Showing papers on "Bandwidth (signal processing) published in 1969"
TL;DR: A class of finite-state algorithms which characterize self-similar space-filling curves, which enable one to continuously map a line onto an N -dimensional cube, and find application in compressing the bandwidth of arbitrary waveforms are introduced.
Abstract: This paper introduces a class of finite-state algorithms which characterize self-similar space-filling curves. The curves enable one to continuously map a line onto an N -dimensional cube, and find application in compressing the bandwidth of arbitrary waveforms. The bandwidth compression is effected in return for an increased susceptibility of the signal to perturbations. The algorithms are represented in a diagrammatic form which enables one to convert the N coordinates of a point in a cube into a single number representing the distance along a space-filling curve, or vice-versa, merely by visual inspection. The diagrams are always finite in size and may be constructed by following a rather simple numerical procedure.
182 citations
TL;DR: Although the basic analysis is derived in terms of photon "counts," the necessary system optics equations are introduced to allow for overall optical hardware design, and the primary underlying assumption is that synchronization is maintained at all times between the transmitter and receiver.
Abstract: In recent literature the advantages of an idealized narrow-width pulse-position modulated (PPM) optical communication system, using coherent sources and direct photodetection, have been shown. In this paper the practical design of such an operating PPM link is considered. System performance in terms of error probabilities and information rates is derived in terms of key parameters, such as power levels, number of PPM signals, pulse width, and bandwidths. Both background radiation and receiver thermal noise are included. Design procedures utilizing this data are outlined. Whenever possible, optimal design values and parameter tradeoffs, in terms of maximizing information rate or minimizing transmitter power, are shown. The effect on performance of photomultipliers and their inherent statistics is also presented. Although the basic analysis is derived in terms of photon "counts," the necessary system optics equations are introduced to allow for overall optical hardware design. The primary underlying assumption is that synchronization is maintained at all times between the transmitter and receiver.
54 citations
TL;DR: This paper considers the problem of designing a network to shape an arbitrary input pulse into a band-limited pulse having minimum intersymbol interference, and uses the zeros of the network transfer function to achieve the band-limiting properties.
Abstract: A fundamental problem in the design of data transmission systems is the synthesis of pulse-shaping networks which satisfy specifications in both the time and frequency domains. This paper considers the problem of designing a network to shape an arbitrary input pulse into a band-limited pulse having minimum intersymbol interference. The design procedure uses the zeros of the network transfer function to achieve the band-limiting properties (using a modified Temes and Gyi constraint) while the transfer function poles are optimized with a computer to give the desired time response. By limiting the specifications on the shaped pulse to an absolute minimum, very accurate results are achieved with simple networks. Some sample designs and experimental results are included. For example, an 11th order transfer function is designed to shape rectangular pulses for a synchronous baseband pulse amplitude modulation system. The shaped pulses have a bandwidth 20 percent in excess of the Nyquist bandwidth and a theoretical worst-case distortion of 2.1 percent. An active realization of this transfer function achieved a worst-case distortion of about 2.5 percent.
34 citations
TL;DR: In this paper, a theory of laser mode locking due to saturable absorbers when the dispersive property of the active material is taken into account is developed. And the authors show that, owing to dispersion, the phase φ l of the modes ( l running from -N to +N ) has a term that is proportional to l 2 and a term (smaller than the previous one) that is proportionally to l 4.
Abstract: A theory is developed of laser mode locking due to saturable absorbers when the dispersive property of the active material is taken into account. The electric field within the cavity is expanded in terms of cavity modes, the problem is treated under the rate-equation approximation, and only third-order nonlinear polarization terms of the dye are considered. The field is assumed to be made of 2N + 1 oscillating modes. It is shown that, owing to dispersion, the phase φ l of the modes ( l running from -N to +N ) has a term that is proportional to l2and a term (smaller than the previous one) that is proportional to l4. In agreement with the experimental results, the term proportional to l2increases the pulsewidth of the total electric field over the case of perfect mode-locking and it also gives a positive linear sweep of the field frequency. The pulsewidth increase is expressed by a factor γ that is proportional to the fourth power of the oscillating bandwidth, to the square of the relaxation time T 1 of the dye, and to the product of the length of the active material times a quantity e that is related to dispersion of the material.
34 citations
TL;DR: It is shown that there exists an optimum object-illumination interval, as a function of the object-to-noise power ratio, which minimizes the degradation due to the limited spatial bandwidth of the optical system and results in the extraction of approximately one bit of information per illumination interval.
