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space-time modulation of a Multimode Electrically Small Antenna for Increased Matching and Efficiency Bandwidths

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2025年第3期73卷 1308-1320页

作者： Fritts, Zachary Babaee, Amirhossein Young, Steve M. Grbic, Anthony Univ Michigan Dept Elect & Comp Engn Ann Arbor MI 48109 USA

In this work, a method for increasing the efficiency-bandwidth product of an electrically small antenna (ESA) by using spatially discrete traveling-wave modulation (SDTWM) is introduced. This method applies generally to electrically small antennas possessing N-fold rotational symmetry. To illustrate the method, it is applied to a top-hat loaded monopole antenna that supports a fundamental radiating mode as well as non-radiating modes that are analogous to discrete orbital angular momentum (OAM) modes. time-modulated capacitors, placed in each sector, couple these modes using SDTWM. The modulation scheme is similar to that of a classic negative-resistance parametric amplifier, but instead of using the modulation to obtain gain from the system, the modulation parameters are chosen to enhance the matching bandwidth of the antenna. We show how this can be done by choosing an appropriate combination of the modulation depth and modulation frequency. After extending the definition of radiation efficiency and mismatch loss to the case of a parametrically time-varying antenna, the extended definitions are used to characterize the simulated performance of the time-varying antenna under two different SDTWM modulation schemes. The first modulation scheme couples the radiative mode to a single non-radiative mode, while the second modulation scheme couples the radiative mode to two different non-radiative modes. Both schemes yield efficiency-bandwidth products that are 6.4-7.6 dB larger than that of the time-invariant version of the antenna.

关键词： Antennas Loaded antennas Helical antennas Bandwidth Integrated circuit modeling Capacitors Antenna radiation patterns Linear systems Couplings Q-factor Efficiency-bandwidth product electrically small antennas impedance matching interpath relation time-varying systems space-time modulation

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Noncoherent receivers for differential space-time modulation

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IEEE TRANSACTIONS ON COMMUNICATIONS 2002年第5期50卷 768-777页

作者： Schober, R Lampe, LHJ Univ British Columbia Dept Elect & Comp Engn Vancouver BC V6T 1Z4 Canada Univ Toronto Dept Elect & Comp Engn Toronto ON M5S 3G4 Canada Univ Erlangen Nurnberg Chair Informat Transmiss D-91058 Erlangen Germany

In this paper, noncoherent receivers for differential space-time modulation (DSTM) are investigated. It is shown that the performance of the previously proposed conventional differential detection (DD) receiver is satisfactory only for very slow flat fading channels. However, conventional DD suffers from a considerable loss in performance even for moderately fast fading, especially if more than one transmit antenna is used. In order to overcome this problem, two improved noncoherent receivers are considered. The first one is the multiple-symbol detection (MSD) receiver. Because of the high computational complexity of MSD, also a low-complexity decision-feedback differential detection (DF-DD) receiver is derived. Analytical and simulation results confirm that both receivers perform equally well and can take full advantage of the enhanced diversity provided by multiple transmit antennas even for fast fading.

关键词： decision-feedback differential detection fading channels multiple-symbol detection space-time modulation transmit and receive diversity

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Multisampling decision-feedback linear prediction receivers for differential space-time modulation over Rayleigh fast-fading channels

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IEEE TRANSACTIONS ON COMMUNICATIONS 2003年第7期51卷 1214-1223页

作者： Ling, C Li, KH Kot, AC Zhang, QT Nanyang Technol Univ Sch Elect & Elect Engn Singapore 639798 Singapore City Univ Hong Kong Dept Elect Engn Kowloon Hong Kong Peoples R China

Novel decision-feedback (DF) linear prediction (LP) receivers, which process multiple samples per symbol interval in conjunction with optimal sample combining, are proposed for differential space-time modulation (DSTM) over Rayleigh fast-fading channels. Performance analysis demonstrates that multisampling DF-LP receivers outperform their symbol-rate sampling counterpart in fast fading substantially. In addition, an asymptotically tight upper bound on the pairwise error probability is derived. In view of this bound, the design criterion of DSTM for fast fading is the same as that for block-wise static fading. To avoid the estimation of the second-order statistics of the channel, A polynomial-model-based DF-LP receiver is proposed. It can approach the performance of the optimum DF-LP receiver at high signal-to noise ratios, provided fading is moderate.

