This report presents design concepts and experimental data of planar active antenna and quasi-optical power combining arrays with strong coupling to realize a compact and low-cost radar and communication system. The prototype circuits for this purpose were made in a layered configuration using microstrip lines and in a uniplanar structure using CPW's. As an active source, an FET was selected. As a unit cell of the power combining array, a single layered active antenna using microstrip lines and slots was fabricated. In the design, small signal S-parameters were used to determine the circuit configuration while a large signal analysis to the entire circuit involving the slot antenna input impedance was carried out. The circuit designed for 10 GHz was found to operate at 9.3 GHz and the other designed for 25 GHz at 24 GHz. In addition, the circuit with CPW's and slot designed for 10 GHz was found to operate at 8.6 GHz. Based on these successful results, linear power combining arrays were made. For the strong coupling, each oscillator output is connected by a single transmission line. Several 6-element microstrip arrays and a 4-element CPW array were fabricated. In the former, sharp main beams were obtained. To obtain a millimeter-wave operating frequency, the second harmonic spatial power combining array made with FET's were demonstrated around 40 GHz. To show a topology of a 2-dimensional array, a 16-element dual polarized array at 7.8 GEL was made. To obtain the maximum in-phase radiation signal, impedance matching, a phase of the radiation signal and a signal phase of each oscillator were taken into account ... Active antenna, Quasi-optical technique, Optical control, Spatial power combiner.

This book presents state-of-the-art trends in reconfigurable active and passive planar antennas and their applications in wireless communication systems operating in the frequency band 5-6 GHz. Due to various key features such as multifunction antenna design, compactness, planar nature, and low cost, these technologies are becoming popular for current and future wireless applications. This book discusses different novel antenna designs and their working principles in detail. The modern and future wireless systems require wideband antennas to accommodate various channels in a single band or in separate bands. The carrier aggregation (CA) has been introduced in the modern wireless systems such as LTE-advanced systems and 5G./6G. In CA, a device can use several channels for transmission and reception. The used channels can exist in the same frequency band (intra-band CA) or in distinct bands (inter-band CA). To accommodate more channels, more bandwidth is required within the operating band. For portable devices, circularly polarized (CP) antennas are more advantageous over linearly polarized antennas since in CP antennas, there is low risk of misalignment and, hence encountering interference. Circularly polarized antenna also provides higher link reliability for the portable devices. To provide high data rates, more bandwidth is needed to accommodate more channels. Various multifunction, compact, and wideband antennas for plethora of applications are addressed in detail in this book. The scope of developing reconfigurable active antennas for application in beam switching, beam steering, wireless charging, security systems, etc., is described. This book concludes by giving glimpses of antenna requirements for future wireless communication systems.

Electrical Engineering Active Antennas and Quasi-Optical Arrays Whether communications, radar, transportation, or defense drives your interest in solid-state devices at microwave and millimeter-wave frequencies, this ready reference book provides you with a useful review of quasi-optical power combining and active integrated antennas. Brought to you in one convenient volume are key reprinted papers from leading experts in microwave technology. Their valuable perspectives range from the most current advances to historical developments. Included as a special feature is an invited paper, never-before-published, which presents an overview of quasi-optical power combining by noted authority J. W. Mink and colleagues. You will discover other helpful highlighted topics such as: Transmitting and receiving active antennas Spatial power combining oscillators Spatial combining amplifiers Beam control Active integrated antennas and quasi-optical systems Analysis and CAD Emerging technologies—two dimensional quasi-optics

Provides systematic coverage of the theory, physics, functional designs, and engineering applications of advanced electromagnetic surfaces.