US5757320A — Short range, ultra-wideband radar with high resol…

Claim 1

Independent Claim 181 words

An apparatus for detecting a characteristic of objects within a field, comprising: a transmitter, including a shielded transmit cavity and a transmit antenna within the shielded transmit cavity, which transmits a sequence of electromagnetic pulses in response to a transmit timing signal; a receiver, including a shielded receive cavity adjacent to the transmit cavity and a receive antenna within the shielded receive cavity, and a differential sampler having a first input connected to the receive antenna and a second input connected to ground, which samples echoes from objects within the field of the sequence of electromagnetic pulses with controlled timing, in response to a receive timing signal, and generates a sample signal in response to the samples, the sample signal indicating a characteristic of objects within the field; a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the echoes such that time between transmission of pulses in the sequence and sampling by the receiver sweeps over a range of delays.

Claim 2

Independent Claim 181 words

An apparatus for detecting a characteristic of objects within a field, comprising: a transmitter, including a shielded transmit cavity and a transmit antenna within the shielded transmit cavity, which transmits a sequence of electromagnetic pulses in response to a transmit timing signal; a receiver, including a shielded receive cavity adjacent to the transmit cavity and a receive antenna within the shielded receive cavity, and a differential sampler having a first input connected to the receive antenna and a second input connected to ground, which samples echoes from objects within the field of the sequence of electromagnetic pulses with controlled timing, in response to a receive timing signal, and generates a sample signal in response to the samples, the sample signal indicating a characteristic of objects within the field; a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the echoes such that time between transmission of pulses in the sequence and sampling by the receiver sweeps over a range of delays.

Claim 3

Dependent Claim 39 words

The apparatus of claim 1, wherein the delays in the range of delays over which the timing circuit sweeps the time between transmission of pulses in the sequence and sampling by the receiver vary by less than 100 nanoseconds.

Claim 4

Dependent Claim 18 words

The apparatus of claim 2, wherein delays in the range of delays vary by less than 10 nanoseconds.

Claim 5

Dependent Claim 55 words

The apparatus of claim 1, wherein the transmit timing signal causes the transmitter to transmit the sequence of electromagnetic pulses at a consistent pulse repetition rate to define a time between pulses, and the time between pulses is greater than difference in the delays at the beginning and the end of the range of delays.

Claim 6

Dependent Claim 71 words

The apparatus of claim 1, wherein the transmit timing signal causes the transmitter to transmit the sequence of electromagnetic pulses at a pulse repetition rate, and wherein the receive timing signal sweeps over the range of delays in a sweep cycle such that echoes are sampled at the pulse repetition rate and with different delays in the range of delays, such that the sample signal represents received echoes in equivalent time.

Claim 7

Dependent Claim 20 words

The apparatus of claim 5, wherein the differential sampler for cancelling background noise is positioned in the shielded receive cavity.

Claim 8

Dependent Claim 20 words

The apparatus of claim 5, wherein the sweep cycle is repeated at a sweep rate of less than 16 kiloHertz.

Claim 9

Dependent Claim 20 words

The apparatus of claim 5, wherein the sweep cycle is repeated at a sweep rate of less than 100 Hertz.

Claim 10

Dependent Claim 16 words

The apparatus of claim 7, wherein the pulse repetition rate is greater than about 1 megaHertz.

Claim 11

Dependent Claim 63 words

The apparatus of claim 1, wherein the differential sampler comprises a first sampling gate having an output and an input coupled to the antenna, a second sampling gate having an output and an input coupled to ground, and a differential amplifier having a first input coupled to the first sampling gate output and a second input coupled to the second sampling gate output.

Claim 12

Dependent Claim 26 words

The apparatus of claim 1, wherein the transmit waveguide cavity, and the receive waveguide cavity are separated by a conductive wall to reduce main bang coupling.

Claim 13

Dependent Claim 26 words

The apparatus of claim 1, including a shielding base, and wherein the transmit waveguide cavity and the receive waveguide cavity are mounted on the shielding base.

