smart-skin sensor using RFID-based folded patch antennas. Int. J. Smart Nano Mater. 2011, 2, 22–38.
  17. Opasjumruskit, K.; Thanthipwan, T.; Sathusen, O.; Sirinamarattana, P.; Gadmanee, P.; Pootarapan, E.; Wongkomet, N.; Thanachayanont, A.; Thamsirianunt, M. Self-powered wireless temperature sensors exploit RFID technology. IEEE Pervasive Comput. 2006, 5, 54–61.
  18. Vaz, A.; Ubarretxena, A.; Zalbide, I.; Pardo, D.; Solar, H.; Garcia-Alonso, A.; Berenguer, R. Full passive UHF tag with a temperature sensor suitable for human body temperature monitoring. IEEE Trans. Circuits Syst. II Express Briefs 2010, 57, 95–99.
  19. Wickramasinghe, A.; Ranasinghe, D.C. Ambulatory monitoring using passive computational RFID sensors. IEEE Sens. J. 2015, 15, 5859–5869.
  20. Manzari, S.; Catini, A.; Pomarico, G.; Di Natale, C.; Marrocco, G. Development of an UHF RFID chemical sensor array for battery-less ambient sensing. IEEE Sens. J. 2014, 14, 3616–3623.
  21. Caccami, M.; Mulla, M.; Occhiuzzi, C.; Di Natale, C.; Marrocco, G. Design and experimentation of a batteryless on-skin RFID graphene-oxide sensor for the monitoring and discrimination of breath anomalies. IEEE Sens. J. 2018, 18, 8893–8901.
  22. Boaventura, A.J.S.; Carvalho, N.B. A batteryless RFID remote control system. IEEE Trans. Microw. Theory Tech. 2013, 61, 2727–2736.
  23. Karmakar, N.C. Handbook of Smart Antennas for RFID Systems; John Wiley & Sons: Hoboken, NJ, USA, 2011.
  24. Ma, C.; Zhang, C.; Wang, Z. A Low-Power AC/DC Rectifier for Passive UHF RFID T. In Proceedings of the 2007 International Symposium on Microwave, Antenna, Propagation and EMC Technologies for Wireless Communications, Hangzhou, China, 16–17 August 2007; pp. 309–314.
  25. Divakaran, S.K.; Krishna, D.D.; Nasimuddin. RF energy harvesting systems: An overview and design issues. Int. J. RF Microw. Comput. Aided Eng. 2019, 29, 1–15.
  26. Ghovanloo, M.; Atluri, S. An integrated full-wave CMOS rectifier with built-in back telemetry for RFID and implantable biomedical applications. IEEE Trans. Circuits Syst. I Regul. Pap. 2008, 55, 3328–3334.
  27. Mohd, Y.; Khaw, M.; Reaz, M. Radio frequency identification: Evolution of transponder circuit design. Microw. J. 2006, 49, 56.
  28. Teh, Y.; Mohd-Yasin, F.; Choong, F.; Reaz, M.I. Development of CMOS UHF RFID modulator and demodulator using DTMOST techniques. In Proceedings of the 2009 IEEE 8th International Conference on ASIC, Changsha, China, 20–23 October 2009; pp. 561–564.
  29. Usami, R.; Komiyama, T.; Chonan, Y.; Yamaguchi, H.; Kotani, K. Photovoltaic-assisted self-Vth-cancellation CMOS rectifier for synergistic RF energy harvesting. IEICE Electron. Express 2020, 17, 1–6.
  30. Theilmann, P.T.; Presti, C.D.; Kelly, D.; Asbeck, P.M. Near zero turn-on voltage high-efficiency UHF RFID rectifier in silicon-on-sapphire CMOS. In Proceedings of the Digest of Papers—IEEE Radio Frequency Integrated Circuits Symposium, Anaheim, CA, USA, 23–25 May 2010; pp. 105–108.
  31. Liu, H.; Vaddi, R.; Datta, S.; Narayanan, V. Tunnel FET-based ultra-low power, high-sensitivity UHF RFID rectifier. In Proceedings of the International Symposium on Low Power Electronics and Design (ISLPED), Beijing, China, 4–6 September 2013; pp. 157–162.
  32. Teh, Y.K.; Lam, W.K.; Khaw, M.K.; Mohd-Yasin, F.; Reaz, M.I.; Sulaiman, M.S. The design of batteryless, TIRIS/spl reg/-compliant RFID transponder IC employing TSMC 0.18/spl mu/m process. In Proceedings of the 2004 IEEE International Conference on Semiconductor Electronics, Kuala Lumpur, Malaysia, 7–9 December 2004; p. 5.
