FM Carriers Research Articles

A pedigree-based prediction model identifies carriers of deleterious de novo mutations in families with Li-Fraumeni syndrome.

De novo mutations (DNMs) are increasingly recognized as rare disease causal factors. Identifying DNM carriers will allow researchers to study the likely distinct molecular mechanisms of DNMs. We developed Famdenovo to predict DNM status (DNM or familial mutation [FM]) of deleterious autosomal dominant germline mutations for any syndrome. We introduce Famdenovo.TP53 for Li-Fraumeni syndrome (LFS) and analyze 324 LFS family pedigrees from four US cohorts: a validation set of 186 pedigrees and a discovery set of 138 pedigrees. The concordance index for Famdenovo.TP53 prediction was 0.95 (95% CI: [0.92, 0.98]). Forty individuals (95% CI: [30, 50]) were predicted as DNM carriers, increasing the total number from 42 to 82. We compared clinical and biological features of FM versus DNM carriers: (1) cancer and mutation spectra along with parental ages were similarly distributed; (2) ascertainment criteria like early-onset breast cancer (age 20–35 yr) provides a condition for an unbiased estimate of the DNM rate: 48% (23 DNMs vs. 25 FMs); and (3) hotspot mutation R248W was not observed in DNMs, although it was as prevalent as hotspot mutation R248Q in FMs. Furthermore, we introduce Famdenovo.BRCA for hereditary breast and ovarian cancer syndrome and apply it to a small set of family data from the Cancer Genetics Network. In summary, we introduce a novel statistical approach to systematically evaluate deleterious DNMs in inherited cancer syndromes. Our approach may serve as a foundation for future studies evaluating how new deleterious mutations can be established in the germline, such as those in TP53.

Time-multiplexed video transmission system: a bandwidth efficient technique for high-quality television transmission via satellite

A bandwidth-efficient television transmission technique called time-multiplexed video transmission (TMVT) is described. The TMVT system uses a two-dimensional filtering and interpolation technique to reduce the transmission bandwidth of TV signals, thereby increasing the utilization efficiency of a satellite transponder by approximately 50%. The system adopts the time-multiplexed component transmission scheme with a single carrier to eliminate interference between different TV signals transmitted through the same satellite transponder, and to avoid the intermodulation between the multiple FM carriers, as in the conventional frequency division multiplexing (FDM) approach. A prototype hardware system has been built and tested, with results closely matching the theoretical analysis. >

Cross-spectral envelope phase discrimination for FM signals

Previous measures of cross-spectral envelope phase sensitivity have used amplitude-modulated sinusoidal carriers. To the extent that these measures reflect the fidelity of the auditory signal representation of complex signals, it should be possible to predict phase disparity thresholds for arbitrary classes of signals. Modulation phase discrimination functions were obtained for sinusoidal FM carriers at 500 and 2000 Hz. For a 0-deg phase disparity between the modulators of the standard, sensitivity to a disparity in the phase of FM modulation is monotonically related to the product of modulation frequency and modulation index over the range of modulation frequencies studied (8–64 Hz). A simple model of this discrimination task assumes that FM signals are converted into AM signals through bandpass filtering at the auditory periphery. This model was tested by demodulating the FM signals through auditory filters tuned to 500 and 2000 Hz. Thresholds obtained for these “FM-equivalent” AM signals were nearly an order of magnitude smaller than the original thresholds and it was necessary to “de-tune” the auditory filters (5- to 10-dB slopes) to fit the FM data. [This research was supported by a grant from the AFOSR.]

Optimization of frequency assignment for reduction of cochannel interference

AbstractThis paper describes the method of optimization of frequency assignment in satellite communication, aiming at reducing cochannel interference. The method is based on the formulation of the assignment problem, so‐called mathematical programming, and is widely applicable. The basic model is defined, and is composed of a pair of systems sharing the same frequency band. A discrete frequency assignment is made with the small segment as the unit, which is obtained by equi‐partitioning the common channel, and the model is formulated as an assignment problem. The lexicographical minimization is employed as the criterion of optimization, by which the interference is reduced for all carriers. A method is presented in which the optimum solution is obtained by the numerical conversion of the cost matrix and the Hungarian method for the assignment problem. To determine efficiently the optimum assignment for carriers with various bandwidths, an algorithm is presented which is based on the branch‐and‐bound method used frequently in the mathematical programming. By this method, the solution can be determined with a small amount of computation for a problem of practical size. Examples are shown which are the assignment of FM carriers by the basic model and the optimum frequency assignment for eight satellites. As a result, it is shown that the frequency assignment can be determined with sufficient accuracy, and the interference is reduced drastically by sufficiently fine segmentation.

