USRE31851E - Signal processing system - Google Patents
Signal processing system Download PDFInfo
- Publication number
- USRE31851E USRE31851E US06/583,352 US58335284A USRE31851E US RE31851 E USRE31851 E US RE31851E US 58335284 A US58335284 A US 58335284A US RE31851 E USRE31851 E US RE31851E
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- United States
- Prior art keywords
- signal
- velocity
- accordance
- coupled
- information signal
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
- G01S13/585—Velocity or trajectory determination systems; Sense-of-movement determination systems processing the video signal in order to evaluate or display the velocity value
- G01S13/586—Velocity or trajectory determination systems; Sense-of-movement determination systems processing the video signal in order to evaluate or display the velocity value using, or combined with, frequency tracking means
Definitions
- This invention generally relates to signal processing systems and, more particularly, to improving the accuracy and reliability of such a system which uses a velocity detector in the form of a microwave transceiver and which takes advantage of the Doppler effect to obtain an electrical velocity information signal.
- microwave transceivers which use the Doppler effect to determine velocity are well known. Such applications include, for example, vehicular speed detection employed by police officers to enforce highway speed limits and equipment such as farm implements wherein it is desirable to determine not only the velocity of the implement but also the distance or acreage that it has covered. By obtaining a precise velocity measurement, accurate distance and acreage measurements may be derived by conventional techniques.
- transceiver systems are particularly useful because they tend to be more accurate than conventional mechanically-driven systems because wheel slippage is not a factor.
- spurious signals may be generated even though the vehicle has stopped because of the system responding to vehicle vibrations, rustling leaves, blowing dirt, or the like.
- a new and improved system for processing an electrical velocity information signal in a velocity detecting system in which a detector means is utilized for developing the signal having a characteristic that varies systematically in accordance with the velocity of the object subject to detection.
- the system comprises converter means coupled to the detector means and responsive to the velocity information signal characteristic for developing an oscillatory signal having a frequency which varies in accordance with the velocity information signal characteristic.
- a tracking filter means having a variable center frequency and responsive to the oscillatory signal for filtering all frequencies other than the center frequency is provided, with the center frequency of the tracking filter means varying in accordance with the frequency of the oscillatory signal.
- Signal generating means are provided which are responsive to the frequency of the signal passed by the tracking filter for generating an output signal having a frequency which has a preset ratio relative to the center frequency.
- the signal generating means comprises a voltage-controlled oscillator means, having an input and an output, for generating a signal at the output which has a frequency that varies in accordance with the voltage applied to the input.
- a comparator means having first and second inputs is utilized, with the first comparator input being coupled to a storage means and the second comparator input being coupled to a reference voltage means, for comparing the voltages at the first and second comparator means inputs and developing a corresponding error voltage.
- Circuit means are coupled to the storage means for selectively charging and discharging the storage means.
- Switch means are coupled to the converter means, the voltage-controlled oscillator means, and the circuit means and are responsive to the first and second oscillatory signals for causing the circuit means to alternately charge and discharge the storage means, whereby the output signal of the voltage-controlled oscillator means has a frequency which is a preset ratio of the frequency of the converter output signals as controlled by the circuit means.
- FIG. 1 is an electrical schematic diagram of a portion of the circuitry of a preferred embodiment of a signal processing system constructed in accordance with the present invention and which includes the velocity detector, intermediate frequency amplification stages, level detectors, and converter stage;
- FIG. 2 is an electrical schematic circuit diagram of the remaining portion of a preferred embodiment of the invention, including the tracking filter and signal generating circuitry.
- FIGS. 1 and 2 in general, there is shown an improved system for processing an electrical velocity information signal.
- Detecting means 10 are utilized for developing an electrical information signal which has a characteristic (e.g. frequency) that varies systematically in accordance with (e.g. is directly proportional to, inversely proportional to, or the like) the velocity of an object subject to detection.
- the system may be mounted on a vehicle, for example, and the object may be the ground over which the vehicle is traversing.
- a signal such as a microwave signal is radiated from the vehicle to the ground and the reflected signal is received by detector 10 and here is developed an output electrical information signal which has a frequency equal to twice the velocity (in miles per hour) divided by the wavelength of the frequency being used.
