JPS6285399A - Security system with saw transmitter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION Field of the Invention This invention relates generally to security systems, and more particularly to
Commonly known as a security system.

It relates to a security system comprising a radio frequency (T'-f) transmitter and receiver.

DESCRIPTION OF THE PRIOR ART A security system in which a plurality of remote transmitting devices transmit encoded T-, f signals to a central receiving station is configured to decode the signals and generate an alarm. Well known in the art. See, for example, U.S. Pat. No. 4,257,038 issued to Rounds et al.
No. 4,110,738 issued to Shaughnessy, No. 4,032,848 issued to Shaughnessy, Seaborn No.
No. 3,914,692, issued by Haymes (
3.852.74 issued to Ra1lies)
No. 0, No. 3,833,895 issued to recteau, and Isaacs (l5aacs).
No. 3,795,896, issued in 1999, all relate to wireless security systems.

Wireless security systems using T'-f transmitters are more flexible and easier to install than wired systems, which require a radio run from each remote transmitter to the central station. However, r-f signals can cause other problems, particularly false alarms caused by stray T'-f radiation and interference (stereostatic) that prevents reception of the r-fl alert signal by the receiver. These 14 questions are
This is made even more difficult by FCC (Federal Communications Commission) regulations that place limits on the signal strength of unlicensed transmitters, such as security system transmitters. RF transmitters must compete with other 'rf signals or operate in frequency ranges where there is little 'r''-f transmission. However, this frequency range is also a frequency range in which it is difficult to generate a suitable T'-f signal.

Wireless security system manufacturers generally choose to operate in high frequency ranges above 50 MHz to avoid interference. “Designing electrical oscillator circuits for such high oscillation frequencies presents some difficulties. Bulk crystal oscillators, which are effective at stabilizing oscillation at relatively low frequencies, are very small. If a relatively large crystal is used (because its frequency must be multiplied,
A large amount of power is consumed, which makes it necessary to replace the transmitter batteries relatively frequently. Inductive/capacitive circuits are relatively unstable and highly sensitive to physical bombardment.

The amplitude modulated (AH) T″-f signal is from the ΔH modulated blind,
For example, it is susceptible to interference from thunderstorms, and therefore it is desirable that the security system transmitter is an FM transmitter.

Electrical oscillator circuits using surface acoustic wave (5AII) devices are known. For example, a SAW oscillator circuit has been described for use in a satellite receiver. See ``Precision L-Band SAW Oscillators for Satellite Instruments'' by Thomas O'Shea, available from Sawchik, PO Box 18000, Orlando, FL, USA.
-Band SIV 0scillator forS
atellite Application, b
y Thomas O'5bea etal a
available floor+ Sawtck, In
c.

P, 0. Box 18000.0rlando, Fl
orida 32860). Prior to this invention, it was considered impossible to construct an effective FHSIV oscillator circuit.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a security system which considerably reduces the occurrence of false alarms and which consumes a relatively small amount of power compared to prior art devices.

It is a further object of the invention to provide a security system with an FH transmitter operating in the 50 MHz to 1 GHz frequency range.

It is another object of the invention to provide a security system with a transmitter using a SAW oscillator circuit.

The invention relates to a device for detecting a condition in a protection area and for generating a detection signal representative of this condition, a vibrating r-
an electrical oscillator circuit for generating an f signal, said oscillator circuit comprising a surface acoustic wave oscillator for stabilizing the oscillation, modulating the oscillation of said oscillator circuit arrangement in response to a detector signal; and a central station device for receiving r-f signals and providing an output indicative of conditions within the protected area.

Preferably, the surface acoustic wave excavator is connected within the feedback circuit portion of the oscillator circuit. Feedback circuit has a Q less than 12000
It is desirable to have. Preferably, the modulation device is a frequency modulation device.

In a preferred embodiment, the oscillator circuit is modulated by varying the capacitance of the oscillator circuit with a voltage variable capacitor. Also, in the preferred embodiment, the detection signal is a Manchester encoded signal and a frequency shift keying (FSK) modulation scheme is used.

