CA1218119A - Overload protector - Google Patents
Overload protectorInfo
- Publication number
- CA1218119A CA1218119A CA000456624A CA456624A CA1218119A CA 1218119 A CA1218119 A CA 1218119A CA 000456624 A CA000456624 A CA 000456624A CA 456624 A CA456624 A CA 456624A CA 1218119 A CA1218119 A CA 1218119A
- Authority
- CA
- Canada
- Prior art keywords
- power
- input
- diversion
- dissipating element
- overload protector
- 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
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3036—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers
- H03G3/3042—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers
- H03G3/3047—Automatic control in amplifiers having semiconductor devices in high-frequency amplifiers or in frequency-changers in modulators, frequency-changers, transmitters or power amplifiers for intermittent signals, e.g. burst signals
-
- 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
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/03—Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G11/00—Limiting amplitude; Limiting rate of change of amplitude ; Clipping in general
- H03G11/02—Limiting amplitude; Limiting rate of change of amplitude ; Clipping in general by means of diodes
Abstract
OVERLOAD PROTECTOR
ABSTRACT OF DISCLOSURE
An overload protector, using a power-dissipating element for receiving and dissipating excessive radio-frequency power, can safely transfer a signal from an input to an output. The protector also has a detector coupled to the input for providing a bias current in response to an input signal in excess of a predetermined magnitude. Also included is a diverter coupled to the input, the output, the power-dissipating element and the detector. This diverter can receive the bias current and can, in response, redirect power at the input from the output to the power-dissipating element.
ABSTRACT OF DISCLOSURE
An overload protector, using a power-dissipating element for receiving and dissipating excessive radio-frequency power, can safely transfer a signal from an input to an output. The protector also has a detector coupled to the input for providing a bias current in response to an input signal in excess of a predetermined magnitude. Also included is a diverter coupled to the input, the output, the power-dissipating element and the detector. This diverter can receive the bias current and can, in response, redirect power at the input from the output to the power-dissipating element.
Description
BACKGROUND OF THE INVENTION
The resent invention relates to overload protectors for preventing excessive radio-frequency energy, applied to an input, from reaching an output.
There are many applications in which a delicate input circuit must be protected from excessive voltages, current or power. For example, certain field effect transistors and other devices cannot tolerate excessive voltage at their inputs. Other examples include the input to certain receivers. For example, in aircraft weather radar systems, the input to a mixer can be damaged by excessive power emanating from nearby radio sources or reflected power originating from the radar itself. Radar systems are especially susceptible to overloading because they incorporate an antenna serving the dual function of transmitting relatively high energy pulses and receiving very faint signals of the same form. In the event such an antenna is damaged or broken off, it is likely that these high energy pulses will not be safely transmitted but will be coupled directly into the input of the radar receiver.
Such radar systems have been very difficult to protect. Known methods of protecting the radar have included rotating the weather radar antenna so it would not receive damaging signals from reflections or from other nearby, operating radar systems until the aircraft has left the heavily trafficked area. One unsuccessful method for protecting the radar system is to turn off its power. However, even when power has been removed, the radar front end and its sensitive components are still exposed to receipt of damaging energy from nearly high frequency sources.
' 1 A known technique for protecting a sensitive input is by shunting the input with one or more stages of pin diodes. A relatively large, radio frequency signal placed across the pin diodes will forward bias them. The forward biasing will persist because of the capacitance of the diode. This approach is inherently limited since this power mutt be absorbed by the pin diode which must -therefore have a high power rating.
Consequently, the pin diode tends to be rather slow and will allow substantial power to reach the protected circuit before the diode becomes effective. Moreover, pin diodes do not provide a perfect short but will only reduce the dynamic shunting impedance across the input of the protected circuit.
With high frequency circuits it is often desirable and practical to take advantage of the relatively short wavelengths of signals propagating through a circuit. For example, a -transmission line may have one end shorted or open but depending upon the effective electrical length of the transmission line, the other end can appear as either an open or short circuit. Similarly, depending upon the spacing of ports on a transmission line, either complete or no coupling will occur between ports. This phenomena is used in circulators, directional couplers and hybrid couplers.
These various effects can be produced with wave guides cables, micro strips, strip lines and through known equivalent circuits that simulate the effect of a transmission line.
Accordingly, there is need for a device for protecting a delicate circuit by interrupting a higher energy power flow more quickly and more completely than has been possible with systems of the prior art.
I
In accordance with the illustrative embodiment demonstrating features and advantages of the present invention, there is provided an overload protector for safely transferring signals from an input to an output.
The protector has a power-dissipating element, a detection means and a diversion means. The detection means it coupled to the input or providing a bias current in response to a signal at the input in excess of a predetermined magnitude. The diversion means is coupled to the input, the output, the power-dissipating element and the detection means. The diversion means can receive the bias current and, in response, redirect power at the input from the output to the power-dissipating element.
In one embodiment, protection is provided to a high frequency detection system having an antenna, a high frequency power source and a power-dissipating element. The detection system also has a phased means having at least a first, a second and a third port. The first and second ports are connected to the antenna and power source, respectively. The first port is phased to communicate with the second and third ports. The second and third ports, however, are phased to prevent communication between them. Also included is a processing means for responding to signals having a predetermined pattern to produce a detected signal. The detection system also has a protector means coupled to the power-dissipating element, the third port and the processing means for diverting signals issuing at the third port from the processing means to the power-dissipating element. Thus, the processing means is protected from excessive signals.
An embodiment of a protector according to the principles of the present invention can selectively transfer power from an input to an output. The :~Z~8~
1 protector employs a diversion transmission means coupled between the input and a power-di~sipating element for conveying power there between. A reflex means of the protector is coupled to the diversion transmission means for reflecting power thereon away from the power-dissipating means. The protector includes an operative means for altering the extent of reflection provided by the reflex means. Thus, the protector can divert power from the output to the power-dissipating 10 element-By employing devices of the foregoing type, a highly effective protector is achieved that can quickly and completely divert power from a protected circuit to power-dissipating component. In a preferred embodiment, the input is coupled through a directional coupler to a node marking the start of two quarter wavelength branches. One branch extending toward the protected circuit is shunted by a first limiter diode, the other line terminating in a power-dissipating resistor. A
controllable stub connected to this power-dissipating resistor has another shunting limiter diode connected at a spacing of one quarter wavelength from the power-dissipating resistor. Preferably, these diodes are forward biased by a Skeptic diode detector driven by the directional coupler. Thus, an excessive signal can effectively reconfigure the circuit to detour the damaging power.
The protector can be extremely fast since these Skeptic diodes can be designed to respond almost immediately to the excessive incoming power by producing a rectified current. The system, which is a passive apparatus, can be designed to switch off in five to twenty nanoseconds or better depending upon the components chosen and the input power to be switched off. In one constructed embodiment the protector was rated for handling 1.5 Kilowatts with a 16 microsecond ~2~119 l pulse width (duty cycle of .003) and a 1.2 microsecond recovery time.
By switching the power to an external load, the protector can be constructed from micro strips which might otherwise be damaged. Thus, notwithstanding unintended loading due to mismatching, a greatly improved power handling capability, about one order of magnitude greater, is achieved because the redirecting of power keeps real power at the diode an order of magnitude lower than the maximum rating of the diode.
BRIEF DESCRIPTION OF THE DRAWINGS
The above brief description, as well as other objects, features and advantages of the present invention, will be more fully appreciated by reference to the following detailed description of a presently preferred but nonetheless illustrative embodiment in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein:
Fig. l is a schematic block diagram of a high frequency detection system including an overload protector according to the principles of the present invention;
Fig. 2 is a more detailed schematic of the overload protector of Fig. l;
Fig. 3 is plan view of a micro strip version of the circuit of Fig. 2;
Fig. PA is a simplified, partial, equivalent circuit diagram illustrating some of the micro strip transmission lines ox Fig. 3 when power it being conveyed from input to output; and Fig. 4B is a circuit diagram similar to that of Fig. PA but showing conditions existing when power is being conveyed from the input to a power-dissipating element.
In Fig. 1 a high frequency detection system, such as an aircraft weather radar system, operating at 9.35 GHz, is illustrated. It will be understood that this environment is exemplary and various other sensitive systems operating at other frequencies can be protected instead. In this specification the term radio-frequency means frequencies above audio and below infrared. The illustrated radar system includes antenna 10 and magnetron 12 connected to a first port 14 and second port 16, respectively, of a phased means, shown herein as wave guide circulator 18. Circulator 18 is phased so that antenna 10 can communicate with either magnetron 12 or third port 20 but -third port 20 and magnetron 12 (a high frequency power source) do not intercommunicate.
