Future small satellites require the development of reconfigurable antennas. Designing such antennas, especially single port patch antennas with circular polarization is a challenging task. Therefore, we propose both right-hand/left-hand circularly polarized (RHCP/LHCP) antenna which can reconfigure. The proposed follows topology E-shape that single-layer and single-feed two RF switches. switche...

Considerable work has been published to define the minimum possible antenna radiation as a function of the antenna size and gain. Many of the derivations assume an enclosing sphere and deal only with the fields external to this sphere. As a result, the limits tend to be overly optimistic, and realizable antennas generally have ’s considerably higher than the minimum values predicted by these th...

Image quality of wide field observations with the ALMA has been studied with imaging simulations. Results of the simulations showed that antenna pointing errors are a serious problem for obtaining high quality images because they make a large error in visibilities in the central (u,v) hole estimated by mosaicing data processings. The ALMA Compact Array (ACA) with more than 10 smaller dishes (6-...

Phased-array feeds are possibly the best option for the 240 to 1200 MHz band on VLA antennas due to their wide bandwidth and relatively small size. One of the greatest assets of these antennas is the ability to produce a shaped beam by appropriately phasing the elements allowing in some cases nearly uniform aperture illumination with minimal ground-directed spillover. The beam-forming propertie...

Two new triple band small size composite-resonator microstrip antenna configurations for wireless communications are presented in this paper. The proposed antennas, each is built of three resonant elements. Two types of compact short-circuited resonators are used; stepped impedance and quarter-wave resonators. The design procedure based on composing the antenna resonators is straightforward and...

Downlink of a multiuser MIMO system is considered, in which the base station (BS) and the user terminals are both equipped with multiple antennas. Efficient transmission schemes based on zero-forcing (ZF) linear receiver processing, eigenmode transmission, and partial channel state information (CSI) at the BS transmitter are proposed. The proposed schemes utilize a handshaking procedure between...

High-frequency backscatter radio systems operate in the backscatter channel, a channel whose envelope probability density function (PDF) and bit-error-rate (BER) performance are strongly affected by the relationship between small-scale fading in the reader-to-tag and tag-to-reader propagation links – i.e., link correlation. This paper shows that backscatter radio systems using co-located reader...

Microstrip antennas have numerous advantages such as small size, low fabrication cost, light weight and can be easily installed in the systems and it finds its applications in various systems like aircraft, satellite and spacecraft. But it has drawback of narrow bandwidth. To overcome this drawback, Microstrip Antennas with Defected Ground structure can be used. In this paper, a microstrip patc...

Microstrip patch antennas are well known for their advantages in terms of small weight, low profile and ease of manufacture. However, the main limiting factor in implementing these antennas in many applications is their low impedance bandwidth (typically 2-3%). One popularly used technique of enhancing the bandwidth is to use multi-layered microstrip[1,2]. The most widely accepted structure in ...