Antenna Switching Research Articles

A FREQUENCY-SELECTING TECHNIQUE FOR MOBILE HANDSET ANTENNAS BASED ON CAPACITANCE SWITCHING

This paper introduces a mobile switchable antenna for long term evolution (LTE) of the 4th generation (4G), applicable to all mobile service bands. The validity of this antenna is assessed by design, realization, and measurement. A new frequency-selecting method is used in the proposed antenna, based on capacitance switching among four states. Due to the limited antenna space in existing terminals, it is quite di-cult to cover the entire low band with a single antenna. To overcome this di-culty, three single- pole double-throw (SPDT) switches, one 74HC04, and four capacitors are used. The resulting antenna covers the LTE (698{798MHz) and GSM (824{960MHz) bands in the low-band characteristic by realizing four capacitance states and at the same time covers the DCS (1710{1880 MHz)/PCS (1850{1990MHz)/WCDMA (1920{2170MHz) bands in the high-band characteristic. The antenna provides a gain of i1:04{6.00dBi, a radiation e-ciency of 32.73{74.99%, and omnidirectional characteristics in the H-plane. Because of this outstanding performance, it is expected that the new frequency - selecting technique will be applied in 4G mobile communication terminals.

Characterization of Performance of a Mobile MIMO Antenna in Free Space

This letter presents an antenna design method for a dual antenna with high isolation for mobile stations (MSs) and includes a verification method for improving the correlation performance of an MS that uses a proposed multiple-input-multiple-output (MIMO) antenna by using MIMO over-the-air (OTA) channel models. The large-scale parameters for the MIMO OTA channel models are important because they determine the fixed geometrical parameters to be used for channel impulse response realization. The correlation performance of an MS has a strong relation to the cross-polarization discrimination (XPD) of the second branch antenna both numerically and experimentally. This study applies modern technology to implement MIMO antenna switch high isolation by selecting Band 5 to have low-frequency fabricated antenna samples that have several XPD values, thereby comparing their characteristics.

SIMULATION OF WAVEGUIDE TURNSTILE‐TYPE JUNCTION WITH A SQUARE WAVEGUIDE OUTPUT FOR INCOHERENT SCATTER RADAR ANTENNA

The computer simulation of the turnstile connection with a square waveguide output has been carried out. The matching unit dimensions have been optimized, and the main characteristics have been obtained. The use of the connection as a polarizer and antenna switch for incoherent radar is proposed.

Spacial Filter of Weighting Method Based on Spectrum Analyse

The selection of a certain scope angle signal in the traditional method is to switch the hard switches in antennas, this paper proposes a method, which based on a weighting method to filter the signal in certain directions, namely spacial filter. With array antennas，the compositive signal can be acquired, by which the phrase and plus (weighting) of each unit antenna’s signal be adjusted and then the signals be added. In different time, signals can be selected in any scope of directions through adjusting each channels by different weighting. The weighting parameters can be obtained through the analysis of spacial signal and spacial spectrum, and then obtains an appropriate weighting window function. Simulation shows that Hamming window’s weighting is the best among the three representative windows functions. It can obtain a low sidelobe (-44dB) and less rising edge and declining edges. And the paper also give a hardware structure.

Relay on-off threshold for NDF protocol with distributed orthogonal space-time block codes

Abstract In this article, a relay on-off threshold (ROT) based on symbol error rate is derived for the cooperative communication networks with multiple antennas, where the non-orthogonal decode-and-forward (NDF) protocol with source antenna switching and linear combining decoding are used as the relaying protocol and decoding scheme, respectively. The optimal ROT for the cases using distributed orthogonal space-time block codes is derived for high signal to noise ratio (SNR) region and also a suboptimal ROT is provided for low SNR region. Finally, the diversity order of the NDF protocol using the relay on-off scheme with the proposed ROT is derived and its performance is verified through numerical analysis.

