A phase-locked loop (PLL) secondary frequency conversion wireless transceiver circuit that complies with the national standard for industrial remote control

This article introduces a frequency synthesis (I2C control) secondary frequency conversion FSK narrowband transceiver module NT230 and NR230 suitable for industrial remote control (especially for electric hoist remote control). This module is specially developed and produced for industrial remote controls. It uses advanced phase-locked loop (PLL) secondary frequency conversion narrowband frequency shift keying (FSK) technology and SMD components. It is small in size, stable and reliable in operation, and has strong anti-interference. The frequency stability reaches 5×10-6 (5PPM, -20℃~50℃), and the sensitivity is 1μV (12dB SINAD). In normal environments, the remote control distance reaches 80 ~100m. Comply with the national standard for industrial remote controls. 1. Working principle The NT230 transmitter module uses a specially imported high-stability crystal oscillator (not a surface acoustic wave resonator). The 230MHz radio frequency FSK signal it outputs is extremely stable, and the transmit current is very small. At 5V/8mA, the output is 110dBμv (75Ω load). The block diagram of the NR230 receiving module is shown in Figure 1. The modulated coded signal from the antenna is high-amplified and mixed and sent to the second mixing circuit composed of LA3372 for detection. After the original signal is output, it is restored to the encoded signal for decoding through low-pass and amplification shaping circuits. The local oscillator signal of the mixer is provided by a voltage-controlled oscillator (VCO) controlled by a phase-locked loop (PLL). The 4MHz crystal oscillator and CPU provide standard frequency (I2C control). It is worth mentioning that the mixer here uses a new SMD component circuit in an SSOP package, with a built-in balanced mixer and mid-amplifier. The mixing efficiency is extremely high and The output spectrum is clean, and the second intermediate frequency filter uses a five-terminal filter dedicated to communication, with a selectivity of 50dB at ±25kHz. 2. Application examples This transceiver module can be widely used in industrial wireless control, crane remote control, wireless data transmission, and remote control. Car garage door, etc. The transmitting and receiving application circuits of the PT2262/2272 codec chip are shown in Figure 2 and Figure 3 respectively. In the figure, the power supply voltage Vcc = 6V. It should be noted that PT2262 generally uses a resistor to determine its oscillation frequency. , this may cause the oscillation frequency to deviate. In this application example, a 4MHz crystal oscillator is divided by CD4060 to provide an accurate frequency. In the circuit of Figure 2, PT2262 is an encoding chip with 8 address codes and 4 address codes. Data code, a total of 12 control terminals. Each control terminal has three states: "0", "1" and floating. In this example, floating is not used, so a pull-down resistor is used to ground. Therefore, the address code has a total of 2 (of 8). Power) is 256. The clock signal is input from the pin of PT2262. The pins,, and pins are the 4-bit data code input terminals. The encoded data signal output by the PT2262 pin is directly sent to the transmitting module NT230. Perform narrowband frequency modulation. If you want to further improve the radio frequency index and reduce the side frequency, you need to add a low-pass circuit composed of an integrated operational amplifier between the output terminal of PT2262 and the input terminal of NT230. Figure 3 shows the receiving decoding circuit. Under the premise that the address codes of PT2272 and encoder PT2262 are completely consistent, the decoder will identify the encoded signal sent from the receiving head NR230. Once the pulse waveform is completely consistent, the decoding will be successful at the corresponding output end of PT2272 (D0~D3). Outputs a high level to drive the subsequent circuit. At the same time, the potential at its pin VT changes from low to high, and is maintained until the end of the encoding signal. When used for more than 4 control terminals, the receiving and decoding can be expanded with CD4514. The specific circuit is shown in Figure 4. CD4514 is a 4- to 16-terminal decoding chip that can expand 4 control signals to up to 16 channels. The transmitting end can be expanded by using a diode matrix or using a PLD chip to form a 16-4 encoder. Once the PT2272 has a correct decoding signal, the high level output by the VT terminal is inverted by IC2 A and IC2 B and then added to the pin-th inhibit terminal of CD4514. Here, IC2 A and IC2 B are connected in parallel to improve the driving capability. The high level output by IC2C is added to the pin enable end of CD4514, so that CD4514 remains valid only when there is a VT signal. During this period, when the input terminals D1~D4 of CD4514 receive the data signal sent from PT2272, one bit of the corresponding output terminal will change to high level. This high level will pass through the drive circuit composed of resistors and transistors, causing the corresponding The relay operates.

 　This article introduces a frequency synthesis (I2C control) secondary frequency conversion FSK narrowband transceiver module NT230 and NR230 suitable for industrial remote control (especially for electric hoist remote control). This module is specially developed and produced for industrial remote controls. It uses advanced phase-locked loop (PLL) secondary frequency conversion narrowband frequency shift keying (FSK) technology and SMD components. It is small in size, stable and reliable in operation, and has strong anti-interference. The frequency stability reaches 5×10-6 (5PPM, -20℃~50℃), and the sensitivity is 1μV (12dB SINAD). In normal environments, the remote control distance reaches 80 ~100m. Comply with the national standard for industrial remote controls. 1. Working principle The NT230 transmitter module uses a specially imported high-stability crystal oscillator (not a surface acoustic wave resonator). The 230MHz radio frequency FSK signal it outputs is extremely stable, and the transmit current is very small. At 5V/8mA, the output is 110dBμv (75Ω load). The block diagram of the NR230 receiving module is shown in Figure 1. The modulated coded signal from the antenna is high-amplified and mixed and sent to the second mixing circuit composed of LA3372 for detection. After the original signal is output, it is restored to the encoded signal for decoding through low-pass and amplification shaping circuits. The local oscillator signal of the mixer is provided by a voltage-controlled oscillator (VCO) controlled by a phase-locked loop (PLL). 4MHz crystal oscillator and CPU provide standard frequency (I2C control). It is worth mentioning that the mixer here adopts