A Passive Front End of Radio Transceivers for LTE Bands

Abstract

ABSTRACT Software defined radio implementation is required for LTE radio transceivers. An SDR consists of an rf front end and a digital processor platform DSP. This paper is devoted to the design and implementation of the passive part of the front end; the antennas and bandpass filters. It presents the design of two microstrip patch antennas and a third order parallel coupled band pass filter with defected ground structure that can be used in cellular communication applications, especially in LTE . The two antennas cover LTE network bands 1, 2, 3, 4, 9, 10, 23, 25, 33, 34, 35, 36, 37, and 39[1]. The antennas and filter were printed using FR-4 substrate material with dielectric constant of ɛ r =4.4, thickness of h = 1.6 mm and loss tangent tan δ = 0.025. The overall dimensions of the first antenna is 39 mm * 37mm * 1.6 mm with 50 Ω impedance. This antenna operates between 1666 MHz and 2239.5MHz for return loss of less than - 6 dB and covers LTE network bands 1, 2, 3, 4, 9, 10, 23, 25, 33, 34, 35, 36, 37, and 39. The simulation results suggest that the antenna gain and directivity value are 1.7dB and 2.5 dBi with omnidirectional radiation pattern. The overall dimension of the second antenna is 25 mm * 21mm * 1.6 mm with 50 Ω impedance. This antenna operates between 1896MHz and 2015.8MHz for return loss of less than - 6dB and covers LTE network bands 1, 2, 25, 33, 36, and 37. The simulation results suggest that the antenna gain and directivity value are 1.4dB and 1.7dBi with omnidirectional radiation pattern. The parallel coupled filter with over all dimensions of 45 mm * 25 mm achieves centers frequency of 1.95 GHz and band width of 80 MHz and covers LTE network bands 36 or 1. The order of the proposed band pass filter is three and three defected ground structure are used. The devices are analyzed using Computer Simulation technology (CST) and Zeland IE3D. They are fabricated with photolithographic techniques and their scattering parameters are measured by using Vector Network Analyzer (VNA) E8719A. Measurements and simulations show good agreement.