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Micromachined Microwave Phase Shifters
Published in Shiban Kishen Koul, Sukomal Dey, Radio Frequency Micromachined Switches, Switching Networks, and Phase Shifters, 2019
Shiban Kishen Koul, Sukomal Dey
One very important application of the phase shifter is in electronically scanned antenna arrays for modern defense radar systems. It also has commercial applications in advanced wireless communication systems requiring beam steering. Phase shifters allow the antenna beam to be steered in the desired direction without physically repositioning the antenna. Two or more radiating elements are present in a phased array antenna and are spatially arranged that emit phase-shifted signals to form a radio beam. A phase shifter is connected to each radiating element that produces the necessary phase shift to steer the antenna beam [8,9]. The phase of each element is adjusted by steering the beam so that individual signals sum up at the desired beam-pointing angle (theta). Many studies and experiments have been performed on the electronic beam-steering principle. The most popular and useful method is to use phase shifters in combination with an antenna array [10,11]. The method of beam steering is broadly classified as time delay, frequency scanning and phase scanning. The amplitude and phase of each antenna element are controlled, and they both can be used to adjust side lobe levels and steer nulls better than that achieved by phase control alone. Figure 5.1a shows a simple phase shift beam forming for a two-antenna system and Figure 5.1b shows a schematic of a beam-steering front end-based phased array antenna. Phase shifters are the general devices used in phased arrays and they account for nearly half of the cost of an entire electronically scanned phased array.
S
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
Si/SiGe/SiGeC silicon-based alloy system providing band offsets that enable heterostructures that can be utilized for heterojunction transistor design and quantum confinement. sideband the signal produced when a carrier signal is modulated. They may be one single sideband, one set of upper and lower sidebands, or a series of sidebands whose number is dependent on the modulation index of the modulation system being used. sidelobe a lobe in an antenna radiation pattern apart from the main lobe and any grating lobes. Sidelobes have peak amplitudes less than that of the main lobe. side lobe level the ratio of a local maximum in a radiation pattern to the global maximum (main beam) of the radiation pattern. sidelobe level (SLL) the peak amplitude of a sidelobe relative to the peak amplitude of the main lobe. The SLL is usually expressed as the number of decibels below the main lobe peak. Siemens, Ernst Werner von (1816-1892) Born: Lenthe, Hanover, Germany Best known for the German and British companies that bear his name. Siemens was a strong believer in basic research, as well as an avid inventor. His early inventions included an improved gutta-percha wrapped telegraph cable that allowed his companies to secure a number of lucrative cable contracts. His discovery of the dynamo principle, and his use of this in heavycurrent applications, allowed his companies to
From launch to transmission: satellite communication theory and SNG
Published in Jonathan Higgins, Satellite Newsgathering, 2012
This means not interfering with adjacent satellites to the intended one, and therefore the radiation pattern from the antenna has to be accurately defined. Due to the relative difference between the wavelength of satellite frequencies and the typical range of antenna sizes, no parabolic antenna can be manufactured to produce a completely perfect radiation pattern, which would be a single focused beam, but always has a main ‘lobe’ (centered on the boresight) and a number of ‘sidelobes’ radiating out from the antenna, as shown in Figure 2.40. The sidelobes can potentially interfere with adjacent signals on the satellite, and one of the aims of good antenna design is to seek to minimize the sidelobes while maximizing the main lobe. Typically, up to 70% of the signal energy will be on boresight – this is a measure of the efficiency of the antenna. Too much energy in the sidelobes will reduce energy in the main lobe signal and will interfere with signals on adjacent satellites. Hence, the requirement to meet a performance target based on 2° satellite spacing.
A Conformal Phased Array Antenna with Improved Gain on a Cylindrical Surface
Published in IETE Journal of Research, 2023
Mritunjay Dwivedi, Dinesh K. Vishwakarma
As shown in Figure 5 in the broadside direction, θs=0°, we obtain a 25% increase in directivity along with the improvement in beam splitting resulting from 0*DEL when the phase correction of 1*DEL is applied. For a steered beam of θs= −30°, the sidelobe correction is minor but the major lobe has increased by 50%. Sidelobes are a challenging problem when steering the beams and become more prominent in the case of a conformal antenna and hence SLL needs some correction along with the improvement in main lobe directivity.
Antenna Array Pattern Synthesis Using Metaheuristic Algorithms: A Review
Published in IETE Technical Review, 2023
The lobes that are other than the major lobe in the radiation pattern of an antenna are known as side lobe. These lobes represent the unwanted radiation in the undesired direction and may cause interference with other radiating equipment. SLL minimization is essential in order to maximize the energy in the desired direction and reduce any waste of energy.
Optimization method of electronic control parameters of antenna array for null controlling in specific regions and sidelobe suppression
Published in International Journal of Electronics, 2023
Yi Tang, Shutian Liu, Renjing Gao, Mohammad Alibakhshikenari
Null controlling and sidelobe suppression have been paid widespread attention owing to the continuous development of communication services and wireless applications in military and civilian fields [1]. The purpose of antenna-array with null controlling and sidelobe suppression is to control the influences of undesired interference signals and ensure normal signal transmission in the communication channel, meanwhile reducing the peak sidelobe level (PSLL) of the radiation patterns [2]. In order to achieve the null controlling and sidelobe suppression of the arrays, various methods have been proposed to place the nulls in the specific directions and reduce the PSLLs [3-5]. For example, a classical null controlling method was introduced to design the positions of the array elements for the design objective of minimum sidelobe level and null depths [3]. Moreover, a comprehensive study on radiation characteristics of antenna-arrays was proposed to control the single, multiple and broad nulls while the PSLL is effectively suppressed [4]. A pattern synthesis method was proposed for the null controlling and PSLL suppression via rotation and phase optimization [5]. In this work, the depth of dual and multiple nulls was regarded as a constraint to achieve the interference suppression of the arrays in the optimization process. As can be seen from the described above, designing the excitation phases or amplitudes is a common method to suppress the signal interference and improve the radiation performances of array antennas [6-8]. A null synthesis method of an array was proposed to suppress the transmit signal interference by optimizing the phase-only weight vector [6]. Moreover, an optimization method exploiting the phase perturbations in the iterative process to control the depths of the nulls was introduced, and the radiation performances were improved by designing the phase-only of each element [7]. In terms of amplitude-only design, the sidelobe level and null position of hybrid antenna-arrays were controlled and the gain of the radiation patterns was enhanced [8].