understood, fact is that the first multicarrier techniques which were developed before the invention of OFDM used filter banks for synthesis and analysis of multicarrier signals. Such filter banks can be designed with small side-lobes, thus, are ideal choice in multiple access and cognitive radio applications . The first proposal came from Chang , who presented the conditions required for signaling a parallel set of pulse amplitude modulated (PAM) symbol sequences through a bank of overlapping filters within a minimum bandwidth. To transmit PAM symbols in a bandwidth e ﬃ cient manner, Chang’s signaling is based on staggering a number of overlapping vestigial side-band (VSB) modulatedsignal sequences. Saltzberg , extended the idea and showed how the Chang’s method could be modified for transmission of quadrature amplitude modulated (QAM) symbols, in a double side-band modulated format. Eﬃcient digital implementation of Saltzberg’s multicarrier system through polyphase structures first introduced by Bellanger et al. [9, 10], was studied by Hirosaki [11, 12], and was further developed by others [13–21]. Both Chang’s and Saltzberg’s methods belong to a class of multicarrier techniques that may be referred to as filter bank multicarrier (FBMC) systems.
Quadrature Phase Shift Keying (QPSK) has to do with splitting a quadrature stream as well as an in-phase stream in a situation where both the streams have half the bit rate of the data stream . The major problem with QPSK has been a sudden phase reversal due to the cosine and sine modulation function which can throw the amplifier into saturation causing non-linearity in the circuitry of the amplifier. Linear amplifiers aid in combating this sudden phase reversal but are expensive to setup . For this reason, the OffsetQuadrature Phase Shift Keying (OQPSK) comes to play. By using OQPSK both the phase and quadrature streams are offset in alignment meaning half a symbol period causing the envelope not to go to zero as it does with QPSK. OQPSK and continuous phase modulation have similar advantages of higher spectral efficiency than QPSK. In Continuous Phase Modulation (CPM) the carrier phase is modulated in a continuous manner with a constant transmit carrier power and doesn’t reset to zero at the start of every symbol as is the case with QPSK . The only drawback with CPM is the high implementation complexity required for an optimal receiver. The Additive white Gaussian noise (AWGN) models assume that the magnitude of a signal passing through it will vary randomly. The basic setup of this study is to modulate input signals using OQSPK and CPM in separate simulations, then pass them through the AWGN channel to estimate their bit error rates (BER).
ABSTRACT: OFDM (Orthogonal Frequency Division Multiplexing) is a multicarrier technique where linearly modulated data streams are divided into number of sub-streams each occupying a bandwidth less than the total bandwidth of the signal. Orthogonal frequency-division multiplexing/ offsetquadrature amplitude modulation with 64- quadrature amplitude modulation is selected as the modulation format to provide a “perfect” rectangular spectrum that efficiently reduces the channel crosstalk. No timing or frequency alignment is required for the sub bands to form the super channel. The modulation format of orthogonal frequency-division multiplexing based on offsetquadrature amplitude modulation (OFDM/OQAM) is selected to provide signal spectrum with high side-lobe suppression ratio, which can effectively reduce the electrical sub-band frequency interference. The optical fiber communication networks fulfill these requirements along with small attenuation loss and better quality of services.
1.728 MHz. The second low IF offers the advantage of easy implementation of filtering and amplifying stages and of implementing a completely digital demodulator. No external passive components are needed. The transmit chain consists of digital look-up table-based quadrature base-band Gaussian Minimum Shift Keyed (GMSK) signal generators followed by a quadra- ture modulator, translating base-band to 110.592 MHz. This frequency is very close to the re- ceive-chain IF, so no dual frequency synthesizer and wide band VCOs are needed. A second advantage is that the frequency deviation is precisely controlled. The IF signal is fed to an off- set Phase Locked Loop (PLL) followed by the small power amplifier (SPA). The SPA drives the external power amplifier. The offset PLL offers a number of advantages; Firstly, RF fil- tering is reduced, since no RF image frequency is present and the harmonic distortion of the RF VCO is low. Secondly, a large loop bandwidth, needed to track the GMSK modulated reference frequency, filters out-of-band signals and reduces VCO frequency pulling caused by switching power amplifiers.
Abstract— In the Modern day electronic fighting Systems the utilization of range has been broadened with a proficient way which makes the recognizable proof of the signal difficult. Modern radars use recurrence and stage tweaked signs to spread their range to enhance the handling gain. The way toward finding the balance arrangement of a perceived signal, the moderate development between signal distinguishing proof and demodulation, is an imperative task of a wise recipient, with various customary resident and military applications. Obviously, with no learning of the transmitted data and various cloud parameters at the authority, for instance, the signal control, carrier repeat and stage offsets, data, and so on., daze distinguishing proof of the adjustment is a troublesome assignment. This turns out to be considerably additionally difficult in certifiable situations. Wideband direct recurrence tweaked (LFM) signal is generally utilized in exact separation estimating radar framework. As customary techniques for creating LFM signal have a great deal of detriments, for example, shakiness and nonlinearity we propose an alternate answer for wideband LFM signal generator in L-band dependent on DDS and recurrence augmentation. The proposed strategy creates the baseband LFM signal utilizing the DDS, and after that includes the baseband motion into the recurrence duplication framework; last we can accomplish an unadulterated L-band wideband LFM signal. The estimation result demonstrates that the proposed can satisfy every prerequisite of anticipant palatably.
