homodynmätningar

Homodyne measurements are a technique used in various fields, particularly in optics and radio frequency engineering, to measure the amplitude and phase of a signal. The core principle involves mixing the unknown signal with a locally generated reference signal that has the same frequency and phase. This process, known as heterodyning if the frequencies differ or homodyning if they are identical, results in a down-converted signal at zero frequency (DC).

In a homodyne setup, the signal and the reference are combined using a mixer, such as a beam splitter in optics or a multiplier circuit in electronics. The output of the mixer is proportional to the product of the amplitudes of the two input signals and the cosine of their phase difference. By analyzing this DC output, one can extract information about the original signal's amplitude and phase relative to the reference.

The advantage of homodyne detection is its sensitivity, as it can detect very weak signals. It also provides a direct measurement of both amplitude and phase, which is crucial for applications like coherent communication systems, interferometry, and precise measurements of physical quantities. The phase information is preserved because the mixing occurs at the same frequency.