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EP0188906A1
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Ground velocity sensor with drop-out detection
Assignee: Deere and Co
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Filing: 1985-12-20
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Granted: —
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Expires: 2005-12-20
Abstract
Abstract A transmitter (22) emtis a signal at the frequency of an oscillator (32). A reference phase-locked loop (3 4 ) provides a corresponding reference velocity voltage (Vt). The reflected signal is received by a receiver (24) and processed by a second phase-locked loop (48) which provides a Doppler velocity votlage (Vr) which is corrected by subtracting (58) the reference voltage (Vt). In order to avoid spurious response by the second PLL (48) a drop-out detector (46) provides a drop-out signal (D/0) when the amplitude of the received signal (fr) is below a threshold (V th ). The drop-out signal causes a low-pass filter (52) in the second PLL (48) to hold its output unchanged for the duration of the drop-out. A digitally implemented embodiment is also disclosed.
Inventors
- 👤 James Joseph Phelan
- 👤 Garn Farley Penfold
- 👤 Larry Wayne Ferguson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 19:11
CPC Classifications
G; G01; G01P; G01P3/00; G01S; G01S15/00; G01S15/02; G01S15/50; G01S15/58; G01S15/60
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
98 words
In a velocity sensor for sensing the velocity of one object moving relative to another object, the velocity sensor having first means for determining velocity data from a velocity dependent frequency derived from a variable magnitude signal reflected from the one object and from a predetermined fixed frequency, and having second means for limiting the effect of reflected signal degradation upon derivation of the velocity data, the improvement wherein the variable magnitude reflected signal is received by an input of the second means and the second means has an output coupled to an input of the first means.
Claim 2
Dependent Claim
98 words
In a velocity sensor for sensing the velocity of one object moving relative to another object, the velocity sensor having first means for determining velocity data from a velocity dependent frequency derived from a variable magnitude signal reflected from the one object and from a predetermined fixed frequency, and having second means for limiting the effect of reflected signal degradation upon derivation of the velocity data, the improvement wherein the variable magnitude reflected signal is received by an input of the second means and the second means has an output coupled to an input of the first means.
Claim 3
Dependent Claim
105 words
The velocity sensor of claim 1, wherein the second means comprises: a drop-out detector for sensing fluctuations in the average magnitude of the reflected signal and for generating a drop--out signal only when the average magnitude is below a predetermined threshold; and the first means comprises a phase-locked-loop circuit responsive to the velocity dependent frequency for generating an output signal which varies in response to changes in the velocity dependent frequency and thus, to changes in object velocity, the phase-locked-loop circuit including hold means responsive to the dropout detector for preventing variations of the output signal when the drop-out detector is generating the first signal.
Claim 4
Dependent Claim
51 words
The velocity sensor of claim 2, wherein .the drop-out detector comprises: a rectifier for rectifying the reflected signal; and a comparator having a first input coupled to receive said predetermined threshold, a second input coupled to receive the rectified reflected signal and an output which is coupled to the hold means.
Claim 5
Dependent Claim
65 words
The velocity sensor of claim 2, wherein the drop-out detector comprises: a rectifier for rectifying the reflected signal; an averaging circuit for generating an average signal representing an average amplitude of the rectified signal; and a comparator having a first input coupled to receive said threshold, a second input coupled to receive the average signal and an output which is coupled to the hold means.
Claim 6
Dependent Claim
160 words
The velocity sensor of claim 2, wherein the phase--locked-loop circuit comprises: a phase comparator with one input coupled to receive the velocity dependent frequency, an output and another input; a voltage controlled oscillator with an output coupled to the other input of the phase comparator and an input; a switch having a first terminal coupled to the output of the phase comparator, a second terminal, and a third terminal coupled to receive the drop-out signal, the switch being operable to connect and disconnect the first and second terminals as a function of the drop-out signal which is applied to its third terminal; an integrator having an input coupled to the second terminal of the switch and having an output: and a summing amplifier having a first input coupled to receive the output of the phase comparator, a second input coupled to receive the output of the integrating amplifier and an output coupled to the input of the voltage controlled oscillator.
Claim 7
Dependent Claim
132 words
The velocity sensor of claim 1, comprising: a first circuit responsive to the fixed frequency for generating a first signal proportional to the fixed frequency; a drop-out detector for sensing fluctuations in the average magnitude of the reflected signal and for generating a drop--out signal only when the sensed magnitude is below a predetermined threshold; a second circuit responsive to the velocity dependent frequency for generating a second signal which varies in response to changes in the velocity dependent frequency, the second circuit including a hold circuit for preventing variation of the second signal in response to generation of the drop-out signal; and a third circuit for generating an output signal with a magnitude which is proportional to the object vehicle and which is a function of the first and second signals.
Claim 8
Dependent Claim
16 words
The velocity sensor of claim 6, wherein: the first and second circuits each comprise a phase-locked--loop.
Claim 9
Dependent Claim
51 words
The velocity sensor of claim 6, wherein the drop-out detector comprises: a rectifier for rectifying the reflected signal; and a comparator having a first input coupled to receive said predetermined threshold, a second input coupled to receive the rectified reflected signal and an output which is coupled to the hold circuit.
Claim 10
Dependent Claim
155 words
The velocity sensor of claim 6, wherein the second circuit comprises: a phase comparator with an input coupled to receive the reflected signal and an output; a voltage controlled oscillator with an output coupled to another input of the phase comparator and an input; a switch having a first terminal coupled to the output of the phase comparator, a second terminal, and a third terminal coupled to receive the drop-out signal, the switch being operable to connect and disconnect the first and second terminals as a function of the drop-out signal which is applied to the third terminal; an integrator having an input coupled to the second terminal of the switch and an output; and a summing amplifier having a first input coupled to receive the output of the phase comparator, a second input coupled to receive the output of the integrating amplifier and an output coupled to the input of the voltage controlled oscillator.
