Ultra-wideband receiver and transmitter

Abstract

A waveform-adaptive ultra-wideband (UWB) transmitter and noise-tracking UWB receiver for use in communications, object detection and radar applications. In one embodiment, the output of an oscillator is gated by a low-level impulse generator either directly or through an optional filter. In a special case of that embodiment wherein the oscillator is 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, the 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 low-level impulse signal can be generated digitally. The UWB signal may be modulated to carry data, or may be used in object detection or ranging applications. The power amplifier may be gated to provide a power-efficient UWB transmitter. The UWB transmitter exhibits well defined and controllable spectral characteristics. 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.

We claim: 
     
       1. A communication system utilizing a carrier-based ultra-wideband transmitter, said system comprising:
 a switched impulse generator to generate a low-level ultra-wideband signal characterized by a series of UWB pulses, said switched impulse generator including one of an on-off switched oscillator, an oscillator having a time-gated dc bias that alternately biases the oscillator on and off, and an impulse-gated mixer that mixes an oscillator output; 
 a wave filter responsive to said switched impulse generator to filter said UWB pulses to define a center-frequency thereof; 
 an antenna responsive to said filter to radiate a carrier-based representation of said UWB pulses at said the defined center-frequency; and 
 a receiver that detects data from individual ones of radiated UWB pulses. 
 
     
     
       2. A method of detecting an object utilizing ultra-wideband transmitting techniques, said method comprising:
 impulse-switching an oscillator to generate a low-level ultra-wideband signal; 
 wave filtering said low-level ultra-wideband signal to provide a carrier and a center frequency thereof; 
 after said filtering step, transmitting a representation of said low-level ultra-wideband signal; and 
 after said transmitting step, receiving from said object a reflected pulse of said representation of said ultra-wideband signal thereby to detect said object. 
 
     
     
       3. The communication system as recited in  claim 1 , further comprising an amplifier interposed between said wave filter and antenna to amplify said ultra-wideband signal. 
     
     
       4. The communication system as recited in  claim 3 , wherein said wave filter comprises one of a band-pass filter and a pulse shaper that substantially confines radiated emissions of said antenna within a given passband. 
     
     
       5. The communication system as recited in  claim 1 , wherein the receiver includes:
 a variable attenuator coupled to a receiving antenna to adjust attenuation levels thereof based on a rate of error detection of said radiated ultra-wideband pulses received at said receiver, and 
 a detector to detect an output of said variable attenuator. 
 
     
     
       6. The communication system as recited in  claim 5 , wherein said detector comprises a tunnel diode and said variable attenuator to adjust said attenuation levels by alternately applying noise and received information signals to said tunnel diode. 
     
     
       7. The communication system as recited in  claim 6 , further including a controller that digitally controls the variable attenuator according to signals received during respective noise dwells and data dwells to enable the detector to discriminate between said noise and received information signals. 
     
     
       8. The communication system as recited in  claim 7 , wherein said controller utilizes a bit error rate to discriminate between noise and information signals. 
     
     
       9. The method of  claim 2 , further comprising the step of providing a tunnel diode to receive the reflected pulse. 
     
     
       10. The method of  claim 2 , further comprising, after generating said low-level ultra-wideband signal, amplifying said low-level ultra-wideband signal. 
     
     
       11. The method of  claim 10 , wherein said filtering comprises one of bandpass filtering and pulse shaping of said low-level ultra-wideband signal in order to substantially confine radiated emissions of said antenna within a given passband. 
     
     
       12. The method of  claim 11 , further comprising the step of defining a bandwidth of the signal radiated upon the object. 
     
     
       13. The method of  claim 2 , further comprising, in the receiving step:
 variably attenuating the level of the reflected pulse according to detected error in the reflected pulse received at said receiver, and 
 detecting a signal produced by the reflected pulse after said variably attenuating. 
 
     
     
       14. The method of  claim 13 , further including providing a tunnel diode to detect the reflected pulse and adjusting said attenuating by alternately applying noise and received information signals to said tunnel diode. 
     
     
       15. The method of  claim 14 , further including digitally controlling said attenuating of the reflected pulse according to signals received during respective noise dwells and data dwells to enable discrimination between noise and signals representing the reflected pulse. 
     
     
       16. The method of  claim 15 , including utilizing bit error rate to discriminate between noise and signals representing the reflected pulse. 
     
     
       17. A method of transmitting a carrier-based ultra wideband pulse, said method comprising:
 generating a low-level UWB pulse that includes an energy burst having a few cycles of RF energy at a defined carrier frequency; 
 wave filtering the energy burst to reject out-of-band emissions; and 
 radiating a carrier-based ultra wideband representation of said energy burst at said defined carrier frequency. 
 
     
     
       18. The method of  claim 17 , further comprising amplifying said energy burst prior to said radiating. 
     
     
       19. A method of transmitting a carrier-based ultra wideband pulse, said method comprising:
 generating an ultra wideband pulse that includes an energy burst having a few cycles of RF energy at a defined carrier frequency;   wave filtering the energy burst to reject out-of-band emissions; and   radiating a carrier-based ultra wideband representation of said energy burst at said defined carrier frequency.   
     
     
       20. A transmitter comprising:
 a generator configured to generate an ultra wideband pulse that includes an energy burst having a few cycles of RF energy at a defined carrier frequency;   a wave filter responsive to filter the energy burst to reject out-of-band emissions; and   an antenna responsive to radiate a carrier-based ultra wideband representation of said energy burst at said defined carrier frequency.   
     
     
       21. A transmitter comprising:
 a generator configured to generate an ultra-wideband signal characterized by a series of UWB pulses;   a wave filter responsive to filter said UWB pulses to define a center-frequency thereof; and   an antenna responsive to radiate a carrier-based representation of said UWB pulses at said defined center-frequency.   
     
     
       22. A carrier-based ultra-wideband transmitter comprising:
 a switched impulse generator to generate an ultra-wideband signal characterized by a series of ultra-wideband pulses, said switched impulse generator including one of an on-off switched oscillator, an oscillator having a time-gated dc bias that alternately biases the oscillator on and off, and an impulse-gated mixer that mixes an oscillator output;   a wave filter responsive to said switched impulse generator to filter said ultra-wideband pulses to define a center-frequency thereof; and   an antenna responsive to said filter to radiate a carrier-based representation of said ultra-wideband pulses at said defined center-frequency.   
     
     
       23. A carrier-based ultra-wideband transmitter comprising:
 a switched impulse generator to generate an ultra-wideband signal characterized by a series of ultra-wideband pulses, said switched impulse generator including an on-off switched oscillator;   a wave filter responsive to said switched impulse generator to filter said ultra-wideband pulses to define a center-frequency thereof; and   an antenna responsive to said filter to radiate a carrier-based representation of said ultra-wideband pulses at said defined center-frequency.   
     
     
       24. A carrier-based ultra-wideband transmitter comprising:
 a switched impulse generator to generate an ultra-wideband signal characterized by a series of ultra-wideband pulses, said switched impulse generator including an oscillator having a time-gated dc bias that alternately biases the oscillator on and off;   a wave filter responsive to said switched impulse generator to filter said ultra-wideband pulses to define a center-frequency thereof; and   an antenna responsive to said filter to radiate a carrier-based representation of said ultra-wideband pulses at said defined center-frequency.