Waveform adaptive ultra-wideband transmitter

• US 6,026,125 A
• Filed: 05/16/1997
• Issued: 02/15/2000
• Est. Priority Date: 05/16/1997
• Status: Expired due to Term

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Multispectral Solutions Incorporated (Zebra Technologies Corporation)
• Inventors: Larrick, J. Frederick Jr., Fontana, Robert J.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Fan, Chieh M.
• Application Number:
  US08/857,836
• Time in Patent Office: 1,005 Days
• Field of Search: 375/295, 375/219, 375/202, 375/204, 375/200, 342/13, 342/27, 342/159, 342/375, 342/21, 342/28, 455/93, 455/91, 455/103, 324/642
• US Class Current: 375/295
• CPC Class Codes: H04B 1/7174 Pulse generation in general H04L25/03834
• CPC Class Codes: H04B 2001/6908 using time hopping
• CPC Class Codes: H04L 27/04 Modulator circuits; Transmitter circuits

Abstract

A waveform adaptive transmitter that conditions and/or modulates the phase, frequency, bandwidth, amplitude and/or attenuation of ultra-wideband (UWB) pulses. The transmitter confines or band-limits UWB signals within spectral limits for use in communication, positioning, and/or radar applications. One embodiment comprises a low-level UWB source (e.g., an impulse generator or time-gated oscillator (fixed or voltage-controlled)), a waveform adapter (e.g., digital or analog filter, pulse shaper, and/or voltage variable attenuator), a power amplifier, and an antenna to radiate a band-limited and/or modulated UWB or wideband signals. In a special case where the oscillator has zero frequency and outputs a DC bias, a low-level impulse generator impulse-excites a bandpass filter to produce an UWB signal having an adjustable center frequency and desired bandwidth based on a characteristic of the filter. In another embodiment, a low-level impulse signal is approximated by a time-gated continuous-wave oscillator to produce an extremely wide bandwidth pulse with deterministic center frequency and bandwidth characteristics. The UWB signal may be modulated to carry multi-megabit per second digital data, or may be used in object detection or for ranging applications. Activation of the power amplifier may be time-gated in cadence with the UWB source thereby to reduce inter-pulse power consumption. The UWB transmitter is capable of extremely high pulse repetition frequencies (PRFs) and data rates in the hundreds of megabits per second or more, frequency agility on a pulse-to-pulse basis allowing frequency hopping if desired, and extensibility from below HF to millimeter wave frequencies.

Claims

1. A transmitter that radiates representations of ultra-wide band signals, said transmitter comprising:

a switched impulse generator to generate a series of high-speed low-level ultra-wideband pulses;

a waveform adapter responsive to said low-level ultra-wideband pulses, said waveform adapter including a filter that defines a center frequency of said low-level pulses; and

an antenna responsive to said waveform adapter to radiate representations of said ultra-wideband signals.

2. The transmitter according to claim 1, wherein:

said waveform adapter further defines a bandwidth of said low-level pulses.

3. An ultra-wideband transmitter comprising a signal generator that generates an ultra-wideband signal having a selectable center frequency and bandwidth, an antenna responsive to said signal generator to radiate representations of said ultra-wideband signals, said generator comprising:

an oscillator;

a low-level impulse generator to generate a low-level impulse signal to gate an output of said oscillator;

a mixer having an RF port input receiving said output of said oscillator and having an X port input receiving an output of said low-level impulse generator; and

an amplifier to amplify a signal output from said mixer to an amplified-level signal for transmission;

said amplified-level signal having a center frequency and a bandwidth based on at least one characteristic of said oscillator.

4. An ultra-wideband transmitter comprising a signal generator that generates an ultra-wideband signal having a selectable center frequency, an antenna responsive to said signal generator to radiate representations of said ultra-wideband signals, said signal generator generates an ultra-wideband signal having a selectable bandwidth and comprises:

an oscillator;

a low-level impulse generator to generate a low-level impulse signal to gate an output of said oscillator;

a filter to be impulse-excited by said low-level impulse signal;

a buffer amplifier to amplify a signal output from said filter;

a mixer having an RF port input receiving said output of said oscillator and having an X port input receiving an output of said buffer amplifier;

a bandpass filter to filter an ultra-wideband output from said mixer prior to transmission of said ultra-wideband signal; and

an amplifier to amplify a signal output from said bandpass filter to an amplified-level signal for transmission;

said amplified-level signal having a center frequency and a bandwidth based on at least one characteristic of said oscillator and at least one characteristic of said filter.

