Tunable multiband power amplifier using thin-film BST varactors for 4G handheld applications

Abstract

A new methodology for multiband tunable power amplifiers (PA) using barium-strontium-titanate (BST) varactors is presented. A prototype tunable power amplifier has been developed and its performance is evaluated in context of the upcoming 4G scenario which demands for multimode/multiband power amplifiers capable of operating over multiple frequency bands. The tunable PA requires two tuning voltages at the output matching network as well as an additional tuning voltage for a novel tunable 2 nd harmonic termination. The PA is continuously tunable from 1700 to 2300 MHz, covering multiple bands. Tunable PA measurements with LTE signals show a maximum gain of 27dB with Pmax of 24.1dBm and an EVM of 6% using BST varactors having Q-factors not more then 30 at sub-2GHz frequencies.Index Terms -Tunable, Multiband power amplifier, BST varactors, 4G.

A single chip multiband power amplifier using active load modulation techniques

“…2(a)) without the ALM network (switch off) at each frequency. Z 2 shows the almost constant load line for MBPAs with the ALM network (switch on) as in (1). If the electrical length, θ, of the transmission line in ALM network is fixed to 99 degree due to the physical limitations, the load impedance modulation can be successful with variable α and Z T as shown in Table I.…”

“…In particular as for the power amplifiers, maintaining the constant load line over the frequency bands has been a key element for single chip multiband PA operations. To keep the same or similar load line over the frequency bands, tunable elements, MEMS technology or switching architectures have been used at the output matching networks, where there are some drawbacks such as higher insertion loss, frequency limitations due to the tuning range of the capacitors, larger chip area and even additional chips for controlling the load lines [1][2][3]. In this paper, we propose an active load modulation (ALM) technique to control the load line for the power amplifier as in Doherty PAs [4][5].…”

Improving 3G/4G receiver sensitivity (TIS) using antenna impedance matching networks

“…In order to match the antenna over a wide frequency range, two different methods have been proposed and used: a) a CLC (fixed inductor and two variable capacitors) antenna matching network between the antenna and the PAIS witch network, and b) antenna aperture tuning where the antenna resonant impedance is changed using a switched capacitor connected inside the antenna [1][2][3][4][5]. Both methods have their advantages.…”