Claim 14

Dependent Claim 24 words

The apparatus of claim 1, wherein the sequence of electromagnetic pulses comprises a plurality of bursts of electromagnetic energy having a nominal center frequency.

Claim 15

Dependent Claim 25 words

The apparatus of claim 1, wherein the sequence of electromagnetic pulses comprises a plurality of impulses of electromagnetic energy having a wide band frequency characteristic.

Claim 16

Dependent Claim 37 words

The apparatus of claim 1, wherein the transmit antenna is a resistively loaded monopole antenna mounted in the transmit waveguide cavity, and the receive antenna is a resistively loaded monopole antenna mounted in the receive waveguide cavity.

Claim 17

Dependent Claim 30 words

The apparatus of claim 15, wherein the transmitter includes a transmit pulse generator, and circuitry which AC couples the antenna mounted in the transmit waveguide to the transmit pulse generator.

Claim 18

Dependent Claim 42 words

The apparatus of claim 15, wherein the receiver waveguide and the transmit waveguide are coupled to a shared ground plane, the receiver includes circuitry which isolates the antenna mounted in the receive waveguide from low frequency residual currents in the receive waveguide.

Claim 19

Dependent Claim 29 words

The apparatus of claim 1, including a fiducial object in the field which produces an echo at a known position in the field for calibration of the sample signal.

Claim 20

Dependent Claim 27 words

The apparatus of claim 1, wherein the timing circuitry includes circuitry for dithering the pulse repetition rate to reduce interference from other electromagnetic sources in the field.

Claim 21

Dependent Claim 182 words

A swept range gate radar for detecting characteristics of objects within a field, comprising: a transmitter, including a shielded transmit cavity and a transmit antenna within the shielded transmit cavity, which transmits a sequence of electromagnetic pulses from the transmit antenna into the field in response to a transmit timing signal; a receiver, including a shielded receive cavity adjacent the transmit cavity and a receive antenna within the shielded receive cavity, which samples echoes from objects in the field of the sequence of electromagnetic pulses with controlled timing, in response to a receive timing signal, and generates a sample signal in response to the samples; a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the echoes such that time between transmission of pulses in the sequence by the transmitter and sampling by the receiver sweeps over a range of delays; and a signal processor, coupled with the receiver, to indicate a characteristic of the object in response to the sample signal.

Claim 22

Dependent Claim 182 words

A swept range gate radar for detecting characteristics of objects within a field, comprising: a transmitter, including a shielded transmit cavity and a transmit antenna within the shielded transmit cavity, which transmits a sequence of electromagnetic pulses from the transmit antenna into the field in response to a transmit timing signal; a receiver, including a shielded receive cavity adjacent the transmit cavity and a receive antenna within the shielded receive cavity, which samples echoes from objects in the field of the sequence of electromagnetic pulses with controlled timing, in response to a receive timing signal, and generates a sample signal in response to the samples; a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the echoes such that time between transmission of pulses in the sequence by the transmitter and sampling by the receiver sweeps over a range of delays; and a signal processor, coupled with the receiver, to indicate a characteristic of the object in response to the sample signal.

Claim 23

Dependent Claim 48 words

The radar of claim 20, wherein the signal processor comprises a counter which counts at a count rate from a beginning of the sweep until the sample signal reaches a threshold, and generates a counter output indicating a position of a source of an echo in the field.

Claim 24

Dependent Claim 41 words

The radar of claim 20, wherein the timing circuit includes a voltage controlled delay circuit having a control input, and a voltage ramp generator coupled to the control input of the voltage controlled delay circuit to sweep the receive timing signal.

Claim 25

Dependent Claim 16 words

The radar of claim 22, wherein the voltage ramp generator comprises a digital to analog converter.

Claim 26

Dependent Claim 36 words

The radar of claim 22, wherein the voltage ramp generator comprises an analog exponential ramp generator, and the voltage controlled delay circuit produces a delay which is an exponential function of voltage on the control input.

Claim 27

Dependent Claim 72 words

The radar of claim 20, wherein the transmit timing signal causes the transmitter to transmit the sequence of electromagnetic pulses at a pulse repetition rate, and wherein the receive timing signal sweeps over the range of delays in a sweep cycle such that echoes are sampled at the pulse repetition rate and with different delays in the range of delays, such that the sample signal represents the received echoes in equivalent time.

