# Hyperbolic Asynchronous Method of a Radio Navigation Technique
## 5 Measurement's Verification of the Asynchronous Method of Radio Navigation
### Technological Localization Demonstrator for Measurement Verification  
The two main components of the asynchronous locating technology demonstrator are described below, the construction and operation of the reference station and locating device (User Terminal). Both of these devices have been designed on the basis of the concept described in Section 3. The devices are built using ready-made components in the form of generators, receivers, amplifiers, computing units and data acquisition cards. The software layer covering signal processing as well as control and the control of the whole system is original [16]. Functional block diagrams of the reference station and the locator (User Terminal) are shown in Figures 18 and 19, respectively. As it can be seen in Figure 18, a reference station is a receiving and transmitting system equipped with an omnidirectional antenna (1). The radio signals containing location messages received by such an  
Figure 19: Functional locator (User Terminal) block diagram. Figure 18: Functional reference station block diagram. antenna, potentially from all directions, pass through the switch (transmit/receive) (2) and then through the coupler (3) to reach the broadband receiver (high frequency). (4) This takes place during a cyclic 8-s break forced by the switch (2), during which the transmission track, namely the power amplifier (10), is disconnected, as described in Section 3.2. In contrast, the received radio signal, still in the HF band, is amplified in the receiver (4) and then transferred (converted) to the IF band (intermediate frequency). This signal is then fed to the input of the data acquisition card (5) located in the computer (6), which controls the operation of the reference station (using LAN (Local Area Network) connection to a receiver (6)) and the implementation of time difference measurement procedures occurring in dependencies (14). Another function of the reference station is the creation of location messages, which takes place in the module (8) under the supervision of a single-board computer (7) which is connected with an RS-232 interface. These messages are placed in the radio signal, whose source is a generator (9) which is connected with (7) using LAN connection. This signal is fed to the power amplifier (10), where it is subject to the amplification necessary to ensure a certain range of operation of the reference station. When the transmission track is unlocked, the signal passes through switch (2) to the antenna (1), from which it is radiated to the propagation environment. Taking into account the necessary high accuracy of time measurement, the reference stations of the described demonstrator used external frequency standards based on the rubidium standard by Stanford Research Systems, which ensured the generated frequency stability at the level \(10^{-11}\)[25]. For comparison, commonly used external frequency standards are characterized by a stability of \(10^{-7}\). The locator (User Terminal) shown in Figure 19 is a receiving system only, which receives signals transmitted by reference stations. These signals, after being received by the antenna and also omnidirectional, are fed to the broadband receiver where they are amplified and converted to the IF band. These signals from the receiver's output go to the data acquisition card located in the control computer, where they are used to decode the location messages described in Section 3.2. On the basis of the information contained in these messages and the calculations performed in the control computer, the current position of the locator (User Terminal) is determined by the relationship (15). Reference station and locator (User Terminal) software was written in C++ language using the Borland Builder application, but for visualization of the results, an application written in the Java environment was made. The control computer software at the reference station carries out time difference measurement procedures and configures and controls the receiver and data acquisition card.