FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
WIDEBAND PHASED ARRAY SYSTEM WITH PROGRAMMABLE NULL POSITIONING CAPABILITY
TATA CONSULTANCY SERVICES LTD.,
an Indian Company of Nirmal Building, 9th Floor,
Nariman Point, Mumbai -21,
Maharashtra, India.
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION
The present invention relates to the field of telecommunications.
DEFINITIONS OF TERMS USED IN THE SPECIFICATION
The term 'Phased array' in this specification relates to a group of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.
The term 'Wideband' in this specification is a relative term used to describe a wide range of frequencies in a spectrum.
The term 'Switched beam' in this specification relates to several available fixed beam patterns. In these systems, decision can be made as to which beam to access at any given point in time, based upon the requirements of the system.
The term 'Steerable' in this specification relates to electronically directing a beam to transmit or receive it in a particular direction.
The term 'Jam signal' in this specification relates to signals that carry binary pattern sent by a data station to inform the other stations that they must not transmit.
The term 'Interference' in this specification relates to signals which alter, modify, or disrupt the wideband phased array signal as it travels along a

channel. The term typically refers to the addition of unwanted signals to the wideband phased array signal.
The term 'Null placement' in this specification relates to a given element spacing. The phase shift chosen between any two elements to give a perfect cancellation in any desired direction is "null placement".
The term 'Nulls' in this specification relates to directions in which there is no radiation. Nulls consist of lines or points on a far-field sphere.
The term 'Main Lobe' in this specification relates to a main lobe, or main beam, of an antenna radiation pattern that contains the maximum power.
The term 'Side lobe' in this specification relates to the lobes of the far field radiation pattern that are not the main lobe.
The term 'Grating Lobe' in this specification relates to phased arrays in which the element spacing is much greater than a half wavelength, the aliasing effect causes some side lobes to become substantially larger in amplitude and approach the level of the main lobe these are called grating lobes.
The term 'phase shifter' in this specification relates to an element of the phased array system which provides a controllable change in the transmission phase angle of a beam/signal.

The term 'True Time Delay' in this specification relates to an element used to improve the bandwidth of the phased array system.
The term 'combiner' in this specification relates to a passive electronic element of the phased array system that linearly merges/mixes two or more signal sources.
The term 'splitter' in this specification relates to a passive electronic element of the phased array system that directs a signal from one source to two or more sources.
BACKGROUND OF THE INVENTION
One of the major concerns for antenna or radar engineers is reception of desired signal in the presence of interference. Interference degrades reception quality by penetrating from the sidelobe region of the antenna pattern. Various works in last two decades are related to the topics of pattern nulling, adaptive nulling and the like. Among these, side lobe suppression (nulling) is proposed using different methods like phase control, amplitude control or by complex weight control. But these methods mostly rely on complex algorithms and computations. Hence, the practical realizations demand constant update of phase, amplitude or in both of excitation coefficient fed to each radiating elements.
Typically, an electronically steered phased array antenna system can be setup with phase shifters connected to each radiating element which in combine transmit (receive) in a directive way. By selecting appropriate

phase gradient between successive.radiating elements, it becomes possible to steer the beam away from the boresight (that is normal to the plane of the radiating elements). Typically, most applications use a complex weight for each element, where the relative amplitude and phase gradient between successive elements determine the beam tilt from boresight and the sidelobe level. But phased array systems display a problem of undesired beam squint for wideband applications. Moreover, the quality of beam shape and angular accuracy worsen with the increase of signal bandwidth, size of aperture and steering angle. This is because phase shifters introduce nearly identical phase shift for other frequency of operation also, whereas the requirement is that of having a relative phase shift value proportional to the change in frequency.
The problem can be overcome by the use of true time delays instead of phase shifters. Moreover, in the rapidly evolving wireless communication systems there is a growing need for implementing a phased array system which is capable of adjusting beam tilt angle, pattern shape and interference suppression preferably over. multiple contiguous frequency band of operations, at low cost overheads.
The currently available wideband, fully steerable array using digitally controlled programmable time-delay units with additional facility of precise null-suppression is prohibitively costly. To overcome this problem, a subarray based feeding mechanism can be implemented where both phase shifters and time-delays can be incorporated. Subarray feeding can typically be conventional or overlapping. Typically, to get the benefits of this system

