Methods to increase the transmission distance of wireless modules

成都亿佰特

Methods to increase the transmission distance of wireless modules [Copy link]

With the development of wireless data transmission, the application of wireless modules is becoming more and more extensive. Wireless modules are widely used in vehicle monitoring, remote control, telemetry, small wireless networks, wireless meter reading, access control systems, community paging, industrial data acquisition systems, wireless tags, identity recognition, contactless RF smart cards, small wireless data terminals, security and fire protection systems, wireless remote control systems, biological signal acquisition, hydrological and meteorological monitoring, robot control, wireless 232 data communication, wireless 485/422 data communication, digital audio, digital image transmission and other fields.

The transmission distance of the wireless module is mainly affected by factors such as power, receiving sensitivity, and antenna. This article mainly describes how to increase the transmission distance of the wireless module from these three aspects.

1. Transmit power

Emissive Power is the strength of the RF signal emitted by the wireless module. Theoretically, the greater the RF signal strength, the longer the transmission distance, that is, a high-power wireless module has a longer transmission distance than a low-power wireless module.

2. Receive sensitivity

Receiver Sensitivity refers to the minimum signal level that a receiver can detect under the condition of a given receiver demodulator and the required signal-to-noise ratio. The receiving sensitivity of wireless transmission is similar to the hearing of people when they communicate and talk. Improving the receiving sensitivity of the signal can make wireless products have a stronger ability to capture weak signals. In this way, as the transmission distance increases, the received signal becomes weaker, and highly sensitive wireless products can still receive data, maintain a stable connection, and greatly increase the transmission distance. That is, the lower the receiving sensitivity, the longer the transmission distance of the wireless module.

The formula for receiving sensitivity is as follows:

S=-174+NF+10lgB+10lgSNR

Where: NF is the noise factor, B is the signal bandwidth, and SNR is the demodulation signal-to-noise ratio. The larger the bandwidth, the greater the system noise factor, the greater the sensitivity, and the worse the receiving performance. This requires that when designing a receiver, the impact of the system bandwidth and noise factor on sensitivity must be considered.

The receiving sensitivity of the wireless module is very important, especially in the low-power transmission system, where every dB is important, especially the "6dB rule": that is, increasing or decreasing by 6dB means doubling or reducing the power by half. For example, when the transmitting energy of the transmitter is 100mW or 20dBm, if the receiving sensitivity is -83dBm at 11Mbps, the theoretical unobstructed line of sight of the transmission is 15km, and when the receiving sensitivity is -77dBm, the theoretical unobstructed line of sight of the transmission is only half of 15km (7.5km), or equivalent to a 1/4 reduction in the transmitting energy, which is equivalent to 25mW, 14dBm. Therefore, improving the receiving sensitivity of the receiving end in the wireless module transmission system is equivalent to increasing the transmitting energy of the transmitting end, while increasing the transmission distance of the wireless module.

3. Antenna

An antenna is a converter that converts guided waves propagating on a transmission line into electromagnetic waves propagating in an unbounded medium, or vice versa. Generally, antennas are reversible, that is, the same antenna can be used as both a transmitting antenna and a receiving antenna, and the basic characteristic parameters of the same antenna as a transmitter or a receiver are the same.

From the perspective of the antenna's theoretical parameters, the antenna's input impedance and antenna gain determine the antenna's performance and the transmission distance of the wireless module. From the perspective of the antenna's input impedance, the antenna is generally made into a standard 50 ohm, and the impedance of the wireless module is also a standard 50 ohm, so that the antenna and the wireless module are fully matched, ensuring that there is no loss of transmission signals, thereby ensuring the distance of the wireless module. From the perspective of the antenna's gain, the total transmitted energy is equal to the sum of the transmit power (dBm) and the antenna gain (dBi). The greater the antenna gain, the greater the total transmitted energy and the longer the wireless module transmission distance.

From the actual test of the antenna, since the actual environment on site cannot be absolutely flat, such as hills, buildings, and trees, which affect the propagation of radio waves to varying degrees and in different ways. Therefore, before the project is implemented, it is necessary to conduct on-site radio wave propagation and receiving field strength tests (accurate to dBm) in order to determine the power, antenna type, installation height and other parameters of the equipment according to the on-site environment and work requirements, so that the uplink and downlink signals can achieve sufficient anti-interference capabilities, and then effective and reliable wireless data transmission can be achieved.

However, in actual testing, it is impossible to be absolutely flat and without obstructions. Therefore, the transmission distance of the wireless module is affected by many factors and is not absolute.

Jacktang

Theoretically, the unobstructed line-of-sight distance for transmission is 15km, but in reality it is much different.