Ultra high resolution ranging unit

• US 5,914,683 A
• Filed: 09/11/1997
• Issued: 06/22/1999
• Est. Priority Date: 09/12/1996
• Status: Expired due to Fees

• Current Assignee: Joe S O'Conner
• Original Assignee: Joe S O'Conner
• Inventors: O'Conner, Joe S.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/927,423
• Time in Patent Office: 649 Days
• Field of Search: 342/127, 342/128, 342/129, 342/135, 342/102, 342/103
• US Class Current: 342/127
• CPC Class Codes: G01S 13/342 using sinusoidal modulation
• CPC Class Codes: G01S 13/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 13/38 wherein more than one modulation frequency is used
• CPC Class Codes: G01S 7/352 Receivers
• CPC Class Codes: G01S 7/356 involving particularities of FFT processing

Abstract

A low cost, real time, remote sensor device for accurately measuring distance to an object with a resolution of 1 millimeter or better using phase information from either electromagnetic or acoustic energy. The device repetitiously transmits a swept frequency and decodes the resulting echo to produce a phase gate which is then converted to an accurate measurement of the range from each sweep. A method for measuring the time between two known phase points on a return signal is employed to determine the range measurement. Since the phase of the signal is used to determine range, the resolution is not dependent on bandwidth.

Claims

1. An ultra high resolution ranging unit comprising a transmitter for transmitting a swept frequency, a receiver for receiving an echo of the swept frequency, a decoder connected to the receiver for decoding the received echo and producing a phase gate, a converter connected to the decoder for comparing phases, and an indicator for indicating distant measurement according to the phases.

2. The apparatus of claim 1, wherein the transmitter is a frequency modulated continuous wave transmitter with a varactor tuner and a volt ramp connected to the varactor tuner for sweeping a transmitted frequency, and wherein the receiver includes an internal demodulator for demodulating the frequency modulated continuous wave echo.

3. The apparatus of claim 2, wherein the receiver further comprises an amplifier and a high bandpass filter connected to the amplifier and an automatic gain control connected to the high bandpass filter, a second amplifier connected to the automatic gain control and a bandpass filter connected to the second amplifier, a controller connected to the bandpass filter for controlling low frequency cutoff according to range, and a gate connected to the bandpass filter for eliminating unwanted flyback or reset signals.

4. The apparatus of claim 3, further comprising a splitter connected to the gate for splitting the signals into first and second channels, an analog-to-digital converter connected to the first channel, a first comparator connected to the converter for creating a pulse at a leading edge phase of each sinewave, a second comparator connected to the converter for creating a second pulse at a trailing edge of each sinewave, a monopulse generator connected to the first and second comparators for generating a fixed pulse from each pulse from the first and second comparators, and an adder connected to the monopulse generator for adding the pulses.

5. The apparatus of claim 4, further comprising first and second comparators connected to the converter for generating pulses at different positions on the sinewave.

6. The apparatus of claim 4, further comprising a phase locked loop circuit connected to the adder, a gate connected to the phase locked loop circuit for gating a phase air signal off during ramp flyback.

7. The apparatus of claim 6, wherein the phase locked loop circuit is connected to a low pass filter in the bandpass filter for adjusting low frequency cutoff.

8. The apparatus of claim 7, further comprising an amplifier connected to the second channel, low pass filters connected to the amplifier in the second channel, the low pass filters connected to the phase locked loop circuit in the first channel for adjusting upper cutoff of the low pass filters, the second channel having first and second comparators connected to the low pass filter, a monopulse generator connected to the first and second comparators, an adder connected to the monopulse generator and a second phase locked loop circuit connected to the adder in the second channel, a switch connected to the phase locked loop in the first channel and a switch connected to the phase locked loop in the second channel, and an output connected to the switch for switching output from the first channel to the second channel.

9. The apparatus of claim 8, further comprising a ranging switch connected to phase comparator outputs in the first and second channels, a start pulse generator connected to the ranging switch, a counter connected to the start pulse generator, a stop pulse generator connected to the counter, a range gate generator connected to the start pulse generator and the stop pulse generator, a range gate selector connected to the range gate generator, a timer connected to the range gate selector, and a range output connected to the timer.

10. The apparatus of claim 9, further comprising second and third counters connected to the ranging switch, second and third start pulse generators connected to the second and third counters respectively, second and third stop pulse generators connected to the second and third counters respectively, second and third range gate generators connected to the second and third start pulse generators and second and third stop pulse generators respectively and connected to the range gate selector.

