The Research And Design Of RF Transceiver

Communication plays an important part of life not only in our daily life but also in social development and progress.Generally speaking, those who sent a letter in the mail and who, in any way for the transmission of information, we call it communication .The equipment using for transmit the message is known as the communication system. End of the 19th century with the rapid development of information, the means of communication using the electrical signal for the carrier is known as the modern communications systems, information from the source of input transducer, sending equipment, channel, receive equipment, output transducer, the composition of output transducer .The transmitter and receiver is the core of modern communication systems devices, in order to make the base-band signal in an effective and reliable channel to set up the transmission.wireless sending and receiving system use electromagnetic waves for the equipment between the different space. It has a tradition of contact great advantages to be applied to the military and in all aspects of life. The system is generally divided into two parts and to senging part and receiving part. Produced by firing high-frequency oscillator signals, base-band signal will be added to the carrier signal, and finally launch into space by the antenna. Received by the receiving antenna, high-frequency amplification, Ultra regenerative detection circuit composed.This paper is a detailed study of the AM transceiver's operating principle, features, as well as the steps. Sending module using OOK modulation (ON-OFF modulation), that is,turning on or turning off the transmitter modulation is the extremism example of AM modulation. Ultra regenerative receiver modules used to receive circuit in order to receive the message.1.the design of RF transceiver modulesThrough the switch to open and close, the 0 and 1 to generate baseband signals, R315A generate a 315M Hz carrier signal, when the switch is turned off, the entire circuit connected to a base-band signal, baseband signal modulation carrier signal, resulting in signal modulation, modulation signal from the antenna to radiation from space.When the switch opens, the circuit does not work.Receiving module is the classic Ultra regenerative 315MHz reception circuit, through its antenna receive the signal,the signal coming in through the band-pass filter which filter the noise and unwanted signal,and pass into amplifier.The output signal come into detecting circuit, then the signal go through the low-pass filter for filtering.After filtering the high-frequency noise, the signal go into the LM358.After a two-stage amplification, the final output of the SC2272 to feet14 (foot data entry) The demodulator is the square, SC2272 signal to determine whether it is effective, if effective, output pin will set high level.2. the RF transceiver moduleThe OOK modulation module , in spite of poor performance, however, the circuit simply and easily to make and the stability of the work. Early use of the transmitter is LC oscillator, and frequency drift is more serious. SAW devices solve this problem, the frequency stability as well as the crystal, and the fundamental frequency of up to several gigahertz, or even Fast. No octave, compared with the crystal circuit,it is extremely simple. The use of SAW devices, the circuit is very stable, even if touch the antenna, or other parts of the circuit,there will not be frequency drift.In this design, the sending module work at 315M, using SAW resonator for the high frequency stabilization,when the surrounding temperature at -25 ~ +85 degrees , the frequency drift of only 3ppm /°. Particularly suitable for multiple wireless remote control and the resumption of a data transmission system. SAW resonator frequency stability weak than the crystal, and ordinary LC oscillator has poor performance of frequency stability and consistency, even with high-quality capacitor, changes in temperature and vibration have been difficult to ensure migration occurs when a frequency has been set.Ultra regenerative receiveing modules is been used in receive circuit. Ultra regenerative detection circuit is actually a batch of high-frequency oscillator oscillation control, use the collpitts oscillator for high-frequency oscillator, the oscillation's frequencyis the same as the frequency of transmitter. The oscillation is intermittent in the oscillation frequency of the oscillation process, which in turn controls the high-frequency oscillator and intermittent vibration. The intermittent oscillation frequency is decided by the circuit parameters (generally a few hundred to a hundred kHz). If select the low-frequency ,we will have the better anti-interference performance of the circuit, but receive a lower sensitivity, on the contrary, select the high-frequency, receiver sensitivity is better, but the anti-jamming performance variation. Ultra regenerative detection circuit has very high gain. 3.the prospect of RF transceiver modulesAs the wireless communications with the convenience of distance f and the limitations of its physical environment, and other advantages. Wireless communication has been widespread concern in all aspects, has been greatly developed in the 20th century, the hardware technology have got great advances, the emergence of a variety of electronic components, makes wireless communications equipment go into people's daily life, the wireless communications will improve its technology to make the progress of our lives. Particularly, we will enter an era of 3G wireless communications will give our lives more profound changes we have made the link more quickly and easily.This design which has its problem about the transmitting distance and responging signal can be improved, and improve the stability of the circuit, as well as various functions.