关键词： differential detection diversity combining linear prediction (LP) space-time modulation time-selective fading

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Coded unitary space-time modulation with iterative decoding: Error performance and mapping design

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IEEE TRANSACTIONS ON COMMUNICATIONS 2007年第4期55卷 703-716页

作者： Tran, Nghi H. Nguyen, Ha A. Le-Ngoc, Tho Univ Saskatchewan Dept Elect Engn Saskatoon SK S7N 5A9 Canada McGill Univ Dept Elect & Comp Engn Montreal PQ H3A 2A7 Canada

This paper studies the bit error probability of coded unitary space-time modulation with iterative decoding where neither the transmitter nor the receiver knows the channel fading coefficients. The tight error bound with respect to the asymptotic performance is first analytically derived for any given unitary constellation and mapping rule. Design criteria regarding the choice of unitary constellation and mapping are then established. Furthermore, using the unitary constellation obtained from orthogonal design with quadrature phase-shift keying (QPSK or 4-PSK) and 8-PSK, two different mapping rules are proposed. The first mapping rule gives the most suitable mapping for systems that do not implement iterative processing, which is similar to a Gray mapping in coherent channels. The second mapping rule yields the best mapping for systems with iterative decoding. In particular, analytical and simulation results show that with the proposed mappings of the unitary constellations obtained from orthogonal designs, the asymptotic error performance of the iterative systems can closely approach a lower bound which is applicable to any unitary constellation and mapping.

关键词： bit-interleaved coded modulation (BICM) error bound error performance iterative decoding signal mapping space-time modulation unitary constellation

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Effective SNR for space-time modulation over a time-varying rician channel

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IEEE TRANSACTIONS ON COMMUNICATIONS 2004年第1期52卷 17-23页

作者： Peel, CB Swindlehurst, AL Brigham Young Univ Dept Elect & Comp Engn Provo UT 84602 USA

Rapid temporal variations in wireless channels pose a significant challenge for space-time modulation and coding algorithms. This letter examines the performance degradation that results when time-varying flat fading is encountered when using trained and unitary space-time modulation. Performance is characterized for a channel having a constant specular component plus a time-varying diffuse component. A first-order autoregressive (AR) model is used to characterize diffuse channel coefficients that vary from symbol to symbol, and is shown to lead to an effective signal-to-noise ratio (SNR) that decreases with time. Differential modulation is shown to have an advantage in effective SNR over trained unitary modulation at high power. Simulation results are provided to support our analysis.

关键词： differential modulation fading channels multiple antennas space-time modulation time-varying channels trained modulation wireless communications

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Mixer-Duplexer- Antenna Leaky-Wave System Based on Periodic space-time modulation

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION 2017年第2期65卷 442-452页

作者： Taravati, Sajjad Caloz, Christophe Ecole Polytech Montreal Poly Grames Res Ctr Dept Elect Engn Montreal PQ H3T 1J4 Canada

We present a mixer-duplexer-antenna leaky-wave system based on periodic space-time modulation. This system operates as a full transceiver, where the upconversion and down-conversion mixing operations are accomplished via space-time transitions;the duplexing operation is induced by the non-reciprocal nature of the structure, and the radiation operation is provided by the leaky-wave nature of the wave. A rigorous electromagnetic solution is derived for the dispersion relation and field distributions. The system is implemented in the form of a spatio-temporally modulated microstrip leaky-wave structure incorporating an array of subwavelengthly spaced varactors modulated by a harmonic wave. In addition to the overall mixer-duplexer-antenna operation, frequency beam scanning at fixed input frequency is demonstrated as one of the interesting features of the system. A prototype is realized and demonstrated by full-wave and experimental results.

关键词： Duplexer leaky-wave antenna mixer nonreciprocity space-time modulation transceiver

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Millimeter-Wave Angle Estimation of Multiple Targets Using space-time modulation and Interferometric Antenna Arrays

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IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 2021年第11期69卷 5126-5134页

作者： Vakalis, Stavros Nanzer, Jeffrey A. Michigan State Univ Dept Elect & Comp Engn E Lansing MI 48824 USA

A new method of angle estimation of multiple targets using a distributed interferometric antenna array and wideband space-time modulation generating a dynamic array pattern is presented in this work. Interferometric array measurements of angle of arrival are generally ambiguous in the presence of two or more targets. We propose a new method of mitigating ambiguities in interferometric measurements by multiplying the angle pseudo-spectra from multiple antenna baselines, resulting in detections at only the angles of the targets. Using a single linear frequency-modulated transmitter and a receive interferometric array with N elements, we show a simple and computationally efficient technique to estimate the angle of up to O(N-2) targets. We describe the theory behind the technique, present detailed simulations, and provide an experimental verification using a three-element millimeter-wave measurement system.

