Vector modulation system and method for wideband impulse radio communications

• US 6,763,057 B1
• Filed: 03/29/2000
• Issued: 07/13/2004
• Est. Priority Date: 12/09/1999
• Status: Expired due to Fees

• Current Assignee: Alereon Incorporated (PNG Telecommunications, Inc.)
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Richards, James L., Fullerton, Larry W., Cowie, Ivan A., Brethour, Vernon R.
• Primary Examiner(s): Liu, Shuwang
• Application Number:
  US09/538,519
• Time in Patent Office: 1,567 Days
• Field of Search: 375/141, 375/130, 375/135, 375/136, 375/142, 375/150, 375/259, 375/295, 370/320, 370/342, 370/441, 370/515, 340/573.1, 340/573.3
• US Class Current: 375/141
• CPC Class Codes: H04B 1/7095 Sliding correlator type
• CPC Class Codes: H04B 1/7176 Data mapping, e.g. modulation
• CPC Class Codes: H04B 1/7183 Synchronisation
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation

Abstract

An apparatus and method for communicating information using an ultra wideband impulse radio transmitter and receiver is disclosed. The method includes the steps of generating and transmitting a series of time-modulated pulses, each pulse delayed by one of four predetermined time delay periods and representative of at least two data bits of information, and receiving and demodulating the series of time-modulated pulses to estimate the data bits associated with each pulse. The apparatus includes an impulse radio transmitter and an impulse radio receiver. The transmitter transmits the series of time-modulated pulses and includes a transmitter time base, a time delay modulator, a code time modulator, an output stage, and a transmitting antenna. The receiver receives and demodulates the series of time-modulated pulses using a receiver time base and two correlators, one correlator designed to operate after a pre-determined delay with respect to the other correlator. Each correlator includes an integrator and a comparator, and may also include an averaging circuit that calculates an average output for each correlator, as well as a track and hold circuit for holding the output of the integrators. The receiver further includes an adjustable time delay circuit that may be used to adjust the predetermined delay between the correlators in order to improve detection of the series of time-modulated pulses.

Claims

1. A method of communicating information in an RF signal emitted by an ultra wideband impulse radio transmitter comprising the steps of:

a. separating the information into an information component signal containing data bits;

b. generating in the transmitter a sequence of ultra wideband RF pulses, each RF pulse characterized by a waveform defining a wave shape and a pulse cycle;

c. modulating a time position of the RF pulses in response to a channelization component signal and in response to the value of the data bits in the information component signal, wherein the time position of each modulated RF pulse can define one of at least two separated modulation states such that each pulse can communicate at least two of the data bits, and wherein the step of modulating the time position of the RF pulses in response to the information component signal includes varying the time positions of the pulses at time delay offset points along a total modulation of greater than one-quarter of the pulse cycle; and

d. transmitting the modulated RF pulses to an ultra wideband impulse radio receiver; and

e. demodulating the modulated RF pulses in the receiver to extract the information from the data bits communicated by each pulse.

2. A method of communicating information in an RF signal emitted by an ultra wideband impulse radio transmitter comprising the steps of:

a. separating the information into an information component signal containing data bits;

b. generating in the transmitter a sequence of ultra wideband RF pulses, each RF pulse characterized by a waveform defining a wave shape and a pulse cycle;

c. modulating a time position of the RF pulses in response to a channelization component signal and in response to the value of the data bits in the information component signal, wherein the time position of each modulated RF pulse can define one of at least two separated modulation states such that each pulse can communicate at least two of the data bits, and wherein the step of modulating the time position of the RF pulses in response to the information component signal includes varying the time positions of the pulses at time delay offset points along a total modulation of greater than one-quarter of the pulse cycle;

d. adjusting the positions of the time delay offset points along the pulse cycle to maximum separation between the modulation states;

e. transmitting the modulated RF pulses to an ultra wideband impulse radio receiver; and

f. demodulating the modulated RF pulses in the receiver to extract the information from the data bits communicated by each pulse.

3. The method of claim 2 wherein the step of adjusting the positions of the time delay offset points includes varying the positions of the offset points in response to changes in the wave shape of the transmitted RF pulses.