5. The ultra-wideband transmitter according to claim 4, wherein said at least one characteristic of said filter is selected from a group comprising:

center frequency;

bandwidth;

out of band rejection; and

skirt response.

6. The ultra-wideband transmitter according to claim 4, wherein:

said oscillator is a voltage controlled oscillator; and

a frequency of said oscillator being selectable between a plurality of frequencies to effect frequency hopping of said ultra-wideband transmitter.

7. The ultra-wideband transmitter according to claim 4, wherein:

power to said amplifier is gated in synchronization with timing of said signal output from said filter.

8. The ultra-wideband transmitter according to claim 4, further comprising:

a data encoder adapted and arranged to encode data in said ultra-wideband signal.

9. The ultra-wideband transmitter according to claim 8, wherein:

said data is encoded at a rate in excess of 100 megabits per second.

10. An ultra-wideband transmitter comprising a signal generator that generates an ultra-wideband signal having a selectable center frequency and bandwidth, an antenna responsive to said signal generator to radiate representations of said ultra-wideband signals, said signal generator comprising:

an oscillator;

a low-level impulse generator to generate a low-level impulse signal to gate an output of said oscillator;

a voltage-controlled buffer amplifier to amplify a signal output from said low-level impulse generator;

a mixer having an RF port input receiving said output of said oscillator and having an X port input receiving an output of said buffer amplifier;

a bandpass filter to filter an ultra-wideband output from said mixer prior to transmission of said ultra-wideband signal; and

an amplifier to amplify a signal output from said bandpass filter to an amplified-level signal for transmission;

said amplified-level signal having a center frequency based on at least one characteristic of said oscillator and having a bandwidth based on at least one characteristic of said low-level impulse signal and a control voltage to said voltage-controlled buffer amplifier.

11. The ultra-wideband transmitter according to claim 10, wherein:

power to said amplifier is gated corresponding to a timing of said signal output from said filter.

12. The ultra-wideband transmitter according to claim 10, wherein:

said oscillator is a voltage controlled oscillator; and

said frequency of said oscillator being selectable between a plurality of frequencies to effect frequency hopping of said ultra-wideband transmitter.

13. The ultra-wideband transmitter according to claim 10, wherein:

power to said amplifier is gated according to timing of said signal output from said filter.

14. The ultra-wideband transmitter according to claim 10, further comprising:

a data encoder adapted and arranged to encode data in said ultra-wideband signal.

15. The ultra-wideband transmitter according to claim 14, wherein:

said data is encoded at a rate in excess of 100 megabits per second.

16. A transmitter that radiates representations of ultra-wide band signals comprising:

an oscillator to generate a low-level signal;

a time gate to gate a several nanosecond to sub-nanosecond range time portion of an output of said oscillator thereby to produce low-level time-gated ultra-wide band signal;

said time-gated ultra-wide band signal having a center frequency corresponding to a frequency of said oscillator;

an amplifier responsive to said time-gated ultra-wide band signal to produce an amplified output; and

an antenna responsive to said amplified output to radiate representations of said ultra-wide band signals.

17. The transmitter according to claim 16, wherein said time gate comprises:

a a pair of serially connected successively fired on-off and off-on transistor switches to gate said small time portion of said output of said oscillator.

18. The transmitter according to claim 16, wherein:

said time-gated ultra-wide band signal has a bandwidth based on a pulse width of said gated time portion of said output of said oscillator.

19. The transmitter according to claim 18, wherein:

said bandwidth of said time-gated ultra-wideband signal is inversely proportional to said pulse width of said gated time portion of said output of said oscillator.

20. The transmitter according to claim 16, wherein:

said oscillator comprises a voltage controlled oscillator; and

said frequency of said oscillator is alterable between a plurality of frequencies to effect frequency hopping of said ultra-wideband transmitter.

