Patent GB-1477484-A (GB)
Title: Method and circuits for transmitting and receiving pulse  sequences by means of radio connections
IPC: H04J13/00
Filed: 1974-05-17
Abstract: 1477484 Transmission of pulse sequences LICENTIA PATENT VERWALTUNGS GmbH 17 May 1974 [17 May 1973] 22191/74 Heading H4L In a system in which the same pulse sequence is transmitted over several radio paths, each pulse of the sequence is modulated by a particular code word taken from a series of n code words, so that a particular pulse may be identified by appropriate demodulation irrespective of its transmission path and interference between the signals received via different paths may be reduced. The number n in the code word series is such that the transmission time for the series is greater than the differences in transmission time to be expected of like pulse sequences transmitted by different paths. All the bits of the code word (e.g. 5 bits) occupy one pulse width of the pulse sequence. In one simple transmitter-receiver arrangement (Figs. 3 and 4, not shown), pulses to be transmitted are applied to a modulator and also to a synchronising circuit which controls a code word generator. The generator produces a sequence of code words which are in turn applied to the modulator in synchronism with the data pulses. The modulated output pulses are applied to a radio transmitting stage. At the receiver, received signals are applied to both a synchronising circuit controlling a code word generator identical to that in the transmitter and also to a modulator. The code words are also applied to this to produce an output which is applied to an integrator. The output of the integrator is periodically inspected by a scanning circuit operated by the synchronising circuit and applied to an output device. In a more elaborate transmitter in which each code word pulse is of the same length as an information pulse (Fig. 5), serial data to be transmitted is applied to a serial/parallel converter 52, such that 8 successive pulses are produced in parallel. These are first held in 8 stores 541-548 whose outputs, each pulse being widened 8 fold, are applied to 8 modulators 551-558. These modulators each receive a different code word from a sequence of 8 code words developed in parallel by a generator 56 in response to a synchronizing signal from unit 53 triggered by the input sequence of data pulses. The 8 modulated pulses are passed to a scanning circuit 57 before transmission as a composite pulse. The receiver may be an inverse arrangement of the transmitter (Fig. 6, not shown) with the received signal applied to a parallel array of 8 modulators, each receiving a different code word from a sequence of 8 code words derived in parallel from a generator activated in synchronism with received pulses. After integration, the modulator outputs are scanned, stored and applied to a parallel/serial converter. Alternatively the receiver may contain a matched filter type arrangement. The received signals are applied to a serial parallel converter 72 (Fig. 7) having as many places as there are bits in a code word (5). The parallel outputs from this are applied to each of n (e.g. 8) summing circuits 741-74n either directly or via inverters, the particular arrangement for each individual summing circuit being in accordance with one of the code words in the sequence used at the transmitter. The summing circuits are read-out by scanning circuits 751-75n operated from a timing circuit 73 which determineswhen a whole code word has been received into stores 761-76n. These are read-out in series to provide the originally transmitted data.