The spectrum of modulated pulses
01 Dec 1947-Journal of the Institution of Electrical Engineers - Part IIIA: Radiocommunication (IET)-Vol. 94, Iss: 13, pp 556-564
TL;DR: In this paper, the spectrum of a train of rectangular pulses sinusoidally modulated in any one of these ways is derived, and it is shown that in none of these methods is there any harmonic distortion or audio crosstalk.
Abstract: Some methods proposed for evaluating the spectra of modulated pulse trains are discussed. The basic pulse-frequency, -phase, -length and -amplitude modulation systems are defined and the spectrum of a train of rectangular pulses sinusoidally modulated in any one of these ways is derived. Modulation by more than one tone is also considered. It is shown that in none of these methods is there any harmonic distortion or audio crosstalk. Anharmonic distortion arises from sidebands of harmonics of the pulse repetition frequency, and graphs are given to illustrate its magnitude. The formulae are extended to cover non-rectangular pulses, and it is shown that the distortions to be expected are practically the same as for rectangular pulses. The reproduction of transients is briefly examined. It seems that they suffer little distortion in form but that their timing is modified by the pulse modulation, the maximum time-shift being half the pulse repetition period.
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Citations
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TL;DR: Some results of an analysis of the spectrum of the frequency modulated pulses of the nervous system show that change in average pulse frequency is the likely information-carrying parameter of a neural pulse train.
Abstract: Spectral analysis is one of the more important design and evaluation tools available to the communications engineer and it could also be a key to increased understanding of the nervous system. Some results of an analysis of the spectrum of the frequency modulated pulses of the nervous system show that 1) change in average pulse frequency is the likely information-carrying parameter of a neural pulse train, since distortion-free recovery of this variable is possible by simple low-pass filtering, and 2) phase relationships existing between signal components and distortion components of a neural pulse train imply unusual distortion attenuating properties of multiple or duplicate information channels. These results are discussed in light of some known nervous system structures.
193 citations
01 Dec 1993
TL;DR: In this article, the PTM family is reviewed, a classification system is proposed and their potential for use in high-speed fibre systems intended for the transmission of analogue data is examined.
Abstract: The principal factor in realising a high-performance bandwidth-efficient fibre communication system at an acceptable cost is the choice of modulation format on the optical carrier. In this context, pulse time modulation (PTM) techniques represent an attractive alternative to purely digital or analogue methods. The PTM family is reviewed, a classification system is proposed and their potential for use in high-speed fibre systems intended for the transmission of analogue data is examined.
64 citations
01 Aug 1991
TL;DR: In this article, an enhanced sampling process was proposed to reduce spectral distortion in the output of digital pulse width modulated class D amplifiers, which can be adjusted such that the spectra produced by the process can take a number of forms for the same signal.
Abstract: An enhanced sampling process which can be used to reduce spectral distortion in the output of digital pulse width modulated class D amplifiers is presented. This process arises from a generalisation of the concepts of natural and uniform sampling and can be adjusted such that the spectra produced by the process can take a number of forms for the same signal. Analytical expressions for the spectra produced by the sampling process are derived for both single and double sided modulation. The performance of the process is assessed by case studies on full bandwidth and bass to midrange audio class D amplifiers. It is shown that at carrier frequencies around 88 kHz in a full bandwidth amplifier and 44 kHz in a bass to midrange amplifier the new sampling process will result in significantly lower distortion when compared with either natural or uniform sampling.
56 citations
TL;DR: This paper proposes to study voltage controlled oscillators (VCOs) based on the equivalence with pulse frequency modulators (PFMs) and describes circuit techniques to achieve a good approximation of the required pulse waveforms, which can easily be implemented by practical circuits.
Abstract: In this paper, we propose to study voltage controlled oscillators (VCOs) based on the equivalence with pulse frequency modulators (PFMs). This approach is applied to the analysis of VCO-based analog-to-digital converters (VCO-ADCs) and deviates significantly from the conventional interpretation, where VCO-ADCs have been described as the first-order $\Delta \Sigma $ modulators. A first advantage of our approach is that it unveils systematic error components not described by the equivalence with a conventional $\Delta \Sigma $ modulator. A second advantage is that, by a proper selection of the pulses generated by the PFM, we can theoretically construct an open loop VCO-ADC with an arbitrary noise shaping order. Unfortunately, with the exception of the first-order noise shaping case, the required pulse waveforms cannot easily be implemented on the circuit level. However, we describe circuit techniques to achieve a good approximation of the required pulse waveforms, which can easily be implemented by practical circuits. Finally, our approach enables a straightforward description of multistage $\Delta \Sigma $ modulator architectures, which is an alternative and practically feasible way to realize a VCO-ADC with extended noise shaping.
