Contents
What is coherent detection?
Coherent detection allows us to detect arbitrary amplitude and phase information of the received light field by interfering the received signal with a local oscillator.
What is the purpose of a phase locked loop?
A phase-locked loop (PLL) is an electronic circuit with a voltage or voltage-driven oscillator that constantly adjusts to match the frequency of an input signal. PLLs are used to generate, stabilize, modulate, demodulate, filter or recover a signal from a “noisy” communications channel where data has been interrupted.
What is coherent detection in analog communication?
Coherent detection allows us to detect arbitrary amplitude and phase information of the received light field by interfering the received signal with a local oscillator. From: Optical Fiber Telecommunications (Sixth Edition), 2013.
How is the Costas loop similar to the phase locked loop?
Costas Loop is similar to the Phase Locked Loop in the sense that it locks onto the frequency and phase of its input signal and produce an output signal that is identical in frequency and phase to the input signal, but it is inherently immune to a 180-degree phase shift of the input signal (i.e. BPSK modulated carrier).
What kind of circuit is Costas BPSK detector?
A 2GHz carrier recovery Costas Loop based BPSK detector is designed using CMOS 0.18µm technology. The designed BPSK detector consists of single to differential conversion circuit, phase/frequency detector, Voltage Controlled Oscillator, differential to single conversion circuit, first order loop filter and a third multiplier.
How is a phase locked loop used in BPSK?
At first glance, one may suggest using a Phase Locked Loop (PLL) for this purpose, but a PLL would lock onto every 180-degree phase shift introduced to the carrier at every data transition and the recovered local carrier would subsequently contain such phase shifts; thereby, making it impossible to recover the baseband signal.
When did John Costas invent the Costas loop?
Costas loop. A Costas loop is a phase-locked loop (PLL) based circuit which is used for carrier frequency recovery from suppressed-carrier modulation signals (e.g. double-sideband suppressed carrier signals) and phase modulation signals (e.g. BPSK, QPSK). It was invented by John P. Costas at General Electric in the 1950s.