Antenna system and radar system incorporating the same

Abstract

An antenna system comprising an array of antenna elements, the array comprising a plurality of groups of antenna elements wherein each group comprises one or more antenna elements arranged in series, and wherein the system further comprises first phase-control means for performing the function of introducing respective phase-shifts to transmitted or received signals passed to or received from each of said groups to provide beamforming and second phase-control means for performing said function with respect to a sub-set of said groups. An antenna system of the invention allows two radar beam patterns having different spatial characteristics to be generated using a single antenna system. The invention also provides a radar system incorporating an antenna system of the invention.

1 . An antenna system comprising an array of antenna elements, the array comprising a plurality of groups of antenna elements wherein each group comprises one or more antenna elements arranged in series, and wherein the system further comprises a first phase-controller arranged to perform the function of applying respective phase-shifts to transmitted or received signals passed to or received from each of said groups to provide beamforming and a second phase-controller for performing said function with respect to a sub-set of said groups. 
   
   
       2 . An antenna system according to  claim 1  wherein at least one of the first and second phase-controllers comprises a Rotman lens. 
   
   
       3 . An antenna system according to  claim 2  wherein both the first and second phase-controllers each comprise a Rotman lens. 
   
   
       4 . An antenna system according to  claim 1  wherein the array of antenna elements is substantially rectangular and each of said groups of antenna elements is a row or column of the array. 
   
   
       5 . An antenna system according to  claim 4  wherein said sub-set of groups is made up of contiguous rows or columns of the array. 
   
   
       6 . An antenna system according to  claim 5  wherein the array of antenna elements is substantially planar. 
   
   
       7 . An antenna system according to  claim 4  wherein array of antenna elements and the Rotman lenses are mounted on a common former. 
   
   
       8 . An antenna system according to  claim 7  wherein the former is substantially cuboid and the first and second Rotman lenses are mounted on respective opposite faces of the cuboid former and the array of antenna elements is mounted on a face of the cuboid former adjacent to the faces mounting the Rotman lenses. 
   
   
       9 . An antenna system according to  claim 7  wherein the former is laminar. 
   
   
       10 . An antenna system according to  claim 1  wherein each antenna element is a patch antenna element. 
   
   
       11 . A radar system comprising an antenna system according to  claim 1 . 
   
   
       12 . A radar system according to  claim 11  wherein at least one of the first and second phase-controllers comprises a Rotman lens. 
   
   
       13 . A radar system according to  claim 12  wherein both the first and second phase-controllers each comprise a Rotman lens. 
   
   
       14 . A radar system according to  claim 13  further comprising first and second RF switches coupled to the first and second Rotman lenses respectively. 
   
   
       15 . A radar system according to  claim 14  further comprising a monolithic microwave integrated circuit (MMIC) operable to provide a transmission signal to each RF switch. 
   
   
       16 . A radar system according to  claim 11  wherein the radar system is a FMCW radar system. 
   
   
       17 . A radar system according  claim 16  further comprising a RF oscillator, a DDS arranged to provide a frequency-modulated signal and a mixer arranged to mix respective outputs of the RF oscillator and the DDS to provide a FMCW signal for transmission, and wherein the clock signal of the DDS is derived from the Rb oscillator output. 
   
   
       18 . A radar system according to  claim 17  comprising one or more ADCs arranged to digitise received signals and wherein the clock signal of each ADC is derived from the RF oscillator output. 
   
   
       19 . A radar system according to  claim 17  and further comprising a frequency-divider arranged to frequency-divide the output of the RF oscillator to generate the, or each, clock signal. 
   
   
       20 . A radar system according to  claim 17  wherein the RF oscillator is a free-running DRO. 
   
   
       21 . A radar system according to  claim 11  and arranged to produce from the antenna array a transmitted signal having a frequency which is a function of transmission direction. 
   
   
       22 . A radar system according to  claim 11  wherein the radar system is monostatic. 
   
   
       23 . A radar system according to  claim 11  wherein the radar system is bistatic. 
   
   
       24 - 26 . (canceled)