Numerous features, objects and advantages of the invention will become apparent from the following detailed description when taken in conjunction with the drawings in Appendix J.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning attention to FIG. 1, an exemplary embodiment of a security system according to the present invention is shown. In this example there are three remote units 10, 11 and 12 and one central office 1.
There are 8. The remote device consists of an intrusion detector 10 at the door, a fear button device 11, and a fire detector device 12, each of which generates a signal when the particular condition it is designed to detect occurs. Each remote detector device io, it and 12 has an associated radio frequency (T-f) transmission 4314.15 and 16, respectively, which transmits an r-f signal to the central station 18.
received by.

Central station 18 decodes this signal and provides an output indicating the detected condition, e.g., flashing light source 20, siren 21,
or provides a signal 22 which is sent by telephone line 23 to a monitoring station (not shown).

Now starting with a more detailed explanation of this invention, the first
The selected embodiments of the security system shown in the figure include an intrusion detector device 10, a fear button device 11 and a fire detection aiiff 1.
2. It is understood that the three remote devices illustrated are exemplary.

Embodiments may include only one such remote device or may include hundreds.

Other types of detectors other than intrusion, fear and fire may also be included. The remote device 10 has a magnetic contact device 31 on the door, which sends out a signal 9uL! by means of an electric wire 32! !
! It is connected to the circuit 33. The processing circuit 33 is connected to the r-f transmitter 14, which is connected to the antenna 3.
4 to the central station 18. Similarly, the fear device 11 has a fear button 35 which is connected to a signal processing device 36 which in turn is connected to the antenna 31.
It is connected to a transmitter 15 equipped with
There is a fire detector 38, which is a signal processing device 39.
and the second processing unit is connected to a transmitter 8116 with an antenna 40. The central station 18 has an antenna 42, which is connected to five receivers and a signal processing circuit in the chassis 43 of the central station 1B. The signal processing circuit section includes an annunciator light source 20 and a relay lens 21.
, and a telephone line 23. It is understood that outputs 20, 21 and 23 are merely exemplary. In some embodiments, only one such output or a variety of other outputs may be used. It will also be appreciated that a wide variety of signals, such as battery status signals, monitoring signals, etc., may be transmitted between the remote units 10, 11 and 12 and the central station 18 in phase η.

The transmitter 14,15 and 1G r-f transmitter circuits are shown in detail in FIG. The adopted embodiment of the transmitter includes a surface acoustic wave (5AW) device 50, a transistor 55, and a coil 6.
0.61 and 62, a voltage variable capacitor 64, variable capacitors 67 and 68, capacitors 70 to 7G, resistors 80 to 88, and a diode 89.

The SAW device 50 is preferably a surface acoustic wave resonator (SAWR) 51 enclosed in a protective case 52.

One side of S/14R 51 is connected to coil 60 and the other side is connected to the base of transistor 55.

The case 52 of the SA device t50 is grounded. The emitter of the transistor 55 is grounded through a resistor 8o and a capacitor 70 connected in parallel. The collector of the transistor 55 is connected to a capacitor 71 and a resistor 8 connected in series.
1 to ground, to the other side of the coil 60, and to ground through an anti-f 34 (this is a figure on the microchip and will be explained further below) and a capacitor 76.

Variable capacitor 68 is connected in parallel with antenna 34. ] The coil 2 is connected to the antenna 34 with a positive power supply voltage (Vf
) is connected between. The condenser 5 is connected between the positive voltage line and the connection j&. The line between the static resistor 51 and the base of the transistor 55 is connected to a modulation circuit 49 generally located at the bottom corner of FIG. (
The remaining portions of the circuitry may be considered part of the modulation circuit 49 insofar as they interact with the modulation circuit 49. ) One side of the coil 61 is connected to the line between the 5A14R51 and the base of the transistor 55. The other side of the coil 61 is connected to ground through a parallel resistor 82 and capacitor 72 and through the variable capacitor 61, and is also connected to the positive voltage line through a resistor 88 and connected to the capacitor 7.
Connected to 4. The other side of the capacitor 74 is connected to the positive voltage line through a resistor 81, and resistors 8G and 8 are connected in series with the cathode of the diode toward ground.
9 to ground, voltage variable capacitor 64 to ground, and resistors 83 and 84 to data input line 58. The line between resistors 83 and 84 is connected to ground through capacitor 73. Line 59 represents the ground side of the data input circuit. The resistor 85 is connected between the data input lines 58 and 59 connected to the signal processing circuit section (33, 36 or 39).

