High Power GaAs MMIC Chipsets for 18 to 32 GHz Frequency Band Applications

Abstract

Recent commercial wireless applications such as Point to Point radio links, LMDS (Local Multipoint Distribution Service), LMCS (Local multi-point Communications Service) and Commercial K-Band Satellite based services have spurred significant activity in development of mmWave power amplifiers. These applications lie in the frequency range of 18 to 42GHz with possible future extensions to 60GHz. These systems employ digital modulation schemes for which highly linear mmWave power amplifiers are essential. This paper presents an overview of some chipsets consisting of High Power amplifiers covering the frequency range of 18 to 32GHz. Preferred solutions to a low cost subsystem vary from one subsystem manufacturer to another as it involves assembly and test capabilities in addition to component costs. The overall direction appears to be toward multi-chip module assemblies. Here, both chip and packaged level component options are considered. SUMMARYThe transmitter section in a radio, such as a Point to Point and LMDS radio, requires the integration of several chips such as pre-driver, driver and output stages with desirable functions such as of on-chip power detection. The data modulation schemes are mostly digital, such as QPSK and QAM, which demand very stringent linearity specifications at system level to ensure the quality of the signal. This translates to the need for developing higher output power modules, providing for increased power consumption, more complex MMIC chip assemblies ..etc. The most important frequency bands of the point to point and LMDS radio links applications are 18, 23, 26, 29, 31 and 38 GHz. To achieve the high power level required by the mmWave radio link applications, a 0.25µm Power pHEMT technology has been used in the MMICs development [1]. To cover most of the frequency bands involved, we developed an 18 to 32GHz broadband driver amplifier, FMM5804. The MMIC has 18dB of gain, 23 dBm of output power and is fully matched [2]. The photograph of the MMIC is shown in Figure 1. Good return loss and broadband stability make this amplifier easy to integrate in a multi-chip environment.