Quad-band GSM Silicon PA Module on LTCC embedding a Coupler-based RF Power Controller

Starting from a standard 0.35 mum CMOS process an RF LDMOS based quad band GSM PA on a LTCC substrate has been obtained. The first version, implemented on a FR4 laminate bread board, demonstrates the feasibility of the new RF process option in order to obtain GaAs level performances, in terms of RF output power and efficiency, at a fraction of the cost. Moreover the new compact size RF LDMOSFET together with spiral inductors and MIM capacitors allows a space saving substrate package layout and avoids designing complex and critical microstrip power combiner or baluns. Then a second version has been implemented on 8times8 mm² LTCC multi layer substrate. The possibility to design and integrate vertically stacked high quality factor inductor and capacitor, compensate the poor Q factor of the passive devices integrated on silicon. Furthermore the higher dielectric permittivity and the lower dielectric loss other than reducing the trace width allow the integration of a power controller circuit based on two embedded directional couplers plus a diplexer filter feeding the RF input of a commercial power controller IC. The GSM850-GSM900 PA shows 34 dBm of Pout and 50% PAE, while the DCS-PCS PA results in 32 dBm of Pout and 47% of PAE at a 3.5 V supply voltage.