Farshid Aryanfar

Millimeter-wave beamforming as an enabling technology for 5G cellular communications: theoretical feasibility and prototype results

The ever growing traffic explosion in mobile communications has recently drawn increased attention to the large amount of underutilized spectrum in the millimeter-wave frequency bands as a potentially viable solution for achieving tens to hundreds of times more capacity compared to current 4G cellular networks. Historically, mmWave bands were ruled out for cellular usage mainly due to concerns regarding short-range and non-line-of-sight coverage issues. In this article, we present recent results from channel measurement campaigns and the development of advanced algorithms and a prototype, which clearly demonstrate that the mmWave band may indeed be a worthy candidate for next generation (5G) cellular systems. The results of channel measurements carried out in both the United States and Korea are summarized along with the actual free space propagation measurements in an anechoic chamber. Then a novel hybrid beamforming scheme and its link- and system-level simulation results are presented. Finally, recent results from our mmWave prototyping efforts along with indoor and outdoor test results are described to assert the feasibility of mmWave bands for cellular usage.

A Broadband Stacked Power Amplifier in 45-nm CMOS SOI Technology

A fully integrated broadband power amplifier (PA) is implemented in a standard 45-nm CMOS SOI technology. The PA is designed using a dynamically biased stacked SOI transistor approach, which constructively adds drain-source voltage signals of individual transistors while keeping their gate voltages within source and drain voltage limits. The design overcomes both low gate-oxide breakdown and low source-drain reach through voltages of nanoscale CMOS transistors. The number, size, and topology of transistors in the stack are optimized to deliver a relatively high linear output power over a wide range of frequencies. The amplifier under a supply voltage of 4.5 V measures a flat gain of 6 dB with -1-dB bandwidth of 6 to 26.5 GHz ( X-band to K-band). At 18 GHz, the PA under a supply voltage of 7.2 V measures a saturated output power (PSAT) of 26.1 dBm ( ~ 400 mW), a linear output power (P1 dB) of 22.5 dBm, and a peak power-added efficiency (PAE) of 11%. With a lower power supply voltage of 4.5 V, the PAE increases to more than 20% and stays above 17% with relatively constant PSAT and P1 dB for several measured frequencies in the range of 6 to 20 GHz. The PA occupies an active chip area of only 0.16 mm2.

Millimeter-wave base station for mobile broadband communication

In this paper a millimeter-wave base station operating at 28GHz for mobile communication is introduced. This base station employs 64-elements antenna phased-array to enable adaptive beamforming required for mobile communication. The phased-array is constructed of sub-arrays for optimal trade-off between performance and required coverage and beamforming capability. The phased array antenna is integrated with the transceivers on the same printed circuit board (PCB) using industry standard manufacturing process to minimize the cost and routing loss. The achieved link budget fulfills the requirements of the LOS and NLOS mobile communication in this band for distances in excess of 1Km. The field measurements depict an end-to-end EVM of better than -24dB for a 16QAM OFDM signal with 500MHz bandwidth (BW).

A Ka-Band doherty power amplifier with 25.1 dBm output power, 38% peak PAE and 27% back-off PAE

We present the design and development of the first fully integrated, two stage Doherty power amplifier (DPA) in the Ka-Band. The DPA is fabricated in a 0.15-μm GaAs pseudomorphic high electron mobility transistor (pHEMT) process. At 26.4 GHz, the amplifier achieves measured small signal gain of 10.3 dB, output power at 1-dB compression point (P1dB) of 25.1 dBm, peak power added efficiency (PAE) of 38%, and PAE of 27% at 6 dB back-off power. To the best of the authors knowledge, this Doherty circuit is the first fully integrated millimeter-wave amplifier that achieves the highest power and a recorded 27% PAE at 6-dB back-off and each unit amplifier has 2 stages.

Millimeter-wave open ended SIW antenna with wide beam coverage

In this paper, a mm-wave open ended SIW antenna on the edge of a multilayer PCB is demonstrated. The designed antenna features 180° and 90° 3dB beamwidth in E- and H-planes, respectively, covering one quarter of the entire space. The antenna is designed compatible with traditional PCB fabrication. Through vias are used as a mean to convert microstrip mode to SIW cavity mode. V-shaped notches are cut on top and bottom walls of the SIW to reduce the performance sensitivity to the PCB edge tolerance. Measurement shows the antenna features 3.9GHz bandwidth centered at 28GHz.

A Fully Integrated Ka-Band Front End for 5G Transceiver

We present the design and measured results of a fully integrated Ka-Band front end on a 0.15-μm GaAs pHEMT process. The integrated front end includes a three stage power amplifier, three stage low noise amplifier, and single pole, double throw switch. The integration of the front end is a crucial step to commercialize mm-Wave technology for 5G mobile communication. In addition to the fully integrated front end module, these three components were fabricated separately for individual characterization and analysis, and those results are presented in this paper.

Dipole array for mm-wave mobile applications

This paper provides details on the design, fabrication and measurement of a beam steerable co-linear dipole array for mobile applications at the 28GHz frequency band. The array is designed and fabricated on an industry standard circuit board stack-up, including the non-high performance substrate layers. The 4-element array measures 7.5dBi peak gain and has a 3dB coverage of 90° in elevation and 25° in azimuth.

MM-wave radio, a key enabler of 5G communication

In this paper, we evaluate a few millimeter-wave (mm-Wave) frequency bands as candidates for cellular mobile communication and demonstrate how selection of frequency band, size of base station (BS) phased array, coverage range, and number of simultaneous users that can be supported are tightly related. One of the major differences of 5G vs. legacy cellular generations is that the radio is operating at a significantly higher frequency; hence, we review the required technologies from integrated circuits to packaging and printed circuit boards (PCB) along with tradeoff among possible choices.

Mobile station radio frequency unit for 5G communications at 28GHz

This paper presents a millimeter wave mobile station radio frequency unit (MS RFU) operating at 28GHz with two receive (Rx) and two transmit (Tx) chains for MIMO or diversity where each chain utilizes beam steering to enhance signal to noise ratio (SNR). Each phased array employs 4 substrate integrated waveguide (SIW) antenna elements incorporated within the main printed circuit board (PCB). The RFU supports up to 800MHz signal BW and 64QAM OFDM signal with -27dB EVM.

A Ka-Band patch antenna array with improved circular polarization

In this paper, a Ka-Band patch sub-array structure for millimeter-wave phased array applications is demonstrated. The conventional corner truncated patch is modified to improve the impedance and CP bandwidth alignment. A new sub-array feed approach is introduced to reduce complexity of the feed line between elements and increase the radiation efficiency. A sub-array prototype is built and tested. Good agreement with the theoretical results is obtained.