Multi-carrier Frequencies Research Articles

Photonic-based dual-chirp microwave waveforms generation with multi-carrier frequency and large time-bandwidth product

Photonic-based dual-chirp microwave waveform generation with multi-carrier frequencies and large time-bandwidth product (TBWP) is proposed. In the approach, a polarization modulator is employed to introduce parabolic phase difference into the injected optical signals. After heterodyne detection in balanced photodetector, dual-chirp microwave waveforms with multi-carrier frequencies are generated. To remedy the TBWP limitation, approach based on splitting parabolic waveform is employed to increase the bandwidth of the generated waveforms while controlling the temporal duration unchanged. The generator features multi-band generation ability and large TBWP performance. Simulations show that bandwidth of the generated signals are increased by N/2 times after splitting the parabolic waveform into N pieces. Four-band dual-chirp signals with bandwidth of 7.32 GHz and TWBP of 6000 are generated. Auto-correlations of the generated waveforms exhibit good pulse compression performance. Ambiguity functions of the generated signals are analyzed, polarization offsets and approach limitations are also investigated.

Photonic generation of multi-frequency dual-chirp microwave waveform with multiplying bandwidth

Abstract A photonic approach to generate dual-chirp microwave waveform with multi-carrier frequencies and multiplying bandwidth is proposed and demonstrated by using a dual-polarization Mach-Zehnder modulator (DPol-MZM) and balanced detection. In the approach, the DPol-MZM driven by a baseband waveform modulates the injected optical signal to generate optical broad-spectra sidebands. After heterodyne in balanced photodetector (BPD), multi-frequency dual-chirp microwave waveform can be generated. The proposed generator allows the injected optical signal with arbitrary intensity modulation format. The key features of the approach are the multi-carrier frequencies generation ability and the bandwidth multiplying operation. The proposed approach is verified by simulation. Dual-chirp signal with four-carrier frequencies is generated by employing optical frequency comb (OFC) with five comb lines. Auto-correlations of the generated signals show good pulse compression ratio and high peak-to-sidelobe ratio. The maximum frequency number of the system is analyzed, and the maximum power ratio is also investigated.

Combined root‐MUSIC algorithms for multi‐carrier MIMO radar with sparse uniform linear arrays

In this study, sparse uniform linear arrays are used to improve the direction-of-arrival (DOA) estimation accuracy for the multiple-input multiple-output radar. With a suitable choice of multi-carrier frequencies, the DOA estimation ambiguity problem caused by spatial under-sampling can be resolved. Two kinds of search-free DOA estimation algorithms based on root-multiple signal classification (MUSIC) are proposed. The first algorithm directly applies the root-MUSIC to each carrier frequency separately for the true DOAs as well as their spurious DOAs, then, a novel DOA replicas matching algorithm is proposed to obtain the true DOAs from the ambiguous ones. The second algorithm utilises the manifold separation technique (MST) to align the noise subspaces of all multi-carrier frequencies. Using the MST, the separable representation of the array manifold vector of each carrier frequency is obtained, then the root-MUSIC polynomials of all multi-carrier frequencies are combined to construct a new polynomial, the true DOAs can be obtained directly by applying polynomial rooting without any matching processing. The two proposed algorithms are both practical, computationally efficient and robust. Numerical simulations verify the effectiveness of the proposed algorithms in terms of root-mean-squared error.

120 Gb/s Wireless Terahertz-Wave Signal Delivery by 375 GHz-500 GHz Multi-Carrier in a 2 × 2 MIMO System

We propose and experimentally demonstrate a photonics-aided 2 × 2 multiple-input multiple-output (MIMO) wireless Terahertz-wave (THz-wave) signal transmission system, which realizes 6 × 20-Gb/s six-channel polarization division multiplexing quadrature-phase-shift-keying THz-wave signal delivery over 10-km wireline single-mode fiber- link and 142-cm wireless 2 × 2 MIMO link with a bit-error ratio under the hard-decision forward-error-correction threshold of 3.8 × 10−3. Our employed multi-carrier frequencies are located within the range of 375 GHz to 500 GHz. To the best of our knowledge, this is the first experimental demonstration of 2 × 2 MIMO wireless transmission of multi-channel THz-wave signal. Here, it is worth noting that our wireless 2 × 2 MIMO link, which offers point-to-point straight transmission and brings neither interference nor gain, is different from the traditional MIMO link defined in the field of wireless communications.

