4-D Arrays as Enabling Technology for Cognitive Radio Systems

Rocca, Paolo; Zhu, Qingxin; Bekele, Ephrem T.; Yang, Shiwen; Massa, Andrea

doi:10.1109/tap.2013.2288109

Cited by 151 publications

(61 citation statements)

References 42 publications

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“…For example, consider a signal whose bandwidth is B. Thus, the maximum bandwidth B of the signal radiated by the time-modulated antenna is usually set as B < f p (TM frequency), to avoid the aliasing effects (overlapping of modulated signal spectrum) [4], [27], [32]. However, the maximum bandwidth B of the signal radiated by the singlesideband time-modulated phased array turns out to be B < 4f p , as shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

Single-Sideband Time-Modulated Phased Array

Yao

Fang

2015

IEEE Trans. Antennas Propagat.

123

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A new in-phase/quadrature (I/Q) complex modulation technique to realize single-sideband time-modulated phaseonly weighting on an array antenna is proposed. Based on modulating rectangular pulses and trapezoidal pulses, the theories of generating a scanning beam at the single positive sideband are presented. It was found that using trapezoidal pulse modulation can obtain excellent performance in power efficiency and undesired sideband level than using rectangular pulse modulation. Unlike conventional time-modulated antenna array where each array element is connected to a RF switch, in the proposed scheme, each element is connected to an I/Q channel modulator which is composed of two Wilkinson power dividers, two RF switches, two 0/π phase shifters in RF channels, and one π/2 fixed-phase shifter in the control circuit. By properly controlling both the phase shifters and the switches in time domain, the single-sideband modulation can be realized with the uniform amplitude and variable phase in frequency domain. The I/Q modulator acts as a phase shifter and can be used to form a phased array. In this paper, the main efforts have been paid to find the pulse sequences to suppress the spurious bands. To validate the proposed technique, simulated results of an eight-element single-sideband time-modulated linear array obtained from the array factor and full-wave analysis are reported. In the case of using rectangular pulses, the power efficiency of the scanning beam is 91.47% and the peak level of the highest undesired harmonic is −13.98 dB. In the case of using trapezoidal pulses, the best values can reach 99.79% and −27.98 dB.Index Terms-In-phase/quadrature (I/Q) complex modulation, phased array, single-sideband time-modulated phase-only weighting, time-modulation (TM) technique.

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Section: Discussionmentioning

confidence: 99%

Single-Sideband Time-Modulated Phased Array

Yao

Fang

2015

IEEE Trans. Antennas Propagat.

123

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“…Assume that the sampling frequency is , and data points are sampled to calculate and , which are written as . Then, and are calculated by (8) As shown in (8), the number of the multiply-add operation to calculate and is . Compared to other direction-finding methods, such as the spatial spectrum estimation method, the calculation amount of the proposed method is small.…”

Section: Theorymentioning

confidence: 99%

“…Because of the periodical modulation, the power of RF signal is distributed along both the fundamental and harmonic components. Recently, the research about TMAs mainly focused on ultra-low sidelobe level (SLL) pattern synthesis [6], the beamforming [7], [8], and the direction finding [9]. The direction-finding property of TMAs was first proposed in [4] by analyzing the relationship between the pattern of the first harmonic component and the mark-to-space ratio of the modulation signal.…”

Section: Introductionmentioning

confidence: 99%

Direction Finding by Time-Modulated Array With Harmonic Characteristic Analysis

Liang

et al. 2015

Antennas Wirel. Propag. Lett.

106

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A novel direction-finding method by the time-modulated array (TMA) is proposed through analyzing the harmonic characteristic of received signal, which requires only two antenna elements and a single RF channel. The signal processing of the proposed method is concise, and its calculation amount concentrates on a two-point discrete Fourier transform (DFT). Numeric simulations are provided to examine the performance of the proposed method, and a simple S band two-element TMA is constructed and tested to verify its effectiveness.

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“…In 2012, Tong and Tennant proposed a two-channel TMA with adaptive beamforming [6]. In 2014, Rocca et al analyzed the harmonic beams of the TMA pointing to different directions and provided the sketch of the 4-D arrays with TMAs [7]. In the above literature, the harmonic radiations generated by the TMA and their patterns are analyzed and optimized, which makes contribution to the potential application of the TMA in the multiple users communication.…”

Section: Introductionmentioning

confidence: 99%

Space-Division Multiple Access Based on Time-Modulated Array

Liang

Zhou

et al. 2015

Antennas Wirel. Propag. Lett.

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A novel space-division multiple-access (SDMA) method is proposed by the multibeam characteristic of the time-modulated array (TMA). The TMA generates the fundamental and harmonic components pointing to different directions. For the uplink, the users in different directions transmit the signals with the same carrier frequency to the base station with the TMA. Then, the base station distinguishes the users by the generated harmonic components. For the downlink, signals of different users are modulated to different carrier frequencies beforehand. Because of the modulation of the TMA, the downlink signals are transmitted to different directions with the same carrier frequency. Compared to the traditional SDMA systems implemented by the Butler matrix beamforming or the digital beamforming, the proposed method implements the SDMA with a single RF channel, which has advantage in the hardware complexity and cost. The uplink and downlink schemes are analyzed, and their drawbacks are discussed. A simple TMA is constructed to verify its effectiveness.

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4-D Arrays as Enabling Technology for Cognitive Radio Systems

Cited by 151 publications

References 42 publications

Single-Sideband Time-Modulated Phased Array

Single-Sideband Time-Modulated Phased Array

Direction Finding by Time-Modulated Array With Harmonic Characteristic Analysis

Space-Division Multiple Access Based on Time-Modulated Array

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