4. A method of communicating information in an RF signal emitted by an ultra wideband impulse radio transmitter comprising the steps of:

a. separating the information into an information component signal containing data bits;

b. generating in the transmitter a sequence of ultra wideband RF pulses, each RF pulse characterized by a waveform defining a wave shape and a pulse cycle;

c. modulating a time position of the RF pulses in response to a channelization component signal and in response to the value of the data bits in the information component signal, wherein the time position of each modulated RF pulse can define one of at least two separated modulation states such that each pulse can communicate at least two of the data bits, wherein the step of modulating the time position of the RF pulses in response to the information component signal includes varying the time positions of the pulses at time delay offset points along a total modulation of greater than one-quarter of the pulse cycle, and wherein each RF pulse is modulated by the information component signal to one of four modulation states, each modulation state corresponding to one of four time delay offset points nominally separated in time by approximately one-quarter cycle intervals along the pulse cycle;

d. transmitting the modulated RF pulses to an ultra wideband impulse radio receiver; and

e. demodulating the modulated RF pulses in the receiver to extract the information from the data bits communicated by each pulse.

5. The method of claim 4 wherein the demodulation step includes separating the time position of each transmitted RF pulse into a reference channel and an offset channel, the reference channel based on a first timing signal synchronized with the channelization component signal and the offset channel based on a second timing signal that is delayed from the first timing signal by a known offset period.

6. The method of claim 5 wherein the known offset period corresponds to the time separation between the time delay offset points in the transmitted RF pulses.

7. A wideband impulse radio communications system comprising:

a. an impulse radio transmitter having an information component modulator, the information component modulator electrically connected to an output stage and operative to modulate a time position of each of a series of wideband RF pulses generated by the output stage;

b. the information component modulator operative to modulate the time position of each RF pulse into one of at least four separate modulation states, whereby each RF pulse can communicate at least two bits of data;

c. an impulse radio receiver comprising a first correlator responsive to a first timing signal and at least one delayed correlator, the delayed correlator responsive to a second timing signal that is delayed from the first timing signal by an offset period; and

d. the first correlator and delayed correlator having separate outputs that generate signals that, when examined with respect to a single pulse, indicate the modulation state and data associated with that pulse by the transmitter.

8. The system of claim 7 wherein the receiver further comprises an adjustable time delay circuit coupled to the first timing signal and is operative to generate the second timing signal, and wherein the system further comprises means to vary the offset period to improve separation between the modulation states.

9. The system of claim 7 wherein the first and delayed correlators each include an integrator and a comparator, each comparator having a first input coupled to an integrator output and a voltage reference input.

10. The system of claim 9 wherein the first and delayed correlators further comprise a sample and hold circuit connected between the integrator and the comparator, and a signal averager having an input coupled to the output of sample and hold circuit and an output coupled to the comparator voltage reference input.

11. The system of claim 10 wherein the receiver further comprises an adjustable time delay circuit coupled to the first timing signal and operative to generate the second timing signal, and wherein the system further comprises means to vary the offset period to improve separation between the modulation states.

12. A vector modulation apparatus, comprising:

an impulse radio transmitter comprising

a transmitter time base for providing a transmitter periodic timing signal;

a time delay modulator connected to the transmitter time base and an information source, the time delay modulator responsive to the information source and operable to delay the timing signal by one of four predetermined time delay periods in order to generate a time delay modulator signal, and wherein the time delay periods represent two bits of data;

a code time modulator connected to the time delay modulator and a PN code source, the code time modulator operable to delay the time delay modulator signal in accordance with a predetermined PN code stored in the PN code source to generate a code time modulator signal;

a transmitter output stage connected to the code time modulator and operable to generate wideband RF pulses in response to the code time modulator signal received from the code time modulator; and

a transmitter antenna for emitting the wideband RF pulses;

an impulse radio receiver comprising

a receiver antenna for receiving the wideband RF pulses;

a receiver time base for generating a receiver periodic timing signal;

a synchronizing means for synchronizing the receiver time base with the transmitter time base;

a first correlator for generating a reference output signal, the first correlator including a first multiplier and a first decode timing generator, the first decode timing generator in communication with the receiver time base and operable to generate a sequence of narrow timing pulses corresponding to the predetermined PN code;

a delayed correlator for generating a delayed offset output signal, the delayed offset output signal delayed in time with respect to the reference output signal, the delayed correlator including a second multiplier, a time delay circuit, and a second decode timing generator, the time delay circuit in communication with the receiver time base and the second decode timing generator, and the second timing generator operable to generate a delayed sequence of narrow timing pulses corresponding to the predetermined PN code; and

whereby the reference output signal and the delayed offset output signal corresponding to a single pulse are representative of the two bits of data associated with that pulse.

13. The apparatus of claim 12, wherein the time delay circuit comprises an adjustable time delay circuit and the impulse radio receiver further comprises a means for varying the adjustable time delay circuit to increase the time delay between the reference output signal and the delayed offset output signal.

14. The apparatus of claim 12, wherein the first correlator and the delayed correlator each include an integrator and a comparator, each comparator having a first input coupled to an integrator output and a voltage reference input.

