Design and validation of an adaptive Cubesat transmitter system using a Thermal Vacuum Chamber (TVAC)

CubeSat in a low earth orbit primarily uses a UHF transmitter with a fixed RF output power. In this paper, the design of the CubeSat transmitter with adaptive power controlability is presented. The design drive is to optimise the SNR and overcome the variability of the propagation path length due to different ground station elevation angles by adjusting its transmitting power. The TVAC test is conducted to validate the performance of the adaptive function in the transmitter. The TVAC is used to emulate the satellite condition in an outer space environment. Four thermal cycles starting from +60°C to -20°C with less than 10-5Pa pressure condition are employed, which was conducted at the KIT CeNT, Japan. The transmitter was integrated inside the satellite structure as a complete CubeSat system. The output power of the transmitter is tested from 0.5W to 2W based on the proposed satellite adaptive mode. The frequency stability of the transmitter is monitored and complies with an average of 70% below requirement, which is less than 2ppm. The results indicate that the RF output power is adjustable to operate as the proposed CubeSat adaptive transmitter in a thermal vacuum condition, which was first developed in Malaysia

FPGA implementation of multi frequency continuous phase frequency shift keying (MCPFSK) modulation techniques for HF data communication

In HF (High Frequency) data communication systems [1,2], FSK (Frequency Shift Keying) digital modulation is widely used. The simplicity in the implementation is the main reason for its popularity. Since noncoherent detection is possible, additional components such as timing recovery circuits [3] are not necessary as required in PSK (Phase Shift Keying) modulation

FPGA implementation of CPFSK modulation techniques for HF data communication

Digital modulation based on FSK is widely used in HF data communication. This is due to simplicity in implementation by noncoherent detection and robustness due noise and phase synchronization error.Hardware based design using FF'GA can reduced system size. The proposed modulation integrates holh the transmitter and receiver modules into a single FPGA. Further reduction in components is achieved hy adopting a multiplierless and parallel algorithm at the receiver module. This is proven by comparing with conventional noncoherent detection algorithm

Detection of binary data for FSK digital modulation signals using spectrum estimation techniques

FSK is widely used for the transmission of data over passband channels due to the simplicity of implementation using noncoherent detection schemes. Better BER performance can achieved with accurate phase synchronization using coherent detection scheme. By using the fast Fourier transform (FlT), it is possible to implement spectrum based detection : complex sinusoid and complex square wave. The BER performance is slightly lower than coherent detection. Unlike coherent detection, phase synchronization is not critical for the spectrum based detection. Further simplification in hardware implementation is achievable using spectrum based detectioncomplex square wave since the use of multipliers is not required

Design of an adaptive CubeSat transmitter for achieving optimum Signal to Noise (SNR)

CubeSat technology has open opportunity to conduct a space related research at a relatively low cost. To maintain CubeSat mission at an affordable cost, CubeSat typically uses a simple communication system using UHF link with fixed transmit power and data rate. However, CubeSat in Low Earth Orbit (LEO) does not have a relative motion with the earth rotation, resulting in a variable of the propagation path of the transmission signal. A transmitter with the adaptive capability to select multiple sets of data rate and RF transmit power are proposed to the improve the link optimization problem due to the variability of the propagation path. This paper presents the adaptive UHF transmitter design as a solution to overcome the variable of the propagation path. The transmitter output power will be adjustable from 0.5W to 2W according to the mode of operations and satellite power limitations. The transmitter is designed to have four selectable modes of operation to achieve optimum SNR and efficient power consumption based on link budget analysis and CONOPS requirement. Three prototypes were developed and tested for space-environment conditions such as radiation, vibration, and thermal vacuum test. Further detail about radiation test conducted at the Malaysia Nuclear Agency Laboratory is explained in this paper with the successful result for estimated more than seven months in the orbit exposure. Based on author knowledge, this radiation test using gamma source with 1.5krad exposure was the first conducted for satellite programmed in Malaysia