DE4202435A1 - GPS satellite-synchronised chronometer with local time display - uses XTAL-controlled clock and interpolation signal processor - Google Patents

Abstract

The radio synchronised clock contains an antenna (10) and radio receiver (20) consisting of pre-amp (22), IF section (24) and a crystal oscillator (26). The oscillator maintains local time with error delta tB (28). GPS satellites (12,14,16,18) transmit synchronising signals and time codes. By determining the relative timing of these signals, local time and position are generated by processor (30). An error estimate for delta tB is output (32) to a time generator (34). Longitude (36) is output to time-zone store (38) which outputs the difference between the Local Mean Time and GMT to the time generator. By these means a chronometer is realised which automatically indicates local time worldwide and with satellite time synchronisation. USE - Ship navigation and chronometer.

Description

The invention relates to a radio-controlled watch with a Clockwork with a time display, an antenna and Receiving means for receiving radio signals and generation of radio support signals and means for correcting the time display by the radio support signals.

The movement is expediently a quartz movement. The Invention is also in mechanical watch movements applicable.

The accuracy of quartz watches is known Support radio signals from a long wave transmitter be sent out which time signals of high accuracy sends out. Signals can also be sent via this transmitter are received, the automatic switching of the Effect clock from summer time to winter time and vice versa.

A disadvantage of such watches is the fact that the Radio support signals only in the range of the concerned station can be received. That is about a radius of 1500 km. This is not a worldwide one Use of radio-controlled clocks possible.  

Navigation systems based on radio signals are known based on satellites. One such system is the "GPS" (Global Positioning System). With such a system from the signals from four satellites, from one Receivers on Earth are received a position information gained. The satellites each send one up accurate GPS time signal, a pseudo random code and one Time stamp (satellite clock) for sending this Random codes. The random code is a periodic repetitive, irregular sequence of impulses. This Random code becomes one in the receiver of one Receiver clock at a specific point in time with a similar, Correlated pseudo-random code generated in the receiver. For this purpose, the recipient's random code is over shifted back and forth over a certain period of time, in other words, phase-modulated. At a certain Phase occurs a correlation: the pseudo-random codes coincide. A correlation arises maximum. The location of this correlation maximum, i.e. the Time related to a reference mark at which the Correlation maximum occurs depends on the Runtime of the electromagnetic waves from the satellite to Receiver, or - in other words - the distance of the Satellites from the receiver, and also from one Time error of the receiver clock compared to the satellite clock. There are now the signals from four in the same way Receive and evaluate satellites. Are known then the positions of the satellites and the distance to the Receiver, the latter due to the time error is falsified. From the four obtained The position of the Be determined by the recipient. The time error is one Auxiliary size, which arises but is not used.  

It is still long-wave navigation systems such as the LORAN process or the OMEGA process known. These also serve exclusively for positions determination.

The invention has for its object a worldwide to create usable radio-based clock.

The invention is further based on the object of a watch to train so that they automatically on the different time zones in which they are currently is operated.

According to the invention, the former object is achieved by that

• a) the receiving means to receive signals from Navigation radio networks are coordinated and
• b) radio signals from the received signals are derivable.

A is therefore not used to generate radio support signals separate transmitter related, which only in a limited Range can be received. Rather be Navigation radio networks used that are available worldwide are. Such navigation radio networks usually serve only for generating position information. These Navigation radio networks are different according to the invention from its actual purpose to the generation of radio support signals to support the time display of clocks exploited. The invention is based on the knowledge that that is possible.  

The receiving means for receiving and set up to process satellite signals, where the signal processing of the satellite signals accumulating time information form the radio support signals. In particular, the receiving means for receiving and Processing of GPS satellite signals can be set up.

The second problem can be solved in that

• a) Signal processing means position information deliver,
• b) the position information on storage means are switched, in which for the different Time zones the time differences from one of the Navigation radio network delivered time information are stored, and
• c) the time displayed by the watch depending on the position information regarding this time difference is corrected.

The position information can be geographical Length.

An embodiment of the invention is as follows with reference to the accompanying drawing which explains a block diagram of an arrangement for radio support of a watch using a satellite Navigation system shows.

With 10 an antenna is designated, which receives signals from four GPS satellites 12 , 14 , 16 and 18 . The GPS satellites each send a highly precise time signal, their ephemeris data and a specific pseudo-random code as well as a time stamp (satellite clock) for the transmission of this pseudo-random code.

The antenna 10 is connected to a receiver 20 . The receiver 20 contains a preamplifier 22 , an RF part 24 and a quartz oscillator 26 . The quartz oscillator 26 represents the receiver clock. The quartz oscillator has a time error Δt _B. This is indicated by arrow 28 .

The HF part effects the generation and phase modulation of the pseudo-random code in the manner outlined above, which is known per se in GPS devices. The sequence of the pseudo-random code corresponds to the pseudo-random code sent out by the satellite. A correlation maximum occurs at a certain phase position. From the position of this correlation maximum, a measured value for the distance to the satellite 12 , 14 , 16 or 18 is obtained. If the receiver clock, namely the quartz oscillator 26 , were to operate in exactly synchronous fashion with the satellite clock, then the distance to the satellite could be determined directly from the position of the correlation maximum. Due to the "gait error" of the satellite clock, the output signal PS is only an apparent distance (pseudo range). However, the information from four satellites is available. From the four equations formed from this, the position of the receiver 20 on the earth's surface and the time error Δt _{B of} the quartz oscillator can be determined by means of a processor 30 . The geographical longitude can be determined from the equations as further information.

An estimated value for the time error Δt _B is obtained at an output 32 and switched to a time generator 34 . The geographic longitude, which is obtained at an output 36 , is applied to a memory 38 .

The memory 38 contains the time differences between local time (LMT) and Greenwich time (GMT) for the different time zones, which are determined by the geographical longitude (and possibly also by the geographical latitude). These time differences are also applied to the time generator 34 via an output 40 . Finally, the time generator receives the GPS time signal from the receiver 20 via an output 42 .

The Greenwich Mean Time GMT can be signaled using the GPS time signal and the transit times of the pseudo-random code signal from the satellite. B. 12 to the receiver 20 . The running time must be corrected by the measured error Δt _{B of} the quartz oscillator 26 as the receiver clock. Furthermore, the Greenwich Mean Time GMT is corrected by the time difference of the relevant time zone output by the memory 38 for the measured position. From this, the time generator 34 outputs the exact local time (LMT). This is displayed by a display device 44 .

In this way, a clock can be realized that adjusts itself automatically to the local time and via Satellite signals is supported with high precision worldwide.

Claims (5)

1. Radio-controlled clock with a clockwork with a time display, an antenna and receiving means for receiving radio signals and generating radio support signals and means for correcting the time display by the radio support signals, characterized in that

• a) the receiving means are matched to the reception of signals from navigation radio networks and
• b) radio support signals can be derived from the received signals.

2. Radio-controlled clock according to claim 1, characterized characterized in that the receiving means for receiving and set up to process satellite signals are, which in the signal processing of Satellite signals accumulating time information Form radio support signals. 3. Radio-controlled clock according to claim 2, characterized records that the receiving means for receiving and Processing of GPS satellite signals set up are.   4. Radio-controlled clock according to one of claims 1 to 3, characterized in that

• a) signal processing means deliver position information,
• b) the position information is switched to storage means in which the time differences for the different time zones compared to a time information supplied by the navigation radio network are stored, and
• c) the time displayed by the clock is corrected as a function of the position information with regard to this time difference.

5. Radio-controlled clock according to claim 4, characterized records that the position information the longitude is.