Abstract: A method for the design of medium gain (15-25 dB) microstrip array antennas is described. A modular approach is utilized in which a given antenna is used as a building block for higher gain antennas. A series of X -band antennas were built in this way, and the results seem to validate the usefulness of the method.

Abstract: Conventional adaptive antenna array processing employing gradient descent requires access to signals on all the antenna array elements. The processing can be carried out at the radio frequency stage, an intermediate frequency stage, and in some cases at baseband. In all cases coherence of the array element signals must be maintained. For situations where access to all the array channels is not possible or not economical, a new technique for adaptively controlling the array weights has been developed. The technique requires access to the controllable weights and the beam-former output. Detailed analysis of the performance of the technique has been carried out. A number of possible structures which can be used are briefly reviewed, and the results of analysis of the performance achievable with some of these/structures are presented. A detailed comparison of the performance of the new technique with that of a system in which all signals are available is given. Ways of optimizing the performance of the new technique are considered. Results of computer studies of the performance of the new technique are presented.

Abstract: This invention utilizes an opto-electronic matrix switch to select a set of fixed value phase shifters. Signals which are selectively phase shifted by this apparatus may be introduced into the signal path of each antenna element of a phased array antenna. In one embodiment the input signal is converted into an intensity modulated optical signal which is then split between paths of different length to provide different delays and hence different phase shifts. The matrix then selects a particular set of the phase shifted signals which are converted back to electrical signals and fed to the antenna array elements.

Abstract: A scannable antenna array especially suited for aircraft having a common reflector and a plurality of spaced apart end-fired Yagi type elements each comprising a driver and one or more director segments spaced mutually from each other and the driver in the direction of the field pattern for the array. In the preferred embodiment, the driver is a dipole comprised of two laterally extending hooked-back radiating segments so dimensioned and spaced from the director elements so as to minimize the mutual electromagnetic coupling among elements of the array. In other embodiments, the driver may comprise a slot.

Abstract: A fiber optic data distribution system is disclosed for distribution of the phase shift commands to an electronically steered antenna array. Novelties include the fan-out of a single bundle to multiple receptors, equalization of optical path for precise synchronization, the use of the RF active side of the antenna for data distribution, the use of the antenna radome as support structure for the fiber optics, and an optical reflector to divert light from the plane of the radome to the transmit/receive element.

Abstract: A system for indicating the direction of a source of radio waves received by a circular antenna array (12) includes a Butler matrix (18) that receives the array outputs and feeds the resultant matrix outputs to correction circuits (22) whose transfer functions are the inverses of the direction-independent factors of antenna patterns generated by antenna elements driven at relative phases that advance around the array at rates that complete an integral number of cycles in one circuit of the array. The resultant corrected signals are fed to a compressive receiver (26), which accordingly generates an output on an output port whose position indicates the direction of the source of the signal.

Abstract: A radiating element (10) having a continuous aperture substantially greater than one half the center frequency wavelength for use in an electronically scanned phased array antenna operating in the range of 94 GHz. The new radiating element comprises a ferrite block (12) having a radiating aperture which measures 5 lambda by 5 lambda in contrast to the conventional discrete radiating element which measures one-half lambda by one-half lambda. A tapered magnetization (see lines 22) is applied to the continuous aperture ferrite block (12). The degree of phase shift can be varied by adjusting the slope of the tapered magnetization. This permits scanning of the continuous aperture pattern. When a plurality of such continuous aperture subarrays is used to form an antenna array (80 or 100), provision is made to adjust the phase at the center of each continuous aperture subarray with respect to the phase of the adjacent subarrays, thereby allowing scanning of the entire pattern of the phased array antenna (100).

Abstract: An automatic direction finder antenna array having a plurality of pairs of oppositely positioned antenna elements arranged radially from a common center with each pair forming a cardioid radiation pattern when energized. Switching apparatus energizes successive antenna pairs to produce a rotating cardioid pattern but with the cardioid being switched back and forth 180° at a higher switching frequency when each pair of antennas is energized during the rotating function. The antenna AX whose output bears the lowest ratio R to the output of its oppositely positioned antenna is determined as well as the antenna AZ having the largest output signal VZ. The precise angle of reception of a received signal is then determined from AX, AZ, and R.