ABSTRACT: The filter bank multicarrier (FBMC) transmission system is an enabling technology for the new concepts and, especially, cognitive radio and it results into an enhanced physical layer for conventional networks. In this paper, we present an decision feedback equalizer based on RLS (Recursive Least Square) and LMS (Least Mean Square) algorithms at the sub-channel level for FBMC systems using exponentially modulated filter banks. The input to the FBMC system is offsetquadrature amplitude modulated (OQAM) input symbols. Simulation results exhibit that, in spite of its increased computational complexity, the FBMC/OQAM transmission technique provides better bit error rate performance.
The raw signal space SAR input is the two dimensional signal which also a LFM signal. The two dimensional signal is first analysed as a series range time signals for each azimuth bin. Each range time signal undergoes matched filtering in the range frequency/azimuth time domain through range FFTs applied to the range time signals. After each signal is transformed back into the range time/azimuth time domain, the result is the range compressed signal as the matched filtering was performed in the range frequency domain. In order to obtain azimuth compression, azimuth matched filtering must be performed. The range compressed signal is then composed into a series of signals with respect to azimuth time at different range bins.
Figure 1. Top part. The gravitational-wave event GW150914 observed by the LIGO Hanford ( H 1, left column panels) and Livingston ( L 1, right column panels) detectors. Times are shown relative to September 14, 2015 at 09:50:45 UTC. For visualization, all time series are filtered with a 35 - 350 Hz band-pass filter to suppress large fluctuations outside the detectors’ most sensitive frequency band, and band-reject filters to remove the strong instrumental spectral lines . Declared time of the entry signal (0.39 s) indicated by blue circles  . Numbers and frequencies of wave phases (left): The true signal entry into 0.33 s (green circle). Bottom part: Experimental templates on observatories s H ( ) t
Nyquist folding receiver (NYFR) is a novel ultra-wideband receiver architecture which can realize wideband receiving with a small amount of equipment. Linear frequency modulated/binary phase shift keying (LFM/BPSK) hybrid modulatedsignal is a novel kind of low probability interception signal with wide bandwidth. The NYFR is an effective architecture to intercept the LFM/BPSK signal and the LFM/BPSK signal intercepted by the NYFR will add the local oscillator modulation. A parameter estimation algorithm for the NYFR output signal is proposed. According to the NYFR prior information, the chirp singular value ratio spectrum is proposed to estimate the chirp rate. Then, based on the output self-characteristic, matching component function is designed to estimate Nyquist zone (NZ) index. Finally, matching code and subspace method are employed to estimate the phase change points and code length. Compared with the existing methods, the proposed algorithm has a better performance. It also has no need to construct a multi-channel structure, which means the computational complexity for the NZ index estimation is small. The simulation results demonstrate the efficacy of the proposed algorithm.
worldwide for various applications while there is a problem identified in higher data transmission rate communication is intersymbol interference (ISI). ISI appears when there is interference at transmission side and the receiver cannot decode the transmission precisely. For example, in a wireless communication system, the same transmission is sent in all directions. In multipath distant transmission the transmitted information signal is reflected from middle objects for example hills, mountains or residential area, the receiver recieves many replicas of signal. In communication system, this phenomenon is called multipath. Because the reflected multipaths consume much time to reach the receiver, the delayed replicas of the original signal intersect with the linear signal, resulting into an ISI ( Intersymbol Interference).
David Cowell gained his doctorate from the School of Electronic and Electrical Engineering at the Uni- versity of Leeds in 2008 working with the Ul- trasound Group. His doctoral research area was advanced coding excitation techniques and excita- tion circuit design for industrial instrumentation and medical imaging systems. During this time he has performed extensive consultancy in instrumentation, FPGA and high-speed digital hardware design. After working as a research consultant in measurement and instrumentation, he joined the Ultrasound Group as a Research Fellow. His main research is currently focused on non-invasive industrial ultrasound measurement. His other active research areas include advanced miniaturized ultrasound excitation systems with low harmonic distortion for phased array imaging, ultrasound system design and signal processing.
