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RF transmitter module is a small PCB sub-assembly capable of transmitting a radio wave and modulating that wave to carry data. Transmitter modules are usually implemented alongside a microcontroller which will provide data to the module which can be transmitted. RF transmitters are usually subject to regulatory requirements which dictate the maximum allowable transmitter power output, harmonics, and band edge requirements.
There are three types of coding methods commonly used in transmitting module, namely fixed code, learning code and rolling code. Rolling code is the upgrading product of fixed code and learning code. Rolling code is used in all occasions with confidentiality requirements.
Rolling code has the following advantages:
1. Strong security, automatic code change after each launch, other people can not use the "detector" to obtain the address code;
2. When the number of address codes is more than 100000, the probability of "duplicate code" in use is very small;
3. It is easy to code, and the rolling code has the function of learning and storage, and can be coded at the user's site without using a soldering iron. Moreover, a receiver can learn up to 14 different transmitters, which is highly flexible in use;
4. Due to the advantages of coding, the receiver's misoperation is almost zero when the receiver does not receive the local code.
The encoding capacity of the fixed code is only 6561, and the probability of heavy code is very high. The code value can be seen through the solder joint, or obtained by "code detector" in the field of use, so it has no confidentiality. It is mainly used in occasions with low security requirements, and it has been widely used because of its low price.
The main factors affecting the remote distance of RF Module are as follows:
1. Transmitting power: if the transmitting power is high, the distance is far, but the power consumption is large, and the interference is easy to occur;
2. Receiving sensitivity: the receiver's receiving sensitivity is improved, and the remote control distance is increased, but it is easy to be disturbed and cause misoperation or out of control;
3. Antenna: linear antennas are used, and they are parallel to each other. The remote control distance is far, but it takes up a large space. The remote control distance can be increased by lengthening and straightening the antenna in use;
4. Height: the higher the antenna, the farther the remote control distance, but limited by objective conditions;
5. Blocking: the currently used wireless remote control uses the UHF frequency band specified by the state, and its propagation characteristics are similar to that of light, with linear propagation and small diffraction. If there is wall blocking between the transmitter and receiver, the remote control distance will be greatly reduced. If the wall is reinforced concrete, the influence will be more serious due to the absorption of the conductor to the radio wave.
