Synchronizer for Meter Range Distributed Radar Prototype
Radiooptics # 06, November 2015
One of the problems of a spatially coherent distributed radar is to form a single timescale of the system for cooperative echo signals processing received by different modules, and synchronize operation of spaced modules. This paper considers a method to design a synchronizer that allows us to solve these problems.
Modules cannot be clocked from common reference oscillator (RO) due to spacing therefore there is a separate RO in each module. Inexpensive commercially available quartz oscillators with long-term frequency instability of the order of 10-5…10-6 may be used as reference oscillators for surveillance meter range radar. To simplify the hardware reference oscillators operate in the free vibration mode. Thus several independent time scales are formed in the system. These time scales will be collated using special synchronization signals during system operation and their differences will be assessed.
A problem of synchronous control of module devices arises for distributed system. It is expected that device settings may be quickly changed during system operation. This requires the simultaneously transmitting control commands for configuration devices (sub-modules) from the central processing station using synchronization channel. To reduce requirement for communication there is a separate synchronizer in each module. Algorithms of synchronization signals and control commands output are loaded in these synchronizers beforehand. Central processing station sends only small pieces of data during system operation. These data fragments used for rapid device configuration according to previously loaded program. Synchronous operation of the system is achieved by the simultaneous launch of synchronizers and keeping strict between the signals.
Synchronization system described in the article successfully is implemented in spatially coherent distributed radar prototype, developed by BMSTU NIIRET. Experimentation showed that designed equipment enables to achieve potential synchronization accuracy equal to 5…8 ns using communication channel bandwidth of 1MHz and quartz oscillators long-term frequency instability of the order of 10-5. Achieved accuracy is enough for operation of surveillance meter range spatially coherent distributed radar. Scientific innovation is the proposed cycle synchronization method, which consists in software-algorithmic comparison of distributed radar time scales. The new synchronization principle allowed to use relatively simple technical solutions for distributed radar prototyping.
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