Method and system for pulse interval modulation

Apparatus for selecting a desired transmitted series of pulses of wave energy in the presence of undesired pulses comprising:

• means for modulating the spacing between adjacent pulses of the transmitted series of pulses in accordance with a selected psuedo-random code which repeats after one cycle of a predetermined number of pulses, the spacing between adjacent pairs of pulses differing for all pulse pairs in the code;
• means for receiving both the undesired and the transmitted series of pulses;
• means for generating a series of pulses spaced in a manner related to the selected psuedo-random code and equal in number to at least one cycle of the code;
• and,
• means for successively comparing the spacing between a predetermined number of said received pulses with the spacing between said generated pulses.

An encoder comprising:

• pulse generating means;
• means for establishing a plurality of different time intervals;
• and,
• means for modulating the spacing of adjacent pulses generated by said pulse generating means in accordance with unique pairs of time intervals selected in a predetermined order to thereby encode the pulse signal as an ordered series of unique time interval pairs.

Apparatus for decoding an incoming signal encoded in accordance with a predetermined code while simultaneously searching for an incoming signal encoded in accordance with said first predetermined code comprising:

• means for generating first and second signals encoded in accordance with the predetermined code;
• means for comparing the encoded incoming signal with said first signal at a comparison rate higher than the repetition rate of the incoming signal;
• means for synchronizing said second signal with the encoded incoming signal in response to a favorable comparison;
• means for gating the encoded incoming signal to a utilization device in response to the synchronized second signal;
• means for continuing the comparing of the encoded incoming signal with said first signal at said comparison rate after synchronizing the second signal;
• means for correlating the code positions in the encoded incoming signal indicated by said first and second signals in response to each further favorable comparison;
• and,
• means for synchronizing said second signal with a first received encoded incoming signal in response to said correlating means.

A method for synchronizing a receiver to a transmitted series of pulses of wave energy of wave energy comprising the steps of:

• (a) transmitting a series of pulses of wave energy spaced according to a selected psuedo-random, cyclically repetitive code wherein the spacing of the pulses defines a plurality of sequential pairs of intervals with each pair of intervals being unique within one cycle of the code;
• (b) receiving the pulses of wave energy;
• (c) shifting the received pulses into a first serial shift register clocked at a first rate;
• (d) generating a series of pulses defining pulse pairs spaced in a manner related to and in the same sequence as the pulse pairs of the transmitted pulses;
• (e) shifting the generated series of pulses into a second shift register clocked at a second predetermined rate higher than the first predetermined rate;
• (f) comparing the signal levels of corresponding stages of the first and second shift registers;
• and,
• (g) generating a synchronization signal in response to a favorable comparison of the signal levels of at least three corresponding stages of the first and second shift registers.

A method for selecting a desired transmitted series of pulses of wave energy in the presence of interfering pulses comprising the steps of:

• (a) modulating the spacing between adjacent pulses of a transmitted series of pulses in accordance with a selected psuedo-random code which repeats after one cycle of a predetermined number of pulses, the spacing between adjacent pairs of pulses differing for all pulse pairs in the one cycle of the code;
• (b) receiving the transmitted series of pulses in the presence of interfering pulses;
• (c) generating a series of pulses spaced in relation to the selected psuedo-random code and equal in number to at least one cycle of the code;
• and,
• (d) successively comparing the spacing between a predetermined number of the received pulses and the spacing between the generated pulses until at least two successive spaces compare favorably.

A method for decoding an incoming signal encoded in accordance with a predetermined code while simultaneously searching for an incoming signal encoded in accordance with the predetermined code comprising the steps of:

• (a) generating first and second signals encoded in accordance with the predetermined code;
• (b) comparing the encoded incoming signal with the first signal at a comparison rate higher than the repetition rate of the incoming signal;
• (c) synchronizing the second signal with the encoded incoming signal in response to a favorable comparison;
• (d) gating the encoded incoming signal to a utilization device in response to the synchronized second signal;
• (e) continuing the comparing of the encoded incoming signal with the first signal at said comparison rate after synchronizing the second signal;
• (f) correlating the code positions in the encoded incoming signal indicated by the first and second signals in response to each further favorable comparison;
• and,
• (g) synchronizing the second signal with the first received encoded incoming signal in response to the correlation.

Apparatus for selectively generating an encoded pulse signal comprising:

• a read only memory having a plurality of unique digital words each stored at a location assigned a predetermined address;
• means for selectively addressing said predetermined locations to read the digital words stored at said locations;
• and,
• means for spacing sequential pulses in accordance with pairs of time intervals related in duration to digital words read from said locations.

