FM Signal Research Articles

Target Motion Parameters Estimation in Forward Scatter Radar

This paper is devoted to the estimation of target motion parameters with a forward scatter radar (FSR). To provide an upper bound for the estimation performance, a closed-form expression of the Cramer–Rao lower bound (CRLB) is provided for the main target signal parameters, namely Doppler rate, baseline crossing instant, and main lobe width parameter of the target amplitude modulation pattern. This is performed by operating on the signal at the output of the standard FSR processing scheme, namely on the crystal video detector signal: the received signal, which is passed through a square-law envelope detector followed by a DC removal filter. The estimate of the kinematic parameters of moving targets that follow a linear trajectory can be obtained by inverting the relationship between these parameters and the previously estimated target signal parameters. Especially, two FSR configurations are investigated: single-node FSR configuration and dual-baseline FSR configuration with a small angular separation between the two baselines. The closed-form expression of the corresponding CRLB is derived by using a linearized version of the same inverse transformation. Finally, a practical estimator is presented, based on a two-dimensional filter bank, and its performance is compared with the derived CRLB. The results show that unbiased and highly accurate estimates of the kinematic parameters are obtained. The feasibility and the effectiveness of this estimation scheme is demonstrated by applying this technique to recorded live data acquired with a dual-baseline FSR configuration exploiting FM signals as a waveform of opportunity.

Efficient Implementation of Multichannel FM and T-DMB Repeater in FPGA with Automatic Gain Controller

In this study, we implemented a high-performance multichannel repeater, both for FM and T-Digital Multimedia Broadcasting (DMB) signals using a Field Programmable Gate Array (FPGA). In a system for providing services using wireless communication, a radio-shaded area is inevitably generated due to various obstacles. Thus, an electronic device that receives weak or low-level signals and retransmits them at a higher level is crucial. In addition, parallel implementation of digital filters and gain controllers is necessary for a multichannel repeater. When power level is too low or too high, the repeater is required to compensate the power level and ensure a stable signal. However, analog- and software-based repeaters are expensive and they are difficult to install. They also cannot effectively process multichannel in parallel. The proposed system exploits various digital signal-processing algorithms, which include modulation, demodulation, Cascaded Integrator Comb (CIC) filters, Finite Impulse Response (FIR) filters, Interpolated Second Ordered Polynomials (ISOP) filters, and Automatic Gain Controllers (AGCs). The newly proposed AGC is more efficient than others in terms of computation amount and throughput. The designed digital circuit was implemented by using Verilog HDL, and tested using a Xilinx Kintex 7 device. As a result, the proposed repeater can simultaneously handle 40 FM channels and 6 DMB channels in parallel. Output power level is also always maintained by the AGC.

Impact of Soil Texture on Path Loss Modelling of an FM Signal Using Diffraction Technique

A novel solution to predict path loss of an FM signal using diffraction technique is proposed. Diffraction technique and soil texture impact are used to improve the Friis free-space model to predict the received signal strength and propagation path loss of an FM signal between a transmitter site and receiver site, while studying the impact of soil texture to the FM signal in the case of surface wave propagation. Measurement of signal strengths with an interval of 5KM along two different routes (1 and 2) were taken with a Digital Field Strength Meter (DW-400), in some selected open/rural environments of Kogi State. A solid-state transmitter (BE 20S), with broadcast frequency of 101.5MHz at antenna height of 120m was considered as the transmitting point source. Bluetooth signal strength meter software was used to visualize this impact of soil texture, where different types of soil were considered within the coverage area of the FM radio station, with the application of a Wireless Personal Area Network (WPAN) technology. Measurements taken along the two different routes were compared against predictions made by the modified model of Friis Free Space. The model showed quite large mean path loss prediction errors, and places with poor signal strength for Prime FM Radio Nigeria were revealed. The result shows that an FM signal induces current in the ground over which it passes and it is attenuated as a result of absorption of energy by the soil, depending on the soil type.

The Impact of Soil Texture on Path Loss Modelling of an FM Signal Using Diffraction Technique

A novel solution to predict path loss of an FM signal using diffraction technique is proposed. Diffraction technique and soil texture impact are used to improve the Friis free-space model to predict the received signal strength and propagation path loss of an FM signal between a transmitter site and receiver site, while studying the impact of soil texture to the FM signal in the case of surface wave propagation. Measurement of signal strengths with an interval of 5KM along two different routes (1 and 2) were taken with a Digital Field Strength Meter (DW-400), in some selected open/rural environments of Kogi State. A solid-state transmitter (BE 20S), with broadcast frequency of 101.5MHz at antenna height of 120m was considered as the transmitting point source. Bluetooth signal strength meter software was used to visualize this impact of soil texture, where different types of soil were considered within the coverage area of the FM radio station, with the application of a Wireless Personal Area Network (WPAN) technology. Measurements taken along the two different routes were compared against predictions made by the modified model of Friis Free Space. The model showed quite large mean path loss prediction errors, and places with poor signal strength for Prime FM Radio Nigeria were revealed. The result shows that an FM signal induces current in the ground over which it passes and it is attenuated as a result of absorption of energy by the soil, depending on the soil type.

