CARRIER TRANSVERSAL EQUALIZER

• US 3,611,201 A
• Filed: 10/21/1969
• Issued: 10/05/1971
• Est. Priority Date: 10/21/1969
• Status: Expired due to Term

• Current Assignee: James E. Goell
• Original Assignee: James E. Goell
• Inventors: Goell, James E.
• Primary Examiner(s): Saalbach, Herman Karl
• Assistant Examiner(s): Nussbaum, Marvin
• Application Number:
  US04/868,034
• Time in Patent Office: 714 Days
• Field of Search: 333/18,28,7T 178/66,69 325/42
• US Class Current: 333/18
• CPC Class Codes: H01P 1/18 Phase-shifters H01P1/165 takes precedence
• CPC Class Codes: H04L 25/03885 adaptive
• CPC Class Codes: H04L 27/01 Equalisers baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005

Abstract

A carrier transversal equalizer includes a plurality of parallel modules each comprising the series combination of an attenuator and a time-delay element. The need for phase shifters is obviated provided that the equalizer is designed such that its complex gain function is periodic, its phase characteristic is odd about the origin and its gain characteristic is even about the origin.

Claims

1. For use in a transmission system which translates information signals at a carrier frequency fc and which is characterized by the introduction of phase distortion in said signals, a transversal equalizer comprising means for directing portions of said signal into a plurality of separate transmission paths, means in each of said paths for controllably attenuating said signal portion therein, means in each of said paths for controllably time delaying said signal portion therein, and characterized in that the combination of said directing, attenuating and time-delaying means is adapted so that the phase characteristic of said equalizer is periodic in frequency and odd about the origin and the gain characteristic of said equalizer is even about the origin.

2. The equalizer of claim 1 wherein said distortion is primarily even ordered and wherein the design frequency fe of said equalizer satisfies approximately the following relationship:

fe (m+ 1/2 ) Delta f, where Delta f is the bandwidth over which equalization is desired and m is an integer, and means for translating said carrier frequency from fc to fe.

3. The equalizer of claim 2 wherein said system is a waveguide transmission system which introduces primarily quadratic phase distortion and wherein m is an even integer.

4. The equalizer of claim 2 wherein said directing means comprises an input and an output terminal, a plurality of modules connected in parallel between said terminals, each of said modules comprising the series combination of said attenuating means and said time delay means.

5. The equalizer of claim 4 wherein the attenuation level of each of said attenuating means is equal approximately to a corresponding Fourier coefficient of the Fourier series of the transfer function of the component of said system producing the phase distortion.

6. The equalizer of claim 5 wherein the difference in delay of adjacent time-delay means is equal approximately to 1/2 Delta f.

7. The equalizer of claim 6 wherein the phase characteristic of said equalizer is characterized by periodicity of 2fb, where fb is the baud rate, and the bandwidth Delta f is equal to fb.

8. The equalizer of claim 1 wherein said distortion is primarily odd ordered and wherein the design frequency fe of said equalizer satisfies approximately the following relationship:

fe n Delta f where Delta f is the bandwidth over which equalization is desired and n is an integer.

9. The equalizer of claim 8 wherein said directing means comprises an input and an output terminal, a plurality of modules connected in parallel between said terminals, each of said modules comprising the series combination of said attenuating means and said time-delay means.

10. The equalizer of claim 9 wherein the attenuation level of each of said attenuating means is equal approximately to a corresponding Fourier coefficient of the Fourier series of the transfer function of the component of said system producing the phase distortion.

11. The equalizer of claim 10 wherein the difference in delay of adjacent time-delay means is equal approximately to 1/2 Delta f.

12. The equalizer of claim 11 wherein the phase characteristic of said equalizer is characterized by a periodicity of 2fb, where fb is the baud rate, and the bandwidth Delta f is equal to fb.

13. A waveguide transmission system comprising a waveguide transmission path in at least a portion of which quadratic phase distortion is disadvantageously introduced, a transversal equalizer in said path comprising input and output terminals, a plurality of modules connected in parallel between said terminals, each of said modules comprising attenuation and time-delay means, the attenuation level of each of said attenuation means being equal to a corresponding Fourier coefficient of the Fourier series of the transfer function of the quadratic phase distortion portion of said path, the difference in delay of adjacent time-delay means being equal to 1/2 Delta f, where Delta f, the bandwidth over which equalization is desired, is equal to the baud rate of said system, and wherein said attenuation and time-delay means are adapted so that the design frequency fe of said equalizer satisfies approximately the following relationship:

fe (m + 1/2 ) Delta f, m being an even integer.

14. A method of equalizing phase distortion in information signals at carrier frequencies comprising the steps of:

directing portions of said signal through an equalizer and into a plurality of separate transmission paths therein, controllably attenuating said signal portions in each of said paths, controllably time delaying said signal portions in each of said paths, performing each of said directing, attenuating and time-delaying steps so as to produce in said equalizer a phase characteristic periodic in frequency and odd about the origin and a gain characteristic even about the origin.

15. The method of claim 14 wherein said performing step includes the additional steps of:

attenuating said signals by an amount equal approximately to a corresponding Fourier coefficient of the Fourier series of the transfer function of the component producing the phase distortion, and time delaying said signal portions such that the difference in delay of adjacent portions is equal approximately to 1/2 Delta f where Delta f is the bandwidth over which equalization is desired.

16. The method of claim 15 wherein said distortion is primarily even ordered and said performing step includes adjusting the equalizer design frequency fe to satisfy approximately the relationship fe (m+ 1/2 ) Delta f, where Delta f is the bandwidth over which equalization is desired and m is an integer.

17. The method of claim 16 wherein said distortion is quadratic waveguide phase distortion and m is an even integer.

18. The method of claim 15 wherein said distortion is primarily odd ordered and said performing step includes adjusting the equalizer design frequency fe to satisfy approximately the relationship fe n Delta f where Delta f is the bandwidth over which equalization is desired and n is an integer.