A method for estimating the protection ratio in fm television transmission

AbstractA calculation method for estimating the protection ratio in FM‐TV transmission is described. The interference between two FM carriers modulated by the NTSC or TCI color bar signal is analyzed and the baseband interference is expressed in a simple form as beat interference. Applying several weighting functions of the visual system to the beat interference, a subjective interference index which expresses the degree of subjective impairment is defined and then a method for estimating the protection ratio using this index is proposed. The protection ratios calculated by this method for various signaling systems and modulation parameters agree well with the results of subjective assessment tests. The method permits determination of the protection ratio in any FM‐TV system without subjective assessment tests for various parameters. It can be used to estimate the protection ratio in introducing new services to existing satellite broadcasting channels and to develop new channel plans.

Carrier-to-Intermodulation Performance of Multiple FM/FDM Carriers Through a GaA1As Hetrojunction Laser Diode

The simple nonlinear rate equations are used to predict the carrier-to-intermodulation performance of laser diodes excited by an arbitrary number of equal-amplitude, equally spaced FM carriers. The special case of relatively small input carrier amplitudes and slowly varying angle modulations is considered and closed-form approximations are obtained.

A Power Series Expansion Approach to Evaluate Modulation Transfer Noise Effects from Digital Carriers to FDM/FM Carriers in Memoryless Nonlinear Devices

This paper presents a power series expansion approach for evaluating modulation transfer noise effects from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</tex> digital carriers (continuous or bursty) to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</tex> FDM/FM carriers in a common memoryless nonlinear amplifier. The method allows for a complete characterization and assessment of this type of transmission impairment and its effects in satellite communications systems. The baseband modulation transfer noise in the FM carriers caused by the random envelope fluctuations due to filtering of PSK pulses and/or by the on-off bursting of the digital carriers can be calculated. Illustrative numerical results indicate that the mixed PSK-FM mode of operation in satellite transponders should be employed with great care since a number of 4 kHz channels in the basebands of the FM carriers may receive prohibitive interference.

Fiber Optic Intermodulation Distortion

In analog frequency-division multiplexed fiber optic systems, laser nonlinearities transfer energy between the different carriers, resulting in intermodulation distortion and interference. A third-order polynomial without memory is used to model the nonlinearity. The FM frequency-division multiplexed (FM/FDM) signal consists of a set of FM carriers at frequencies. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N_{\omega 0}</tex> , where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N = L, L + 1, L +2, ... , M</tex> . The video distortion introduced by the nonlinearity is determined for various types of second- and third-order intermodulation terms. The intermodulation distortion frequency spectrum is determined for FM signals with assumed Gaussian spectra.

Modulation Transfer from TDMA On-Off Bursting to FM Carriers in Memoryless Nonlinear Devices: Part I--Power Spectra

The modulation transfer noise caused by the bursts of TDMA signals is modeled and analyzed in detail. Expressions of the power spectra of the RF and the baseband modulation transfer noise have been obtained for the most general case of L TDMA and N FM carriers in a zero-memory nonlinear amplifier such as a helix-type TWTA. From these general expressions, the RF power spectrum and the baseband modulation transfer noise onto the FM carriers can be readily computed. It is shown that there are only line spectra and no continuous spectrum in the modulation transfer noise caused by the TDMA on-off bursting. The separation of the spectral lines is equal to the TDMA frame rate. The maximum of the power spectrum of the modulation transfer noise is inversely proportional to the square of the TDMA frame duration and is independent of the separation between TDMA and FM carriers. The modulation transfer noise is in general a complicated function of TDMA burst levels, burst patterns, burst lengths, FM carrier levels, carrier sizes, device nonlinearities, and operating points.

