What is FHSS in RFID

Frequency-Hopping Spread Spectrum (FHSS) is one of the most typical spread spectrum working methods in communication technology. It widens the bandwidth of the information many times by means of encoding and modulation, and performs frequency shift keying (FSK) modulation with the spread spectrum code sequence, so that the frequency of the carrier is continuously hopped. The transmitted information and the combination of these spreading codes are selected and controlled, and constantly jump during transmission. At the receiving end, the original information can be reStored correctly only through demodulation because the same local generator as the sending end generates the exact same spreading code for despreading.

Advantage:

1. Confidentiality. The pseudo-randomness of the frequency hopping pattern and the key amount of the frequency hopping pattern make the frequency hopping system confidential. Even the frequency hopping communication of analog voice, as long as the enemy does not know the frequency hopping pattern used, it has a certain ability to keep secret. When the key of the frequency hopping pattern is large enough, it has the ability to resist interception.

2. Anti-jamming. Since the carrier frequency is hopping, it has the ability to resist single-frequency and partial bandwidth interference. When the number of hopping frequencies is large enough and the frequency hopping bandwidth is wide enough, its anti-interference ability is very strong.

3. Anti-multipath fading. Using the fast hopping of the carrier frequency, it has the function of frequency diversity, so that the system has the ability to resist multipath fading. The condition is that the frequency interval of the hopping is larger than the relevant bandwidth.

4. Utilizing the orthogonality of the frequency hopping pattern, a frequency hopping code division multiple access system can be formed to share spectrum resources and have the ability to withstand overload.

5. The frequency hopping system is an instantaneous narrowband system, which can communicate with existing narrowband systems. That is, when the frequency hopping system is at a certain fixed carrier frequency, it can establish communication with the existing fixed frequency narrowband system. In addition, the frequency hopping system is applicable to both analog and digital sources.

6. The frequency hopping system has no obvious near-far effect. This is because when the high-power signal only produces the near-far effect on a certain frequency, when the carrier frequency jumps to another frequency, it is no longer affected by it. This point makes the frequency hopping system easy to be applied and developed in mobile communication.