Design analysis of integrated passive device-based balun devices with high selectivity for mobile application

Abstract

This paper presents highly selective, low-loss, and miniaturized balun devices fabricated using the integrated passive device (IPD) technique for the GSM band (900/1800 MHz) and the WiFi band (2400 MHz) in mobile applications. Balun devices were fabricated on a gallium arsenide (GaAs) substrate using the IPD fabrication process to reduce the overall size (0.05 λg × 0.036 λg at 900 MHz). Each device is the combination of lattice lumped structure with a low-pass filter and a high-pass filter configuration. This structural formation of lumped elements helps to reduce the phase mismatch error in the balun devices. For all the balun devices, the measured results indicated a minimum amplitude imbalance (<0.47 dB) and low phase imbalance (180 ± 2.6°). Mathematically calculated, calculated after considering parasitic effects, simulated and measured results exhibited a good correlation. The return loss is below 18 dB and insertion loss is below 0.25 dB for the entire fabricated devices. A balun device with a center frequency of 900 MHz has given the best results amongst all fabricated devices.