Antennas are designed to transmit and receive electro-magnetic waves. A phased array antenna is an antenna comprising a plurality of radiator elements (radiators) with a directive radiation pattern (beam) which can be controlled by controlling individual radiator elements (radiators) or groups of radiator elements in the antenna. In general, the steering direction of the radiation pattern is determined by control of the phases of the signal to or from the radiator elements. In conventional phased array antennas the phase control is achieved by phase shifters. The specific phases are typically determined by a digital signal processing (DSP) subsystem.
One example of phased array antennas is disclosed in U.S. patent application Ser. No. 6,759,980 disclosing a phased array antenna comprising an input, a feed network electronically coupled to the input, a plurality of radiators, a plurality of phase shifters for providing phase shifts for the signals prior to transmitting the signals to the radiators or receiving the signals from the radiators, and a controller for controlling the phase shift provided by the phase shifters.
FIG. 1 illustrates a simplified block diagram of a system generally referenced 100 comprising a multiple power divider 140 for distributing the reference signal 101 to one or more transmitter/receiver (T/R) modules, and a simple phased array antenna (PAA) 150, known in the art. FIG. 1 illustrates electronically steering the wave front of a signal. Three possible wave fronts 162, 164, 166 are shown. Reference signal 101 is inputted to the multiple power divider 140. The reference signal is normally generated by a reference signal generator (not shown in FIG. 1).
The power divider 140 distributes the reference signal 101 to four phase shifters 112, 114, 116, 118. The phase shifters 112, 114, 116, 118 provide respective phase shifts s1, s2, s3, s4 degrees (not shown). The wave front 162, 164, or 166 is determined by the phase shifts s1, s2, s3, s4 of the phase shifters. The phased array antenna 150 comprises phase shifters 112, 114, 116, 118, amplifiers 122, 124, 126, 128, and radiators 132, 134, 136, 138. Each of the phase shifters 112, 114, 116 118 is connected to an amplifier 122, 124, 126, 128. Each of the amplifiers 122, 124, 126, 128 transfers an amplified and phase shifted signal to a respective radiator. The PAA of FIG. 1 can steer the wave front only in one dimension, either an azimuth dimension or an elevation dimension.
An exemplary PAA comprises an array of radiators in which the relative phases of the electromagnetic signals radiated by the radiators are varied in such a way so as to cause the radiation pattern of the phased array antenna to be in a desired direction. In FIG. 1, numeral 161 illustrates a radiation pattern (beam).
The simplified phased array antenna 150 illustrated by FIG. 1 typically comprises an array of T/R modules 102, 104, 106, 108 and an array of radiators 132, 134, 136, 138. In the architecture of the PAA of FIG. 1, each radiator is connected to one T/R module. In FIG. 1 only the transmit part of the T/R modules 102, 104, 106, 108 are shown.
Exemplary PAAs use transmitters (TR) or receivers (RX) or T/R modules, which perform functions, such as, shifting the phase of a signal by a predetermined amount of degrees. For example T/R module 102 in FIG. 1 phase shifts a signal by s1 degrees.
An exemplary conventional T/R Module 102 comprises among other elements a phase shifter 112 and an amplifier 122. Exemplary PAA use a plurality of T/R modules, each T/R module comprising a phase shifter (PS). PS are electronic devices enabling the antenna beam to be electronically steered, in a desired direction, without mechanically repositioning the PAA. Conventional PAA are extremely expensive and of high power-consumption, therefore they are mainly used in military applications, such as aircraft radars and missile-radars. For instance, in an exemplary PAA, about 4000 phase shifters are used; each phase shifter costs several thousands U.S. dollars, resulting in a total cost of millions of U.S. dollars for such PAA. There is therefore a need for low cost phased array antennas giving about the same performance of the conventional high cost phased array antennas.