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41 
Computer Simulation of Cross Correlators for Correlated InputsCoulter, Linda J. 01 January 1984 (has links) (PDF)
Cross correlator systems, analog and clipped input channels, with correlated random narrow band Gaussian noise as inputs are computer simulated. The performance of each system is evaluated on the basis of the output signaltonoise ratio. The output SNR of each system is compared with theoretical asymptotic approximations computed as a function of the SNR of the input channels. The output of the simulation compares within 3 dB of the asymptotic approximations for the analog correlator for all values of the correlation coefficient tested and for the systems with clipped input channels with uncorrelated inputs. For the systems with clipped input channels, certain combinations of the input SNR with nonzero correlation cause the output SNR to be zero. This causes discontinuities in the dB plot. For the systems with clippers and nonzero correlation of the input channels, the output of the simulation compares within 3 dB of the results of the asymptotic approximations when no discontinuities occur in the output plot.

42 
A study of the effects of linear networks on FM wavesJohnson, Preston Benton 12 January 2010 (has links)
The analysis of the distortion which results when frequencymodulated waves are passed through linear networks is investigated by the Fourier method and the Quasisteadystate method. The major enphasis is placed on the Fourier method, and extensive digital computer programs are developed to allow this method to be implemented on the modern, highspeed digital computer. In the Fourier method, the frequencymodulated wave which is applied to the input of a linear network is broken up into its Fourier spectrum. Each of the resulting ‘'sideband'' frequencies is then passed through the network and is subjected to alterations in amplitude and phase. The output wave is then synthesized by taking the vector sum of the "weighted" sideband components. In contrast to the single pair of sideband frequencies generated by amplitude modulation, the spectrum of a frequencymodulated wave contains an infinite number of sideband components. Fortunately, only a relatively small number of these sidebands have significant influence on the total makeup of the waveform. The number of significant sidebands is proportional to the value of modulation index. When the modulation index is high, the number of significant sidebands is very large and the number of computations required by the Fourier method becomes enormous. Previously considered to be completely impractical, the Fourier method was usually abandoned in favor of the Quasisteadystate approach. However, the digital computer techniques developed in the course of this investigation allow for a fast, economical, and convenient analysis based on the Fourier method even when the modulation index is relatively high. Analyses were performed for values of modulation index up to 45 and techniques are discussed for increasing this range.
The Quasisteadystate method is based on the assumption that the frequency of the input wave is changing slowly enough that the frequency of the output wave at any instant is equal to the "instantaneous fregquency' of the input wave. This method is inherently in error since it neglects the transient terms generated by the changing frequency. To compensate for this error, it is the general practice to incorporate correction terms, usually in the form of an infinite series. The Quasisteadystate method is more effective at low modulating frequencies (high modulation index). While the analysis contained in this paper considers in detail only a firstorder correction, the application of higherorder correction terms is discussed. The results obtained from applying both analyses to a complex, multisection filter indicate that the computer solution of the Fourier method is preferable for intermediate values of modulation index.
Experimental verification of the Fourier method is obtained by simulating the system on an analog computer. The advantages of this rather novel approach are discussed in some detail. The agreement between the results predicted by the digital computer and those obtained experimentally leaves no doubt to the validity and accuracy of the analysis.
Digital computer programs for analyzing the distortion using each of the above methods are given. Subprograms are also included, some of which can be used independently. Among these are a program that computes Bessel functions of the first kind for positive and negative orders and a program that computes the minimum phase shift of a network from its atténuation. All programs are written in the FORTRAN IV computer language and were executed on the IBM 7040/1401 system. / Ph. D.