Now looking at FIG. 3, a microcircuit diagram is shown. That is, in the preferred embodiment, the circuit of FIG. 2 is arranged on an integrated circuit chip or printed wiring board, and the various connections are made by means of metal graphics printed on the chip.

There are two main shapes: the ground shape 115 shown by the dashed line and the positive voltage shape 116 shown by the solid line.
There is. The figures 115 and 116 are separated by an absolute Ii1 on the IC chip or printed wiring board. When a printed wiring board is used, 81t of approximately 1/8" x 1" of the figure 115 acts as a T'-f antenna. If this circuit is used in a shielded hybrid (miniaturized) circuit, a separate antenna must be used to radiate the energy outside the shield. Also shown is a third graphic 117 used to connect the four circuit strands. Other conventional figures, such as those shown schematically by the remaining circuit lines in FIG. The connections are indicated by black dots such as 107, which correspond to the circuit points with the same number at J3 in the circuit diagram of Figure 2. If the dragon is to be obtained, it is necessary, but,
Similar shapes can also be used to tune the appropriate oscillation frequency, as is known in the art.

In the preferred embodiment, the 5AII device 50 is a 315 MHz zero-phase surface acoustic wave device, the transistor 55 is a bipolar type 23C287B, and the coil 60 is a 6-turn, W, G 28 wire. , diameter 0.1
It is an air-core coil with a length of 25 inches and 13/32 inches.

Preferably, coil 61 is a 0.41 microhenry fixed coil and coil 62 is a 1.5 microhenry fixed coil. Voltage variable resistor 64 is preferably a model HV2105C silicon Epicap diode (available from Motorola, Inc.).
Variable capacitors 67 and 60 are 3-35 picofarad capacitors.

Capacitors 70, 73, 75 and 76 are 470 pico 77
1 rad is desirable, and 71 is 1000 pl'
, 72 is a 94pt capacitor, and 74 is a 47pF capacitor.

Resistors 83, 84 and 86 are preferably 1000Ω resistors, resistor 80 is a 100 ohm resistor, resistor 81 is a 47A:Ω resistor, and resistor 85 is 600Ω resistor. , and the resistor 87 is a 2 Meg oak resistor. Diode 89 is model 1N4148. 34 is preferably made of copper.

Other components of the invention as shown in FIG. 1 may be conventional, such as those described in the previously listed US patents.

However, the signal processing l! I! Preferably, the device is programmed to generate a Manchester digital signal having a voltage level of approximately 7 to 5 volts at approximately 4 kilohertz.

The circuit works as follows. 5A141151, transistor 55, capacitor 16 and coil 60 form a Pierce oscillation circuit, 5A14R
51 controls the oscillation frequency. Transistor 55 is an active amplification element. The 5AWR 51 and the coil 60 can be considered to be the main elements of the feedback circuit 48. Rinki or “
The center frequency is preferably tuned by mechanically adjusting the separation between the windings of coil 60. The line that includes Conan 1 No. 11 and resistor 81 is 5AI41 (5
1 indirectly provides a shunt to 1, with capacitor 1 blocking the DC current and resistor 81 serving as the load and circuit Q adjuster (see discussion of Q below). shortens the start-up time of oscillator circuit 47. Capacitor 75 is a shunt capacitor to prevent T-f energy from entering the modulator portion of the circuit through ground. Coil 62 It has a lower resonant frequency than the rest and serves as a choke to prevent antenna energy from being fed through capacitors 15 and 7G to the bias circuit section of transistor 55 (see below). Capacitors 71, 75 and 16 are chosen to have low capacitive resistance so as not to create significant thermal stability problems.