11. The apparatus of claim 8, further comprising a ranging switch connected to the phase comparators in the first and second channels, a start pulse generator connected to the ranging switch, a monopulse generator connected to the start pulse generator, a range gate generator connected to the monopulse generator, a charge pump connected to the ranging switch and to the range gate generator, and a range output connected to the charge pump.

12. The apparatus of claim 8, further comprising a computer interface connected to the range output for displaying range and determining speed from rate of change of range.

13. Ultra high resolution ranging apparatus, comprising a radar module, a ramp generator connected to the radar module, an amplifier connected to the radar module, a waveform compensator connected to the amplifier and to the ramp generator, an automatic gain control connected to the amplifier, a second amplifier connected to the automated gain control, and a high pass tracking filter connected to the second amplifier, a gating circuit connected to the high pass tracking filter, a primary channel amplifier and a secondary channel amplifier connected to the gating circuit, a low pass tracking filter connected to the secondary channel amplifier, a first set of phase comparators connected to the primary channel amplifier and a second set of phase comparators connected to the low pass tracking filter, monopulse generators connected to the sets of phase comparators, monopulse phase comparators connected to the monopulse generators, phase locked loop circuits connected to the monopulse phase comparators, a VF converter connected to the phase locked loop comparator in the first channel and connected to the low pass tracking filter in the second channel, a switch connected to the phase locked loop circuit in the first channel and to the phase locked loop circuit in the second channel, and an output connected to the switch.

14. The apparatus of claim 13, further comprising a secondary channel automatic gain control connected to the amplifier and connected to the switch.

15. The apparatus of claim 13, further comprising a timing circuit connected to the ramp generator, and first and second phase locked loop gates connected to the timing generator and respectively connected to the primary channel phase locked loop circuit and the secondary channel phase locked loop circuit.

16. The apparatus of claim 13, further comprising a second switch connected to the first switch and connected to the monopulse phase comparators, first, second and third counters connected to the second switch, first, second and third start pulse generators connected to the first, second and third counters, first, second and third stop pulse generators connected to the first, second and third counters, first, second and third range gate generators connected to the first, second and third start pulse and stop pulse generators, a range gate selector connected to the range gate generators, a timer connected to the range gate selector, an ASCII generator connected to the timer, a computer interface connected to the ASCII generator, and a range output connected to the computer.

17. The apparatus of claim 13, further comprising a second switch connected to the first switch and connected to an AGC level detector which is connected to the secondary channel amplifier, the second switch being connected to the monopulse phase comparators in the primary and secondary channels, a start pulse generator connected to the second switch, a monopulse generator connected to the start pulse generator, a range gate generator connected to the monopulse generator, a charge pump connected to the second switch and to the range gate generator, and a range output connected to the charge pump.

18. The apparatus of claim 17, further comprising a computer interface connected to the range output.

19. A method of ultra high resolution ranging, comprising generating a frequency modulated continuous wave signal, sweeping the signal, transmitting the signal, receiving echo signals, high pass filtering and gating the echo signals, amplifying the gated signals in primary and secondary channels, low pass filtering the amplified signals in the secondary channel, creating phase comparator signals from the amplified and low passed signals in the primary and secondary channels, creating monopulse signals and phase preparing the monopulse signals and creating phase locked loop signals in the primary and secondary channel, controlling the low pass tracking filter with the phase locked loop signal from the primary channel, and switching output from the primary channel to the secondary channel.

20. The method of claim 19, further comprising providing timing signals for sweeping and for gating pulse locked loop circuits in the primary and secondary channels for avoiding flyback signals.

21. The method of claim 20, further comprising monopulse phase comparator signals from the first and second channels to a second switch, supplying signals from the second switch to first, second and third counters, generating first, second and third start pulses and stop pulses and generating first, second and third range gate signals with the start and stop pulses, selecting and timing selected range gate signals and providing the time signals to a computer for providing a range output and rate of change speed output.

22. The method of claim 20, further comprising providing signals from phase comparators in the primary channel and the secondary channel to a second switch, generating a start pulse with a signal from the second switch, generating a monopulse with the start pulse and generating a range gate signal with the monopulse, supplying the range gate signal and the signal from the switch to a charge pump and providing an output from the charge pump.