43 
Measurements and models of radio frequency impulsive noise inside buildingsBlackard, Kenneth Lee 18 August 2009 (has links)
This thesis presents results of average and impulsive noise measurements inside five office buildings and retail stores. Measurements were made at 918 MHz, 2.44 GHz, and 4.0 GHz using a superheterodyne receiver with 70 dB dynamic range and a 3dB RF bandwidth of 40 MHz. Omnidirectional and directional antennas were used to investigate the characteristics and sources of radio frequency noise in indoor channels. Statistical analyses of the measured data are presented in the form of amplitude probability distributions, pulse duration distributions, pulse spacing distributions, and noise factor distributions. Simple mathematical models of these statistical characterizations are also presented.
The measurements and analyses indicate devices with electromechanical switches (copy machines, microwave ovens, printers, and electric motors) are principal sources of impulsive noise in retail and office environments. The 918 MHz band was consistently the worst band throughout the measurement campaign. This is attributed to higher path losses at 2.44 GHz and 4.0 GHz, and to adjacent and cochannel interference from users near the 902928 ISM band. Pulse duration statistics indicate that no significant differences exist between impulse durations in the measured bands. This suggests that impulsive noise inside buildings is very wideband, and that pulse durations are directly a function of the receIver bandwidth. Pulse spacing statistics also indicate that intervals between consecutive impulses are similar in each frequency band.
This thesis developed a computer simulation algorithm to create sequences of impulsive noise events which have statistical distributions similar to measured data. The statistical results for simulated impulsive noise are compared to measured distributions to illustrate the accuracy of the simulation algorithm. / Master of Science

44 
Weak narrowband signal detection in multivariate nongaussian clutterSistanizadeh, Mohammad K. January 1986 (has links)
This dissertation is concerned with the development and performance analysis of nonlinear receivers for detection of weak narrowband signals in multivariate nonGaussian clutter. The novelty of the detection scheme lies in the utilization of both the complex measurement and the multivariate nonGaussian character of the clutter. Two clutter models are developed based on the available partial information. Model (I) is based on the a priori knowledge of the firstorder density, correlation structure of the amplitude, and the circular symmetric assumption of the inphase and quadrature phase components. Model (II) is based on the firstorder inphase and quadrature phase densities and the complex correlation structure. These models completely specify a multivariate complex nonGaussian density and can be used for clutter generation.
A class of optimum nonlinear receiver structures based on weak signal level, canonically known as Locally Optimum Detectors (LOD) are derived under clutter Model (I). This can be considered to be a generalization of the LOD for the independent and identically distributed (i.i.d) clutter. The detectors utilize complex measurements and their structures depend on whether the underlying hypothesis testing model is real or complex.
The performance of each of the proposed detector structures, based on the concept of Efficacy, is formulated. Then, the performance of the detectors are evaluated with respect to a reference detector using Asymptotic Relative Efficiency (ARE) criterion. Numerical evaluation of the performance expression is carried out for constant signal in Weibull distribution for various density parameters. Simulation results indicate that the performance of the developed detectors, based on ARE, is superior to (i.i.d) LOD detector and matched filter.
Finally, the sensitivity of the detector performance to parameter variation of the structural nonlinearities is investigated. / Ph. D.

