Practical modeling and de-embedding procedure for matching circuit of triple band front-end module used for EGSM/DCS/PCS cellular phone system

Abstract

Integration of the antenna front-end module is improved using balanced SAW technology and LTCC technology with sophisticated 3D electromagnetic simulation techniques. New SAW front-end modules for use in EGSM/DCS/PCS triple-band cellular phones have been developed. Conventional RF section designs utilize matching circuits between the front-end module and the RF-IC, which has a complex load impedance. Our new concept front-end module includes the matching circuit for size reduction. Due to the internal matching circuit, the front-end modules are no longer standard 50 ohm system devices. We have demonstrated a practical modeling and de-embedding procedure for the internal RF-IC matching circuit. With this technique, we can evaluate SAW filter characteristics, such as insertion loss, VSWR and amplitude/phase balance, in the nominal output impedance of the SAW filter (e.g.,150 ohm balance) in spite of complex output impedance values for the front-end modules. This modeling technique is useful, not only for inspection of SAW filters for front-end modules, but also for investigating yield problems due to component variations in matching circuits. We believe this technique is useful for developing new concept front-end modules that include matching circuits for the RF-IC.