Claim 28

Dependent Claim 21 words

The radar of claim 25, wherein the sweep cycle is repeated at a sweep rate of less than about 16 kiloHertz.

Claim 29

Dependent Claim 20 words

The radar of claim 25, wherein the sweep cycle is repeated at a sweep rate of less than 100 Hertz.

Claim 30

Dependent Claim 16 words

The radar of claim 26, wherein the pulse repetition rate is greater than about 1 megaHertz.

Claim 31

Dependent Claim 49 words

The radar of claim 20, wherein the receiver includes a first sampling gate coupled to the receive antenna, a second sampling gate coupled to ground and a differential amplifier having a first input coupled to the first sampling gate and a second input coupled to the second sampling gate.

Claim 32

Dependent Claim 26 words

The radar of claim 29, including a shielding base, and wherein the shielded transmit cavity and the shielded receive cavity are mounted on the shielding base.

Claim 33

Dependent Claim 24 words

The radar of claim 20, wherein the sequence of electromagnetic pulses comprises a plurality of bursts of electromagnetic energy having a nominal center frequency.

Claim 34

Dependent Claim 25 words

The radar of claim 30, wherein the sequence of electromagnetic pulses comprises a plurality of impulses of electromagnetic energy having a wide band frequency characteristic.

Claim 35

Dependent Claim 25 words

The radar of claim 20, wherein the transmit antenna comprises a resistively loaded monopole antenna, and the receive antenna comprises a resistively loaded monopole antenna.

Claim 36

Dependent Claim 32 words

The radar of claim 33, wherein the transmitter includes a transmit pulse generator, and circuitry which AC couples the transmit antenna mounted in the shielded transmit cavity to the transmit pulse generator.

Claim 37

Dependent Claim 41 words

The radar of claim 33, wherein the shielded receive cavity and the shielded transmit cavity are coupled to a shared ground plane, the receiver includes circuitry which isolates the receive antenna from low frequency residual currents in the shielded receive cavity.

Claim 38

Dependent Claim 29 words

The radar of claim 20, including a fiducial object in the field which produces an echo at a known position in the field for calibration of the sample signal.

Claim 39

Dependent Claim 27 words

The radar of claim 30, wherein the timing circuitry includes circuitry for dithering the transmit timing signal to reduce interference from other electromagnetic sources in the field.

Claim 40

Dependent Claim 283 words

A swept range gate radar for detecting characteristics of objects within a range of less than 20 feet, comprising: a transmitter, including a shielded transmit cavity and a resistively loaded transmit antenna within the shielded transmit cavity, which transmits a sequence of radio frequency (RF) pulses from the transmit antenna into the field in response to a transmit timing signal having a transmit pulse repetition rate of greater than 1 megaHertz; a receiver, including a shielded receive cavity, a resistively loaded receive antenna within the shielded receive cavity, a first sampling gate coupled to the receive antenna, a second sampling gate coupled to ground and a differential amplifier having a first input coupled to the first sampling gate and a second input coupled to the second sampling gate, which samples echoes from objects in the field of the sequence of RF pulses with controlled timing in the first and second sampling gates, in response to a receive timing signal, and generates a sample signal in response to the samples; a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the echoes such that time between transmission of pulses in the sequence by the transmitter and sampling by the receiver sweeps over a range of delays in a sweep cycle such that echoes are sampled at the pulse repetition rate and with different delays in the range of delays, such that the sample signal represents the received echoes in equivalent time; and a signal processor, coupled with the receiver, to indicate a characteristic of objects in the range in response to the sample signal.

