High frequency remote control circuit design circuit diagram

Although OOK modulation has poor performance, its circuit is simple and easy to implement and its operation is stable, so it has been widely used. It is almost without exception used in automobile and motorcycle alarms, warehouse doors, and home security systems. circuit.

Early transmitters mostly used LC oscillators, which caused serious frequency drift. The emergence of surface acoustic devices has solved this problem. Its frequency stability is roughly the same as that of crystal oscillators, and its fundamental frequency can reach hundreds of megahertz or even gigahertz. There is no need for frequency multiplication, and the circuit is extremely simple compared to a crystal oscillator. The following two circuits are common transmitter circuits. Due to the use of acoustic surface devices, the circuit works very stably. Even if the antenna, acoustic surface or other parts of the circuit are held by hand, the transmitting frequency will not drift. Compared with Figure 1, the transmit power of Figure 2 is larger. It can reach more than 200 meters.

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The receiver can use a super regenerative circuit or a super heterodyne circuit. The super regenerative circuit has low cost and low power consumption of about 100uA. It has well-adjusted super regenerative circuit sensitivity and one-level high amplification, one-level oscillation, one-level mixing and two A mid-level superheterodyne receiver is almost the same. However, the super-regenerative circuit has poor operating stability and poor selectivity, thus reducing its anti-interference ability. The figure below shows a typical super regenerative receiver circuit.

The sensitivity and selectivity of superheterodyne circuits can be very good. The monolithic integrated circuit launched by the American company Micrel can complete reception and demodulation. Its MICRF002 is an improved version of MICRF001. Compared with MICRF001, it has lower power consumption. And has a power shutdown control terminal. MICRF002 has stable performance and is very easy to use. Compared with super reproduction circuits, the disadvantage is that the cost is relatively high (RMB35 yuan). The following is its pin arrangement and recommended circuit.

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ICRF002 uses ceramic resonators, and by using different resonators, the receiving frequency can cover 300-440MHz. MICRF002 has two working modes: scanning mode and fixed mode. The scan mode acceptance bandwidth can reach several hundred KHz. This mode is mainly used with LC oscillation transmitters because the frequency drift of LC transmitters is large. In scan mode, the data communication rate is 2.5KBytes per second. The bandwidth of the fixed mode is only tens of KHz. This mode is used with transmitters that use crystal oscillator frequency stabilization, and the data rate can reach 10KBytes per second. The working mode selection is achieved through pin 16 (SWEN) of MICRF002. In addition, use the wake-up function to wake up the decoder or CPU to minimize power consumption.　

MICRF002 is a complete single-chip superheterodyne receiving circuit, which basically realizes "direct data output" after "antenna input". The receiving distance is generally 200 meters.