15. The apparatus of claim 14, wherein each of the first and delayed correlators further comprise a sample and hold circuit connected between the integrator and the comparator, and a signal averager having an input coupled to the output of the sample and hold circuit and an output coupled to the comparator voltage reference input.

16. The apparatus of claim 15, wherein the time delay circuit comprises an adjustable time delay circuit and the impulse radio receiver further comprises a means for varying the adjustable time delay circuit to adjust the time delay between the reference output signal and the delayed offset output signal.

17. A vector modulation transmitter, comprising:

a transmitter time base for providing a transmitter periodic timing signal;

a time delay modulator connected to the transmitter time base and an information source, the time delay modulator responsive to the information source and operable to delay the timing signal by one of four predetermined time delay periods in order to generate a time delay modulator signal, and wherein the time delay periods represent at least two bits of data;

a code time modulator connected to the time delay modulator and a PN code source, the code time modulator operable to delay the time delay modulator signal in accordance with a predetermined PN code stored in the PN code source to generate a code time modulator signal;

a transmitter output stage connected to the code time modulator and operable to generate wideband RF pulses in response to the code time modulator signal received from the code time modulator; and

a transmitter antenna for emitting the wideband RF pulses.

18. A vector modulator receiver, comprising:

a receiver antenna for receiving wideband RF pulses;

a receiver time base for generating a receiver periodic timing signal;

a synchronizing means for synchronizing the receiver time base with a transmitter time base associated with the receiver;

a first correlator for generating a reference output signal, the first correlator including a first multiplier and a first decode timing generator, the first decode timing generator in communication with the receiver time base and operable to generate a sequence of narrow timing pulses corresponding to a predetermined PN code;

a delayed correlator for generating a delayed offset output signal, the delayed offset output signal delayed in time with respect to the reference output signal, the delayed correlator including a second multiplier, a time delay circuit, and a second decode timing generator, the time delay circuit in communication with the receiver time base and the second decode timing generator, and the second timing generator operable to generate a delayed sequence of narrow timing pulses corresponding to the predetermined PN code; and

whereby the reference output signal and the delayed offset output signal corresponding to a single pulse are representative of at least two bits of data associated with the single pulse by a corresponding transmitter.

19. A method of transmitting vector modulated ultra-wide band pulses, comprising the steps of:

generating a periodic timing signal using a transmitter time base;

generating a time delay modulator signal by delaying the periodic timing signal by one of four predetermined time delay periods, each time delay period representative of at least two bits of data and each time delay period having an associated modulation state;

adjusting the predetermined time delay periods to maximize separation between the modulation states associated with the predetermined time period periods;

generating a code time modulator signal by delaying the time delay modulator signal in accordance with a predetermined code stored in a code source;

generating wide band RF pulses in response to the code time modulator signal using a transmitter output stage; and

transmitting the wide band RF pulses using a transmitter antenna.

20. A method of receiving vector modulated ultra wide band pulses, comprising the steps of:

receiving the wide band pulses using a receiver antenna, each wide band pulse representative of at least two bits of data;

generating a periodic timing signal using a receiver time base;

synchronizing the receiver time base with an associated transmitter time base;

generating a sequence of narrow timing pulses corresponding to a predetermined PN code using the periodic timing signal;

generating a reference output signal by multiplying the received wide band pulses by the sequence of narrow timing pulses using a first correlator; and

generating a delayed offset output signal by multiplying the received wide band pulses by a delayed version of the sequence of narrow timing pulses using a delayed correlator.

21. A vector modulation transmitter, comprising:

means for generating a periodic timing signal;

means for generating a time delay modulator signal by delaying the periodic timing signal by one of four predetermined time delay periods, each time delay period representative of at least two bits of data and approximately one-quarter of a total time delay formed by the four predetermined time delay periods;

means for generating a code time modulator signal by delaying the time delay modulator signal in accordance with a predetermined PN code;

means for generating wide band RF pulses in response to the code time modulator signal; and

means for transmitting the wide band RF pulses.

22. A vector modulation receiver, comprising:

means for receiving the wide band pulses, each wide band pulse representative of at least two bits of data;

means for generating a receiver periodic timing signal;

means for synchronizing the receiver periodic timing signal with an associated transmitter periodic timing signal;

means for generating a sequence of narrow timing pulses corresponding to a predetermined PN code using the receiver periodic timing signal;

means for generating a reference output signal by multiplying the received wide band pulses by the sequence of narrow timing pulses; and

means for generating a delayed offset output signal by multiplying the received wide band pulses by a delayed version of the sequence of narrow timing pulses.