Wave guide port 20 is connected through wave guide to coaxial cable transition 21 to input Jo of an overload protector comprising protection means 24 and power-dissipating element 26. Transition 21 may be a commercially available device in which a wave guide terminates with an internal conductive probe acting as the center line of a coaxial cable. The output Jo of protector 24 connects to the input of a processing means, shown herein as the front end or mixer of a radar receiver. Mixer 28 and its associated circuitry may be the conventional radar circuit found in an aircraft weather radar system, although other sensitive circuits may be protected instead.
Referring to Fig 2, the previously mentioned overload protector is illustrated in a more detailed schematic diagram showing power-dissipating element 26 as an external grounded load. Element 26 is connected to connector Jo which may be an OSM-type of connector.
Input Jo (an OSM-type female connector) connects to one port of directional coupler 30 whose corresponding port Lo l19 1 connects to node A. The two other corresponding ports of directional coupler 30 are separately connected to a matching 50 ohm resistor 32 and to the input of a matching network 34. Matching network 34 is designed to correct impedance mismatches that might otherwise exist between the circuitry served by it. The input Jo is designed to work into a 50 ohm characteristic impedance.
Directional coupler 30 is designed to have a -33dB
coupling between input Jo and the input of matching network 34. Directional couplers such as coupler 30 are known per so. See for example, Members of the Staff of the Radar School, MUTT., Principles of Radar, McGraw ill Book Co., Inch (1952). pp. 834-39; Dr. Max Fogies, Modern Microelectronics, Research and Education Association, New York, New York (1972) pp. 222-25. As explained in those references, directional couplers can be Fabricated from wave guides, cables, strip lines or micro strips and the same phenomena can be produced with an equivalent circuit composed of inductors and capacitors. In this embodiment, directional coupler 30 is designed to afford duplex communication between input Jo and node A.
The output of matching network 34 connects to a detection means (also referred to as an operative mean) in the form of a pair of unidirectional conducting devices 36 and 38. Devices 36 and 38 are preferably Skeptic diodes (for example type DMJ, manufactured ho Alpha Industries of Woburn, Maws.) having both of their anodes connected to the output of matching network 34.
A low past filter means includes a shunting storage capacitor 39 connecting between ground (that is, a reference potential and the junction of test point TO
and the cathodes of diodes 36, 38. The filter means includes an inductor or chose 40 connecting between test point TO and node C. Also, 68 ohm carbon composition, direct-current return resistor 43 it shown connected I
between ground and test point TO.
Configured in this fashion, a sufficiently large signal at input Jo can forward bias diodes 36 and 38 which then act as detectors for producing a voltage across capacitor 39 and a bias current Is through inductor 40 to node C.
Node C is coupled through beam lead capacitor 42 (10 pi) to the anodes of parallel limiter diodes 44 and 46 whose cathodes are grounded. For the specified operating frequency diode 44 may have a recovery time of 20 nanoseconds and diode 46, 10 nanoseconds. Diodes 44 and 46 may be pin diodes, type numbers COLA 3132-02 and COLA 3131-01 respectively, by Alpha Industries of Woburn, Mass. A direct current return is provided by inductor 48 which connects between ground and the junction of the anodes of limiter diodes 44 and 46 and the output connector Jo.
The balance of the circuitry of Fig. 2 is herein referred to as a diversion means. Line A-C between nodes A and C is referred to herein as a main (or as a third) transmission means. Line A-C is preferably a quarter wavelength transmission line which may be formed from micro strips, although embodiments employing wave guides, cables or other equivalent circuits are possible. A variable impedance is provided by a semiconductor, limiting diode 50, herein referred to as a cancellation (or as an interrupt) means. Limiting diode 50 has its anode connected to node C and its cathode grounded. In one preferred embodiment, diode 50 is a pin diode, type COLA 3133-03 manufactured by Alpha Industries, Woburn, Mass., having a recovery time of 50 Nina seconds. Another quarter wavelength line segment between nodes A and B, line segment A-B, is similar to line A-C and is referred to as a diversion transmission means. Node B is coupled through capacitor 52 (a capacitor identical to capacitor ..~,~
mob/
~23~
1 42) and OHM connectors I to 50 ohm matching termination 26. Line B-D, a second transmission means connected between nodes B and D, is another quarter line similar to the two other lines, line A-C and line By A
S shunting means (also referred to as a reloading or reflex means) is shown as a shunting diode 54 with its anode connected to node D and its cathode grounded.
Diode 54 is a semiconductor providing variable impedance (that is, an impedance varying diode) and may be identical to previously mentioned diode 50. A fourth transmission means, line D-E, is connected between node D and node E and is serially connected with line B-D to form a line stub. In a referred embodiment line D-E is effectively one half wavelength long.
Referring to Fig. 3, a practical embodiment of the circuit of Fig. 2 is illustrated as a micro strip circuit. It will be understood that this circuit could be fabricated with discrete components where the various transmission lines are synthesized by an equivalent circuit, especially for lower frequencies. Alterna-lively, the circuit could be made with wave guide although the latter would be substantially more difficult to fabricate. The illustrated circuit employs a four-walled aluminum frame 60 onto which are mounted the three previously mentioned OSM-type connectors Jo, Jo and Jo'; The outer conductive cowls of connectors Jo, Jo and Jo are screw mounted to aluminum frame 60.
The interior circuitry is mounted on a micro strip board comprising an aluminum ground plane I
electrically and physically connected to frame 60 and having the same outside dimensions as it. On the side of frame 60 opposite plane 62 an identically sized aluminum cover plate (not shown) is attached by screws to the frame. Ground plane 62 has laminated to its inside face a low loss dielectric material, preferably composed of polytetrafluoroethylene which is .010 inch 1 thick. The various conductive strips illustrated upon dielectric material 64 are metal laminations which may be photo chemically etched into the pattern shown.
Micro strip board material can be obtained from Rogers Co., of Chandler, Arizona, the dielectric material being referred to as RT/Duroid 5880. In this schematic components previously described in Fig. 2 bear identical reference numerals.
The majority of the illustrated strip lines are dimensioned to provide a 50 ohm characteristic impedance. Specifically, the strip lines aligned between connectors Jo and Jo, the previously mentioned lines A-B, B-D, D-E, as well as the line between connector Jo' and node B, are all designed to have a 50 ohm characteristic impedance. The width of these 50 ohm strip lines it .031 inch. Similarly designed is the strip line AYE running between elements AYE and 32 in the directional coupler.
The directional coupler 30 includes a strip AYE
which is spaced about .035 inch from strip 30B for approximately 0.225 inch. Directional coupler 30 is designed to operate at an input frequency of 9.3S GHz with -33dB coupling from input Jo to element AYE. The right end yin thy view) of strip AYE is terminated ho previously mentioned chip nest ion 32 which connect to grounded pad 66. Pad 66 is a metal lamination resting atop dielectric material 64 hut having a slot cut there through and reaching the aluminum ground plane 62.
This typical slot is approximately 0.13 inch long and 0.031 inch wide with rounded end. The slot is connected to ground plane I by soldering pad 66 to the ground plane 62.
Previously mentioned matching network 34 is shown herein a shunting capacitive element AYE, a widened metallic pad for capacitively shunting signals to the underlying ground plane 62. A strip line also .~31 if 1 inch wide) then reaches from shunting capacitor AYE to previously mentioned Skeptic diodes 36, 38, shown herein as a parallel combination, hermetically sealed into a common package by the manufacturer. The strip 34C between component AYE and 36 is shunted about approximately two thirds of the way towards component 36 by strip line inductor 34B which connects to grounding pad 68, a pad again having a soldering slot for connecting to ground plane 62. Strip 3~B is a quarter wave direct-current return acting as a radio-fre~uency choke. Components AYE and 34C provide an impedance matching network so that the 50 ohm strip line from strip AYE is matched to the lower impedance presented by Skeptic diodes 36, 38. The dimensions and thus the values of elements AYE and 34C are selected according to the impedance at diodes 36, 38.
A shunting storage capacitor 39 is formed by the area of pad 39 which is approximately .04 square inch.
