Method and apparatus for spread spectrum distance and velocity profile measurement

A method for extracting target range information from a pulsed time of flight ranging system comprising:

• a) generating a chip sequence;
• b) generating a plurality of replicas of the chip sequence each with a predetermined phase delay;
• c) modulating a signal with the chip sequence;
• d) transmitting the signal into an environment;
• e) recovering and recording a reflected signal from the environment;
• f) correlating the reflected signal with the plurality of replicas of the chip sequence to create and store a correlation profile;
• g) determining a largest echo amplitude and phase delay from the correlation profile;
• h) removing the largest echo amplitude and phase delay from the reflected signal;
• i) storing the largest echo amplitude and phase delay in a measurement profile;
• j) repeating f) through i);
• and
• k) processing the measurement profile to extract target range information.

A method of deriving time of flight range gated Doppler flow profiling parameters using a direct sequence spread spectrum system comprising:

• a) generating a chip sequence;
• b) generating a plurality of replicas of the chip sequence, the replicas having a plurality of predetermined phase delays and a plurality of predetermined frequency shifts;
• c) modulating an energy signal with the chip sequence;
• d) transmitting the modulated energy signal into a flow environment;
• e) recovering and recording a reflected energy signal reflected from set of targets in the flow environment;
• f) correlating the reflected energy signal with the plurality of replicas of the chip sequence to create a correlation profile;
• g) storing the correlation profile;
• h) determining a largest echo amplitude, and a phase delay and velocity corresponding to the largest echo amplitude;
• i) removing the largest echo amplitude and phase delay and velocity corresponding to the largest echo amplitude from the reflected energy signal;
• j) storing the largest echo amplitude and phase delay and velocity corresponding to the largest echo amplitude in a measurement profile;
• k) repeating f) through j);
• and,
• l) processing the measurement profile to extract time of flight range gated Doppler flow profiling parameters.

An apparatus for deriving range to and flow velocity of a target comprising:

• a) a signal processor programmed to generate a first chip sequence and a plurality of modified chip sequences;
• b) a transmit transducer that receives the first chip sequence from the signal processor and transmits a modulated energy signal into an environment using the first chip sequence;
• c) a receive transducer that receives a reflected energy signal from targets in the environment, converts the reflected energy to a digital received electric signal, and sends the digital received electric signal to the signal processor;
• d) wherein the signal processor is programmed to cross correlate the plurality of modified chip sequences with the digital received electric signal to determine a correlation set of correlation amplitude values;
• e) wherein the signal processor is programmed to identify and create a set of echo sequences from the correlation set and remove the set of echo sequences from the digital received electric signal;
• and
• f) wherein the signal processor is programmed to create a measurement profile from the set of removed echo sequences to calculate target range information from the measurement profile.

A method for identifying and removing echo sequences from a received signal, the method comprising:

• a) generating a direct sequence of predetermined length;
• b) normalizing the direct sequence;
• c) generating a transmitted sequence by repeating the direct sequence a plurality of times;
• d) receiving the received signal from a transducer;
• e) cross correlating the received signal with the transmitted sequence;
• f) identifying an echo sequence from a cross correlation value;
• g) removing the identified echo sequence from the received signal;
• and,
• h) repeating e), f), and g) a predetermined number of times.

A method for identifying and removing a set of echo sequences to build a high fidelity echo profile used to calculate ranging and flow measurements, the method comprising:

• a) generating a maximal length direct sequence;
• b) normalizing the maximal length direct sequence;
• c) generating a plurality of transmitted sequences by repeating the maximal length direct sequence a plurality of times;
• d) generating a received sequence having a plurality of echoes at a plurality of Doppler frequency shifts;
• e) cross correlating the received sequence with each of the plurality of transmitted sequences;
• f) identifying an echo sequence;
• g) removing the identified echo sequence from the received sequence;
• h) adding the removed echo sequence to a high fidelity echo profile;
• and
• i) repeating f), g), h), and i) until a desired dynamic range of the echo profile is reached.