architecture having phase shifters in the main array can be combined by Butler matrix and time delays in the subarray can be combined by corporate feed. Also, the concept of complex weight optimization for adaptive interference suppression can be utilized by this architecture. Using adaptive sidelobe cancellers or by optimizing the complex weight coefficients it is possible to place one or multiple nulls in the presence of strong interference. These methods though popular for null formation, are costly as they require extra hardware and computational resources. Typical solution in this regard, is to control the signal characteristics at the sub-array level. Often a large sub-array can be divided into few sub arrays where time delays are used at sub array level and phase shifters are used at antenna levels. Particularly, Haupt R.L elaborates a sub-array null formation technique which optimizes complex weights in the sub-array level. Controlling the undesirable grating lobe in beam shaping and in null placements is one of the major challenges in sub-array scheme.
This is solved by using partially overlapped sub array technique where the overlap extent will be optimized. Setting up an electronically steer able phased array system which can be simultaneously wideband, programmable, low complexity requiring minimum additional hardware's like power combiners and splitters, minimum computational efforts for suppressing deterministic interference (where the angle of arrival of jamming signal is known) is a major challenge.
There were various attempts in the prior art to overcome these drawbacks:

Particularly, US Patent 5414433 discloses a phased array radar antenna with two-stage time delay units. The disclosure contains a phased array antenna with multiple antenna radiating elements for providing a directed beam of electromagnetic energy. The radiating elements are arranged in groups to form multiple time steered subarrays. However, the disclosure lacks in the resolution of null forming capability due to the time delay control at two stages.
Further, US Patent 4544927 discloses a Wideband beamformer that discloses a wideband performance due to a combination of phase shift and time-delay beam forming without considering any null-forming capability. The disclosure generates a sector beam to scan in parallel in scan-space. However, the disclosure lacks the capability to steer the beam formation using time-delay units and does not have a null-imposing capability towards the interference direction.
There is therefore felt a need for a system which has the capability to generate the beam pattern and steer the beam in the desired direction. In addition, there is felt a need for a system which can automatically impose null in the location of interference without the use of complex techniques and expensive equipment.

OBJECT OF THE INVENTION
It is an object of the present invention to provide a phased array system which has the capacity to electronically steer the beam of the radiating elements using minimum hardware.
It is another object of the present invention to provide antenna element sharing method, by fixed overlapped sub-array architecture, that offers simple null steering capability while eliminating the need for intensive computation of complex weight vectors attached to each antenna element.
It is yet another objective of the invention to provide a phased array system that consists of sub array combination that will not introduce either grating lobes or require an optimization of illumination function to eliminate grating lobe.
It is still another object of the present invention to provide a phased array system that removes the restriction of using multiple types of feed network design for the cases where the same wireless service is allotted to different spectrums in different regions of operation within a broad frequency band allocation.
SUMMARY OF THE INVENTION
The present invention envisages a programmable wideband phased array system. Trie phased array system comprises:

• a main linear array of M radiating elements where the distance d between each of said radiating elements is less than one wavelength (λ) of the operating frequency, where M and d are positive integer;
• time-delay units discretely connected to each of the radiating elements to form a sum pattern signal to enable wideband and steerable operation of the phased array;
• a splitter element coupled to the time-delay unit to receive the sum pattern signal, the splitter element adapted to form two discrete sets of sub-arrays, each set containing (M-1) elements, where at least one element of one set overlaps a corresponding element of the other set;
• phase-shifters connected discretely to each of said sets of sub-arrays adapted to receive the sum pattern signal and further adapted to detect an external. interference signal and form a difference pattern signal, said difference pattern signal is a function of cosine of the detected angle of interference to position a programmable null signal at the location of the external interference signal impinging on said phased array system;
• a combiner element coupled to the phase shifters to combine the output signals of the phase shifters to form a combined difference pattern; and
• transmitter and receiver element to transmit the combined output signal and/or receive external signals.

