Equalizer for linearizing a transmission channel phase-frequency response utilizing odd and even order all-pass networks

Claim 2

An equalizer for linearizing the phase-frequency response (FIG. 6 - C0) of a transmission channel to an applied signal, the channel having a bandwidth containing preselected frequencies (f1 < f2 < f3 < f4 < f5), the equalizer being characterized by successive all pass filter stages comprising at least: first (FIG. 2 - ckt. I) and second (FIG. 2 - ckt. II) odd order filter stages for symmetrically phase shift aligning different respective groups of preselected frequencies (FIG. 6 - Delta 1, f1, f3, f5; FIG. 7 - Delta 2, f2, f3, f4), at least one frequency of each group being in common (f3), to conform to predetermined linear phase - frequency approximations (C1, C2); the first odd order filter including means for aligning an odd number of alternate ones of the preselected frequencies (f1, f3, f5) as arranged in order of increasing magnitude, the second odd order filter including means for aligning an odd number of consecutive preselected frequencies (f2, f3, f4) also arranged in order of increasing magnitude; and an even order filter stage (FIG. 2 - ckt. III) for antisymmetrically phase shift aligning the previously phase aligned frequency groups about their common frequency.

Claim 3

An equalizer for linearizing the phase - frequency response (FIG. 6 - C0) of a transmission channel to an applied signal, the channel having a predetermined bandwidth (f1 < f2 < f3 < f4 < f5), said equalizer being characterized by successive all-pass filter stages, each filter stage having its phase shift Delta phi varying as where n-m 0 for an even order phase shift, n-m 1 for an odd ordeR phase shift; and where omega 2 pi F, omega i 2 pi Fi, and omega j 2 pi Fj being the angular frequencies denominated pivot points, subject to the condition that ( Delta phi ) i 2i pi and ( Delta phi )j (2j-1) and (i, j 1, 2, 3 . . . ), and R being the real part of the filter stage transfer function H( omega ); the equalizer being further characterized by at least: a first filter stage (FIG. 2 - ckt. I) for introducing an odd order phase shift (FIG. 6 - Delta 1) to align a first group of frequencies (f1, f3, f5) along a first linear phase -frequency approximation to yield a first intermediate response characteristic (c1); a second filter stage (FIG. 2 ckt. II) for introducing an odd order phase shift (FIG. 7 - Delta 2) to align a second group of frequencies (f2, f3, f4,) along a second linear phase -frequency approximation (d) to yield a second intermediate response characteristic (c2); and a third filter stage (FIG. 2 - ckt. III) for introducing an even order phase shift (FIG. 8 - Delta 3) to linearly align the first and second linear approximations to yield a final response characteristic (c3).

Claim 4

An equalizer for linearizing the phase - frequency response (FIG. 6 - C0) of a transmission channel to an applied signal, the channel having a predetermined bandwidth (f1 < f2 < f3 < f4 < f5), said equalizer being characterized by successive all-pass filter stages, each filter stage having its phase shift Delta phi varying as where n-m 0 for an even order phase shift, n-m 1 for an odd ordeR phase shift; and where omega 2 pi F, omega i 2 pi Fi, and omega j 2 pi Fj being the angular frequencies denominated pivot points, subject to the condition that ( Delta phi ) i 2i pi and ( Delta phi )j (2j-1) and (i, j 1, 2, 3 . . . ), and R being the real part of the filter stage transfer function H( omega ); the equalizer being further characterized by at least: a first filter stage (FIG. 2 - ckt. I) for introducing an odd order phase shift (FIG. 6 - Delta 1) to align a first group of frequencies (f1, f3, f5) along a first linear phase -frequency approximation to yield a first intermediate response characteristic (c1); a second filter stage (FIG. 2 ckt. II) for introducing an odd order phase shift (FIG. 7 - Delta 2) to align a second group of frequencies (f2, f3, f4,) along a second linear phase -frequency approximation (d) to yield a second intermediate response characteristic (c2); and a third filter stage (FIG. 2 - ckt. III) for introducing an even order phase shift (FIG. 8 - Delta 3) to linearly align the first and second linear approximations to yield a final response characteristic (c3).

Claim 5

An equalizer according to claim 2, wherein the phase shift Delta phi of the first filter stage (FIG. 3) varies as the pivot points F1 and F2 coinciding with the respective extremes of the first group of frequencies (f1 and f5).

Claim 6

An equalizer according to claim 3, wherein the phase shift Delta phi of the second filter stage (FIG. 4c) varies as wherein the pivot points F1'' and F3'' coincide with the lower extreme (f1) and an intermediate (f3) frequency of the first group, F2'' and F4'' coincide with frequencies of the second group, and m kn.

Claim 7

An equalizer according to claim 2, wherein each odd and even order filter stage respectively produces a symmetrical and antisymmetrical phase shift as measured from a corresponding linear phase - frequency approximation connecting at least extreme and intermediate frequencies of the respective group.

Claim 8

An equalizer according to claim 1, wherein the first and second odd order stages and the even order stage are permutatively arrangeable.

Claim 9

An equalizer according to claim 2, wherein the first and second odd order stages and the even order stage are permutatively arrangeable.