The modified Pierce circuit 47 further includes a coil 61 and a variable capacitor 67, which can also be considered part of a modulation circuit, as discussed further below. These two elements r are tuned as the centerline frequency of oscillation and the modulated frequency.

Resistors 88 and 82 and coil 61 are connected to transistor 55
The DC bias point for this transistor is set to determine the gain of the transistor. Resistor 80 and capacitor 70 further refine the gain adjustment and prevent the gain from dropping at low battery voltages.

The modulation circuit is mainly composed of a capacitor 1j72, 73, 74, resistors 83 to 81, a variable capacitor 67, and a voltage variable capacitor (VVC) 64, the last of which is the most important element. ] Capacitor 2 is v
It provides a shunt to vC and trimmer condenser 1167.

Capacitor 72 is selected to provide temperature compensation for VVC 64. Capacitor 73 and resistor 84 form a filter network. Resistor 85 provides a matched low impedance load to the incoming data signal and is sized to match the circuitry used in signal processing device 33, 36 or 39.

Resistors 83-87 together ensure that undesirable negative voltages are V
It forms a DC voltage divider that helps to prevent voltage build-up at the cathode of VC64. Capacitor 74, resistance 8G
and diode 89 are connected to the 1-rimming circuit (61 and 61
) and the modulation circuit, the capacitor → Noah 4 blocks the flow of DC current, and the resistor 86 acts as a load to block the flow of excessive power from the shunted circuit. Diode 8 serves as a voltage regulator for the resistive divider network.

It is desirable to adjust the centerline frequency and the shift frequency (the amount by which the frequency shifts when modulated) by trimming the variable capacitor 67. The frequency can also be adjusted by trimming the coil 61. The latter trimming is carried out by slightly mechanically moving the windings of the coil relative to each other. (In the hybrid transmitter I have constructed, mechanical trimming of coil 61 is the method chosen to adjust the frequency.) Coils 60 and 61 are the same as those discussed herein. can be modified to accommodate different centerline and shift frequencies. These coils play an important role in keeping the feedback energy in positive rather than negative phase, thus sustaining oscillation.

These coils are unique in that their Q is quite low compared to the normal Q as given in this type of circuit, and this low Q of these coils helps in obtaining a low overall Q of the feedback circuit. This is an important factor (see below).

The operation of the circuit is as follows. The oscillation of the Tachimoto T'-f oscillator circuit 41 is caused by the feedback section 4 of the circuit including the SAW device 50.
stabilized by 8. (The oscillation frequency can be tuned by trimming the coil 61 in some embodiments.) The oscillation of the feedback circuit, and thus the oscillation of the circuit off, is modulated by the data input in the following manner. A variable voltage capacitor 64 changes the capacitance of the modulation circuit in response to changes in the data input voltage. This change in capacitance of the modulator circuit shifts its oscillation frequency.

Since the modulation circuit is in parallel with the 5AWR circuit, changing its resonant frequency changes the effective resonance of the entire circuit. The modulation circuit can be thought of as "pulling" the modulated frequency from the regular SAW resonant frequency. For the illustrated circuit, a data input voltage change of about 5 volts will result in a change in oscillation frequency of about 60 to 90 kilohertz, depending on the tuning.

A change of more than 100 kilohertz was obtained. Preferably, the overall 5AWR centerline frequency and modulation frequency (frequency shift) are both tuned simultaneously using variable capacitor 67 (or coil 61).

The security system of this invention is a frequency deviation GEE Inc. (F
SK), other frequency modulation schemes can also be used. Signal processing device, e.g. 33.3
6 or 39 generates a digital signal consisting of a series of voltage transitions between a high voltage value (preferably 4 to 5 volts) and a low voltage ii (preferably 0.1 to 0.4 volts). The signal is preferably Manchester encoded, which allows the central station 18 to regularly update its synchronization with the receivers. However, other digital encoding schemes can also be used.

