A 27-MHz wireless transmitter is fabricated with all the off-chip inductors, capacitors and resistors built on a thin organic substrate. The transmitter module occupies an area of 25mm×25mm. It includes the transistor circuits on a silicon chip and off-chip passive circuits with large-value inductors and capacitors. The newly packaged transmitter module functions properly and gives a 5 dB higher output power while other performances are comparable to that of the counterpart assembled using discrete passive components. It demonstrates the possible system-on-package (SOP) solution of radio-frequency (RF) systems using the embedded passives. IntroductionModern electronic systems have been driven toward further miniaturization and system integration with more functionality but keeping the total system cost and performance more or less the same or even better. This has been prevailing in wireless systems. As the silicon integrated circuit (IC) technology has been very mature in the implementation of digital and analog circuits, the system-onchip (SOC) has been considered as the solution of RF system integration [1]. However, there are passive components in RF circuits that cannot be integrated into the silicon IC chip. The passive components may be either too costly in terms of IC chip area or the RF performance is too poor.The passive components, primarily capacitors and inductors as well as resistors are key circuit elements in RF circuits of wireless systems. Although the discrete passives have been well developed and used to implement RF circuits on printed circuit board (PCB), they have drawbacks in terms of assembly and component counts. This is caused by the individual packages of the discrete passive components which are of bulky size and heavy weight. As a result, the packaging solution using discrete passives complicates the assembly and increases the volume and weight of the packaged systems. Furthermore, the system performance may also be compromised by the uncertain parasitic circuit elements associated with the leaded or SMT discrete passives.Although the system-on-package (SOP) has been considered as the solution of the system integration with optimized performance, including the wireless systems [2-6], few RF circuits using SOP approach have been reported. Nevertheless, only embedded passive technology has been reported and developed for RF systems in the form of individual RF building blocks while almost none of packaged RF transmitter system on a thin organic substrate has so far been reported [7][8][9][10][11][12][13][14][15]. This is especially true for the common consumer electronic circuits operating below gigahertz range.

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