Claim 11
Dependent Claim
107 words
The velocity sensor of claim 1, wherein: the first means comprises a first counter receiving the velocity dependent frequency, the first counter establishing a variable length time period corresponding to a predetermined number of cycles of the velocity dependent frequency and a second counter receiving the fixed frequency, the second counter counting at said fixed frequency for said established time period, the contents of said second counter at the end of said time period being indicative of the object velocity; and the second means comprises a drop-out circuit for inhibiting the first and second counters when a magnitude of the reflected signal drops below a predetermined threshold.
Claim 12
Dependent Claim
134 words
The velocity sensor of claim 10, further comprising: a flip-flop with a clock input coupled to receive the velocity dependent frequency, a set input, and a 0 output, the second counter having an inhibit input coupled to the Q output of the flip-flop and a clock input coupled to receive the fixed frequency; and the first counter having an inhibit input coupled to the Q output of the flip-flop, a clock input coupled to receive the velocity dependent frequency and a 0-out terminal coupled to the set input of the flip-flop, the 0-out terminal changing state at the end of said time period so that in response, the flip-flop Q output and the inhibit inputs change from a first state to a second state, thereby preventing further counting of the first and second counters.
Claim 13
Dependent Claim
113 words
The velocity sensor of claim 11, further comprising: a first monostable multivibrator having an input coupled to the 0-out terminal of the first counter and having an output; and a second monostable multivibrator having an input coupled to the output of the first monostable and having an output, the first and second counters each having a preset input coupled to the output of the second monostable, the state change of the 0-out of the first counter causing the first monostable to fire, which, in turn, causes the second monostable to fire, the firing of the second monostable causing the first and second counters to be reset to first and second initial values, respectively.
Claim 14
Dependent Claim
56 words
The velocity sensor of claim 12, further comprising: a latch with data inputs coupled to receive the contents of the second counter and with a read input coupled to the output of the first monostable so that firing of the first monostable causes the latch to read and store therein the contents of the second counter.
Claim 15
Dependent Claim
41 words
The velocity sensor of claim 13, wherein: the second monostable is triggered to begin firing at the end of the firing period of the first monostable so that the latch reads the second counter contents before the second counter is reset.
Claim 16
Dependent Claim
120 words
The velocity sensor of claim 12, further comprising: an OR gate with a first input coupled to the output of the second monostable, with an output coupled to the preset inputs of the first and second counters, and with a second input; a resistor coupled between ground and the second OR gate input; a switched terminal which is energized when system power is turned on; and a capacitor coupled between the second input of the OR gate and said switched terminal so that when the switched terminal is energized, a momentary signal is transmitted through the capacitor and OR gate to the preset inputs to thereby reset the first and second counters to their initial values upon system power turn-on.
Claim 17
Dependent Claim
30 words
The velocity sensor of claim 11, wherein the drop-out circuit comprises: a sensing circuit for generating a drop-out signal when a magnitude of the reflected signal drops below the threshold.
Claim 18
Dependent Claim
48 words
The velocity sensor of claim 16, wherein: the flip-flop has a data input coupled to receive the drop-out signal so that on the next cycle of the velocity dependent frequency, the drop-out signal forces the Q output of the flip-flop to the second state, thereby inhibiting both counters.
Claim 19
Dependent Claim
55 words
The velocity sensor of claim 1, wherein: the first means comprises period measuring means for measuring the period of a predetermined number of cycles of said velocity dependent frequency; and the second means includes means for preventing the measured period from being influenced when the reflected signal has a magnitude which falls below a threshold.
Claim 20
Dependent Claim
43 words
The velocity sensor of claim 18, wherein the period measuring means comprises: a first counter counting said predetermined number of cy- cles at a rate equal to the velocity dependent frequency; and a second counter counting at a constant rate for said period.
Claim 21
Dependent Claim
41 words
The velocity sensor of claim 19, further comprising: memory means for storing the contents of the second counter, the velocity sensor operating so that the second counter contents are stored in the memory means at the end of every measured period.
Claim 22
Dependent Claim
37 words
The velocity sensor of claim 19, wherein the means for preventing comprises: means for comparing a magnitude of the reflected signal to the threshold and for generating a drop-out signal when the magnitude falls below the threshold.
Claim 23
Dependent Claim
73 words
The velocity sensor of claim 21, wherein the means for preventing further comprises: a bistable circuit having a dock input coupled to receive the reflected signal, having a data input coupled to receive the drop-out signal and having an output coupled to inhibit inputs of both the first and second counters, generation of a drop-out signal forcing the bistable output to a known state which prevents the first and second counters from counting.
Claim 24
Dependent Claim
52 words
The velocity sensor of claim 22, wherein: the first counter has an output which changes state at the end of said period, the bistable circuit also having a set input coupled to the first counter output so that the bistable output changes to said known state at the end of said penod.
Claim 25
Dependent Claim
40 words
The velocity sensor of claim 23, wherein: the first and second counters each have preset inputs which cause the first and second counters to be initialized to predetermined first and second numbers, respectively, when a preset signal is applied thereto.
Claim 26
Dependent Claim
54 words
The velocity sensor of claim 24, further comprising: a first monostable having an input coupled to the first counter input and having an output; and a second monostable having an input coupled to the output of the first monostable and having an output coupled to the preset inputs of the first and second counters.
Claim 27
Dependent Claim
34 words
The velocity sensor of claim 25, further comprising: a latch for receiving and storing the contents of the second counter, the latch having a read input coupled to the output of the first monostable.
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