Comparative evaluation of nonlinear location devices.

Comparative evaluation of nonlinear location devices.

Comparative evaluation of nonlinear location devices.

The attached table provides the main technical characteristics of nonlinear locators (IL) of foreign and domestic production, presented on the Russian market.

The most significant classification feature, in our opinion, is the power of the emitted probing signal. From the table it is clear that all ILs can be divided into two large groups:

• «powerful», as a rule, pulsed ILs with an output power of > 100 W;
• «low-power», as a rule, continuous ILs with an output power of ~ 1 W

In turn, the NL of both groups are divided into single-frequency and dual-frequency. The latter provide the ability to comparatively analyze the 2nd and 3rd harmonics of the probing signal, which significantly expands the operator's capabilities in terms of identifying electronic search objects against the background of corrosion nonlinearities.

As follows from Table 1, the power of pulse locators' transmitters is 1000 times higher than that of continuous ones. In turn, the sensitivity of continuous locators' receivers is 1000 times better than that of pulse NL receivers.

Taking into account the specified proportions from the relationships of short-range nonlinear location, it follows that, all other things being equal, in particular identical directional properties of antenna systems, the signal/noise ratio at the input of the receiver of a pulse locator is approximately 3 orders of magnitude higher than that of a continuous locator. The latter determines a practically 3-fold excess of the detection range provided by a pulse locator in comparison with a continuous locator.

The calculated ratio of detection ranges coincides with the results of comparative tests of the NR900 locator (Pper = 150 W, Po = -115 dBW) with continuous locators «Ob» (Pper = 250 mW, Po = -145 dBW), «Rodnik» (Pper = 800 mW, Po = -150 dBW) and BROOM (Pper = 80 mW, Po = -140 dBW), conducted on a sufficiently representative (more than 20 units) set of detection objects. Thus, the above-mentioned continuous locators showed a detection range 3-10 times smaller than NR900. Moreover, about 40% of the detected objects were not detected by the «Ob» locator, as well as the low-power pulse locator «Lux» (Pper = 14 W, Po = -130 dBW).

In conclusion of the calculated and experimental comparative assessments, we will make a number of comments regarding the NL antenna systems. As a rule, the consumer compares different types of NL based on the transmitter power, although in fact, the power flux density at the location of the desired object is significant, proportional to the product of the transmitter power and the gain of the transmitting antenna. An effective highly directional antenna not only increases the energy of the probing signal, but also allows for better spatial selection in the interior conditions of the room being surveyed. It is also important that the NL antenna has circular polarization.

Thus, the scope of application of low-power, both continuous and pulsed NL is limited to searching in the surface layer of building

structures, as well as in the simplest interior elements. It should be noted that low-power NLs are capable of guaranteeing detection of only the simplest search objects that are not equipped with serious shielding and special filters that reduce the nonlinear effective scattering surface of the sought object.

In turn, powerful pulse locators are practically devoid of the above-mentioned shortcomings and, as a result, provide much greater productivity and efficiency of search activities — they practically do not require a two-sided examination of massive interior elements, mandatory opening of suspended ceilings, and also provide a confident search in the thickness of building structures.

In terms of possible concerns about the impact of a powerful NL probing signal on the operator, two aspects should be noted using the example of the NR-900 series locators:

— with a pulse power of 150 W and a duty cycle of 1000, the average power is only 150 mW;

— the level of the rear lobes of the antenna system is minus 20 dB. This ensures compliance with the energy load standards for the operator in accordance with GOST 12.1.006-84 during continuous operation for 8 hours a day.

The issues of electromagnetic compatibility of powerful locators have been positively resolved in the latest modification of the NR900 series locators (NR-900E) due to the highly efficient antenna system with a narrow directional pattern (60 at half power), as well as due to the introduction of a listening mode that ensures control of the range load before turning on the transmitter.

Conclusions

1. Foreign nonlinear locators presented on the Russian market, at a significantly higher cost (2-3 times), are significantly inferior to the most advanced domestic developments in terms of ensuring high search performance, reliable detection of «embedded» devices with a small effective scattering surface.

2. Among domestic locators, the locator of the IV generation of the NR900 series — NR900E should be especially highlighted, combining high energy potential, the possibility of the most complete analysis of response signals by the operator (11.111 harmonics, envelope mode — 20K), high ergonomic indicators.

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