Abstract: Multiple beam antennas are modified and improved through the use of lenses coupled together by hybrid junctions. A dual lens structure avoids circulators while permitting the lenses to be used both for transmission and for reception. A six lens structure provides perfect phase focusing utilizing an R-2R geometry with a Mobius topology, giving 360 degrees of independent antenna beams from a single circular or cylindrical antenna array.

Abstract: Signals from antenna elements (14) of a rectangular array (12) are translated in frequency by mixers (16) fed from a chirped local oscillator (19). The resultant signals are fed to the first of two groups (20 and 36) of two-dimensional delay lines connected in series at right angles to each other. The two-dimensional delay lines are dispersive, having a linear relationship of delay to frequency, and the sweep rate of the local oscillator (19) is such that the signals caused by a given frequency component at the mixer input ports are completely compressed in time when they reach the output ports (46) of the delay lines of the second group (36). As a consequence, the device performs a three-dimensional Fourier transformation from time and two spatial dimensions to temporal frequency and two dimensions of spatial frequency. When fed by a two-dimensional antenna array, the output of the device can readily be interpreted as indicating the direction of the source and the frequency at which it is radiating.

Abstract: Recent theoretical and experimental investigations have established the phase-mode technique for directional pattern synthesis in circular arrays of nonisotropic sources. For non-isotropic sources the possibility of phase-mode stability has emerged, indicating wideband directional patterns. In the letter a further examination analysing the shape of the element pattern for phase-mode stability is presented.

Abstract: Multiple interference sources are independently acquired, tracked and canled in a multi-element antenna array where the number of antenna elements n is an integer power of the base 2, i.e. n=2 M where M is the number of sources desired to be cancelled. The antenna elements are selectively coupled to sets of n/2 phase shifters in respective closed loop control circuits and operate in phase controlled sets, one for each interference source. The phase of the received signal incident on one half of the elements in each set is independently adjusted relative to the other half, for each desired null in a separate control loop, such that for a particular interfering source each antenna element of the set has one corresponding neighboring element in a pair of elements whose phase mutually differs by 180° at the space angle of the arrival of the interference wavefront relative to the axis of the antenna. This produces a substantially infinite null in the direction of arrival of the particular interfering wavefront and thus complete cancellation of that interfering source is effected. This null is retained as other interfering sources are independently acquired, nulled and tracked by a respective different set of n/2 elements in the same array.

Abstract: A external feedback network (4, 5) for decreasing variations in a beam pointing angle of a scanning antenna array. A dedicated aperture manifold (4) is integral with the aperture (1) of the scanning antenna and provides a signal which represents the beam pointing angle. The signal is detected (13), decoded (15), and converted into digital data for averaging and processing by a central processing unit a (CPU). The processed data is then compared with a value stored in memory and any difference forms the basis of a correction signal. For application to a microwave landing system, the correction signal is used to adjust the start/stop time of the scanning commands of the antenna to remove the error without modifying the beam steering algorithm. A space-coupled monitor (6,7) may also be used independent of the feedback network to provide an alarm indication in response to any failure of the dedicated aperture manifold (4), the automatic stabilization circuitry (5) or the array system (1, 2, 8, 9, 11).

Abstract: A computationally efficient method for estimating the angle of arrival of the strongest plane wave incident on a sparse circular antenna array is described. In the example investigated, the elements of the array are spaced by more than 5 1/2 \lambda , eliminating the problems of mutual coupling. An unambiguous estimate of the angle of arrival is obtained by a beamforming approach. Results of computer simulations are presented which show the processing to be robust in the presence of noise, multipath signals, and antenna element positioning errors.

Abstract: A moment method analysis of infinite microstrip dipole arrays which uses an efficient technique to evaluate the generalised impedance matrix is described. A particularly simple formulation is obtained through the use of the periodic Green function. Results for the reflection coefficient magnitude against scan angle are given for a typical array.

