In this paper, we propose a new architecture and performance analysis for beam index modulation (BIM) wireless communication implemented with the aid of analog beamforming. The BIM concept is presented in order to extend and adapt the spatial modulation (SM) concept to sparse wireless communication channel environments. It is shown that when compared with the conventional beamforming and SM strategies, the BIM system can achieve higher spectrum efficiency in high signal to noise ratio (SNR) and non-line-of-sight (nLoS) sparse channel scenarios. Furthermore, different to the previous spatial scattering modulation (SSM) work the proposed BIM architectures have reduced hardware complexity, and, importantly, in some nLoS sparse channel conditions the BIM can also outperform the SSM. The above findings were further validated by some demonstrative experiments that were conducted at 10 GHz.

Products of passive intermodulation (PIM) generated by weak nonlinearities of passive circuits subjected to relatively high transmit power of multicarrier signals may cause strong interference in emerging broadband and multiradio communication systems. This paper presents a new approach to a characterization of distributed nonlinearities in printed circuits fabricated on commercial grade microwave laminate materials. An efficient procedure for PIM characterization has been devised using the commercial RF-CAD software. The phenomenological model has been developed to take into account concurrent distributed nonlinearities of printed transmission lines and to evaluate PIM products of arbitrary order. It has been observed for the first time that the sources of nonlinearity in typical microstrip circuits may have highly uneven distributions which require a different means for PIM characterization and modeling. The proposed methodology has been validated by accurate predictions of the PIM response of complex circuit layouts. The results of this paper pave the way to a holistic approach to the design of planar microwave circuits and devices under given linearity constraints.

This paper presents the results of experimental study of passive intermodulation (PIM) generation in microstrip lines with U-shaped and meandered strips, impedance tapers, and strips with the profiled edges. It is shown that the geometrical discontinuities in printed circuits may have a noticeable impact on distributed PIM generation even when their effect is indiscernible in the linear regime measurements. A consistent interpretation of the observed phenomena has been proposed on the basis of the phase synchronism in the four-wave mixing process. The results of this study reveal new features of PIM production important for the design and characterization of low-PIM microstrip circuits.

A new implementation of a beam-steering transmitarray is proposed based on the tiled array architecture. Each pixel of the transmitarray is manufactured as a standalone unit which can be hard-wired for specific transmission characteristics. A set of complementary units, providing reciprocal phase-shifts, can be assembled in a prescribed spatial phase-modulation pattern to perform beam steering and beam forming in a broad spatial range. A compact circuit model of the tiled unit cell is proposed and characterized with full-wave electromagnetic simulations. Waveguide measurements of a prototype unit cell have been carried out. A design example of a tiled 10 × 10-element 1-bit beam-steering transmitarray is presented and its performance benchmarked against the conventional single-panel, i.e., unibody, counterpart. Prototypes of the tiled and single-panel C-band transmitarrays have been fabricated and tested, demonstrating their close performance, good agreement with simulations and a weak effect of fabrication tolerances. The proposed transmitarray antenna configuration has great potential for fifth-generation (5G) communication systems.

A new architecture of surface acoustic wave (SAW) sensor-tags with lower insertion loss and enhanced sensitivity is investigated. It efficiently employs two transducer arrays at the input and output of the acoustic channel, respectively. The improved sensitivity is attained due to a higher number of stronger constituent signals contributing constructively to the device response. An efficient matrix modeling approach is generalized to permit fast design and synthesis of the multitransducer sensor-tags with arbitrary topologies. The modeling approach consistency is validated by energy balance. Several simulation examples of new 6 GHz SAW sensor-tags, implemented on 128°YX-LiNbO3 substrate, are presented and compared against a conventional reflective delay line device. The effects of finite electrode resistivity and SAW beam diffraction are evaluated numerically and the SAW sensor-tag design tradeoffs and principles are established.