| To insure the overawing force and the actual combat force, the navy of every country in the world is developing the naval surface war-ships studiedly. At the same time, they also focus on the development of the new generation weapon under water, such as anechoic submarine. We can anticipate that in 21centery, the flexible anechoic submarine, which is shockproof and has strong attack and defence capability will become the main force of the sea fight.Cladding tiles to submarine hull is the major way to achieve anechoicness. At the present time, the most difficult problem in manufacturing anechoic submarine is the technique of cladding tile. If there are any disbonding defects under anechoic tiles (lack of glue, gap or air bubble), it will depress the anechoic performance and fastness of the tiles. If the shipboard is eroded or the tiles shell, the navigate capability and anechoic performance of the submarine will be affected. So the only way to protect the submarine from all these problems is to inspect the adhesive defects under anechoic tiles and take actions to repair it.Meeting the demand of engineering application, we successfully developed the microwave nondestructive inspector CPY-1 in 1997. It is the first time that a nondestructive tester can be used to inspect the disbonding defects under anechoic tiles all over the submarine at real time. The test error was lower than 10%.This topics in this paper are formed form some important problems or strange phenomena, arose during the process of developing the microwave nondestructive inspector CPY-1 and engineering inspection. The author took part in the development of the improved microwave nondestructive inspector CPY-1G and engineering inspection. This paper also studied on some problems theoretically, such as the sensitive operating point of the instrument, the reflection coefficient can be greater than unity, and so on.The main contributions of the paper is as follows:K As an important member in the research group, the author took part in the project of developing and adjusting the improved microwave nondestructive inspector CPY-1G and in the field test as well. This CPY-1G instrument is more safe, more accurate and more reliable than the CPY-1 instrument.2 For the first time, the author brings forward the concept of "Pyramid horn high order mode resonator" and PML-FDTD technique is used to analyze the electromagnetic field distribution in the pyramid horn. The results show that the pyramid horn sensor is much more sensitive than the open ended waveguide or transmission line sensors. The sensor we used is a kind of resonance sensor. The difference of anechoic tile sample is in fact a perturbation inside the pyramid horn resonator. If an open ended waveguide or coaxial line sensor is used, it is just a little change at the terminal load for different samples. Anyway, the pyramid horn sensor can be a resonance sensor, which operates with high order mode. This provides physical explanation for the puzzle of sensitive operating point of the CPY-1.3 To choose proper reference sample, a genetic algorithm program is developed to optimize the reference sample parameter. At the same time, the validity of the result is verified by an analytic method. This provides the foundation of making optimized reference sample for CPY-1 G. As a result of it, the test accuracy raise to 95%.4 For the first time, the author brings forward the conclusion: "In passive media, reflection coefficient can be greater than unity". Under some conditions, although for passive materials, when a plan wave incidents to the interface between a layered lossless material and a layered lossy material, the reflection coefficient of electric field may be greater than unity. The strict theoretical analysis is given.5 It is proved that the reflection coefficient of electric field for lossy transmission line can be greater than unity. The conditions for this phenomenon to occur are also given.
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