The invention provides a 90-degree active bridge with an ultra-
broad band. The active bridge comprises a first all-pass filter network composed of 2n-stage
cascade all-pass filters and a second all-pass filter network composed of 2n-stage
cascade all-pass filters, wherein an
angular frequency product of an i stage of the first all-pass filter network and a (2n-i+1) stage of the second all-pass filter network is a definite value, n is a positive integer, and i is in a range from 1 to 2n. According to the 90-degree active bridge with the ultra-
broad band, the 90-degree active bridge is used in a
broad band range of a
baseband signal to perform a stable 90-degree phase shift for signals, the
phase error range is less than 1 degree,two channels of signals which are subjected to the phase shift can be subjected to addition, subtraction and
gain amplification, the active bridge can be excellently applied to the
single side band output of the base band broad band
signal close to
zero frequency, simultaneously
weak signal can be subjected to 100-time
gain amplification, besides, the
gain amplification is achieved and simultaneously the
phase error range is controlled within 2 degrees, and the phase shift characteristic is stable.