ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific, and medical (ISM) purposes, excluding applications in telecommunications. These bands were established to accommodate various RF energy uses such as RF heating, microwave ovens, and medical diathermy machines, which can emit powerful signals capable of causing electromagnetic interference. To mitigate potential disruptions to radio communications using the same frequencies, these devices are restricted to specific bands where they must tolerate any interference generated by ISM applications. Users operating within these bands have no regulatory protection against interference from ISM device operations.
Historical Context and Usage Expansion
The ISM bands were first established at the International Telecommunications Conference of the ITU in Atlantic City in 1947, with the American delegation proposing several bands, including the now commonplace 2.4 GHz band, primarily for microwave heating. Over time, however, the fastest-growing use of these bands has shifted towards short-range, low-power wireless communications systems. These systems often utilize ISM frequencies because they can operate without a government license, provided they tolerate interference issues inherent to these bands. Examples of devices using ISM frequencies include cordless phones, Bluetooth devices, near-field communication (NFC) devices, garage door openers, baby monitors, and wireless computer networks (Wi-Fi).
Regulatory Framework and Frequency Allocations
The ITU Radio Regulations define the ISM bands, with individual countries potentially having variations due to national radio regulations. Communication devices operating in these bands must be designed to tolerate interference from ISM equipment. While unlicensed operations are typically permitted in these bands, licensed use is generally low due to the high likelihood of harmful interference. In the United States, the FCC governs uses of the ISM bands under Part 18 rules, with Part 15 covering unlicensed communication devices that may share ISM frequencies. European standards for short-range devices operating in ISM bands are developed by ETSI, and usage is regulated by national spectrum regulation authorities.
Common Applications and Frequency Bands
ISM bands are utilized for a wide range of applications beyond telecommunications, including induction heating, microwave heating, and medical treatments like diathermy. Recently, radar systems have also begun operating within these bands, particularly the 2.4 GHz band, due to the availability of inexpensive wireless ICs. Everyday uses of ISM bands include Wi-Fi, Bluetooth, Zigbee, RFID, and NFC systems. Notably, the 2.4 GHz band is commonly used for Wi-Fi and Bluetooth communications, while the 13.56 MHz band is used by many RFID and NFC systems.
Conclusion
ISM radio bands play a crucial role in supporting a variety of industrial, scientific, and medical applications, as well as enabling short-range, low-power wireless communications. Their designation and regulation facilitate the coexistence of numerous technologies and devices across different sectors, despite the potential for electromagnetic interference.
Citations: [1] https://en.wikipedia.org/wiki/ISM_radio_band [2] https://www.militaryaerospace.com/directory/blog/14059677/what-are-the-ism-bands-and-what-are-they-used-for [3] https://tektelic.com/what-it-is/ism-radio-bands/ [4] https://www.pcmag.com/encyclopedia/term/ism-band [5] https://resources.altium.com/p/ism-bands-around-world [6] https://www.everythingrf.com/community/ism-frequency-bands [7] https://www.tesswave.com/what-are-the-ism-frequency-bands/ [8] https://www.analog.com/en/resources/glossary/ism.html [9] https://www.edn.com/ism-bands-and-frequencies-comparisons-and-case-studies/