In this letter, a new moment method using helical segments is presented to model Normal Mode Helical Antenna (NMHA). Using this method, the NMHA can be modeled by a few segments. The current distributions and radiatio...In this letter, a new moment method using helical segments is presented to model Normal Mode Helical Antenna (NMHA). Using this method, the NMHA can be modeled by a few segments. The current distributions and radiation patterns of some NMHAs are calculated.A comparison is made between results obtained using this helical segment algorithm and a linear segment algorithm, and the results of the two algorithms agree fairly well. When calculating the impedance matrix [Z], all the elements of the matrix can be obtained by only calculating a few elements with the application of the symmetric and periodic characteristics of the NMHA.Therefore, the CPU time and the memory storage are significantly reduced, with the accuracy and speed enhanced.展开更多
The physical size of an antenna becomes an important characteristic when receiving signals in bands with long wavelengths. Size determines two important aspects of antenna performance;impedance and efficiency. For exa...The physical size of an antenna becomes an important characteristic when receiving signals in bands with long wavelengths. Size determines two important aspects of antenna performance;impedance and efficiency. For example, the VHF antennas installed on radio sets that intended to receive FM or the latest technology Digital Audio Broadcasting (DAB) radio signals in Bands II, III respectively. Antennas that are installed on mobile platforms (i.e. portable receivers) require a receiver that utilizes a whip telescopic antenna with adjustable length which can operate as a λ/4 monopole antenna. Whereas, non-portable applications like a deck commercial receiver has no built in antenna due to the large size of the radiator needed and so must be connected with an external antenna. This paper presents a new design of a very small size Normal Mode Multiloop Helical Antenna (NMMHA) with superior performance developed for commercial receivers operate in band II, III. The major drawback which has been overcome with this design is the very narrow bandwidth of the Normal Mode Helical Antenna, which originally was optimized to provide the minimum Voltage Standing Wave Ratio VSWR response across Band II (87.5 - 108 MHz). The NMMHA’s size allows it to be a build in block of a deck commercial receiver.展开更多
The antenna is a receiver’s component that collects electromagnetic waves from various directions. The rationale behind focusing on the circular array is that its tuning ensures that the receiver processes the desire...The antenna is a receiver’s component that collects electromagnetic waves from various directions. The rationale behind focusing on the circular array is that its tuning ensures that the receiver processes the desired signal only, while rejecting the unwanted interference. This can only be achieved by a directional external antenna that is large in size and must be steered mechanically in the desired direction. As this arrangement is not practical, smart antennae have been proposed as an alternative. A circular phased array can produce a predicted radiation pattern, whereby it receives maximum energy from the desired direction without the need for mechanical control. Owing to these characteristics, phased arrays exhibit high gain as well as immunity to interference, making them ideal for use in high interference environments. This combination would ensure that it could be incorporated into a commercial deck receiver or installed on vehicles.展开更多
文摘In this letter, a new moment method using helical segments is presented to model Normal Mode Helical Antenna (NMHA). Using this method, the NMHA can be modeled by a few segments. The current distributions and radiation patterns of some NMHAs are calculated.A comparison is made between results obtained using this helical segment algorithm and a linear segment algorithm, and the results of the two algorithms agree fairly well. When calculating the impedance matrix [Z], all the elements of the matrix can be obtained by only calculating a few elements with the application of the symmetric and periodic characteristics of the NMHA.Therefore, the CPU time and the memory storage are significantly reduced, with the accuracy and speed enhanced.
文摘The physical size of an antenna becomes an important characteristic when receiving signals in bands with long wavelengths. Size determines two important aspects of antenna performance;impedance and efficiency. For example, the VHF antennas installed on radio sets that intended to receive FM or the latest technology Digital Audio Broadcasting (DAB) radio signals in Bands II, III respectively. Antennas that are installed on mobile platforms (i.e. portable receivers) require a receiver that utilizes a whip telescopic antenna with adjustable length which can operate as a λ/4 monopole antenna. Whereas, non-portable applications like a deck commercial receiver has no built in antenna due to the large size of the radiator needed and so must be connected with an external antenna. This paper presents a new design of a very small size Normal Mode Multiloop Helical Antenna (NMMHA) with superior performance developed for commercial receivers operate in band II, III. The major drawback which has been overcome with this design is the very narrow bandwidth of the Normal Mode Helical Antenna, which originally was optimized to provide the minimum Voltage Standing Wave Ratio VSWR response across Band II (87.5 - 108 MHz). The NMMHA’s size allows it to be a build in block of a deck commercial receiver.
文摘The antenna is a receiver’s component that collects electromagnetic waves from various directions. The rationale behind focusing on the circular array is that its tuning ensures that the receiver processes the desired signal only, while rejecting the unwanted interference. This can only be achieved by a directional external antenna that is large in size and must be steered mechanically in the desired direction. As this arrangement is not practical, smart antennae have been proposed as an alternative. A circular phased array can produce a predicted radiation pattern, whereby it receives maximum energy from the desired direction without the need for mechanical control. Owing to these characteristics, phased arrays exhibit high gain as well as immunity to interference, making them ideal for use in high interference environments. This combination would ensure that it could be incorporated into a commercial deck receiver or installed on vehicles.