Apparatus for selectively generating an encoded pulse signal comprising:

• first means for storing a plurality of unique digital words each at a location assigned a predetermined address;
• means for selectively generating an initial address signal corresponding to one of said predetermined addresses assigned to said locations;
• means for generating a second address signal;
• means for selectively addressing one of said predetermined locations to read the digital word at said one of said locations responsively to said initial and second address signals;
• means for generating a series of spaced pulses;
• and,
• means responsive to said pulse generating means for generating a sequential pulse spaced in accordance with the digital word read from said addressed one of said locations.

Apparatus for selectively generating an encoded pulse signal comprising:

• first means for storing a plurality of unique digital words each at a location assigned a predetermined address;
• means for selectively addressing one of said predetermined locations to read the digital word stored at said one of said locations;
• and,
• means for spacing sequential pulses in accordance with a time interval related in duration to the digital word read from said one of said locations,
• said addressing means including:
• means for selectively generating an initial address signal corresponding to one of said predetermined addresses assigned to said locations;
• a counter responsive to each of said spaced sequential pulses for providing a digital output signal;
• means for enabling said counter to generate a plurality of successive subsequent address signals;
• and,
• means for successively addressing different ones of said pre-determined locations responsively to said initial and subsequent address signals to successively read said digital words stored at said different ones of said locations.

A pulse interval modulation encoder comprising:

• first means for storing a plurality of digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• means for selectively generating an initial address signal;
• means for sequentially generating subsequent address signals;
• means for selectively reading said stored plurality of digital words responsively to said initial and subsequent address signals;
• means for generating a series of spaced pulses;
• and,
• means for modifying the spacing between successive pairs of pulses in said series of pulses in response to said selectively read digital words.

Apparatus for selecting a coded series of pulses from a received signal in the presence of interfering pulses comprising:

• first storing means for storing a plurality of digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• first addressing means for selectively addressing one of said predetermined locations to read the digital word stored at said one of said locations;
• first generating means for generating a first series of pulses;
• first modulating means for modulating the spacing between two pulses in said series of pulses in accordance with the time interval represented by the digital word read from said first storing means;
• means for comparing the spacing between pulses of the received signal with spacing between pulses of the modulated first series of pulses;
• means for generating a gating signal synchronized to the coded series of pulses in the received signal in response to a favorable comparison;
• and,
• means for selectively gating the received signal in response to said gating signal.

A laser target designation and tracking system comprising:

• a laser transmitter at a first location for transmitting a series of pulses of light wave energy toward a target;
• means at said first location for modulating the spacing between the pulses of said series of pulses in accordance with a predetermined cyclically repetitive code, the spacing of the pulses defining a plurality of sequential pairs of time intervals, each pair of time intervals being unique for one cycle of the code;
• means at a second location for receiving light wave energy reflected from the target;
• means at said second location for generating a series of pulses spaced in accordance with said predetermined code;
• and,
• means at said second location for comparing the received light wave energy with said generated series of pulses to detect said predetermined code.

A coded wave energy transmitting and receiving system comprising:

• a transmitter adapted to transmit a series of pulses applied thereto in the form of wave energy;
• a read only memory having a plurality of stored digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• first means for selectively addressing said predetermined locations of said first storing means to sequentially read the digital words stored at said locations in accordance with a sequence providing words representing unique pairs of time intervals;
• first means for generating a series of spaced pulses;
• means for modifying the spacing between the pulses of said series of pulses responsively to the digital words sequentially read from said locations;
• circuit means for applying said modified series of pulses to said transmitter for transmission thereof in the form of wave energy;
• and,
• means for receiving said modified series of pulses transmitted in the form of wave energy.

A coded wave energy transmitting and receiving system comprising:

• a transmitter adapted to transmit a series of pulses applied thereto in the form of wave energy;
• first means for storing a plurality of digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• first means for selectively addressing one of said predetermined locations of said first storing means to read the digital word stored at that location;
• first means for generating a series of spaced pulses;
• means for modifying the spacing between the pulses of said series of pulses responsively to the digital word read from said one of said locations;
• circuit means for applying said modified series of pulses to said transmitter for transmission thereof in the form of wave energy;
• and,
• means for receiving said modified series of pulses transmitted in the form of wave energy,
• said address means including:
• means for selectively generating an initial address signal corresponding to one of said predetermined addresses assigned to said locations;
• means for generating a second address signal;
• and,
• means for addressing said one of said locations responsively to said initial and second address signals.

