Microwave phase shifters are devices that alter the phase of the electromagnetic oscillations at the output of a microwave transmission line, with respect to the phase of the oscillations at the input of the line. The phase of a transmission line can be shifted by increasing the length/time of the transmission line or by altering the wavelength.
In microwave solutions, phase shifters are passive microwave devices that change the phase angle of an RF signal. RF waves can combine to strengthen or weaken a signal, depending on if the waves are identical or different. Identical frequencies will strengthen a signal, whereas opposing ones will weaken it. Phase shifters change the angle of an RF signal so that it doesn’t interfere with the wrong signals. This technology maintains strong performance by providing low insertion loss.
We can understand this concept better by considering noise-cancelling headphones, which use some phase shifting principles. In an audio application, instead of adjusting RF and microwave energy, the shift involves the phase of an audio wave in relationship to another wave. Noise-canceling headphones reduce noise by inserting a sound wave that is 180 degrees out of phase with the surrounding noise. The new sound wave has been shifted to cancel out the first wave, thus reducing the noise you hear.
This noise-cancelling example illustrates an extreme result that we do not typically see in microwave applications. Generally, microwave phase shifters only need to change minor increments of a wavelength to achieve the desired performance results.
Phase shifters are used in a variety of applications, including phase modulators, frequency up-converters, testing instruments and phased array antennas. Radiall designs and manufactures analog phase shifters for microwave components and coaxial phase shifters for space qualified components.
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