Body integrated wearable electronics can be used for advanced health monitoring, security, and wellness. Due to the complex, asymmetric surface of human body and atypical motion such as stretching in elbow, fi nger joints, wrist, knee, ankle, etc. electronics integrated to body need to be physically fl exible, conforming, and stretchable. In that context, state-of-theart electronics are unusable due to their bulky, rigid, and brittle framework. Therefore, it is critical to develop stretchable electronics which can physically stretch to absorb the strain associated with body movements. While research in stretchable electronics has started to gain momentum, a stretchable antenna which can perform far-fi eld communications and can operate at constant frequency, such that physical shape modulation will not compromise its functionality, is yet to be realized. Here, a stretchable antenna is shown, using a low-cost metal (copper) on fl exible polymeric platform, which functions at constant frequency of 2.45 GHz, for far-fi eld applications. While mounted on a stretchable fabric worn by a human subject, the fabricated antenna communicated at a distance of 80 m with 1.25 mW transmitted power. This work shows an integration strategy from compact antenna design to its practical experimentation for enhanced data communication capability in future generation wearable electronics.

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The field of printed electronics is still in its infancy and most of the reported work is based on commercially available nanoparticle-based metallic inks. Although fully printed devices that employ dielectric/semiconductor inks have recently been reported, there is a dearth of functional inks that can demonstrate controllable devices. The lack of availability of functional inks is a barrier to the widespread use of fully printed devices. For radio-frequency (RF) electronics, magnetic materials have many uses in reconfigurable components but rely on expensive and rigid ferrite materials. A suitable magnetic ink can facilitate the realization of fully printed, magnetically controlled, tunable devices. This report presents the development of an iron oxide nanoparticle-based magnetic ink. First, a tunable inductor is fully printed using iron oxide nanoparticle-based magnetic ink. Furthermore, iron oxide nanoparticles were functionalized with oleic acid to make them compatible with a UV-curable SU8 solution. Functionalized iron oxide nanoparticles were successfully embedded in the SU8 matrix to make magnetic substrate. The as-fabricated substrate was characterized for its magnetostatic and microwave properties. A frequency tunable printed patch antenna is demonstrated using the magnetic and in-house silver-organo-complex (SOC) inks. This is a step towards low-cost, fully printed, controllable electronic components.

The theory and design of a half mode SIW ferrite LTCC based phase shifter is presented in this work. Unlike typical ferrite based designs, the biasing is done through embedded windings in a multilayer substrate which not only obviates the requirement of bulky electromagnets but also prevents loss of bias fields at the air-to-ferrite interface. The phase shifter is operated in the partially magnetized state of ferrite substrate. Through the combined effect of embedded windings, half mode waveguide operation and partially magnetized state, the required bias fields have been reduced by 90% as compared to conventional ferrite based designs employing electromagnets. A complete analytical model, backed up by electromagnetic simulations and measured results from a prototype, is presented in this paper. The fabricated prototype demonstrates a phase shift of 83.2 at a center frequency of 13.1 GHz and a figure of merit of 83.2/dB. As a proof-of-concept, the proposed phase shifter design is monolithically integrated with a twoelement antenna array to demonstrate a measured beam steering of 30. The phase shifter design is highly efficient in terms of required bias fields, has a small form factor and can be easily integrated with other electronic components and systems.

Tunable filters that are based on ferrite materials often require large and bulky electromagnets. In this work, we present a tunable filter in the Ku-band, which is realized in multilayer ferrite LTCC substrate with embedded bias windings, thus negating the need of a large electromagnet. Also, because of the embedded windings, the bias fields are not lost at the air-substrate interface and therefore the field and current requirements are reduced by an order of magnitude as compared to the previously reported filters. A simulation strategy that uses full permeability tensor with arbitrarily directed magnetic fields has been used to model the filter on a partially magnetized ferrite substrate. Special attention has also been paid to approximate the non-uniform magneto-static fields produced by the embedded windings. The complete design is implemented in 10 layers of ferrite LTCC, making it the first magnetically tunable filter with embedded windings and extremely small size [(5 5 ) ]. The filter demonstrates a measured tunability of 4% and an insertion loss of 2.3 dB. With the small form factor, embedded windings, and low bias requirements, the design is highly suitable for compact and tunable SoP applications.Index Terms-Bandpass filter (BPF), ferrite, low temperature co-fired ceramics (LTCC), system on package (SoP).