Investigation of a high power electromagnetic pulse source

A high power electromagnetic pulse source with a resonant antenna driven by a compact power supply was investigated in this paper. To match the impedance of the resonant antenna and initial power source, a compact power conditioning circuit based on electro exploding opening switch (EEOS) and pulsed transformer was adopted. In the preliminary experiments, an impulse capacitor was used to drive the system. With the opening of the EEOS at the current of 15 kA flowing trough the primary of the transformer, the resonant antenna was rapidly charged to about -370 kV within a time of about 100 ns. When the switch in the resonant antenna closed at the charging voltage of about -202 kV, the peak intensity of the detected electric field at a distance of about 10 m from the center of the source was 7.2 kV∕m. The corresponding peak power of the radiated electromagnetic field reached 76 MW, while the total radiated electromagnetic energy was about 0.65 J. The total energy efficiency of the resonant antenna was about 22% which can be improved by increasing the closing rapidity of the switch in the antenna.

Receive Antenna Selection for Time-Varying Channels Using Discrete Prolate Spheroidal Sequences

Receive antenna selection (AS) has been shown to maintain the diversity benefits of multiple antennas while potentially reducing hardware costs. However, the promised diversity gains of receive AS depend on the assumptions of perfect channel knowledge at the receiver and slowly time-varying fading. By explicitly accounting for practical constraints imposed by the next-generation wireless standards such as training, packetization and antenna switching time, we propose a single receive AS method for time-varying fading channels. The method exploits the low training overhead and accuracy possible from the use of discrete prolate spheroidal (DPS) sequences based reduced rank subspace projection techniques. It only requires knowledge of the Doppler bandwidth, and does not require detailed correlation knowledge. Closed-form expressions for the channel prediction and estimation error as well as symbol error probability (SEP) of M-ary phase-shift keying (MPSK) for symbol-by-symbol receive AS are also derived. It is shown that the proposed AS scheme, after accounting for the practical limitations mentioned above, outperforms the ideal conventional single-input single-output (SISO) system with perfect CSI and no AS at the receiver and AS with conventional estimation based on complex exponential basis functions.

A Loop-Loaded PIFA for Switchable Beam Patterns

A switchable beam pattern antenna composed of electric and magnetic radiators, i.e., a monopole and a loop, is proposed. The proposed antenna is designed to operate at 2 GHz for wireless communications. By controlling the state of the switch located at the junction between the dipole and the loop, the antenna can select one between two beam patterns. The simulated 10 dB frequency bandwidths are observed to be approximately 9.5% (1.87–2.06 GHz) and 10.0% (1.93–2.13 GHz) for on and off states, respectively. The simulated and measured results indicate that the proposed antenna operates at approximately the same frequencies, whereas it is clearly observed that the antenna’s maximum beam direction is alternated depending on the switching states.

Adaptive penta-band handset antenna with hand effect compensation

The increase in the number of cellular operating bands and the ever-increasing criteria antenna size reduction has pushed the need to use switchable antenna structures. Further, the presence of a hand in the close vicinity of the antenna causes deterioration in performance. The authors present a switchable antenna technique, evaluate the effect of the human hand on it and discuss a novel method to compensate for the mismatch. A penta-band switchable planar inverted-F antenna covering 824-960 and 1710-2170-MHz has been used in this study. The presence of the hand was observed to cause 2.0-6.0-dB loss in efficiency for the low band. Using the proposed extra-ground antenna switching method and the dynamic antenna matching, technique the total efficiency of the antenna can be improved by 0.5-2.5-dB compared to the mismatched case.

Four-port beam reconfigurable antenna array for pattern diversity system

This study investigates a practical design for a switched beam planar antenna that can be implemented as a compact, low-cost switchable and/or reconfigurable beam antenna array. The antenna consists of a four-port antenna array, which is based on L-shaped quarter-wavelength slot antenna elements. This type of antenna array is a planar structure and its maximum directional radiation beam pattern presents in an azimuth plane covering 3600. The antenna array operates based on the `ON' or `OFF' states of PIN diodes in each individual slot antenna element and the combined signals from the four-port output. Therefore by properly controlling the state of the PIN diodes, the antenna exposes its characteristics of switchable/ reconfigurable beam patterns in the Φ-plane. To validate the proposed design, a small smart, switched-beam antenna operating at 2.7 GHz in multiple input-multiple output applications is simulated and fabricated.

DYNAMIC BASESTATION ANTENNA DESIGN FOR LOW ENERGY NETWORKS

A challenge faced by the information and communications technology (ICT) industry is the growing data volume and associated energy consumption. How to both meet a dynamic tra-c demand at a consistently low energy consumption level is of importance from both commercial and climate change perspectives. This paper proposes a dynamic basestation concept that allows the number of active sectors to be adjusted in accordance with the tra-c load. This is achieved through a novel switchable antenna design that can adjust the azimuth beam-width by using a tuneable re∞ector. Simulation and theoretical results show that the dynamic basestation can reduce the total operational energy of a cellular network by a peak of 75% and a mean of 38%.

