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Journal ArticleDOI

The spectrum of modulated pulses

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.
Citations
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Journal ArticleDOI
TL;DR: A voltage-controlled oscillator (VCO)-based nonuniform sampling (NUS) analog-to-digital converter (ADC) is introduced, which shifts the conventional voltage-domain level crossing to the phase domain, thus eliminating the need for any continuous-time comparator or reference generator.
Abstract: This paper introduces a voltage-controlled oscillator (VCO)-based nonuniform sampling (NUS) analog-to-digital converter (ADC), which shifts the conventional voltage-domain level crossing to the phase domain, thus eliminating the need for any continuous-time (CT) comparator or reference generator. It increases the signal bandwidth and reduces the implementation costs of both analog and digital circuitries compared to the existing voltage-domain NUS ADCs. The signal-to-quantization-noise ratio (SQNR) is improved by the first-order noise shaping and inherent dithering via the free-running oscillation of VCO. The quantization error of the proposed architecture is analyzed, and a phase-domain calibration on the VCO nonlinearity is proposed. Due to the mostly digital architecture and time-based nature of the proposed architecture, the performance and figure of merit (FOM) are expected to improve with the scaled technology. This prototype achieves 200-MHz bandwidth with 60-dB dynamic range (DR) and consumes 19.7 mW of power with an active area of 0.13 mm2 in 65-nm complementary metal–oxide–semiconductor (CMOS), where the nonuniform digital signal processing (DSP) is performed off chip. The estimated power and area of the nonuniform DSP including the calibration and decimation filter are 30 mW and 0.114 mm2, respectively.

27 citations


Cites background from "The spectrum of modulated pulses"

  • ...The details of the PFM operation have been comprehensively analyzed and generalized in [37] and [51]–[53], and further discussion falls outside the scope of this paper....

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  • ...(PFM) [37], [51]–[53] can also be applied to estimate the performance....

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Journal ArticleDOI
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.

26 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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Journal ArticleDOI
TL;DR: In this paper, three approaches to amplitude to pulsewidth conversion are discussed and compared: comparison of the audio signal with a triangle waveform, switching stages with hysteresis and RC feedback, and modified multivibrators.
Abstract: Silicon monolithic circuits are best suited for applications with low power dissipation. Conventional approaches to audio power amplifiers have a rather limited efficiency, and are therefore not necessarily the best choice for integrated circuits. Pulse-width modulation, however, promises an efficiency of up to 100 percent and has several other advantages. Three approaches to amplitude to pulse-width conversion are discussed and compared: comparison of the audio signal with a triangle waveform, switching stages with hysteresis and RC feedback, and modified multivibrators. Possible configurations of output stages are listed. The use of complementary transistors results in higher efficiency and lower distortion.

18 citations

Journal ArticleDOI
TL;DR: In this paper, a hybrid pulse modulation technique was proposed to suppress EMI in a quasi-Z-source converter comprising an impedance-source network and GaN-based H-bridge switching circuit.
Abstract: Rapid voltage and current transitions in switched-mode power converter circuits generate electromagnetic interference (EMI) which may interfere with other electronic systems. High-speed (e.g., wide bandgap) switching devices can improve circuit efficiency and compactness, but may increase the bandwidth of the interference generated. The peak interference is concentrated at harmonics of the fundamental switching frequency, and so may be reduced by modulating the converter switching frequency. However, converter topologies incorporating more than one switching device may not be suited to modulation of the switching frequency, and coordinated modulation of other pulse parameters is required to suppress interference. A relatively simple implementation of a hybrid pulse modulation technique is presented to suppress EMI in a quasi-Z-source converter comprising an impedance-source network and GaN-based H-bridge switching circuit. The technique uses two anharmonically related periodic signals to generate a modulated sawtooth carrier, which in turn generates coordinated switching pulses aperiodically modulated in position and width within a constant switching period. Experimental results demonstrated 10 dB suppression of the peak interference with negligible impact upon the converter's efficiency or output voltage. The proposed pulse modulation technique and its method of implementation are generic, and are expected to be widely applicable to other switched-mode dc–dc power converters.

15 citations


Cites background from "The spectrum of modulated pulses"

  • ...The theoretical basis of EMI suppression by modulating one or more parameters of q(t) is well understood [8]–[10] and the spectrum of several such PWM techniques, including the hybrid PWM presented here, has been calculated analytically [10]....

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Journal ArticleDOI
TL;DR: In this article, the authors considered the effect of random distribution of the i.f. phase at the onset of pulses and evaluated the optimum slicing level to achieve the minimum output noise.
Abstract: Formulae for random noise in the audio-frequency output in pulse-communication receivers are given for pulse-length-, pulse-phase- and pulse-frequency-modulation systems in which the received pulses are sliced; they are also given for pulse-amplitude modulation. Noise resulting from random distribution of the i.f. phase at the onset of pulses is also considered. Optimum slicing level giving minimum output noise is evaluated.Signal/noise ratio and threshold formulae are obtained from these data for the pulse-modulation systems and are compared with those for conventional amplitude- and frequency-modulation systems having the same mean or peak power. Final conclusions as to the merits of all the above systems are drawn from graphs of output signal/noise ratio, in which the performance below threshold is also taken into account.

12 citations

References
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Journal ArticleDOI
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

Journal ArticleDOI
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