Characterization and Optimization of a Collinear Array of Circularly Polarized Side-Mounted Elements

This paper presents the radiation characteristics of a two-element collinear array of shunt-fed, slanted dipoles side-mounted to a metallic tower. It presents the radiation characteristics of the array as commonly implemented by FM broadcasters and suggests methods on how to optimize these characteristics such as the power gain, pattern circularity, side-lobe reduction, and horizontal-vertical polarization component ratio for the array to better conform to broadcast standards. By determining these characteristics using an advance antenna simulation software, optimization variables are identified, and their optimized values are determined. The optimized values lead to improved radiation characteristics of the array in conforming with broadcast requirements. Results show that adjusting the distance between the dipoles to less than one wavelength reduces the sidelobe of the array radiation pattern; varying the dipole physical specifications improves the polarization component ratio and the circularity of the radiation pattern. However, varying the dipole specifications also reduces the gain of the array. For applications requiring higher gains, other methods of realizing high collinear array gains are recommended

Optimizing the coverage of FM broadcast station by radiation pattern shaping

This paper describes how to configure the radiation pattern of an omnidirectional FM antenna to at least approximate a desired directional radiation pattern. The desired radiation pattern is based on the population location within the coverage area of an FM radio station. In this way, the station will transmit signal only in directions where the signal is needed, thereby the station\u27s transmitter will be operating at much reduced power. A linear uniform antenna array is used to produce the customized radiation pattern on the horizontal plane. The array is composed of two basic identical omnidirectional antennas, each is called a bay. By determining the proper distance and phase relationship of the two identical basic antennas, any radiation pattern can be realized. Genetic algorithm (GA) is used in optimizing the values of the distance and the phase relationship of the two bays in linear array, producing an optimized radiation pattern identical to the desired radiation pattern. Genetic Algorithm is implemented in Matlab. Optimum values of the GA parameters are first determined prior to the optimization of the radiation pattern for a more accurate, consistent and faster results. Two directional patterns are presented to demonstrate the method. Finally, an antenna simulation software is used to validate the results in each case

Radiation characteristics of patterns derived from shunt-fed slanted dipole linear arrays

The radiation characteristics of three directional radiation patterns derived from a two-bay horizontal uniform linear array are presented for FM broadcast applications. The bays in the array are the commonly-used shunt-fed, slanted dipoles. Two control factors, distance and phase, are used to shape the patterns. The variation of bay distance and phase without the use of sophisticated and expensive equipment makes the array implementation simple. The theoretical electric field patterns are presented. The horizontally and vertically polarized (H-pol and V-pol) components of the electric field are described together with the power densities created along the horizon. A discussion on the gain characteristics of each pattern as well as the array impedance over the entire FM broadcast band are likewise presented. Based on the computations, the directional patterns produced by the two-bay uniform linear array have maximum gains that are greater than the gain derived from four-bay collinear arrays. The resulting directional patterns also have greater beam widths; no side lobes and pattern nulls are present. Although only the distance and phase control factors are used to shape the pattern of the two-bay linear array, several useful patterns for FM broadcast applications are realized that find practical applications in FM broadcasting. © 2016 Praise Worthy Prize S.r.l. - All rights reserved

The compliance to broadcast standards of a side-mounted circularly polarized antenna

Non-directional antenna bays in FM broadcast applications were designed to exhibit radiation characteristics that conform to broadcast standards. However, the metallic tower where these antennas are mounted and secured is not considered during the development process. Knowing that the radiation characteristics of antennas are affected by the metallic tower, it is the aim of this paper to present the compliance of the side-mounted Circularly Polarized Antenna (CPA) to broadcast standards. The CPA compliance to requirements on polarization components, pattern circularity and bandwidth is specifically presented. Results of numerical analyses using an advanced antenna simulation software show that the radiation characteristics of the CPA are severely altered by the presence of the tower and thus impairing its capacity to adhere to the said broadcast requirements. Some adjustments on the CPA structure are needed to improve its performance. © 2018 Praise Worthy Prize S.r.l.-All rights reserved