An Enhanced Phase locked loop with demodulation of FM signals

An Enhanced Phase locked loop with demodulation of FM signals

Intelligent Bearing Fault Diagnosis Based on Tacholess Order Tracking for a Variable-Speed AC Electric Machine

Bearing fault diagnosis in an alternating-current (AC) electric machine (EM) under variable-speed conditions without a tachometer is a challenge. This issue is addressed through an intelligent method based on synchrosqueezing wavelet transform (SWT) and tacholess order tracking (TOT) techniques, which are used to analyze the synchronously sampled current and vibration signals, respectively. The current signal is typically an amplitude- and frequency-modulated (AM–FM) signal. SWT can not only extract the instantaneous frequencies of the AM–FM signal but also reconstruct the harmonic components accurately. Initially, the IF curve with the highest energy is extracted adaptively to reconstruct the rotation component. Subsequently, the mechanical rotation angle is calculated from the rotation component for TOT. The effectiveness of the proposed method is evaluated on a brushless direct-current motor and a permanent magnet synchronous generator with different fault bearings. The method’s superiority is verified through a comparative study. Given that the proposed method is intelligent and efficient, it can be used in the industry and extended to the fault diagnosis of other AC EMs.

Оброблення результатів вимірювання фази періодичних сигналів автогенераторних перетворювачів фізичних величин

The problem of phase measuring is a promising scientific and technical direction, but the general tendency of its solution is the inextricable development of the methodology of information processing and software and hardware part of the control and measuring equipment used in such fields as radiophysics, radio navigation, precision measurement of roughness, size and defects, surfaces and crystals, detecting, including noisy FM signals. At present, the following methods for measuring the phase difference of signals, such as phase compensation, phase difference transformation in time intervals, correlation methods, Fourier series transformation method with subsequent phase separation, as well as digital methods, the most common of which is the time gate method and method of a discrete number of pulses of a measuring signal. Most of the described methods are designed to measure the phase of harmonic and quasi-harmonic signals. However, in real-world measurement, the measuring channel is a source of noise; the output measurement signal is distorted and requires filtration, which requires the use of complex filter systems, or application software that implements a signal filtering algorithm. This problem can also occur due to the relaxation mode of the measuring self-generator and violation of the power supply. In order to simplify the hardware and reduce the number of mathematical operations that increase the measurement time and reduce the sensitivity of the measurement, a numerical method for calculating the phase of the measurement signal of self-generator converters of physical quantities in the background of the action of the additive noise of the signal propagation channel, including parasitic amplitude modulation, is demonstrated. , thus eliminating the need to consider the spectral composition of the signal and the cumbersome calculations of the Fourier transform.

Цифровая обработка сигналов с применением RTL-SDR-приемника н а примере ЧМ-сигн ала

Цифровая обработка сигналов с применением RTL-SDR-приемника н а примере ЧМ-сигн ала

Four-PAM Modulation of Ambient FM Backscattering for Spectrally Efficient Low-Power Applications

Ambient backscatter uses radio frequency signals available in the environment (e.g., radio broadcasting, television, or mobile telephony) to transmit data effectively leading to significant energy and cost efficiency increase. This paper presents a novel wireless tag, which for the first time utilizes 4-pulse amplitude modulation technique to modulate the ambient backscattered FM signals in order to send data to a nearby low-cost software defined radio reader. The tag is based on an RF front-end that uses a single transistor controlled by an ultralow-power microcontroller. The microcontroller includes an analog-to-digital converter for sensing and a digital-to-analog converter for RF front-end control. A proof-of-concept prototype is demonstrated in an indoor environment with the low bit rate of 345 b/s and power consumption $27~\mu \text{W}$ . It operated using a real FM station at 34.5 km away and the tag-to-reader distance was tested at 1 m. The value of energy spent in this modulator was 78.2 nJ/bit at 345 b/s and 27.7 nJ/bit at 10.2 kb/s.

