The subject of the invention is a system for detecting RF signals, intended for detecting and measuring electromagnetic signals transmitted in radio frequency bands ranging from 3 kHz to 300 GHz, for use in telecommunications, military and civilian applications.

The description of US4503388 patent shows a system for detecting RF (radio frequency) signals using the diffraction of a coherent light beam on a diffraction grating generated in an acousto-optic component as a result of acoustic wave propagating inside it. The wave is excited by a piezoelectric transducer connected to the antenna. The acousto- optic component diffracts a light beam proportionally to the RF signal frequency. Behind the acousto-optic unit there is a focusing lens, semiconductor amplifier and a linear photodetector. The detection system for RF signals includes a monochromatic laser emitting a beam of light at a specific wavelength, depending on the type of active medium. In a typical embodiment, this is a laser arranged as a resonator system, comprising an active medium pumping system placed in a resonant cavity between the system of parallel mirrors, one of which constitutes a semi-reflective outlet mirror. Pumping the active medium results in population inversion that leads to stimulated photon emission. The mirrors reflect part of the emitted photons back to the active medium. Such an optical system is a type of resonator for a specific frequency of electromagnetic waves.

A disadvantage of such RF detection systems is their limited scope of application and the necessity of using complex laser light amplifiers.

The system for RF signal detection, equipped with an acousto-optic component that diffracts the light beam emitted in the monochromatic laser resonator system, a focusing lens placed in the route of diffracted light beam placed between the acousto-optic unit and a multi-segment photo detector, while the acousto-optic unit includes a piezoelectric transducer connected to the antenna, according to the invention, rely on that its acousto- optic component is placed together with the focusing lens in the resonator system between active medium and the matrix of optical fibers, which create a semi-reflective output mirror integrated with a multi-segment photo-detector, while the endfaces of optical fibers are located perpendicularly to the light beam and covered with a semi-reflective layer, and the opposite ends of optical fibers are connected to the multi-segment detector.

Advantageously, if the endfaces of optical fibers constituting the matrix form a concave spherical mirror directed towards the focusing lens. In particular, the endfaces of optical fibers creating the concave spherical mirror are located in a single plane

perpendicular to their surface.

Advantageously, if the focusing lens surface is coated with an anti-reflection layer. Advantageously also, if each optical fiber in optical fiber matrix is connected to different photosensitive unit of the multi-segment photo detector.

In the solution proposed by the invention, the acousto-optic component is a part of the monochromatic laser resonator system, changing the direction of beam propagation inside the resonant cavity, while the matrix of optical fibers is formed in such a way that each optical fiber can operate as a fragment of the resonator output mirror, depending on the angle of diffraction induced by the acousto-optic component. In this resonator arrangement only the light projected perpendicularly to the optical fiber is amplified. This light is recorded on the multi-segment photodetector. Thanks to the selective amplification of signal propagating at a specific direction, i.e. for a specific angle of light beam diffraction, it is possible to record even very weak signals. Based on the signal distribution, it is possible to determine the angle of beam diffraction, and consequently, the RF signal parameters within the whole range of electromagnetic waves at a very high signal-to-noise ratio.

The invention is presented in one of the embodiments in a figure that shows a schematic diagram of the RF signal detection system.

The RF signal detection system is equipped with an acousto-optic component 4 placed together with the focusing lens 7 in the monochromatic laser resonator system between active medium 1 , and the matrix of optical fibers 5 that constitute the semi- reflective output mirror integrated with the multi-segment photodetector 6. The acousto- optic component 4 consists of a piezoelectric transducer connected to an RF receiving antenna. The acousto-optic unit 4 diffracts a light beam emitted in the resonator towards the focusing lens 7, and it focuses the passing light beam on a fragment of the matrix of optical fibers 5. The endfaces of optical fibers 5 are situated perpendicularly to the direction of light beam and covered partly with a light reflecting layer, while the opposite ends of optical fibers 5 are connected to the multi-segment photo detector 6. The multi- segment photo detector 6 can be made in the shape of a photo ruler, matrix or other set of photosensitive components. The endfaces of optical fibers 5 being part of optical fiber matrix 5 have the form of a spherical concave mirror directed to the focusing lens 7. Such a mirror can be made with one row of optical fibers 5 with their endfaces situated in a single plane perpendicular to their surface. It can be a spherical mirror made in spatial or planar technology. For planar technology mirror, optical fibers 5 will be made as specially designed planar optical fibers. The surface of focusing lens 7 should be coated with an anti- reflective layer to avoid initialization of laser action on this particular system component.

The monochromatic laser resonator system includes a pumping system 2 for active medium 1 and a reflecting mirror 3 of the reflection coefficient equals to 100%. The pumping system 2 can use diode illuminants or flashlights to provide light for active medium 1 in the form of a crystal, which results in exciting the active medium 1 and obtaining population inversion. As a result of spontaneous emission, photons from active medium 1 are emitted at all directions. Part of them is projected onto the acousto-optic system 4, where RF signals are transformed into acoustic signals. The acoustic signals stimulate the generation of spatial diffraction grating by the periodic condensing and dissolving the acousto-optic component 4. The photons emitted spontaneously from active medium 1 falling onto the generated diffraction grating are subject to diffraction. The angle of light beam diffraction, for a specific wavelength depends on the diffraction grating period. A diffracted light beam is partly reflected from the optical fiber matrix 5. The layer, the optical fiber 5 endfaces are covered with, should reflect approximately 60% of the incoming light. The light reflected from optical fiber 5, whose endface is perpendicular to the direction of incoming beam, returns to the resonator system starting the process of laser light emitting in the active medium 1. It results in a considerable amplification of light beam emitted in the specific direction defined by its diffraction angle on the diffraction grating. The focusing lens 7 set in the path of diffracted light beam is intended for focusing light on optical fibers 5, thus increasing the resolution of the system in terms of frequency. Part of the light passing through the optical fibers 5 reaches the multi-segment photo detector 6 fitted with photosensitive components measuring the intensity of light propagating within each optical fiber 5. By comparing signals with particular photo components it is possible to determine the angle of beam diffraction on the diffraction grating, thus, knowing the laser wavelength it is possible to determine the parameters of an RF signal incoming to the acousto-optic system 4.