关键词： Angle estimation correlator arrays dynamic arrays interferometric antenna arrays interferometry radar space-time modulation target detection

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Fast differential unitary space-time modulation decoding for a MIMO radio channel

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WIRELESS PERSONAL COMMUNICATIONS 2003年第4期25卷 343-349页

作者： Smith, DB Univ Technol Sydney Fac Engn Telecommun Sydney NSW 2007 Australia

Improved decoding efficiency is achieved for differential unitary space-time modulation across a multiple-input multiple-output ( MIMO) channel. The group nature of constellations used for signal transmission, and hence a minimised search space for maximum likelihood (ML) decoding are utilised to give this improvement. A procedure using lattice reduction for fast decoding across a multiple-input single-output ( MISO) channel is generalised to a MIMO channel effectively, as a modification to a previous proposal, and used to generate the ML decoder search space. Further insight into the application of this algorithm is given. The decoding technique developed is shown to have very good error performance for reasonably sized MIMO channels.

关键词： differential modulation fading channels space-time modulation fast decoding multiple antennas

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Effects of Non-Identical Rayleigh Fading on Differential Unitary space-time modulation

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IEEE TRANSACTIONS ON COMMUNICATIONS 2009年第5期57卷 1359-1369页

作者： Tao, Meixia Shanghai Jiao Tong Univ Dept Elect Engn Shanghai 200240 Peoples R China

Non-identical fading distribution in a multiple-input multiple-output (MIMO) channel, including unequal average channel gains and fade rates, often occurs when antennas are not co-located. In this paper, we present an analytical study of the effects of non-identical Rayleigh fading on the error performance of differential unitary space-time modulation (DUSTM). The fading processes for different transmit-receive antenna pairs are assumed to be independent and time-variant. We find that the maximum-likelihood (ML) differential detector of DUSTM over such channels is involved except for differential cyclic group codes. The conventional detector is proved to be asymptotically optimal in the limit of high signal-to-noise ratio (SNR) over static fading channels. Applying the distribution of quadratic forms of Gaussian vectors, we then derive closed-form expressions for the exact error probabilities of two specific unitary classes, namely, cyclic group codes and orthogonal codes. Simple and useful asymptotic bounds on error probabilities are also obtained. Our analysis leads to the following general findings: (1) equal power allocation is asymptotically optimal, and (2) non-identical channel gain distribution degrades the error performance. Finally, we also introduce a water-filling based power allocation to exploit the transmit non-identical fading statistics.

关键词： Differential detector error probability analysis independent and non-identical channels Rayleigh fading space-time modulation

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DPC Rates and Multiplexing Gains for MIMO Broadcast Systems with Multi-Dimensional space-time modulation

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IEEE TRANSACTIONS ON COMMUNICATIONS 2011年第3期59卷 639-647页

作者： Kassouf, Marthe Leib, Harry McGill Univ Dept Elect & Comp Engn Montreal PQ H3A 2A7 Canada

This paper considers multiple-antenna broadcast channels (BCs) with multi-dimensional space-time modulation schemes, created by various allocations of signal dimensions to transmit antennas. The signal dimensions are divided into disjoint subsets, where one is shared between all users, and each of the others are assigned to different users. This model encompasses several practical single point to multi-point wireless communication systems employing multiple antennas. Assuming space and time dispersive channels, we consider the transmission rates that are achieved by applying dirty paper coding (DPC) at the transmitter, present inner and outer bounds for the DPC rate region, and study the effects of space-time modulation formats. At high SNR, we consider the limit form of these bounds, derive an achievable multiplexing gain region, and study the effects of sharing signal dimensions between users.

关键词： Multiple-input multiple-output (MIMO) broadcasting systems space-time modulation dirty paper coding (DPC) multiplexing gain

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