Broadband microwave push-pull power amplifiers in liquid crystal polymer modules

In this Ph.D. research we present the development of broadband 6-18 GHz push-pull power amplifier (PA) modules implemented with the liquid crystal polymer (LCP) packaging/substrate material. The main focus is to achieve a broadband > 20 dB improvement in the suppression of 2nd-order distortions up to their 1 dB compression point (P1dB). The total P1dB output power for the module is to be twice of that for each single-ended PA. The single-ended PAs used are Fairchild RMPA61810 MMICs fabricated in 0.25 mum GaAs pHEMT technology. These push-pull PAs are the first to achieve both high output power and broadband even-order distortion cancellation.;For single-ended amplifiers having more than an octave of bandwidth, their output 2nd-order harmonic distortion (HD2) and intermodulation distortion products (IMD2) can fall inside the passband, and cannot be filtered. However, when power combined with the push-pull architecture, it is possible to cancel out these 2nd-order distortion products. The amount of achievable cancellation (suppression) is limited by the amount of balance of a push-pull amplifier.;In order to achieve maximum cancellation, baluns employed within the module need to have a minimum amount of imbalance. We propose two novel solutions in this research in order to improve other key performances of a balun, while simultaneously maintaining minimum imbalance. A twin dielectric thin-film thickness structure has been developed specifically to reduce a baluns' insertion loss, without having to sacrifice its bandwidth. A prototype balun with such structure has been fabricated with BCB dielectric thin-films, and has been measured to provide an amplitude imbalance of < 0.5 dB, phase imbalance of < 6°, and an insertion loss of < 0.7 dB, all across a bandwidth of 4 to 20 GHz. On the other hand, a novel broadband even-mode matching network (EMMN) has been devised to specifically improve the return losses of and isolation beween the balanced ports. A balun with EMMN has been fabricated in a multi-layered LCP flex, and measured to have > 15 dB return losses and > 12 dB of isolation for the balanced ports, across a 6 to 18 GHz bandwidth. Baluns with low insertion losses and good return losses help improve a push-pull PA's gain; whereas high balanced ports isolation help improve the amplifier's stability. We have also derived theoretical explanations for the origins of imbalances of coupled microstrip lines planar baluns.;Baluns are designed and integrated into the LCP substrate as embedded passive devices. Technical challenges and processing procedures for firstly developing broadband baluns in LCP are discussed in details. The LCP material is chosen for the implementation of the module as it provides the benefits of being near hermetic, light weight, low cost, and with available thin-film laminates suitable for the implementation of broadband baluns.;We also present in this dissertation extensive distortion measurement results of the broadband push-pull PA modules. The goal of a broadband > 20 dB improvement in distortion level suppression has been achieved and verified through our experiments. For a single-ended PA, measured in-band 2nd-order distortion levels are -20 dBc (decibels relative to carrier) at P 1dB; for the push-pull PA, output HD2 and IMD2 levels have been measured to be lower than -40 dBc. Output distoriton levels are characterized for the PAs from 12 to 36 GHz. These distortion levels for the push-pull module are also well suppressed when driven deep into the saturation region, up to the 6 dB compression point (P6dB).