Method and apparatus for reducing crosstalk on cross-polarized communication links

Claim 2

A polarization diversity transmission system with apparatus for reducing crosstalk comprising in combination: means for transmitting information signals in a set of two distinct linear polarizations; means for transmitting a frequency-diversity pilot signal along with each of the information signals in each of the polarizations; and means for receiving the signals in each of the poLarizations including means including an input and an output for separating from the information signals components of the pilot signals received in each of the polarizations, means for processing the components of the pilot signals and for forming therefrom control signals proportional to the degree of correction required to cancel the crosstalk induced between the polarizations during transmission and reception, and means responsive to said control signal forming means for correcting the received information signals to cancel the crosstalk automatically, said correcting means comprising an electrical control circuit including an input and an output, means for applying the information signals received in each of the polarizations to the input of said circuit, means for selectively varying the amplitude and phase of said information signals in response to the control signals, and means for additively combining said information signals to generate at the output of said circuit information signals devoid of the crosstalk.

Claim 3

A polarization diversity transmission system according to claim 1 in which said electrical control circuit of said correcting means is a feedback circuit, the output of which is serailly connected to the input of said pilot signal separating means.

Claim 4

A polarization diversity transmission system according to claim 1 in which said electrical control circuit of said correcting means is a feed-forward circuit, the input of which is serially connected to the output of said pilot signal separating means.

Claim 5

A polarization diversity transmission system according to claim 1 in which: said information signal transmitting means transmits two information signals A1 and A2 in two distinct linear polarizations; said pilot signal transmitting means transmits two pilot signals along with the two information signals in each of the two polarizations, one pilot signal at a frequency f1 and the other pilot signal at a frequency f2, where f1 is not equal to f2; said received information signals are of the forms S1 and S2respectively, where S1 V11A1+ V21A2 S2 V12A1 + V22A2 and where V11, V12, V21, and V22 are complex coefficients indicative of the level of crosstalk induced between the polarizations during transmission and reception; the components of the pilot signals received in each of the polarizations are proportional to the coefficients V11, V12, V21, and V22, respectively; said processing and control signal forming means produces control signals C11, C12, C13, C21, C22, C23, respectively, of the form C11 * - V12/V11 C12 * the angle of V12/V11 C13 * (V11) (1 - (V12V21/V11V22) ) 1 C21 * - V21/V22 C22 * the angle of V21/V22 C23 * (V22) (1 - V12V21/V11V22) ; 1and said correcting means generates replicas of the transmitted information signals A1 and A2, respectively, according to the form

Claim 6

A polarization diversity microwave transmission system with apparatus for reducing crosstalk comprising in combination: means for transmitting microwave information signals A1 and A2 within the same frequency-band and in two distinct linear polarizations; means for transmitting a pilot signal along with each of the information signals in each of the polarizations, one pilot signal at a frequency f1 and the other pilot signal at a frequencY f2, where f1 and f2 are within the frequency-band of the information signals A1 and A2, respectively, and where f1 is not equal to f2; means for receiving the signals in each of the polarizations, where the received information signals are of the form S1 V11A1 + V21A2 S2 V12A1 + V22A2 and where V11, V12, V21 and V22 are complex coefficients indicative of the level of crosstalk induced between the polarizations during transmission, said receiving means further including means for separating components of the pilot signals received in each of the polarizations, said components being proportional to the coefficients V11, V12, V21, V22, respectively, means for processing said components and for forming control signals C11, C12, C13, C21, C22, C23, respectively, of the form C11 * - V12/V11 C12 * the angle of V12/V11 C13 * (V11) (1 - (V12V21/V11V22)) 1 C21 * - V21/V22 C22 * the angle of V21/V22 C23 * (V22) (1 - (V12V21/V11V22)) 1; and correcting means responsive to said control signal forming means for generating replicas of the transmitted information signals A1 and A2 according to the following form

Claim 7

A polarization diversity microwave transmission system with apparatus for reducing crosstalk comprising in combination: means for transmitting microwave information signals A1 and A2 within the same frequency-band and in two distinct linear polarizations; means for transmitting a pilot signal along with each of the information signals in each of the polarizations, one pilot signal at a frequency f1 and the other pilot signal at a frequencY f2, where f1 and f2 are within the frequency-band of the information signals A1 and A2, respectively, and where f1 is not equal to f2; means for receiving the signals in each of the polarizations, where the received information signals are of the form S1 V11A1 + V21A2 S2 V12A1 + V22A2 and where V11, V12, V21 and V22 are complex coefficients indicative of the level of crosstalk induced between the polarizations during transmission, said receiving means further including means for separating components of the pilot signals received in each of the polarizations, said components being proportional to the coefficients V11, V12, V21, V22, respectively, means for processing said components and for forming control signals C11, C12, C13, C21, C22, C23, respectively, of the form C11 * - V12/V11 C12 * the angle of V12/V11 C13 * (V11) (1 - (V12V21/V11V22)) 1 C21 * - V21/V22 C22 * the angle of V21/V22 C23 * (V22) (1 - (V12V21/V11V22)) 1; and correcting means responsive to said control signal forming means for generating replicas of the transmitted information signals A1 and A2 according to the following form