Research On Broadband Millimeter Wave Receiver Front-End

During the past few years, global mobile data traffic and connected devices present the trend of explosive growth as the rise of mobile internet and Internet of Things (IoT). Looking ahead to the year 2020 and beyond, current mobile communication systems are unable to fulfil the requirement of ultra-high data rate and density, ultra-low latency, ultra-high mobility and massive device connections, therefore the research on 5G has become the focus of global communication field. The millimeter wave (MMW) technology and the massive multiple-input and multiple-output (MIMO) technology have obtained a lot of attention and several researches have been conducted on them for their advantage in increasing the capacity, transmission data rate, anti-interference ability and decreasing the latency.The research of this thesis is from National Science and Technology Major Project’s topic "The Research and Validation of Millimeter Wave Mobile Communication System’s Key Technology" and undertakes the design of the millimeter wave massive MIMO radio frequency (RF) system. The designed RF system operates at the 28GHz and is able to support 64 channels and 500MHz bandwidth with time division duplexing (TDD) mode. The RF system includes antenna array, millimeter wave front-end array, immediate frequency (IF) transceiver, local oscillator (LO) source module and digital processing board. The digital IF structure is employed in the receiver design and the center frequency of the IF is 2.75GHz.The major work of this thesis is to design the millimeter wave receiver front-end in the RF system. The performance indicators were determined under the overall requirements of the RF system’s performance, then the architecture of sub-harmonic mixing and external LO was used in the front-end. The front-end accomplishes the receiving of the RF signal, down-converts it to the IF and then pre-processes the IF signal by low noise amplifier, mixer, filter and IF amplifier and so on. The RF and IF passband of the front-end is 27-29GHz and 2.5-3GHz respectively.The front-end design was validated by link simulation, then major devices in the front-end were designed with evaluation measurement, and finally realized the front-end. The realized front-end obtains above 26.5dB receiving gain at 28GHz, while the gain flatness is below 0.8dB within 500MHz bandwidth. The measured noise figure is below 4.3dB, and the input ldB compression point and the third order intercept point are greater than-21dBm and -11.2dBm respectively. The image rejection ratio is kept above 45dBc and the reflect coefficients of all the front-end’s ports are below-lOdB at the same time. A receiving error-vector-magnitude (EVM) test was also performed on the front-end under both narrowband signals and broadband signals. The test results show that for signal with 50MHz bandwidth, the front-end achieves EVM below 3.4%,2.6%,2.3% and 2.1% respectively for QPSK, QAM 16, QAM64 and QAM256 modulation, and the value becomes 5.1% and 7% when the signal bandwidth is extended to 250MHz and 500MHz for QAM16 modulation. The overall measurement results show that the designed millimeter wave receiver front-end have excellent performance.