Recently, the concept of passive IoT has begun to get hot. Internationally, a startup called Wiliot announced it had received a $200 million Series C funding led by SoftBank Vision Fund. The company's most typical product is a Bluetooth sensor tag that does not require a battery and is powered by surrounding radio waves based on Bluetooth protocols. In China, innovative companies such as Shenzhen Meikai Information Technology Co., Ltd. are also trying to make breakthroughs in this field. , a new field, is gathering more attention.
1 What is passive IoT
Passive IoT As the name suggests, it means that IoT devices can work normally without power (battery or wires). This sounds incredible, and even violates the principle of physics energy conservation .
But in fact, the passive IoT device works not because it does not use electricity, but because it can capture energy from the surrounding links to maintain the normal operation of the device.
There is a lot of energy around us, such as light, 4G, 5G signals, etc. The passive Internet of Things is the idea of making these microenergy. Passive IoT can also be implemented in a variety of ways.
The first type is achieved by collecting radio wave energy in surrounding links. , for example, 4G signals, 5G signals, wifi signals, Bluetooth signals, etc., each radio signal is an energy transmission.
This is also the most popular way for passive IoT, because in order to operate normally, an IoT device needs to not only obtain working energy, but also transmit data information, and the transmission of signals also depends on radio signals. Therefore, using radio methods can both obtain energy and transmit signals, making the system very simple, and at the same time, the cost, size, etc. can be very low.
The second common type is to collect solar power supply. solar power supply can obtain a lot of electricity, but the system is complex and costly. It is suitable for some scenarios, but it is obviously not applicable for large-scale and low-cost Internet of Things application scenarios.
The third type is pressurized power generation. generates current by changing the deformation of the material through mechanical force. There are also some more suitable scenarios for this method, such as switches, remote controls, etc. But this method that requires direct hands-on is obviously not suitable in most scenarios.
So, in this article, we focus on the passive IoT method of radio signals.
2 Why do you need a passive Internet of Things? What is the meaning of it
Why is the concept of passive Internet of Things so attractive? We can see the picture below.
In the previous PPTs that introduced the prospects of the Internet of Things market, there are only three layers above, namely high-speed Internet of Things (such as 5G, LTE Cat.4, etc.), medium-speed Internet of Things (LTE Cat.1, eMTC, etc.), and low-speed Internet of Things (NB-IoT, LoRa, etc.), these are all active Internet of Things technologies.
The number of low-speed Internet of Things devices can reach 10 billion. Now, with the addition of passive Internet of Things, the number of IoT device connections can reach 100 billion. I believe that in various PPTs in the future, we will often see this picture.
Of course, the significance of passive IoT is not just to expand the potential market of IoT devices by an order of magnitude, because the characteristics of passive IoT devices are becoming increasingly sought after by the market.
First, it means no need for batteries. On the one hand, it means a reduction in cost. In the active Internet of Things, the cost of the battery itself and the replacement cost of the battery are also relatively high. Passive IoT tags can achieve very low costs. For example, the current general-purpose UHF RFID tag can reach a level of 2-3 cents (RMB). is unimaginable in the active Internet of Things.
On the other hand, it is energy-saving and environmentally friendly. The production of batteries uses a large number of metals and chemicals. With the increasingly strict environmental protection policies, passive Internet of Things is a trend.
Second, the tag can be very lightweight, is free from the constraints of the battery, and the passive Internet of Things tag can be used as a patch-based product form, with higher application flexibility.
3 Technical feasibility of passive Internet of Things
Regarding the technical feasibility of passive Internet of Things, the author has also communicated with senior industry insiders.
From a technical perspective, passive Internet of Things is not a new concept. RFID is a very mature passive Internet of Things technology, and the annual shipments are at the level of tens of billions. The passive Internet of Things solution for
radio waves is mainly divided into two links: absorbs radio power supply links and transmits signals to be received by the receiver.
First talk about the energy acquisition link from radio signals. The most critical device in this link is the antenna. The antenna's electromagnetic ability to obtain electromagnetics is mainly divided into two categories according to the differences in technical types.
, the first type is inductive coupled to , the shape of the antenna is a coil, and the transmission of electromagnetic energy is completed in the induction field area (like a stable field). Therefore, the working distance of will be very close. For example, the working distance of NFC (a type of high-frequency RFID) is less than 10cm, and the low-frequency RFID (125kHz-132kHz) and high-frequency RFID (13.56MHz) antennas adopt this method.
coil type RFID antenna diagram
The second type is a microwave radiation system. The transmission of electromagnetic energy is completed in the far-field area (radiation field). Therefore, the types of antennas are mainly dipole antennas and microstrip antennas, and the far-field radiation antennas are usually resonant.
(a) Tag dipole antenna
(b) Reader flat panel microstrip antenna
Common ultra-high frequency RFID antenna representative, source: "Internet of Things UHF RFID Technology, Products and Applications"
UHF RFID, Bluetooth, WiF and other communication technologies passive IoT solutions can only have a longer working distance (mainly the distance from power withdrawal).
Let’s talk about signal transmission, when electronic components obtain normal working current, the distance and method of transmitting signals are no different from those of active Internet of Things.
Therefore, in the passive IoT solution, the biggest technical difficulty of is how to obtain the working current. Because the density of electromagnetic energy decreases a lot as the distance becomes longer, the distance to obtain energy is the working distance of the passive IoT solution.