Frequency and polarisation reconfigurability from an open-loop square ring antenna

In this study, two types of reconfigurable microstrip square ring antennas are proposed. The basic structure of the proposed antennas is an open-loop-type square ring resonator. To increase antenna gain, a square ring slot with narrow width is embedded into the ground plane. The proposed antenna is fed by a T-shaped microstrip through a gap coupling. Depending on the location of the gap in the square ring, the open-loop square ring antenna exhibits different resonant frequencies or polarisations. The state of the gaps in the ring can be adjusted by controlling the bias voltage applied to the Positive-Intrinsic-Negative (PIN) diodes. By altering the connectivity of the vertical and horizontal gaps using the two PIN diodes, the open-loop-type square ring resonator can be used as a frequency switchable antenna. Using a similar method, a polarisation diversity antenna can be realised by independently adjusting the two PIN diodes inserted into diagonally placed gaps. In this latter case, the two polarisations are orthogonal to each other at the same frequency.

Single Front-End MIMO Architecture with Parasitic Antenna Elements

In recent years, wireless communication technology has been studied intensively. In particular, MIMO which employs several transmit and receive antennas is a key technology for enhancing spectral efficiency. However, conventional MIMO architectures require some transceiver circuits for the sake of transmitting and receiving separate signals, which incurs the cost of one RF front-end per antenna. In addition to that, MIMO systems are assumed to be used in low spatial correlation environment between antennas. Since a short distance between each antenna causes high spatial correlation and coupling effect, it is difficult to miniaturize wireless terminals for mobile use. This paper shows a novel architecture which enables mobile terminals to be miniaturized and to work with a single RF front-end by means of adaptive analog beam-forming with parasitic antenna elements and antenna switching for spatial multiplexing. Furthermore, statistical analysis of the proposed architecture is also discussed in this paper.

General Switch-and-Stay Combing for Space Diversity over Rayleigh Fading Channels

Three multibranch switch-and-stay combining (MSSC) schemes are analyzed for Rayleigh fading channels, where different decision statistics for antenna switching (i.e., switch statistic) are used. Letaandrdenote the fading factor and the received baseband signal of a diversity branch, respectively. In contrast to the traditional MSSC that uses the faded signal-to-noise ratio (SNR) of diversity branches as the corresponding switch statistic, to enhance the receiver performance,|r|,|ar|, and a new linear combination of a and|r|are used as switch statistics of the three MSSC schemes, respectively. For performance evaluation, the bit error rate (BER) of BPSK is derived for the three MSSC schemes over both independent-and-identical distributed (i.i.d.) and independent-and-nonidentical distributed (i.n.d.) Rayleigh fading channels. To pursue optimal performance, the locally optimal switch threshold (ST) of each MSSC scheme is obtained for generali.n.d.fading channels. In addition, the locally optimal ST becomes the globally optimal ST fori.i.d.channels. Numerical results based on the analysis and simulations are presented. In contrast to the MSSC overi.i.d.fading channels, we will show that the performance of MSSC schemes can be improved by increasing the number of branches, ifi.n.d.channels are considered.

Nonlinear Steady-State III–V FET Model for Microwave Antenna Switch Applications

A nonlinear III-V field-effect transistor model is proposed for designing microwave antenna switches and related circuits, off-state gate and drain capacitance values of a pseudo-morphic high-electron-mobility transistor (HEMT) derived from pulsed S-parameters with a deep OFF-state quiescent gate voltage are found to be much less voltage dependent than capacitance values measured by a nonpulsed bias owing to trap-induced dispersion effects. Our device model based on pulsed-bias CV characteristics accurately simulates switch nonlinearity. Both gate and drain capacitance values are assumed to be nonlinear, and a charge expression is developed for model implementation. For both capacitance values, a nonpulsed-bias CV curve is also utilized to maintain accurate capacitance at the quiescent voltage and, thus, accurate simulation of off-switch isolation. Additional terms are introduced to an existing drain current model to improve accuracy at high V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gs</sub> /low V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ds</sub> and subthreshold regions. Furthermore, the model is extended to multiple-gate devices. Harmonics generated from both OFF- and ON-state switches, insertion loss, and isolation are accurately predicted for both single- and multiple-gate HEMTs.