USRP 2901 Based FM Transceiver with Large File Capabilities in Virtual and Remote Laboratory

The radio signal processing capability can be provided by Universal software radio peripheral (USRP) hardware. The received signal frequency can be controlled and transmitting the signal through wireless is possible by installing NI USRP utility configuration. The programmable USRP was running VI snippet program in block diagram panel with radio companion integrated through USB cable on windows 7 64 bit OS. With the parameters such as IQ rate, transmitter gain, carrier frequency along with device name which is given as ni2901_1 the students can able to tune the radio signal. In addition to this the students can able to record the FM signal and extract the IQ data and plot the spectrum of signal and analyze it using graph palette. The standard FM equation contains the modulation index, carrier frequency, message signal amplitude, frequency deviation and frequency sensitivity can also analyzed using LabVIEW. By using Carson’s rule the bandwidth of wideband FM signal can be calculated. In this project RF0 module is used USRP device is connected with dual band vertical antenna with 2.4 and 5GHz frequency as Tx1 and the receiver is connected to Tri band vertical antenna with 144, 400 and 1200 MHz. while transmitting red color will blink in the device for transmitting and green color indicates the received signal. The purpose of doing this experiment was to gain experience in signal processing and receive hands on experience with the USRP. This VI snippet program will support all file formats. Up sample we used in front panel should be -1 always and if large size files is transmitted the value should be increased. The iPhone received the signal with high quality using ear pods the students can able to listen all the information which is transmitted through USRP. Here the transmitted frequency we used in the front panel is 94.7 MHz. The transmitted signal through USRP is successfully tested in the campus of Institute of Aeronautical Engineering, Hyderabad, India.

Theoretical investigation of the capture effect in IMDD-based microwave photonic mixers

We study the large-signal behavior of microwave photonic (MWP) mixers to investigate the small-signal suppression phenomenon commonly referred to as the capture effect. We introduce and theoretically study the capture effect in the context of MWP mixers. Theoretical expressions are derived for calculating the capture effect in three basic MWP mixer types based on intensity-modulation direct-detection (IMDD). We show that the capture effect not only is a function of the power ratio between the input radio-frequency (RF) signals to the MWP mixers, but also depends on the absolute value of their powers. In addition, it is shown that the capture effect of an IMDD-based MWP mixer depends on the fiber dispersion and chirping of the optical modulator, but does not depend on the noise of its components and bias drift of the optical modulator. We extend the study to different unequal-power frequency components of a signal, and as a practical example, we investigate the capture effect when a narrowband FM signal is applied to the RF input of an IMDD-based MWP mixer, theoretically demonstrating considerations and limitations in using MWP mixers.

Superior Execution Time Design of a Space/Spatial-Frequency Optimal Filter for Highly Nonstationary 2D FM Signal Estimation

Multiple-clock-cycle, signal adaptive, and fully pipelined hardware design of the optimal (Wiener) space/spatial-frequency (S/SF) filter is developed in this paper. All implementation and verification details, as well as the extensive comparative analysis, are provided. The developed solution optimizes critical design performances related to the hardware complexity, in line with multiple-clock-cycle nature. Variable (signal adaptive) number of clock cycles, taken within the execution in different S/SF points, provides this solution to retain the optimized time requirements, as well as high resolution, selectivity, and estimation quality of the corresponding recently proposed signal adaptive filtering solution. However, as the major contribution, the fully pipelined implementation enables the developed design to additionally improve the time required for execution. The achieved improvement corresponds to a clock cycle per each S/SF point performed within the estimation that results in the significant comparative improvement in execution time of up to 50% in terms of S/SF points lying outside the local frequency of the estimated 2D frequency-modulated signal. The implementation is tested on a highly nonstationary multicomponent signal and is verified by a field programmable gate array circuit design.

A Frequency Demodulator Based on Adaptive Sampling Frequency Phase-Locking Scheme for Large Deviation FM Signals

A frequency demodulation scheme based on adaptive sampling frequency phase-locking loop (PLL) is proposed for extracting large deviation message signal from sinusoidal frequency-modulated signals. The proposed scheme has been designed to track the frequency-modulated input signal using a look-up-table and adaptively changing the sampling period. While tracking the carrier signal, the numerically controlled oscillator involved in the PLL structure produces the sampling frequency according to the variation of input frequency. In the PLL, the message signal has been extracted at the output of proportional integral controller. Simulation results prove that the PLL exhibits quick acquisition behavior, wide operating range, negligible steady-state error. Experimental investigation validates the efficacy of the proposed PLL performance in message signal extraction.

A novel phase parameter estimation method of quadratic FM signal based on Sigmoid fractional ambiguity function in impulsive noise environment

To overcome the limitations that the second-order statistics based methods rely heavily on gaussianity assumption and the fractional lower-order statistics based methods depend on the priori knowledge of non-Gaussian noise, two novel concepts, the Sigmoid transform based instantaneous correlation function and Sigmoid transform based fractional ambiguity function, are defined firstly. Based on these definitions, a novel phase parameters estimation method of the quadratic FM signal is proposed in impulsive noise environment. Furthermore, the property of the Sigmoid transform is presented and proved. Simulations have verified its superior performances over existing methods based on fractional ambiguity function or fractional ambiguity function based on fractional lower order statistic, especially under impulsive noise. Meanwhile, it does not depend on the priori knowledge of noise.