FIG. 4 shows three examples of Manchester encoded signals. Each of the three examples includes a precursor section (the left part in each sample) that is a series of Manchester-coded ones. This precursor section gives the transmitter time to prepare and Give the receiver time to establish communication. (Even if the front end data bits are lost, no problem occurs.)
There is a central part of zero voltage (not star encoded), but
This provides a transition to the next important data point i~. Even when the signal is all O's or all 1's (as in the right part of sample numbers 2 and 3, respectively), the Manchester method produces regular transitions between low voltage (direct and high voltage values). Be careful what you're doing.

This is the feature that allows regular identification with the receiver.

The voltage transitions of the digital signal (Manchester or otherwise), as mentioned above, are transmitted at r.
-f causes a corresponding frequency shift in the signal. This frequency shift is detected by the station 18 receiver and the digital overload signal is reproduced.

The security system according to the invention is much more reliable than prior art security systems due to the superior frequency stability of the transmitter and lower power consumption.

The SA-stabilized transmitter is a regular LC and RCC type shaker/
It does not have the temperature shift and drift problems associated with transmitter devices, nor does it have the power supply and battery failure problems associated with prior art bulk crystal oscillator circuits. SAW y′F.

The oscillator/transmitter does not exhibit the spurious modes of oscillation that plague prior art transmitters. Additionally, the harmonic oscillation frequency's commercial level is more attenuated from the fundamental frequency than in prior art oscillators/transmitters.

A feature of this invention is the antenna and output antenna load simulation on the wiring machine which leads to high oscillator starting reliability, which prevents repeated starting from dead condition.
This is effective for low Kl transmitters. Furthermore, the operating pressure range for each transmission is very wide, from DC 3V to DC 1V.
It extends up to 2V, and the frequency changes in this range are only small.

This invention is the first operational FH5A14 oscillator/transmitter. An important factor in creating an operational FHSAW oscillator/transmitter is reducing the Q of the feedback circuit compared to conventional circuits. Q can be defined in terms of bandwidth or in terms of impedance (Z) and resistance (R); Q due to the title is referred to here as Qbw, and Q due to the latter is referred to here as QZR. -ru. Note that Q is a relative term and these two Q values are generally not equal. Qbw is Qbw=Fo/,
In this case, F. where i is the fundamental frequency (318 MHz in the adopted example), L is the inductance, and C is the capacitance, then given by the equation Fo='/π, /L and −, and UF is the value during modulation. QII? can be defined as -7 when Z is given by Z = (X, -X,), where QZRl'r ×1 is the inductive reactance, xC is the inductive reactance, R is the direct current and It is skin effect resistance. Typical transmitter designs strive to maintain high Q feedback circuits. To obtain a reasonably high output voltage and have an acceptable transmitter broadcast range, the Qbw should be approximately 16X 1 in the feedback circuit.
It was believed that it should be 03. (Broadcast range should be at least 200 feet for security transmitters.) However, high Q bwO5IVR
I? ; based oscillation circuits tend to shift to free vibration mode. A feedback circuit is desirable. Coil 60.61 is
It is also a feature of the invention that it is constructed from wire of a much smaller diameter than that commonly used in this type of oscillator circuit. Reducing the wire diameter is important in establishing the low QZR required for adequate frequency pulling capability. Reducing the wire diameter limits the current and reduces the electrical cross-sectional area. Increase the resistance by
Therefore, the T'-f skin effect is increased. In a 5AWR circuit, the reactances X and Xl must generally remain constant for constant frequency so that the resistance is a valid variable. As previously mentioned, with proper biasing of transistor 55, the broadcast range to 900 feet was increased despite the low Large. The rHSA-transmitter of this invention has eight HS
It is particularly useful for security systems because it is less susceptible to noise and interference problems that disrupt AW transmissions and put them out of practical use.

Another feature of this invention is that it is manufactured on a single IC chip. Prior to this invention, it was not thought possible to place such a transmitter on a 1-71-tub. The design of the graphics given previously is important for this.

Yet another feature of the invention is the unusually fast start-up time of the 5AWr (transmission filter). Such fast start-up results in less data loss and shorter transmission times.

