Switched Beam Smart Antenna System Research Articles

DC–20‐GHz compact SPQT switch for butler matrix switched beam smart antenna system

AbstractA DC–20‐GHz broadband and compact single‐pole‐quadruple‐throw (SPQT) switch for Butler matrix switched beam smart antenna system application has been designed and fabricated on 0.15‐μm GaAs pHEMT process. By adopting inductive high impedance transmission lines in series‐shunt switch topology, the SPQT switch demonstrates an insertion loss of 1.25–3.53 dB from DC to 20 GHz, and the isolation is higher than 22 dB with a compact chip size of 1.5 mm2. The measured output 1 dB compression point (OP1 dB) is 16 dBm at 12 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2023–2026, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26993

High altitude airborne cellular base stations antenna analysis

Obtaining continual mobile communication coverage over two or more disparate regions from an airborne platform utilizing a deployable cellular base station has proven to be challenging due to the resulting signal spatial structure and signal gain observed from the mobile ground users. A two-dimensional aircraft simulation environment has been developed to evaluate the optimal link budget of an antenna system coupled with a Code Division Multiple Access (CDMA) base station positioned above 45,000 feet in a designated elliptical orbital pattern in an effort to acquire broader and longer communication coverage. This will analyze the signal excess results of both an omni-directional conventional antenna system (CAS) and a switched-beam smart antenna system (SBSAS) with multiple mobile ground users present. Collectively, these results constitute a basis for low-risk implementation for a high altitude airborne deployable cellular base station.

Printed Circuit Switched-Beam Smart Antenna System Using 4x4 Butler Matrix Beamforming Network At The Band (11.25-12.85) GHz

The aim of this paper is to investigate and implement the use of special type of beamformer (the Butler matrix) with an antenna array in a switched beam smart antenna system. This system is designed and analyzed to be used for satellite communication in the band (11.25-12.85) GHz. The system, including a (4x4) Butler matrix and a 4-element microstrip patch antenna array, is completely built using microstrip printed circuit technique for the sake of compactness. The results obtained by simulation and measurement show that this system can produce narrow multibeams in different directions with a wide coverage angle of about 146 and a relatively high crossover level of -3 dB. The resulted beams have directivities range from 9 dB to 11 dB, and half-power beamwidths range from 30 to 42 with relatively low side lobe level of less than -10 dB.

Development of an Adaptive and a Switched Beam Smart Antenna System for Wireless Communications

This study concentrates on the development of two separate Smart Antenna Systems for the 2.45 GHz ISM band. Both systems incorporate the RF-beamforming method. Each system has the ability to point the beam in a three dimensional space, both in azimuth and in elevation direction. The Switched Beam System adopts a passive network-based beamforming approach, using 2-D Butler matrix topologies. The Adaptive System utilizes the vector modulator method, but only in the azimuth direction, increasing beam-steering accuracy, whereas introducing complexity and cost. The system design is presented for both cases, along with some module design and testing examples. A comparison of the two systems will be also discussed.

Performance evaluation of medium access control for multiple-beam antenna nodes in a wireless LAN

We consider the medium access control (MAC) protocol design for nodes in a wireless LAN that use a wide-azimuth switched beam smart antenna system comprised of a multiple beam antenna array. The one-hop performance of carrier sense multiple access (CSMA) as well as slotted aloha for such a system is presented analytically and through simulation. The problem of synchronization of multiple beams in CSMA is investigated in our analysis. Our results show that, under heavy offered load conditions, CSMA is a good choice with nodes that have multiple-beam smart antennas, despite the performance loss due to the beam synchronization, providing a stable throughput that approaches unity and is invariant to fluctuations in the offered load. Slotted Aloha, on the other hand, is capable of higher peak throughput in a narrow range of offered loads as more switched beams are employed, but performance drastically reduces beyond optimum offered loads. We also introduce a method, expanded receive rule (ERR), whereby the tight synchronization among different beams of a receiver node in CSMA is relaxed, which is observed to provide better throughput. Finally, we also present performance results for a 4-way-handshake-type carrier sense mechanism using multiple beam antennas.

Performance of switched-beam smart antennas for cellular radio systems

The performance and feasibility of switched-beam smart antennas for cellular radio systems is investigated. Switched-beam smart antenna systems are shown to either increase the capacity or extend the radio coverage by increasing the carrier-to-interference ratio (CIR). The trunking efficiency degradation caused by narrow-beam sectoring can be recovered or even improved by using a variety of trunkpool techniques. One drawback of switched-beam smart antennas is that the improvement in reverse-channel performance is not uniform over the entire cell area, and this presents a limiting factor on the achievable gains, practical considerations such as power control and the limited deployment of smart antenna cells are also addressed.