In actual applications, passive IoT solutions will try to use components with very low working current. If the working frequency is not very high, but the working current of the components is relatively high, you can store a certain amount of power by adding a capacitor, and then work through the capacitor discharge.
is obvious. The Bluetooth or Wifi signal in the weak links around cannot achieve energy supply. Generally, a separate energy source is required. In the RFID system, the reader and writer provide the energy source. Bluetooth or Wifi scheme also requires a separate base station or similar device.
So, the typical workflow of passive IoT system is:
4 Commercial feasibility of passive IoT
In addition to technical feasibility, what is the commercial feasibility of passive IoT?
Currently, RFID is a very mature passive Internet of Things technology. It has large-scale applications in both low-frequency, high-frequency and ultra-high-frequency. The largest number of them is ultra-high-frequency RFID . The global shipment of its tags has reached nearly 20 billion every year, and the Chinese market is also the most important region for RFID.
In passive RFID scheme, reader and writer not only provides energy, but also is responsible for receiving signals transmitted by tags. Therefore, passive RFID requires additional reader and writer cost.
However, NFC is one of the variables, because NFC has become the standard configuration for smartphones at present, Therefore, in NFC solutions, many application scenarios only need to consider the tag cost, rather than the reader and writer cost.
Therefore, NFC is more suitable in many consumer-oriented scenarios, such as anti-counterfeiting and traceability for valuable items such as high-end liquor, jewelry, etc., and some lock or access control scenarios. NFC has been widely used, but the fatal weakness of NFC is its short working distance.
The biggest advantage of using small wireless technologies such as Bluetooth and WiFi to create passive IoT solutions is that smartphones are implanted, and their working distance is also farther than NFC.
However, the passive IoT solution of Bluetooth and WiFi requires a separate energy signal source, and the efficiency of Bluetooth and WiFi to transmit energy is relatively low, and the distance to obtain the working current is short, which means that the overall cost of this solution will not be too low.
Of course, compared with the active solution, its tag cost is extremely low and its size is small, which can be a better alternative in some scenarios concentrated in tag nodes. However, in the scenario where nodes are scattered, the active method is more appropriate.
5 Why is RFID the best passive IoT technology
Currently, RFID has tens of billions of shipments every year, and the cumulative volume has already reached 100 billion, and it is not impossible to achieve a 100 billion yuan annual volume in the future. The reason why
RFID technology is so popular is mainly because it is a very good passive IoT technology.
First, from a technical perspective, the biggest difficulty of the passive IoT solution is how to obtain electrical energy from electromagnetic wave . People use a set of test data: fixed transmit antenna output power and receiving antenna (RFID tag antenna) size to record the reading distance at different frequencies, and obtain the working distance diagram at different frequencies as shown in the figure below.
Working distance diagram at different frequencies, source: "Internet of Things UHF RFID Technology, Products and Applications"
It can be found that the 840M-960MHz working in UHF RFID is the frequency band with the highest energy transmission efficiency and the farthest working distance, and and the 2.4G frequency band working in Bluetooth, WiFi and other technologies have much shorter energy transmission distance. Wiliot's Bluetooth passive tags currently have a working distance of 3m, while the UHF RFID can be about 10 meters away.
Second, it is the maturity of the industry. The UHF RFID tags on the market are very small in size and light in size. This is because after decades of development, the UHF RFID tag production link has already had a very complete industrial chain. Whether it is the production of etching antennas, binding machines, and then to composite machine , these process flows have been very complete. The cost and size of the
tag have almost reached the extreme, and the players who are later can only imitate the production process and are difficult to surpass. The application of
RFID technology is becoming more and more extensive, and the industry is growing rapidly, and it has become a backbone force in the IoT circle. This year, the 16th International Internet of Things Exhibition and Shenzhen Station of IOTE 2021 will be held at the Shenzhen Futian Convention and Exhibition Center from October 23 to 25.
At this exhibition, many well-known companies that have deeply rooted in the RFID industry were invited to participate in the exhibition, including Fudan Microelectronics , Yuanwanggu , Youboxun, Cainiao Network , Xinda , Sichuang Medical Hui , Yingpinjie, STMicroelectronics , Sato, Zebra, Aili , Yongyi, Aoyi, Chuanqi, Hardesheng, Cheng, Handhall, Dongda Integration, Yuning, Quanshunhong, Ande, Shengbang, Honglu, Ousi IoT, Rodanbell, Huicheng Xintong, Yuanmingjie, Chili, Boside, Yuehe, Yingda Juli, Dongxinyuanxin, Zhongkong Ruidiyou, Guoxin, Anzhibo, Baodian, Deshi, Detong, Xingeshan, Xinjinglu, Xiangcheng Communications, Guoju, Jiaoguan, Pinguan, Xianshi, Shangmi, Xinye, Ruichi, Rongzhixing, Xinlian Chuangzhan, Changda, Lanchang, Sibito, Jin Ruiming, Jianhe, Xinfenju, Harshen Intelligent Materials, Bowei, Oupu, Deju, Huashi Jingcheng, Siyuanchuang, Zhilian, Sco, Beidouxingtong, New Leopard, Lixin , Rongrui, Aida, Kailuwei, Tengcai, Xincheng, Huasheng Intelligent, Moorjia, Liandian, Wanquan, Toshiba and other companies in the entire industrial chain!
Reference materials for this article:
"Internet of Things UHF RFID Technology, Products and Applications", author: Ganquan
"Can this startup that has been favored by SoftBank/Qualcomm/Samsung subvert the traditional RFID market? 》, author: Zhao Xiaofei, Internet of Things think tank