Claim 41

Dependent Claim 283 words

A swept range gate radar for detecting characteristics of objects within a range of less than 20 feet, comprising: a transmitter, including a shielded transmit cavity and a resistively loaded transmit antenna within the shielded transmit cavity, which transmits a sequence of radio frequency (RF) pulses from the transmit antenna into the field in response to a transmit timing signal having a transmit pulse repetition rate of greater than 1 megaHertz; a receiver, including a shielded receive cavity, a resistively loaded receive antenna within the shielded receive cavity, a first sampling gate coupled to the receive antenna, a second sampling gate coupled to ground and a differential amplifier having a first input coupled to the first sampling gate and a second input coupled to the second sampling gate, which samples echoes from objects in the field of the sequence of RF pulses with controlled timing in the first and second sampling gates, in response to a receive timing signal, and generates a sample signal in response to the samples; a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, the receive timing signal causing the receiver to sample the echoes such that time between transmission of pulses in the sequence by the transmitter and sampling by the receiver sweeps over a range of delays in a sweep cycle such that echoes are sampled at the pulse repetition rate and with different delays in the range of delays, such that the sample signal represents the received echoes in equivalent time; and a signal processor, coupled with the receiver, to indicate a characteristic of objects in the range in response to the sample signal.

Claim 42

Dependent Claim 48 words

The radar of claim 38, wherein the signal processor comprises a counter which counts at a count rate from a beginning of the sweep until the sample signal reaches a threshold, and generates a counter output indicating a position of a source of an echo in the field.

Claim 43

Dependent Claim 41 words

The radar of claim 38, wherein the timing circuit includes a voltage controlled delay circuit having a control input, and a voltage ramp generator coupled to the control input of the voltage controlled delay circuit to sweep the receive timing signal.

Claim 44

Dependent Claim 16 words

The radar of claim 40, wherein the voltage ramp generator comprises a digital to analog converter.

Claim 45

Dependent Claim 36 words

The radar of claim 40, wherein the voltage ramp generator comprises an analog exponential ramp generator, and the voltage controlled delay circuit produces a delay which is an exponential function of voltage on the control input.

Claim 46

Dependent Claim 21 words

The radar of claim 42, wherein the sweep cycle is repeated at a sweep rate of less than about 16 kiloHertz.

Claim 47

Dependent Claim 20 words

The radar of claim 42, wherein the sweep cycle is repeated at a sweep rate of less than 100 Hertz.

Claim 48

Dependent Claim 26 words

The radar of claim 38, including a shielding base, and wherein the shielded transmit cavity and the shielded receive cavity are mounted on the shielding base.

Claim 49

Dependent Claim 24 words

The radar of claim 38, wherein the sequence of RF pulses comprises a plurality of bursts of RF energy having a nominal center frequency.

Claim 50

Dependent Claim 25 words

The radar of claim 38, wherein the sequence of RF pulses comprises a plurality of impulses of RF energy having a wide band frequency characteristic.

Claim 51

Dependent Claim 25 words

The radar of claim 38, wherein the transmit antenna comprises a resistively loaded monopole antenna, and the receive antenna comprises a resistively loaded monopole antenna.

Claim 52

Dependent Claim 32 words

The radar of claim 48, wherein the transmitter includes a transmit pulse generator, and circuitry which AC couples the transmit antenna mounted in the shielded transmit cavity to the transmit pulse generator.

Claim 53

Dependent Claim 41 words

The radar of claim 38, wherein the shielded receive cavity and the shielded transmit cavity are coupled to a shared ground plane, the receiver includes circuitry which isolates the receive antenna from low frequency residual currents in the shielded receive cavity.

Claim 54

Dependent Claim 29 words

The radar of claim 38, including a fiducial object in the field which produces an echo at a known position in the field for calibration of the sample signal.

Claim 55

Dependent Claim 27 words

The radar of claim 38, wherein the timing circuitry includes circuitry for dithering the pulse repetition rate to reduce interference from other electromagnetic sources in the field.

