ÿþ<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" > <html> <head> <title>Institute for ElectroMagnetic Research / Our Products / Beamless Pulsed Microwave Generators </title> <meta http-equiv="Content-Type" content="text/html; charset=Windows-1252"> <meta name= "Description" content="Powerful microwave oscillators"> <meta name="Keywords" content="IEMR - Microwave Oscillators, MILO, MCG"> <link rel="stylesheet" href="style/institute.css" type="text/css"> </head> <body> <table width="90%"> <tr><td> <h3><a href="home_page.htm" >Home Page</a> > <a href="our_prod.htm" >Our Products</a> > Beamless Pulsed Microwave Generators</h3> <hr> <h3 align="center">Beamless Microwave Generator MHWG-1</h3> <p>Nowadays, beamless pulsed microwave generators are in a relatively wide use which, seemingly, can be attributed to their large breadth of emission spectrum, rugged structure and relatively low production costs. </p> <p>However, since in those devices the broad emission spectrum is provided owing to excitation of the electrodynamic structures, or immediately antennas, by a small-width pulse (0.1-1 ns), then despite a high level of radiated pulsed power ~ 109 W, the radiation energy is low, not exceeding usually several joules. It is exactly this fact that imposes certain limitations on usage of those devices. </p> <p>IEMR, Ltd. has developed several kinds of the beamless generators, namely those that employ excitation of the electrodynamic structures by high-pressure discharges and those based on excitation of the non-linear circuits that have lumped constants by powerful current pulses with a high steepness of the leading edge.</p> <p>These devices are rugged structurally, enabling to produce high-peak power output levels at a relatively large breadth of the spectrum and a high stability of the shape of radiation pulse generated.</p> <p>As an example of one type of our proprietary beamless generators, we shall give a brief description of a device enabling to produce single pulses or bursts of pulses generated. Its operation is based on the use of an H-type waveguide driven by large-current high-pressure gas-filled spark gaps. </p> <table border="0" align="center" width="80%"> <tr align="center"> <td>&nbsp;</td> <td><a href="./Figures/bl_gen_01.jpg"><img src="./Figures/sbl_gen_01.jpg" width="400" height="325" border="0"/></a></td> <td>&nbsp;</td></tr> <tr><td>&nbsp;</td><td align="center">Fig. 1. General view of generator employing H-waveguide on experimental stand. 1  H-waveguide with driver spark gap; 2  Radiating horn; 3  Anechoic chamber; 4  Chamber-to-horn junction; 5  HV delay line; 6  Low-inductance storage capacitance; 7  HV pulsed power supply. </td><td>&nbsp;</td></tr> </table> <p>This generator is viewed as an H-type waveguide (1) filled with refined transformer, or silicone, oil in order to prevent breakdowns during operation at high-power levels. The waveguide is driven by one or two (with a certain delay) gas-filled high-pressure spark gaps upon triggering them off with an HV-pulse with an amplitude up to 400 kV that comes from the high-voltage low-inductance storage capacitance (6). The spark gaps which are filled up with SF<SUP>6</SUP> , or a mixture of SF<SUP>6</SUP> with N<SUP>2</SUP> , can be set off either one-by-one, or with a certain delay relative to each other, as introduced by the high-voltage delay line (5). An adjustable high-voltage supply of the transformer type allowing to produce pulses with an amplitude up to 420 kV is used as charging source for the low-inductance capacitance. The use of this high-voltage transformer makes for a very compact voltage source. </p> <p>Fig. 2 gives an oscillogram of radiated pulse from this generator in the mode of operation of driving the H-waveguide by two spark gaps in that event when the actuation time of one is delayed in relation to the other. </p> <table border="0" align="center" width="80%"> <tr align="center"> <td>&nbsp;</td> <td><a href="./Figures/bl_gen_02.jpg"><img src="./Figures/sbl_gen_02.jpg" width="400" height="325" border="0"/></a></td> <td>&nbsp;</td></tr> <tr><td>&nbsp;</td><td align="center">Fig. 2. Oscillogram of radiated pulse in the mode of generation of a burst of pulses driven by two spark gaps with delay. </td><td>&nbsp;</td></tr> </table> <p>Fig. 3 presents an oscillogram of emission from the generator upon driving the H-waveguide with one spark gap. In this case, single pulses are produced.</p> <table border="0" align="center" width="80%"> <tr align="center"> <td>&nbsp;</td> <td><a href="./Figures/bl_gen_03.jpg"><img src="./Figures/sbl_gen_03.jpg" width="400" height="325" border="0"/></a></td> <td>&nbsp;</td></tr> <tr><td>&nbsp;</td><td align="center">Fig. 3. Oscillogram of emission from generator in the mode of production of single pulses of radiation. </td><td>&nbsp;</td></tr> </table> <p>As one can see from the above oscillograms, during simultaneous actuation of two spark gaps a burst of pulses with long widths is generated, the radiated power being, however, considerably lower, as compared with the case of one spark gap excitation when a single pulse is radiated. This phenomenon is accounted for by a low value of energy stored in the storage capacitance (6). </p> <p>The main performances of our proprietary beamless generator are given in Table 1. </p> <h3 align="center">Table 1. </h3> <table border="1" align="center"> <title>Table 1. </title> <tr><td>&nbsp;1.