Modulation Transfer from TDMA On-Off Bursting to FM Carriers in Memoryless Nonlinear Devices, Part II-Baseband Performance

When TDMA and FM carriers are commonly amplified by a memoryless device with nonlinear amplitude and phase characteristics, modulation transfer noise induced by the on-off bursting of the TDMA signals will be present at the FM carriers. In Part II of this paper, closed form expressions of the power spectra of the modulation transfer noise are derived for many special carrier configurations of interest. Numerical examples are also provided in terms of the signal-to-modulation transfer noise ratio, SNR, in the baseband of the FM carriers. It is shown how SNR varies as a function of TDMA burst levels, burst patterns, burst lengths, FM carrier levels, carrier sizes, and device nonlinearities and operating points. With these detailed analyses and numerical examples, insight can be gained into the mechanism of modulation transfer from TDMA on-off bursting to the FM signals. Results presented in this part of the paper should be useful for transmission systems planning and evaluation, and for TDMA burst scheduling.

Interference between FM Carriers and a Digitally Modulated SCPC Circuit

The interference from the digital single channel per carrier (SCPC) circuits into frequency-modulated carrier systems has been calculated by convolving the desired and the interfering spectra extending the previously published works. Resulting interference noise power in FDM/FM systems covering a wide range of modulation indices and basebands has been presnted. Also plots of interference noise power as a function of the number of SCPC circuits have been presented for various values of carrier power to interference power ratios.

Nonlinear Spectrum-Spreading Interference Effects Between Adjacent Satellite Transponders

For communications satellites carrying a phase-shift keying (PSK) modulated carrier in one transponder and FM carriers in neighboring transponders, there is a potential adjacent interference effect from the PSK carrier into the FM carriers. In this correspondence the noise-power ratio (NPR) degradation is calculated for the top voice channels of the FM carriers as a function of the time-division multiple-access (TDMA) transponder single-carrier saturated equivalent isotropic radiated power (eirp), the TDMA transponder output filter selectivity, and the FM carrier sizes, Calculations are performed for the specific parameters of the INTELSAT IV system and compared with laboratory measurements. However the results are easily extendable to other communications satellite systems.

Some effects of delay and modulation-index mismatch on cochannel FM interference

The baseband distortion resulting from the cochannel interference of two FM carriers nominally carrying the same modulation is considered. Such distortion was observed to plague VHF mobile telephone service in Phoenix, Ariz. This distortion arises when the landline audio delay and modulation indices of the two transmitters are not closely equalized. Both sinusoidal and Gaussian modulation age analyzed. Curves presented indicate that baseband distortion power as large as 20 percent of baseband signal power may occur for an RF carrier amplitude ratio of 0.7 and an unequalized delay of the order of 200 µs when the minimum rms transmitter phase deviation is 2 rad. Increasing the deviation to 4 rad reduces the distortion to the 5-percent range. The desirability of large index modulation in this context is thus apparent.

Measurements of AM-PM conversion in low-noise TWT's, TDA's, and parametric amplifiers

Experiments have been carried out to determine the AM-PM conversion coefficients of traveling-wave tubes, tunnel diode amplifiers, and parametric amplifiers. Phase-input power characteristics have been measured by a precision phase bridge, and formulas are quoted for the calculation of both intelligible and unintelligible cross-talk coupling when the device handles multiple FM carriers.

Spurious Sidebands of a Linear Signal

For interference evaluation studies, the voltage or power spectrum of transmitting systems must be known. This paper evaluates the magnitude of the sideband power levels for linear FM carriers. Carriers of this type are encountered in FM-CW and FM pulsed radars. Analytical expressions are derived and spectral amplitudes are plotted which permit rapid evaluation of spurious sideband powers as a function of a normalized frequency deviation about the carrier.

Multiple-Carrier Behavior of a Frequency-Selective Ferrite Limiter

The ferrite limiter is a device which has the property of independently limiting two or more RF carriers if they are spaced by several megacycles from each other. This property may have utility in communication satellites as a multiple access tool or for minimizing the effects of jamming signals. The introductory section describes the device, its limiting action, and mode of operation in a commercial or military communications satellite. The body of the paper summarizes the measurements taken to determine the communications performance of the device. Specifically, measurements covering the steady state and dynamic bandwidth, the limiting action for one and two FM carriers, the phase linearity, and the crosstalk between two FM carriers are presented. The measured performance of the device was in reasonable agreement with performance predicted from a simplified analytic model. Measurements found the device to be essentially distortionless for a single wideband FM signal. With two carriers present, the limiting factor of performance was found to be coherent crosstalk.