A coded wave energy transmitting and receiving system comprising:

• a transmitter adapted to transmit a series of pulses applied thereto in the form of wave energy;
• first means for storing a plurality of digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• first means for selectively addressing one of said predetermined locations of said first storing means to read the digital word stored at that location;
• first means for generating a series of spaced pulses;
• means for modifying the spacing between the pulses of said series of pulses responsively to the digital word read from said one of said locations;
• circuit means for applying said modified series of pulses to said transmitter for transmission thereof in the form of wave energy;
• and,
• means for receiving said modified series of pulses transmitted in the form of wave energy,
• said receiving means including:
• second means for storing a plurality of digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• second means for selectively addressing one of said predetermined locations of said second storing means to read the digital word stored at that location;
• second means for generating a second series of spaced pulses;
• second means for modifying the spacing between the pulses of said second series of pulses responsively to the digital word read from said second storing means;
• means for comparing the spacing between pulses of the received modified first series of pulses and pulses of the modified second series of pulses;
• means for generating a gating signal synchronized to the received modified series of pulses in response to a favorable comparison;
• and,
• means for selectively gating the received signal in response to said gating signal.

A method for selectively generating an encoded pulse signal comprising the steps of:

• storing a plurality of digital words each at a location assigned a predetermined address;
• selectively addressing one of said predetermined locations to read the digital word stored at said one of said locations by selectively generating an initial address signal corresponding to one of said predetermined addresses assigned to said location, generating a second address signal, summing said initial and second address signals, and addressing said one of said locations responsively to the sum of said initial and second address signals;
• and,
• spacing sequential pulses in accordance with a time interval related in duration to the digital word read from said one of said locations by generating a series of spaced pulses, and modifying the spacing between said pulses responsively to the digital word read from said one of said locations.

A method for pulse interval modulation encoding comprising the steps of:

• storing a plurality of digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• selectively generating an initial address signal;
• sequentially generating subsequent address signals responsively to said initial address signal;
• selectively reading said stored plurality of digital words responsively to said initial and subsequent address signals;
• generating a series of spaced pulses;
• and,
• modifying the spacing between successive pairs of pulses in said series of pulses in response to said selectively read digital words.

A method for selecting a coded series of pulses from a received signal in the presence of interfering pulses comprising:

• storing a plurality of digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• selectively addressing one of said locations to read the digital word stored at said one of said locations;
• generating a series of pulses;
• modulating the spacing between two pulses in said series of pulses in accordance with the time interval represented by the digital word read from said addressed location;
• comparing the spacing between pulses of the received signal with spacing between pulses of the modulated series of pulses;
• generating a gating signal synchronized to the coded series of pulses in the received signal in response to a favorable comparison;
• and,
• selectively gating the received signal in response to said gating signal.

A method for designating and tracking a target comprising the steps of:

• transmitting a series of pulses of light wave energy from a first location toward a target;
• modulating the spacing between the pulses of said transmitted series of pulses of light wave energy in accordance with a predetermined cyclically repetitive code, the spacing of the pulses defining a plurality of sequential pairs of time intervals, each pair of time intervals being unique for one cycle of the code;
• receiving light wave energy reflected from the target at a second location;
• generating, at said second location, a series of pulses spaced in accordance with said predetermined code;
• comparing the light wave energy received at said second location with said generated series of pulses to detect said predetermined code;
• and,
• tracking said target in response to the detected predetermined code.

A method for transmitting and receiving coded wave energy signals comprising the steps of:

• providing a transmitter adapted to transmit a series of pulses applied thereto in the form of wave energy;
• storing in a first storing means a plurality of digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• selectively addressing one of said predetermined locations of said first storing means to read the digital word stored at that location;
• generating a first series of spaced pulses;
• modifying the spacing between a pair of pulses of said first series of pulses responsively to the digital word read from said one of said locations of said first storing means;
• applying said modified first series of pulses to said transmitter for transmission thereof in the form of wave energy;
• receiving wave energy including said modified first series of pulses transmitted in the form of wave energy;
• storing in a second storing means a plurality of digital words each representing a unique time interval and each stored at a location assigned a predetermined address;
• selectively addressing one of said predetermined locations of said second storing means to read the digital word stored at that location;
• generating a second series of spaced pulses;
• modifying the spacing between a pair of pulses of said second series of pulses responsively to the digital word read from said second storing means;
• comparing the spacing between pulses of the received wave energy with the spacing between pulses of the modified second series of pulses;
• generating a gating signal synchronized to the received modified series of pulses in response to a favorable comparison;
• and,
• selectively gating the received signal in response to said gating signal.