Introduction

Radio navigation is a set of operations for determining the course of the objects (aircraft, ships), as well as to direct them.

The main task of navigation is to direct a moving object by the optimal trajectory to the sertain point.

At the present stage of development of civil aviation (CA) the high demands placed on improving the quality of its work and above all to improving of the safety and regularity of aircraft operations (AO). A successful solution of this problem is largely determined by the level of development of navigational aids, including radio navigation aids of flight safety.

Navigation systems by accuracy are characterized by error of navigation parameters (NP) measurement.

Accuracy is a qualitative characteristic that determines the proximity of measurement results to the true value of navigation parameter.

1.General information about the frequency-phase method of radio navigation measurements

The radio beacon is designed for generation and radiation of radio signals, ensuring measurement of the azimuth angle of the aircraft equipped with avionics systems VOR. The radio beacon is used in airports and on navigation aircraft highways of civil aviation.

DVOR 2000 radio beacon has a signal form of VOR equipment and answers the requirements for this equipment set out in the "Annex 10 to the Convention on International Civil Aviation (ICAO)». Radio beacon can be used in a complex with distance measuring beacon DME / N and as a standalone product.

The structure of the beacon includes hardware (container with equipment), antenna system, two control antennas and remote control equipment RCE 2000. Signal generating equipment and control and monitoring one of the beacon is placed in a container fitted with temperature control system. The antenna system consist of a central one and 48 ring emitters arranged in a circle diameter of 13.5 m. Radiators of the antenna system installed on the reflector diameter of 30 m.

The system of internal control provides automatic control of all key beacon parameters, the search and localization of faults with the accuracy up to replacement unit (RU). The radio beacon parameters and state of the equipment are displayed on the color display in graphical mode. While operation all changes in the state of the equipment and staff actions are recorded and stored for 30 days in the remote control equipment.

Beacon can be managed with local control panel or by remote control RCE 2000, which can be located at a distance of 10 km. Changing of the beacon equipment state or settings is conducted by light and sound alarms.

The RCE 2000 equipment provides an access to information about the parameters of the beacon on the local Ethernet network using TCP / IP protocol or the ATN network, in accordance with the protocol CCITT X.25.

The system of internal control provides automatic control of all key beacon parameters, the search and localization of faults with the accuracy up to replacement unit (RU). The radio beacon parameters and state of the equipment are displayed on the color display in graphical mode. While operation all changes in the state of the equipment and staff actions are recorded and stored for 30 days in the remote control equipment.

In beacon all the main devices are reserved: a signal former, a transmitter, a control unit, control antennas, the power supplies, control module.

One set of the main devices of beacon is installed in a rack (cabinet). As a reservation set of device us used a second similar cabinet with additional switching kits. In operation, the control of the main and reservation equipment is provided. Switching to the reservation set is carried out automatically by the signal of control devices.

Beacon power is provided from the main and reservation three-phase network 380/220 V, 50 Hz. Within 30 minutes, the beacon can be powered by batteries. Operating mode of a beacon is a continuous non-stop, without the constant presence of staff.

The rack and the modules construction is designed according to IEC 297 (Euromechanics). In the beacon equipment are used standardized modules, boards and devices, as well as a modern element base and surface mount technology.

Application of the Doppler principle of direction finding is possible also in radio beacon goniometrical systems. Since, according to the principle of reciprocity in the creation and allocation of information about the direction on the object between the radio beacons and direction finders there is no difference (as there is no fundamental difference between their antennas), the analysis of Doppler finders can be adequately classified as Doppler beacons. Therefore, the signal generated at each point in space by the rotation of transducer A1 (Figure 1.a) relative to the fixed oscillator A2 is described by:

,

Where w0 - carrier frequency of the emitted signals, i.e. due to the Doppler signal frequency (phase) changes, modulation envelope contains information about the angular position of the object relative to the beacon. To allocate this information is used a phase reference signal emitted by the central antenna A2. In this case, the frequency deviation signal

The change of frequency caused by the rotation of the antennas A1 and signals of variable (Ua1) and the reference (Ua2) phases for receiving point with a bearing = 90 shown in Fig. 1.b.

To create a Doppler frequency signal spectrum of the beacons, corresponding to the spectrum of the standard goniometrical beacons VOR, the antennas A1 and A2 emit oscillations of a more complex form. Central antenna radiates AM oscillation for generating a reference phase signal,

where - coefficient of carrier AM by signal frequency.

On a set of vibrators that imitate the movement of the antenna A1 (Fig. 1. C), the signals of carrier AM by auxiliary subcarrier frequency _s.

In turn, the subcarrier frequency is modulated by frequency as a result of antenna A2moving. Thus, the mobile antenna creates a combined AM - FM signal, which is being adopted at a distance from the beacon, is much greater than doubled distance.

For signal processing of Doppler angle measuring beacon (DVOR) is applied onboard receiver of standard system VOR. But in this case, bearing information is contained in the phase of the FM fluctuations.

Sizes of circle (2r) in DVOR beacons are taken much larger than the wavelength to reduce direction finding errors caused by clutter and uneven terrain reflections.

The large sizes of the DVOR antenna system lead to a decrease in the influence of clutter on the bearing accuracy is about 10 times compared to standard beacons VOR. For almost complete elimination of the influence are developed precision Doppler beacons PDVOR, in which the bearing information is transmitted in the same way as in

DVOR. The signal for the phase reference oppositely to DVOR in precision beacon transmitted by sub-carrier frequency of 6500 Hz, a frequency-modulated by oscillation of reference phase with switching antennas frequency.