&nbsp;</td> <td>&nbsp;Signal emission frequency band&nbsp;</td> <td>&nbsp;350 750 MHz&nbsp;</td></tr> <tr><td>&nbsp;2.&nbsp;</td> <td>&nbsp;Peak signal power value&nbsp;</td> <td>&nbsp;Not less than 500 MW&nbsp;</td></tr> <tr><td>&nbsp;3.&nbsp;</td> <td>&nbsp;Total radiated energy in one burst&nbsp; </td> <td>&nbsp;Not less than 2 J&nbsp;</td></tr> <tr><td>&nbsp;4.&nbsp;</td> <td>&nbsp;Repetition period of radiated bursts&nbsp;</td> <td>&nbsp;Not less than 1 min.&nbsp;</td></tr> <tr><td>&nbsp;5.&nbsp;</td> <td>&nbsp;Total generator weight&nbsp;</td> <td>&nbsp;Not more than 260 kg&nbsp;</td></tr> </table> <p>This option of the generator also includes an antenna mirror that allows to control the beam position.</p> <p>Our proprietary generator of single pulses and bursts of broadband pulses can be used in diverse studies on electromagnetic compatibility.</p> <h3 align="center">Coaxial Beamless Pulsed Microwave Generator MG-1</h3> <p>High-power pulsed beamless microwave generator MG-1 is designed for electromagnetic compatibility (EMC) studies in the laboratory and field conditions. Generator uses electrodynamic structure, excited by the high current and voltage pulses. The electrodynamic structure is loaded on the phased logperiodic antenna array (PA). Conical vibrators are utilized to ensure effective operation of the logperiodic antenna array in the broad frequency band and high power levels.</p> <p>General view of beamless MG-1 generator, connected to the matched load and driven by the MCG simulator is shown in Figure 1.</p> <table border="0" align="center" width="80%"> <tr align="center"> <td>&nbsp;</td> <td><a href="./Figures/bl_MG_01.jpg"><img src="./Figures/bl_MG_01.jpg" width="400" height="325" border="0"/></a></td> <td>&nbsp;</td></tr> <tr><td>&nbsp;</td><td align="center">Fig. 1. General view of beamless generator powered by the MCG simulator and connected to the matched load. 1  matched load; 2  coaxial generator; 3  transition unit; 4  gas-filled electroexplosive opening switch; 5  current sensors; 6  voltage sensors; 7  switching spark-gap unit; 8  capacitor storage; 9  control unit. </td><td>&nbsp;</td></tr> </table> <p>Coaxial beamless generator MG-1 can be powered by both MCG simulator and capacitor storage.</p> <p>General view of MG-1 generator with the connected low-inductance capacitor storage is shown in Figure 2.</p> <table border="0" align="center" width="80%"> <tr align="center"> <td>&nbsp;</td> <td><a href="./Figures/bl_MG_02.jpg"><img src="./Figures/bl_MG_02.jpg" width="325" height="400" border="0"/></a></td> <td>&nbsp;</td></tr> <tr><td>&nbsp;</td><td align="center">Fig. 2. General view of beamless coaxial generator MG1 with connected capacitor storage; 1  elements of logperiodic phased antenna array; 2  output antenna isolator; 3  phased array conical vibrators; 4  coaxial generator; 5  capacitor storage. </td><td>&nbsp;</td></tr> </table> <p>The oscillogram of radiation emission from MG-1 generator picked up 15 m away from its antenna is shown in Figure 3.</p> <table border="0" align="center" width="80%"> <tr align="center"> <td>&nbsp;</td> <td><a href="./Figures/bl_MG_03.jpg"><img src="./Figures/bl_MG_03.jpg" width="400" height="325" border="0"/></a></td> <td>&nbsp;</td></tr> <tr><td>&nbsp;</td><td align="center">Fig. 3. </td><td>&nbsp;</td></tr> </table> <p>The main parameters of the generator are given in the Table below.</p> <h3 align="center">Table 1. </h3> <table border="1" align="center"> <title>Table 1. </title> <tr><td>&nbsp;1.&nbsp;</td> <td>&nbsp;Bandwidth of generator&nbsp;</td> <td>&nbsp;150 500 MHz&nbsp;</td></tr> <tr><td>&nbsp;2.&nbsp;</td> <td>&nbsp;Radiation pulse width&nbsp;</td> <td>&nbsp;15 ns&nbsp;</td></tr> <tr><td>&nbsp;3.&nbsp;</td> <td>&nbsp;Field strength produced by generator-emitted radiation at 50 m distance&nbsp; </td> <td>&nbsp;Up to 5 kV/m&nbsp;</td></tr> <tr><td>&nbsp;4.&nbsp;</td> <td>&nbsp;Repetition period of radiated bursts&nbsp;</td> <td>&nbsp;Not less 1 min.&nbsp;</td></tr> <tr><td>&nbsp;5.&nbsp;</td> <td>&nbsp;The maximum dimensions of the generator:<br> &nbsp;&nbsp;Diameter <br> &nbsp;&nbsp;Length </td> <td>&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;150 mm<br>&nbsp;&nbsp;&nbsp;&nbsp;370 mm</td></tr> <tr><td>&nbsp;6.&nbsp;</td> <td>&nbsp;Maximum size of generator with antenna&nbsp;</td> <td>&nbsp;630x630x500 mm&nbsp;</td></tr> </table> <p>MG-1 generator is used as a radiation source for electromagnetic compatibility studies. </p> </td></tr></table> <table border="0" align="left" width="90%" > <tr><td> <hr> </td></tr> <tr><td align="center"> <a href="information.htm" target="mainFrame" >Information about IEMR</a> &nbsp; <a href="departments.htm" target="mainFrame" >Departments</a> &nbsp; <a href="our_prod.htm" target="mainFrame" > Products</a> &nbsp; <a href="our_res.htm" target="mainFrame" > Research Projects </a> </td></tr> <tr><td align="center"> <a href="http://www.emph.com.ua" target="_blank" >Electromagnetic Phenomena Journal</a> &nbsp; <a href="Address.htm" target="mainFrame" >Contact us </a> </td></tr> </table> </body> </html>