Patent ID: 7528679

Claim:
A circuit arrangement which, starting from an input signal generates two 90° phase-shifted output signals, in which the input signal has a base frequency and is supplied on two parallel branches including a first branch and a second branch via a branching point, comprising: in the first branch: a first sub-branch of the first branch including a first all-pass filter having a cut-off frequency which is below the base frequency; a second sub-branch of the first branch including a second all-pass filter having a cut-off frequency which is above the base frequency; and a first adder or subtractor for combining output signals of the first all-pass filter and the second all-pass filter to produce one of the two 90° phase-shifted output signals; and in the second branch: a first sub-branch of the second branch including a third all-pass filter having a cut-off frequency which is above the base frequency; a second sub-branch of the second branch including a fourth all-pass filter, whose frequency is below the base frequency; and a second adder for combining output signals of the third all-pass filter and the fourth all-pass filter to produce another one of the 90° phase-shifted output signals.