【文章內(nèi)容簡介】 frequency oscillations change the instantaneous frequency, the interference caused by the parasitic amplitude limiter (or with a limited role in the proportion of increase frequency discriminator) removed. Therefore, regardless of the margin from the launch frequency signal from the received signal power or the analysis of the demodulator, the FM systems are better than the antijamming performance of the system AM. 2. Occupied bandwidth FM systems as a result of broadband frequency occupied bandwidth, FM is only suitable for over FM band (30Hz30GHz) use. For the medium and longwave band (MW:1000100m, longwave 101 km), while the use of AM or SSB Modulation. 3. Transmitter power FM transmitter system launched by the instantaneous FM carrier frequency changes with the modulation signal for the FM wavewave, and its average power equal to the maximum power。 and AM transmitter system is the AM signal to launch, when the MAM = 1 when the largest transmission power equal to average power (carrier power) 4 times. If the AM transmitter and FM transmitter at the end of the introduction of the same type of power tubes, according to the maximum power is estimated that the FM transmitter emits power AM transmitter is fired 4 times the average power. 4. AM transmitter power amplifier for the demanding pipe Launched wave amplitude is the amplitude modulation signal with the change, which the reverse of the zoom control a higher voltage, should adopt a higher breakdown voltage of the tube, or easily puncture the tube. And FM transmitter is the amplitude in the state, the tube can not easily be puncture. 5. Comparison of production costs FM series production of its testing device is a plex process, so the need for testing is equipped with fully mechanized Senate, shielding room of the production of expensive testing equipment, testing equipment directly determine the stability of performance, but also the needs of professional skilled workers. AM production devices are relatively easy to many, so the threshold for the production of FM products is much higher than the production of AM products, therefore the difference between the cost of production more than doubled. Above both the performance and cost, the users of the two cases must be understood that the current widely used form of the AM transceiver ponents, because of its higher cost and at the same time more convenient for production, so request is not too high on some occasions, the use of this model, this paper also focused on the introduction of this module. Wireless Transmitter Module DF data transmitter frequency for 315M, the use of SAW resonator frequency stabilization, high frequency stability, when the environmental temperature between 25 ~ +85 degree changes, the frequency drift of only 3ppm / 176。c Particularly suitable for a collection of multiple wireless re mote control and data transmission system. SAW resonator frequency stability after the crystal, and general LC oscillator frequency stability and consistency of poor, even with highquality finetuning capacitance, temperature changes and vibration has been transferred it is difficult to ensure good frequency point migration will occur. DF does not have code to launch module integrated circuits, and an increase of a data modulation transistor Q1, such a structure can be