Phase calculation circuitry in digital television receiver

Claim 1

Apparatus for generating the instantaneous phase value θ of the vector sum C of a pair of quadrature-related signal components I and Q with respect to one of said signal components I; said apparatus comprising: (a) means for receiving a pair of instantaneous magnitude values of said orthogonal signal components I and Q; (b) means for calculatiang a value equal to: ##EQU9## (c) a source of coefficient values Kι, where ι is an index varying from 1 to 2; (d) means for calculating the logarithm of tan α to the base B, hereinafter Log B (tan α); wherein said logarithm calculating means comprises a ROM to which the value of tan α is applied as an address code, and which is programmed to contain the associated Log B (tan α) values at the respective memory locations; (e) first means for adding to the value of Log B (tan α) a value equal to Log B (M) +Log B (K 1 ), where M is a constant; (f) first means for determining the antilogarithm of the output of said first adding means; (g) means for multiplying the value of Log B (tan α) by a factor of 2; (h) second means for adding to the output of said multiplying means a value equal to Log B (M) +Log B (|K 2 |) to the base B; (i) second means for determining the antilogarithm of the output of said second adding means; (j) means for combining the output of said first antilogarithm determining means with the output of said second antilogarithm determining means to generate the value α'; and (k) means for transposing the angle α' to the corresponding phase angle θ of the vector sum C.