45 
A comparison of digital beacon receiver frequency estimatorsGendron, Paul John 29 September 2009 (has links)
Two algorithms for estimating the frequency and power of the carriers of 20 GHz and 30 GHz satellite signals are compared. Both algorithms operate on a prefiltered sequence generated by lowpass filtering followed by signal decimation for the purpose of sampling rate reduction. The lowpass filtering is accomplished via the overlapadd method of FIR filtering using the FFT. Carrier frequency prediction and tracking is accomplished with a Kalman predictor, for which the frequency drift process is modeled via polynomial extrapolation. The Kalman predictor operates on frequency measurements provided by one of two frequency estimators.
One of the frequency estimation algorithms, a refinement of the DFTautomatic frequency control technique, uses the ChirpTransform algorithm in its aim for the maximum likelihood estimate of frequency and power. The averaged periodogram is computed from the prefiltered sequence and is used to measure the frequency of the drifting frequency signal as well as its power. One of the disadvantages of this algorithm is the bias present in the estimation of power. The bias can be removed only with knowledge of the noise power. The algorithm has the advantage of being almost exclusively a convolution and therefore is accomplished with minimal computation via the FFT.
An alternative parametric approach to frequency estimation is also investigated. In this approach the weighted leastsquares modified YuleWalker method of autoregressive model estimation is used on the prefiltered sequence to yield frequency estimates. Power estimation is accomplished next via modal decomposition of the estimated correlation sequence. The advantage of this approach is that for slowly varying frequency drift paths (24 hour cycle) the frequency estimates exhibit MSE approximately 3 dB less than the ChirpTransform algorithm over a wide range of SNR. There are two disadvantages to the parametric algorithm. First the parametric algorithm estimates power with MSE approximately 2 dB greater than the nonparametric algorithm. Secondly the algorithm is more complicated than the nonparametric ChirpTransform algorithm because it requires matrix inversions and the determination of the roots of a polynomial.
For the digital beacon receiver problem investigated here both algorithms perform similarly in two important respects. First both algorithms can lock onto a carrier signal whose frequency is drifting at the rate of 5 Hertz per second in a noise environment corresponding to a 15 dB/Hz SNR. Secondly both algorithms can make unbiased frequency estimates of the carrier signal allowing the receiver to track the carrier at 7 dB/Hz SNR. Both algorithms attain the CramerRao bound for estimation of constant frequency sinusoids. For a simulated satellite signal with maximum frequency drift of 5 Hertz per second the Kalman frequency predictor is able to reduce the problem to nearly that of the constant frequency case so that the resulting performance corresponds to the CramerRao bound for estimation of constant frequency sinusoids.
Where computational considerations are critical the nonparametric algorithm is preferred. In fact, unless the superior accuracy of the frequency prediction afforded by the parametric algorithm is paramount, the nonparametric algorithm is to be chosen. / Master of Science

46 
Modular approach to the development of a twoway radio receiver systemKellerman, Valpre Cecilia 12 1900 (has links)
Thesis (MScIng)University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The preliminary development of a FM radio receiver module is discussed. An existing narrowband
system operating between 48MHz and 50MHz will be replaced. Digital components were
investigated, compared and used with analogue techniques to build a more flexible twoway radio
receiver system. A direct digital synthesizer was considered as a replacement for the current
synthesized phased lock loop local oscillator and much attention was given to the local oscillator
and mixer design, characteristics and measurement procedures.
A detailed study of receiver systems was undertaken to determine the specifications needed for
every receiver component to achieve satisfactory receiver performance in the end. Receiver
characteristics as well as receiver measurement procedures are defined. A software tool was
developed to aid the design process, establishing computationally whether the receiver
specifications are met prior to the final design.
The complete design process, from fundamental specifications through to the developed final
receiver module is discussed. A modular design approach was used to guarantee easy
manufacturing, substitution and testing. This approach comprises the breakdown of the receiver
into well defined components that are each matched to 50O. The separate components of the
system were designed, measured and characterized to make it possible to replace only a single
component instead of the entire system when a part becomes redundant. / AFRIKAANSE OPSOMMING: Die grondslag vir die ontwikkeling van ‘n FM radio ontvanger module word in hierdie dokument
gelê. ‘n Bestaande noubandstelsel wat tussen 48MHz and 50MHz ontvang word vervang deur
hierdie nuwe stelsel wat aangewend sal kan word in die bestaande tweerigtingradio se omhulsel.
Digitale komponente is ondersoek, vergelyk en gebruik saam met analoogtegnieke om ‘n meer
buigsame radiostelsel te bewerkstellig. ‘n Direkte digitale sintitiseerder is oorweeg as ‘n
vervanging vir die huidige fasesluitlus ossillator met heelwat klem op die oscillatoren
mengerontwerp, komponent spesifikasies en metingsprosedures.
‘n Diepgaande studie van ontvangerstelsels is gedoen om te bepaal wat die tipiese spesifikasies
vir elke ontvangerstadium is, sodat die finale ontvanger se spesifikasies behaal kan word.
Ontvanger eienskappe en meetprosedures word volledig gedefinieer. ‘n Sagtewareprogram is
ontwikkel om die ontvangerontwerpsproses te vergemaklik deur vooraf te kan vasstel watter
ontvangerspesifikasies bereik sal kan word al dan nie.
Die volledige ontwerpsproses, vanaf fundamentele spesifikasies tot by die finale ontvanger word
omskryf. ‘n Modulereontwerp prosedure is gebruik ter versekering van die maklike vervaardiging,
vervanging en toetsing van elke komponent. Die radio is tydens ontwerp opgebreek in
boublokkies wat elkeen aangepas word na 50O. Elke aparte boublokkie van die ontvangerstelsel
is afsonderlik ontwerp, gemeet en volledig gespesifiseer om dit moontlik te maak om slegs een
komponent te vervang in plaas van die hele stelsel wanneer ‘n enkele komponent nie meer
beskikbaar is nie.

