What is Costas loop?

Costas loop is an analog circuit that can regenerate the carrier and its phase from the input signal without any or with a minimum carrier content. It is a loop with phase locking that relies on the frequency content of the side signals. The phase locking loop maintains the phase relationship of the generated sinus signal to the reference signal and uses an oscillator of a controlled voltage that generates a sinusoid signal with a frequency and phase that can be controlled by steering voltage and phase comparative circuit. When the steering voltage or correction voltage increases, the instant phase conductor of the controlled output of the oscillator may increase due to the reference signal. A typical input into the Costas loop is the so -called double side band suppressed by the carrier signal. The use of multiplier and low passage filters, voltage -controlled voltage output and incoming double side zone carrier are mixed so that the double side zone support signal is shifted in the frequency spectrum to the basic band, usually sound, SP SPEktra. It is commonly known as demodulation of the message from the modulated carrier. The Digital Costas loop described by multiplier and synchronous detection function performed by digital signal processors.

In addition, the double side bandwage is a special type of signal because it does not have a carrier. The simplest form of modulation is the modulation of the amplitude with a double side belt, with the carrier modified so that its envelope is proportionally in proportion to the message. Simple circuits can demodulate this modulation of double side belt amplitude, a carrier with two side tapes. A simple diode detector fixes the carrier and transmits the result to a low passport S and the result is a message.

If the carrier is suppressed, the Costas loop reconstructs the carrier using a function called regeneration of the supporting phase. When starting, an oscillator controlled by a free -running voltage is not yet locked to the supporting frequency of the incoming double side band aftera pushed carrier. It should be noted that the Costas loop actually calculates the frequency of the carrier based on the positions of the side zone in the frequency spectrum. Using a low-pass filter in-phase and quadrature, or 90 degrees, the version output of the controller controlled voltage, the low-bicycle product demodulated side bands creates correction signals for synchronizing the voltage oscillator to the center of the side band. Meanwhile, the message is extracted as long as the oscillator controlled voltage is locked on the suppressed carrier.