The wireless sensor network node is a micro-embedded system with functions of collecting, transmitting and receiving data. This paper designs the network receiving node based on the wireless communication technology, and adopts the network receiving node of the RF radio receiving chip T5743 to reach the network node data. Short-distance reception, and reduce the bit error rate of the received data to achieve wireless communication of sensor data.

I. Introduction

The wireless sensor network arranges hundreds of sensor nodes in a specific area to form a monitoring network. These nodes are organized efficiently, stably, and correctly through specific protocols, and work together to complete an application task to achieve data acquisition and wireless communication. And the ability to process information. The wireless sensor network node can transmit monitoring data in real time, has the characteristics of rapid construction and convenient deployment, and is not easily restricted by the target environment. Therefore, it has good application in the fields of environmental monitoring, urban traffic management, medical monitoring, warehouse management, and automotive electronics. .

The nodes in the wireless sensor network are usually a micro-embedded system, which has different functions for collecting data, receiving data, processing data, and transmitting data. The processing capability, storage capacity and communication capability are all collected. Data management and collaborative work, so the hardware and software technology of sensor network nodes is the focus of sensor network research. This paper mainly discusses the design of short-distance reception of wireless sensor network node data.

Second, the working principle of the receiving node

The wireless sensor network data receiving node module is mainly composed of the receiving chip T5743 and the MCU microprocessor PIC18F6620. As shown in Figure 1, the transmitting end uses ATMEL's T5754 as the data transmitting chip, which matches the receiving chip T5743 and receives and receives with certain transmission. Frequency and data transfer rates work together. The receiving chip T5743 communicates with the I/O port of the MCU microprocessor PIC18F6620 through the DATA serial bidirectional data line. When the MCU microprocessor receives the data, the DATA_CLK is used as the synchronous clock, and the microprocessor PIC18F6620 sends the command to the receiving chip T5743. Special timing to achieve data reception and processing. The receiving process uses software control to carry out data transmission and realize control of the receiving chip T5743. Before receiving the data, the microprocessor PIC18F6620 writes the program in the MUC into the configuration register of the receiving chip through the DATA line, and performs the receiving chip on the receiving chip. Configuration, and then waiting to receive data; when there is data, it is accessed by the LNA_IN terminal of the receiving chip T5743, amplified by the low noise amplifier and sent to the mixer to be converted into an intermediate frequency; at the intermediate frequency level, the transformed signal is It is amplified and filtered before being sent to the demodulator.

Third, the receiving node chip

ATMEL's T5743 chip is an integrated UHF radio receiver module with a PLL phase-locked loop receiver chip in a SO20 package. The T5743 chip was developed to meet the requirements of low data rate and low cost RF data transmission systems. Its data transmission speed is 1~10kB/s, and the coding mode is Manchester or dual phase mode, which can be used for receiving frequency range. ASK data transmission from 300MHz to 450MHz (433.92MHz and 315MHz); high sensitivity, fully integrated VCO for low power consumption, supply voltage 4.5V~5.5V; single-ended RF output easy to print with antenna or PCB version The antenna is adapted; the operating temperature range is -40 ° C ~ 105 ° C.

The T5743 chip has a bidirectional serial data interface DATA, which allows serial communication with the MCU via the DATA chip to exchange information. It can work at 2 typical frequencies of 433.92MHz and 315MHz, selected by the MODE pin, set high to 433.92MHz, set low to 315MHz, and receive frequency between 1kB and 10kB, which is set by software. The design uses a 1MHz IF to match the front-end SAW filter to achieve high image rejection, based on the new SAW device, achieving 40dB rejection, and can communicate with the microcontroller with a simple bidirectional data line, using separate pins Power management is implemented by a microcontroller.

The RF front end of the T5743 chip is a superheterodyne structure that converts the RF input signal into a 1MHz IF signal. The RF front end consists of a low noise amplifier LNA, a local oscillator LO, a mixer and an RF amplifier. LO is the carrier frequency generated by the PLL phase-locked loop and is used by the mixer. The RF signal is input through the RF input pin LNA-IN. The input impedance is 1000Ω/pF at 433.92MHz. When designing the input network, first consider the noise matching, and properly adjust the component value and the distribution of the printed circuit board to match the input end. The T5743 has the highest sensitivity at high signal-to-noise ratios. In this way, the signal from the RF front-end is filtered by a fully integrated 4th-order IF filter to achieve an application of 334.02MHz with a center frequency of 1 MHz.

The mode of operation of the demodulator in the design is set by the register OPMODE, the logic "L" sets the demodulator to the FSK mode; the logic "H" sets the demodulator to the ASK mode. In the ASK mode, an automatic threshold control circuit is used, which sets the detection reference voltage to an appropriate value for obtaining a good signal-to-noise ratio. This circuit can also effectively suppress any type of in-band noise signal or competing emission if S/N More than 10dB can detect the data signal very well. In the FSK mode, digital signals can be detected if the S/N exceeds 2 dB.

The output signal of the demodulator is filtered by a digital filter and sent to a digital signal processing circuit. The passband of the digital filter matches the characteristics of the data signal. The digital filter consists of a 1st order high pass and a 3rd order low pass filter. The cutoff frequency fcu _ DF of the high pass filter is determined by equation (1). The cutoff frequency of the low-pass filter is determined by the selected baud rate range (BR-Range), BR-Range is set in the OPMODE register, and the BR-Range setting must be adapted to the baud rate.

All timings of the digital circuitry and analog filters of the wireless sensor network receiving node are from one clock. This clock cycle TCLK is obtained from the crystal oscillator via the divider, and the number of divisions is controlled by the logic state of the MODE pin. The frequency of the crystal oscillator is determined by the RF input signal, which also determines the frequency (fLO) of the local oscillator. The operating state of the T5743 chip is set by the two 15-bit RAM registers of OPMODE and LIMIT. The registers can be programmed by the bidirectional DATA port. If the register contents change due to a power loss, this state is represented by an output called a reset flag (RM), in which case the receiving circuit must be reprogrammed. After a power-on reset (POR), the registers are placed in the default mode and the registers are not programmed if the receiver is operating in the default mode. Similarly, if the receiving circuit is not in the reset mode, the corresponding OFF command programming will be initiated; if the receiving circuit is in the reset mode, the corresponding OFF command programming will not be initiated, and the reset flag will still be present on the DATA pin.

Vdisplay is a professional promotional display supplier in China. We offer Customized high quality Clothing Displays,OEM Apparel Display Stands.With More than 20 years in Promotional Display industrial ,We very much experience in design and  manufacturing Clothing Display Racks,MDF Shoe Display Stands,Metal Socks Display Racks,Apparel Display Stands ,Garment Display Stand.

We have been offering a superior range of Shoe Display Racks. These shoe display racks offered by us are widely acclaimed among the patrons for their high storage capacity, strength, attractive designs, tear resistance and elevated durability.

Shoe Display Rack

Shoe Display Rack,Shoes Display Shelves,Shoe Display,Shoe Display Shelves

Vista Display Stand Co., Ltd. , https://www.vistadisplayfixture.com