This paper introduces a base station antenna system as a future cellular technology. The base station antenna system is the key to achieving high-speed data transmission. It is particularly important to improve the frequency reuse factor as one of the roles of a base station. Furthermore, in order to solve the interference problem due to the same frequency being used by the macro cell and the small cell, the author focuses on beam and null control using an AAS (Active Antenna System) and elucidates their effects through area simulations and field tests. The results showed that AAS can improve the SINR (signal to interference-plus-noise ratio) of the small cell area inside macro cells. The paper shows that cell quality performance can be improved by incorporating the AAS into a cellular base station as its antenna system for beyond 4G radio access technology including the 5G cellular system.

In this paper, we investigate a preference-aware multicast mechanism in active array aided LTE (Long Term Evolution) networks. An active antenna system can direct vertical beams in different horizontal and vertical directions, so the amount of energy delivered is more concentrated on the target users. The active array provides each multicast group with an individual beam with specific downtilt delivering shared video to all users in the group. For the multicast system, the objective of our proposed resource allocation scheme is to maximize the total throughput, subject to the constraints of power, subcarrier and antenna downtilt, as well as horizontal angles and the vertical half power bandwidth. To solve the problem, individual beams are steered for multicast groups. Furthermore, a novel subcarrier assignment scheme is proposed to enhance the spectrum resource utilization, and the optimal power allocation is obtained by virtue of Lagrangian method. Simulation results demonstrate the throughput and the spectral efficiency enhancement of our proposed scheme over other conditional schemes.

Several broad bandwidth, electrically small, non-Foster element-augmented antennas have been designed, analyzed and measured. Both electric loop (protractor) and electric dipole (Egyptian axe) structures have been selected as the near-field resonant parasitic (NFRP) elements for these antenna designs. In order to increase their instantaneous 10dB bandwidth, negative impedance convertor (NIC)-based capacitor and inductor elements have been designed accordingly to be incorporated internally into those NFRP elements. Proper design and analysis procedures for these systems are introduced. The simulated performance characteristics of the resulting non-Foster element-augmented protractor and Egyptian axe dipole antennas are presented. Favorable comparisons with their experimentally measured values are demonstrated.

This paper proposes a new circuit-fed 2-D amplifying array architecture using the multi-ported aperture-coupled patch antennas. The power distribution achieved by this array is formed by stacking three kinds of basic cells repeatedly. Each cell, which serves as a radiator and also a power relay, has a multi-ported patch antenna and one or two amplifiers. The signal transmission coefficient of the cell from the input port to the output port is designed with a power level of 0 dB and a phase of 360. An X-band 4 3 element array with uniform amplitude distribution is demonstrated. The measured results, such as the antenna gain and the radiation patterns, agree very well with the predicted ones, due to the precision design of the basic cells. The measured gain of the antenna array is 27.7 dBiA at the frequency of 10.4 GHz on the H-plane, with a half-power beamwidth of 14 in the H-plane and 16 in the E-plane.

Active integrated antenna techniques have high potential for giving smaller size, lighter weight, lower cost and higher efficiency, in particular to millimeter-wave circuit-antenna systems. This paper gives a review of active integrated antenna techniques with emphasis on beam steering and retrodirective antenna arrays. Various beam steering operations of integrated antenna oscillator arrays using locking phenomena are presented. Beam steering arrays of such type have the feature that phase shifters are not necessary in the arrays. Arrays with higher harmonic output radiation can enlarge the beam steering range. Arrays of locked active antennas which operate as self-oscillating mixers can be beam controllable receiving antennas.

Beam control using active antenna arrays with self-oscillating harmonic mixers has been investigated. The active antenna is composed of a patch antenna receiving RF signal and a parallel feedback type oscillator which operates as the self-oscillating harmonic mixer, and down-converts the received RF signal into IF signal. The mixer has two ports for local oscillating (LO) signal. One is an output port extracting the LO signal. The other is an input port for an injection signal to synchronize the local oscillation. The mixers can be coupled unilaterally without other nonreciprocal components by connecting the output port to the input port in the next mixer. In the unilaterally coupled array, the phase differences of the LO signals between the adjacent mixers can be varied without phase shifters in injection locking state by changing the local free-running frequencies of the self-oscillating mixers. The receiving pattern can be controlled by combining the IF signals from the individual active antennas, which have phases associated with the LO signals. The IF is difference between the RF and double of the LO frequency so that arbitrary phase differences from 0 to 2π radian can be provided to the output IF signals. The experiments using the two- and three-element arrays demonstrated beam control capability.