In accordance with the present invention, the inter-element spacing between the radiating elements is λ/2.
Typically, each of the sets of sub-arrays consists of (M-2) overlapping elements and the overlapped sets of sub array contain one of either the first or the Mth radiating elements.
Preferably, the time-delay unit is a time-delay based Programmable Switching Matrix, said Programmable Switching Matrix having:
• two levels of programmable delay lines connected with a plurality of dual-pole three-throw RF switches;
• unit delays and PIN diodes provided between the two poles of the switches; and
• coaxial cable transmission lines for the interconnection of delay lines with the switches,, unit delays and PIN diodes and for wideband operations of the phased array system.
Typically, the unit delays are assigned pre-determined delay values.
In accordance with the present invention, the phase shifters include a digital variable phase shifter which can be connected to either or both of the sub-arrays.
Typically, the phased array system includes a microcontroller to control the operations of the time-delay unit and the phase shifters.

In accordance with the present invention, there is provided a method for pattern generation, steering operation of a wideband phased array system and positioning a programmable null at the location of external interference, the method comprises the following steps:
• using the radiating elements of the phased array system to generate a beam;
• steering the beam in the desired direction using a sum pattern generated by using true time based delays;
• transmitting the steered wideband signal;
• sensing the arrival of an external interference signal and the angle/location of interference using well known methods; and
• shifting the phase and generating a difference signal which is a function of cosine of the detected angle of interference for nullifying the effect of the interference.
Typically, the step of providing a true time-delay includes the steps of:
a. connecting a two layer time-delay based Programmable Switched
Matrix to each of the radiating elements with a dual-pole three-
throw RF switch;
b. providing fast responding PIN diodes and unit delays having a pre
determined value between the two poles of the switch; and
c. interconnecting the aforesaid elements with a coaxial transmission
line.

Typically, the step of generating a sum pattern signal includes the steps of selecting any one of the three alternative paths provided by the dual-pole three-throw RF switches each path having a pre-determined value of time-delay settings as assigned to the unit delay element of the programmable switched matrix.
Typically, the step of generating a difference pattern signal includes the step of detecting the angle/location at which the interference signal is impinging on the system, shifting the phase with a value that is a function of cosine of the detected angle of interference, generating a difference pattern (null signal) and placing the null signal at that location.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Other aspects of the invention will become apparent by consideration of the accompanying drawings and their description stated below, which is merely illustrative of a preferred embodiment of the invention and does not limit in any way the nature and scope of the invention.
FIGURE 1 illustrates a schematic of the system for pattern generation and interference cancellation, in accordance with the present invention;
FIGURE 2 illustrates a sum pattern generation and steering network at antenna level for each sub array, in accordance with the present invention; and
FIGURES 3 to 12 illustrate quiescent patterns and sidelobe suppression, in accordance with the present invention.

DETAILED DESCRIPTION
The present invention envisages a wideband phased array system which enables wideband beam pattern generation and steerable operation of the phased array of the radiating elements along with the capability of positioning programmable null in the direction of the interference signal. In addition, the system gives the phased array the ability to scan over a set of fixed spatial angles.
In accordance with one aspect of the present invention, the phased array system achieves the aforementioned functionalities by employing two stages, the first stage consisting of a true time delay based time-delay unit which is connected to each of the radiating elements of the linear phased array and the second stage consisting of digital variable phase shifters at the sub-array level, each sub-array consists of (M-l) elements, where Mis a positive integer representing the number of radiating elements in the phased array.
In accordance with another aspect of the present invention, the sub-array is an overlapped array formed by overlapping the radiating elements of the main linear phased array. The overlapped sub-arrays consist of (M-2) elements. The overlapped sub-arrays improve the side lobe level of the wideband beam and allow the center at the sub array level to be less than one

wavelength (λ) thereby ensuring that grating lobe is not observed. In addition, the overlapping offers simple null steering capability while eliminating the need for intensive computation of complex weight vectors attached to each radiating elements.
In accordance with yet another aspect of the present invention, the architecture of combining a linear array of radiating elements, where each radiating element has a digitally selectable true time-delay weight facilitates wideband, fixed angle electronic beam switching with pattern control mechanism for wireless base-stations.
Referring to the accompanying drawings, a linear array of M numbers of radiating elements, represented by reference numeral 100 are divided into two sub arrays each consisting of (M-l) elements as shown in FIGURE 1 of the accompanying drawings. The two horizontal sub arrays overlap each to the extent of (M-2) elements. Thus, the element locations that are grouped in only any one of the two sub arrays are the first element and the Mth element. The fixed overlap architecture always ensures that the problem of grating lobe is eliminated while considering the inter-element spacing'd' to be less than free space wavelength (λ) or guide wavelength.
The phased array system comprises of two stages namely a time-delay unit 102 for applying a time-delay based phase gradient at radiating elements level 100 and digital variable phase shifters 106 phase shifters 108 are exploited at the overlapped sub array level as shown by the schematic in

