Microwave Engineering Europe March 2000 Cover story Our cover shows one of Ericsson Microelectronics' recent LDMOS introductions, a 70W device aimed at GSM applications. More detail is on page 15. We also feature linearisation and device characterisation for power amplifiers on pages 45 and 52. IF RIP It's a theme that we've featured in Microwave Engineering Europe over a number of years, but the demise of the intermediate frequency in high-volume commercial receivers does look to be firmly on the horizon. The superhet receiver has certainly served us all well over the years and, despite the cellular handset industry's moves to let it rest in peace, the direct conversion or zero IF alternative is not going to replace superhet in the vast majority of designs. However, the change for those cellular handset designs and other high volume applications such as satellite television receivers could be dramatic, and indicates just how much the design philosophy for RF circuits has moved on. The direct conversion receivers now being discussed or openly offered as products by companies like Infineon, Ericsson, Analog Devices, Philips, Alcatel and Texas Instruments, are all highly integrated silicon circuits. The savings from losing the intermediate stages and the added DC problems resulting from the architecture really only make sense if the products are highly integrated and the volume is there too. Filtering is still required, albeit in the digital domain, so there is a need for advanced digital signal processing to sort everything out after analogue to digital conversion. Will the adoption of direct conversion receivers have a more widespread impact on our industry? We think it has already fundamentally changed the previously accepted wisdom that zero IF was tomorrow's technology and probably always would be. You can judge for yourself by reading this month's issue - see pages 17 to 27. The other theme which has cropped up in this issue, in a rather less formally planned way than RF transceivers, is power amplifiers. LDMOS has become established as the most significant power technology of the moment and we report this month on Ericsson's increased levels of automation in the production of power transistors and the expansion of the company's facilities in California to cope with a doubling in demand for devices. Power transistors have largely been hand-crafted in the past and the increased automation is certainly interesting to watch first hand, encompassing automated alignment and wire bonding. Placement of the die in the package is still very much a handcrafted exercise. Those changes are happening in Morgan Hill, California, the head office for Ericsson's RF Power activity and notable that the silicon foundry in Kista, near Stockholm is now managed from Morgan Hill, such is the nature of international companies. LDMOS and power amplifier linearisation feature on pages 15, 45 and 52. Paul Jackson

Contents In focus Infineon VP backs direct conversion and MEMS for an integrated future; Ericsson joins moves to direct conversion receivers Focus on Frequency conversion Front end conversion takes direct route; Triple mode transmitter trims component count; Mixers maximise multilayer material Characterization of discontinuity effects in single ridge waveguide A canonical topology of a step discontinuity at the junction of two waveguides is a shunt susceptance in cascade with an ideal transformer. The object of this paper is to provide some experimental data on the element values of such a step between standard and a single ridge waveguides. Professor Joe Helszajn from Apollo Microwaves, show that the resonant frequency of the test piece is in excellent agreement with that calculated using the mode matching method (MMM)d Ltd, describes the use of miniature digital potentiometers in a power amplifier. Using digital potentiometers in commercial RF power amplifier applications Linearisation techniques for power amplifiers require control components. In this paper Gareth Lloyd of Efficient, Linear & Broadband Ltd, describes the use of miniature digital potentiometers in a power amplifier. GSM/EDGE: device characterization for RF power amplifier Designers of basestation radios for the next generations of cellular systems (2G+, 3G) need to trade-off between spectral efficiency, power and linearity. This paper summarises the differences between GSM and EDGE specifications and reports on LDMOS device characterisation under EDGE signals. The authors are Pascal Gola and Jean-Christophe Nanan of Motorola Toulouse. Sommaire d'articles Zusammenfassung der Artikel New Products and Data Calendar Classified Catalogue Update & Appointments