Abstract: The arrangement is for cancelling unwanted sidelobes in travelling-wave arrays, especially the back lobe (5) where the main beam (4) approaches the end-fire direction; the array should have high symmetry, ie, with the usual form of array (radiators spaced along a single feeder), the radiation patterns when fed from either end should be mirror images. Cancellation is obtained by having feed connections (2, 2') at both ends of this form of array (1), the feed at one end being attenuated (8) relative to the other and effectively subtracted (6) therefrom. In RF form, for receiving or transmitting, the subtraction can be effected by phase-reversing (7) the signal in one of the feed connections. In baseband form, suitable for receiving only, diodes are included in both feed connections and subtraction performed at baseband frequency.

Abstract: A planar active antenna array design combines miniature beryllia amplifiers using batch process techniques with an open-celled microstrip antenna. A thin, very light active antenna subarray using these technologies has been developed and tested.

Abstract: The basic similarities and essential differences between adaptive processing structures in the space and time domains are considered. Attention is focused on the fact that a cascade structure is required to decorrelate the signals received from different elements of an antenna array, while a very different and more efficient lattice filter structure may be used to decorrelate successive samples of a time series. The difference is explained by examining the Levinson-Durbin recursion algorithm, which essentially gives rise to the lattice filter structure. The algorithm is presented in a generalised form which takes into account the effect of non-stationary statistics and shows clearly how the use of recursion in time is fundamentally responsible for its efficiency. The algorithm is clearly not appropriate for antenna array decorrelation or in the spatial domain generally.

Abstract: An adaptive antenna array is described having least two antennae 26 associated with at last one acousto-optic time-integrating correlator 28 having an optical input and an acoustic input The optical input is modulated in accordance with the signal received by one antenna of the array and the acoustic input is modulated in accordance with the signal received by another antenna of the array, whereby the correlator produces an output representative of the time delay between the signals received by the respective antennae A processor 30 records the time delays between the individual signals received by the antennae 26 and programs time delay units 29 so that all the return signals are combined in phase

Abstract: Three methods for sidelobe reduction in linear antenna arrays using only one or two discrete amplitude levels are compared. The trade-off between the complexity of implementation and the achievable peak sidelobe level is demonstrated.

Abstract: Technology features of a beam forming network (BFN) employing ferrite devices to provide multiple beam antenna pattern control for satellites used in telecommunications are described. The BFN produces the phase and amplitude distribution for each horn in an antenna array, with the number of horns in the array being equal to the number of outputs in the BFN. One configuration involves microwave switches and permits illumination of a single feed horn at a time using ferrite latching circulators that function by reversing the circulation direction. A more flexible version, yielding a variable amplitude distribution across the feed horn array to accommodate changing traffic patterns or serving a TDMA system, includes the capability of forming nulls in the system with a variable phase shifter in the input ports. The antenna scan angles in phased arrays can be limited to 8 deg from center. Acceptable insertion losses have been demonstrated in BFN with hundreds of ports and switching rates as high as 10 kHz.

Abstract: The problem of a cavity-backed annular slot array is solved using appropriate Green's functions for the interior and exterior regions of the cavity. The excitation is assumed to be general in form ...

Abstract: The present invention provides a radio direction finding system for a circular antenna array, and includes a plurality of a (e.g. 24) input lines each for receiving signals from a respective antenna of the array, a matrix of digitally controlled switches for switching signals on the input lines to b (e.g. 8) matrix output lines. control means connected to the matrix for selectively connecting a set of b of the input lines connected to adjacent antenna to the output lines, and for varying the selected set of input lines so as to advance the selected group of 8 around the circular array, a beam forming circuit connected to receive signals from the b matrix output lines at 14a...14h, and including a tree of dual input hybrid transformers 19a, 19b, 19c, 19d, 20, 21, and 28, arranged to additively combine the signals so as to produce a sum signal containing information from all the signals on the matrix output lines. wherein the tree includes sets of delay lines, e.g. 16, 17, 18, each set for consecutively introducing different phase delays in an associated signal path of the tree whereby beam slewing is introduced in at least two levels in the combining tree.