OFDM Scheme for Data Transmission Over Inductive Channels

Although OFDM has become a widely used method for transmitting digital data on multicarrier frequencies in wideband digital communication, this scheme has barely been used for near field inductive communication. Therefore, in this paper, OFDM is applied to three inductive communication systems including two, three and four node systems in order to transmit data over inductive channels. Furthermore, the channel responses for these three circuits are analysed in details to clarify the accurate inductive channels for data transmission that were defined alternatively in other papers. Besides, the effects of second neighbour interaction on inductive systems are also included in this work. More importantly, the OFDM scheme has been simulated in MATLAB and implemented in MATLAB SIMULINK in order to verify the method in either theory or practice. The BER versus SNR performances obtained by simulation and implementation are compared with the theoretical results to verify the data transmission errors.

Design and Performance Analysis of a Multiuser OFDM Based Differential Chaos Shift Keying Communication System

In this paper, a multiuser OFDM-based chaos shift keying (MU OFDM-DCSK) modulation is presented. In this system, the spreading operation is performed in time domain over the multicarrier frequencies. To allow the multiple access scenario without using excessive bandwidth, each user has $N_P$ predefined private frequencies from the $N$ available frequencies to transmit its reference signal and share with the other users the remaining frequencies to transmit its $M$ spread bits. In this new design, $N_P$ duplicated chaotic reference signals are used to transmit $M$ bits instead of using $M$ different chaotic reference signals as done in DCSK systems. Moreover, given that $N_P , the MU OFDM-DCSK scheme increases spectral efficiency, uses less energy and allows multiple-access scenario. Therefore, the use of OFDM technique reduces the integration complexity of the system where the parallel low pass filters are no longer needed to recover the transmitted data as in multicarrier DCSK scheme. Finally, the bit error rate performance is investigated under multipath Rayleigh fading channels, in the presence of multiuser and additive white Gaussian noise interferences. Simulation results confirm the accuracy of our analysis and show the advantages of this new hybrid design.

An Estimation Method for number of carrier frequency

This paper proposes a method that utilizes AR model power spectrum estimation based on Burg algorithm to estimate the number of carrier frequency in single pulse. In the modern electronic and information warfare, the pulse signal form of radar is complex and changeable, among which single pulse with multi-carrier frequencies is the most typical one, such as the frequency shift keying (FSK) signal, the frequency shift keying with linear frequency (FSK-LFM) hybrid modulation signal and the frequency shift keying with bi-phase shift keying (FSK-BPSK) hybrid modulation signal. In view of this kind of single pulse which has multi-carrier fre- quencies, this paper adopts a method which transforms the complex signal into AR model, then takes power spectrum based on Burg algorithm to show the effect. Experimental results show that the estimation method still can determine the number of carrier frequencies accurately even when the signal noise ratio (SNR) is very low.

Two-way communication over gas pipe-line using multicarrier modulated sound waves with cyclic frequency shifting

In recent years, several studies on acoustic communication systems utilizing gas pipe lines have been carried out. However, in conventional acoustic communication technology, the transmission rate cannot be improved because of the reverberant signals arising from reflections at the bends and branches in pipes. To reduce the effect of the reverberant signals and to improve the transmission data rate, we studied a multi-carrier modulation system. In this study, to avoid intersymbol interference, we employed special modulation symbols composed of multicarrier frequencies which change cyclically. To evaluate the proposed system, we constructed an experimental setup simulating a pipe system equivalent to that of a six-story building as a communication path. We achieved a transmission rate of 3,840 bps using the proposed method.