- Detector 10 may therefore take the form of a commercially available system which operates on the so-called "X-band” (10.525 GHz) such as a model MA86656-A detector manufactured by Microwave Associates. Further information may be obtained from the book “Radar Handbook” by Merrill Skolnick, published by McGraw-Hill (1970).
- the characteristic of the detector's output signal that varies systematically in accordance with the velocity of the objects subject to detection need not necessarily be frequency.
- the output signal could be a DC voltage whose magnitude corresponds to velocity.
- the detector 10 may be operated in a "starved local oscillator injection" mode and thus achieve a marked increase in noise performance stability.
- a "starved local oscillator injection” mode by applying much less RF injection than that amount suggested by the microwave detector manufacturer, and adding to the mixer diode an amount of DC bias current (via resistors 12 and 13) to bring the mixer back to its typical operating point, the temperature stability of the RF sensitivity of the system is substantially improved.
- Converter means 30 are coupled to the output of detector means 10 at output terminal 11 and are responsive to the velocity information signal characteristic (i.e., frequency in the illustrated embodiment of the invention) for developing an oscillatory signal at the output terminal 31 of operational amplifier 32 having a frequency which varies in accordance with the velocity information signal characteristic.
- the converter means comprises an operational amplifier 32 biased as shown to effectively operate as a Schmitt Trigger circuit; that is, it is biased in a comparator configuration such that it has relatively close maximum and minimum input switching thresholds, coupled with a fast response time, resulting in its being easily overdriven to thus produce an amplified rectangular pulse signal output signal in response to a relatively wide range (magnitude) of sinusoidal or rectangular wave input signals.
- converter means 30 may take other forms such as a voltage-controlled oscillator to convert a signal having a voltage which is systematically related to velocity into a corresponding rectangular wave output signal without departing from the principles of the invention.
- the embodiment of the invention illustrated in FIG. 1 further includes amplifier means coupled between detector 10 and a tracking filter means 40, by way of converter means 30, for amplifying the electrical velocity information signal.
- the amplifying means includes a low-input-impedance amplifier 15, comprising a pair of amplifying transistors 16 and 17 connected as shown in FIG. 1.
- the low-input-impedance amplifier is used primarily for converting the current signal into a voltage signal and it provides impedance matching.
- the operation of amplifier 15 is described in greater detail in the aforementioned U.S. Pat. No. 3,895,384 patent.
- Low-input-impedance amplifier 15 is followed by an intermediate frequency (IF) amplifier 20, comprising a pair of operational amplifiers 21 and 22 which are available in integrated circuit form from National Semiconductor and commonly referred to as a "2904".
- IF intermediate frequency
- Operational amplifier 21 has a gain which is variable in response to the application of a control signal. Essentially, this is achieved in the illustrated embodiment of the invention by providing an external impedance in the form of a fixed resistor 23 coupled between the inverting input of operational amplifier 21 and ground via resistor 25 and capacitor 26.
- a switch means in the form of a bilateral switch 24 (available in integrated circuit form from RCA and commonly referred to as a "4066") which is responsive to a switching signal for selectively shorting and unshorting resistor 23.
- a bilateral switch 24 available in integrated circuit form from RCA and commonly referred to as a "4066"
- resistor 23 With resistor 23 shorted, the gain of operational amplifier 21 is relatively high; unshorted, relatively low.
- the switching signal is derived by a level detecting means in the form of a voltage level detector 35 which includes an operational amplifier 36, a peak detector formed by diode 37 and resistor 38a, and an integrator formed by resistor 38b and capacitor 39.
- Op amp 36 operates as a comparator to provide a level detecting means to generate the switching signal which actuates switch 24 to thus un-short the normally-shorted resistor 23 and thereby substantially decrease the gain (e.g., by a factor of five) of amplifier 21 when the velocity of the object being detected is essentially zero.
- the gain is thus decreased to a point where spurious signals, caused by vehicle vibration, rustling leaves, blowing dirt, or the like which might be generated while the vehicle is stopped, are not amplified sufficiently to operate the system.
- the output of comparator 36 is applied to the inverting input of another operational amplifier 101 as hereinafter described in greater detail.
