ZigBee through the wall

ZigBee through the wall

Common ZigBee modules work in the 2.4G universal free frequency band. In recent years, ZigBee alliance has also launched ZigBee products working at 868mhz, but limited by the free frequency band, they have not been applied on a large scale.

We take the common TI CC2530 ZigBee module as an example to explore the through wall distance of ZigBee.

The maximum transmitting power of CC2530 chip is + 4.5dbm, the receiving sensitivity is - 96dbm and the link is 100.5dbm. Take inverted-F antenna as an example:

During the distance test of inverted-F antenna, the transmitting distance is greatly related to the direction of the space where the module's sky is located. During the indoor test, the RSSI value received by the antenna varies greatly in different directions, and the maximum energy difference is 20-30dbm. During the distance test of serpentine antenna, the transmitting distance is greatly related to the direction of the space where the module's sky is located. During the indoor test, the antenna is located in different directions, The difference between the received RSSI values is not as large as that of the inverted-F antenna, and the directivity is not strong.

We choose serpentine antenna for wall penetration test:

The serpentine antenna is about 8 meters away from the room without obstruction. The received RSSI value is about - 65 DBM. It passes through a 20 cm thick brick wall and the received signal is about 86 DBM. The ZigBee module of CC2530 transmits a similar brick wall. The communication distance is about 10 meters. With interference, the distance is not about 10 meters. Therefore, there are many rooms in the room. To achieve full room coverage, it is necessary to select a high-power ZigBee module to cover all rooms, Or add ZigBee relay at the appropriate location.

Project case: when installing ZigBee intelligent system in a villa in Shenzhen, ZigBee modules with PA are selected, and the ZigBee relay adopts open position switches. The whole villa (three floors in total) is fully covered, and all smart products can be normally controlled on mobile phones.