A linear antenna array receives incoming microwave signals which are coup to a wide-angle, microwave lens to produce a received beam pattern in azimuth. The beam pattern is crystal detected and log video amplified to produce an output signal comprising directional information in the amplitude level. The directional information is processed in a logic processor which converts information into binary voltage levels which are gated to appropriate switch drivers and to automatically decide the discrete received beam detecting target signal and to activate a switch which will enable ECM signals to be transmitted to radiate in the desired transmit beam. ECM signals which are gated through the switch apparatus by inputs from the logic processor are coupled to a second microwave lens apparatus which forms a beam pattern to be transmitted which is retro-directive with respect to the received beam pattern. The beam is transmitted by a linear antenna array.
A phased array antenna system having low power amplifiers reduces power loss through several tens meters high frequency cables. The antenna system for transmitting a signal in a base station, comprising: a phased array unit for selecting an input signal through one of a plurality of beam ports, for dividing the input signal into a plurality of signals and for outputting the plurality of signals through a plurality of array ports, each of the signal having a linear phase difference according to difference of propagation path; a switch for receiving the input signal from a base station, for selecting one of the plurality of beam ports of said phased array and for transmitting the input signal to the selected beam port, responsive to a control signal transmitted from the base station; a plurality of low power amplifiers for low power amplifying the plurality of signals inputted from the plurality of array ports of said phased array; and phased array antennas for radiating the plurality of signals from said plurality of low power amplifiers, thereby providing a spatial power summation into a direction of equiphase plane allowing effective radiated power sufficiently enough to cover a cell into a steered direction selected by said switch.
A low cost antenna in a base station suitable for deployment where high density of wireless users are present in specific directions (e.g., cross roads in urban areas). A lens is used associated with antenna elements to collimate the beam for a longer distance in the desired directions. By using the lens, the need for complex electronics is minimized, thereby reducing the cost of a base station. Another aspect of the present invention enables the lens to be designed precisely by first determining the radiation pattern of each array element according to a corresponding coordinate system, transforming the radiation pattern to a common coordinate system, and determining a composite radiation pattern using the value determined for the common coordinate system. Inverse scattering technique is applied using the composite radiation pattern and the desired collimation pattern to determine the precise shape of the lens.
A radio frequency transponder/repeater is provided wherein an array of receiving antenna elements is coupled to an array of transmitting antenna elements to provide a directional antenna system and including additionally an internal radio frequency source which is also coupled to the array of transmitting antenna elements. With such arrangement, an internally generated signal provided by the radio frequency source may be transmitted using the transmitting array of the Van Atta System.
Apparatus and method for determining velocity and range of a target within a field of view. A velocimeter and tracker (10, 100) includes a laser (12, 12') that produces modulated coherent light, a portion of which illuminates targets (22, 22') coming into a field of view (24, 24') of the velocimeter and tracker. Coherent light reflected from the target travels back along a detection path toward a phase conjugate mirror (40, 40') as a probe wave (26, 26'). A higher intensity portion of the coherent light produced by the laser is split into equal parts that are directed toward the phase conjugate mirror from opposite directions and interact with the probe wave to produce a phase conjugate light signal that travels back along the detection path and is also reflected from the target. Light reflected by the target experiences a Doppler phase shift as a function of target velocity. First, second, and higher order phase shifted signals reflected from the target are imaged on photo diodes (68, 68'), producing an electrical signal having components corresponding to the frequency differences of the various order light signals. As a function of the sums and differences of the frequency components of the electrical signal, the range and velocity of the target are determined.
An optical limited scan antenna system is disclosed. The invention is a dual lens type array antenna system with a small array feed network. The system includes a bootlace-type microwave aperture lens with an array of radiating elements arranged along the linear aperture and an array of pickup elements arranged along the curved inner surface, an intermediate optical corrective lens, a feed array for illuminating the corrective lens with a source distribution, and with a power divider and phase shifters arranged to drive the feed array. The corrective lens is circularly symmetric (spherically symmetric in the three-dimensional case), and its radially varying dielectric constant is such that a point source on its surface is focused to an image point on the inner surface. The pickup elements on the curved surface of the aperture lens are coupled to corresponding radiating elements on the linear aperture. The corrective and aperture lens cooperate to map an input or source distribution into an aperture distribution which is a scaled version of the source distribution. The system results in high efficiency obtained with a minimum number of active elements and relatively low cost optical components.