Abstract: A resolution measure is proposed which is more general than the Rayleigh resolution distance and which takes into account a priori object information and interfering noise. The measure allows evaluation of the quality of an optical system, independent of the class of objects being observed. The resolution of an ideal spatially band-limited optical imaging system is calculated as a function of the object-to-noise power ratio for a number of a priori object statistics. It is shown that there exists an optimum object-illumination interval, as a function of the object-to-noise power ratio, which minimizes the degradation due to the limited spatial bandwidth of the optical system and results in the extraction of approximately one bit of information per illumination interval.
33 citations
Patent•
03 Jun 1969TL;DR: In this paper, the authors describe a series of three BIthis paperRINGENT ELEMENTS of varying thickness with two wave delay ELEMENTS to create an OPTICAL FILTER, which is placed in the light path between an object and a projected image.
Abstract: THE OPTICAL APPARATUS USED IN A TELEVISION SYSTEM, FOR EXAMPLE, INCLUDES A SERIES ARRANGEMENT OF THREE BIREFRINGENT ELEMENTS OF DIFFERENT THICKNESS INTERSPERSED WITH TWO QUARTER WAVE DELAY ELEMENTS TO CONSTITUTE AN OPTICAL FILTER. THE FILTER IS PLACED IN THE LIGHT PATH BETWEEN AN OBJECT AND THE IMAGE FORMED AT THE PHOTOSENSITIVE ELEMENT OF A CAMERA TUBE. THE SPATIAL FREQUENCY BANDWIDTH OF THE LIGHT PASSING THROUGH THE FILTER IS CONTROLLABLE IN ONE OR MORE DIRECTIONS AND IN THE SAME OR DIFFERENT AMOUNTS IN A PLURALITY OF DIFFERENT DIRECTIONS BY SUITABLE DIMENSIONING OF THE BIREFRINGENT ELEMENTS AND/OR BY APPROPRIATE ROTATIONAL POSITIONING OF THE ENTIRE FILTER ABOUT THE OPTICAL AXIS.
32 citations
01 Sep 1969
27 citations
TL;DR: Heterodyne detection with mercury cadmium telluride detectors yielded signal-to-noise ratios within 3 dB of the coherent photon noise limit.
Abstract: A 10.6-μ optical heterodyne communication system is described that uses two stable single mode and single frequency CO2 lasers of high frequency stability. Wavelength control on both lasers allows the use of one and the same transition of the rotation–vibration band of CO2 around 10.6 μ. The system has a bandwidth of 1 MHz, and simultaneous operation in baseband and on a 50-kHz carrier has been achieved. Heterodyne detection with mercury cadmium telluride detectors yielded signal-to-noise ratios within 3 dB of the coherent photon noise limit.
25 citations
05 May 1969
TL;DR: In this paper, the authors proposed a method for correcting the effects of energy dissipation in filters, making their response conform to that of ideal filters, which is particularly noticeable in narrowband bandpass filters used in microwave communications.
Abstract: Predistortion is a standard technique for correcting the effects of energy dissipation in filters, making their response conform to that of ideal filters. The problem of dissipation is particularly noticeable in narrowband bandpass filters used in microwave communications systems. Dissipation makes the passband edges slump downward, as shown in Figure 1, which can cause distortion and intermodulation. In predistorting a filter, we allow for dissipation in the initial design. A response approximating the ideal response can be approximated at the price of increased insertion loss. The flat response of predistorted filters is advantageous when used in high-capacity microwave communications systems; however, the filters have an additional property which makes them especially attractive for certain applications in microwave communications systems.
19 citations
TL;DR: In this article, the feasibility of using the surfacewave transmission line (SWTL) as this link, including its characteristics, launching energy onto the line, coupling to and from the line and communication capacity, is investigated.
Abstract: The potential use of surface waves for the communication and control link with high-speed trains is being studied for the U. S. Department of Transportation, Office of High-Speed Ground Transportation. The results are presented for the first part of this study, which dealt with the feasibility of using the surfacewave transmission line (SWTL) as this link, including its characteristics, launching energy onto the line, coupling to and from the line, and communication capacity. The SWTL shows promise in providing the bandwidth and economy required to meet the demands of a high-speed ground transportation system, without requiring the allocation of space in the crowded radio spectrum.
18 citations
01 Mar 1969
TL;DR: In this paper, an up-converter with gain and stabilized frequency is realized through the sideband locking of an IMPATT oscillator, with an output power of 13.3 dBm over the bandwidth 30 MHz.
Abstract: An up-converter with gain and stabilized frequency can be realized through the sideband locking of an IMPATT oscillator. An up-converter with a gain of 13.3 dB (microwave to microwave) and an output power of 13.3 dBm over the bandwidth 30 MHz is realized and operated at 10.18 GHz.
