One article to understand the ISM frequency band
The ISM (industrial production, scientific rationality, diagnosis and treatment) frequency band is a specific wireless communication frequency band defined by the International Telecommunication Union (ITU) "Radio Regulations". This frequency band is a frequency band set aside for other main uses of radio frequency outside the telecommunication network. Therefore, although the ISM frequency band is theoretically suitable for the main purpose of the telecommunication network, the communication products using the ISM frequency band must be able to bear the influence from other frequencies and electromagnetics, such as heating from microwave ovens, radio frequency heating, and other possible influences. Effects of machinery and equipment that create interference signals (EMI). Although the International Telecommunication Union has identified specific frequency bands, the ISM frequency bands expressly stipulated by various countries are not uniform.
The original purpose of the ISM band was not for communications, but many short-range, low-power, license-free (or license-free, fault-tolerant) communication systems now operate in this frequency band. In addition to communications, the most common main uses of the ISM band are electromagnetic induction heating for industrial production and household use, microwave heating for industrial production and household use, and medical radio frequency such as diathermy, continuous hyperthermia therapy, and radio frequency/microwave ablation. and microwave heating. In addition, because the ISM frequency band can be used at will, and there are some special wireless network integrated circuit chips for frequencies in this frequency band, some recently developed radar detection systems also use the ISM frequency band, especially in the 2.4GH ISM frequency band. signal jammer
The most common daily main uses of the ISM frequency band are low-power and short-distance communication such as WiFi, mobile phone Bluetooth, Zigbee, wireless landline, RFID and NFC. In foreign countries, most people are familiar with the ISM band because most WiFi and Bluetooth communications and the 5GHz WiFi system that has become more and more popular recently use the ISM band. In addition, there are many common RFID and NFC systems that use the 13.56MHz frequency in the 13.553MHz~13.567MHz ISM band, and many bank credit cards, security connections, staff authentication and wireless payment systems also use this technology.
In addition, many new smart home electronic products and hobbyist electronic products use Zigbee technology operating in the 915MHz and 2.4 GHz ISM frequency bands to complete power consumption and short-range communication between devices. In the next few years, 60GHz WiFi (ie WiGig, also known as IEEE 802.11ad) operating in the 60GHz ISM band will likely be popularized for its very high-volume machine-to-device communication capabilities. The main uses of this process are, for example, Ultra HD, 4k video streaming and fast wireless data transfer between devices.
Compared with the past, there have been many more deployment plans and communication platforms for ISM frequency bands in recent years. Some of these reasons are likely to be the increasingly potential Internet of Things (IoT) and Industry 4.0 applications, which may use low-power and short-range device-type communications without customer involvement. Examples of such new technology applications include Thread, Z-wave, LoRa and NB-IoT (Industrial Internet of Things). Although the ISM frequency band may also be used for satellite communication in the future, at this stage, not all CubeSats, nanoSATs or other small and medium-sized communication satellites use the ISM frequency band.
The key frequency categories in the ISM band are as follows:
1. Frequency 6.78MHz
This frequency range is 6.765-6.795MHz, which belongs to the medium and short wave frequency. This frequency range has been assigned by the International Telecommunication Union as the ISM frequency band in the world, and will be more and more used by the RFID system.
This frequency band was originally set for short-wave communication. According to the dispersal characteristics of radio waves in this frequency band, short-wave communication can only achieve a small effect distance during the day, more than a few hundred kilometers, and can spread across the interior at night. The operators of this frequency category are different types of wireless communication services, such as radio communication services, wireless communication weather services, and wireless communication airline services.
2. Frequency 13.56MHz
This frequency range is 13.553 ~ 13.567MHz, which is in the medium and short wave frequency band, all of which are ISM frequency bands. In this frequency range, in addition to inductively coupled RFID systems, there are other ISM applications, such as remote control systems, long-distance manipulation of physical model systems, demonstration wireless communication systems and pagers.
This frequency band was also originally set up for short-wave communications. According to the characteristics of radio waves in this frequency band, network signals allow communication across the mainland during the day and night. The operators of this frequency category are different types of wireless communication service organizations, such as news reporting organizations and telecommunications network organizations.