21. The transmitter according to claim 16, wherein:

power to said amplifier is gated corresponding to a timing of said gated small time portion of said time-gated ultra-wideband signal.

22. The transmitter according to claim 16, further comprising:

a data encoder adapted and arranged to encode data in said time-gated ultra-wideband signal.

23. The ultra-wideband transmitter according to claim 22, wherein:

said data is encoded at a rate in excess of 100 megabits per second.

24. A method of radiating representations of an ultra-wideband signal having a desired center frequency, said method comprising:

generating a low-level signal having a frequency corresponding to a desired center frequency of said ultra-wideband signal;

impulse-gating said low-level signal to generate a series of discrete ultra-wideband pulses, said impulse-gating being less than about 5 nanoseconds;

waveform adapting said discrete pulses to produce a waveform-adapted output; and

applying said waveform-adapted output to an antenna to radiate representations of ultra-wide band signals.

25. The method of generating an ultra-wideband signal according to claim 24, wherein:

said low-level impulse-gating is less than 1 nanosecond.

26. The method of generating an ultra- wideband signal having a center frequency according to claim 24, further comprising:

after said impulse-gating step, amplifying said ultra- wideband pulses to a desired power level; and

radiating said amplified pulses at said center frequency.

27. The method of generating an ultra-wideband signal having a center frequency according to claim 24, further comprising:

adjusting on a pulse-by-pulse basis said frequency of said signal.

28. A method of generating an ultra-wideband signal having a center frequency, comprising:

generating a source signal having a frequency corresponding to a desired center frequency of said ultra-wideband signal;

time-gating said source signal to generate a series of discrete pulses, said time-gating being less than about 5 nanoseconds;

waveform adapting said series of discrete pulses to produce a waveform-adapted output whose frequency or bandwidth is determined by at least one of filtering, mixing, multi-level attenuating, and pulse-shaping said source signal; and

applying said waveform-adapted output to an antenna.

29. The method of generating an ultra-wideband signal according to claim 28, wherein:

said time-gating is less than 1 nanosecond.

30. The method of generating an ultra- wideband signal having a center frequency according to claim 28, further comprising:

amplifying said ultra-wideband signal to produce an amplified ultra-wideband signal of a desired power level; and

radiating said amplified ultra-wideband signal at said center frequency.

31. A signaling device including transmitter, said signaling device comprising:

a switched impulse generator to generate a series of discrete low-level ultra-wideband pulses

a waveform adapter responsive to said low-level ultra-wideband pulses that defines a center frequency and bandwidth of said ultra-wide band pulses;

said center frequency being determined by one of frequency-mixing and filtering said ultra-wide band signal; and

an antenna responsive to said waveform adapter to radiate a representation of said ultra-wideband signal.

32. A method for transmitting data using ultra-wideband techniques, said method comprising:

generating a series of UWB signal pulses by using one of an UWB impulse generator and a pulse-excited oscillator;

providing a data encoder to modulate said series of UWB signal pulses;

providing a waveform adapter to modulate said series of signal pulses with said data encoder wherein said modulating comprises at least one of inter-pulse frequency variation, inter-pulse phase shifting and multi-level attenuation according to representations of data, said modulating being achieved by waveform adapting said signal pulses by controlling one of phase, bandwidth, frequency, amplitude, and attenuation;

applying said modulated signal pulses to an antenna; and

transmitting said modulated pulses at a selectable center frequency.

33. An ultra-wideband transmitter comprising:

a signal generator to generate an ultra-wideband signal having a selectable center frequency, said signal generator comprising;

a low-level impulse generator to generate a low-level impulse signal,

a filter to be impulse-excited by said low-level impulse signal, and

an amplifier to amplify a signal output from said filter to an amplified-level signal for transmission, a center frequency and a bandwidth of said amplified-level signal being selectable based on at least one characteristic of said filter; and

an antenna responsive to said signal generator to radiate representations of said ultra-wideband signals.

34. The ultra-wideband transmitter according to claim 33, wherein:

power to said amplifier is gated corresponding to a timing of said signal output from said filter.