An audio FIR-DAC in a BCD process for high power class-D amplifiers

Doorn, T.S.; Tuijl, E.J.M. van; Schinkel, D.; Annema, Anne-Johan; Berkhout, Marco; Nauta, Bram

doi:10.1109/esscir.2005.1541659

Cited by 10 publications

(7 citation statements)

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“…The design method commonly adopted for SDFIR DAC, is to use a standard digital FIR filter design algorithms (e.g. Parks-McClellan algorithm [90]), and choose a practical numerical resolution for the FIR coefficients [116,55,122,125,18,34,66]. The design of linear-phase FIR filters with fractional coefficients are widely discussed in the literature [96,123].…”

Section: Coefficients Precisionmentioning

confidence: 99%

“…Semi-digital FIR filters or sometimes called analog FIR filters, are used as frequency selective filters as well as converting from digital domain to analog domain since it uses analog multipliers as filter taps. The analog multipliers are implemented by means of current sources, in conventional SDFIR filters, if the output of the Σ∆ modulator quantizer is a single bit [116,122,18,34,87,105,124,46,109]. In fact each tap is one-bit DAC and they are weighted according to the filter coefficients.…”

Section: Semi-digital Fir Filtermentioning

confidence: 99%

“…5.1, to an interpolating stage, digital Σ∆ modulator and a semi-digital finite-impulse response (FIR) filter. Semi-digital FIR digital-to-analog converters (SDFIR DAC), used as filters and data converters, are implemented as switched-capacitor network or in current-steering architectures, and reported previously in [116,122,18,34,87,105,124,48,47,46]. In this configuration, N -bit baseband data is up-sampled and filtered through the interpolator and then applied to the digital Σ∆ modulator.…”

Section: Introductionmentioning

confidence: 99%

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Studies on Selected Topics in Radio Frequency Digital-to-Analog Converters

Sadeghifar

2019

Linköping Studies in Science and Technology. Dissertations

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The network latency in fifth generation mobile technology (5G) will be around one millisecond which is much lower than in 4G technology. This significantly faster response time together with higher information capacity and ultra-reliable communication in 5G technology will pave the way for future innovations in a smart and connected society. This new 5G network should be built on a reasonable wireless infrastructure and 5G radio base stations that can be vastly deployed. That is, while the electrical specification of a radio base station in 5G should be met in order to have the network functioning, the size, weight and power consumption of the radio system should be optimized to be able to commercially deploy these radios in a huge network. Last but not least I would like to especially thank my soulmate and my love Hoda. Without all your help, your devotion and patience, I would not be able to complete this work. Therefore, I dedicate this work to you.

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Section: Coefficients Precisionmentioning

confidence: 99%

Section: Semi-digital Fir Filtermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Studies on Selected Topics in Radio Frequency Digital-to-Analog Converters

Sadeghifar

2019

Linköping Studies in Science and Technology. Dissertations

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“…Although, in most telecommunication applications, the attenuation provided by a semi-digital FIR filter in the transmitter path does not totally resolve the out-of-band noise suppression problem, it relaxes the tight requirement on the expensive off-chip SAW filters or the succeeding analog filter. Semi-digital FIR filters, used as filters and data converters and implemented as switched-capacitor network or in current-mode (current-steering) architectures, have been previously reported previously [20,49,50,[57][58][59]. For instance, in [49], a semi-digital FIR filter is designed to target the elimination of the out-of-band noise caused by a preceding second-order Σ∆ modulator.…”

Section: Introductionmentioning

confidence: 99%

On High-Speed Digital-to-Analog Converters and Semi-Digital FIR Filters

Sadeghifar¹

2015

Linköping Studies in Science and Technology. Thesis

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High-speed and high-resolution digital-to-analog converters (DACs) are vital components in all telecommunication systems. Radio-frequency digital-to-analog converter (RFDAC) provides high-speed and high-resolution conversion from digital domain to an analog signal. RFDACs can be employed in direct-conversion radio transmitter architectures. The idea of RFDAC is to utilize an oscillatorypulse-amplitude modulation instead of the conventional zero-order hold pulse amplitude modulation, which results in DAC output spectrum to have highenergy high-frequency lobe, other than the Nyquist main lobe. The frequency of the oscillatory pulse can be chosen, with respect to the sample frequency, such that the aliasing images of the signal at integer multiples of the sample frequency are landed in the high-energy high-frequency lobes of the DAC frequency response. Therefore the high-frequency images of the signal can be used as the output of the DAC, i.e., no need to the mixing stage for frequency upconversion after the DAC in the radio transmitter. The mixing stage however is not eliminated but it is rather moved into the DAC elements and therefore the local oscillator (LO) signal with high frequency should be delivered to each individual DAC element.In direct-conversion architecture of IQ modulators which utilize the RFDAC technique, however, there is a problem of finite image rejection. The origin of this problem is the different polarity of the spectral response of the oscillatorypulse-amplitude modulation in I and Q branches. The conditions where this problem can be alleviated in IQ modulator employing RFDACs is also discussed in this work.Σ∆ modulators are used preceding the DAC in the transmitter chain to reduce the digital signal's number of bits, still maintain the same resolution. By utilizing the Σ∆ modulator now the total number of DAC elements has decreased and therefore the delivery of the high-frequency LO signal to each DAC element is practical. One of the costs of employing Σ∆ modulator, however, is a higher quantization noise power at the output of the DAC. The quantization noise is ideally spectrally shaped to out-of-band frequencies by the Σ∆ modulator. The shaped noise which usually has comparatively high power must be filtered out to fulfill the radio transmission spectral mask requirement.Semi-digital FIR filter can be used in the context of digital-to-analog conversion, cascaded with Σ∆ modulator to filter the out-of-band noise by the modulator. In the same time it converts the signal from digital domain to an analog quantity. In general case, we can have a multi-bit, semi-digital FIR filter where each tap of the filter is realized with a sub-DAC of M bits. The delay elements are also realized with M-bit shift registers. If the output of the modulator is given by a single bit, the semi-digital FIR filter taps are simply controlled by a single switch assuming a current-steering architecture DAC. One of the major advantages is that the static linearity of the DAC is optimum. Since there are only t...

