1. Overview of RFID frequency application
With the development of the current society, science and technology has been improving. The application of RFID radio frequency identification technology is also becoming more and more extensive, and the issue of frequency allocation is getting more and more valued. Because radio frequency identification systems generate and radiate electromagnetic waves, these systems are cleverly classified as radio equipment, and radio frequency identification systems cannot disrupt or weaken other radio services during operation. In particular, it should be ensured that the RFID radio frequency identification system will not interfere with nearby wireless electromagnetic waves and mobile radio services.
In the choice of the working frequency in the radio frequency identification system, the influence of some other factors should also be considered. Can not affect or interfere with other radio services. In our country, a certain frequency range is reserved for industrial, scientific and medical applications. The use of radio waves is also uniformly divided according to frequency bands.
Each frequency also has its own advantages and disadvantages. The transmission distance below 135KHz is as short as about 10 cm, and the communication speed is slow. This frequency band is open in most countries and will not involve issues such as license applications for laws and regulations. Therefore, it is the most widely used. Mainly used in pets, access control and anti-theft tracking, etc. The most widely used radio services in this frequency range are aviation and maritime radio services. Timing signal and frequency standard service and military radio service. The frequency range of 13.553~13.567MHz is in the middle of the shortwave range. According to the propagation characteristics of electromagnetic waves in this frequency band, it is allowed to penetrate the connection day and night in black and white. In this frequency range, there are different types of radio service organizations. Such as news and telecommunications services and other institutions. In China, UHF (ultra high frequency) frequency bands allocated to RFID are mainly concentrated in two frequency ranges. One is 840-960MHZ (specifically 840-845MHz and 920-925MHz, the transmission power is 2W), and the other is 433MHZ (different countries have different UHF allocations). The 840-960MHZ frequency band and the 433MHZ frequency band belong to the UHF range. Let's analyze and compare the advantages and disadvantages between the two.
2. The advantages and disadvantages of 433MHZ frequency
Initially, the frequency range of 430.050 ~ 440.000 MHz was allocated to amateur radio services worldwide. Some radio enthusiasts will use this frequency band for language and data transmission. But now the 433.050~434.790MHz band has been largely occupied by various industrial, scientific, and medical (ISM-Industrial-Scientific-Medical) applications. In addition to the backscatter radio frequency identification system, there are also small telephones, telemetry transmitters, wireless headsets, unregistered short-range low-power wireless walkie-talkies, keyless access systems, and many other applications that fill this frequency band. Class cards, etc.
433MHZ is in the UHF (30-1000MHZ) range. The common feature of UHF is that it basically cannot be reflected by the ionosphere. The propagation methods that play a major role in this frequency band are space wave propagation within line-of-sight, as well as tropospheric scattering and ionospheric scattering. Compared with the high frequency band, the advantage of this frequency band is that a small-sized antenna can be used for low-capacity systems. Obviously, this feature is particularly suitable for mobile communications. Tropospheric scattering replaces the radio-relay system in some occasions, because it can hop hundreds of kilometers without a relay station, and it can also have a large capacity (multi-channel transmission), which is impossible at low frequencies.
433MHZ is at the low end of UHF. Compared with the high end of 860-960MHZ (usual UHF frequency), because the low end can be reflected by the ionosphere, it is prone to interference. But at the same time, because it is at the low end of the ultra-high frequency, it also has the characteristics of some high-frequency waves. The communication is simple, easy to implement, and low in cost. It can realize long-distance communication with a small power and much smaller antenna, which is its advantage. These advantages make it more widely used. In addition, its UHF communication has high stability, large capacity, and strong transmission capabilities, making its advantages more prominent.
3. The advantages and disadvantages of UHF
Since the end of 1997, the frequency range of 868 ~ 870MHz has allowed short-distance equipment in Europe, thereby in Europe Postal and Telecom Conferences, 43 Member States of the Telecommunications Conference can also be used for RF identification systems. Some Far East countries are also considering this frequency range to be used for short-range devices. Outside Europe (USA and Australia), frequency ranges 888 ~ 889MHz and 902 to 928MHz have been used and used in reverse scattering RF identification system. At present, China's radio frequency identification system typically UHF frequency range is 860-960 MHz, specified as 840 to 845MHz and 920 to 925 MHz.
The frequency range radio wave is substantially not reflected, and the quality of transmission information is good, and the stability is high. In the radio relay system, a higher frequency is employed, although the propagation loss increases, high antenna gain can compensate for this part of loss. Therefore, this band is suitable, and the capacity can also be increased, and more ways can be passed. But at the same time, the frequency band is relatively complex than 433MHz, and the cost is higher, which is an unfavorable side.