An Automatically Assembled Miniaturized SMD Isolator For 1.9ghz Band Communications Systems

Abstract

A miniaturized SMD isolator has been developed for 1.9GHz band communication systems. The dimensions of the isolator are '7x7x3mm (0.15cc) and the weight is 0.50g. By reducing the number of elements and simplifying the structure stacking, assembly has been automated. And a height of 3mm is made possible by stacking some of the elements. The terminals for the surface mount specification are composed of six pieces. Fixed strength of terminals with PCB (printed circuit board) has improved about 40% in comparison with a conventional model being formed four terminals. It is pos:;ible to design the isolator for 1.3GHz by adjusting the capacitance. Selected the capacitors by automatic capacitor sorting machine (ACSM) in a high speed, the assembly time has been cut by about 15%. 1. INTRODUCT~ON three layers of PCB. Two kinds are used, one is for an isolator, and the other for a circulator. The center conductors of each layer have been insulated and oriented at 120" degrees to each other, One end of each conductor is connected to a ground substrate via the through hole and the other end is connected to a capacitor. 100-ohm chip resistors are connected in parallel to divide the power dissipation in order to enable a power rating. For a circulator, they are not used. A resin case with molded copper U0 terminals and ground terminals is used. One end of each terminal is formed in SMD type, the other end is connected with the main substrate. A magnet applies a dc magnetic field to the femte and is located in a hole in the top of the resin case. Simple, stacked element design allows automated assembly. With dense packing, dimensions are reduced to 7x7x3mm(max) and a weight of 0.5g. With the iricrease in mobile communications systems, such as portable telephones, there has been a consequent reduction in size, weight. and cost of these systems. A low cost, low profile isolator suitable for SMD has been developed to satisfy these requiremcnts. A technique for producing a small SMD isolator for 300MHz and 800MHz bands has already been reported'11[21, but none has been produced for the 1.9GHz band. We have automated one of the assembly processes. To cut down the cost of elements and the assembly time, the structure incorporates common elements and processes. With this structure, which makes possible the automation of all the assembly processes, assembly time and cost are halved. This paper describes the construction, design, manufacturing process and performance of the isolator.