The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this paper, the variation of side lobe level (SLL) of ‘optimized uniformly excited time-modulated linear antenna array’ (OUE-TMLAA) with different number of antenna elements is presented. To realize the optimized array patterns of the arrays, sideband levels (SBLs) is suppressed to below −30 dB and the increase on first null beam width (FNBW) is restricted within 35% of that of the ‘uniformly excited...
In several applications such as wireless communication, radar; shaped beam patterns are used to radiate power in a desired sector of region while suppressing the power towards the other direction to avoid interferences. This paper introduces a new technique to synthesizing flat-top shaped power pattern in time-modulated unequally spaced linear arrays (TMUSAs). Since, TMUSA synthesis problems are multimodal,...
In this paper, sideband radiations which are generally regarded as the undesired effects of time-modulated antenna arrays (TMAAs), are exploited to design multi-beam antenna arrays. Time modulation (TM) is applied into uniformly excited linear array of half wave dipole radiators to generate low side-lobe sum and difference patterns at the center frequency and first sideband respectively while the...
In this work, the effectiveness of a relatively newly developed optimization algorithm, artificial bee colony (ABC) algorithm has been employed to synthesize uniformly excited, non-uniformly spaced, symmetrical linear arrays. ABC is used to reduce the side lobe level (SLL) of uniformly excited linear antenna arrays by taking the element spacing as the optimization parameters. The effectiveness of...
In this paper, a cosecant squared shaped beam pattern is synthesized from a uniformly spaced but nonuniformly excited linear antenna array where the uniform spacing of the array elements is considered as half of the desired signal wavelength. The shaped beam pattern is synthesized for the angular beam width of 32° by reducing the side lobe level (SLL) to −20.06 dB and almost without any ripple in...
In this paper, a flat-top beam pattern is generated through time modulation of linear array. Three parameters; side lobe level (SLL), ripple (R) and transition width (T) related are obtained as −30.2dB, 0.1dB and 6.4° respectively. To simplify the complexity of the feeding network, only two states of static phase shift (0, π) is considered. The maximum side band radiation level of the first two sidebands...
In this paper, a new approach to reduce the side band radiation level of time modulated linear array is presented. Keeping normalized on-time duration of the array elements at each modulation period remains unchanged for a given pattern at fundamental radiation, a suitable time delay is provided before the switch-on instants of the array elements. The method is applied to the pattern where the fundamental...
In addition to the desired frequency, theoretically the Time Modulated Antenna Array (TMAA) radiates signals at the infinite number of different harmonics of the modulation frequency. But the radiation energy at the first few harmonics (called sidebands) is most significant. In this paper, the maximum radiation at first two harmonics of TMAA has been studied for the different values of the side lobe...
In addition to fundamental frequency, Time Modulated Antenna Array (TMAA) also radiates at different harmonics (sideband) of modulation frequency Generally radiation at first few harmonics contain significant amount of power. In this paper, the maximum radiations at first three sidebands of uniformly excited TMAA are characterized by uniformly changing switch-on time of each element. The normalized...
In this work, the Artificial Bee Colony (ABC) algorithm is used to minimize the side lobe level of the main beam and the first two side band radiation of the uniformly excited time modulated linear antenna array. ABC searches the switch on or excitation time duration of each of the element of the antenna array under consideration. This approach gives satisfactory results without changing the amplitude...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.