This invention relates to Ultra- Wideband (UWB) sharpeners for providing excitation to a symmetric antenna. Background art

In publication of "Anfu Zhu, Fu Sheng, Anxue Zhang, An Implementation of Step Recovery Diode-Based UWB Pulse Generator. Proceedings of 2010 IEEE International Conference on Ultra-Wideband (ICUWB2010) " is described a design of Ultra- Wideband pulse generator comprising pulse shaper with a shapener. Said UWB sharpener for excitation a symmetric antenna comprises an avalanche transistor. A base of avalanche transistor is connected to an input of impulses. A collector and an emitter of the avalanche transistor both are connected to its timing resistor and forming capacitor. UWB pulse generator further comprises a step recovery diode which through its anode is connected to a first resistor, coupled to a positive pump source, and through its cathode is connected to the capacitor and to a second resistor, coupled to a negative pump source. A symmetric antenna consisting of two identical parts, wherein one part is connected to the anode of the step recovery diode via a capacitor and other part is connected to the cathode of the step recovery diode via a capacitor. When using antenna, given circuit does not allow matching optimally the output impendence of the generator to the input impendence of the antenna and independent adjustment of the amplitude of the output pulses.

Known pulse shaping circuit to power an antenna are described in US Patent No. 7812760, US Patent application No. US 201 1/0013673 and US Patent application No. US 2003/0043078. Said circuits comprise an avalanche transistor as the input pulse sharpener and transformers as dividers for two paraphase pulses, containing paraphase amplifier output load, which as itself is a symmetric antenna. The disadvantages of such devices are the restrictions placed on the front of the output pulses, the presence of only one stage of exacerbation, the difficulty of matching the input impedance of a symmetric antenna. The aim of the invention is to increase the efficiency of transmission for UWB symmetric antenna specifically by improving a control of amplitude of pulses and by providing an exact match between an output impedance of a sharpener and an input impedance of an antenna.

Summary of the invention

Said aim is achieved by design of UWB sharpener for excitation a symmetric antenna, wherein sharpener's main elements are an avalanche transistor, a step recovery diode and a symmetric antenna. An avalanche transistor via its base is connected to an source of pulses, via its collector is connected to a timing resistor, which is coupled to a source of high voltage, and a forming or shaping capacitor, and via its emitter is connected to an emitter resistor, coupled to a ground, and a positive pulse control capacitor.

A step recovery diode via its anode is connected to a first resistor pumping current, which is coupled to a positive pump source, and via its cathode is connected to the positive pulse control capacitor and to a second resistor pumping current, which is coupled to a negative pump source.

A symmetric antenna consists of two identical parts, wherein a first part is connected to the anode of the step recovery diode and a second part is connected to the cathode of the step recovery diode. The UWB sharpener further comprises a base resistor, a load resistor, a control capacitor and matching resistors.

A base resistor is connected to the base of the avalanche transistor and to the emitter of the avalanche transistor.

A load resistor and a negative pulse control capacitor are both connected to the forming or shaping capacitor, and other end of the negative pulse control capacitor is connected to the anode of the step recovery diode, and the other end of the load resistor is connected to a ground. Such a circuit provides improved control of amplitude of the pulses. The sharpener further comprises a first matching resistor is connected to the anode of the step recovery diode and to the first part of the symmetric antenna, and a second matching resistor is connected to the cathode of the step recovery diode and the second part of the symmetric antenna. Said design provides an exact match between an output impedance of the sharpener and an input impedance of the antenna.

Brief description of drawings Fig. 1 illustrates a prior art of UWB sharpener for excitation a symmetric antenna.

Fig. 2 illustrates a UWB sharpener 1 for excitation a symmetric antenna constructed in accordance with the present invention.

Fig. 3 illustrates impulses describing a work of a UWB sharpener from the moment of receiving an activation impulse.

Fig. 4 illustrates radio pulses emitted by a symmetric antenna.

Detailed description of the invention

Next, with reference to drawings, the present invention will be described in detail.

