An Ultraminiature Switch Connector for Testing Wireless Equipment
Murata Electronics North America
Smyrna, GA
Embedding test points in today's miniature RF circuit boards has traditionally been a problem because of the amount of PCB space required and the intrusive effects to the circuit's performance. The benefits of having these RF test points always seem to give way to their disadvantages. A new ultra-miniature switch connector has been developed that all but eliminates these disadvantages and now provides miniature, low cost test points in compact RF PCBs that have little or no effect on circuit performance.
The model SWD switch connector system is composed of an ultraminiature, surface-mountable receptacle measuring 3 mm square with an integrated mechanical switching function and a choice of test probe adapters. The switch connector/test probe combination features a frequency range of DC to 6 GHz, an impedance of 50 
and an in-circuit insertion loss of 0.1 dB (max) (without the measurement adapter). Figure 1 shows the switch connector's simplified operation.
The switch receptacle is designed for surface mounting and as such may be mounted in line with the circuit board traces using reflow soldering techniques. Its small size makes it easy to incorporate and its high reliability poses little risk to overall circuit performance. In addition, the SWD receptacle is very low cost so as not to burden the total circuit's bill of material and manufacturing costs.
Table 1 lists the SWD system's performance specifications. Figure 2 shows the system's insertion loss, SWR (switch on) and isolation (switch off) vs. frequency. In addition, there is a ±0.7 mm offset tolerance for the test probe adapter to make suitable electrical contact due to the self-centering mechanical design of the receptacle. Figure 3 shows the receptacle's mechanical construction.
The SWD system is designed for use in testing wireless equipment primarily designed to operate from DC to 6 GHz. Its characteristics make it a good fit for portable applications, such as cellular phones, two-way pagers and wireless modems. As an example, the SWD system facilitates automatic RF measurements in production by positioning the switch connector receptacle between the antenna and the front-end filter. The easy-to-use connect/disconnect feature makes the test probe system ideal for troubleshooting RF circuit performance problems or performing automated system checks in a high speed measurement process.
SWD switch connector receptacles are available on tape and reel and sell for $0.55 to $0.45 in quantities of 10,000 to 25,000. A variety of test probe adapters are available. More information may be obtained from the company's Web site at www.murata.com.
Murata Electronics North America,
Smyrna, GA (770) 433-5782.