Design criteria for wideband active phased array antennas

The instantaneous bandwidth of a phased array antenna can be increased by dividing the aperture into subarrays and placing a time delay network behind each subarray. The size of the subarray determines the instantaneous bandwidth of the antenna. Bandwidth criteria for phased array antennas were previously developed for both narrow band signal with frequency agility and for instantaneous wideband signals. The bandwidth criteria were defined in terms of loss of antenna gain and relative amplitude of grating lobes. Radars may apply an amplitude weighting to the received pulse in order to reduce time sidelobes. This weighting for an LFM (linear frequency modulated) wide bandwidth pulse effectively tapers the contribution from frequencies off midband, resulting in progressively more effective suppression of instantaneous grating lobes out to the edge of the band. The pulse compression of this time weighted receive pulse is formed from the sum of the contributions from the receive patterns over the bandwidth. The process of time weighted LFM pulse compression produces a return that has an effective antenna receive grating lobe contribution much less than that is exhibited by the instantaneous patterns at the band edges. In this paper we examine the receive sidelobe performance of a phased array antenna for instantaneous wide bandwidth after an amplitude taper is applied in the radar receiver.