FIGURE 1. Both the stages may be switched and controlled by a microcontroller.
A sum beam is required to generate and steer the phased array radiating elements 100 in desired directions.. The sum pattern generation in the present invention is implemented by the time-delay unit 102 which is a Programmable Switching Matrix (PSM) as seen in FIGURE 2.
FIGURE 2 shows a two-level PSM for simplified eight element linear array to be exploited for sum pattern generation which can be steered to any desired direction.
Each radiating element of 100 at the main array level is connected to a time delay unit 102 which is a programmable time delay matrix as shown in FIGURE 2 of the accompanying drawings. A uniform linear array of eight elements of inter-element spacing of λ/2 is selected for illustration. These are subdivided into two overlapped sub arrays of having seven elements each. Firstly, in order to generate and steer the sum pattern in the predefined direction elements in each sub array are fed to the PSM. In the PSM, a unit delay T is fixed up by coaxial line length for wideband operation.
Each radiating element is referred to ANT 1, ANT 2 and the like in FIGURE 2 is connected to a two layer time-delay matrix with layers denoted arbitrarily as 'A' and 'B' respectively. Each antenna is immediately connected to layer 'A'. Layer 'A' consists of a dual-pole three-throw (DP3T) RF switch. In between the two poles the time-delay (denoted by xT,

where x is a selectable value) is inserted. The switch matrix can select any one of the three alternative paths with different values of time-delay settings.
The two levels of delay lines are microcontroller programmable and switched by fast responding PIN diodes (A0, A1, A2 and B0, B1, B2) with proper combination of digital bits. Digital word (here six bit) is provided in such a fashion so that in each level (either A or B) only one path is selected (switched ON). Only seven combinations are non-redundant here and as a result the gradients are; OT, ±1T, ±2T, ±3T. For instance, OT beam will be in the broad side direction and for other combination beam is steered in any desired direction for the purpose of beam steering and if, AO is selected for ANT 1, it automatically suggests that only AO path will be selected for all other elements. Thus, for ANT 1 to ANT 6, layer 'A' introduces a progressive delay of 2T (12T, 10T, 8T etc). The same logic is applied to layer 'B' also. However, the paths for layer 'A' and layer 'B' are separately selectable. This configuration reduces the need for multiple control signals for individual delay setting.
The outputs of the time-delay matrix 102 for individual elements are combined using the splitter/ combiner 104 to form two sub arrays as explained before. At the sub array level, outputs of the two sub arrays are combined in a manner where a multi-bit digital phase shifter 106 and a phase shifter 108 is connected to the sub arrays.
The phase'shifters 106 at the sub array levels generate the difference pattern when priori direction of interference arrival is known. Difference pattern

forms the null in side lobe region and suppresses the adjacent lobe heights to reject wide angle interference. The difference pattern from both the sub-arrays is combined using a power splitter/ combiner 110 and sent to a transmitter/ receiver 112.
According to another embodiment of the invention, the introduction of multi-bit phase-shifters 106 at the sub-array level offers null forming option at various positions. For null formation, phase shifters at sub-array are finely tuned to form difference pattern at the predetermined angle of strong interference arrival. Thus, when the angle of arrival of jamming signal is known, a simple expression is evaluated to compute the phase shifter value required to be imposed in the sub-array level. For instance, if a jamming signal is known to be getting injected from an angle of 9 = 65 , a null is placed there, by setting the digital phase shifter with a value that is a function of cosine of 65°, The use of time-delay matrix at the array level ensures wideband scanning system while the use of multibit digital phase shifter at the sub-array level ensures a precise null placement for a given frequency of jamming signal.
The system design proposed by the present invention removes the restriction of using multiple types of feed network designs for the cases where the same wireless service is allotted different spectrums in different regions of operation within a broad frequency band allocation.
Further, an important aspect of this invention is to design the control network for adaptive null generation, which is realized in the sub-array

