hi,all. I want to design a 90 degree phase shifter , which frequency varying form 1.6MHz to 2.4MHz，Could somebody give me an idea ?
Thanks.Best Regards
Look up the hilbert FIR filter or alternitively for analog you can build a allpass filter which provides a 90 deg phase shift over the frequency band of interest.
An allpass filter can provide 90° phase shift for exactly one frequency. Over a 1:1.5 frequency range, the phase shift would vary between about 80 and 100°. To achieve a frequency independant phase shift of 90°, you would use two chains of cascaded allpasses with stepped characteristic frequency, that produce a phase difference of 90°. It's an approximation method (similar to Hilbert FIR).