Eisuke Haraguchi

Coherent homodyne receiver with a compensator of Doppler shifts for inter orbit optical communication

This paper presents Bread Board Model (BBM) of coherent homodyne receiver with an optical phase locked loop and a frequency compensator of Doppler shifts for inter satellite optical communication link. 2.5Gbps BPSK data has been demodulated with sensitivity of -49.1dBm at bit rate of 1e-6 under initial frequency offset of +/-7 GHz simulated as Doppler shifts due to variation of distance between each satellite.

Phase stabilized RF reference signal dissemination over optical fiber employing instantaneous frequency control by VCO

Stable microwave reference signal transfer systems are required in communication systems, very long baseline interferometer (VLBI) radio astronomy applications, particle accelerators and metrologies. Radio over fiber (RoF) technique is one of candidates which realize precise microwave dissemination without degradation of stability. We developed the precision microwave signal dissemination system in which a fluctuation of phase caused by transmitting optical fiber thermal expansion. This system monitors a phase of the signal reflected at destination, and controls transmitting signal frequency using a voltage controlled oscillator (VCO). The measurement shows that the phase error is 0.098 deg (r.m.s) of the 1.0 GHz microwave signal in 1-km length single mode fiber over 10 hours.

Homodyne BPSK receiver with Doppler shift compensation for inter satellite optical communication

This paper presents Bread Board Model (BBM) of homodyne BPSK (Binary Phase Shift Keying) receiver with an optical phase locked loop and a Doppler shifts compensator for inter satellite optical communication link. 2.5Gbps BPSK data has been demodulated with sensitivity of −49.1dBm at bit error rate of 1e-6 under initial frequency offset of +/−7.5 GHz simulated as Doppler shifts due to relative motion of each satellite.

Spatial light modulator based optically controlled beamformer for variable multiple-spot beam antenna

We propose and demonstrate an optically controlled multiple-beam phased array antenna employing spatial light modulator. Developed prototype of the optical beamformer enables control multiple-beam direction and width; we demonstrated beamforming operation at 18 GHz. Furthermore, we have performed the communication test such as the bit error ratio (BER) test, data rate of 622 Mbps and 1244 Mbps in the digital communication link. We have confirmed that this optical beamformer had no serious effect for BER performance.

Evaluation of developing inertial stabilization unit

Micro vibrations generated from some internal disturbance sources such as a reaction wheel degrades the pointing stability of an observation satellite. To suppress the pointing error, we have been developing an inertial stabilization unit. A prototype mechanism is designed based on concepts that it has non-contact actuators and sensors, and rotational leaf springs are applied to support a stabilized platform in order to meet two requirements which are precise drive and tolerance for launch load. Two kind of inertial sensors are installed on the platform to measure the attitude directly. Each of these two inertial sensors covers low or high bandwidth signal respectively. These signals will be able to be combined as one wideband signal to stabilize the platform in inertial space. In this paper, the developing prototype mechanism and control equipment are described and the basic evaluation results are reported. Less than 0.3urad as a drive precision and more than 100Hz as a local sensor control bandwidth are verified. The development of the system has not completely finished yet, but the basic performance is certified to meet the design specification. From now on, we continue to develop the unit. These future results can be applied to inter-satellite laser communication system.