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Modern analog circuits are heavily dependent on inductor performance, where the poor inductor quality factor ( ) of silicon processes leads to degradation in circuit efficacy, especially at RF and microwave frequencies. Several techniques have been proposed to enhance the of integrated on-chip inductors, but the most effective method of improvement is to lower the series resistance by increasing the inductor metal thickness. This paper presents the most cost-effective method of achieving a thick metal by using a standard 0.18-m multilayer BiCMOS process. An expanded physically based model for multiple-metal stacked inductors is presented, which expands on previous research to show the effects and limitations of stacking two, three, and four metal layers in a five-metal-layer process. The excellent accuracy of this geometrical model is illustrated with respect to a range of inductor designs showing that an improvement in of more than 50% may be achieved. Due to the increased parasitics in multilayer structures, the improvement is very frequency dependent, which is clearly predicted with the expanded model. The predictive capability of the model is further used to provide detailed insight into the effectiveness of a patterned ground shield for different substrate characteristics. This predictive ability will contribute greatly to first time right inductor designs and eliminate the expensive and time-consuming fabrication iterations required to fine tune other inductor models.Index Terms-Integrated stacked inductor model, patterned ground shield (PGS), improvement, prediction.

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A compact, planar antenna operating at 433 MHz is proposed for wireless smart systems with dimensions of 51 × 28 mm 2 including a ground plane, and printed on a low-cost FR4 material. Significant size reduction is achieved using the variation of an inverted-F antenna configuration with a square-spiral section and rectangular patch element. Fine-tuning of the antenna's resonant frequency is possible using a small capacitive stub. Sensor and radio transceiver electronics can be accommodated above the ground plane. The measured results indicate a 10 dB return loss bandwidth of 4.5 MHz, and a peak realised gain of −13 dBi with omnidirectional radiation characteristics.Introduction: In recent years, wireless smart systems have rapidly emerged in areas such as healthcare and activity monitoring with applications in outpatient monitoring and the provision of in-home lifelines for the elderly [1, 2]. Wireless sensor motes operating in the 433 MHz industrial scientific and medical (ISM) band are a popular choice for low data rate applications and provide a good communication range due to reduced body absorption when compared to higher frequencies.Small and lightweight sensor realisations are key constraints for unobtrusive monitoring and an example of a 433 MHz sensor device is presented in [3] measuring 25 mm 2 in size excluding the antenna. A λ 0 /4 resonant antenna at 433 MHz would require dimensions of ∼170 mm excluding a ground plane. For the intended application, the goal is to realise a wrist-worn sensor with an area of 51 × 28 mm 2 . This size constraint means that a λ 0 /4 antenna is impractical and significant reduction of antenna dimensions is therefore necessary. It is well known however that decreasing the antenna size can negatively affect the efficiency, gain and bandwidth of the antenna [4]. Several small-sized 433 MHz antennas have been reported in the literature [5][6][7], but these antennas are too large in size for this application. A dual-band loop antenna configuration with dimensions very similar to those required is presented in [8] with a reported gain figure of −20 dBi at 433 MHz. In this Letter, an antenna structure is proposed that meets the required size constraints while also providing an acceptable figure for a peak realised gain of −13 dBi. The Letter discusses the design of the proposed antenna structure as well as size reduction methods. In addition, the simulated and measured results for the antenna impedance and radiation characteristics are presented and discussed.

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