In order to achieve a higher resistance to interference with respect to alien sources of deliberate interference in the use of communication connections via short waves, certain cooperative measures are proposed which include that the stations are equipped with highly-constant quartz crystal clocks and the bursts of information to be transmitted are accompanied by a time signal with the aid of which it is possible to correct any time tolerances between the stations. With an acknowledgment signal, use is made of a frequency variation of the radio frequency in the timing of consecutive burst transmissions including the acknowledgment response. The information contained in a burst in a fault safeguarded fashion is transmitted in coded form. The code sequence for encoding the information component and the fault safeguarding component of a burst and for the frequency address which determines the transmitting and receiving frequencies is recalculated for each burst on the basis of the clock time of the quartz crystal clock and on the basis of a subscriber number.
A simple and economical, yet tamper-proof, electronic locking apparatus for motor vehicles features an electronic key and an electronic lock, which each contain a synchronized, constantly operating, precision oscillator. The output of each oscillator is applied at a predetermined counting rate to a respective number sequence generator. Both generators contain the same predetermined number sequence, which they step through at the same clock rate, applying the instantaneous value of the count to a first input of a respective computer. A second input of each computer is connected to a fixed memory which supplies a permanent, characteristic code number to the computer. Both the count state and the characteristic code number are combined using corresponding algorithms in the key and in the lock to produce a combination code. The key-produced combination code is sent from a transmitter in the key to a receiver in the lock and compared there with the lock-produced combination code. In the event of a successful comparison, a control pulse is generated, which actuates various positioning means in the lock.
In radio operation in tactical use, an increased jamming resistance with respect to intentional jamming is required. For protection against intentional jamming, frequency hopping techniques have proven very advantageous in which the signals are transmitted in the form of successive error-protected signal blocks where each signal block is transmitted on a different radio carrier frequency which changes in a pseudo-random manner. With this technique, phase shifts can occur which are greater than half a bit and therefore make analysis of the signal blocks difficult or impossible. It is proposed herein that each received signal block be checked after regeneration in a regenerative repeater, controlled by a bit clock pulse, as to its correct block phase and therefore, respectively, newly establish the block clock pulse phase required for further accurate processing of a signal block.
A cellular radiotelephone system providing service to remote units having a voice operated transmitter (VOX) is disclosed. If the regularly scheduled periodic signal quality measurements made by fixed site equipment indicate that the remote unit signal has not been received for a predetermined number of measurements, an audit request is transmitted to the remote unit. The remote unit responsively keys its transmitter for a predetermined period of time. A first special scan is programmed into the regular process such that the fixed site equipment may continue with its regular process until the signal quality measurement must be made. A second measurement is made following the first and if the two signal quality measurements made while the VOX remote unit is known to be transmitting agree, system reconfiguration for the service of this remote unit may be implemented by the cellular system.
This invention generally relates to wired and wireless ultra wideband (UWB) data communications apparatus and methods, and in particular to UWB receiver systems and architectures.An ultra wideband (UWB) receiver system comprising: a receiver front end to receive a UWB signal; an analogue-to-digital converter coupled to said receiver front end to digitize said received UBW signal; and a correlator coupled to said analogue-to-digital converter to correlate said digitized UWB signal with a reference signal.
