Design of wireless remote control transmitting and receiving circuit

    　Circuit principle: Although OOK modulation has poor performance, its circuit is simple, easy to implement, and stable in operation. Therefore, it has been widely used. Such circuits are almost always used in car and motorcycle alarms, warehouse gates, and home security systems. Early transmitters mostly used LC oscillators, and the frequency drift was more serious. The emergence of SAW devices solved this problem. Its frequency stability is roughly the same as that of crystal oscillators, and its base frequency can reach hundreds of megahertz or even thousands of megahertz. No frequency multiplication is required, and the circuit is extremely simple compared to crystal oscillators. The following two circuits are common transmitter circuits. Due to the use of SAW devices, the circuit works very stably. Even if the antenna, SAW or other parts of the circuit are grasped by hand, the transmission frequency will not drift. The transmission power of Figure 2 is higher. It can reach more than 200 meters. The receiver can use super-regenerative circuits or super-heterodyne circuits. Super-regenerative circuits are low in cost and have low power consumption of about 100uA. The sensitivity of a well-adjusted super-regenerative circuit is similar to that of a super-heterodyne receiver with a high-level amplifier, an oscillator, a mixer, and two intermediate amplifiers. However, the working stability and selectivity of the super regenerative circuit are relatively poor, which reduces the anti-interference ability. The figure below shows a typical super regenerative receiving circuit. 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. The sensitivity of a well-adjusted super regenerative circuit is similar to that of a super heterodyne receiver with a high-level amplifier, an oscillator, a mixer, and two intermediate amplifiers. However, the working stability and selectivity of the super regenerative circuit are relatively poor, which reduces the anti-interference ability.