In Fig. 2 is shown Ultra- Wideband (UWB) sharpener 1 for excitation a symmetric antenna 18. The UWB sharpener 1 comprises an avalanche transistor 2, which via its base 2B is connected to an source of pulses In, but via its collector 2K is connected to a timing resistor 4, coupled to a source of high voltage 3. A forming capacitor 6 is also connected to the collector 2K of the avalanche transistor 2. The sharpener 1 also comprises an emitter resistor 8 and a positive pulse control capacitor 10 that are connected to an emitter 2E of the avalanche transistor 2, wherein the emitter resistor 8 is coupled to a ground. The circuit of the sharpener 1 also comprises a step recovery diode 13 (SRD), which via its anode 13 A is connected to a first pumping resistor 14, coupled to a positive pump source 11, and via its cathode 13K is connected to the positive pulse control capacitor 10 and to a second pumping resistor 15, wherein the second pumping resistor 15 is coupled to a negative pump source 12. At the output of the sharpener 1 is provided a symmetric antenna 18 comprising two identical antenna parts 18A and 18B. The one part 18A of the antenna 18 is connected to the anode 13A of the step recovery diode 13 and other part 18B is connected to the cathode 13K of the step recovery diode 13.

The UWB sharpener 1 further comprises a base resistor 5 connected to the base 2B of the . avalanche transistor 2 and to the emitter 2E of the avalanche transistor 2. Said design of circuit decreases a drift of forming pulse. The UWB sharpener 1 further comprises a load resistor 7 and a negative pulse control capacitor 9, wherein the load resistor 7 and the negative pulse control capacitor 9 are connected to the forming capacitor 6. Other end of the negative pulse control capacitor 9 is connected to the anode 13A of the step recovery diode 13, and the other end of the load resistor 7 is coupled to a ground. It was found out that such a design of circuit helps to adjust amplitude of pulses much more easily comparing to the state of art sharpeners.

Additionally, the UWB sharpener 1 comprises matching resistors 16 and 17, wherein the first matching resistor 16 is connected between the anode 13A of the step recovery diode 13 and the one part 18A of the symmetric antenna 18. The second matching resistor 17 is connected between the cathode 13K of the step recovery diode 13 and the second part 18B of the symmetric antenna 18. In the state of art sharpeners as it is shown in Fig. 1 instead of the resistor 16 and 17 capacitors are used. Usage of resistors 16 and 17 and by adding previously made modifications of the circuit provides a possibility to maintain exact match of quantity between an output impedance of the sharpener 1 and an input impedance of the antenna 18.

Fig. 3 illustrates (a) - an activation impulse at an input In; (b) - an impulse at the collector 2K of the avalanche transistor 2; (c) - a pulse at the load resistor 7; (d) - a pulse at the emitter resistor 8; (e) - a pulse at the anode 13A of the step recovery diode 13; and (f) - a pulse at the cathode 13A of the step recovery diode 13.

Fig. 4 (a) illustrates a shape of emitted radio pulse in the absence of agreement with an input impendence of a symmetric antenna. Given figure illustrates impulses when there are no matching resistors 16 and 17 connected. Fig. 4 (b) illustrates a shape of emitted radio pulse at the optimum agreement with an input impendence of a symmetric antenna. It should be understood by those skilled in the art that the structure and details of the present invention may be changed in various manners without departing from the scope of the present invention. List of reference numerals

1 - a sharpener;

2 - an avalanche transistor;

2B - a base of the avalanche transistor;

2E - an emitter of the avalanche transistor;

2K - a collector of the avalanche transistor;

3 - a source of high voltage;

4 - a timing resistor;

5 - a base resistor;

6 - a forming capacitor;

7 - a load resistor;

8 - an emitter resistor;

9 - a negative pulse control capacitor;

10 - a positive pulse control capacitor;

11 - a positive pump source;

12 - a negative pump source;

13 - a step recovery diode;

13 A - an anode of the step recovery diode;

13K - a cathode of the step recovery diode;

14 - a first pumping resistor;

15 - a second pumping resistor;

16 - a first matching resistor;

17 - a second matching resistor;

18 - symmetric antenna;

18A - one part of a symmetric antenna;

18B - other part of a symmetric antenna;

In - a source of pulses.