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“…An active low-pass filter after the DAC output can reduce the OBN power to acceptable low levels, but this solution is expensive in terms of power consumption and chip area. A FIR-DAC [1] approach implements a one-bit PWM modulator, followed by a semi-digital lowpass FIR reconstruction filter. It achieves high-end audio performance with sufficiently low OBN, but the FIR structure costs area, adds latency, and (like an analog low-pass filter) inherently limits the maximum output signal frequency.…”

mentioning

confidence: 99%

15.3 A 115dB-DR audio DAC with −61dBFS out-of-band noise

Westerveld

Schinkel²,

Tuijl

2015

2015 IEEE International Solid-State Circuits Conference - (ISSCC) Digest of Technical Papers

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Out-of-band noise (OBN) is troublesome in analog circuits that process the output of a noise-shaping audio DAC. It causes slewing in amplifiers and aliasing in sampling circuits like ADCs and class-D amplifiers. Non-linearity in these circuits also causes cross-modulation of the OBN into the audio band. These mechanisms lead to a higher noise level and more distortion in the audio band. OBN also leads to interference in the LF and MF band, compromising e.g. AM radio reception. To sufficiently avoid these problems, it is desired to reduce OBN power to below -60dBFS. An active low-pass filter after the DAC output can reduce the OBN power to acceptable low levels, but this solution is expensive in terms of power consumption and chip area. A FIR-DAC[1] approach implements a one-bit PWM modulator, followed by a semi-digital lowpass FIR reconstruction filter. It achieves high-end audio performance with sufficiently low OBN, but the FIR structure costs area, adds latency, and (like an analog low-pass filter) inherently limits the maximum output signal frequency. Multi-bit noise shapers employ smaller quantization steps and therefore output lower OBN. The cascaded modulator architecture[2,3] can directly be followed by an onchip amplifier without low-pass filtering. However, with only 330 quantization levels, it still cannot achieve the desired -60dBFS OBN without additional filtering. Moreover, this approach requires complex dynamic element matching (DEM) and inter-symbol interference (ISI) shaping mechanisms.We present an approach that reduces OBN to below -60dBFS with minimal increase in power and area consumption. It consists of two paths ( fig. 1). The main path is based on [4], containing a 128x oversampled 5-bit 3 rd order noise shaper, thermometer decoder and Real-Time DEM algorithm followed by a current DAC. Since the digital noise shaper generates negligible in-band noise products, the error signal of the noise shaper is practically equal to the OBN. This error signal is integrated (as part of the loop filter), quantized and fed to a correction path with a differentiating DAC (DIFF-DAC). This DAC inverts the integration action, obtaining unity signal transfer. The output currents of both paths are subtracted, reducing OBN significantly. Quantization noise of the correction path is shaped because the error signal is differentiated after quantization. Depending on the shape of the noise transfer function of the main DAC, the DIFF-DAC needs an overrange in order to accommodate the increased signal swing caused by the integration action. Still, area and power cost is minimal because the range of the DIFF-DAC is still only a fraction of the main DAC range.The DIFF-DAC is a semi-digital FIR-DAC with a 1-z A demonstrator chip was designed and manufactured in a 180nm CMOS process. The interpolation filters and the noise shaper were implemented in an FPGA for flexibility. The digital part of the chip contains the 5-bit thermometer decoder, the Real-Time DEM algorithm and the logic circuitry for the DIFF-DAC. To obtain ...

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An audio FIR-DAC in a BCD process for high power class-D amplifiers

Cited by 10 publications

References 4 publications

Studies on Selected Topics in Radio Frequency Digital-to-Analog Converters

Studies on Selected Topics in Radio Frequency Digital-to-Analog Converters

On High-Speed Digital-to-Analog Converters and Semi-Digital FIR Filters

15.3 A 115dB-DR audio DAC with −61dBFS out-of-band noise

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An audio FIR-DAC in a BCD process for high power class-D amplifiers

Cited by 10 publications

References 4 publications

Studies on Selected Topics in Radio Frequency Digital-to-Analog Converters

Studies on Selected Topics in Radio Frequency Digital-to-Analog Converters

On High-Speed Digital-to-Analog Converters and Semi-Digital FIR Filters

15.3 A 115dB-DR audio DAC with &#x2212;61dBFS out-of-band noise

Contact Info

Product

Resources

About

15.3 A 115dB-DR audio DAC with −61dBFS out-of-band noise