TL;DR: A digital computer simulation of a double-binary phase-shift keying system to investigate the effects of limiting action and of the shape and bandwidth of the filter on the system performance, expressed in terms of error probability.
Abstract: This paper describes a digital computer simulation of a double-binary phase-shift keying system. This simulation program is used to investigate the effects of limiting action and of the shape and bandwidth of the filter on the system performance, expressed in terms of error probability
TL;DR: In this paper, the problem of designing helical resonators for use in constant-bandwidth tunable filters from VHF through UHF frequencies is approached from two different viewpoints and the conclusions are verified by experimental results.
Abstract: The problem of designing helical resonators for use in constant-bandwidth tunable filters from VHF through UHF frequencies is approached from two different viewpoints and the conclusions are verified by experimental results.
01 Mar 1969
TL;DR: In this paper, a method for obtaining the transient response of a linear time-invariant system is presented, which eliminates the evaluation of the eigenvalues and also involves a minimal number of numerical steps.
Abstract: A novel method for obtaining the transient response of a linear time-invariant system is presented. The main advantages of this method are that it eliminates the evaluation of the eigenvalues and also involves a minimal number of numerical steps. The method is illustrated by a specific example.
01 Aug 1969
TL;DR: Investigation of the problems of obtaining unity gain and dynamic range led to the development of a computer-aided analysis that provides a family of dc transfer characteristics of cascaded p- channel MOS `half-stages' when a variation of either a material or electrical parameter is made.
Abstract: A 16-stage, fixed or variable analog delay line that makes use of integrated p-channel MOS field-effect transistors is described. The delay line relies on `sample' and `hold' techniques and makes use of the inherent characteristics of p-channel MOS transistors. The delay line provides unit gain with a dynamic range of 1 volt. The bandwidth of the delay line is 0.8 MHz under nonsampling conditions. The lowest sampling rate was found to be 50 Hz. A built-in capacitive compensation technique using signals opposite in phase reduces feedthrough of the sampling signal and final filtering requirements. Investigation of the problems of obtaining unity gain and dynamic range led to the development of a computer-aided analysis that provides a family of dc transfer characteristics of cascaded p- channel MOS `half-stages' when a variation of either a material or electrical parameter is made.
01 May 1969
TL;DR: In this paper, a method of analysis, based on solutions to the wave equation, is first developed in general terms and then applied specifically to AT-cut quartz, where boundary conditions are used to determine resonant frequencies and vibration patterns under short-circuit conditions.
Abstract: The monolithic-crystal filter has two or more pairs of electrodes on the same piezoelectric plate; mechanical-wave propagation in the regions between electrodes takes place in an evanescent mode. A method of analysis, based on solutions to the wave equation, is first developed in general terms and then applied specifically to AT-cut quartz. Boundary conditions are used to determine resonant frequencies and vibration patterns under short-circuit conditions; from these, the electrical equivalent circuit is developed. Experimental results confirm the validity of the method. The theoretical results presented describe the bandwidth and motional capacitances of 2- and 3-resonator filters as functions of their geometry (electrode width, thickness and spacing). A method of predicting unwanted resonances is developed. A 3-resonator filter, with a centre resonator of different geometry, is considered. Some results relevant to multiple-resonator filters (up to ten) are described. Extension of the theory to overtone-mode devices is also discussed.
TL;DR: A novel method of measuring driving-point and transfer impedance over a wide spectrum rapidly and with good accuracy uses a digital computer to transform the pulse response of a network into the frequency domain and a sampling oscilloscope provides the time transformation needed for data acquisition.
Abstract: A novel method of measuring driving-point and transfer impedance over a wide spectrum rapidly and with good accuracy uses a digital computer to transform the pulse response of a network into the frequency domain. A sampling oscilloscope provides the time transformation needed for data acquisition. The method and laboratory technique are discussed. Experimental data show agreement within 12 percent between the data from a single pulse measurement and bridge measurements over a band of 40 harmonic frequencies, i.e., 25-1000 MHz. Fundamental accuracy and bandwidth are believed to be substantially greater than these figures.
TL;DR: The FFT computing algorithm, when implemented on a modern digital process computer, provides nearly realtime power spectrum analysis of noise signals, making its use attractive for increasing the safety and availability of complex and expensive reactor systems through on-line monitoring of fluctuations in neutron or gamma flux, system pressure, or mechanical vibration.
Abstract: The FFT computing algorithm, when implemented on a modern digital process computer, provides nearly realtime power spectrum analysis of noise signals. Programmable selection of frequency range, filter center frequencies, and bandwidths makes its use attractive for increasing the safety and availability of complex and expensive reactor systems through on-line monitoring of fluctuations in neutron or gamma flux, system pressure, or mechanical vibration.