Previously mentioned direct-current return resistor 43 connects between pad 39 and the illustrated (typical) slot in grounded pad 70. A strip inductor, .007 inch wide and .242 inch long connects between pad 70 and the strip line running between connector Jo and diode I at a point nearer to the diode. Diode 46 is generally in the shape of a cubical chip waving terminals formed on opposing faces. Its cathode face is solder-connected to ground plane 62 exposed through the slot AYE cut through dielectric material I Area 72 is grounded to prevent bypass currents. The anode of diode 46 is connected to the micro strip on either side of slot AYE by a 99-99%
pure gold ribbon, .005 inch by .0025 inch. A gap in the micro strip between diodes I and 50 is spanned by beam lead capacitor 42. Previously mentioned diodes 44 and 50 are situated in slots AYE and AYE, respectively, (similar to slot AYE so that each of their cathodes connect to ground plane 62. Again, their anodes connect I
1 to a gold ribbon spanning the slows AYE and AYE.
The anode of diode 50 connects to previously mentioned node C. The micro strip between nodes C and A
is the previously mentioned quarter wavelength trays-mission strip and is, in -this embodiment, approximately 0.190 winch long, in view of the operating frequency of 9.35 GHz. Of approximately the same length is the perpendicular micro strip line running from node A to node B. Soldered between node B and strip 74 is beam lead capacitor 52. Strip 74 leads to load connector Jo'. The strip between node B and node D is similar in length to line A-B. At node D limiter diode 54 is soldered within slot AYE atop ground plane 62. Again, the anode of diode 54 connects to a gold ribbon spanning either side of slot AYE. A folded micro strip between node D and E is approximately twice the length of strip B-D and is open at node E.
To facilitate an understanding of the principles associated with the foregoing apparatus, the operation of the equipment of Figs. 1, 2 and 3 will be explained using the simplified schematic of Figs. PA and 4B. In Fig. 1, circulator 18 operates such that high frequency power from magnetron 12 is transferred to antenna 10 in short bursts without coupling a significant signal into port 20. Signal reflected ho targets eventually cause a return to be received by antenna 10 and coupled through circulator 18 into port 20. After passing through transition 21 the return signal is coupled to input connector Jo of protector 24.
The relatively small signal appearing at connector Jo does not produce a sufficient signal to charge capacitor 39 fig. 2). Accordingly, any current IT through inductor 40 is negligible. Thus diode 54 and 50 are not forward biased and remain essentially a very high impedance Jan open circuit). As a result, the open circuit at node still appears as an open circuit at 1 node D. One quarter wavelength therefrom at node B this open circuit appears like a short across load 26. This short at node B causes the line By to appear like an open circuit from node A. Since there are no other S diode or other components shunting the energy in the micro strip connection between connectors Jo and Jo, signals are conveyed without reflection between those connectors. An equivalent circuit of the micro strip under these conditions is shown in Fig. PA, wherein node B is shown grounded to produce what appears to be an open circuit when viewed from node A.
Referring again to Fig. 1, we now assume that the magnetron pulse applied to antenna 10 is reflected back into port 14 due to a nearby obstruction or due to damage to antenna 10. This pulse is therefore at a relatively high power level. Alternatively, a nearby radar signal, a likely happening at a crowded airport, can be directed into antenna 10 to produce an excessive signal at port 14. Consequently, an excessive signal it conveyed from port 20 to connector Jo. This pulse may typically rise at the rate of 10 watts per nanosecond.
Accordingly, a significant amount of energy is coupled from the directional coupler 30 (Fig. 2) through matching network 34 to detecting diodes I 3B. The high speed rectification provided by them causes a rapid charging o capacitor 39. Consequently, a bias current IBM eventually reaching about 60 ma flows through inductor 40 and forward biases diodes 54 and 50. This current dramatically reduces their dynamic impedance and presents an effective short circuit from their anode to cathodes. These effective short circuits cause the grounding of the micro strips as illustrated in Fig. 4B.
Nodes C and D have been grounded by their respective limiter diodes as illustrated in Figs. 2 an 4B. Since the line A-C, having its nod C grounded, it a quarter wavelength long, the effect of line A-C as seen from ~Z~8~1~
1 node A is that of an open circuit. Similarly, line B-D
has its node D grounded so that the line appears from node B as an open circuit. Consequently, there is an undisturbed signal path from input connector Jo -through S line A-B and connector Jo to power-dissipating element 26. Therefore, the excessive power on connector Jo is dissipated externally. Moreover, the effective open circuit presented by line A-C provides excellent isolation to keep destructive power from ever reaching the protected circuits.
It will be appreciated that as the input power rises, should any of it leak past line A-C, additional protection is provided by diodes 44 and 46 (Fig. 2).
Such leaked power can forward bias diodes 44 and 46.
These diodes have a certain amount of capacitance so that they effectively remain forward biased to shunt power so that any signal reaching output connector Jo is relatively small. Significantly, diode 44 and especially diode 46, can be selected to have a very fast response since these diodes need not dissipate much energy.
When the excessive signal ceases, all of the diodes can return to a relatively non-conducting state.
For example, diodes 44 and 46 can be discharged through inductive choke 48. Similarly, capacitor 39 a well as diodes 50 and 54 can be discharged through resistor 43 which is effectively connected in parallel across them.
With the just described embodiment, the bias current IT can be generated rather quickly (5 to 20 nanoseconds). However, the return to normal operation is designed to take somewhat longer, up to 1.2 microseconds, and is a function of the pulse width and the power level applied. This recovery time is limited by the time constant established by resistor 43. Also, another limiting factor is the recovery time associated with diodes 44, 46, 50 and 54, especially the latter g 1 two. Once these elements discharge the system is then in a condition to operate us originally described with power flowing from input Jo to output Jo, essentially no power being conveyed to power-dissipating element 26.
It is to be appreciated that various modifications may be implemented with respect to the above described preferred embodiment. For example, the power rating of the foregoing system can be changed by the expedient of specifying diodes with a different power rating or by placing more or fewer diodes in parallel to change the effective power rating Additionally, it is possible to change the size of the micro strip by simultaneously changing the dielectric constant of the underlying nonconductive material.
Also, while a directional coupler is shown driving the detector for producing bias current, alternate coupling techniques can be employed, including an ohmic connection. Also, in many cases a quarter or half wavelength line can be increased by multiples of half wavelengths without changing the effect of the system.
Also, while a 50 ohm characteristic impedance is disclosed, clearly, in alternate embodiments, other impedances can be employed. Furthermore, while a micro strip configuration has been shown, discrete hard I wired components, waveguid~ systems, strip line systems or coaxial cable systems can be employed depending upon the required power handling capability, reliability, weight and size limitations, etc. Additionally, the values of components and the specific components selected can be changed depending upon the required frequency, band width, power handling capability, temperature stability, accuracy, leakage requirement, interference immunity, etc. Also, wile the protector has been shown guarding the input to a radar receiver, any system for receiving an oscillating signal can be protected by the foregoing circuit. In addition, short ~Z~8:~9 1 circuits provided by the illustrated diodes can be accomplished by other devices including transistors, or other fast switching devices. It will be further appreciated that while in some instances a diode produces a shorting effect resulting in an open circuit, the length of awn associated transmission line can be altered so that an open/shorted diode can produce either an open or short circuit.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
I
The resent invention relates to overload protectors for preventing excessive radio-frequency energy, applied to an input, from reaching an output.
There are many applications in which a delicate input circuit must be protected from excessive voltages, current or power. For example, certain field effect transistors and other devices cannot tolerate excessive voltage at their inputs. Other examples include the input to certain receivers. For example, in aircraft weather radar systems, the input to a mixer can be damaged by excessive power emanating from nearby radio sources or reflected power originating from the radar itself. Radar systems are especially susceptible to overloading because they incorporate an antenna serving the dual function of transmitting relatively high energy pulses and receiving very faint signals of the same form. In the event such an antenna is damaged or broken off, it is likely that these high energy pulses will not be safely transmitted but will be coupled directly into the input of the radar receiver.
Such radar systems have been very difficult to protect. Known methods of protecting the radar have included rotating the weather radar antenna so it would not receive damaging signals from reflections or from other nearby, operating radar systems until the aircraft has left the heavily trafficked area. One unsuccessful method for protecting the radar system is to turn off its power. However, even when power has been removed, the radar front end and its sensitive components are still exposed to receipt of damaging energy from nearly high frequency sources.