Investigation into the structure of spectra of signals with linear frequency modulatio

Analytical expressions for the spectrum and the uncertainty function for composite non-uniform signals with FM pulse width (SNLFM-FM signals) are obtained. The technique and results of studies of the SNLFM - FM signals spectral, correlation and structural properties are presented in the manipulation of the phase by various classes of binary discrete sequences.

Synchronous radio-frequency FM signal generator using direct digital synthesizers.

A novel Radio-Frequency Frequency-Modulated (RF-FM) signal generation method is introduced and a prototype circuit developed to evaluate its functionality and performance. The RF-FM signal generator uses a modulated, voltage-controlled time delay to correspondingly modulate the phase of a 10 MHz sinusoidal reference signal. This modulated reference signal is, in turn, used to clock a Direct Digital Synthesizer (DDS) circuit resulting in an FM signal at its output. The modulating signal that is input to the voltage-controlled time delay circuit is generated by another DDS that is synchronously clocked by the same 10 MHz sine wave signal before modulation. As a consequence, all of the digital components are timed from a single sine wave oscillator that forms the basis of all timing. The resultant output signal comprises a center, or carrier, frequency plus a series of phase-synchronized sidebands having exact integer harmonic frequency separation. In this study, carrier frequencies ranging from 10 MHz to 70 MHz are generated with modulation frequencies ranging from 10 kHz to 300 kHz. The captured spectra show that the FM signal characteristics, amplitude and phase, of the sidebands and the modulation depth are consistent with the Jacobi-Anger expansion for modulated harmonic signals.

Parameter estimation of CFM signals based on MICPF‐HAF

A novel algorithm for parameter estimation of cubic frequency modulated (CFM) signals, known as a modified integrated cubic phase function high-order ambiguity function (MICPF-HAF), is introduced. The MICPF-HAF demodulates CFM signals to quadratic FM (QFM) signals via phase differentiation, and then the MICPF is applied to realise the parameter estimation of QFM signals. The analyses and simulations show that the proposed MICPF-HAF achieves a great improvement in anti-noise performance in comparison with the HAF and the CPF-HAF-based methods.

Teager–Kaiser energy methods for signal and image analysis: A review

This paper provides a review of the Teager–Kaiser (TK) energy operator and its extensions for signals and images processing. This class of operators possesses simplicity and good time-resolution and is very efficient in instantaneously estimating AM–FM signals and images. We point out the importance of the concept of energy from the point of view of the generation of the signal. More precisely, we emphasize the importance of analyzing signals from the point of view of the energy of the system needed to produce them. We show how this class of TK energy operators can be used to estimate useful features for signals and images analysis in time, space and frequency domains such as instantaneous frequency, second-order moment frequency, coherence function or spatial envelope and phase. We also show the importance of the higher derivative order of TK energy operator in terms of demodulation for both mono and multi-dimensional signals. Most of the developed tools around TK energy operators deal with real and complex-valued signals and some of them extended to multi-dimensional case. Due to their low complexity and their instantaneous-adapting nature, the class of TK energy operators offers valuable processing tools for time (space), frequency and time–frequency analysis.

A Novel Parameter Estimation Method of the Quadratic FM Signal in Alpha-stable Distribution Environment

This paper takes the Alpha-stable distribution as the noise model and studies the parameter estimation problem of quadratic FM signal in the impulsive noise environment. Since the conventional algorithms degenerate severely in the impulsive noise environment, this paper proposes a novel method of fractional ambiguity function basing on the fractional lower-order statistics (FLOS-FAF). Firstly, the fractional lower order Instantaneous correlation function is proposed and is performed by the fractional Fourier transform (FRFT). Secondly, parameters of quadratic FM signal are jointly estimated by peak searching the FLOS-FAF and dechirping method. Simulation experiments verify that the proposed algorithm can suppress the impulse noise and has good performance when poor SNR condition exists.

A 5-mW 750-kb/s Noninvasive Transceiver for Around-the-Head Audio Applications

This brief presents a noninvasive energy-efficient frequency-modulated ultra-wideband (FM-UWB) transceiver. 8-frequency-shift-keying (FSK) subcarrier modulation is utilized to enhance the data rate with a slight increment of hardware complexity compared to the conventional 2-FSK FM-UWB system. The transmitter employs a fast settling PLL with a pretuned relaxation VCO for 8-FSK subcarrier modulation. The transmitted signal by an FLL-assisted ring VCO followed by a single-stage class AB power amplifier meets the FCC spectrum mask. The regenerative receiver employs a wideband LNA with a stacked structure to save power. Two 4th-order Butterworth bandpass filters and envelope detectors convert the FM signal to an AM signal with good linearity. The 3.5-4 GHz 750-kb/s transceiver implemented in 65-nm CMOS consumes 5 mW from a 1-V supply, achieving an energy efficiency of 6.7 nJ/bit.