Replanting for sustainable development is one of the critical missions of the coffee industry in the Daklak province, Vietnam. However, this plan has been faced with many difficulties including poor survival and growth rates due to the low nematode tolerance of young coffee plants in replanted fields. Mycorrhizal symbiosis and grafting have been applied separately but not yet resulted in the expected results of the replanting plan. Whether the combination of them would help managing nematode in the soil and consequently enhance the replanted efficiency is largely unknown. Mycorrhizal symbiosis was applied to Coffea canephora plants or/and grafted onto Coffea liberica rootstock, which were grown and compared to the untreated ones in both net-house-pots and the replanted plantation. The survival rate, growth indicators and the soil pathogens were monitored during the experimental periods. The combination of grafting and mycorrhiza symbiotic techniques significantly decreased the nematode densities in the replanted soil. As a result, the survival rate and growth indicators of the coffee in the replanted soil treated by the combined technique were better than treated by the two separate techniques. The results suggested that the combination of grafting and mycorrhiza symbiotic techniques would propose a potentially effective Pratylenchus coffeae and Meloidogyne incognita nematode management in replanted coffee fields in the Daklak province, Vietnam.

In this paper, the author presents the design and implementation of an Sband transmitter for nanosatellites. By combining heterostructure field effect transistors (HFET) and laterally diffused metal–oxide–semiconductor (LDMOS) technology and using flexible structure and flexible control method, this research obtained 60 dB gain power when input is -14 dBm, output power is 46 dBm (more than 25 W) in 2,1 GHz -2,3 Ghz frequency; phase noise is -80 dBc/Hz at 100 KHz offset frequency. Unlike other traditional transmitters, this transmitter was designed with multi-stages which have multi-peaks resonance to expand bandwidth to respond to the requirement of generation of the complex signal in wide band. Moreover, the phase locked loop (PLL) in frequency synthesizer makes the frequency conversion more flexible and output frequency more stable; thermal problem in module also was solved by using thermistor and operation mode. Measurement results prove that the design does not only satisfy the requirements of nanosatellites but also can be applied to other satellites together with their ground station because it has open configure with flexible structure and flexible control method.

In the paper, the new microwave modules of NanoDragon satellite’s receiver were designed and fabricated. Purpose of this design is not only reduce budget but also respond to frequency requirement, bandwidth and transmission rate. The microwave modules consist of low noise amplifier (LNA), mixer and local oscillator (LO). These modules operate at S band according to requirement of satellite. Firstly, each module was designed, simulated, fabricated and measured. Then they were integrated together. Output of integrated microwave modules is IF signal with bandwidth is suitable for demodulation PCM – PM (BPSK). And have high gain value conform to receiver’s requirement. Simulation result of low noise amplifier is 19.108 dB at 2.9 GHZ. Simulation result of integrating two stage LNA become 2-stage LNA have gain value over 38 dB. Gain value obtained is 11.5 dB when measurement. Integrating microwave modules result is 10.5 dB with gain value. That mean this microwave modules of receiver operated very well. LNA was very good. This subsystem can apply for NanoDragon satellite’s receiver and receiver of ground station. Keywords: Receiver, Microwave Modules of Receiver, Satellite, NanoDragon satellite, LNA, Mixer, LO, IF.