Claim 56

Independent Claim 203 words

A method for detecting a characteristic of an object within a field, comprising: generating a transmit timing signal; switching a transistor coupled to an antenna to produce the sequence of pulses, the transistor switches an output node coupled to the antenna less than 9 volts in amplitude, and in less than one nanosecond on the antenna in response to the transmit timing signal, to transmit a sequence of electromagnetic pulses to the field with controlled timing at a pulse repetition rate; generating a receive timing signal; switching a transistor coupled to a sample gate in response to the receive timing signal, the transistor switching an output coupled to the sampling gate less than 9 volts in amplitude, and in less than one nanosecond on the sample gate in response to the receive timing signal, to sample echoes of the sequence of electromagnetic pulses after reflection by the object to produce samples with controlled timing, so that time between the transmitting of pulses in the sequence and the sampling of echoes sweeps repeatedly over a range of delays; and producing a signal in response to an accumulation of the samples in a capacitance during the range of delays, indicating the characteristic of the object.

Claim 57

Independent Claim 203 words

A method for detecting a characteristic of an object within a field, comprising: generating a transmit timing signal; switching a transistor coupled to an antenna to produce the sequence of pulses, the transistor switches an output node coupled to the antenna less than 9 volts in amplitude, and in less than one nanosecond on the antenna in response to the transmit timing signal, to transmit a sequence of electromagnetic pulses to the field with controlled timing at a pulse repetition rate; generating a receive timing signal; switching a transistor coupled to a sample gate in response to the receive timing signal, the transistor switching an output coupled to the sampling gate less than 9 volts in amplitude, and in less than one nanosecond on the sample gate in response to the receive timing signal, to sample echoes of the sequence of electromagnetic pulses after reflection by the object to produce samples with controlled timing, so that time between the transmitting of pulses in the sequence and the sampling of echoes sweeps repeatedly over a range of delays; and producing a signal in response to an accumulation of the samples in a capacitance during the range of delays, indicating the characteristic of the object.

Claim 58

Dependent Claim 36 words

The method of claim 53, including in the step of switching a transistor coupled to an antenna to produce the sequence of pulses, biasing the transistor for non-avalanche switching in response to the transmit timing signal.

Claim 59

Dependent Claim 37 words

The method of claim 53, including in the step of switching a transistor coupled to a sample gate to produce the sequence of pulses, biasing the transistor for non-avalanche switching in response to the receive timing signal.

Claim 60

Dependent Claim 16 words

The method of claim 53, including dithering the transmit timing signal and the receive timing signal.

Claim 61

Independent Claim 153 words

An apparatus for detecting a characteristic of objects within a field, comprising: a transmitter which transmits a sequence of electromagnetic pulses in response to a transmit timing signal, the transmitter including a transistor coupled to the antenna, the transistor biased in a non-avalanche switching region, and supplying transmit pulses to the antenna; a receiver which samples echoes from objects within the field of the sequence of electromagnetic pulses with controlled timing, in response to a receive timing signal, and generates a sample signal in response to an accumulation of the samples, the sample signal indicating a characteristic of objects within the field, and a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, to cause the receiver to sample the echoes such that time between transmission of pulses in the sequence and sampling by the receiver sweeps over a range of delays.

Claim 62

Independent Claim 153 words

An apparatus for detecting a characteristic of objects within a field, comprising: a transmitter which transmits a sequence of electromagnetic pulses in response to a transmit timing signal, the transmitter including a transistor coupled to the antenna, the transistor biased in a non-avalanche switching region, and supplying transmit pulses to the antenna; a receiver which samples echoes from objects within the field of the sequence of electromagnetic pulses with controlled timing, in response to a receive timing signal, and generates a sample signal in response to an accumulation of the samples, the sample signal indicating a characteristic of objects within the field, and a timing circuit which supplies the transmit timing signal to the transmitter and supplies the receive timing signal to the receiver, to cause the receiver to sample the echoes such that time between transmission of pulses in the sequence and sampling by the receiver sweeps over a range of delays.

Claim 63

Dependent Claim 29 words

The apparatus of claim 57, including circuitry for dithering the transmit timing signal and the receive timing signal rate to reduce interference from other electromagnetic sources in the field.

Claim 64

Dependent Claim 20 words

The apparatus of claim 57, wherein the transistor coupled to the antenna has a switching speed of about 0.1 nanoseconds.