A phased array behavior of a unilaterally coupled active antennas has been investigated. The active antenna is composed of a patch antenna and a parallel feedback type oscillator which can be coupled unilaterally to other oscillators without other nonreciprocal components. Numerical calculations of the reduced equations describing the behavior of the coupled oscillators array demonstrated that the phase differences between the oscillators can be varied up to about π/2 by giving the frequency changes from the injection locking frequency to the oscillators except of the first one. The oscillator mounted with the varactor diode for wide tuning range exhibited the property suitable for constructing the unilaterally coupled array. In the experiments at X-band, the electromagnetic wave radiated from the five element array was successfully scanned.

Design of circularly polarized active antennas of dual-fed square patch type is given, and spatial power combining and phased array operation of the antennas have been successfully achieved. In a phased array experiment of the arrays with two and three active antennas by the method of varying their free-running oscillation frequencies, we obtained the scan angles from -12 to +13 and those from -13 to +13, respectively, and good axial ratios together with high spatial power-combining efficiencies.

In coupled oscillator arrays, it is possible to control the inter-element phase shift up to 180 by free-running frequency distribution based on injection-locking phenomenon. In this paper, a new technique to control the inter-element phase shift electronically up to the maximum extent of 360 is reported. Oscillators are unilaterally coupled to the preceding oscillator through one of the two paths, which differ from each other 180 in electrical length and each includes an amplifier. Turning on the desired amplifier one can control the phase shift either -180 to 0 or 0 to 180. The technique was applied in a three-element oscillator array each coupled to a patch antenna via a round aperture. The radiation beam of the array could be scanned 47 in total.

Two types of CPW-fed active antenna for television receivers, printed on thin dielectric film, are analyzed numerically and experimentally and their broadband operations are reported. The actual gain of the receiving active antenna is expressed in terms of the transducer power gain of the amplifier circuit and the effective length of the passive antenna. Between the feed point of the passive antenna element and the CPW, the silicon transistor 2SC2585 or 2SC3604 is integrated with a dipole antenna or loop antenna. The actual gains of a dipole antenna with 24 cm length are more than 8 dBd (relative gain to the standard half-wave dipole) at frequencies from 470 to 770 MHz for television channels 13-62 in Japan. In the case of a loop antenna with a size of 25. 8 cm12 cm, actual gains of more than 3. 5 dBd are obtained for channels 1-12, from 90 to 222 MHz, and more than 6. 5 dBd for channels 13-62, from 470 to 770 MHz.

Several types of transmission-line coupling are analyzed to use in one- and two-dimensional active antenna arrays, and a method is developed to scan the beam of the arrays using the mutual locking theory. To compensate the undesired effect of strong radiative coupling of the nearest neighbor elements on the phased array performance, addition of resistive stubs to the end elements is proposed. In a 14 array it was observed that after the connection of resistive stubs, the scanning range of the array increased considerably. The effect of oscillator amplitudes on the phased array behavior is explored numerically. In the experiments main beam of 22 and 33 active antenna arrays were steered up to 25 and 15, respectively in the H-plane.

This paper reviews some of the recent effort in the area of microwave-optical interaction as applied to enhance the utility of the active integrated antennas and arrays. The paper consists of two parts. In the first part, the optical bias is used as a hidden port to control the characteristics of the active integrated antennas. Two examples will be presented. In the second part, an optical carrier is used for remoting of active integrated antenna for beam control.

The high-Tc superconducting active antenna proposed here for millimeter and submillimeter radiowave communications, uses a YBCO slot antenna with a series Josephson junction array to increase the normal-state resistance of the junctions, in order to ensure impedance matching between the antenna and the junctions. The antenna is a coplanar waveguide fed slot antenna, which can be easily and monolithically combined with the Josephson junctions. The design frequency of the antenna is 10 GHz and the obtained bandwidth of a VSWR less than 2 was 4.1%. Normal-state resistance values of the junction array could be confirmed by measuring I-V characteristics and 100-MHz impedance measurements, and both agree very well. Microwave mixing experiments were carried out using the junction array with the antenna, and the experiments showed that the conversion gain of the junction was proportional to the number of the junctions. The conversion gain of an eight-junction mixer with the antenna was found to be -6 dB.

High Tc superconducting (SC) active antennas made from thin films were produced by the magnetron sputtering method. The SC active antennas are found to be good for detecting 50GHz electromagnetic waves. Furthermore, the improvement of the sensitivity of the SC active antennas is demonstrated with the use of a corner reflector.