39 citations
Cites background from "The spectrum of modulated pulses"
...This approach brings new insight, because the spectrum of a PFM signal can be described by a trigonometric series [30]....
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...The signal d(t) is a pulse frequency modulated signal [30]....
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...For a sinusoidal input x(t), the signal d(t) can be expanded into a trigonometric series [29], [30], [33]....
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TL;DR: This letter shows that the discrete Fourier transform of a VCO-ADC output sequence can be calculated analytically for single tone inputs and the SNDR predictions of the proposed model have been compared to behavioral simulations displaying only a deviation of 0.7 dB.
Abstract: Oversampled ADCs based on voltage-controlled oscillators have been analyzed using statistical models inherited from sigma-delta modulation. This letter shows that the discrete Fourier transform of a VCO-ADC output sequence can be calculated analytically for single tone inputs. The calculation is based on the transformation of the VCO output into a pulse frequency modulated signal that can be represented by a trigonometric series. Knowledge of the VCO-ADC output spectrum allows accurate evaluation of the SNDR dependence with the VCO oscillation frequency and gain constant. The SNDR predictions of the proposed model have been compared to behavioral simulations displaying only a deviation of 0.7 dB.
22 citations
Cites methods from "The spectrum of modulated pulses"
...Digital Object Identifier 10.1109/LSP.2014.2357071 In this letter, we propose an analysis complementary to [3], [4], in which a VCO-ADC is first transformed into a pulse frequency modulator whose spectrum is well known [10]–[12]....
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References
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9 citations
01 Feb 1946
TL;DR: In this article, the advantages of duplex transmission were analyzed from the point of view of signal-to-noise ratio, audio fidelity, and transmitter and receiver design. But the advantages were not as great as the ratio offered by the transmission of a standard frequency-modulated carrier.
Abstract: Several pulse methods for the transmission of television sound on the picture carrier during the line-blanking intervals are analyzed from the points of view of signal-to-noise ratio, audio fidelity, and transmitter and receiver design. The advantages of duplex transmission are: (1) elimination of a separate sound transmitter; (2) elimination of the ambiguity and difficulty which may occur when a standard frequency-modulated sound signal is tuned in; (3) freedom of the audio output from the type of distortion which occurs in frequency-modulated receivers as a consequence of excessive drift of the frequency of the local oscillator; and (4) improvement of the phase characteristic of the picture intermediate-frequency amplifier resulting from elimination of trap circuits. The highest audio-modulation frequency in duplex systems must not exceed one half of the line-scanning frequency. This is a disadvantage under the present television standards which specify a line frequency of 15,750 cycles per second. With the exception of pulsed frequency modulation, the signal-to-noise ratios of sound in duplex systems are not so great as the ratio offered by the transmission of a standard frequency-modulated carrier. The comparison is subject to the condition that the amplitude of the frequency-modulated carrier is 0.7 of the peak amplitude of the duplex carrier. The signal-to-noise ratio of a pulsed frequency-modulated signal may equal the ratio of a standard frequency-modulated signal up to a critical distance from the transmitter, but is less at greater distance.
5 citations
01 Jul 1946-Journal of the Institution of Electrical Engineers - Part III: Radio and Communication Engineering
TL;DR: In this paper, the authors describe a television system in which sound pulses having a constant height and variable width are inserted in the line synchronizing periods, which leads to a simplified receiver and improves the program quality in the presence of severe interference.
Abstract: The paper describes a television system in which sound pulses having a constant height and variable width are inserted in the line synchronizing periods. It is claimed that this method of transmission leads to a simplified receiver and that the programme quality is better in the presence of severe interference. Other advantages are that the frequency band-width for transmission is reduced; the method of receiving sound ensures automatic volume control; the sound pulses provide a fixed reference level for automatic volume control on the vision channel; mutual interference between vision and sound often present on two-channel reception is avoided; reduced transmission band-width simplifies the design of the receiving antenna; mutual coupling between the vision and sound antennae at the transmitter is avoided; and the installation and maintenance costs of the sound transmitter are saved. The frequency range of the system operated in conjunction with the pre-war British transmission would be limited to 5 kc/s.
3 citations