Then, the first complex signal and the second complex signal are constructed from in-phase channel signal and quadrature channel signal. The construction method are the same, i.e. The data whose n 3 / 4 are picked to be as the real part, the rest are as the image part. The fist complex signal and the second complex signal are as follows:
Essential tremor is a disorder that causes involuntary oscillations in patients both while they are engaged in actions and when maintaining a posture. Such patients face serious difficulties in performing daily living activities such as meal movement. We have been developing an electromyogram (EMG)-controlled exoskeleton to suppress tremors to support the movements of these patients. The problem is that the EMG signal of the patients is modulated by the tremor signal as multiplicative noise. In this paper, we proposed a novel signal processing method to demodulate patients’ EMG signals. We modelled the multiplicative tremor signal with a powered sine wave and the tremor signal in the EMG signal was removed by dividing the modelled tremor signal into the EMG signal. To evaluate the effective- ness of the demodulation, we applied the method to a real patient’s EMG signal, extracted from biceps brachii while performing an elbow flexion. We quantified the effect of the demodulation by root mean square error between two kinds of muscle torques, an estimated torque from the EMG signal and calculated torque from inverse dynamics based on the motion data. The proposed method succeeded in reducing the error by approximately 15–45% com- pared with using a low-pass filter, typical processing for additive noise, and showed its effectiveness in the demodula- tion of the patients’ EMG signal.
The block diagram in figure fig.1 given here describe for transmitter in traffic light shown in figure. Functionality of each block described next. Microcontroller read data from control station. Information is transmitted to the traffic signal and VLC transmitter which is inserted in traffic signal. Thus information is passed as signal to vehicles. Here the system is categorized to two parts section A describes about Light Fidelity communication and section B describes about wireless communication. Section A is for traffic light and vehicles and B for vehicular communications. Figure fig.2 above shows the receiver section for infrastructure to vehicle here a VLC receiver used to receive information from VLC transmitter. A power supply is needed in both transmitter and receiver, but different amount of power needed for each component.
frequencies. Modulating a sine wave carrier makes it possible to keep the frequency content of the transferred signal as close as possible to the centre frequency (typically the carrier frequency) of the pass band. When coupled with demodulation, this technique can be used to, among other things, transmit a signal through a channel which may be opaque to the baseband frequency range (for instance, when sending a telephone signal through a fiber-optic strand). In music synthesizers, modulation may be used to synthesis waveforms with a desired overtone spectrum. In this case the carrier frequency is typically in the same order or much lower than the modulating waveform. See for example frequency modulation synthesis or ring modulation. A device that performs modulation is known as a modulator and a device that performs the inverse operation of modulation is known as a demodulator. A device that can do both operations is a modem[2-4].
and trigger signal is shown in Figure7. Parameter configuration and acquisition process of acquisition card are shown in Figure8. A acquisition process is divided into 3 step in sequence structure, the first step and the second one acquite IF signals in the rising and falling phase of triangular wave separately. A few controllers beside the sequence structure configure the initial parameters for the card. Parameter configuration VI (AI Config) designates the card to equipment No.1, channel No.0 and buffer size 1000 by forward controls palette. AI start can start one time acquisition according to the designated sampling frequency and points(#S). AI start can set trigger type and slope simultaneously.The trigger type is set as digital A(using digital trigger), the slope is set as rising edge trigger at the first step and the slope is set as falling edge trigger at second.It can be read out of the acquited data from computer buffer, and these data are sent to the later step to measure frequency. AI clear is to stop acquisition and release buffer and on-board resource.
Figure 1 shows the proposed structure of 1-8GHz phase shifter employed vector synthesized technology, it includes quadraturesignal generator, gain amplifier and signal combiner, where the quadraturesignal generator produces four pairs of orthogonal differential signals. The signal combiner uses the Gilbert cell circuit to amplify the gain while performing polarity selection. The logic encoder encodes the five-bit digital control signal input from the outside, its output is used to control the DAC conversion circuit. DAC conversion circuit sent the analog signal generated by logic encoder control signals into input terminal of the signal combiner to complete the phase modulation. Since the circuit uses less passive devices, it is more high integrated and suitable for wideband application.
The spectral purity of the final analog output signal is determined primarily by the DAC. The phase noise is basically that of the reference clock. The heart of the system is the phase accumulator whose contents are updated once each clock cycle. Each time the phase accumulator is updated, the digital number, M, stored in the phase register is added to the number in the phase accumulator register. Assume that the number in the delta phase register is 00...01 and that the initial contents of the phase accumulator are 00...00. The phase accumulator is updated by 00...01 on each clock cycle. If the accumulator is 32-bits wide, 2 32 clock cycles (over 4 billion) are required before the phase accumulator returns to 00...00, and the cycle repeats. The truncated output of the phase accumulator serves as the address to a sine (or cosine) lookup table. Each address in the lookup table corresponds to a phase point on the sine wave from 0° to 360°. The lookup table contains the corresponding digital amplitude information for one complete cycle of a sine wave. (Actually, only data for 90° is required because the quadrature data is contained in the two MSBs). The lookup table therefore maps the phase information from the phase accumulator into a digital amplitude word, which in turn drives the DAC.
Abstract. Direct digital synthesis (DDS) is widely used in radar signal generation. In order to study the influence of phase truncation on signal processing, this paper models DDS to generate linear frequency modulated (LFM) signal, and accomplishes pulse compression based on systemvue. Based on phase truncation spurs of the single-tone sinusoidal signal, spurious components of LFM signals generated by DDS are analyzed qualitatively. Simulations graphically demonstrate that, these spurs decrease signal to noise ratio after pulse compression. To avoid effect of these spurs, proper parameters of DDS are provided for radar systems.