A configurable sampling rate converter for all-digital 4G transmitters

Roverato, Enrico; Kosunen, Marko; Lemberg, Jerry; Nieminen, Tero; Stadius, Kari; Ryynänen, Jussi; Eloranta, P.; Kaunisto, R.; Pärssinen, Aarno

doi:10.1109/ecctd.2013.6662279

Cited by 9 publications

(10 citation statements)

References 13 publications

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“…the carrier frequency f c is twice the digital sampling rate f s ). A configurable fractional interpolation chain that efficiently converts the base sampling rate of LTE signals to the gigahertz-range carrier-dependent sampling rate needed at the RF-DAC input has been published in [6].…”

Section: System-level Simulationsmentioning

confidence: 99%

“…Theoretically, the problem could be straightforwardly solved by increasing the effective number of bits (ENOB) of the converter [5]. However, the maximum ENOB that can be achieved without calibration is typically around 10-12 bits, which is not sufficient to meet the tight RX-band noise requirement [6]. Hence, such a solution is controversial to the objectives of digital RF, i.e.…”

Section: Introductionmentioning

confidence: 99%

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RX-Band Noise Reduction in All-Digital Transmitters With Configurable Spectral Shaping of Quantization and Mismatch Errors

Roverato¹,

Kosunen²,

Lemberg³

et al. 2014

IEEE Trans. Circuits Syst. I

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This paper describes the first purely digital approach to reduce the receive band noise in digitally-intensive RF transmitters. The proposed solution applies bandpass deltasigma modulation and dynamic element matching (DEM) to the receive band (RX-band) instead of the transmit band. This enables selective attenuation of the noise originating from amplitude quantization and static mismatches of the digitalto-analog converter (DAC), which would otherwise reach the transmitter output almost unattenuated. A highly configurable 4 th-order noise transfer function is designed to achieve optimum attenuation in the programmable RX-band, while ensuring negligible degradation of the transmitted signal quality as well as stable operation of the tree structure DEM encoder. A general validation of DEM, independent from the duration of the DAC impulse response, is also presented. The proposed solution is verified through system-level simulations with LTE signals. In the presence of typical amplitude and timing mismatches, the RXband noise can be reduced below-160 dBc/Hz without filtering after the DAC, thus potentially enabling SAW-less operation of all-digital transmitters.

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Section: System-level Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

RX-Band Noise Reduction in All-Digital Transmitters With Configurable Spectral Shaping of Quantization and Mismatch Errors

Roverato¹,

Kosunen²,

Lemberg³

et al. 2014

IEEE Trans. Circuits Syst. I

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“…However, the transmitter fails at achieving low OOB emissions for SAW-less operation. As demonstrated in [7], ENOB up to 13 is needed to push the unfiltered quantization noise reaching the RF output below the typical limit of -160 dBc/Hz. Spectral densities of the input/output signals for (a) binary/thermometer encoder, and (b) mismatch-shaping encoder.…”

Section: Programmable Rx-band Noise Shapingmentioning

confidence: 99%

“…The baseband I/Q data is generated offline and loaded into a 16k-word memory, from where it can be streamed to the rest of the TX chain. Even though ENOB of 13 is sufficient for OOB quantization noise below -160 dBc/Hz [7], the wordlength of I BB and Q BB at the memory output is 15 bits, in order to leave enough margin for roundoff errors in the DSP part. The outputs of the I and Q paths are combined on-chip through an RF balun, designed to match 50Ω external load in the low-band (0.7-1.0 GHz) of the cellular radio spectrum.…”

Section: Circuit Implementationmentioning

confidence: 99%

“…The first is the digital repetition spectrum, attenuated only by the sinc response of the D/A converter's zero-order hold. This can be successfully handled by increasing the oversampling ratio (OSR) of the digital baseband signal, which is well supported by deep-submicron CMOS processes [7]- [15]. The second issue is the DAC quantization noise.…”

Section: Introductionmentioning

confidence: 99%

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All-Digital LTE SAW-Less Transmitter With DSP-Based Programming of RX-Band Noise

Roverato

Kosunen

Cornelissens³

et al. 2017

IEEE J. Solid-State Circuits

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We present the first all-digital LTE transmitter using programmable digital attenuation of RX-band noise. The system is architectured to fully exploit the speed and low cost of DSP logic in deep-submicron CMOS processes, without increasing at all the design effort of the RF circuitry. To achieve SAWless operation, the transmitter uses digital bandpass delta-sigma modulation and mismatch-shaping to attenuate the DAC noise at a programmable duplex distance. These functions can be implemented entirely within DSP, thus taking advantage of the standard digital design methodology. Furthermore, the fully digital RX-band noise shaping significantly relaxes the performance requirements on the RF front-end. Therefore, 10 bits of resolution for the D/A conversion are sufficient to achieve-160 dBc/Hz out-of-band noise, without need for digital predistortion, calibration or bulky analog filters. The transmitter was fabricated in 28nm CMOS, and occupies only 0.82 mm 2. Besides low outof-band noise, our system also demonstrates state-of-art linearity performance, with measured CIM3/CIM5 below-67 dBc, and ACLR of-61 dBc with LTE20 carrier. The circuit consumes 150 mW from 0.9/1.5V supplies at +3 dBm output power.

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