Patent CZ-9803870-A3 (CZ)
Title: Information transmission method, particularly of global satellite system correction data through the mediation of transmitters within the frequency band of 30 kHz and 30 MHz and apparatus for making the same
Inventor: VEJRAZKA FRANTISEK PROF ING CS
IPC: H04B7/185
Filed: 1998-11-26
Abstract: When transmitting data, the modulation pulse characteristic is modified so that the modulated signal phase and at least the first derivation thereof are continuous functions and instantaneous phase thereof matched at the start, in the middle and at the end of each bit with the phase of the initial non-modified modulated signal. The obtained modified modulated signal is the divided into individual time samples that are quantized and information regarding characteristic of the corresponding high-frequency signal (VFS), forming a set of basic building elements of the output VFS of one bit duration is stored into memory. Data intended for transmission are compressed and then divided into blocks of 60-bit length consisting of 41 information bits and 19 check bits, where at the most 8 initial and 1 stop bit from that 41 information bits of every message distinguish individual, predefined types of data blocks. Prior sending the individual data blocks, the even information bits are inverted. The  modulation itself of the carrier wave is carried out by direct digital synthesis thereof by selecting the basic building elements selected from the VFS sample memory so that these samples follow continuously each other. The compressed content of the message to be transmitted is transmitted to a transmitter and decoded to obtain the originally transmitted correction data. Modulation portion of the apparatus transmitting section comprises at least one modulator (100) having a its output a microprocessor (6) being connected to a first and a second input/output communication interface (VVKR) (200. 201) and further directly with one output of a counter (BC) block (2), via a temperature compensated crystal controlled oscillator (1) to one input BC (2) and further to one input of a VFS sample memory (3). Said VFS sample memory (3) second input is connected with said BC (2) second output, while the second output thereof is connected via a digital-to-analog converter (4) with the input of an output filter and amplifier block (5) the output of which is connected via an envelope detector (9) with a second microprocessor (7) that is connected to the first VVKR (200) to connect a bidirectional serial communication line (210). Receiving portion (500) is formed by two first mixers I (10) and Q (11) having their inputs connected to an antenna (50) and having their outputs connected to the input of a first intermediate frequency (mf) filter (12) the output of which is connected via a fist intermediate frequency (mf) amplifier (13) with one input of the second mixer (14) that is further connected with the input of a block (15) formed by a second intermediate frequency filter and a second intermediate frequency amplifier. Said block (15) output is connected to a microprocessor (20) being connected with a fundamental crystal-controlled oscillator (19). Said fundamental crystal-controlled oscillator (19) is connected with one input of a first local oscillator (17) and an input of a second local oscillator (18) the output of which is connected to the second input of the second mixer (14). The output of said first local oscillator (17) is connected directly to the second input of the first mixer I (10) and via a 90-degree advance phase shifter (16) to the second input of the first mixer Q (11). Said microprocessor (20 output is the output of the received data.