# A Low-Cost Printed Log-Periodic Dipole Array for DVB-T2 Digital TV Applications
## 1 Introduction  
In the last two decades, analog broadcasting has been progressively replaced by digital modulation, which allows the use of advanced video compression techniques for terrestrial TV, resulting in a significant increase in the quality of the transmitted video signal, also improving the allocation efficiency of the frequency spectrum. Digital TV (DTV) offers the final user a high data rate transmission, it provides interactive services, and it is able to operate at lower power compared to analog TV. The DTV operates in the UHF band, from Channel 21 to Channel 69 (470 MHz-860 MHz) [1], and, being a broadcast service, it is employed by a large user base. Therefore, the rapid evolution of the digital TV calls for high-performance, broadband, and low-cost antennas working in the lowest part of the UHF band. Log-Periodic Dipole Arrays (LPDAs) have been the most common and widespread antennas used for TV signal reception since their first introduction in the 1960s [2], thanks to their wideband properties and flat gain within their operating frequency band and they are still considered one of the best solutions for all applications that require a broadband behavior and a stable gain [3, 4]. Wire LPDAs using cylindrical dipoles as radiating elements were proposed by [PERSON] in 1957 [5] and are still extensively used as wideband antennas. They can be designed with a bandwidth up to a decade, with a typical gain of around 10 dBi in air [6], and can be used at VHF and UHF frequencies, with a standard and cost-effective technology. Standard wire LPDAs can be designed following [PERSON]'s guidelines [7] and can be fabricated relying on relatively low-cost procedures. However, the main advantages of wire LPDAs are lost in the SHF band, where the dipoles become so short and tiny that they can be created only by specialized technologies [8]. On the other hand, printedLPDAs are a common choice for applications in the SHF band and beyond, due to their low production cost, size, and weight. Printed LPDAs can be miniaturized using suitable dielectric substrates since the resonant length of the printed dipoles must be equal to half a wavelength in the dielectric substrate. This feature of printed LPDAs can also be exploited to design a compact and low-cost printed LPDA at UHF frequencies, as we performed in this paper. A further miniaturization can be easily achieved in printed LPDAs by suitably meandering the radiating dipoles, leading to a designed antenna with a reduced size, especially compared with the corresponding wire antenna working in the same frequency band. The typical size of wire log-periodic dipole arrays that cover the frequency band of analog TV is almost 1 square meter, and the operating bandwidth spans from 300 MHz to 1 GHz. Therefore, such wire LPDAs could be cumbersome in the DTV-UHF frequency band [9; 10], but their size can be reduced by employing printed LPDAs, which exploit planar technology to reduce the dipole length. Since the dipole arms of such LPDAs are printed on the opposite sides of a dielectric substrate, the geometrical parameters of such an antenna cannot be computed in the same way as a standard wire LPDA [7]. In particular, the length of the longest dipole must be computed by considering the dielectric substrate parameters [11], and then the rest of the dipoles can be designed following Carrel [7], choosing first the optimal values for the log-period \(\tau\) and the spacing factor \(\sigma\), and then obtaining the necessary number of dipoles to cover the requested frequency band. The dielectric substrate of the printed LPDA for DTV applications must be as cheap as possible since the antenna size is relatively large to cover the requested UHF bandwidth; therefore, the best choice is an FR4 substrate, which has a dielectric permittivity of around 4.3, guaranteeing a moderate size reduction at a low cost. A further size reduction can be achieved using one of the many techniques proposed in the literature for reducing the size of an LPDA [12].