A multiband power amplifier with a tunable transmission line for mobile LTE applications

Abstract

A power amplifier (PA) for multiband applications implemented with a tunable load modulation technique is presented. The broadband output matching can be done by load modulation implemented by modification of the characteristic impedance (Z C ) of the tunable transmission line. The multiband PA delivered a gain of more than 10.5 dB, an adjacent-channel-leakage ratio of evolved UMTS terrestrial radio access adjacent channel leakage ratio (E-UTRA) lower than 230 dBc, and a power added efficiency of 28-31% at the output power of 26-dBm and the frequency range of 1.5-2.05 GHz with a 10-MHz 16QAM long-term evolution signal.ABSTRACT: Two novel cascaded microstrip open-loop resonators with loading varactors are presented to design tunable filter. In two coupled resonators, the coupled sides can provide both electrical and magnetic coupling. A capacitance loaded at input/output feed line is used to control the external quality. By adjusting the parameters of coupling side and the value of the capacitance, coupling coefficients and external quality can be tuned to meet the requirement of constant absolute bandwidth. A two-pole filter is demonstrated a tuning range from 607 to 942 MHz with the insertion loss 2.5-3.2 dB. Especially, the 3-dB bandwidth is approximately 63 6 7 MHz with the center frequency from 642 to 942 MHz.

A Multiband Power Amplifier With a Reconfigurable Output-Matching Network for 10-MHz BW LTE Mobile Phone Applications

“…3(b) shows the S-parameters of the MBPA for low-band operation (SW on) for different Z L values. Note that the TTL can be tuned to the frequency where the second harmonic rejection takes place (between 1.6 and 1.9 GHz) by adjusting variable parameters of the TTL including characteristic impedance (Zc) and electrical length (θ) using varactor diodes [9], [11]. The TTL plays the role of a shunt resonator for the second harmonic rejection and its resonance frequency can be tuned from 1.6 to 1.9 GHz.…”

“…However, it also needs an output matching network implemented with distributed components including a λ/4 transmission line. Recently, an MBPA utilizing a tunable transmission line (TTL) for load impedance modulation was reported [9]. However, the load modulation by the TTL was effective only in the limited frequency range of 1.5−1.85 GHz.…”