  33. Grasso, L.; Sorbello, G.; Ragonese, E.; Palmisano, G. Codesign of differential-drive CMOS rectifier and inductively coupled antenna for RF harvesting. IEEE Trans. Microw. Theory Tech. 2020, 68, 364–375.
  34. Mui, K.M.; Khaw, M.K.; Mohd-Yasin, F. Power Management IC for a Dual-Input-Triple-Output Energy Harvester. Micromachines 2020, 11, 937.
  35. Lu, X.; Wang, P.; Niyato, D.; Kim, D.I.; Han, Z. Wireless networks with rf energy harvesting: A contemporary survey. IEEE Commun. Surv. Tutor. 2015, 17, 757–789.
  36. Guler, U.; Ghovanloo, M. Power Management in Wireless Power-Sipping Devices: A Survey. IEEE Circuits Syst. Mag. 2017, 17, 64–82.
  37. Teh, Y.; Mok, P.K.T. Design of Transformer-Based Boost Converter for High Internal Resistance Energy Harvesting Sources With 21 mV Self-Startup Voltage and 74% Power Efficiency. IEEE J. Solid-State Circuits 2014, 49, 2694–2704.
  38. Teh, Y.; Mohd-Yasin, F.; Choong, F.; Reaz, M.I.; Kordesch, A.V. Design and Analysis of UHF Micropower CMOS DTMOST Rectifiers. IEEE Trans. Circuits Syst. II Express Briefs 2009, 56, 122–126.
  39. Saghlatoon, H.; Honari, M.M.; Mirzavand, R.; Mousavi, P. Substrate integrated waveguide groove sensor antenna for permittivity measurements. In Proceedings of the 12th European Conference on Antennas and Propagation (EuCAP 2018), London, UK, 9–13 April 2018; pp. 1–3.
  40. Honari, M.M.; Mirzavand, R.; Saghlatoon, H.; Mousavi, P. A two-port microstrip sensor antenna for permittivity and loss tangent measurements. In Proceedings of the 2019 13th European Conference on Antennas and Propagation (EuCAP), Krakow, Poland, 31 March–5 April 2019; pp. 1–4.
  41. Saghlatoon, H.; Mirzavand, R.; Honari, M.M.; Mousavi, P. Sensor antenna for dielectric constant measurement of materials in contact with the structure. In Proceedings of the 2019 13th European Conference on Antennas and Propagation (EuCAP), Krakow, Poland, 31 March–5 April 2019; pp. 1–3.
  42. Behdani, M.; Kalateh, M.M.H.; Saghlatoon, H.; Melzer, J.; Mirzavand, R. High-Resolution Dielectric Constant Measurement Using a Sensor Antenna With an Allocated Link for Data Transmission. IEEE Sens. J. 2020, 20, 14827–14835.
  43. Khalid, N.; Mirzavand, R.; Saghlatoon, H.; Honari, M.M.; Mousavi, P. A Three-Port Zero-Power RFID Sensor Architecture for IoT Applications. IEEE Access 2020, 8, 66888–66897.
  44. Khalid, N.; Mirzavand, R.; Saghlatoon, H.; Honari, M.M.; Mousavi, P. Three-Port Zero-Power RFID Flood Sensor for IoT Applications. In Proceedings of the 2020 IEEE Wireless Power Transfer Conference (WPTC), Seoul, Korea, 15–19 November 2020; pp. 61–64.
  45. Khalid, N.; Mirzavand, R.; Saghlatoon, H.; Honari, M.M.; Mousavi, P. A Three-Port Zero-Power RFID Wireless Sensor for IoT Applications. In Proceedings of the 2020 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting (AP-S CNC/USNC-URSI), Montreal, QC, Canada, 5–10 July 2020; pp. 1–2.
  46. Fernández-Salmerón, J.; Rivadeneyra, A.; Martínez-Martí, F.; Capitán-Vallvey, L.F.; Palma, A.J.; Carvajal, M.A. Passive UHF RFID tag with multiple sensing capabilities. Sensors 2015, 15, 26769–26782.
  47. Kapucu, K.; Dehollain, C. A passive UHF RFID system with a low-power capacitive sensor interface. In Proceedings of the 2014 IEEE RFID Technology and Applications Conference (RFID-TA), Tampere, Finland, 8–9 September 2014; pp. 301–305.
  48. Das, S.; Sawyer, D.J.; Diamanti, N.; Annan, A.P.; Iyer, A.K. A strongly miniaturized and inherently matched folded dipole antenna for narrowband applications. IEEE Trans. Antennas Propag. 2019, 68, 3377–3386.
  49. Das, S.; Saghlatoon, H.; Mousavi, P.; Iyer, A.K. A Highly Miniaturized and Inherently Conjugately Matched Folded Dipole-Based RFID Tag Antenna. IEEE Access 2019, 7, 101658–101664.
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