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The method is considered which consists of measurements of output antenna signals on a number of frequencies and Fourier transformation of data into time domain for separation of own antenna field and interference fields. The results of testing at serial facility for antenna measurements in an anechoic chamber are presented as for diagnosis of scattered fields, as for improvement of accuracy of antenna characteristics evaluation. [ABSTRACT FROM PUBLISHER]

A report on an investigation of spherical, disc, and half-disc antennas in the frequency and time domains with the objective of developing small planar versions of the antennas. These antennas have an omni-directional impulse response in azimuth and pulse duration of 0.5-0.65 nanoseconds. In addition, the measured data show a reasonable peak received signal in a pulse communication link using two identical antennas. [ABSTRACT FROM PUBLISHER]

Differential GPS on board naval vessels has been tested in severe multipath archipelago environment against a commercial laser tracker system. The average location difference was 3 meters and two periodic error components were found. Their tune constants were 1.8 and 28 seconds and the peak amplitudes 1.5 and 1.1 meters, respectively. In addition to these, a clear dependency of location error standard deviation figures on the GPS antenna mounting distance from the sea level was observed. [ABSTRACT FROM PUBLISHER]

Testing of satellite antennas at high millimeter and submillimeter wavelengths has some specific problems not encountered at lower frequencies. The atmospheric attenuation due to water and oxygen molecule resonances at certain frequency bands can be substantial. Therefore, conventional far-field test methods for electrically large antennas are ruled out by the required far-field distance of kilometers or even tens of kilometers. However, the compact antenna test range (CATR) makes such far-field tests possible within an indoor chamber having a controlled atmosphere. The application and ongoing development of a CATR based on a hologram as the focusing element are outlined [ABSTRACT FROM PUBLISHER]

In this work, the influence of resistive absorbers in the vicinity of small antennas was investigated, in order to define a lower limit for the size of a small anechoic chamber for antenna calibration and radiation pattern measurements, with respect to the distance between the antenna under test (AUT) and the RF absorbers lining the walls. Furthermore, the influence of a relatively narrow transmission channel, formed by the absorbers on the side walls between the measurement antenna and the AUT was investigated. It was found by measurements that absorbers with the length of 610 mm do not have a measurable effect on the radiation characteristics of a small antenna at around 1.8 GHz, as long as they are kept more than 100 mm from the AUT, and the transmission channel formed by the absorbers between the antennas is wider than 100 mm [ABSTRACT FROM PUBLISHER]

Reliable impedance measurements of installed HF air navigation antennas are possible with an automatically adjusted high power analyzer using levels above 30 dBm to overcome external interference signals coupled from the environment. Even a bad mismatch of an unknown device cannot cause unpredictable results or test equipment failures if this straightforward method is applied. The proposed adaptive network analyzer covers frequencies between 100 kHz-50 MHz and regulates the test port power down to 10 dBm according to the return loss and, thus, reduces the risk of damage and, at the same time, improves resolution at the other end of the return loss scale above 25 dB. The rejection of the misleading effects of unwanted signals can be further improved by the built-in modulation [ABSTRACT FROM PUBLISHER]

If modern airborne radar systems are to function properly, the radar antenna radiation patterns must meet certain specifications. Until recently, most radar antennas were designed and tested in a clean antenna environment, i.e., there is no near field scattering from host structures or radome effects. However, these higher order effects are the matter of increasing concern with added performance demands in the ever-increasing jammer and clutter interference environments. We investigated the capabilities and limitations of currently available analysis techniques and computer codes for installed performance of airborne radar antenna systems. Then we developed an extended ray-optical technique that could predict total installed performance of airborne radar antenna systems, i.e., the near field scattering from aircraft structures and radome effects. The new analysis technique utilized a ray-tracing method in both airframe and radome simulation. Thus, it can efficiently predict the total installed performance of large radar antenna systems on an aircraft structure [ABSTRACT FROM PUBLISHER]