Switchable loop‐loaded printed dipole antenna with a balun/feed structure

AbstractA switchable loop‐loaded printed dipole antenna is introduced for a frequency‐tuning operation. Two loop elements with extensions are placed asymmetrically at each side of a twisted dipole excited by a balun/feed vertically placed underneath the dipole. PIN diodes are used between each loop element and its extension to achieve switchable antenna operation for 3 and 5.5 GHz bands. Simulated and measurement results are presented to demonstrate the proposed tuning performance. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:76–79, 2012, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26453

Measurement of the reflector antenna absorption at terahertz frequencies by the method of a balanced radiometer

The inherent noise of a prototype panel of the millimeter-wave telescope main reflector is measured at room temperature. A modulation radiometer based on a heterodyne detector with an input superconducting mixer and a balanced antenna switch is used. The noise temperature of the detector in the double-sideband mode equals 570 K at a local oscillator frequency of 842 GHz. The absorption factor of the aluminum panel calculated from the thermal radiation intensity is 0.31 ± 0.07%. This value is checked on samples made of phosphor bronze and stainless steel. The respective absorption factors are 0.41 ± 0.07 and 1.30 ± 0.07%, which are close to those obtained earlier for these materials using radiometers with direct-reading detectors. The wide dynamic range of the heterodyne detector simplifies calibration of the radiometer: there is no need to cool down the sensitive element below liquid helium temperature. A balanced switch of a new design makes it possible to radically suppress the influence of the background and take precision room-temperature measurements.

Training-Symbol Embedded, High-Rate, Single-Symbol ML-Decodable, Distributed STBCs for Relay Networks

Distributed space-time block codes (DSTBCs) from complex orthogonal designs (CODs) (both square and nonsquare), coordinate interleaved orthogonal designs (CIODs), and Clifford unitary weight designs (CUWDs) are known to lose their single-symbol ML decodable (SSD) property when used in two-hop wireless relay networks using amplify and forward protocol. For such networks, in this paper, three new classes of high rate, training-symbol embedded (TSE) SSD DSTBCs are constructed: TSE-CODs, TSE-CIODs, and TSE-CUWDs. The proposed codes include the training symbols inside the structure of the code which is shown to be the key point to obtain the SSD property along with the channel estimation capability. TSE-CODs are shown to offer full-diversity for arbitrary complex constellations and the constellations for which TSE-CIODs and TSE-CUWDs offer full-diversity are characterized. It is shown that DSTBCs from nonsquare TSE-CODs provide better rates (in symbols per channel use) when compared to the known SSD DSTBCs for relay networks. Important from the practical point of view, the proposed DSTBCs do not contain any zeros in their codewords and as a result, antennas of the relay nodes do not undergo a sequence of switch on/off transitions within every codeword, and, thus, avoid the antenna switching problem.

2$\,\times\,$2 Switch Matrix for WiMAX Relay Station Applications

A 2 × 2 Switch Matrix operating at the 3.3-3.8 GHz frequency band is presented. The design is based on PIN diode switch elements. The achieved isolation is below 80 dB, while the insertion loss is less than 2 dB for the full frequency band. The proposed 2 × 2 Switch Matrix is used as the antenna switching element in the RF Front-End of a WiMAX Relay Station, supporting both Time-domain Transmit and Receive and Simultaneous Transmit and Receive operation in Time Division Duplexing mode.

DOA Estimation Algorithm in Switch Antenna Array with a Single Cycle of Sampled Data

For DOA estimation of coherent signals in switch antenna array (SAA), a new fast algorithm is proposed. Instead of conventional sub-space algorithm’s covariance matrix, a Toeplitz matrix is constructed with a single cycle of sampled data. It is proved theoretically that the ranks of the Toeplitz matrix is equal to the number of signal sources and has no relations with the coherency of the signal source. Through eigenvalue decomposition, signal and noise subspace are obtained respectively, then DOA estimation can be done by one-dimensional spectral peak searching according to the MUSIC algorithm. The theoretical analysis and simulation results demonstrate validity and superiority of the novel algorithm.