' 1 A known technique for protecting a sensitive input is by shunting the input with one or more stages of pin diodes. A relatively large, radio frequency signal placed across the pin diodes will forward bias them. The forward biasing will persist because of the capacitance of the diode. This approach is inherently limited since this power mutt be absorbed by the pin diode which must -therefore have a high power rating.
Consequently, the pin diode tends to be rather slow and will allow substantial power to reach the protected circuit before the diode becomes effective. Moreover, pin diodes do not provide a perfect short but will only reduce the dynamic shunting impedance across the input of the protected circuit.
With high frequency circuits it is often desirable and practical to take advantage of the relatively short wavelengths of signals propagating through a circuit. For example, a -transmission line may have one end shorted or open but depending upon the effective electrical length of the transmission line, the other end can appear as either an open or short circuit. Similarly, depending upon the spacing of ports on a transmission line, either complete or no coupling will occur between ports. This phenomena is used in circulators, directional couplers and hybrid couplers.
These various effects can be produced with wave guides cables, micro strips, strip lines and through known equivalent circuits that simulate the effect of a transmission line.
Accordingly, there is need for a device for protecting a delicate circuit by interrupting a higher energy power flow more quickly and more completely than has been possible with systems of the prior art.
I
In accordance with the illustrative embodiment demonstrating features and advantages of the present invention, there is provided an overload protector for safely transferring signals from an input to an output.
The protector has a power-dissipating element, a detection means and a diversion means. The detection means it coupled to the input or providing a bias current in response to a signal at the input in excess of a predetermined magnitude. The diversion means is coupled to the input, the output, the power-dissipating element and the detection means. The diversion means can receive the bias current and, in response, redirect power at the input from the output to the power-dissipating element.
In one embodiment, protection is provided to a high frequency detection system having an antenna, a high frequency power source and a power-dissipating element. The detection system also has a phased means having at least a first, a second and a third port. The first and second ports are connected to the antenna and power source, respectively. The first port is phased to communicate with the second and third ports. The second and third ports, however, are phased to prevent communication between them. Also included is a processing means for responding to signals having a predetermined pattern to produce a detected signal. The detection system also has a protector means coupled to the power-dissipating element, the third port and the processing means for diverting signals issuing at the third port from the processing means to the power-dissipating element. Thus, the processing means is protected from excessive signals.
An embodiment of a protector according to the principles of the present invention can selectively transfer power from an input to an output. The :~Z~8~
1 protector employs a diversion transmission means coupled between the input and a power-di~sipating element for conveying power there between. A reflex means of the protector is coupled to the diversion transmission means for reflecting power thereon away from the power-dissipating means. The protector includes an operative means for altering the extent of reflection provided by the reflex means. Thus, the protector can divert power from the output to the power-dissipating 10 element-By employing devices of the foregoing type, a highly effective protector is achieved that can quickly and completely divert power from a protected circuit to power-dissipating component. In a preferred embodiment, the input is coupled through a directional coupler to a node marking the start of two quarter wavelength branches. One branch extending toward the protected circuit is shunted by a first limiter diode, the other line terminating in a power-dissipating resistor. A
controllable stub connected to this power-dissipating resistor has another shunting limiter diode connected at a spacing of one quarter wavelength from the power-dissipating resistor. Preferably, these diodes are forward biased by a Skeptic diode detector driven by the directional coupler. Thus, an excessive signal can effectively reconfigure the circuit to detour the damaging power.
The protector can be extremely fast since these Skeptic diodes can be designed to respond almost immediately to the excessive incoming power by producing a rectified current. The system, which is a passive apparatus, can be designed to switch off in five to twenty nanoseconds or better depending upon the components chosen and the input power to be switched off. In one constructed embodiment the protector was rated for handling 1.5 Kilowatts with a 16 microsecond ~2~119 l pulse width (duty cycle of .003) and a 1.2 microsecond recovery time.
By switching the power to an external load, the protector can be constructed from micro strips which might otherwise be damaged. Thus, notwithstanding unintended loading due to mismatching, a greatly improved power handling capability, about one order of magnitude greater, is achieved because the redirecting of power keeps real power at the diode an order of magnitude lower than the maximum rating of the diode.
BRIEF DESCRIPTION OF THE DRAWINGS
The above brief description, as well as other objects, features and advantages of the present invention, will be more fully appreciated by reference to the following detailed description of a presently preferred but nonetheless illustrative embodiment in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein:
Fig. l is a schematic block diagram of a high frequency detection system including an overload protector according to the principles of the present invention;
Fig. 2 is a more detailed schematic of the overload protector of Fig. l;
Fig. 3 is plan view of a micro strip version of the circuit of Fig. 2;
Fig. PA is a simplified, partial, equivalent circuit diagram illustrating some of the micro strip transmission lines ox Fig. 3 when power it being conveyed from input to output; and Fig. 4B is a circuit diagram similar to that of Fig. PA but showing conditions existing when power is being conveyed from the input to a power-dissipating element.
In Fig. 1 a high frequency detection system, such as an aircraft weather radar system, operating at 9.35 GHz, is illustrated. It will be understood that this environment is exemplary and various other sensitive systems operating at other frequencies can be protected instead. In this specification the term radio-frequency means frequencies above audio and below infrared. The illustrated radar system includes antenna 10 and magnetron 12 connected to a first port 14 and second port 16, respectively, of a phased means, shown herein as wave guide circulator 18. Circulator 18 is phased so that antenna 10 can communicate with either magnetron 12 or third port 20 but -third port 20 and magnetron 12 (a high frequency power source) do not intercommunicate.
Wave guide port 20 is connected through wave guide to coaxial cable transition 21 to input Jo of an overload protector comprising protection means 24 and power-dissipating element 26. Transition 21 may be a commercially available device in which a wave guide terminates with an internal conductive probe acting as the center line of a coaxial cable. The output Jo of protector 24 connects to the input of a processing means, shown herein as the front end or mixer of a radar receiver. Mixer 28 and its associated circuitry may be the conventional radar circuit found in an aircraft weather radar system, although other sensitive circuits may be protected instead.
Referring to Fig 2, the previously mentioned overload protector is illustrated in a more detailed schematic diagram showing power-dissipating element 26 as an external grounded load. Element 26 is connected to connector Jo which may be an OSM-type of connector.
Input Jo (an OSM-type female connector) connects to one port of directional coupler 30 whose corresponding port Lo l19 1 connects to node A. The two other corresponding ports of directional coupler 30 are separately connected to a matching 50 ohm resistor 32 and to the input of a matching network 34. Matching network 34 is designed to correct impedance mismatches that might otherwise exist between the circuitry served by it. The input Jo is designed to work into a 50 ohm characteristic impedance.
Directional coupler 30 is designed to have a -33dB
coupling between input Jo and the input of matching network 34. Directional couplers such as coupler 30 are known per so. See for example, Members of the Staff of the Radar School, MUTT., Principles of Radar, McGraw ill Book Co., Inch (1952). pp. 834-39; Dr. Max Fogies, Modern Microelectronics, Research and Education Association, New York, New York (1972) pp. 222-25. As explained in those references, directional couplers can be Fabricated from wave guides, cables, strip lines or micro strips and the same phenomena can be produced with an equivalent circuit composed of inductors and capacitors. In this embodiment, directional coupler 30 is designed to afford duplex communication between input Jo and node A.
The output of matching network 34 connects to a detection means (also referred to as an operative mean) in the form of a pair of unidirectional conducting devices 36 and 38. Devices 36 and 38 are preferably Skeptic diodes (for example type DMJ, manufactured ho Alpha Industries of Woburn, Maws.) having both of their anodes connected to the output of matching network 34.
A low past filter means includes a shunting storage capacitor 39 connecting between ground (that is, a reference potential and the junction of test point TO
and the cathodes of diodes 36, 38. The filter means includes an inductor or chose 40 connecting between test point TO and node C. Also, 68 ohm carbon composition, direct-current return resistor 43 it shown connected I
between ground and test point TO.
Configured in this fashion, a sufficiently large signal at input Jo can forward bias diodes 36 and 38 which then act as detectors for producing a voltage across capacitor 39 and a bias current Is through inductor 40 to node C.
Node C is coupled through beam lead capacitor 42 (10 pi) to the anodes of parallel limiter diodes 44 and 46 whose cathodes are grounded. For the specified operating frequency diode 44 may have a recovery time of 20 nanoseconds and diode 46, 10 nanoseconds. Diodes 44 and 46 may be pin diodes, type numbers COLA 3132-02 and COLA 3131-01 respectively, by Alpha Industries of Woburn, Mass. A direct current return is provided by inductor 48 which connects between ground and the junction of the anodes of limiter diodes 44 and 46 and the output connector Jo.
The balance of the circuitry of Fig. 2 is herein referred to as a diversion means. Line A-C between nodes A and C is referred to herein as a main (or as a third) transmission means. Line A-C is preferably a quarter wavelength transmission line which may be formed from micro strips, although embodiments employing wave guides, cables or other equivalent circuits are possible. A variable impedance is provided by a semiconductor, limiting diode 50, herein referred to as a cancellation (or as an interrupt) means. Limiting diode 50 has its anode connected to node C and its cathode grounded. In one preferred embodiment, diode 50 is a pin diode, type COLA 3133-03 manufactured by Alpha Industries, Woburn, Mass., having a recovery time of 50 Nina seconds. Another quarter wavelength line segment between nodes A and B, line segment A-B, is similar to line A-C and is referred to as a diversion transmission means. Node B is coupled through capacitor 52 (a capacitor identical to capacitor ..~,~
mob/
~23~
1 42) and OHM connectors I to 50 ohm matching termination 26. Line B-D, a second transmission means connected between nodes B and D, is another quarter line similar to the two other lines, line A-C and line By A
S shunting means (also referred to as a reloading or reflex means) is shown as a shunting diode 54 with its anode connected to node D and its cathode grounded.
Diode 54 is a semiconductor providing variable impedance (that is, an impedance varying diode) and may be identical to previously mentioned diode 50. A fourth transmission means, line D-E, is connected between node D and node E and is serially connected with line B-D to form a line stub. In a referred embodiment line D-E is effectively one half wavelength long.
Referring to Fig. 3, a practical embodiment of the circuit of Fig. 2 is illustrated as a micro strip circuit. It will be understood that this circuit could be fabricated with discrete components where the various transmission lines are synthesized by an equivalent circuit, especially for lower frequencies. Alterna-lively, the circuit could be made with wave guide although the latter would be substantially more difficult to fabricate. The illustrated circuit employs a four-walled aluminum frame 60 onto which are mounted the three previously mentioned OSM-type connectors Jo, Jo and Jo'; The outer conductive cowls of connectors Jo, Jo and Jo are screw mounted to aluminum frame 60.
The interior circuitry is mounted on a micro strip board comprising an aluminum ground plane I
electrically and physically connected to frame 60 and having the same outside dimensions as it. On the side of frame 60 opposite plane 62 an identically sized aluminum cover plate (not shown) is attached by screws to the frame. Ground plane 62 has laminated to its inside face a low loss dielectric material, preferably composed of polytetrafluoroethylene which is .010 inch 1 thick. The various conductive strips illustrated upon dielectric material 64 are metal laminations which may be photo chemically etched into the pattern shown.
Micro strip board material can be obtained from Rogers Co., of Chandler, Arizona, the dielectric material being referred to as RT/Duroid 5880. In this schematic components previously described in Fig. 2 bear identical reference numerals.
The majority of the illustrated strip lines are dimensioned to provide a 50 ohm characteristic impedance. Specifically, the strip lines aligned between connectors Jo and Jo, the previously mentioned lines A-B, B-D, D-E, as well as the line between connector Jo' and node B, are all designed to have a 50 ohm characteristic impedance. The width of these 50 ohm strip lines it .031 inch. Similarly designed is the strip line AYE running between elements AYE and 32 in the directional coupler.
The directional coupler 30 includes a strip AYE
which is spaced about .035 inch from strip 30B for approximately 0.225 inch. Directional coupler 30 is designed to operate at an input frequency of 9.3S GHz with -33dB coupling from input Jo to element AYE. The right end yin thy view) of strip AYE is terminated ho previously mentioned chip nest ion 32 which connect to grounded pad 66. Pad 66 is a metal lamination resting atop dielectric material 64 hut having a slot cut there through and reaching the aluminum ground plane 62.
This typical slot is approximately 0.13 inch long and 0.031 inch wide with rounded end. The slot is connected to ground plane I by soldering pad 66 to the ground plane 62.
Previously mentioned matching network 34 is shown herein a shunting capacitive element AYE, a widened metallic pad for capacitively shunting signals to the underlying ground plane 62. A strip line also .~31 if 1 inch wide) then reaches from shunting capacitor AYE to previously mentioned Skeptic diodes 36, 38, shown herein as a parallel combination, hermetically sealed into a common package by the manufacturer. The strip 34C between component AYE and 36 is shunted about approximately two thirds of the way towards component 36 by strip line inductor 34B which connects to grounding pad 68, a pad again having a soldering slot for connecting to ground plane 62. Strip 3~B is a quarter wave direct-current return acting as a radio-fre~uency choke. Components AYE and 34C provide an impedance matching network so that the 50 ohm strip line from strip AYE is matched to the lower impedance presented by Skeptic diodes 36, 38. The dimensions and thus the values of elements AYE and 34C are selected according to the impedance at diodes 36, 38.
A shunting storage capacitor 39 is formed by the area of pad 39 which is approximately .04 square inch.
Previously mentioned direct-current return resistor 43 connects between pad 39 and the illustrated (typical) slot in grounded pad 70. A strip inductor, .007 inch wide and .242 inch long connects between pad 70 and the strip line running between connector Jo and diode I at a point nearer to the diode. Diode 46 is generally in the shape of a cubical chip waving terminals formed on opposing faces. Its cathode face is solder-connected to ground plane 62 exposed through the slot AYE cut through dielectric material I Area 72 is grounded to prevent bypass currents. The anode of diode 46 is connected to the micro strip on either side of slot AYE by a 99-99%
pure gold ribbon, .005 inch by .0025 inch. A gap in the micro strip between diodes I and 50 is spanned by beam lead capacitor 42. Previously mentioned diodes 44 and 50 are situated in slots AYE and AYE, respectively, (similar to slot AYE so that each of their cathodes connect to ground plane 62. Again, their anodes connect I
1 to a gold ribbon spanning the slows AYE and AYE.
The anode of diode 50 connects to previously mentioned node C. The micro strip between nodes C and A
is the previously mentioned quarter wavelength trays-mission strip and is, in -this embodiment, approximately 0.190 winch long, in view of the operating frequency of 9.35 GHz. Of approximately the same length is the perpendicular micro strip line running from node A to node B. Soldered between node B and strip 74 is beam lead capacitor 52. Strip 74 leads to load connector Jo'. The strip between node B and node D is similar in length to line A-B. At node D limiter diode 54 is soldered within slot AYE atop ground plane 62. Again, the anode of diode 54 connects to a gold ribbon spanning either side of slot AYE. A folded micro strip between node D and E is approximately twice the length of strip B-D and is open at node E.
To facilitate an understanding of the principles associated with the foregoing apparatus, the operation of the equipment of Figs. 1, 2 and 3 will be explained using the simplified schematic of Figs. PA and 4B. In Fig. 1, circulator 18 operates such that high frequency power from magnetron 12 is transferred to antenna 10 in short bursts without coupling a significant signal into port 20. Signal reflected ho targets eventually cause a return to be received by antenna 10 and coupled through circulator 18 into port 20. After passing through transition 21 the return signal is coupled to input connector Jo of protector 24.
The relatively small signal appearing at connector Jo does not produce a sufficient signal to charge capacitor 39 fig. 2). Accordingly, any current IT through inductor 40 is negligible. Thus diode 54 and 50 are not forward biased and remain essentially a very high impedance Jan open circuit). As a result, the open circuit at node still appears as an open circuit at 1 node D. One quarter wavelength therefrom at node B this open circuit appears like a short across load 26. This short at node B causes the line By to appear like an open circuit from node A. Since there are no other S diode or other components shunting the energy in the micro strip connection between connectors Jo and Jo, signals are conveyed without reflection between those connectors. An equivalent circuit of the micro strip under these conditions is shown in Fig. PA, wherein node B is shown grounded to produce what appears to be an open circuit when viewed from node A.
Referring again to Fig. 1, we now assume that the magnetron pulse applied to antenna 10 is reflected back into port 14 due to a nearby obstruction or due to damage to antenna 10. This pulse is therefore at a relatively high power level. Alternatively, a nearby radar signal, a likely happening at a crowded airport, can be directed into antenna 10 to produce an excessive signal at port 14. Consequently, an excessive signal it conveyed from port 20 to connector Jo. This pulse may typically rise at the rate of 10 watts per nanosecond.
Accordingly, a significant amount of energy is coupled from the directional coupler 30 (Fig. 2) through matching network 34 to detecting diodes I 3B. The high speed rectification provided by them causes a rapid charging o capacitor 39. Consequently, a bias current IBM eventually reaching about 60 ma flows through inductor 40 and forward biases diodes 54 and 50. This current dramatically reduces their dynamic impedance and presents an effective short circuit from their anode to cathodes. These effective short circuits cause the grounding of the micro strips as illustrated in Fig. 4B.
Nodes C and D have been grounded by their respective limiter diodes as illustrated in Figs. 2 an 4B. Since the line A-C, having its nod C grounded, it a quarter wavelength long, the effect of line A-C as seen from ~Z~8~1~
1 node A is that of an open circuit. Similarly, line B-D
has its node D grounded so that the line appears from node B as an open circuit. Consequently, there is an undisturbed signal path from input connector Jo -through S line A-B and connector Jo to power-dissipating element 26. Therefore, the excessive power on connector Jo is dissipated externally. Moreover, the effective open circuit presented by line A-C provides excellent isolation to keep destructive power from ever reaching the protected circuits.
It will be appreciated that as the input power rises, should any of it leak past line A-C, additional protection is provided by diodes 44 and 46 (Fig. 2).
Such leaked power can forward bias diodes 44 and 46.
These diodes have a certain amount of capacitance so that they effectively remain forward biased to shunt power so that any signal reaching output connector Jo is relatively small. Significantly, diode 44 and especially diode 46, can be selected to have a very fast response since these diodes need not dissipate much energy.
When the excessive signal ceases, all of the diodes can return to a relatively non-conducting state.
For example, diodes 44 and 46 can be discharged through inductive choke 48. Similarly, capacitor 39 a well as diodes 50 and 54 can be discharged through resistor 43 which is effectively connected in parallel across them.
With the just described embodiment, the bias current IT can be generated rather quickly (5 to 20 nanoseconds). However, the return to normal operation is designed to take somewhat longer, up to 1.2 microseconds, and is a function of the pulse width and the power level applied. This recovery time is limited by the time constant established by resistor 43. Also, another limiting factor is the recovery time associated with diodes 44, 46, 50 and 54, especially the latter g 1 two. Once these elements discharge the system is then in a condition to operate us originally described with power flowing from input Jo to output Jo, essentially no power being conveyed to power-dissipating element 26.
It is to be appreciated that various modifications may be implemented with respect to the above described preferred embodiment. For example, the power rating of the foregoing system can be changed by the expedient of specifying diodes with a different power rating or by placing more or fewer diodes in parallel to change the effective power rating Additionally, it is possible to change the size of the micro strip by simultaneously changing the dielectric constant of the underlying nonconductive material.
Also, while a directional coupler is shown driving the detector for producing bias current, alternate coupling techniques can be employed, including an ohmic connection. Also, in many cases a quarter or half wavelength line can be increased by multiples of half wavelengths without changing the effect of the system.
Also, while a 50 ohm characteristic impedance is disclosed, clearly, in alternate embodiments, other impedances can be employed. Furthermore, while a micro strip configuration has been shown, discrete hard I wired components, waveguid~ systems, strip line systems or coaxial cable systems can be employed depending upon the required power handling capability, reliability, weight and size limitations, etc. Additionally, the values of components and the specific components selected can be changed depending upon the required frequency, band width, power handling capability, temperature stability, accuracy, leakage requirement, interference immunity, etc. Also, wile the protector has been shown guarding the input to a radar receiver, any system for receiving an oscillating signal can be protected by the foregoing circuit. In addition, short ~Z~8:~9 1 circuits provided by the illustrated diodes can be accomplished by other devices including transistors, or other fast switching devices. It will be further appreciated that while in some instances a diode produces a shorting effect resulting in an open circuit, the length of awn associated transmission line can be altered so that an open/shorted diode can produce either an open or short circuit.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
I
Claims (40)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An overload protector, operating at at least a radio-frequency for safely transferring signals from an input to an output, said overload protector producing the power required for operation of said overload protector entirely from a signal at said input in excess of a predetermined magnitude, said overload protector comprising:
a power-dissipating element;
a detection means coupled to said input for producing a bias current in response to a signal at the input in excess of a predetermined magnitude; and diversion means coupled to said input, to said output, to said power-dissipating element and to said detection means for receiving said bias current, said diversion means being operable in response to said bias current to redirect power at said input away from said output to said power-dissipating element.
a power-dissipating element;
a detection means coupled to said input for producing a bias current in response to a signal at the input in excess of a predetermined magnitude; and diversion means coupled to said input, to said output, to said power-dissipating element and to said detection means for receiving said bias current, said diversion means being operable in response to said bias current to redirect power at said input away from said output to said power-dissipating element.
2. An overload protector according to claim 1 wherein said diversion means comprises:
a variable impedance coupled to said detection means to receive said bias current, said variable impedance being coupled to said input for varying direction of power flowing therefrom in response to said bias current.
a variable impedance coupled to said detection means to receive said bias current, said variable impedance being coupled to said input for varying direction of power flowing therefrom in response to said bias current.
3. An overload protector according to claim 2 further comprising:
low pass filter means coupled between said detection means and said variable impedance for passing low frequency and direct-current components of said bias current to said variable impedance.
low pass filter means coupled between said detection means and said variable impedance for passing low frequency and direct-current components of said bias current to said variable impedance.
4. An overload protector according to claim 3 wherein the signal at said input is repetitive and wherein said detection means comprises:
a unidirectional conducting device coupled between said input and said filter means.
a unidirectional conducting device coupled between said input and said filter means.
5. An overload protector according to claim 4 wherein said variable impedance comprises a diode.
6. An overload protector according to claim 1 wherein said diversion means includes:
reloading means connected to said power-dissipating element for gating thereto signals from said input in response to said bias current.
reloading means connected to said power-dissipating element for gating thereto signals from said input in response to said bias current.
7. An overload protector according to claim 6 wherein said diversion means further comprises:
a diversion transmission means coupled between said input and said power-dissipating element for conveying signals therebetween; and a second transmission means coupled between said reloading means and said power-dissipating element for conveying signals therebetween, said diversion transmission means and second transmission means each being in effect longer than one-eighth of the wavelength of the radio frequency signals therein.
a diversion transmission means coupled between said input and said power-dissipating element for conveying signals therebetween; and a second transmission means coupled between said reloading means and said power-dissipating element for conveying signals therebetween, said diversion transmission means and second transmission means each being in effect longer than one-eighth of the wavelength of the radio frequency signals therein.
8. An overload protector according to claim 7 wherein said diversion transmission means is in effect an odd multiple of quarter wavelengths long.
9. An overload protector according to claim 8 wherein said second transmission means is in effect an odd multiple of quarter wavelengths long.
10. An overload protector according to claim wherein said diversion means comprises:
interrupt means for decoupling said input and output in response to said bias current; and a third transmission means coupled between said interrupt means input and the junction of said input and said first transmission means for conveying signals therebetween, said third transmission means being in effect an odd multiple of quarter wavelengths long.
interrupt means for decoupling said input and output in response to said bias current; and a third transmission means coupled between said interrupt means input and the junction of said input and said first transmission means for conveying signals therebetween, said third transmission means being in effect an odd multiple of quarter wavelengths long.
11. An overload protector according to claim 10 wherein said diversion means comprises:
a fourth transmission means, open at one end and connected at its other end to the junction of said reloading means and said second transmission means, said fourth transmission means being in effect a multiple of half-wavelengths in length.
a fourth transmission means, open at one end and connected at its other end to the junction of said reloading means and said second transmission means, said fourth transmission means being in effect a multiple of half-wavelengths in length.
12. An overload protector according to claim 1 further comprising:
a directional coupler having two pairs of ports, duplex transmission occurring within each pair, one pair being separately connected to said input and said diversion means, from the other pair of ports at least one of said ports being connected to said detection means.
a directional coupler having two pairs of ports, duplex transmission occurring within each pair, one pair being separately connected to said input and said diversion means, from the other pair of ports at least one of said ports being connected to said detection means.
13. An overload protector according to claim 12 further comprising:
a limiter diode connected between a reference potential and the junction between said output and said diversion means.
a limiter diode connected between a reference potential and the junction between said output and said diversion means.
14. An overload protector according to claim 13 wherein said diversion means comprises:
reloading means connected to said power-dissipating element for coupling thereto signals of said input in response to said bias current; and interrupt means for decoupling said input and output in response to said bias current.
reloading means connected to said power-dissipating element for coupling thereto signals of said input in response to said bias current; and interrupt means for decoupling said input and output in response to said bias current.
15. An overload protector according to claim 14 wherein said detection means comprises a relatively high-speed Schottky diode.
16. An overload protector according to claim 14 wherein said reloading means and said interrupt means each comprise:
an impedance varying diode connected for forward biasing by said bias current.
an impedance varying diode connected for forward biasing by said bias current.
17. An overload protector according to claim 26 wherein said diversion means further comprises:
a diversion transmission means coupled between said input and said power-dissipating element for conveying signals therebetween; and a second transmission means coupled between said reloading means and said power-dissipating element for conveying signals therebetween, said diversion transmission means and second transmission means each being in effect longer than one-eighth of the wavelength of the radio frequency signals therein.
a diversion transmission means coupled between said input and said power-dissipating element for conveying signals therebetween; and a second transmission means coupled between said reloading means and said power-dissipating element for conveying signals therebetween, said diversion transmission means and second transmission means each being in effect longer than one-eighth of the wavelength of the radio frequency signals therein.
18. An overload protector according to claim 27 wherein said diversion transmission means is in effect an odd multiple of quarter wavelength long.
19. An overload protector according to claim 1 further comprising:
a radio frequency source;
an antenna; and a circulator having at least three ports, one of said ports being connected to said antenna, the other two ports being (a) in communication with the antenna but not with each other, and (b) separately connected to said radio frequency source and said input.
a radio frequency source;
an antenna; and a circulator having at least three ports, one of said ports being connected to said antenna, the other two ports being (a) in communication with the antenna but not with each other, and (b) separately connected to said radio frequency source and said input.
20. A radio frequency detection system comprising:
a radio frequency power source;
an antenna;
phased means having at least a first, second and third port, said first and second ports being connected to said antenna and power source, respectively, said first port being phased to communicate with said second and third port, said second and third ports being phased to prevent communication between themselves;
a power-dissipating element a processing means for responding to signals having a predetermined pattern to produce a detected signal; and a protector means coupled to said power-dissipating element, said third port and said processing means for diverting signals issuing at said third port away from said processing means to said power-dissipating element, whereby said processing means is protected from input signals in excess of a predetermined magnitude.
a radio frequency power source;
an antenna;
phased means having at least a first, second and third port, said first and second ports being connected to said antenna and power source, respectively, said first port being phased to communicate with said second and third port, said second and third ports being phased to prevent communication between themselves;
a power-dissipating element a processing means for responding to signals having a predetermined pattern to produce a detected signal; and a protector means coupled to said power-dissipating element, said third port and said processing means for diverting signals issuing at said third port away from said processing means to said power-dissipating element, whereby said processing means is protected from input signals in excess of a predetermined magnitude.
21. A radio frequency detection system according to claim 20 wherein said phased means comprises a waveguide circulator and said protector means comprises a microstrip circuit, said system further comprising:
a waveguide to microstrip transition.
a waveguide to microstrip transition.
22. A radio frequency detection system according to claim 20 wherein said protector means comprises:
a first transmission strip, effectively one-quarter wavelength long, coupled between said third port and said power-dissipating element for conveying signals therebetween;
a shunting diode; and a second transmission strip, effectively one-quarter wavelength long, coupled between one terminal of said shunting diode and the junction of said power-dissipating element and said first transmission strip.
a first transmission strip, effectively one-quarter wavelength long, coupled between said third port and said power-dissipating element for conveying signals therebetween;
a shunting diode; and a second transmission strip, effectively one-quarter wavelength long, coupled between one terminal of said shunting diode and the junction of said power-dissipating element and said first transmission strip.
23. A radio frequency detection system according to claim 22 further comprising:
a limiting diode having one terminal coupled to said processing means;
a third transmission strip, effectively one-quarter wavelength long, coupled between said third port and the junction of said limiting diode and said processing means;
and a fourth transmission strip, effectively a multiple of half wavelengths long having one end open and the other end connected to the junction of said shunting diode and said second transmission strip.
a limiting diode having one terminal coupled to said processing means;
a third transmission strip, effectively one-quarter wavelength long, coupled between said third port and the junction of said limiting diode and said processing means;
and a fourth transmission strip, effectively a multiple of half wavelengths long having one end open and the other end connected to the junction of said shunting diode and said second transmission strip.
24. A protector operating at at least a radio frequency for selectively transferring power from an input to an output, comprising:
a main transmission means coupled between said input and output for conveying power there between;
a power-dissipating element;
a diversion transmission means coupled between said input and said power-dissipating element for conveying power there between;
a reflex means coupled to said diversion transmission means for reflecting power on said diversion transmission means away from said power-dissipating element;
and an operative means for producing a bias current altering the extent of reflection provided by said reflex means, whereby said protector can divert power away from said output to said power-dissipating element.
a main transmission means coupled between said input and output for conveying power there between;
a power-dissipating element;
a diversion transmission means coupled between said input and said power-dissipating element for conveying power there between;
a reflex means coupled to said diversion transmission means for reflecting power on said diversion transmission means away from said power-dissipating element;
and an operative means for producing a bias current altering the extent of reflection provided by said reflex means, whereby said protector can divert power away from said output to said power-dissipating element.
25. A protector according to claim 24 further comprising:
a cancellation means coupled to said main transmission means for reflecting power thereon away from said output, said operative means being operable to alter simultaneously the extent of reflection provided by said reflex and cancellation means.
a cancellation means coupled to said main transmission means for reflecting power thereon away from said output, said operative means being operable to alter simultaneously the extent of reflection provided by said reflex and cancellation means.
26. A protector according to claim 24 wherein said diversion transmission means includes:
a line segment, its length effectively one-quarter of the wavelength of signals thereon, coupled between said power-dissipating element and said input, said operative means being operable to short said power-dissipating element.
a line segment, its length effectively one-quarter of the wavelength of signals thereon, coupled between said power-dissipating element and said input, said operative means being operable to short said power-dissipating element.
27. A protector according to claim 26, wherein said reflex means comprises:
a line stub, its length effectively three-quarters of the wavelength of signals thereon, having one end open and the other end connected to said power-dissipating element;
and a shunt means coupled at a mid-section of said line stub for shorting it at an effective distance from said power-dissipating element of one-quarter of the wavelength of signals thereon.
a line stub, its length effectively three-quarters of the wavelength of signals thereon, having one end open and the other end connected to said power-dissipating element;
and a shunt means coupled at a mid-section of said line stub for shorting it at an effective distance from said power-dissipating element of one-quarter of the wavelength of signals thereon.
28. An overload protector operating at at least a radio frequency for safely transferring signals from an nut to an output, comprising:
a power-dissipating element;
a detection means coupled to said input for producing a bias current in response to a signal at the input in excess of predetermined magnitude;
diversion means coupled to said input, to said output, to said power-dissipating element and to said detection means for receiving said bias current, said diversion means being operable in response to said bias current to redirect power at said input away from said output to said power-dissipating element; and a directional coupler having two pairs of ports, duplex transmission occurring within each pair, one pair being separately connected to said input and said diversion means, from the other pair of ports at least one of said ports being connected to said detection means.
a power-dissipating element;
a detection means coupled to said input for producing a bias current in response to a signal at the input in excess of predetermined magnitude;
diversion means coupled to said input, to said output, to said power-dissipating element and to said detection means for receiving said bias current, said diversion means being operable in response to said bias current to redirect power at said input away from said output to said power-dissipating element; and a directional coupler having two pairs of ports, duplex transmission occurring within each pair, one pair being separately connected to said input and said diversion means, from the other pair of ports at least one of said ports being connected to said detection means.
29. An overload protector according to claim 28 further comprising:
a limiter diode connected between a reference potential and the junction between said output and said diversion means.
a limiter diode connected between a reference potential and the junction between said output and said diversion means.
