Search

In this letter, a cross-coupled dual-bandpass filter (BPF) with separate electric and magnetic coupling paths (SEMCPs) for 5G sub-6 GHz applications is proposed. Source-to-load couplings are also introduced in this structure for the flexibility of heterogeneous feed lines. Five controllable transmission zeros (TZs) in total are produced in the dual-band filter. The filter achieves good overall performance by adopting two pairs of quarter-wavelength stepped-impedance resonators (SIRs). To minimize the size of the filter and enlarge the controllable range of the second passband, the SIRs forming the second passband are separated and folded onto two different layers. The measured dual band filter achieves fractional bandwidths of 7.82% and 4.08%, centered at frequencies of 3.45 and 4.9 GHz with insertion losses of 1.15 and 1.42 dB, respectively.

This paper introduces the design of a 24∼32 GHz variable gain amplifier (VGA) with a wide gain tuning range for millimeter-wave phased arrays. The VGA is based on a $0.13-\mu\mathrm{m}$ SiGe BiCMOS process and achieved digital gain control using current steering technique. The VGA gain tuning range is from - 16 to 20 dB, which consumes 24 mW with 1.6 V DC power supply. The output P 1dB is 6.7 dBm and NF is 4.7 dB at maximal gain state. The gain flatness is ±0.5 dB across 24∼32 GHz in all 256 states. The chip area is $0.6\times 0.3\text{mm}^{2}$ without testing pads.

In order to predict the livestock carrying capacity in meadow steppe, a method using back propagation neural network is proposed based on the meteorological data and the remote-sensing data of Normalised Difference Vegetation Index. In the proposed method, back propagation neural network was first utilised to build a behavioural model to forecast precipitation during the grass-growing season (June–July–August) from 1961 to 2015. Second, the relationship between precipitation and Normalised Difference Vegetation Index during the grass-growing season from 2000 to 2015 was modelled with the help of back propagation neural network. The prediction results demonstrate that the proposed back propagation neural network-based model is effective in the forecast of precipitation and Normalised Difference Vegetation Index. Thus, an accurate prediction of livestock carrying capacity is achieved based on the proposed back propagation neural network-based model. In short, this work can be used to improve the utilisation of grassland and prevent the occurrence of vegetation degradation by overgrazing in drought years for arid and semiarid grasslands.

Since 2002, ultra wideband (UWB) technology has ignited the interests of academia and industry for its potential of achieving high-speed wireless communication in short distance with low power. It is actively investigated today due to the wide available bandwidth for very high data rate up to 480Mb/s and low power service over short distances in 10m range. According to FCC (Federal Communications Commission), the frequency spectrum allocated for UWB is 3.1-10.6 GHz, and the spectrum shape of modulated output power and maximum power level are limited to -41.3dBm/MHz, which ensures that UWB can coexist with existing spectrum users like GSM(Global System of Mobile communication), WLAN(Wireless Local Area Network) and Bluetooth. Based on MB-OFDM(Multi-Band Orthogonal Frequency Division Multiplexing), WiMedia released the initial version of Physical Layer (PHY) Specification in September 2005. In this proposal, the UWB frequency spectrum from 3.1 GHz to 10.6 GHz is divided into 14 channels with 528MHz for each channel. These sub-bands are grouped into five band groups. It is seen that by increasing the signal bandwidth significantly, ultra-wideband achieves a high channel capacity and becomes an attractive solution to the ever-increasing data rate demands in wireless personal area networks (WPAN). In December 2005, European Computer Manufacturer's Association (ECMA) proposed the standard ECMA 368/369 on high-speed UWB physics layer and media access control layer based on MBOFDM scheme. This has pushed the industrialization of UWB technology to a new stage again. In China, UWB technology has also become a hot topic according to the issue of the UWB standard by Chinese Government in 2008. A new UWB scheme named dual carrierorthogonal frequency division multiplexing (DC-OFDM ) has been proposed and applied in China. In China standard, only the band from 6.2GHz to 9.4GHz and the band from 4.2GHz to 4.8GHz are available for UWB applications. These bands are partitioned into 14 subbands of 264MHz bandwidth which means the bandwidth is halved in China’s DC-OFDM standard compared with the ECMA 368/369 standard. Thus the sampling frequency of the DACs(Digital-to-Analog Converter) and ADCs(Analog-to-Digital Converter) are halved too. The power consumption of the system can be reduced greatly. Moreover, in DC-OFDM

This paper presents a low phase noise and low reference spur quadrature phase-locked loop (QPLL) circuit that is implemented as a part of a frequency synthesizer for China UWB standard systems. A glitch-suppressed charge pump (CP) is employed for reference spur reduction. By forcing the phase frequency detector and CP to operate in a linear region of its transfer function, the linearity of the QPLL is further improved. With the proposed series-quadrature voltage-controlled oscillator, the phase accuracy of the QPLL is guaranteed. The circuit is fabricated in the TSMC 0.13 μm CMOS process and operated at 1.2-V supply voltage. The QPLL measures a phase noise of −95 dBc/Hz at 100-kHz offset and a reference spur of −71 dBc. The fully-integrated QPLL dissipates a current of 13 mA.