An FPGA-based all-digital transmitter with 28-GHz time-interleaved delta-sigma modulation

Tanio, Masaaki; Hori, Shingo; Tawa, Noriaki; Yamase, Tomoyuki; Kunihiro, Kazuaki

doi:10.1109/mwsym.2016.7540142

Cited by 16 publications

(9 citation statements)

References 5 publications

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“…The needed complex zero can be obtained by simply replacing the coefficients r and c from (5) with the values corresponding to the targeted normalized frequency (fn), which can be obtained using the relationship between the z-transform and the Fourier transform in (6). (6) where A is the modulus of the complex number z.…”

Section: A General Architecture Of 1 St Order Cdsmmentioning

confidence: 99%

“…Therefore, using this CDSM scheme, the denominator from (7-8) is reduced to a simple delay z -1 (independent of r and c, no complex coefficients), whereas the numerator in (8) remains identical to (5) and enables the placement of the custom complex zero according to (6).…”

Section: B Proposed 1 St Order Cdsmmentioning

confidence: 99%

“…Secondly, the sign of the imaginary part determines the position of the custom zero, namely if Im(z) > 0, then the normalized frequency is fz > 0. Finally, the normalized frequency can be obtained using (6), for example in the case of z1 = 0.25+0.97j, fz1 ≈ 0.21.…”

Section: B Proposed 1 St Order Cdsmmentioning

confidence: 99%

“…digital signal processing based on Delta-Sigma Modulators (DSM) can enable the use of highly-efficient power amplifier stages in a digital transmitter. Moreover, techniques such as time-interleaving (TI) [5] and multi-channel look-ahead [6] can be employed in order to overcome DSM integration challenges and increase the maximum operating frequency. As a result, it is shown in [6] that an FPGA implementation of a TI DSMbased all-digital transmitter can reach a maximum effective sampling frequency of 28 GHz and meet the transmit mask of IEEE 802.11a WLAN standard in the 5.2 GHz band.…”

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confidence: 99%

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Digital Complex Delta–Sigma Modulators With Highly Configurable Notches for Multi-Standard Coexistence in Wireless Transmitters

Marin

Frappé

2018

IEEE Trans. Circuits Syst. I

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This paper presents a Complex Delta-Sigma Modulator (CDSM) designed for the integration in a digital transmitter chain targeting multi-standard coexistence with nearby receivers. The use of a Delta-Sigma Modulator (DSM) has the advantage of increased performances in terms of signal-tonoise-ratio (SNR) in the band of interest. However, the resulting out-of-band noise becomes an issue for multi-standard coexistence, thus increasing the complexity of the succeeding filtering stage. These constraints could be relaxed in the DSM stage, by placing a complex zero near the frequency band, where a low noise level is needed. This is achieved by cross-coupling the In-phase (I) and Quadrature (Q) channels, thus obtaining a CDSM. A review of known design methods for CDSM revealed limitations regarding the poles/zeros optimization, and the configurability of the complex zeros placement. The proposed architecture introduces two additional cross-couplings from the I and Q quantizers' outputs in order to decorrelate the zeros placement and the poles optimization problem. Hence, the improved CDSM can be implemented using existing optimization tools, which reduces considerably the number of iterations and the computational effort. In addition, the resulting modulator can target different coexistence scenarios without the need of redesign, unlike other known methods. Simulation results show a noise level reduction of approximately 20-30 dB near specific frequency bands by the proposed CDSM scheme with respect to standard DSM. Finally, we show an efficient fine/coarse configurability mechanism, which is obtained when introducing additional delays in the cross-coupling paths. Index Terms-Delta Sigma Modulator (DSM), Complex Delta Sigma Modulator (CDSM), finite impulse response (FIR), multistandard coexistence, digital transmitter; I. INTRODUCTION ECENT progress in advanced CMOS integrated digital transmitter (TX) architectures [1] [2] has been focusing on reducing the power consumption and circuit area to follow the trend of increased data rates and signal bandwidths (BW) in communication standards, e.g. IEEE 802.11 standard.

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Section: A General Architecture Of 1 St Order Cdsmmentioning

confidence: 99%

Section: B Proposed 1 St Order Cdsmmentioning

confidence: 99%

Section: B Proposed 1 St Order Cdsmmentioning

confidence: 99%

mentioning

confidence: 99%

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Digital Complex Delta–Sigma Modulators With Highly Configurable Notches for Multi-Standard Coexistence in Wireless Transmitters

Marin

Frappé

2018

IEEE Trans. Circuits Syst. I

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“…As a cornerstone of SDR, all-digital RF transceiver based on delta-sigma modulation has attracted intensive research interest due to its low cost and flexibility to accommodate multiband multi-RAT operations. Both transmitter [30]- [52] and receiver [53]- [59] designs have been reported, and various delta-sigma modulators, including lowpass [30], [32]- [34], [36]- [39], [41]- [45], [47], [48], bandpass [31], [35], and multiband [40], [49]- [52] have been demonstrated. To relax the FPGA speed requirement, several time-interleaving or parallel processing techniques are also presented [38], [39], [43]- [45], [47], [48].…”