One feature of the present invention is that a relatively large frequency shift can be obtained. As mentioned previously, frequency shifts between 60 and 90 kilohertz are quite common, and shifts of 100 kilohertz have also been obtained. Prior to this invention, it was believed that such high frequency shifts would cause the S/V equipment to go into a free vibration mode without returning to the fundamental frequency.

Yet another feature of the invention is the use of variable voltage capacitors or tuning diodes to modulate the 5IVR circuit. Modulation down to zero volts is possible with the design shown. Before this invention, this was called “H
It was never done on a transmitter IC chip.

For clarity, although the r-f transmitter circuit of FIG. It should be understood that from some point of view the modulation circuit may be considered part of the feedback circuit and/or the oscillator circuit.

A novel security system has been described that includes a frequency modulated transmission field using an S-sieve device and incorporates many other features. It will now be apparent that those skilled in the art may make many uses and modifications of the specific embodiments described without departing from the inventive concept. Many other equivalent electronic components and materials may also be used. For example, different amplifiers may be substituted for transistor 55, other inductance combinations may be used, different chip (board) geometry designs and materials may be substituted, and the circuit may be It may be configured other than on the chip (other). Many truncated remote transmitting devices and receiving stations can also be used. Many forms of frequency modulation can be used, and many types of encoding schemes, digital or otherwise, can be used. Other SAW devices may also be used. For example, I have had success using a 180 degree phase S static oscillator in J3 in a similar F)l transmitter circuit. Accordingly, the present invention should be construed as encompassing all novel combinations of features present in the previously described security systems.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an exemplary security system according to the present invention. FIG. 2 is a detailed circuit diagram of the 'r'-f transmitter 11 portion of the present invention. FIG. 3 is a miniature diagram showing the microcircuit diagram of the transmitter and the connections to this diagram. FIG. 4 shows several examples of data signals input from the signal processing device to the transmitter. In these drawings, 10.11.12 is the remote device (
respectively, detector device 1 fear button device, fire detection 5
Vi place) , 14 , 15 , 16 Ha! 18. I
a IXI wave transmitter, 18 is a central station, 41 is an oscillator circuit, 48 is a feedback circuit, 49G is a modulation circuit, 50 is a surface acoustic wave device, 51 is a surface acoustic wave resonator, 55 is a transistor, 60.61.62 64 is a voltage variable capacitor, 67 and 138 are variable capacitors, 70 to 76 are capacitors, 80 to 88 are resistors, and 89 is a diode. (5 other people) FIG, 2

Claims (1)

[Claims] 1. A device for detecting a condition in a protection range and generating a detector signal representative of this condition; an electrical oscillator circuit device for generating an oscillating r-f signal; the aforementioned oscillation; a surface acoustic wave device connected within said oscillator circuit for stabilizing said oscillator circuit; a device responsive to said detector signal for modulating the oscillation of said oscillator circuit; and said vibrating r- a central office device for receiving f signals and providing an output indicative of said condition. 2. The device for modulating comprises a circuit device for modulating the oscillation frequency of the oscillator circuit device to generate a frequency modulated r-f signal. The security system described in section. 3. The electrical oscillator circuit device comprises a feedback circuit, and the surface acoustic wave device includes an electric current in the feedback circuit to stabilize the oscillation of the oscillator device around a predetermined number of circuits. Claim 2, which is connected to
The security system described in section. 4. The security system according to claim 3, wherein the feedback circuit has a Q of less than 12,000. 5. Security system according to claim 2, wherein said device for modulating comprises a device for changing the capacitance of said modulating circuit device. 6. The security system according to claim 5, wherein the device for modulating the capacitance is a voltage variable capacitor. 7. said detector signal consists of a signal having a series of voltage transitions between high and low voltage values, and said device for modulating modulates the oscillation frequency of said oscillator circuit arrangement; 3. The security system of claim 2, wherein the security system modulates and generates an r-f signal having a frequency shift corresponding to said voltage transition. 8. The security system of claim 7, wherein said detector signal comprises a Manchester encoded signal. 9. The security system of claim 7, wherein said frequency deviation is between 60 kHz and 100 kHz. 10. The security system according to claim 1, wherein said oscillation frequency is in the range of 50 MHz to 1 GHz.