Frequency shift keying (FSK) is a popular digital modulation technique for data transmission. Some common applications of FSK modulation include both wired and wireless data transmission as well as infrared remote controls for consumer electronic equipment. FSK demodulation can be either coherent or noncoherent. Coherent detection always demands carrier and bit synchronization, typically achieved using phase-locked loops (PLLs).
Click here to download the full size of the above Circuit.
PLLs are very noise-sensitive and normally call for a trimming adjustment inside the loop filter. FSK noncoherent demodulation can be implemented with two bandpass filters and two envelope detectors. Bit synchronization may be required as well. In narrowband FSK transmission systems, bandpass filters must have a very high quality factor, making implementation more complex. This idea presents a noncoherent, narrowband FSK receiver that eliminates the drawbacks mentioned above. Figure 1 shows the FSK demodulation circuitry in which neither PLLs nor high-quality-factor bandpass filters are used. With this high-frequency (HF) demodulation circuit, no trimming adjustments are necessary. L1, L2, C4, and C7 form two resonant circuits, implementing an input filter whose passband is centered at 10 MHz. A differential high-frequency amplifier amplifies the 10-MHz signal. IC1 and IC2 combine to make an automatic gain-control (AGC) circuit. The amplified signal is then converted into a digital waveform by a wideband comparator, IC3. The resulting digital signal clocks a 4-bit counter (IC4). Oscillator IC5 clears the counter. IC6A, the D-type flip-flop, latches the counter`s most significant bit at the rising edge of the oscillator signal OSC_OUT. Since the oscillator circuit generates a 50% digital waveform duty cycle and the two FSK frequencies are: The calculated OSC_OUT frequency also can be divided or multiplied by a power of two....
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
characters left: