GB2240695A - Interference cancellation system for radio receiver - Google Patents
Interference cancellation system for radio receiver Download PDFInfo
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- GB2240695A GB2240695A GB9027438A GB9027438A GB2240695A GB 2240695 A GB2240695 A GB 2240695A GB 9027438 A GB9027438 A GB 9027438A GB 9027438 A GB9027438 A GB 9027438A GB 2240695 A GB2240695 A GB 2240695A
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- receiver
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- transmission line
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/12—Neutralising, balancing, or compensation arrangements
- H04B1/123—Neutralising, balancing, or compensation arrangements using adaptive balancing or compensation means
- H04B1/126—Neutralising, balancing, or compensation arrangements using adaptive balancing or compensation means having multiple inputs, e.g. auxiliary antenna for receiving interfering signal
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- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Noise Elimination (AREA)
Abstract
The system is connected to a radio receiver system having transmission line 34 interconnecting a receiver antenna 30 and a receiver 32, and the interference cancellation system includes a directional coupler 38 connected to an auxiliary antenna 36, a directional coupler 48 connected to transmission line 34, a synchronous detector 42 with inputs connected to couplers 38, 48, a signal controller 46 with inputs connected to coupler 38 and detector 42, and a subtractor, 52 which injects into the transmission line 34 an interference cancellation signal provided by controller 46. In order to prevent cancellation of the desired signal when only that signal is present, the receiver antenna 30 is directional, the auxiliary antenna 36 is omnidirectional and the gain of the interference cancellation system from antenna 36 to subtractor 52 is less than the gain of antenna 30 within a predetermined angle of its boresight. Alternatively the antenna pattern of the auxiliary antenna 36 has a null, this null and the boresight of the directional receiver antenna 30 being directed to the desired signal source, (Figs 3, 4). The antennas 30, 36 may be coaxially mounted together. <IMAGE>
Description
INTERFERENCE CANCELLATION SYSTEM FOR INTERFERENCE SIGNALS
HAVING AN ARBITRARY AND UNKNOWN DURATION AND DIRECTION
CROSS REFERENCE TO RELATED APPLICATIONS
Reference is made to U.S. Patent Application entitled "Highly Directive Radio Receiver Employing Relatively Small
Antennas", by A. Talwar, filed concurrently herewith, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to radio communication systems and methods, and more particularly relates to interference cancelling systems and methods for minimizing or eliminating interference in radio receivers due to unwanted signals. Even more specifically, this invention relates to a cancellation system and method for situations where the direction of arrival of the signal of interest is known, but the direction of arrival of an interfering signal is arbitrary.
Description of the Prior Art
Fig. 1 is a functional diagram of a conventional interference cancellation system connected to a radio receiver system, shown generally as including a receiver antenna 2, a receiver 4 and a transmission line 6 interconnecting the receiver antenna 2 and the receiver 4. The interference cancellation system includes an auxiliary antenna 8, the purpose of which is to receive an RF sample of an interfering signal and to provide a reference signal for the interference cancellation system.
This reference signal is used to detect the presence, amplitude and phase of the same interfering signal in the transmission line 6 between the receiver antenna 2 and the receiver 4, in the following manner.
A first coupler 10 is electronically connected to the auxiliary antenna transmission line 12 to provide a portion of the reference signal corresponding to the interfering signal received by the auxiliary antenna 8 to one input of a synchronous detector 14. A sample of the signal received on the receiver transmission line 6 is provided to a second input of the synchronous detector 14 by using a second coupler 16 connected to the receiver transmission line 6. The synchronous detector 14 thus compares a portion of the reference signal and the sample signal from the receiver transmission line 6, and provides output signals which vary in accordance with the differences and similarities in phase and amplitude of the reference and sample signals.
The output signals of the synchronous detector 14 are modified by respective integrators/amplifiers 18 to provide control signals which are provided to a signal controller 20.
The reference signal is also provided, through an appropriate amplifier 22, to the signal controller 20. The signal controller 20 and the synchronous detector 14 thus define an adaptive control loop in the interference cancellation system such that the signal controller 20, driven by the control signals, adjusts the amplitude and phase of the reference signal and provides an adjusted cancellation signal. The cancellation signal is then injected into the receiver signal path defined by the receiver antenna 2, transmission line 6 and receiver 4 with equal amplitude but in a phase which is opposite to that of the interference signal, thereby cancelling the interfering signal in the receiver path. A third coupler, which is referred to as a subtractor 24 in Fig. 1, is used to inject the cancellation signal into the receiver signal path.
The interference cancellation system automatically and continuously maintains the amplitude and phase of the cancellation signal for maximum cancellation.
When the direction of the desired signal is fixed, a directive antenna may be used for the receiver antenna. If the direction of the interference signal is arbitrary, then an omni-directional antenna is generally used for the auxiliary antenna 8.
In a conventional interference cancellation system, such as the type described above and illustrated by Fig. 1 of the drawings, the strongest signal received at the auxiliary antenna 8, be it the desired signal or the interfering signal, is cancelled since it dominates and controls the outputs of the synchronous detector 14. When the interfering signal arrives in the same direction as the signal of interest, both the interfering signal as well as the desired signal are cancelled.
When only the desired signal is present, or when the desired signal is stronger than the interfering signal, the conventional interference cancellation system must be disabled in order to prevent cancellation of the desired signal.
Another disadvantage of the conventional cancellation interference system is that the auxiliary antenna 8 and the receiver antenna 2 must be spaced apart from one another so that there is a phase difference between the reference signal from the auxiliary antenna and the sample signal taken from the receiver antenna. This phase difference is necessary so that the adaptive control loop of the cancellation system, and in the particular the synchronous detector 14 of the loop, can distinguish between the two signals and provide a proper detector output signal to the signal controller 20.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an interference cancellation system and method which will minimize the possibility of cancelling a desired signal received by a radio receiver system to which the interference cancellation system is connected when no interference is present.
It is another object of the present invention to provide an interference cancellation system which is automatically disabled for signals received in the direction of the signal of interest.
It is yet a further object of the present invention to provide an interference cancellation system which overcomes the inherent disadvantages of conventional interference cancellation systems.
In one form of the present invention, an interference cancellation system for connection to a radio receiver system having a receiver antenna, a receiver portion and a receiver transmission line inter injecting the receiver antenna with the receiver, includes an auxiliary antenna for receiving an interfering signal, the auxiliary antenna providing a reference signal corresponding to the interfering signal received by the auxiliary antenna. A first directional coupler is electrically coupled to the auxiliary antenna. The reference signal is provided to the first directional coupler, and the first directional coupler has an output and provides a first output signal which is proportional to the reference signal.
The interference cancellation system further includes a second directional coupler, the second directional coupler being electrically coupled to the receiver transmission line.
The second directional coupler has an output and provides on the output a sample signal corresponding to the interfering and desired signals received by the receiver antenna.
A synchronous detector is further included in the interference cancellation system. The synchronous detector has at least two inputs which are respectively electrically coupled to the first and second directional couplers so that the synchronous detector is provided with the first coupler output signal and the sample signal. The synchronous detector compares the first coupler output signal and the sample signal and provides at least one detector output signal.
The interference cancellation system further includes a signal controller. The signal controller has a first input which is electrically coupled to a second output of the first coupler so that the signal controller is provided with a signal which is proportional to the reference signal, and at least a second input which is electrically coupled to the synchronous detector and which is provided with the detector output signal.
The synchronous controller has an output on which is provided a cancellation signal.
The interference cancellation system further includes a subtractor. The subtractor is coupled to the receiver transmission line and is further electrically coupled to the signal controller. The subtractor has an input on which is provided the cancellation signal. The subtractor effectively injects the cancellation signal onto the receiver transmission line carrying the received signals and into the receiver signal path defined by the receiver antenna, transmission line and receiver. The cancellation signal injected into the receiver signal path is equal to and opposite in phase to the interfering signal carried by the receiver transmission line so as to cancel the received interfering signal.
The interference cancellation system may include an amplifier interposed between the second output of the first coupler and the signal controller's first input, and an integrator/amplifier interposed between the detector and the signal controller to integrate and amplify the detector output signal and to provide a control signal to the signal controller.
In accordance with one form of the present invention, the gain of the interference cancellation system, from the auxiliary antenna to the subtractor, must be less than the gain of the receiver antenna. If this holds true, then the interference cancellation system will have insufficient gain to cancel any signal within some angle of the receiver antenna boresight. The strongest signal outside of this angle is cancelled (or at least reduced). The receiver antenna is pointed in a manner such that the desired signal arrives within a predetermined angle of the boresight, that is, where the receiver antenna has the most gain. With this arrangement, the interference cancellation system of the present invention need not be turned off when the interfering signal is absent.
Furthermore, unlike conventional interference cancellation systems, the auxiliary antenna of the present invention need not be mounted in a spaced apart relationship with the receiver antenna. As long as the gain of the interference cancellation system from the auxiliary antenna to the subtractor is less than the gain of the receiver antenna, the two antennas may be mounted coaxially without the desired signal being cancelled. In such a configuration, where the two antennas may be mounted coaxially, the auxiliary antenna may be an omni-directional antenna, and the receiver antenna is directional.
In an alternative form of the present invention, the interference cancellation system may employ an auxiliary antenna providing a null in its gain, for example, a loop antenna or one which provides a cardioid antenna pattern. The auxiliary antenna would be mounted coaxially with the receiver antenna, which receiver antenna would be of the directive type.
The null of the auxiliary antenna would be aligned with the boresight of the receiver antenna and directed toward the desired signal. Accordingly, the interference cancellation system would have sufficient gain from the auxiliary antenna through the subtractor which is greater than that of the receiver antenna outside of a predetermined angle with respect to the boresight of the receiver antenna to cancel any interfering signals received from directions outside of this predetermined angle. However, due to the null in the antenna pattern of the auxiliary antenna, the interference cancellation system of the present invention would have insufficient gain within the predetermined angle of the boresight of the receiver antenna so as not to cancel the desired signal received within that predetermined angle.
In either configuration described above, the interference cancellation system will not cancel a desired signal when only the desired signal is present.
These and other objects, features and advantages of this invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a functional diagram of a conventional interference cancellation system.
Fig. 2 is a functional diagram of the interference cancellation system of the present invention.
Fig. 3 is an alternative form of the interference cancellation system of the present invention.
Fig. 4 is a pictorial illustration of superimposed antenna patterns for the auxiliary antenna and the receiver antenna.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 2 illustrates functionally one form of the interference cancellation system of the present invention.
The interference cancellation system is adapted to be connected to a radio receiver system having a receiver antenna 30, a receiver 32, and a receiver transmission line 34 connecting the receiver antenna 30 with the receiver 32. The receiver antenna 30 receives an interferring signal and a desired signal, as sometimes may occur when a receiver and a transmitter are collocated, which signals are provided to the receiver 32 by the transmission line 34.
The interference cancellation system includes an auxiliary antenna 36 for receiving an interfering signal. The auxiliary antenna 36 is connected to a first directional coupler 38 by a transmission line 40, and provides to the first directional coupler 38 a reference signal which corresponds to the interfering signal received by the auxiliary antenna 36.
One output of the first directional coupler 38 is connected to an input of a synchronous detector 42. The other output of the first directional coupler 38 is provided to an amplifier 44, whose output is connected to the input of a signal controller 46. The first directional coupler 38 thus provides a portion of the reference signal to the synchronous detector 42, as well as to the signal controller 46 through the amplifier 44.
The interference cancellation system further includes a second directional coupler 48. The second directional coupler 48 is electrically coupled to the receiver transmission line 34, and has an output on which is provided a sample signal corresponding to the signals received by the receiver antenna 30. As mentioned previously, the interference cancellation system includes a synchronous detector 42. The synchronous detector 42 has at least two input ports (i.e., a reference port and an error port) which are respectively electrically coupled to the outputs of the amplifier 44 and the second directional coupler 48 so that the reference signal and the sample signal are provided to the two input ports of the synchronous detector.
The synchronous detector 42 is basically a quadrature phase detector. A typical synchronous detector which is suitable for use is described in U.S. Patent No. 3,999,444 which issued to Rabindra Ghose and Walter Sauter, the disclosure of which is incorporated herein by reference. The synchronous detector 42 compares the reference signal and the sample signal and provides one or more detector output signals.
The synchronous detector 42 may be regarded as a switch controlled by zero-crossing of the reference port signal of such a detector. Because the synchronous detector is referenced to the interference signal ti.e., the reference signal), a non-zero sample signal will cause the synchronous detector 42 to output a DC detector output signal. An amplifier and/or an integrator 50 may be included in the interference cancellation system and connected to the synchronous detector's output so that the DC output signals of the detector will be amplified and integrated to create control signals, which signals are provided to the signal controller 46 of the interference cancellation system.
A signal controller 46 suitable for use in the interference cancellation system of the present invention is described in U.S. Patent No. 3,699,444, mentioned previously.
In its simplest form, the signal controller consists of an inphase and a quadrature-phase electronic attenuator, each being controllable by a respective DC control signal. One of its inputs is provided with a portion of the reference signal from the output of the first directional coupler 38. Another input of the signal controller receives the control signals from the amplifiers/integrators 50. An output of the signal controller is provided to a subtractor 52, or 180 hybrid, which subtractor is coupled to the receiver transmission line 34.
The signal controller 46 provides a cancellation signal to the subtractor 52 which, in effect, injects the cancellation signal into the receiver signal path defined by the receiver antenna 30, transmission line 34 and receiver 32 and, more specifically, onto the receiver -transmission line carrying the desired and interfering signals.
Because the synchronous detector 42 is referenced to the interfering signal to be eliminated, the non-zero sample signal will result in DC signals at the outputs of the synchronous detector. The DC signals are amplified and integrated to create control signals for the signal controller 46 such that the values of gain and phase of the cancellation signal which is generated by the signal controller 46 change only when the sample signal is present. As the non-zero sample signal causes the control signals to change, the values of gain and phase of the cancellation signal change until such values become what are exactly required to drive the sample signal to zero.The cancellation signal which is injected into the receiver transmission line 34 is equal to and opposite in phase to the interfering signal received by the receiver antenna 30 and carried by the receiver transmission line 34 so as to cancel the received interfering signal.
In conventional interference cancellation systems, such as that shown in Fig. 1 of the drawings, the strongest signal received at the auxiliary antenna is cancelled since it dominates the outputs of the synchronous detector. When the interfering signal arrives in the same direction as the desired signal, both the interfering signal as well as the desired signal are cancelled. When only the desired signal is present, or when the desired signal is stronger than the interfering signal, a conventional interference cancellation system must be disabled in order to prevent cancellation of the desired signal.
The interference cancellation system of the present invention minimizes the possibility of cancellation of the desired signal. As illustrated by Fig. 2, the gain in the auxiliary or the signal controller path, which is defined by the auxiliary antenna 36, amplifier 44, signal controller 46 and subtractor 52, is insufficient to cancel any signal within some angle of the receiver antenna boresight. However, the strongest signal outside of this angle is cancelled or at least reduced.
More specifically, and again referring to the embodiment shown in Fig. 2 of the drawings, the auxiliary antenna 36 is an omni-directional antenna, such as a dipole. Accordingly, the input will have a fixed gain in any direction and thus receive an interfering signal from any direction. The receiver antenna 30, on the other hand, is of the directive type, such as a parabolic antenna. Accordingly, it has relatively significant gain within a predetermined angle about its boresight.
The receiver antenna 30 is pointed in a manner such that the desired signal arrives within the predetermined angle. If the gain of the interference cancellation system from the auxiliary antenna 36 to the subtractor 52 is less than the gain of the receiver antenna 30 within the predetermined angle of boresight, then the desired signal will not be cancelled.
However, all interfering signals from directions outside of the predetermined angle will be cancelled or reduced, as the gain of the interference cancellation system and in particular the auxiliary or signal controller path of the system will exceed the gain of the receiver antenna 30 outside of the predetermined angle of boresight.
For example, assume that the gain of the receiver antenna 30 is +10 dB within the predetermined angle of boresight, and the gain of the omni-directional auxiliary antenna 36 is zero dB. The total gain of the auxiliary or signal controller path is limited to +5 dB maximum. Any signal arriving within the 5 dB beamwidth of the receiver antenna 30 is not cancelled since there is insufficient signal amplitude in the auxiliary path for cancellation. This is irrespective of whether there are any signals outside of the 5 dB beamwidth. For signals arriving outside of this beamwidth, this limitation does not apply. Accordingly, when only the desired signal is present (and is received within the predetermined angle of boresight of the receiver antenna 30), it is not cancelled.
Fig. 3 illustrates an alternative form of the interference cancellation system of the present invention. All of the components of this alternative embodiment, except for the auxiliary antenna 36, are the same as those components used in the interference cancellation system described previously with respect to Fig. 2. However, in this embodiment, an auxiliary antenna 36a is chosen, not to be omni-directional, but rather to exhibit a null in a fairly narrow direction. An example of such an antenna is a loop antenna (which has nulls in its antenna pattern which are diametrically opposite one another) or an antenna having a cardioid pattern (see Fig. 4).
The auxiliary antenna 36a is positioned such that the null in its antenna pattern is pointed in the direction of the desired signal, which is also the direction in which the receiver antenna 30 is directed, so that the centerline of the null of the auxiliary antenna 36a is substantially parallel to the boresight of the receiver antenna. Thus, the gain of the auxiliary antenna 36a and, consequently, of the auxiliary signal path from the auxiliary antenna 36a to the subtractor 52, automatically falls off within a predetermined angle of the boresight of the receiver antenna 30 such that no cancellation occurs within this predetermined angle.
Using an auxiliary antenna 36a exhibiting a null in its antenna path allows a much higher gain G to be used in the auxiliary path, i.e., from the auxiliary antenna 36a to the subtractor 52. The auxiliary path gain of the interference cancellation system may, in effect, be greater than that of the receiver antenna 30, as long as the auxiliary antenna 36a is directed with its null towards the desired signal, and the receiver antenna is directed in the same manner, and as long as the gain of the auxiliary path at the null is maintained at a level which is less than the gain of the receiver antenna within a predetermined angle of the receiver antenna boresight.
Fig. 4 illustrates a cardioid antenna pattern 54 of the auxiliary antenna superimposed on the antenna pattern 56 of the receiver antenna which is of the directive type, such as a parabolic antenna. The null 58 of the auxiliary antenna pattern 54 is pointed in the direction of the desired signal, as is the boresight of the receiver antenna. It can be seen from Fig. 4 that the angle over which a signal is not cancelled depends on the maximum gain G in the auxiliary path of the interference cancellation system. The angle over which cancellation does not occur decreases as the maximum gain is increased.
In a preferred form of the interference cancellation system of the present invention, the auxiliary antenna 36 and the receiver antenna 30 are not spaced apart but rather are coaxially mounted together. If the auxiliary antenna 36 is an omni-directional antenna, the auxiliary gain of the interference cancellation system from the auxiliary antenna 36 to the subtractor 52 is less than the gain of the receiver antenna 30 within a predetermined angle of the receiver antenna boresight. If the auxiliary antenna 36a is a loop antenna or one that exhibits a cardioid antenna pattern or, more generally, one that exhibits a null, then the null of the auxiliary antenna is directed toward the desired signal, as is the receiver antenna 30. In either case, the auxiliary antenna and receiver antenna may be coaxially mounted.
It can be seen from the above description that the interference cancellation system of the present invention is adapted to cancel interfering signals having an arbitrary and unknow duration and direction. The desired signal is not cancelled. The interference cancellation system of the present invention need not be disabled when only the desired signal is present, as in conventional systems. Furthermore, the auxiliary antenna and the receiver antenna need not be spaced apart but rather may be coaxially mounted.
Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention.
Claims (6)
1. An interference cancellation system for connection to a radio receiver system having a receiver antenna, a receiver portion and a receiver transmission line electrically coupling the receiver antenna to the receiver, the interference cancellation system comprising:
an auxiliary antenna for receiving an interfering signal, the auxiliary antenna providing a reference signal corresponding to the interfering signal received by the auxiliary antenna;
a first directional coupler, the reference signal being provided to the first directional coupler, the first directional coupler having first and second outputs and respectively providing thereon first and second output signals each corresponding to the reference signal;;
a second directional coupler, the second directional coupler being electrically coupled to the receiver transmission line, the second directional coupler having an output and providing thereon a sample signal corresponding to an interfering signal and desired signal received by the receiver antenna;
a synchronous detector, the synchronous detector having at least two inputs respectively electrically coupled to the first and second directional couplers and being responsive to the second output signal of the first coupler and the sample signal of the second coupler, the synchronous detector comparing the first coupler second output signal and the sample signal and providing at least one detector output signal in response thereto;;
a signal controller, the signal controller having a first input electrically coupled to the first directional coupler and being responsive to the first output signal of the first coupler, and at least a second input electrically coupled to the synchronous detector, the signal controller having an output and providing thereon a cancellation signal in response to the detector output signal; and
a subtractor, the subtractor being electrically coupled to the receiver transmission line and being further electrically coupled to the signal controller, the subtractor having an input on which is provided the cancellation signal, the subtractor effectively injecting the cancellation signal onto the receiver transmission line carrying the received interfering and desired signals, the cancellation signal injected into the receiver transmission line being equal to and opposite in phase to the interfering signal received by the receiver antenna and carried by the receiver transmission line so as to cancel the interfering signal on the receiver line;
the auxiliary antenna being qn omni-directional antenna, and the receiver antenna being a directive antenna;;
the gain of the interference cancellation system from the auxiliary antenna to the subtractor being less than the gain of the receiver antenna within a predetermined angle of the receiver antenna boresight.
2. An interference cancellation system for connection to a radio receiver system having a receiver antenna, a receiver portion and a receiver transmission line electrically coupling the receiver antenna to the receiver, the interference cancellation system comprising:
an auxiliary antenna for receiving an interfering signal, the auxiliary antenna providing a reference signal corresponding to the interfering signal received by the auxiliary antenna;
a first directional coupler, the reference signal being provided to the first directional coupler, the first directional coupler having first and second outputs and respectively providing thereon first and second output signals each corresponding to the reference signal;;
a second directional coupler, the second directional coupler being electrically coupled to the receiver transmission line, the second directional coupler having an output and providing thereon a sample signal corresponding to an interfering signal and desired signal received by the receiver antenna::
a synchronous detector, the synchronous detector having at least two inputs respectively electrically coupled to the first and second directional couplers and being responsive to the second output signal of the first coupler and the sample signal of the second coupler, the synchronous detector comparing the first coupler second output signal and the sample signal and providing at least one detector output signal in response thereto;
a signal controller, the signal controller having a first input electrically coupled to the first directional coupler and being responsive to the first output signal of the first coupler, and at least a second input electrically coupled to the synchronous detector, the signal controller having an output and providing thereon a cancellation signal in response to the detector output signal; and
a subtractor, the subtractor being electrically coupled to the receiver transmission line and being further electrically coupled to the signal controller, the subtractor having an input on which is provided the cancellation signal, the subtractor effectively injecting the cancellation signal onto the receiver transmission line carrying the received interfering and desired signals, the cancellation signal injected into the receiver transmission line being equal to and opposite in phase to the interfering signal received by the receiver antenna and carried by the receiver transmission line so as to cancel the interfering signal on the receiver line;
the auxiliary antenna exhibiting an antenna pattern having null, and the receiver antenna being a directive antenna;;
the auxiliary antenna being positioned such that the null of its antenna pattern is parallel with the boresight of the receiver antenna and such that the null of the auxiliary antenna and boresight of the receiver antenna are directed to the desired signal source.
3. An interference cancellation system as defined by claim 1, wherein the auxiliary antenna and the receiver antenna are coaxially mounted.
4. An interference cancellation system as defined by claim 2, wherein the auxiliary antenna and the receiver antenna are coaxially mounted.
5. A method for substantially preventing an interference cancellation system from cancelling a desired signal received by a radio receiver system to which the interference cancellation system is connected, the radio receiver system including a receiver antenna, a receiver and a receiver transmission line interconnecting the receiver antenna and the receiver, the interference cancellation system including an auxiliary antenna, a first directional coupler electrically coupled to the auxiliary antenna, a second directional coupler electrically coupled to the receiver transmission line, a synchronous detector electrically coupled to the first and second directional couplers, a signal controller electrically coupled to the first directional coupler and to the synchronous detector, and a subtractor electrically coupled to the signal controller and to the receiver transmission line and provided to inject a cancellation signal into the receiver transmission line, the auxiliary antenna being an omni-directional antenna and the receiver antenna being a directive antenna, the method comprising the step of:
maintaining the gain of the interference cancellation system from the auxiliary antenna to the subtractor at a level which is less than the gain of the receiver antenna within a predetermined angle of the receiver antenna boresight.
6. A method for substantially preventing an interference cancellation system from cancelling a desired signal received by a radio receiver system to which the interference cancellation system is connected, the radio receiver system including a receiver antenna, a receiver and a receiver transmission line interconnecting the receiver antenna and the receiver, the interference cancellation system including an auxiliary antenna, a first directional coupler electrically coupled to the auxiliary antenna, a second directional coupler electrically coupled to the receiver transmission line, a synchronous detector electrically coupled to the first and second directional couplers1 a signal controller electrically coupled to the first directional coupler and the synchronous detector, and a subtractor electrically coupled to the signal controller and to the receiver transmission line and provided to inject a cancellation signal into the receiver transmission line, the auxiliary antenna exhibiting an antenna pattern having a null, and the receiver antenna being a directive antenna, the method comprising the steps of:
positioning the auxiliary antenna such that the null of the auxiliary antenna pattern is directed towards the desired signal, the receiver antenna being positioned such that its boresight is directed toward the desired signal; and
maintaining the gain of the interference cancellation system from the auxiliary antenna to the subtractor at the null at a level which is less than the gain of the receiver antenna within a predetermined angle of the receiver antenna boresight.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US45890189A | 1989-12-29 | 1989-12-29 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9027438D0 GB9027438D0 (en) | 1991-02-06 |
| GB2240695A true GB2240695A (en) | 1991-08-07 |
| GB2240695B GB2240695B (en) | 1994-06-08 |
Family
ID=23822549
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9027438A Expired - Fee Related GB2240695B (en) | 1989-12-29 | 1990-12-18 | Interference cancellation system for interference signals having an arbitrary and unknown duration and direction |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2032647C (en) |
| GB (1) | GB2240695B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014125491A1 (en) * | 2013-02-14 | 2014-08-21 | Ubiqam Ltd. | Methods and systems for processing received signals for a wireless network receiver |
| US9178600B2 (en) | 2002-09-28 | 2015-11-03 | Koninklijke Philips N.V. | Packet data transmission in a mimo system |
| GB2571709A (en) * | 2018-02-28 | 2019-09-11 | Cambium Networks Ltd | Communication apparatus and method |
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| US3699444A (en) * | 1969-02-17 | 1972-10-17 | American Nucleonics Corp | Interference cancellation system |
| US3947848A (en) * | 1962-08-07 | 1976-03-30 | The United States Of America As Represented By The Secretary Of The Navy | Anti-jam dual channel video cancellation circuit for first target tracking system |
| US4010469A (en) * | 1951-06-20 | 1977-03-01 | The Rand Corporation | Interference suppression |
| US4044359A (en) * | 1962-01-09 | 1977-08-23 | General Electric Company | Multiple intermediate frequency side-lobe canceller |
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1990
- 1990-12-18 GB GB9027438A patent/GB2240695B/en not_active Expired - Fee Related
- 1990-12-19 CA CA 2032647 patent/CA2032647C/en not_active Expired - Fee Related
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4010469A (en) * | 1951-06-20 | 1977-03-01 | The Rand Corporation | Interference suppression |
| US4044359A (en) * | 1962-01-09 | 1977-08-23 | General Electric Company | Multiple intermediate frequency side-lobe canceller |
| US3947848A (en) * | 1962-08-07 | 1976-03-30 | The United States Of America As Represented By The Secretary Of The Navy | Anti-jam dual channel video cancellation circuit for first target tracking system |
| US3699444A (en) * | 1969-02-17 | 1972-10-17 | American Nucleonics Corp | Interference cancellation system |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9178600B2 (en) | 2002-09-28 | 2015-11-03 | Koninklijke Philips N.V. | Packet data transmission in a mimo system |
| US10645709B2 (en) | 2002-09-28 | 2020-05-05 | Koninklijke Philips N.V. | Packet data transmission in a MIMO system |
| WO2014125491A1 (en) * | 2013-02-14 | 2014-08-21 | Ubiqam Ltd. | Methods and systems for processing received signals for a wireless network receiver |
| US9496904B2 (en) | 2013-02-14 | 2016-11-15 | Ubiqam Ltd. | Methods and systems for processing received signals for a wireless network receiver |
| US9887717B2 (en) | 2013-02-14 | 2018-02-06 | Ubiqam Ltd. | Methods and systems for processing received signals for a wireless network receiver |
| GB2571709A (en) * | 2018-02-28 | 2019-09-11 | Cambium Networks Ltd | Communication apparatus and method |
| GB2571709B (en) * | 2018-02-28 | 2020-09-09 | Cambium Networks Ltd | Interference mitigation apparatus and method for a wireless terminal |
| US11303044B2 (en) | 2018-02-28 | 2022-04-12 | Cambium Networks Ltd | Interference mitigation apparatus and method for a wireless terminal |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2240695B (en) | 1994-06-08 |
| GB9027438D0 (en) | 1991-02-06 |
| CA2032647A1 (en) | 1991-06-30 |
| CA2032647C (en) | 2000-03-21 |
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| Date | Code | Title | Description |
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| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20031218 |