Microwave proximity sensor

• US 4,313,118 A
• Filed: 06/30/1980
• Issued: 01/26/1982
• Est. Priority Date: 06/30/1980
• Status: Expired due to Term

• Current Assignee: Noel M. Calvin
• Original Assignee: Noel M. Calvin
• Inventors: Calvin, Noel M.
• Primary Examiner(s): Lieberman, Eli
• Application Number:
  US06/164,805
• Time in Patent Office: 575 Days
• Field of Search: 343/701, 343/702, 343/703, 343/5 PD, 343/803, 343/820
• US Class Current: 343/701
• CPC Class Codes: G01B 15/00 Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons characterised by the use of optical techniques G01B9/00, G01B11/00
• CPC Class Codes: G01B 7/023 for measuring distance between sensor and object G01B7/082 and G01B7/102 take precedence
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G01S 7/032 Constructional details for solid-state radar subsystems

Abstract

An improved microwave proximity sensor including 1/4-wavelength folded dipole antenna performing the functions of a transmitting antenna, a receiving antenna, and a frequency determining element in a microwave oscillator.

Claims

1. A microwave proximity sensor comprising:

microwave oscillator means, said microwave oscillator means including 1/4-wavelength dipole antenna means connected to comprise tank circuit means, and further including microwave oscillator means coupled to said 1/4-wavelength dipole antenna means to function as lumped constant oscillator means, whereby said 1/4-wavelength dipole antenna means functions as a resonance frequency determining element for said microwave oscillator means, said 1/4-wavelength dipole antenna means being connected to radiate energy generated by said microwave oscillator means and to receive energy reflected back from reflective objects, the impedance of said 1/4-wavelength dipole antenna means being variable in response to the phase and amplitude of said reflected energy, and the power consumed by said microwave oscillator means being related to the impedance of said 1/4-wavelength dipole antenna means;

converter means for converting power to voltage whereby a voltage proportional to said power consumption of said microwave oscillator means is generated, said converter means comprising constant current source means connected to said oscillator means as a power supply therefor such that the voltage drop across said constant current source means is substantially proportional to the power consumption of said microwave oscillator means;

comparator means coupled to said constant current source means for producing output responsive to changes in said voltage;

pulse generator means coupled to said constant current source means, said pulse generator means producing pulses having a low duty cycle, for providing pulses to turn on said constant current source means; and

sample and hold circuit means coupled to said constant current source means such that the voltage output of said constant current source means is fed to said sample and hold circuit means, the latter being connected such that its output is connected to said comparator means.

2. A microwave proximity sensor comprising:

microwave oscillator means, said microwave oscillator means including 1/4-wavelength dipole antenna means connected to comprise tank circuit means, and further including microwave oscillator means coupled to said 1/4-wavelength dipole antenna means to function as lumped constant oscillator means, whereby said 1/4-wavelength dipole antenna means functions as a resonance frequency determining element for said microwave oscillator means, said 1/4-wavelength dipole antenna means being connected to radiate energy generated by said microwave oscillator means and to receive energy reflected back from reflective objects, the impedance of said 1/4-wavelength dipole antenna means being variable in response to the phase and amplitude of said reflected energy, and the power consumed by said microwave oscillator means being related to the impedance of said 1/4-wavelength dipole antenna means;

converter means for converting power to voltage whereby a voltage proportional to said power consumption of said microwave oscillator means is generated, said converter means comprising constant current source means connected to said oscillator means as a power supply therefor such that the voltage drop across said constant current source means is substantially proportional to the power consumption of said microwave oscillator means;

comparator means coupled to said constant current source means for producing output responsive to changes in said voltage;

pulse generator means coupled to said constant current source means, said pulse generator means producing pulses having a low duty cycle, for providing pulses to turn on said constant current source means;

sample and hold circuit means coupled to said constant current source means such that the voltage output of said constant current source means is fed to said sample and hold circuit means, the latter being connected such that its output is connected to said comparator means, said sample and hold circuit means comprising MOS field effect transistor means.