Determination of dispersion characteristics of a communication channel from a received training sequence processed by correlation and replication

Claim 2

Apparatus for use in a television signal transmitter wherein the transmitted television signal incorporates horizontal line periods and wherein signal dispersion having an expected range of delay is present in the transmitted television signal after propagation through a communications medium, said apparatus CHARACTERISED BY means (402) for generating a training sequence, said training sequence including a number of predetermined symbols and having a duration at least equal to said range of delay, and means (403,405,406) for transmitting said training sequence in predetermined ones of said horizontal line periods at a predetermined symbol rate.

Claim 3

Apparatus as claimed in claim 2 wherein said transmitting means also serves to transmit video and audio signals.

Claim 4

Apparatus as claimed in claim 3 wherein said transmitting means serves to transmit said video and audio signals in a predetermined television signal format.

Claim 5

Apparatus as claimed in claim 1 wherein said transmitting means also serves to transmit an information signal in time intervals surrounding said associated time interval.

Claim 6

Apparatus as claimed in any preceding claim wherein said training sequence is a pseudorandom sequence.

Claim 7

Apparatus as claimed in claim 6 wherein said predetermined symbols in said pseudorandom sequence have equal positive and negative values.

Claim 8

Apparatus as claimed in claim 6 wherein said predetermined symbols in said pseudorandom sequence have values which are zero and nonzero.

Claim 9

Apparatus as claimed in any one of claim 1 to 5 wherein said training sequence is a modified pseudorandom sequence in which a constant value is added to each predetermined symbol.

Claim 10

Apparatus as claimed in any preceding claim wherein said transmitting means includes means (404) for spectrally shaping said training sequence prior to transmission.

Claim 11

Apparatus as claimed in claim 10 wherein said spectrally shaping means includes a tapped delay line clocked at a multiple of said predetermined symbol rate.

Claim 12

Apparatus as claimed in claim 10 or 11 wherein said spectrally shaping means provides raised cosine spectral shaping.

Claim 13

Receiver apparatus for use in a communications system wherein any received signal has propagated through a communications medium in which signal dispersion may be present, said receiver apparatus CHARACTERISED BY means (515,517), responsive to a received training sequence including a plurality of predetermined symbols occurring at a predetermined symbol rate, for processing said received training sequence using correlation and signal replication, and means (520) responsive to the processed training sequence for determining at least one characteristic of said signal dispersion.

Claim 14

The apparatus of claim 13 wherein said processing means provides correlation using a clock signal which is n times said predetermined symbol rate, where n is an integer ≧ 1.

Claim 15

The receiver apparatus of claim 13 wherein said training sequence is a pseudorandom sequence and said processing means is responsive to said pseudorandom sequence.

Claim 16

The receiver apparatus of claim 13 wherein said processing means correlates said training sequence with a predetermined set of coefficients and replicates said correlated training sequence.

Claim 17

The apparatus of claim 16 wherein each coefficient is said predetermined set of coefficients is a binary number.

Claim 18

The apparatus of claim 17 wherein the binary numbers have equal positive and negative values.

Claim 19

The apparatus of claim 17 wherein the binary numbers have values which are zero and nonzero.

Claim 20

The receiver apparatus of claim 13 wherein said processing means replicates said received training sequence at least one time and correlates said received training sequence with a predetermined set of coefficients and correlates the replica of said received training sequence with said predetermined set of coefficients.

Claim 21

The receiver apparatus of claim 13 further including a source (505) of at least one carrier signal and said determining means determines the phase characteristic of said signal dispersion and controls said carrier signal source.

Claim 22

The receiver apparatus of claim 13 further including an equalizer (510) and said determining means adjusts the operation of said equalizer.

Claim 23

The receiver apparatus of claim 13 wherein said determining means determines the amplitude and delay characteristics of said signal dispersion.

Claim 24

The receiver apparatus of claim 13 further including an automatic gain control circuit (502) through which said received training sequence is coupled and said determining means includes means for controlling the gain of said automatic gain control circuit.

Claim 26

A communication system comprising a transmitter and a receiver which are separated by a communications medium in which signal dispersion having an expected range of delay may be present, said transmitter CHARATERISED BY means for generating a training sequence, said training sequence including a number of predetermined symbols and having a duration at least equal to said range of delay, and means for transmitting said training sequences in an associated time interval, and said receiver CHARACTERISED BY means, responsive to a received training sequence including a plurality of predetermined symbols, for processing said received training sequence using correlation and signal replication, and means responsive to the processed training sequence for determining at least one characteristic of said signal dispersion.