- Tracking filter means 40 comprise a phase-locked loop 41 operated with a relatively long (e.g. 2 to 3 seconds) time constant which allows it to track the incoming frequency from terminal 31 but delays its response to rapid changes therein. In other words, both the attack (or “capture”) and release times of phase locked loop 41 to and from the so-called “locked” state are so slow as to allow the internal oscillator to run at approximately the average frequency of the input signal, but never actually "lock in”. Tracking filter 40 thus effectively operates as a high-Q filter which is responsive to the oscillatory signal from converter 30 for filtering all frequencies other than the center frequency (i.e., the frequency of the signal at terminal 31), with this center frequency varying in accordance with the frequency of the oscillatory signal at terminal 31.
- Tracking filter 40 thus effectively operates as a high-Q filter which is responsive to the oscillatory signal from converter 30 for filtering all frequencies other than the center frequency (i.e., the frequency of the signal at terminal 31), with this center frequency varying in accordance with the frequency of
- Phase locked loop 41 may be any suitable circuit such as a "4046 " integrated circuit available from RCA.
- Signal generating means are responsive to the frequency of the signal passed by the tracking filter for generating an output signal which is a preset ratio relative to the center frequency.
- the signal generating means comprises a voltage-controlled oscillator means 50, comparator means 60, charging/discharging circuit means 70, switching means 80, and a local oscillator means 90.
- Voltage-controlled oscillator means 50 includes a pair of operational amplifiers 51 and 52 and a bilateral switch 54 (e.g. a "4066") connected as shown for generating a signal at the output 53 which has a frequency that varies in accordance with the voltage applied to the inputs of op amp 52.
- a bilateral switch 54 e.g. a "4066"
- Comparator means 60 in the form of an op amp 61 biased to operate as a comparator is provided to develop an error voltage at output terminal 62 which is applied to both inputs of operational amplifier 52.
- Comparator 61 (which may advantageously take the form of an integrated circuit manufactured by RCA and commonly designated “3140") has first and second inputs 63 and 64, with input 63 coupled to a reference voltage source (generally designated throughout the drawings as "V" and which in the illustrated embodiment of the invention is a positive 8 volts) by means of a resistor capacitor network and with its second input 64 coupled to a storage means in the form of a storage capacitor 65.
- V reference voltage source
- Circuit means 70 are coupled to the storage capacitor 65 for selectively charging and discharging capacitor 65.
- the circuit means comprises a pair of bilateral switches 71 and 72 which are coupled to storage capacitor 65 by means of fixed resistor 73 and variable resistor 74, in the case of bilateral switch 71, and by fixed resistor 75, in the case of bilateral switch 72.
- Switches 71,72 are responsive to the output signals from a dual shift register 82 which is hereinafter described in greater detail.
- the output signals of dual shift register 82 (which may take the form of an integrated circuit manufactured by RCA and commonly referred to as a "4015") alternately actuate bilateral switches 71 and 72.
- Bilateral switch 71 is coupled between the inverting input of comparator 61 and ground so that when bilateral switch 71 is closed, capacitor 65 discharges at a rate determined by resistors 73 and 74.
- bilateral switch 72 is closed (and thus bilateral switch 71 is open)
- storage capacitor 65 is charged from reference voltage V at a rate determined by fixed resistor 75.
- a desired error voltage at output terminal 62 may be obtained which causes voltage-controlled oscillator means 50 to oscillate at a frequency which has a preset ratio relative to the frequency passed by tracking filter 40.
- this signal has a frequency which is a preset ratio relative to the velocity information signal developed by detector 10.
- the output signal at the circuit which may be taken at output terminal 53 of voltage-controlled oscillator 50, is essentially unaffected by environmental changes because the circuit of the invention effectively factors out such changes. For example, if an environmental change such as temperature were to increase the values of resistors 73 and 74, it would likewise increase the value of resistor 75. Thus, the resulting change in the rate of discharge of storage capacitor 65 would be offset by the resulting change in the rate of charge of storage capacitor 65.
- Switch means 80 comprising a dual flip-flop circuit 81 (which may take the form of an integrated circuit manufactured by RCA and commonly referred to as a "4013") and a dual shift register 82 (which was referred to hereinabove) are coupled to the converter means 30 by way of tracking filter 40, coupled to voltage-controlled oscillator 50 at output terminal 53 and coupled to circuit means 70 by way of bilateral switches 71, 72.
- the switch means 80 is responsive to the oscillatory signals from tracking filter 40 and voltage-controlled oscillator 50 for causing circuit means 70 to alternately charge and discharge storage capacitor 65, as discussed in greater detail above.
- the preferred embodiment of the invention illustrated in FIG. 2 further comprises a local oscillator means 90 which is coupled to the clock inputs (i.e., terminals 1 and 9) of the dual shift register 82 for providing a clock signal for the switch means 80, whereby each shift register is controlled by the same clock signal to further minimize the influence on the system by environmental changes.
- a single local oscillator circuit 90 to clock both shift registers of dual shift register 82, changes in the clock frequency caused by temperature, for example, will affect each shift register the same amount. Consequently, since one shift register controls the rate of discharge of capacitor 65 and the other controls the rate of charge of capacitor 65, changes in the local oscillator frequency are effectively cancelled.
- Local oscillator circuit 90 comprises an operational amplifier 91 having a timing capacitor 92 and associated biasing resistors connected as shown to provide a local oscillator signal at output terminal 93.
- the oscillator frequency of local oscillator circuit 90 is approximately 13 KHz, although it may range from 12 to 14 KHz so long as the drift is relatively slow, without adversely affecting the accuracy of the system.
- another advantage of the present invention is that it enables a relatively low cost oscillator circuit to be employed; that is, an oscillator circuit which need not be held to close tolerances with respect to its frequency of oscillation by means of a relatively expensive crystal or the like.
- Gating circuit 100 means in the form of gating circuit 100 are coupled to amplifying means 20 by way of bilateral switch 24 and operational amplifier 21 for externally applying a control signal, whereby the output signal may be blocked either manually or in response to the occurrence of a predetermined external event.
- Gating circuit 100 comprises an operational amplifier 101 utilized as a comparator and a switch 102 which may take the form of a manual switch on the vehicle control panel (not shown) or the form of a mechanical or electronic switch which is automatically actuated whenever the vehicular implement for which the system is being used (e.g. a sprayer, seed planter, harvester, etc.) is deactivated.
- switch 102 applies a positive voltage V to the inverting input terminal of op amp 101 to thereby inhibit the passage of the output signal at output terminal 53 of voltage-controlled oscillator 50 to the output terminal 103 of gating circuit 100.
- the output signal at terminal 103 may of course be used to operate a counting circuit to obtain calibrated velocity information, which in turn may be used to derive accurate distance and/or acreage information.
- the system of the invention effectively improves the signal-to-noise ratio and provides an output signal which is essentially unaffected by changes in environmental factors such as temperature and humidity.
- the system of the invention finds particular utility in connection with a microwave transceiver velocity detecting system which takes advantage of the well-known Doppler effect.
- Another feature of the invention provides for manual and/or automatic deactivation of the system without interfering with its operation. In other words, the system may be temporarily deactivated while a liquid sprayer or planter, for example, is temporarily deactivated without introducing errors because of the deactivation and subsequent reactivation.