30. An overload protector according to claim 29 wherein said diversion means comprises:
reloading means connected to said power-dissipating element for coupling thereto signals of said input in response to said bias current; and interrupt means for decoupling said input and output in response to said bias current.
reloading means connected to said power-dissipating element for coupling thereto signals of said input in response to said bias current; and interrupt means for decoupling said input and output in response to said bias current.
31. An overload protector according to claim 30 wherein said detection means comprises a relatively high-speed Schottky diode.
32. An overload protector according to claim 30 wherein said reloading means and said interrupt means each comprise:
an impedance varying diode connected for forward biasing by said bias current.
an impedance varying diode connected for forward biasing by said bias current.
33. An overload protector according to claim 32 wherein said diversion means further comprises:
a diversion transmission means coupled between said input and said power-dissipating element for conveying signals there between; and a second transmission means coupled between said reloading means and said power-dissipating element for conveying signals there between, said diversion transmission means and second transmission means each being in effect longer than one-eighth of the wavelength of the radio frequency signals therein.
a diversion transmission means coupled between said input and said power-dissipating element for conveying signals there between; and a second transmission means coupled between said reloading means and said power-dissipating element for conveying signals there between, said diversion transmission means and second transmission means each being in effect longer than one-eighth of the wavelength of the radio frequency signals therein.
34. An overload protector according to claim 33 wherein said diversion transmission means is in effect an odd multiple of quarter wavelengths long.
35. An overload protector operating at at least a radio-frequency for safely transferring signals from an input to an output, comprising;
a power-dissipating element;
a detection means coupled to said input for providing a bias current in response to a signal at the input in excess of a predetermined magnitude;
diversion means coupled to said input, to said output, to said power-dissipating element and to said detection means for receiving said bias current, said diversion means being operable in response to said bias current to redirect power at said input away from said output to said power-dissipating element:
a radio frequency source;
an antenna; and a circulator having at least three ports, one of said ports being connected to said antenna, the other two ports being (a) in communication with the antenna but not with each other, and (b) separately connected to said radio frequency source and said input.
a power-dissipating element;
a detection means coupled to said input for providing a bias current in response to a signal at the input in excess of a predetermined magnitude;
diversion means coupled to said input, to said output, to said power-dissipating element and to said detection means for receiving said bias current, said diversion means being operable in response to said bias current to redirect power at said input away from said output to said power-dissipating element:
a radio frequency source;
an antenna; and a circulator having at least three ports, one of said ports being connected to said antenna, the other two ports being (a) in communication with the antenna but not with each other, and (b) separately connected to said radio frequency source and said input.
36. An overload protector operating at at least a radio frequency for safely transferring signals from an input to an output, comprising:
a power-dissipating element;
a detection means coupled to said input for providing a bias current in response to a signal at the input in excess of a predetermined magnitude;
diversion means coupled to said input, to said output, to said power-dissipating element and to said detection means for receiving said bias current, said diversion means being operable in response to said bias current to redirect power at said input away from said output to said power dissipating element, said diversion means including reloading means connected to said power-dissipating element for grating thereto signals from said input in response to said bias current, said diversion means comprising:
a diversion transmission means coupled between said input and said power-dissipating element for conveying signals there between and a second transmission means coupled between said reloading means and said power-dissipating element for conveying signals there between, said diversion transmission means and second transmission means each being in effect longer than one of the wavelength of the radio frequency signals therein.
a power-dissipating element;
a detection means coupled to said input for providing a bias current in response to a signal at the input in excess of a predetermined magnitude;
diversion means coupled to said input, to said output, to said power-dissipating element and to said detection means for receiving said bias current, said diversion means being operable in response to said bias current to redirect power at said input away from said output to said power dissipating element, said diversion means including reloading means connected to said power-dissipating element for grating thereto signals from said input in response to said bias current, said diversion means comprising:
a diversion transmission means coupled between said input and said power-dissipating element for conveying signals there between and a second transmission means coupled between said reloading means and said power-dissipating element for conveying signals there between, said diversion transmission means and second transmission means each being in effect longer than one of the wavelength of the radio frequency signals therein.
37. An overload protector according to claim 36 wherein said diversion transmission means is in effect an odd multiple of quarter wavelengths long.
38. An overload protector according to claim 37 wherein said second transmission means is in effect an odd multiple of quarter wavelengths long.
39. An overload protector according to claim 38 wherein said diversion means comprises:
interrupt means for decoupling said input and output in response to said bias current; and a third transmission means coupled between said interrupt means input and the junction of said input and said diversion transmission means for conveying signals there between, said third transmission means being in effect an odd multiple of quarter wavelengths long.
interrupt means for decoupling said input and output in response to said bias current; and a third transmission means coupled between said interrupt means input and the junction of said input and said diversion transmission means for conveying signals there between, said third transmission means being in effect an odd multiple of quarter wavelengths long.
40. An overload protector according to claim 39 wherein said diversion means comprises:
a fourth transmission means open at one end and connected at its other end to the junction of said reloading means and said second transmission means, said fourth transmission means being in effect a multiple of half wavelengths in length.
a fourth transmission means open at one end and connected at its other end to the junction of said reloading means and said second transmission means, said fourth transmission means being in effect a multiple of half wavelengths in length.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US58981284A | 1984-03-15 | 1984-03-15 | |
| US589,812 | 1990-09-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1218119A true CA1218119A (en) | 1987-02-17 |
Family
ID=24359637
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456624A Expired CA1218119A (en) | 1984-03-15 | 1984-06-14 | Overload protector |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1218119A (en) |
| DE (1) | DE3507779A1 (en) |
| GB (1) | GB2156176B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3618170A1 (en) * | 1986-05-30 | 1987-12-03 | Rohde & Schwarz | Arrangement for suppressing the transmission frequency of a radio-frequency transmitter at the input of an adjacent receiver |
| US4930035A (en) * | 1989-04-03 | 1990-05-29 | Raytheon Company | Radio frequency limiter circuit |
| IT1231205B (en) * | 1989-04-03 | 1991-11-23 | Selenia Ind Elettroniche | MICROWAVE SWITCH WITH PROTECTION FUNCTION OF DOWNSTREAM DEVICES, EVEN WITH THE DEVICE OFF |
| FI90478C (en) * | 1992-03-09 | 1994-02-10 | Lk Products Oy | Filter |
| US5432489A (en) * | 1992-03-09 | 1995-07-11 | Lk-Products Oy | Filter with strip lines |
| US6366766B1 (en) * | 2000-05-12 | 2002-04-02 | Tektronix, Inc. | Input protection circuit for a radio frequency |
| DE102010060581A1 (en) * | 2010-11-16 | 2012-05-16 | Telefunken Radio Communication Systems Gmbh & Co. Kg | Circuit for protecting high frequency electrical or electronic components of e.g. wireless local area network apparatus against over voltage, has short circuit branch lines galvanically secured against ground potential |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3495180A (en) * | 1966-12-09 | 1970-02-10 | Itt | Amplitude control circuit |
| US3518585A (en) * | 1966-12-30 | 1970-06-30 | Texas Instruments Inc | Voltage controlled a.c. signal attenuator |
| GB1278231A (en) * | 1970-01-10 | 1972-06-21 | Plessey Co Ltd | Improvements in and relating to feedback control systems |
| GB1359392A (en) * | 1972-03-17 | 1974-07-10 | United Aircraft Corp | Aircraft navigation receiver apparatus |
| AU482123B2 (en) * | 1972-11-24 | 1977-03-23 | Amalgamated Wireless (Australasia) Limited | Radio receiver protection arrangement |
| JPS51117816A (en) * | 1975-04-09 | 1976-10-16 | Sony Corp | Receiver |
| US4158814A (en) * | 1977-09-08 | 1979-06-19 | General Research Of Electronics, Inc. | Automatic overload protection system |
-
1984
- 1984-06-14 CA CA000456624A patent/CA1218119A/en not_active Expired
- 1984-07-12 GB GB08417763A patent/GB2156176B/en not_active Expired
-
1985
- 1985-03-05 DE DE19853507779 patent/DE3507779A1/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| GB2156176B (en) | 1988-06-22 |
| DE3507779A1 (en) | 1985-09-26 |
| GB8417763D0 (en) | 1984-08-15 |
| GB2156176A (en) | 1985-10-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |