Bluetooth
At present, the positioning accuracy of this technology is very poor. Bluetooth 5.0 and previous versions use RSSI signal strength to locate the distance, and the accuracy is difficult to achieve above the meter level. If you want to locate the angle, you need a directional antenna. There are two methods. There are always two Bluetooth modules. The directional antennas are facing different directions. The angle of the signal source is calculated according to the ratio of the signal strength received by the antennas. The other method is to install a rotating mechanism on the antenna, which is similar to the radar rotation scanning method to find the strongest signal. direction. It is also possible to improve the positioning accuracy based on the networking of multiple devices, but the practicality is really not very good. Therefore, the current positioning of this method is not ideal, and there is no follow-up product.
After the Bluetooth 5.1 technology matures, there will be opportunities. Bluetooth 5.1 supports antenna arrays. There is a phase difference when the antenna array receives RF signals. According to the phase difference, the distance and angle of the signal source can be calculated. From the newly announced technical standard of Bluetooth 5.1, the positioning accuracy can reach CM level, and the angular accuracy can reach within 5 degrees. At present, the Bluetooth SIG has announced the Bluetooth 5.1 standard, but no products have been launched yet. According to the progress of semiconductor devices, the market is expected to launch mature mass-produced Bluetooth 5.1 chips or modules in two years, which is quite exciting. However, from the point of view of its principle, Bluetooth 5.1 will not be perfect. There is a problem of multipath reflection. In the case of small indoor space or surrounding pillars, metal and other electromagnetic wave emitters, the signal of the signal source will be multipath reflected. , Finally, the signals received by the antenna come from multiple directions, which will cause positioning errors.
Understand the implementation
principle
WIFI
Detailed tutorial on ESP32-based WiFi-RSSI positioning and distance
measurement through ESP866 RSSI value
UWB
Xiaomi UWB One Finger Connect Technology (Video)
[UWB Positioning] - Simple Experience of DWM1000 Module Debugging - 1
[UWB Positioning] - Simple Experience of DWM1000 Module Debugging - 2
[UWB Positioning] - Simple Experience of DWM1000 Module Debugging - 3
DW1000 Learning Road ( 1) -------- Use DW1000 to send
data
DW1000 UWB Transceiver Chip Data Sheet Free Download
- DW1000 is a fully integrated single-chip ultra-wideband (UWB) low-power low-cost transceiver IC, compliant with IEEE802.15.4-2011. It can be used in two-way ranging or time-of-flight positioning systems to locate assets with an accuracy of 10 cm. It also supports data transfer at rates up to 6.8
Mbps- DW1000 is a fully integrated low-power single-chip CMOS RF transceiver IC that complies with the IEEE802.15.4-2011 UWB standard. The DW1000 consists of an analog front end (containing a receiver and a transmitter) and a digital back end (interfacing with an off-chip host processor). The TX/RX switch is used to connect a receiver or transmitter to the antenna port. Temperature and voltage monitors are available on-chip. The receiver consists of an RF front-end that amplifies the received signal in a low-noise amplifier and down-converts it directly to baseband. The receiver is optimized for wideband, linearity and noise figure. This enables each supported IEEE802.15.4-2011
UWB channel to be down-converted with minimal additional noise and distortion. The baseband signal is demodulated and the resulting received data is provided to the host controller via SPI. Transmit pulse trains are generated by applying digitally encoded transmit data to an analog pulse generator. The burst is up-converted by a double-balanced mixer to a synthesizer-generated carrier and focused on one of the allowed UWB channels of IEEE802.15.4-2011. The modulated RF waveform is amplified before being transmitted from an external antenna. The integrated circuit has on-chip one-time programmable (OTP) memory. This memory can be used to store calibration data such as Tx power level, crystal initial frequency error adjustment, and range accuracy adjustment. These adjustment values can be automatically retrieved when needed. See Section 5.14 for details. Always-on (AON) memory is used to retain DW1000 configuration data in the lowest power operating state when the on-chip voltage regulator is disabled. This data will be uploaded and downloaded automatically. DW1000
AON memory usage is configurable. The DW1000 clock scheme is based on three main circuits: crystal oscillator, clock PLL and RF PLL. The on-chip oscillator is designed to operate at 38.4 MHz using an external crystal. An external 38.4 MHz clock signal can be used in place of the crystal if a suitably stable clock is available elsewhere in the user's system. This 38.4 MHz clock is used as the reference clock input for the two on-chip PLLs. The clock PLL (denoted CLKPLL) generates the clocks required for digital back-end processing signals. The RF phase-locked loop generates the down-conversion local oscillator (LO) for the receive chain and the up-conversion local oscillator (LO) for the transmit chain. Provides an internal 13
kHz oscillator for sleep state. The host interface includes a slave-only SPI for device communication and configuration. A number of MAC functions are implemented, including CRC generation, CRC checking, and received frame filtering.
Introduction to DWM1000 Module
- Based on the DW1000 chip developed by DecaWave, it is an ultra-wideband wireless transceiver chip compatible with IEEE802.15.4-2011 protocol
- It is mainly used in the development of real-time location system (RTLS) and wireless sensor network, including industries such as agriculture, building control, factory automation, medical treatment, security and warehousing.
Introduction to UWB DWM1000 Module
- The DWM1000 module is an ultra-wideband transceiver module designed based on Decawave's DW1000 chip. The module integrates the antenna and all RF circuits, power management and clock circuits. This module can be used in TWR or TDOA positioning system to locate the target, its accuracy can be less than 10cm; and the module supports data transmission rate up to 6.8Mbps
- Technical data
- Conforms to IEEE802.15.4-2011 ultra-wideband standard;
- Supports 4 RF bands from 3.5GHz to 6.5GHz;
Programmable output power of the transmitter;
Fully coherent receiver, maximizing the use distance and high accuracy;
Its design complies with FCC (Federal Communications Commission) & ETSI (European Telecommunications Standards Institute) UWB spectrum standards;
Power supply is 2.8 V~3.6V;
Low power consumption;
Data transmission rate 110kbps, 850kbps, 6.8Mbps three modes;
The maximum data packet length is 1023 bytes, which meets the application requirements of high data exchange;
Integrated MAC support function
Supports two-way ranging and TDOA positioning;
Host interface is SPI;
23mmx13mmx2.9mm 24-pin side castellation package.