TL;DR: In this paper, the effect of antenna discrimination and bandwidth expanding modulation methods upon the total communication capacity in a given frequency band was studied. And the authors concluded that for efficient performance, bandwidth expansion is required; they also concluded that communication capacity can be considerably increased by improving the near side lobe performance of antennas.
Abstract: Radio systems operating at frequencies above 10 GHz are limited to short hops by rain attenuation. A severe interference problem arises from the fact that in a given area many repeaters may mutually interfere through through the back and side lobe responses of their antennas. Introducing the concept of frequency spectrum conservation by maximizing the communication flow through an area, a model of a dense network of radio systems has been studied to determine the effect of antenna discrimination and bandwidth expanding modulation methods upon the total communication capacity in a given frequency band. We conclude that for efficient performance, bandwidth expansion is required; we also conclude that communication capacity can be considerably increased by improving the near side lobe performance of antennas.
TL;DR: In this article, a stochastic model of pseudorandom (PR) signals is adopted and a statistical analysis carried out of the velocity and acceleration tolerances of wide-band PR matched filter sonar systems.
Abstract: A stochastic model of pseudorandom (PR) signals is adopted and a statistical analysis carried out of the velocity (i. e., Doppler) and acceleration tolerances of wide-band PR matched filter sonar systems. The reference functions for these correlation detection systems are considered to be time-compressed or time-expanded replicas of the transmitted signal. Results are derived for the case of a PR signal having a flat power spectral density over a finite bandwidth. It is shown that the velocity and acceleration tolerances are essentially independent of the signal bandwidth and that therefore the radar-derived expressions for the narrow-band tolerances can be extended to the wide-band sonar case. An interesting result is that the derived acceleration tolerance is approximately three times the widely used estimate that is based on the target remaining in the same Doppler channel over the integration time.
Patent•
26 Nov 1969
TL;DR: In this paper, a pulse code modulation system for reducing bandwidth in which voice signal input is compressed, limited, filtered into frequency channels, all of which are converted to the same baseband frequency and are fed to a time sharing multiplexing circuit followed by an analog to digital circuit for transmission.
Abstract: Pulse code modulation system for reducing bandwidth in which voice signal input is compressed, limited, filtered into frequency channels, all of which are converted to the same baseband frequency and are fed to a time sharing multiplexing circuit followed by an analog to digital circuit for transmission. The digital signal is received, converted to analog, demultiplexed, demodulated to voice frequency channels and bandpass filtered. The number of channels applied to the time sharing circuit can be reduced by common band occupancy quadrature carrier methods and then converted to baseband.
TL;DR: In this paper, it was shown that if a switching technique is used to scale the bandwidth of a lowpass filter, the resultant circuit has some of the characteristics of an N-path filter.
Abstract: It is shown that, if a switching technique is used to scale the bandwidth of a lowpass filter, the resultant circuit has some of the characteristics of an N-path filter. The consequence of this is that the signal frequency must be bandlimited to avoid spurious responses at the switching frequency and its harmonics.
Patent•
22 Oct 1969
TL;DR: In this article, a method for complete correction of Doppler shift in a transmitted spectrum of individual frequencies, or tones, constituting a multitone, coded pulse system in which the lowest (reference) and highest frequencies and the bandwidth are known and enclose an information band of frequencies.
Abstract: Method and means for complete correction of Doppler shift in a transmitted spectrum of individual frequencies, or tones, constituting a multitone, coded pulse system in which the lowest (reference) and highest frequencies and the bandwidth are known and enclose an information band of frequencies. The upper and lower half-bands of the received signal are filtered out and mixed to provide the difference frequencies, one of which is a unique frequency corresponding to the spectrum bandwidth. This is filtered out and multiplied by a fixed factor to provide the zero-Doppler reference frequency. The latter is mixed with the information band, which has been filtered from the input signal, and the result is a signal which comprises the information band Doppler-corrected for the reference frequency. The signal corresponding to the spectrum bandwidth is also sent through means which senses the amount of Doppler-shift it has undergone, selects an inverse multiplying factor in accordance with this amount of shift and multiplies the reference-frequency-corrected information band, thereby correcting it for the Doppler-stretch the received information band has undergone. The information band is now completely Doppler-corrected and is divided by a zeroDoppler correction factor to correct the spectral spread introduced by the previous multiplication by said inverse multiplying factor.
05 May 1969
TL;DR: In this paper, the design, construction, and evaluation of a five-resonator, broad-band frequency doubler employing charge-storage diodes is discussed, and the experimental doubler exhibits approximately an octave bandwidth at 50 percent efficiency.