levels. This is conventionally implemented by digital variable phase shifters with high resolution and by confirming that one half of the sub-array is out of phase with other half.
In the present invention, the sub-array #1 (102-1) will be out of phase with the second sub-array #2 (102-2). With this consideration, the difference pattern is generated in any direction mainly in the side lobe region around main lobe. Difference pattern in the sidelobe region creates null in the angle arrival of interference after having some priori knowledge.
Hence in the present invention, both the sum pattern and difference pattern are digitally controlled for beam formation and adaptively interference rejection in the quiescent pattern which is highly desirable from radar and communication point of view.
MATHEMATICAL FORMULATION:
Mathematically, the sum pattern of the linear elements in each subarray is given by the following expression:
F(θ)exp(-jny) (1)
Where, N is number of elements and
y/ = kdcosθ +β and main beam will be in direction (target) of θ0 when phase gradient to be maintained is β- -kdcos θ0 .

Difference pattern M is the number of sub array and expressed by the following equation:

Where f =kdcos+a and difference pattern with broad null will be in a0 direction (interference) when a~- kdcos&. Then the resultant pattern Fs (6) is the multiplication of array pattern and sub array pattern.
Fs (0) =F (θ) S (Φ) (4)
Therefore, the resultant pattern imposes a desired null without changing the quiescent pattern.
EXPERIMENTAL DETAILS
CASE-1: Main beam at boresight:
For instance, when it is required to steer the main beam in the broadside direction, inter-element phase gradient (time delay) at the element level should be zero. This is obtained from the matrix shown in the FIGURE 2 by loading A0=0, Al=l, A2=0 and B0=0, Bl=l, B2=0 or delay gradient OT. Now suppose the main beam is situated at this angle and arrival of a wide

angle interference signal is estimated near 65°. According to this proposal, in order to minimize the effect of interference, a difference pattern should be formed at angle of 65°. Difference pattern can be obtained in the sub array level by adjusting the variable phase shifter such that, inter-element phase difference be -n cos65° and to one half of the sub array elements (here second sub array) with additional 180° of phase difference. Matlab® simulation in FIGURES 3 and 4 shows quiescent beam in the boresight direction and adaptively suppressed pattern around 65°. The results show an wide angle interference cancellation of 15 db.
FIGURES 5 and 6 show the interference rejection at angles 45° and 115° with respect to the quiescent pattern in FIGURE 3, keeping delay gradient at element level unaltered (0T).
CASE-2: Main beam steered:
Now the beam is to be steered in different angular positions. As an example, for 70°, this is implemented by assuming unit delay of T=7i/6 and loading word pattern A0=1, A1=0, A2=0 and B0=1, B1=0, B2=0 in the PSM matrix, This bit pattern provides -3T as inter-element delay gradient or corresponding phase gradient -n/3 which is very applicable for steering the beam in that particular direction. Simulated results can be seen in FIGURES 7, 8 and 9 depicts the quiescent pattern at 70°. After generation of the difference pattern, suppression is formed in the side lobe at 40° and 95°. Squint and distortion in the main beam is negligible after adaptive shaping. FIGURES 10 and 11 represent the suppression at 140° and 85° respectively corresponding to quiescent pattern in the FIGURE 12.

TECHNICAL ADVANTAGES
The technical advancements of the present invention include in providing a wideband phased array system that consists of a time-delay unit at the radiating element level to enable wideband and steerable operation of the radiating elements and digital variable phase shifter at sub array level to position the null. If a strong interfering signal is a little away in frequency from the operating frequency of the radiating elements, the same phase shifters can be used to recalculate the phase shifting required to place the null. Therefore, the system makes null placement independent of the frequency and scanning angle of the radiating element arrays.
Additionally, the overlapping of the radiating elements at the sub array level allows the phase centre at the sub array level to be less than one wavelength thereby ensuring that grating lobe is not observed.
Further, the system has the ability to place the null at desired angular location by knowing only two parameters (for the interfering signal) namely frequency and the angle of imposition and without affecting the desired operation of the main array. The system does not require complex weighting coefficients techniques to place the null at the desired location.
The present invention increases the cell capacity by suppressing the interference using directional beam and suppressing the jam signal by positioning the location of Null. The cell capacity can be additionally

