Homemade Simple Frequency Synthesis Source ----- FREQUENCY GENERATOR

Homemade simple frequency synthesis signal source, Frequency Generator Keywords: CD4040, frequency generator circuit diagram Author: Zheng Maoxin In order to obtain a frequency stable square wave signal, the author tried a simple frequency synthesized source with a frequency range of 1 Hz to 3 MHz. Since the selected crystal temperature coefficient is about 0.2 ppm / ° C, the output frequency is extremely stable. When the temperature of ± 10 ° C is changed, the output frequency does not exceed 2 ppm. The circuit of the signal source is shown in the drawings. The signal source is composed of three integrated circuits. The CD4060 and 8.192 MHz crystal constitute a reference oscillator, and the 1 foot 8192 is divided into 1 kHz, as the reference frequency of the phase-locked loop. Integrated phase-locked loop circuit CD4046 constitutes a standard frequency synthesis circuit. Its internal voltage controlled oscillator generally operating frequency is 1.2MHz, and it is overclocked in this circuit. 6, the received capacitance is reduced to 6.2pf, in actual applications, can be operated to 3.2MHz when the power supply voltage is 12V. Of course, when the operating frequency is high, the waveform is slightly poor, which is not big in amateur relationship. The CD4040 is the 12 binary counter, which is used as any divider of the L ~ 3000, and then uses the zero pulse to divide the divided output. Since the CD4040 is a serial counter, the triggers are flipped without synchronization. When the operating frequency is high, the inclusion interference of the clever end is large, so it is filtered out of the ground, and the R5 value should be reduced. To 620Ω, it can make the divider work normally. The frequency division coefficient of the circuit is the sum of the numbers corresponding to each closing switch. By combining the 12 switches, the divided integer between the L ~ 4095 can be obtained. Use the CD4040 as a divider, compared to the divider circuit composed of the preset decimal subtraction counter, the division is large, but the disadvantage is that the adjustment frequency needs to be converted, it is not as intuitive, which is not necessary to adjust frequently. Operation, or suitable. The 4th foot of the CD4046 can output a square wave signal of 1 kHz to 3 MHz. At the same time, the L000 divider is formed by a CD4518 and a piece of CD4017, and the output signal of the CD4046 4 foot output signal can be obtained from 1 Hz to 3 kHz, and it has the same accuracy. The CD4017 is used to obtain a square wave signal having a duty cycle of 50%, while the output of the CD4518 is a pulse having a duty ratio of 20%. If a CD4518 divider is inserted in the middle, a square wave signal as low as 0.01 Hz can be obtained. In addition, an emitter follower can be accessed at the output to increase the output driving capability. With the 5V regulator tube of the CD4046 (15), the output can be converted to a TTL level.