A method for identifying and removing echo sequences from a received sequence, the method comprising:

• a) defining and setting a value for the length of a direct sequence defining and setting a value for the length of a measurement environment;
• b) defining a two dimensional maximal length direct sequence array a plurality of times greater in size than the length of the direct sequence and populated with zeros;
• c) defining a plurality of variables and populating the plurality of variables with 1s and 0s in a pseudo-random sequence;
• d) populating the maximal length direct sequence array with a deterministic sequence of 1s and 0s using an exclusive or function;
• e) normalizing the values in the maximal length direct sequence array to 1s and (−1)s;
• f) defining a two dimensional transmitted sequence array a plurality of times greater in size than the maximal length direct sequence array and populated with zeros;
• g) populating the transmitted sequence array with the deterministic sequence of 1s and (−1)s stored in the maximal length direct sequence array repeated a plurality of times;
• h) defining a two dimensional received sequence array equal in size to the transmitted sequence array and populated with zeros;
• i) populating the received sequence array with a digitized received signal;
• j) defining a two dimensional correlation array populated with zeros;
• k) defining a correlation value field with a zero value;
• l) cross correlating the received sequence array with the transmitted sequence array and populating the correlation value field with correlation values;
• m) populating the correlation array with the correlation values from the correlation value field;
• n) identifying an amplitude and a phase shift of an echo sequence corresponding to the highest correlation value;
• o) shifting the transmitted sequence by the identified phase shift;
• p) multiplying the phase shifted transmitted sequence with the identified amplitude to create the echo sequence corresponding to the highest correlation value;
• q) subtracting the echo sequence corresponding to the highest correlation value from the received sequence;
• and,
• r) Repeating k) through q) a plurality of times until a desired signal to noise ratio is achieved.

A method for identifying and removing echo sequences to build a high fidelity echo profile, the method comprising:

• a) defining and setting values for the length of a direct sequence and the length of a measurement environment;
• b) defining a two dimensional maximal length direct sequence array a plurality of times greater in size than the length of the direct sequence and populated with zeros;
• c) defining a plurality of variables and populating the plurality of variables with 1s and 0s in a random sequence;
• d) populating the maximal length direct sequence array with a deterministic sequence of 1s and 0s using an exclusive or function;
• e) normalizing the values in the maximal length direct sequence array to 1s and (−1)s;
• f) defining a two dimensional reference array a plurality of times greater in size than the maximal length direct sequence array and populated with zeros;
• g) populating the reference array with values from the maximal length direct sequence array a plurality of times;
• h) defining a plurality of two dimensional holding arrays populated with zeros;
• i) populating the plurality of holding arrays with the values from the reference array each a different plurality of times;
• j) defining a plurality of two dimensional transmitted sequence arrays populated with zeros;
• k) populating the plurality of transmitted sequence arrays with the values from the plurality of holding arrays;
• l) defining a two dimensional received sequence array populated with zeros;
• m) populating the received sequence array with a digitized received signal;
• n) defining a three dimensional correlation array populated with zeros;
• o) defining a three dimensional high fidelity echo profile array populated with zeros;
• p) defining a plurality of correlation value fields each with a value of zero;
• q) cross correlating each of the plurality of transmitted sequence arrays with the received sequence array and populating each of the plurality of correlation value fields with correlation values;
• r) populating the correlation array with the correlation values from the plurality of correlation value fields;
• s) identifying an amplitude, a phase shift, and a frequency shift of an echo sequence corresponding to the highest correlation value;
• t) shifting the transmitted sequence by the identified phase shift and time scaling the transmitted sequence by the identified frequency shift;
• u) multiplying the identified phase shifted and time scaled transmitted sequence with the identified amplitude to create the echo sequence corresponding to the highest correlation value;
• v) Subtracting the echo sequence corresponding to the highest correlation value from the received sequence;
• w) Populating the high fidelity echo profile array with values from the correlation array;
• and,
• x) Repeating p) through w) a plurality of times until a desired signal to noise ratio is achieved.