Abstract
Description
Claims (24)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/583,352 USRE31851E (en) | 1977-08-04 | 1984-02-24 | Signal processing system |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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US82165177A | 1977-08-04 | 1977-08-04 | |
US06/583,352 USRE31851E (en) | 1977-08-04 | 1984-02-24 | Signal processing system |
Related Parent Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US82165177A Continuation | 1977-08-04 | 1977-08-04 | |
US06/008,057 Reissue US4359734A (en) | 1977-08-04 | 1979-01-31 | Signal processing system |
Publications (1)
Publication Number | Publication Date |
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USRE31851E true USRE31851E (en) | 1985-03-19 |
Family
ID=27078788
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US06/583,352 Expired - Lifetime USRE31851E (en) | 1977-08-04 | 1984-02-24 | Signal processing system |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5455588A (en) * | 1993-03-01 | 1995-10-03 | Lew; Hyok S. | Method for determining target velocity by measuring phase shift |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3465336A (en) * | 1968-05-09 | 1969-09-02 | Us Army | Doppler radar with clutter controlled filter channel |
US3599110A (en) * | 1970-03-31 | 1971-08-10 | Ibm | Self-clocking system having a variable frequency oscillator locked to leading edge of data and clock |
US3715751A (en) * | 1970-09-30 | 1973-02-06 | Raytheon Co | Digital speed gate for doppler radar |
US3885238A (en) * | 1969-11-24 | 1975-05-20 | Itt | Phase locked loop receiving system with improved signal acquisition |
US3895384A (en) * | 1973-04-23 | 1975-07-15 | Dickey John Corp | Distance measuring apparatus |
US4016568A (en) * | 1974-01-18 | 1977-04-05 | Matsushita Electric Industrial Co., Ltd. | Method and system for measuring doppler frequency shift of an echo |
US4020490A (en) * | 1974-11-20 | 1977-04-26 | Decatur Electronics, Inc. | Traffic radar and apparatus therefor |
US4052722A (en) * | 1975-09-15 | 1977-10-04 | Decatur Electronics, Inc. | Traffic radar and apparatus therefor |
US4072947A (en) * | 1976-11-11 | 1978-02-07 | Rca Corporation | Monotonically ranging FM-CW radar signal processor |
-
1984
- 1984-02-24 US US06/583,352 patent/USRE31851E/en not_active Expired - Lifetime
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3465336A (en) * | 1968-05-09 | 1969-09-02 | Us Army | Doppler radar with clutter controlled filter channel |
US3885238A (en) * | 1969-11-24 | 1975-05-20 | Itt | Phase locked loop receiving system with improved signal acquisition |
US3599110A (en) * | 1970-03-31 | 1971-08-10 | Ibm | Self-clocking system having a variable frequency oscillator locked to leading edge of data and clock |
US3715751A (en) * | 1970-09-30 | 1973-02-06 | Raytheon Co | Digital speed gate for doppler radar |
US3895384A (en) * | 1973-04-23 | 1975-07-15 | Dickey John Corp | Distance measuring apparatus |
US4016568A (en) * | 1974-01-18 | 1977-04-05 | Matsushita Electric Industrial Co., Ltd. | Method and system for measuring doppler frequency shift of an echo |
US4020490A (en) * | 1974-11-20 | 1977-04-26 | Decatur Electronics, Inc. | Traffic radar and apparatus therefor |
US4052722A (en) * | 1975-09-15 | 1977-10-04 | Decatur Electronics, Inc. | Traffic radar and apparatus therefor |
US4072947A (en) * | 1976-11-11 | 1978-02-07 | Rca Corporation | Monotonically ranging FM-CW radar signal processor |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5455588A (en) * | 1993-03-01 | 1995-10-03 | Lew; Hyok S. | Method for determining target velocity by measuring phase shift |
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Legal Events
Date | Code | Title | Description |
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AS | Assignment |
Owner name: FLEET CREDIT CORPORATION, A CORP. OF RI, RHODE ISL Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:DICKEY-JOHN CORPORATION, A CORP. OF DE;DICKEY-JOHN INTERNATIONAL, LTD., A CORP. OF CT;DICKEY-JOHN INTERNATIONAL, LTD., A CORP. OF DE;AND OTHERS;REEL/FRAME:005016/0010 Effective date: 19880419 |
|
AS | Assignment |
Owner name: DICKEY-JOHN CORPORATION Free format text: RELEASED BY SECURED PARTY;ASSIGNOR:FLEET CREDIT CORPORATION;REEL/FRAME:005650/0235 Effective date: 19910328 |
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AS | Assignment |
Owner name: FIRST BANK NATIONAL ASSOCIATION, MINNESOTA Free format text: SECURITY INTEREST;ASSIGNOR:DICKEY-JOHN CORPORATION;REEL/FRAME:007327/0153 Effective date: 19941115 |
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AS | Assignment |
Owner name: U.S. BANK NATIONAL ASSOCIATION F/K/A FIRST BANK NA Free format text: TERMINATION;ASSIGNOR:DICKEY-JOHN CORPORATION;REEL/FRAME:012153/0874 Effective date: 20010723 |