Dual-clock MASH delta-sigma modulator employing a frequency modulated intermediate signal

Maezawa, Koichi; Sakou, M.; Matsubara, W.; Mizutani, Takashi

doi:10.1587/elex.3.459

Cited by 3 publications

(2 citation statements)

References 6 publications

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“…Recently, another type of the DSM, called Frequency Delta-Sigma Modulator (FDSM), has attracted considerable attention, which uses a voltage controlled oscillator (VCO) [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. The FDSM uses an intermediate frequency modulation (FM) signal that is generated by the VCO, and it has no feedback DAC or integrator.…”

Section: Introductionmentioning

confidence: 99%

Noise Floor Reduction in Frequency Delta-Sigma Modulation Microphone Sensors

Maezawa

Mori

Andoh

2021

Sensors

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Frequency delta-sigma modulator (FDSM) employing a variable frequency oscillator is a novel replacement of the classical delta-sigma modulators. This is advantageous for application to sensors, because an ADC can be intrinsically integrated with the sensors. We have already proposed to use this technique to various sensors. However, the signal-to-noise ratio was significantly degraded by noise floor, in the previous papers. In this paper, we have investigated the origin of the noise floor in the FDSM microphone sensors as a promising example. It was demonstrated that improving the phase noise of the oscillator can drastically reduce the noise floor. For this reduction we improved the Q-factor of the cavity resonator, and the design of the oscillator circuit. With these improvements, the phase noise, and, hence, the noise floor, were improved by approximately 40 dB. In addition, we obtained an SNR of 57 dB for 114 dBSPL sound input with 96 kHz bandwidth, which corresponds to the dynamic range of 87 dB for maximum 140 dBSPL. A much larger dynamic range of around 120 dB is expected by increasing the sampling rate and decreasing the Al diaphragm thickness. These results also indicate the promise of the FDSM to varieties of physical sensors.

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Section: Introductionmentioning

confidence: 99%

Noise Floor Reduction in Frequency Delta-Sigma Modulation Microphone Sensors

Maezawa

Mori

Andoh

2021

Sensors

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“…The DSM is a most significant part in the DSADC, which determines the ADC performance. The frequency DSM (FDSM) using a frequency modulated (FM) intermediate signal [1][2][3][4][5][6] is a promising technique when applying the DSADC to sensors. It uses an oscillator instead of the integrator and D/ A converter used in the conventional DSM, so that very simple and low noise implementation is possible.…”

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confidence: 99%

Delta‐sigma modulation microphone sensors using microwave cavity resonator

et al. 2016

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The frequency delta-sigma modulation (FDSM) technique was applied to the microphone sensors. The FDSM is a superior analogue-to-digital conversion technique, which outputs wide band, large dynamic range digital signals without precision analogue components. In this implementation, a microwave cavity resonator having movable membrane on its one end, together with a gain block consisting of a heterojunction field effect transistor, was used for sound-frequency converter. The output of this converter (frequency modulated intermediate signal) was sampled and converted to 1-bit delta sigma modulated digital signals. The noise shaping behaviour with a clear signal peak was demonstrated for the fabricated devices.

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Effects of Oscillator Phase Noise on Frequency Delta Sigma Modulators with a High Oversampling Ratio for Sensor Applications

Maezawa

Mori

2021

IEICE Trans. Electron.

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Frequency delta sigma modulation (FDSM) is a unique analog to digital conversion technique featuring large dynamic range with wide frequency band width. It can be used for high performance digitaloutput sensors, if the oscillator in the FDSM is replaced by a variable frequency oscillator whose frequency depends on a certain external physical quantity. One of the most important parameters governing the performance of these sensors is a phase noise of the oscillator. The phase noise is an essential error source in the FDSM, and it is quite important for this type of sensors because they use a high frequency oscillator and an extremely large oversampling ratio. In this paper, we will discuss the quantitative effects of the phase noise on the FDSM output on the basis of a simple model. The model was validated with experiments for three types of oscillators.

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Dual-clock MASH delta-sigma modulator employing a frequency modulated intermediate signal

Cited by 3 publications

References 6 publications

Noise Floor Reduction in Frequency Delta-Sigma Modulation Microphone Sensors

Noise Floor Reduction in Frequency Delta-Sigma Modulation Microphone Sensors

Delta‐sigma modulation microphone sensors using microwave cavity resonator

Effects of Oscillator Phase Noise on Frequency Delta Sigma Modulators with a High Oversampling Ratio for Sensor Applications

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