increased by using space division multiple access along with TDMA using switchable beam base stations including cellular and WLAN systems.
Due to the above novel features the present invention can be used in:
• switchable beam antennas for ultra wideband communications, specifically for high definition video transmission applications in home entertainment systems;
• Software Defined Radio (SDR) applications in multi standard and multi band stations; and
• high multipath fading environments like mines and factory floors.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment as well as other embodiments of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

WE CLAIM:
1. A programmable wideband phased array system, said system comprising:
• a main linear array of M radiating elements where the distance d between each of said radiating elements is less than one wavelength (X) of the operating frequency of said phased array system, where M is a positive integer;
• time-delay units discretely connected to each of said radiating elements to form a sum pattern signal to enable wideband and steerable operation of the phased'array;
• a splitter element coupled to said time-delay unit to receive said sum pattern signal, said splitter element adapted to form two discrete sets of sub-arrays, each set containing (M-1) elements, where at least one element of one set overlaps a corresponding element of the other set;
• phase-shifters connected discretely to each of said sets of sub-arrays adapted to receive the sum pattern signal and further adapted to detect an external interference signal and form a difference pattern signal, said difference pattern signal is a function of cosine of the detected angle of interference to position a programmable null signal at the location of the external interference signal impinging on said phased array system;
• a combiner element coupled to the phase shifters to combine the output signals of the phase shifters to form a combined difference pattern; and

• transmitter and receiver element to transmit said combined output
signal and/or receive external signals.
2. The system as claimed in claim 1, wherein the each of said sets of sub-arrays consists of (M-2) overlapping elements.
3. The system as claimed in claim 3, wherein the overlapped sets of sub-arrays contain one of either the first or the Mth radiating element,
4. The system as claimed in claim 1, wherein said time-delay unit is a time-delay based Programmable Switching Matrix, said Programmable Switching Matrix having:

• two levels of programmable delay lines connecting a plurality of dual-pole three-throw RF switches;
• unit delays and PIN diodes connected between the two poles of said switches; and
• coaxial cable transmission lines for the interconnection of delay lines with the switches, unit delays and PIN diodes and for wideband operations of said system.

5. The system as claimed in claim 5, wherein the unit delays are assigned pre-determined delay values.
6. The system as claimed in claim 1, wherein said phase shifters include a digital variable phase shifter which can be connected to either or both of the sub-arrays.

7. The system as claimed in claim 1, wherein said system includes a
microcontroller to control the operations of the time-delay unit and the
phase shifters.
8. A method for pattern generation, steering operation of a wideband phased
array system and positioning a programmable null at the location of
external interference, said method comprising the following steps:
• using the radiating elements of the phased array system to generate a beam;
• steering the beam in the desired direction using a sum pattern generated by using true time based delays;
• transmitting the steered wideband signal;
• sensing the arrival of an external interference signal and the angle/location of interference using well known methods; and
• shifting the phase and generating a difference signal which is a function of cosine of the detected angle of interference for nullifying the effect of the interference.
9. The method as claimed in claim 8, wherein the step of providing a true
time-delay includes the steps of:
a. connecting a two layer time-delay based Programmable Switched
Matrix to each of the radiating elements with a dual-pole three-
throw RF switch;
b. providing fast responding PIN diodes and unit delays having a pre
determined value between the two poles of the switch; and

c. interconnecting the aforesaid elements with a coaxial transmission line.
10.The method as claimed in claim 8, wherein the step of generating a sum pattern signal includes the steps of selecting any one of the three alternative paths provided by the dual-pole three-throw RF switches each path having a pre-determined value of time-delay settings as assigned to the unit delay element of the programmable switched matrix.
11. The method as claimed in claim 8, wherein the step of generating a difference pattern signal includes the step of detecting the angle/location at which the interference signal is impinging on the system, shifting the phase with a value that is a function of cosine of the detected angle of interference, generating a difference pattern (null signal) and placing the null signal at that location.