GB1268896A - Electrical detecting means - Google Patents
Electrical detecting meansInfo
- Publication number
- GB1268896A GB1268896A GB1877970A GB1877970A GB1268896A GB 1268896 A GB1268896 A GB 1268896A GB 1877970 A GB1877970 A GB 1877970A GB 1877970 A GB1877970 A GB 1877970A GB 1268896 A GB1268896 A GB 1268896A
- Authority
- GB
- United Kingdom
- Prior art keywords
- transistor
- repetition rate
- output
- signal
- alarm
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/22—Electrical actuation
- G08B13/24—Electrical actuation by interference with electromagnetic field distribution
- G08B13/2491—Intrusion detection systems, i.e. where the body of an intruder causes the interference with the electromagnetic field
-
- 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
- G01S13/52—Discriminating between fixed and moving objects or between objects moving at different speeds
- G01S13/56—Discriminating between fixed and moving objects or between objects moving at different speeds for presence detection
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- General Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Computer Networks & Wireless Communication (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
1,268,896. Radar. MINNESOTA MINING & MFG. CO. 20 April, 1970 [21 April, 1969], No. 18779/70. Addition to 1,219,202. Heading H4D. A pulsed radar of the type described in Specification 1,219,202 with reference to Figs. 6, 7A, 7B therein, exhibits a change in oscillator frequency and pulse frequency when the environment (i.e., the medium through which the pulses pass) changes. To overcome this the present radar comprises: a feedback oscillator including a transistor 30, Fig. 1, with an internal, tuned, feedback loop comprising capacitor 42 and transmitter inductor 44; a transmitting antenna 32 for radiating the oscillatory output; a receiving antenna 33 for receiving reflections of the transmitted wave and for superimposing a signal representative of the phase and amplitude of the reflected wave upon the signal in the internal feedback loop to form a composite feedback signal; a bias C/R network 46, 48, 50 which switches on the oscillator to give the pulsed output at a repetition rate which is a function of the phase and amplitude of a received signal and which is directly proportional to the amplitude of a charging voltage; an output circuit 36 which produces a pulsed signal 224, Fig. 2, having a repetition rate corresponding to the oscillator pulse repetition rate; and a negative feedback voltage regulator 14 responsive to the pulsed signal on line 20 to produce the charging voltage on line 16 at an amplitude inversely proportional to the repetition rate of the pulses signal, and adjusting the charging voltage when a change in the oscillator pulse repetition rate is detected caused by a change in the phase and amplitude of the received signal which lasts greater than a predetermined time and is thus indicative of a change in the environment, the adjustment being such as to restore the oscillator pulse repetition rate to a "standard environment" rate. The only substantial detected changes in the oscillator pulse repetition rate will thus be short and due to moving targets. The regulator 14 comprises a monostable circuit 56 comprising two balanced transistor pairs 129 and a pulse width determining adjustable C/R circuit 57, 59, 61, and producing a train of pulses 226, Fig. 2, of determined width. The pulse train is fed to an integrator 60 which has a time constant such that it integrates-out (i.e. removes the influence of), rapid changes of pulse repetition rate, e.g. due to a moving target, and any increase in the output of the integrator which provides the charging voltage on line 16, must be due to a slow change in environment. In the elaborated embodiment of Fig. 3, an alarm and indicator circuit 26 is used and an additional integrator stage 64A, 64B is used in the regulator 14 having a much smaller integration constant than integrator 60 so that very sudden changes in the pulse repetition rate, e.g. from birds, do not actuate the alarm. The output of the integrator stage 64B is taken via emitter follower 58, as a non-inverted output, to the alarm circuit. The latter comprises a deviation indicator 66 which gives an alarm output when the signal on line 22 departs by more than a predetermined amount from a value indicating no-moving targets in a standard environment. The alarm output on line 80 is fed to a decaying memory circuit 68. A capacitor 96 is charged up by successive short pulses enabling transistor 84, until transistor 86 conducts and alarm relay coil 88 is energized. The alarm state is stopped by a positive signal on the emitter of transistor 84 produced after 1 min. 15 sec. by a programmed unijunction transistor 70. A capacitor 106 at the gate and input terminals of the transistor is charged up to trigger the transistor after said period. To stop an alarm condition being indicated when the system is switched on, a balanced transistor pair 76 conducts and holds line 80 down to ground due to the non-conduction of transistor pair 116 of flip-flop circuit 72. After 1 min. 15 sec. unijunction transistor 152 conducts and its output switches the left-hand transistor of pair 116 into conduction. Circuit 72 now flips, and line 80 is able to transmit normal signals.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US616924A US3407403A (en) | 1967-02-17 | 1967-02-17 | Electrical detecting means |
US81780169A | 1969-04-21 | 1969-04-21 |
Publications (1)
Publication Number | Publication Date |
---|---|
GB1268896A true GB1268896A (en) | 1972-03-29 |
Family
ID=27087902
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB1877970A Expired GB1268896A (en) | 1967-02-17 | 1970-04-20 | Electrical detecting means |
Country Status (2)
Country | Link |
---|---|
DE (1) | DE2019733A1 (en) |
GB (1) | GB1268896A (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2315733A1 (en) * | 1975-06-23 | 1977-01-21 | Tacussel Maurice | RADAR, ESPECIALLY FOR THE SURVEILLANCE OF A PREMISES |
-
1970
- 1970-04-20 DE DE19702019733 patent/DE2019733A1/en active Pending
- 1970-04-20 GB GB1877970A patent/GB1268896A/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
DE2019733A1 (en) | 1970-11-12 |
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