47 
Benefits to processor load for quadrature baseband versus radio frequency demodulation algorithmsNdovi, Lusungu 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))Stellenbosch University, 2008. / The continued advancement and improvement of softwaredefined radio technology has
been a key factor in furthering research into the implementation of most signal
processing algorithms at baseband. Traditionally, these algorithms have been carried
out at RF, but with the coming of SDR, there has been a need to shift the processing
down to baseband frequencies which are more compatible with the fast developing
software radio technology.
The study looks at selected demodulation algorithms and investigates the
possibility and benefits of carrying them out at QBB. The study ventures into the area
of beamforming, multipath compensation, Doppler shift compensation and matched
filter detection. The analysis is carried out using Matlab simulations at RF and QBB.
The results obtained are compared, not only to evaluate the possibility but also the
benefits in terms of the processing load. The results of the study showed that indeed,
carrying out the selected demodulation algorithms at QBB was not only possible, but
also resulted in an improvement in the processing speed brought about by the reduction
in the processing load.

48 
Efficient, High power Precision RF and mmWave Digital Transmitter ArchitecturesBhat, Ritesh Ashok January 2018 (has links)
Digital transmitters offer several advantages over conventional analog transmitters such as reconfigurability, elimination of scalingunfriendly, power hungry and bulky analog blocks and portability across technology. The rapid advancement of technology in CMOS processes also enables integration of complex digital signal processing circuitry on the same die as the digital transmitter to compensate for their nonidealities. The use of this digital assistance can, for instance, enable the use of highly efficient but nonlinear switchingclass power amplifiers by compensating for their severe nonlinearity through digital predistortion. While this shift to digitally intensive transmitter architectures is propelled by the benefits stated above, several pressing challenges arise that vary in their nature depending on the frequency of operation  from RF to mmWave.
Millimeter wave CMOS power amplifiers have traditionally been limited in output power due to the low breakdown voltage of scaled CMOS technologies and poor quality of onchip passives. Moreover, high datarates and efficient spectrum utilization demand highly linear power amplifiers with high efficiency under backoff. However, linearity and high efficiency are traditionally at odds with each other in conventional power amplifier design. In this dissertation, digital assistance is used to relax this tradeoff and enable the use of stateoftheart switching class power amplifiers. A novel digital transmitter architecture which simultaneously employs aggressive devicestacking and largescale power combining for wattclass output power, dynamic load modulation for linearization, and improved efficiency under backoff by supplyswitching and load modulation is presented.
At RF frequencies, while the problem of wattclass power amplification has been long solved, more pressing challenges arise from the crowded spectrum in this regime. A major drawback of digital transmitters is the absence of a reconstruction filter after digitaltoanalog conversion which causes the baseband quantization noise to get upconverted to RF and amplified at the output of the transmitter. In high power transmitters, this upconverted noise can be so strong as to prevent their use in FDD systems due to receiver desensitization or impose stringent coexistence challenges. In this dissertation, new quantization noise suppression techniques are presented which, for the first time, contribute toward making wattclass fullyintegrated digital RF transmitters a viable alternative for FDD and coexistence scenarios. Specifically, the techniques involve embedding a mixeddomain multitap FIR filter within highlyefficient wattclass switching power amplifiers to suppress quantization noise, enhancing the bandwidth of noise suppression, enabling tunable location of suppression and overcoming the limitations of purely digitaldomain filtering techniques for quantization noise.

