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90-degree phase shift network, system for controlling a 90-degree phase shift characteristic of the network, linearizer using all-pass filters, and system for controlling the linearizer
90-degree phase shift network, system for controlling a 90-degree phase shift characteristic of the network, linearizer using all-pass filters, and system for controlling the linearizer
A 90-degree digital phase shift network includes at least two all- pass digital filters which have a phase difference of 90 degrees therebetween. These digital filters are adapted to receive the same signal. Each of the all-pass digital filters has phase characteristics . theta. (&ohgr;) given by ##EQU1## where T represents a sampling period, P. sub.i a real number indicative of a filter coefficient, &ohgr; the angular frequency, m a weight variable, n'=n/2 (n=even number), n'=(n+ 1) /2 (n=odd number), n an order of a 90-degree digital PSN, m being a positive value other than 1, and satisfying |2m&ohgr;| / |P.sub.i | 1 when &ohgr; T is sufficiently lower than 1, while satisfying |-P.sub.i &ohgr; T.sup.2 . vertline. / 2m 1 when &ohgr; T is substantially equal to &pgr;.
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