Shintaro Shinjo

Concurrent Multiband Digital Outphasing Transmitter Architecture Using Multidimensional Power Coding

All-digital outphasing transmitter architecture using multidimensional power coding (MDPC) is proposed for noncontiguous concurrent multiband transmission with a high power efficiency. MDPC transforms multiband digital baseband signals into multibit low-resolution digital signals that drive switching-mode PAs. A prototype digital outphasing transmitter consists of two 1-GHz bandwidth GaN Class-D PAs and a Chireix power combiner. The two GaN PAs are driven by bipolar radio frequency (RF) pulse-width modulation (PWM) signals, which are transformed from a concurrent dual-band LTE signal by MDPC. The dual-band LTE signal with 15-MHz aggregate channel bandwidth at 240 and 500 MHz frequency band is transmitted with -30 and -37 dBc out-of-band emissions, respectively. Digital outphasing achieves more than two times higher coding efficiency than conventional concurrent dual-band digital transmitters with the same PAs in Class-S operation. Measured power coding efficiencies of 35.4% and 47.1% are observed with outphasing bipolar and 3-level RF PWM signals respectively, which are encoded from the dual-band LTE signal.

Over 65% PAE GaN voltage-mode class d power amplifier for 465 MHz operation using bootstrap drive

We report a digitally-driven switching-mode amplifier using GaN devices in Voltage-Mode Class D operation, for use at 465 MHz (the recently designated frequency for LTE Band 31). The amplifier is fabricated as an integrated circuit including output devices and drivers. The output circuit employs two stacked GaN FETs; a bootstrap-drive configuration is used in order to increase the driver-stage efficiency for the uppermost GaN FET. The GaN VMCD amplifier achieves peak power-added efficiency of 66.6%, and an output power of 3.3W. At 6dB power backoff, power-added efficiency of 36.3% is achieved. These power-added efficiency values are the highest for reported GaN VMCD amplifiers at a commercial wireless frequency.

An L-band high efficiency and low distortion power amplifier module using an HPF/LPF combined interstage matching circuit

A three stage high power amplifier (HPA) module for wide-band CDMA handy phones using an HPF/LPF combined interstage matching circuit has been developed. An HPF/LPF combined interstage matching circuit can realize both the optimum load impedance of the second stage FET and the optimum source impedance of the third stage FET to achieve high efficiency. The developed three stage HPA module, size of which is 0.08cc (7 mm/spl times/7 mm./spl times/1.7 mm), achieves a power-added efficiency of 43.9% and an output power of 27.1 dBm with an adjacent channel leakage power (ACP) of -38 dBc at 1.95 GHz.

Integrating the Front End: A Highly Integrated RF Front End for High-SHF Wide-Band Massive MIMO in 5G

Fifth-generation (5G) mobile communications will need to accommodate huge traffic demands in the near future. Massive multipleinput/multiple-output (MIMO) technology utilizing hundreds of antenna elements has drawn attention as a key antenna configuration for envisioned 5G applications. Realizing the massive MIMO concept of active phased-array antennas (APAAs) for 5G will require small-size, low-power-consumption, and highly accurate phase control over the wide-band frequency range, which poses significant challenges for the RF front end. This article describes prototyped highly integrated RF front ends for high super-high-frequency (SHF) wide-band massive MIMO in 5G.

ASK and Pi/4-QPSK dual mode SiGe-MMIC transceiver for 5.8GHz DSRC terminals having stabilized amplifier chain

A high integrated SiGe-MMIC transceiver having voltage controlled oscillator (VCO), phase locked loop (PLL), dual-transmit block for amplitude shift keying (ASK) mode and pi/4-quadrature phase shift keying (QPSK) mode, and common receiver block for the dual modes is developed for 5.8GHz dedicated short range communications (DSRC) terminals. To obtain stability of transceiver using differential configuration, which has on-chip closed loops generated by common ground/V CC pad arrangement and differential pairs, the stabilized MMIC design method based on the loop analysis is introduced to it. In the loop analysis, the both on-chip loops of differential mode and common mode are considered, the maximum loop gain of less than -3dB all over the frequency range is defined as the absolute stabilized condition. The simulated results for each loops show that isolation resistors inserted in bias feed line are effective for improving the stability. The effectiveness of the design method is evaluated by the measured results. The SiGe-MMIC transceiver having the stabilized amplifier chain is fabricated in 0.35μm SiGe-BiCMOS, and it achieves the adjacent channel power ratio (ACPR) of −38.2dBc under the ASK modulation and that of −47.2dBc under the pi/4-QPSK modulation.

