Low-pass Active Filter Enabling DVB-H/T and GSM Standard Coexistence

This paper deals with the design of a novel UHF band low-pass active filter aiming to allow the coexistence in a single terminal of the respective standards, DVB-H/T for digital TV reception and GSM for cellular telephony. The filter concept is based on a common 11-pole generalized Chebyshev low-pass network suitably modified to isolate the standard bands. The approach consists in adding only a single negative resistance in the network in order to compensate for the overall losses near the cut-off frequency and enhance the selectivity of the filter. Key parameters as stability, noise factor, linearity and power consumption have been considered in the design of this active filter. Also, experimental prototypes based on conventional discrete surface mount components and assembled on a FR4 substrate have been built up in order to prove this new concept.