Claim 65

Dependent Claim 60 words

The apparatus of claim 57, wherein the receiver includes: a sample diode coupled to an antenna adapted to receive echoes, the sample diode also coupled to receive the receive timing signal; a sample holding capacitor coupled between the diode and a reference voltage which accumulates a plurality of samples over time; and an amplifier, coupled to the sample holding capacitor.

Claim 66

Dependent Claim 39 words

The apparatus of claim 57, wherein the delays in the range of delays over which the timing circuit sweeps the time between transmission of pulses in the sequence and sampling by the receiver vary by less than 100 nanoseconds.

Claim 67

Dependent Claim 18 words

The apparatus of claim 61, wherein delays in the range of delays vary by less than 10 nanoseconds.

Claim 68

Dependent Claim 55 words

The apparatus of claim 57, wherein the transmit timing signal causes the transmitter to transmit the sequence of electromagnetic pulses at a consistent pulse repetition rate to define a time between pulses, and the time between pulses is greater than difference in the delays at the beginning and the end of the range of delays.

Claim 69

Dependent Claim 71 words

The apparatus of claim 57, wherein the transmit timing signal causes the transmitter to transmit the sequence of electromagnetic pulses at a pulse repetition rate, and wherein the receive timing signal sweeps over the range of delays in a sweep cycle such that echoes are sampled at the pulse repetition rate and with different delays in the range of delays, such that the sample signal represents received echoes in equivalent time.

Claim 70

Dependent Claim 15 words

The apparatus of claim 64, wherein the receiver includes a differential sampler canceling background noise.

Claim 71

Dependent Claim 20 words

The apparatus of claim 64, wherein the sweep cycle is repeated at a sweep rate of less than 16 kilohertz.

Claim 72

Dependent Claim 20 words

The apparatus of claim 64, wherein the sweep cycle is repeated at a sweep rate of less than 100 Hertz.

Claim 73

Dependent Claim 16 words

The apparatus of claim 67, wherein the pulse repetition rate is greater than about 1 megahertz.

Claim 74

Dependent Claim 65 words

The apparatus of claim 57, wherein the receiver includes an antenna, a first sampling gate having an output and an input coupled to the antenna, a second sampling gate having an output and an input coupled to the antenna, and a differential amplifier having a first input coupled to the first sampling gate output and a second input coupled to the second sampling gate output.

Claim 75

Dependent Claim 52 words

The apparatus of claim 69, wherein the first and second sampling gates include respective diodes connected between the antenna and the timing circuit to receive the echoes from the antenna and the receive timing signal from the timing circuit, and respective sample holding capacitors coupled between the antenna and a reference potential.

Claim 76

Dependent Claim 24 words

The apparatus of claim 57, wherein the sequence of electromagnetic pulses comprises a plurality of bursts of electromagnetic energy having a nominal center frequency.

Claim 77

Dependent Claim 25 words

The apparatus of claim 57, wherein the sequence of electromagnetic pulses comprises a plurality of impulses of electromagnetic energy having a wide band frequency characteristic.

Claim 78

Dependent Claim 35 words

The apparatus of claim 57, wherein the transmitter includes a resistively loaded monopole antenna mounted in a transmit waveguide cavity, and the receiver includes a resistively loaded monopole antenna mounted in a receive waveguide cavity.

Claim 79

Dependent Claim 42 words

The apparatus of claim 73, wherein the receiver waveguide and the transmit waveguide are coupled to a shared ground plane, the receiver includes circuitry which isolates the antenna mounted in the receive waveguide from low frequency residual currents in the receive waveguide.

Claim 80

Dependent Claim 29 words

The apparatus of claim 57, including a fiducial object in the field which produces an echo at a known position in the field for calibration of the sample signal.

Claim 81

Dependent Claim 27 words

The apparatus of claim 57, wherein the timing circuitry includes circuitry for dithering the pulse repetition rate to reduce interference from other electromagnetic sources in the field.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2001-05-25	2001-11-24	2002-05-26	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2005-05-25	2005-11-24	2006-05-26	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2009-05-25	2009-11-24	2010-05-26	$7700.00	Window Closed / Lapsed

Short range, ultra-wideband radar with high resolution swept range gate

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