An L-band high-efficiency and low-distortion power amplifier using HPF/LPF combined interstage matching circuit

An L-band high-efficiency and low-distortion power amplifier using a high-pass filter/low-pass filter (HPF/LPF) combined interstage matching circuit is presented in this paper. An HPF/LPF combined interstage matching circuit can realize both the optimum load impedance of the driver-stage FET and the optimum source impedance of the final-stage FET to achieve high efficiency with a specified distortion. The circuit has been utilized in a three-stage high-power-amplifier module, the size of which is 0.08 cm/sup 3/ (7 mm/spl times/7 mm/spl times/1.7 mm). The amplifier achieves a power-added efficiency of 43.9% and an output power (P/sub out/) of 27.1 dBm with an adjacent channel leakage power of -38 dBc at 1.95 GHz for wide-band code-division multiple-access cellular phones.

A highly integrated RF frontend module including Doherty PA, LNA and switch for high SHF wide-band massive MIMO in 5G

A highly integrated RF frontend module including a three-stage power amplifier (PA), a two-stage low noise amplifier (LNA) and a switch (SW) is presented for high SHF wide-band massive MIMO in 5G. In order to achieve efficient operation over wide-band frequency, Doherty PA configuration using a parasitic output capacitance neutralization technique is proposed for final stage PA. To improve LNAs gain flatness over wide frequency band, two R-LC stabilization circuits with different resonance frequencies are proposed. They are fabricated with 0.15-μm GaAs process, and integrated into a 5 × 5 mm2 QFN package. The state-of-the-art measured results show that final stage PA and three-stage PA achieve a drain efficiency (DE) at 8dB back-off of more than 22 % and 12 %, respectively, and a two-stage LNA achieves a noise figure (NF) of less than 1.4dB over 14.5–15.0 GHz.

Static sequence assisted out-of-band power suppression for DFT-s-OFDM

A novel static sequence assisted discrete Fourier transform (DFT)-spread-orthogonal frequency division multiplexing (OFDM) waveform is proposed to suppress out-of-band (OoB) emission. In the proposed scheme, a deterministic sequence, which functions as cyclic prefix (CP), is used to suppress OoB emission. A measure of continuity is proposed to determine the location of the static sequence to maximize the amount of OoB suppression. Perturbation is added to the static sequence to further improve phase continuity at block transitions. It is shown that the spectra of the proposed static sequence assisted waveforms are more compact that those of the conventional waveforms. A frequency offset estimation method using the static sequence is described and its performance is evaluated by simulations.

Inter-band carrier aggregation digital transmitter architecture with concurrent multi-band delta-sigma modulation using out-of-band noise cancellation

Concurrent multi-band delta-sigma modulation (CMB-DSM) with out-of-band noise cancellation is presented for the first time. A scaled replica modulator creates anti-phased quantization noise for multi-band noise cancellation, consequently reducing adjacent channel leakage and significantly relaxing the design of a multi-band RF filter to suppress undesirable out-of-band emission. A prototype digital transmitter is designed with 6th-order CMB-DSM using a loop filter with stability compensation. Experimental results show that the proposed noise cancellation technique achieves more than 15-dB suppression on the out-of-band quantization noise with LTE inter-band carrier aggregation (CA) on 856 MHz and 1450 MHz bands with 40-MHz aggregated channel bandwidth.

A fully analog two-way sequential GaN power amplifier with 40% fractional bandwidth

In this paper, we report a two-way sequential power amplifier (SPA) using GaN HEMTs. The proposed fully analog SPA delivers Psat of approximately 40dBm over 2-3 GHz covering 40% fractional bandwidth. The design consists of a 3dB input coupler, a main amplifier, a peak amplifier, and a 10dB output coupler for power combining. After proper designing and optimizing these critical wideband couplers in terms of both phase and amplitude alignment, the measured final SPA shows 45% to 61% drain efficiency (DE) at 35dBm (5dB backoff) output from 2.1 to 2.9 GHz under CW stimulus. A complete set of SPA with analog RF input and output network is demonstrated.