Research Article Lowering the Sidelobe Level of a Two-Way Pattern in Shared Aperture Radar Arrays John N. Sahalos 1,2 1 Radio-Communications Lab, Aristotle University of essaloniki, essaloniki, Greece 2 Department of Engineering, University of Nicosia, Nicosia, Cyprus Correspondence should be addressed to John N. Sahalos; sahalos@auth.gr Received 23 October 2020; Revised 25 November 2020; Accepted 22 December 2020; Published 6 January 2021 Academic Editor: Ping Li Copyright©2021JohnN.Sahalos.isisanopenaccessarticledistributedundertheCreativeCommonsAttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A study of lowering the peak SLL of shared aperture radar arrays is presented. A two-weight amplitude distribution for the elementsoftransmitandreceivearraysisused.Imposingcertainconditions,therelationofthenumberofelementsofthearrays wasfound.Oneconditionimposestheappearanceofaminorlobepositionoftransmitorreceivearraypatternatacertainnullof receiveortransmitarraypattern.Asecondconditionimposestheequalsidelobeleveloftwoconsecutiveminorlobeseithernear themainbeamofthetwo-wayarraypatternoratcertainpositionsofreceiveortransmitarraypattern.eresultingpeakSLLof the two-way radar array pattern depending on the conditions reaches from −47dB up to less than −50dB. 1. Introduction Radar systems need to have antennas with narrow main beam and suppressed sidelobes. In [1–4] and the references therein, one can find recourses and design techniques of several radar antennas. A radar structure with excellent performance contains transmit and receive phased arrays at the same aperture. is structure, except for the perfor- mance,hassignificantadvantagessuchasreducedbulkiness and lower manufacturing costs. In the international litera- ture, [5–9], there are interesting design techniques of in- terleaving and/or tapered arrays where several analytical or numericalmethodsaregiven.eideaofHaupt[10–12]for synthesizing a receive array that places nulls of the receive pattern in the directions of the peak of the sidelobes of the transmit pattern was proved to be extremely useful and successful. In [13], Haupt’s idea was extended by equating thelevelofthefirsttwominorlobesofthetwo-wayradiation pattern. Moreover, to reduce the SLL up to −45dB, it was proposed in [13] to use two different amplitude weights for the elements of transmit and receive arrays. In this paper, an effort is made to minimize the SLL by using the two-weight arrays and searching possible condi- tions for the two-way array pattern. e reduction of the SLL,dependingontheconditions,isbetterthanthatof[13] and goes from −47dB up to less than −50dB. 2. Formulation Let us consider a transmit and a receive linear array of discrete elements along the x-axis with equal interelement distance d (see Figure 1). etransmitarrayhas N t elementswitharrayfactorAF t while the corresponding receive one has N r elements (N r ≤ N t ) with array factor AF r . e excitation of the above arrays combines the ad- vantages of taper distribution and the simplicity of the feed network of uniform arrays [13]. e two amplitudes of the elements are W 1 and W 2 and their distribution is shown in Figure1.eelementswiththerelativeamplitude W 2 arein the middle, symmetric in both arrays. In the receive array, nonreceiving edge elements exist. e number of elements with a relative amplitude W 2 is M in both arrays. Let us suppose that W 1 � 1 and W 2 is expressed as W 2 � 2 +(δy), (δy) > 0. (1) e transmit and receive array factors are Hindawi International Journal of Antennas and Propagation Volume 2021, Article ID 6685565, 10 pages https://doi.org/10.1155/2021/6685565