A Frequency-Controlled Ultrawide Bandwidth Phase Shifter: Phase Shifting Without a Phase Shifter?

We present in this paper results about a high-frequency analog phase shifter suitable for multi-octave operation. Principles of this ultrawide bandwidth phase shifter are based upon the use of a frequency-tunable local oscillator (LO) feeding a delay element. Through proper frequency variation, two coherent phase-shifted LO signals are produced. The first LO signal is used for fundamental up-conversion with the incident radio-frequency (RP) signal; the phase-shifted RF output signal is then obtained by down-conversion, using the second LO sipal. Measurements done on a prototype indicate an over than 20:1 operational bandwidth, merely limited by filter band-width considerations.