49 
SwitchedCapacitor RF Receivers for High Interferer ToleranceXu, Yang January 2018 (has links)
The demand for broadband wireless communication is growing rapidly, requiring more spectrum resources. However, spectrum usage is inefficient today because different frequency bands are allocated for different communication standards and most of the bands are not highly occupied.
Cognitive radio systems with dynamic spectrum access improve spectrum efficiency, but they require wideband tunable receiver hardware. In such a system, a preselect filter is required for the RF receiver front end, because an outofband (OB) interferer can block the front end or cause distortion, desensitizing the receiver. In a conventional solution, offchip passive filters, such as surfaceacousticwave (SAW) filters, are used to reject the OB interferer. However, such passive filters are hardly tunable, have large area, and are very expensive. Onchip, highselectivity, linearly tunable RF filters are, therefore, a hot topic in RF frontend research. Switchedcapacitor (SC) RF filters, such as Npath filters, feature good linearity and tunability, making them good candidates for tunable RF filters. However, Npath filters have some drawbacks: notably, a poor harmonic response and limited closeby blocker tolerance.
This thesis presents the design and implementation of several interferertolerant receivers based on SC technology. We present an RF receiver with a harmonicrejecting Npath filter to improve the harmonic response of the Npath bandpass filter. It features tunable narrowband filtering and high attenuation of the third and fifthorder LO harmonics at the LNA output, which improves the blocker tolerance at LO harmonics. The 0.21 GHz RF receiver is implemented in a 65 nm CMOS process. The blocker 1 dB compression point (B1dB) is 2.4 dBm at a 20 MHz offset, and remains high at the third and fifthorder LO harmonics. The LNA’s reverse isolation helps keep the LO emission below 90 dBm. A twostage harmonicrejection approach offers a > 51 dB harmonicrejection ratio at the third and fifthorder LO harmonics without calibration.
To improve tolerance for closeby blockers, we further present an SC RF receiver achieving highorder, tunable, highly linear RF filtering. We implement RF input impedance matching, Npath filtering, highorder discretetime infiniteimpulse response (IIR) filtering and downconversion using only switches and capacitors in a 0.10.7 GHz prototype with tunable center frequency, programmable filter order, and very high tolerance for OB blockers. The 40 nm CMOS receiver consumes 38.576.5mA, achieves 40 dB gain, 24 dBm OB IIP3, 14.7 dBm B1dB for a 30MHz blocker offset, 6.89.7 dB noise figure, and > 66dB calibrated harmonic rejection ratio.
The key drawback of our earlier SC receiver is the relatively high theoretical lower limit of the noise figure. To improve the noise performance, we developed a 0.10.6 GHz chopping SC RF receiver with an integrated blocker detector. We achieve RF impedance matching, highorder OB interferer filtering, and flickernoise chopping with passive SC circuits only. The 3480 mW 65 nm receiver achieves 35 dB gain, 4.69 dB NF, 31 dBm OBIIP3, and 15 dBm B1dB. The 0.2 mW integrated blocker detector detects large OB blockers with only a 1 us response time. The filter order can be adapted to blocker power with the blocker detector.

50 
Bounds and algorithms for carrier frequency and phase estimationRice, Feng January 2002 (has links)
Quadrature amplitude modulation (QAM) is a highly bandwidth efficient transmission technique for digital communications. It makes use of multiple signal phase and amplitude levels to carry multiple bits per symbol. This requires accurate and robust carrier phase and frequency estimation in the receiver. / Thesis (PhDElectronicEngineering)University of South Australia, 2002

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