“Digital signal OOK/ASK wireless transceiver circuit has simple circuit structure and reliable operation, and can be easily embedded in Electronic equipment and systems to form a point-to-point, point-to-multipoint wireless data transmission channel.
Author: Huang Zhiwei, Zhu Weihua, Zou Qihong
The designed digital signal OOK/ASK wireless transceiver circuit is composed of TX6000 single-chip transmitter chip and RX6000 single-chip receiver chip, working in 916.50MHz frequency band; it has OOK/ASK modulation and demodulation ability, strong anti-interference ability, suitable for industrial control Application; SAW frequency synthesis technology, good frequency stability; receiving sensitivity up to -98dBm, transmit output power 0.75mW; data rate up to 115.2Kbps; low operating voltage (2.7 ~ 3.5V); low power consumption, receiving current 1.8 mA, the current when transmitting is 12mA, the receiving standby state and the transmitting standby state are only 0.5μA; it can be used in digital narrowband, spread spectrum radio link, handheld data terminal, wireless local area network, computer communication, data acquisition system, telemetry remote control and other systems.
2 Digital signal OOK/ASK wireless transmitting circuit
The digital signal OOK/ASK wireless transmitting circuit is shown in Figure 1 and Figure 2, and the circuit component parameters are listed in Table 1. The circuit takes TX6000 as the core. TX6000 is a monolithic transmitter chip launched by RF Monolithics, SM-20H package, the chip contains: SAW resonator, SAW filter, RF amplifier, modulation and bias control circuits. The impedance range of the RF output terminal (RFIO) is 35~75Ω, and an external antenna series matching coil and a parallel ESD protection coil are connected. The SAW resonator and amplifier 1 (TXA1) form an oscillator. The digital signal to be transmitted is input through the TXMOD terminal, amplified by the transmitting amplifier 2 after modulation, and filtered by the SAW filter and output. The transmitter has 2 working modes: ASK transmission, OOK transmission, low power consumption (sleep). Mode control is done by CNTRL0 and CNTRL1. Set CNTRL1 to “high level” and CNTRL0 to “low level”, the chip works in ASK transmit mode; set both CNTRL1 and CNTRL0 to “low level”, the chip works in low power (sleep) mode. In the circuit, T/S is the transmit mode/sleep mode control signal.
Table 2 Component parameters of digital signal OOK/ASK receiving circuit
Modulation type OOKOOKASK
3 Digital signal OOK/ASK wireless receiving circuit
The digital signal OOK/ASK wireless receiving circuit is shown in Figure 3 and Figure 4, and the parameter values of the circuit components are listed in Table 2. The circuit is based on RX6000. RX6000 is a monolithic receiver chip launched by RF Monolithics, which contains: SAW filter, SAW delay line, RF amplifier, detector, data limiter, low-pass filter and other circuits. The RF output end RFIO impedance range is 35~75Ω, and an external antenna series matching coil and a parallel ESD protection coil are connected. The RF signal reaches the RF amplifier RFA1 through the SAW filter. The RFA1 gain is selectable between 35dB and 5dB. The output of RFA1 goes to the SAW delay line, which has a standard 0.5μs delay. The second stage RF amplifier RFA2 has a gain of 51dB. The detector output drives the gyratory filter, which provides a 3-pole, 0.05-degree equal-ripple low-pass filter response. The output of the filter is amplified by the baseband amplifier to the BBOUT terminal. When the receiver’s RF amplifier operates at 50% duty cycle, the signal change at BBOUT is about 10mV/dB, and the peak-to-peak signal level reaches 685mV. The output signal of BBOUT is coupled to the CMPIN input through a series capacitor. When the receiver is set to low power (sleep) mode, the output impedance at BBOUT is in a high impedance state.
The input signal of the CMPIN end is added to two data limiters, and the analog signal from BBOUT is converted into a data stream. The data limiter DS1 is a capacitively coupled comparator with an adjustable threshold. The limiter level of the comparator is from 0 to 90mV, set by the resistor between RFEF and THLD1. The threshold value is zero, and the sensitivity is the best. The number of data limits DS2 limits the trigger point can be set between RRE and THLD2 resistance between 1 ~ 120mV, usually set to 60mV. DS1 and DS2 output digital signals at the RXDATA terminal through the AND gate. The output of the peak detector also provides an AGC reset signal to the AGC control circuit through the AGC comparator. The AGC control circuit ensures the dynamic operating range of the receiver.
The receiver has 2 working modes: receive and low power consumption (sleep). Controlled by CNTR1 and CNTR0: when CNTR1 and CNTR0 are high, the receiver works in receive mode; when CNTR1 and CNTR0 are low, the receiver works in low power (sleep) mode. R/S in the circuit is the control signal of receiving mode/sleep mode.
Digital signal OOK/ASK wireless transceiver circuit has simple circuit structure and reliable operation, and can be easily embedded in electronic equipment and systems to form a point-to-point, point-to-multipoint wireless data transmission channel.
The problem that should be paid attention to in use is: when the transceiver circuit is placed in the same system, the transmitting circuit needs to be placed in transmit mode and the receiving circuit in sleep mode before sending data; the transition time of the transmit circuit from sleep mode to transmit mode is at least 1ms; data of any length can be sent; the transmitting circuit should be put into sleep mode after sending. Before receiving data, put the receiving circuit in the receiving mode, and put the transmitting circuit in the sleep mode; the conversion time of the receiving circuit from the sleep mode to the receiving mode is at least 1ms; the data received by the receiving circuit can be directly sent to the serial interface of the microcontroller or After level conversion, it is sent to the computer. The circuit does not transmit and receive data while in sleep mode. The data transfer rate is up to 115.2Kbps.