A High-Power Mechanical Switch Connector Design For Base Station Transceiver Units

By Fabien Bourgeas, Vincent Larrey, and Claude Brocheton,
Radiall SA

Abstract
A mechanical switch connector has been developed that achieves the high isolation required for use in cellular infrastructure transceiver units (TRUs). Electromagnetic simulations and experimentation plans were performed on the switch to optimize its isolation. This article describes the performance of multiple preliminary switch concepts, as well as the parameters of the final, successful design.

Introduction
This switch is designed to enable the combination of two independent amplification stages into a common signal output (see Figure 1). However, with this functionality come severe constraints in terms of isolation between outputs in conjunction with a high-power transmission. The performance target for the switch was an isolation of 40 dB up to 3 GHz with an average power of 80 watts and 50 watts, respectively, for the GSM 900 and GSM 1800 bands. While it may be easy enough to find RF mechanical switches with good VSWR values up to 6 GHz on the market, it is much more difficult – indeed impossible – to find products with the rare combination of good isolation and high power.

Figure 1: Application block diagram