It uses the JFET’s properties to act as variable resistor. The same approach has been used to employ a variable resistor-based circuit to make the phase shifter frequency independent. Moreover, they produce results that are not 100% accurate for the range of frequency defined. Those two designs that we’ve described so far are all costly techniques and require special function ICs for their operation. This is a frequency independent phase shifter using frequency to voltage converter . Figure 1 shows the diagram of this implementation. Compensation for the variation in the frequency is achieved using the programmable capacitor. The phase shift can be varied using the programmable resistor. That design approach is based on a simple op amp phase shifter with a programmable floating resistor and a programmable capacitor. Some researchers have built them using programmable floating resistors. Research has been done to make efficient phase shifters that are frequency independent. Here, we simplify the system to reduce the effect of frequency on phase and make a system independent of frequency in the range of 4kHz to 7kHz. This varying phase may be a problematic issue in some critical communication related applications and would make the system highly frequency dependent. A slight variation of frequency would lead to a drastic change in the phase. As mentioned earlier, traditional phase shifters are designed using an all pass filter, with a phase shift varying from 0 degrees to 180 degrees for a given frequency. This article presents the implementation of a frequency independent phase shifter using basic building blocks of analog circuits, such as op amps, JFETs and passive devices. To address that, efficient techniques are required to maintain the phase over a large range of frequency. A slight deviation in the frequency causes the phase to change drastically and that can distort the modulated signal and in turn cause loss of information. Traditional phase shifters were designed using all pass filters and several RC circuits, and they only operated at a single frequency. Some examples like single sideband (SSB) filters require precise 90-degree shifts for modulation as well as demodulation. Digital and analog communication requires large amounts of angular variations that are constant over a large range of frequencies.

Phase shift