Patent ID: 6081232
Filing Date: 2000-06-27
Classification: H01Q

Abstract:
In a Mach-Zehnder interferometer commonly used in an electro-optical beamforming network for phased array antennas, the interferometer having a first and a second electro-optical phase modulators, a source of coherent beam positioned to supply optical signals to the modulators, a frequency shifter for receiving therein the modulated optical signals from the first modulator, a voltage source connected to the second modulator to provide phase control to the optical signals travelling through the second modulator, a detector coupled to the shifter, the detector being further coupled to the second modulator via a coupler; an improvement to the Mach-Zehnder interferometer to render the interferometer suitable for use in an antenna system having optical control of beam direction and employing at least a pair of such improved Mach-Zehnder interferometers, the interferometers having identical elements but different pre-determined beam propagation directions, said improvement to each Mach-Zehnder interferometer comprising: a receiving antenna having beam scanning capability for receiving signals from a distant transmitter; a first amplifier coupled between said receiving antenna and the frequency shifter, said first amplifier providing gain control to the received signals and the shifter mixing the amplified received signals with the coherent beam from the beam source to produce an output signal, said output signal thereafter being input to the detector wherein said output signal is combined with phase-controlled optical signals from the second modulator to yield an outgoing signal having a pre-determined direction of propagation; a transmit antenna for transmitting said outgoing signal and a second amplifier coupled between the detector and said transmit antenna for amplifying said outgoing signal prior to transmission.