3. Frequency 27.125MHz
This frequency range is 26.957-27.283MHz. In addition to the inductively coupled RFID system, ISM applications in this frequency range also include medical electric heating physiotherapy instruments, industrial-grade high-frequency welding equipment and pagers. When assembling an industrial-grade 27MHz RFID system, it is necessary to pay attention to all the high-frequency welding equipment that may exist in the surrounding area. The high-frequency welding equipment causes a high magnetic field strength, which will obviously affect the RFID system at the same frequency in work. In addition, when planning the 27MHz RFID system in the hospital outpatient department, attention should be paid to the possible influence of the electric heating physiotherapy instrument.
4. Frequency 40.680MHz
This frequency range is 40.660 ~ 40.700MHz, which is in the middle and low end of the VHF frequency band. In this frequency range, the primary application of ISM is monitoring and remote control.
In this frequency range, the effect distance of inductively coupled RFID technology is small, and the light wavelength of this frequency 7.5m is not suitable for building small and low-cost reverse transmission rfid tags, so there is currently no radio frequency in this frequency band. In the work of the identification technology system, it belongs to the frequency band that is not suitable for the radio frequency identification technology system.
5. Frequency 433.920MHz
This frequency range is 430.050 ~ 434.790MHz, which is allocated to amateur radio service applications on a global scale. This frequency band is located in the middle of the amateur radio frequency band, and is already occupied by various ISM applications at this stage. This frequency range belongs to the UHF band, and when radio waves hit buildings or other obstructions, significant losses and reflections will occur.
This frequency band is suitable for reverse-direction transmission RFID systems. In addition, it can also be used for small and medium-sized telephones, monitoring transmitters, wireless Bluetooth headsets, short-range low-power radios, and vehicle wireless network intermediate locking devices. However, in this frequency band, because of the use of many, the mutual influence of ISM is relatively large.
6. Frequency 869.0MHz
This frequency range is 868-870MHz, which is in the UHF band. Since 1997, this frequency band has been used in Europe for short-range devices, so it can also be used as an RFID frequency. Some Far East countries are also considering allowing the use of this frequency range for short-range machinery.
7. Frequency 915.0MHz
In foreign countries and Australia, the frequency ranges of 888-889MHz and 902-928MHz are already available, and are applied by the reverse direction transmission RFID system. This frequency range has not yet been used by ISM in Europe. The adjacent frequency range is occupied by radiotelephones manufactured to CT1 and CT2 specifications.
8. Frequency 2.45GHz
The standard of this ISM frequency is 2.400-2.483 5GHz, which belongs to the microwave heating stock band and is also in the UHF band, which partially overlaps with the frequency range of amateur radio amateurs and wireless communication precision positioning service applications. The radio waves in this frequency band are quasi-light sources, and the buildings and obstacles are all very good vertical surfaces, and the radio waves lose a lot of data when transmitting data.
This frequency range is suitable for reverse transmission RFID systems. In addition, typical ISM applications in this frequency band include mobile phone Bluetooth and 802.11 protocol wifi network.
9. Frequency 5.8GHz
The standard of this ISM frequency is 5.725 to 5.875 GHz, which belongs to the microwave heating stock band, which partially overlaps with the frequency range of amateur radio amateurs and wireless communication precision positioning service applications.
Typical ISM applications in this frequency range are reverse-direction transmissive RFID systems, which can be used in highway RFID systems and also in gate opening and closing (in malls or department stores) systems.
10. Frequency 24.125GHz
The standard of this ISM frequency is 24.00-24.25GHz, which belongs to the microwave heating stock band, which partially overlaps with the frequency range of amateur radio amateurs, wireless communication precision positioning services and satellite services for earth environment communication.
Within this frequency range, there is no radio frequency identification technology system in operation at this stage. This stock band is mainly used in mobile signal sensors, and is also used for wireless communication classification systems for transmitting data.
11. Use of other frequencies
The frequency range within 135 kHz is not reserved as an Industrial Manufacturing, Sound and Medical (ISM) frequency, and this frequency band is used in many applications for various wireless communication services. Except for the ISM frequency, RFID can be used in all frequency ranges within 135kHz, because this frequency band can work with a relatively large magnetic induction intensity, especially for inductively coupled RFID systems.
According to the dispersion characteristics of radio waves in this frequency band, wireless communication services occupying this frequency range can achieve a distance of more than 1,000 km. Within this frequency range, typical wireless communication services are airline navigation bar wireless communication services, ocean navigation navigation bar wireless communication services, on-time data signal services, frequency specification services, and defense wireless communication services. A radio frequency identification technology system operating at this frequency will invalidate the wireless communication clock within 500 meters of the card writer. Possibility of RFID system possession.
