A broadband directional coupler based on ferrite cores

Abstract

A broadband directional coupler based on ferrite cores is proposed for high frequency (HF)/Very high frequency (VHF)/Ultra High Frequency (UHF) communication systems. The transformer-type coupler is composed of two double-aperture ferrite cores and 1-mm-diameter strands. The ferrite cores with different relative permeabilities are screened to achieve an ultra-wide bandwidth (5-1000 MHz). The coupler demonstrates excellent electric performances. The voltage standing wave ratio of each port is less than 1.2, a stable −20 dB coupling level is maintained over the operating bandwidth and the insertion loss is less than 0.8 dB. Such couplers have compact sizes and are of very low cost.