Manabu Akita

Development of millimeter wave radar using stepped multiple frequency Complementary Phase Code and concept of MIMO configuration

Stepped multiple frequency Complementary Phase Code (CPC) modulation proposed by authors is a unique radar modulation/demodulation method that can achieve an extremely low range sidelobe by the short code length, a high range resolution equivalent to the transmission bandwidth by a narrower band receiver, and a long range detection performance. Authors also have developed 60GHz millimeter wave radar employing this modulation. In this paper, the experimental results using the radar system are at first presented to verify the radar performance described above. Then the concept of expansion to Multi Input Multi Output (MIMO) of stepped multiple frequency CPC is also described. The initial simulation results indicated the possibility that MIMO stepped multiple frequency CPC enable us to obtain not only a high range-velocity resolution but also a high angular resolution while preventing the deterioration of the characteristics in Doppler direction.

Nonlinear effects for sidelobe characteristics of pulse radars

Nonlinear effects on correlation sidelobes of receiver signals for pulse radars, which were UWB pulse radar, pulse compression radar and mainly phase coded high pulse repetition frequency (PCHPRF) radar were discussed. Sidelobes of pulse radars increases in the case of nonlinear system with some other radio frequency (RF) parameters. We investigated on the parameters verified decision parameters for these sidelobe characteristics by using RF simulation method considering nonlinear effects.

Experimental Comparison of stepped multiple frequency CPC with Pulse compression

Authors have developed the stepped multiple frequency Complementary Phase Code (CPC) radar system. The unique radar modulation/demodulation method can achieve both a high range resolution and a long-range detection performance with a narrow band receiver compared with the transmission bandwidth. In this paper, the experimental verification to compare the detection range performances between Stepped multiple frequency CPC and Pulse compression was conducted. The experimental results indicated that the proposed modulation was 1.72 times superior to Pulse compression in the detection range performance on the condition where the transmission bandwidth, observation time, peak power, code length (the number of chips of switching codes), and the number of total pulses were set to be the same.

Data processing procedure using distribution of slopes of phase differences for broadband VHF interferometer: New Data Processing for Continuous DITF

The upgraded VHF digital interferometer (VHF DITF) system is introduced which can continuously sample the radiation associated with lightning. A new processing technique was implemented which uses the distribution of slopes of the phase difference versus frequency to locate the radiation source. By using this technique, frequency components which are not due to lightning can be excluded and low as well as high amplitude sources are located. As a result, both positive breakdown and negative breakdown are located, and negative recoil leaders (recoil leaders) are visualized in great detail. The recoil leaders which continue into the positive charge region are seen to slow their propagation and dim their radiation as they cross the flash initiation region. Analysis of the relative received power of the different breakdown types, negative leaders, recoil leaders, and positive leaders, also can be made. In both the intracloud and cloud-to-ground flash, the modes of the distributions of received power for negative leaders, recoil leaders, and positive leaders were approximately the same. The brightest emissions seen from the positive leader were substantially lower than the brightest emission seen from the negative leader. The results also indicate that positive leaders as well as lower elevation negative leader emit more low frequency radiation than recoil leaders and high-elevation negative leaders. By continuously sampling the VHF waveform, the upgraded VHF DITF locates many weak sources which the previous system was not capable of locating.