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confidence: 99%

Delta-Sigma Modulation for Next Generation Fronthaul Interface

Wang

Jia

Campos

et al. 2019

J. Lightwave Technol.

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A new function split option for the next generation fronthaul interface (NGFI) is demonstrated based on all-digital RF transmitter using bandpass delta-sigma modulation. Different from other low layer split (LLS) options, such as option 6 (MAC-PHY), 7 (high-low PHY), and 8 (CPRI), the proposed option 9 implements RF functions in the digital domain, and splits within the RF layer, with high-RF layer centralized in the distributed unit (DU) and low-RF layer distributed in remote radio units (RRUs). A proof-of-concept all-digital RF transmitter based on real-time delta-sigma modulation is implemented using a Xilinx Virtex-7 FPGA. A 5-GSa/s delta-sigma modulator is demonstrated to encode LTE/5G signals with bandwidth up to 252 MHz and modulation format up to 1024-QAM to a 5-Gb/s OOK signal, which is transmitted over 30-km single-mode fiber from DU to RRU. To relax the FPGA speed requirement, a 32-pipeline architecture is designed. Two-carrier aggregation of 5G and 14-carrier aggregation of LTE signals are demonstrated with error vector magnitude (EVM) performance satisfying the 3GPP specifications. Compared with option 8 (CPRI), although the proposed option 9 split occurs at a lower level, it offers improved spectral efficiency and reduced NGFI data rate than CPRI. Moreover, other LLS options, such as 6, 7, and 8, all require a complete RF layer implemented in the analog domain at remote cell sites; whereas option 9 realizes high-RF layer in the digital domain at DU, and eliminates the need of analog RF devices, such as DAC, local oscillator and mixer at RRU, which not only makes low-cost, energy-efficient, and small-footprint cell sites possible for the wide deployment of small cells, but also paves the road toward software defined radio (SDR) and virtualization of DU and RRU for improved compatibility and reconfigurability among multiple radio access technologies (multi-RATs). Given its centralized architecture and deterministic latency, option 9 is suitable for radio coordination applications, and has potential in low-frequency narrowband scenarios with cost, power, and/or size sensitive cell sites, such as massive machine type communication (mMTC) and narrowband internet of things (NB-IoT). Index Terms-All-digital RF transmitter, delta-sigma modulation, fronthaul, NGFI, software defined radio. I. INTRODUCTION T HE emerging video-intensive and bandwidth-consuming services, e.g., virtual reality, augmented reality, immersive applications, are driving the explosive growth of mobile data traffic [1]-[3], making radio access networks (RAN) become

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Wideband 1-Bit Bandpass Delta Sigma Modulator Using Elliptic Filter in Noise Transfer Function

Maehata

Suematsu

2022

IEEE Access

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A 1-bit band-pass delta-sigma modulator (BP-DSM), which utilizes oversampling technology, allows a modulated signal to be directly output by using a high-speed 1-bit digital pulse train, thus realizing miniaturization of transmitters. For 1-bit BP-DSM, the noise transfer function (NTF) is used to suppress quantization noise power in the transmission band and a guideline of out-of-band gain of |NTF|< 1.5 is used to prevent oscillation. However, in previous studies, such as Butterworth and inverse Chebyshev filters, the out-of-band gain was designed indirectly by tuning the zeros and poles in the transmission band and thus, was not stabilized sufficiently. Furthermore, even though the zeros of the NTF are identical to the poles of the loop filter, there are still widely used designs in which the zeros are set on the unit circle, making stabilization quite difficult. Therefore, in this paper, we propose a feasible implementation of the NTF for 1-bit BP-DSM with an elliptic filter that can be used to set not only in-band but also out-of-band gain, in which both the zeros and poles are set inside the unit circle. As a design result, a modulation bandwidth of 400 MHz as a relative bandwidth of 11%, a noise suppression bandwidth of 800 MHz, and an adjacent channel leakage power ratio of 50 dB were achieved at a center frequency of 3.6 GHz, enabling a wider bandwidth and higher SNR than before by improving the stability.INDEX TERMS Delta-sigma modulator, quantization, 5G mobile communication, software defined radio, wideband.

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An FPGA-based all-digital transmitter with 28-GHz time-interleaved delta-sigma modulation

Cited by 16 publications

References 5 publications

Digital Complex Delta–Sigma Modulators With Highly Configurable Notches for Multi-Standard Coexistence in Wireless Transmitters

Digital Complex Delta–Sigma Modulators With Highly Configurable Notches for Multi-Standard Coexistence in Wireless Transmitters

Delta-Sigma Modulation for Next Generation Fronthaul Interface

Wideband 1-Bit Bandpass Delta Sigma Modulator Using Elliptic Filter in Noise Transfer Function

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