Simplified and systematic design of a solid-state FM stereo transmitter

The study deals with the design and construction of a solid-state FM stereo broadcast transmitter. The whole system is divided into four (4) major parts, namely: the modulator, the stereogenerator, the power amplifier and the power combiner.A prototype of the transmitter is constructed and its performance is evaluated based on the electrical performance evaluation standard set by the National Telecommunications Commission (NTC) and the Kapisanan ng mga Brodkaster sa Pilipinas (KBP). The evaluation is carried out using existing and available instruments and equipment.The result of the performance evaluation revealed that the prototype met the specifications required of an FM broadcast transmitter.The prototype is therefore fitted to be used in actual broadcast operations. With a power output of 30 w, the prototype can be used as a low power broadcast transmitter.Aside from the performance evaluation, a comparative cost analysis is made based on the cost of RFpower produced by the prototype and a local-made vacuum tube transmitter

Reducing FM broadcast energy consumption using directional radiation pattern

Much energy is saved in the daily operation of FM broadcast stations if the transmitting antenna system employed transmits RF signal only in directions where the signal is wanted. Most FM broadcasters employ antenna systems that radiate equally in all directions or having an omnidirectional pattern on the horizontal plane. In most cities where broadcast stations operate, the target population is located only in some directions from the antenna location and definitely not around it. The use of correct radiation patterns in FM broadcasting is very important to assure that every RF energy emitted by the transmitter is received only within the target areas and not to be wasted in directions where the signal is not needed. This paper presents a method of producing directional patterns that are suitable for FM broadcast applications with simple implementation. These patterns are shaped by varying the physical distance and the phase relationship of two basic antennas called bays in uniform linear array. The bay used in the array is the shunt-fed, slanted dipole commonly used in FM broadcasting. Computer simulations show that the patterns presented in this paper have sufficient gains in certain directions, greater beamwidth and sidelobe-free. Though only two control factors are used in shaping the radiation pattern of the array, several patterns can still be produced that find practical applications in FM broadcasting. © 2006-2015 Asian Research Publishing Network (ARPN)

Frequency selection and control of FM broadcast transmitters using a two-modulus prescaler

A technique and a system are presented and described that offer simple, economical and convenient method f stabilizing and programming the carrier frequency of an FM broadcast transmitter. The system employs the common phase locked loop method of frequency programming and control but uses a two-modulus prescaler instead of a fixed modulus prescaler as part of the counter divider section contained in the feedback loop. With the use of the two modulus prescaler , frequency programming is easy for a transmitter to operate at a particular frequency anywhere between 88.1 MHz to 107.9 MHz using only one reference frequency. The system described here has a resolution (channel separation) of 50 kHz instead of the ideal 200 kHz. The carrier frequency stability is good and satisfies the standard stability and other frequency related requirements stated in the KBP (Kapisanan ng mga Brodkaster sa Pilipinas) Technical Standards and Operating Requirements for Broadcast Stations in the Philippines

Customized directional patterns for FM broadcast using uniform linear array of optimized shunt-fed slanted dipoles

Much-energy is saved in the daily operation of FM broadcast stations if the transmitting antenna system emp0loyed transmits RF signal only in directions where it is needed. Antenna manufacturers make use of the trial-and-error method of adding parasitic elements when a particular pattern is desired by a particular customer. This paper presents a simple method of broadcast. The proposed method makes use of two modified shunt-fed slanted dipoles forming a uniform linear array. The modified dipole is optimized to exhibit a circular pattern even in the control factors: the physical distance and the electrical distance between the two dipoles. These factors are easy to determine and easier to implement than the present method of pattern shaping enough gain with the absence of pattern nulls and minor lobes that are common in high gain antenna systems used by most broadcasters

Radiation pattern shaping for FM broadcast-optimizing coverage

This paper describes how to configure the radiation pattern of an omnidirectional FM antenna to at least approximate a desired directional radiation pattern. The desired radiation pattern is based on the population location within the coverage area of an FM radio station. In this way, the station will transmit signal only in directions where the signal is needed, thereby the station\u27s transmitter will be operating at much reduced power. A linear uniform antenna array is used to produce the customized radiation pattern on the horizontal plane. The array is composed of two basic identical omnidirectional antennas, each is called a bay. By determining the proper distance and phase relationship of the two identical basic antennas, any radiation pattern can be realized. Genetic algorithm (GA) is used in optimizing the values of the distance and the phase relationship of the two bays in linear array, producing an optimized radiation pattern identical to the desired radiation pattern. Genetic Algorithm is implemented in Matlab. Optimum values of the GA parameters are first determined prior to the optimization of the radiation pattern for a more accurate, consistent and faster results. Two directional patterns are presented to demonstrate the method. Finally, an antenna simulation software is used to validate the results in each case. ©2010 IEEE