Abstract: Many frequency multipliers can be viewed as consisting of an impedance inverter which couples together impedances at two different frequencies. Using this point of view, the design, construction, and evaluation of a five-resonator, broad-band frequency doubler employing charge-storage diodes is discussed. The doubler is a balanced design, employing two diodes and a balun. Design procedures which relate a low-pass filter prototype to the doubler circuit are presented. Good agreement between theory and experiment has been demonstrated; the experimental doubler exhibits approximately an octave bandwidth at 50 percent efficiency with an input frequency range of 1 to 2 GHz.
TL;DR: The rigorous treatment of the data rate of a multilevel digital FM system is analyzed using frequency-shift keying at the transmitter and ideal discrimination detection with an integrate-and-dump circuit as the post-detection filter.
Abstract: The data rate of a multilevel digital FM system is optimized subject to fixed RF bandwidth, signal-to-noise ratio, and output error rate. The possibility of optimizing such a system was first considered by J. R. Pierce at Bell Telephone Laboratories. He made the observation that it is possible to send many levels slowly or fewer levels rapidly for an FM wave of fixed RF bandwidth and error rate, and that there must be a choice of signaling rate and number of levels that optimize the data rate. The rigorous treatment of this problem is the subject of this paper. The mathematical model we analyze uses frequency-shift keying at the transmitter and ideal discrimination detection with an integrate-and-dump circuit as the post-detection filter. Our results are exhibited graphically showing the various dependencies among the pertinent system parameters.
TL;DR: A receiver for biphase modulated signals using an integrate-and-dump filter is optimum only if the IF filter bandwidth is infinite, and a lower bound on this quantity is determined as a function of the ratio (IF filter bandwidth)/(bit rate).
Abstract: A receiver for biphase modulated signals using an integrate-and-dump filter is optimum only if the IF filter bandwidth is infinite. Finite IF filter bandwidth results is a performance degradation. Using the predetection signal-to-noise ratio as the performance criterion, a lower bound on this quantity is determined as a function of the ratio (IF filter bandwidth)/(bit rate). The corresponding upper bound on the error probability is also presented.
TL;DR: In this paper, the increase in bandwidth potential of a simple parametric amplifier obtained by adding active rather than passive filter elements to the signal circuit is discussed. But the performance of the amplifier was not analyzed.
Abstract: The increase in bandwidth potential of a simple parametric amplifier obtained by adding active rather than passive filter elements to the signal circuit is discussed. Measured performance data of an amplifier constructed for the 4GHz satellite-communication band is given; by using this technique, a sevenfold increase in bandwidth at 20dB gain was obtained
TL;DR: In this article, the case of limiting an incoherent or coherent interference signal at the frequency of a biphase or quadriphase digital signal is analyzed. And the results give the IM products, interference, and attenuation of the digital signal, plus interference through a hard limiter.
Abstract: This paper analyzes the case of limiting an incoherent or coherent interference signal at the frequency of a biphase or quadriphase digital signal. The results give the IM products, interference, and attenuation of the digital signal, plus interference through a hard limiter.
TL;DR: In this paper, a design procedure for optimizing the performance of a varactor upconverter microwave power amplifier with respect to maximum pump efficiency is described, where an optimum diode and circuit parameters and operating levels are given.
Abstract: This paper describes a design procedure for optimizing the performance of a varactor upconverter microwave power amplifier with respect to maximum pump efficiency; the procedure gives explicit diode and circuit parameters and operating levels. An optimum diode is selected by inclusion of an empirical relation between diode breakdown voltage and cutoff frequency. A fully driven abrupt junction diode is assumed. The bandwidth of an upconverter is limited by the intermediate frequency input circuit which typically has a 3 dB bandwidth of about 10 percent. We describe a method of obtaining broadband operation where the interface between the intermediate frequency source and the varactor diode is mismatched in an optimum way. Analysis shows that the frequency variation in mismatch loss just compensates for the frequency variation in upconverter gain predicted by the Rowe-Manley relations. The design procedure is illustrated by a 300 MHz to 10.960 GHz varactor upconverter built for use in the transmitter of the short hop radio system experiment. A bandwidth of 120 MHz between 1.4 dB points represents a bandwidth of more than 40 percent at the intermediate frequency. An output power of +16 dBm was obtained using a pump power of +20 dBm giving a pump efficiency of 40 percent. The normal input to the driver amplifier is +3 dBm giving an overall gain of +13 dB. The upconverter operates over a temperature range of −40°F to +140°F with only a small change in bandshape and output power.