Clock synchronization when switching between broadcast and data transmission modes

Patent metadata

Field	Value
Publication number	US-11201720-B2
Application number	US-202015929271-A
Country	US
Kind code	B2
Filing date	Apr 21, 2020
Priority date	Oct 24, 2017
Publication date	Dec 14, 2021
Grant date	Dec 14, 2021

Abstract

A communication system allows for clock synchronization between a transmitter and a receiver when switching from transmission of an analog signal to transmission of a digital signal. The system uses clock synchronization during transmission of the digital signal, but the clock synchronization may be lost when switching to transmission of an analog signal. A digital clock synchronization is embedded in the analog signal so that the clock synchronization between the transmitter and the receiver may be reestablished upon switching to a digital signal without any delay in transmission of the digital signal.

First claim

What is claimed is:

1. A system comprising; a transmitter including a transmitter clock, wherein the transmitter is configured to switch between transmission of a digital signal and an analog signal; and a receiver including a receiver dock, wherein the receiver is configured to receive the signal transmitted from the transmitter; wherein the transmitter is configured to transmit the signal to the receiver through skywave propagation; wherein the transmitter and the receiver are spaced apart to have at least one skip zone between the transmitter and the receiver; wherein the transmitter is configured to transmit a clock synchronization signal; wherein the clock synchronization signal is transmitted between the transmitter and the receiver, wherein the clock synchronization signal is configured to synchronize the transmitter clock and the receiver clock; wherein the clock synchronization signal is embedded in the analog signal so that the clock synchronization signal is transmitted with the analog signal; wherein the transmitter clock and the receiver clock are synchronized by the clock synchronization signal without a delay when the transmitter switches from transmitting the analog signal to the digital signal; wherein the receiver is configured to correct for signal distortions caused by the skywave propagation using the clock synchronization signal embedded in the analog signal.

2. The system of claim 1 , wherein the analog signal is an Amplitude Modulation (AM) signal.

3. The system of claim 1 , wherein the clock synchronization signal is a phase modulated signal.

4. The system of claim 1 , wherein the clock synchronization signal is transmitted during the entirety of the transmission of the analog signal.

5. The system of claim 1 , wherein the clock synchronization signal is transmitted with the analog signal only for the time needed to establish synchronization before the transmitter switches from the analog signal to the digital signal.

6. The system of claim 1 , wherein the analog signal is used for station identification.

7. The system of claim 1 , wherein the analog signal is an audio broadcast.

8. The system of claim 1 , wherein the digital signal transmits financial trading data.

9. The system of claim 1 , wherein the transmitter clock and the receiver clock are set based on time data received from a global positioning system.

10. A method comprising: embedding a clock synchronization signal in an analog signal wherein the clock synchronization signal is configured to synchronize a transmitter clock and a receiver clock; transmitting the analog signal and the embedded dock synchronization signal from a transmitter to a receiver; switching the transmission from the transmitter from the analog signal to a digital signal; wherein said transmitting includes transmitting the analog signal via skywave propagation from the transmitter to the receiver; wherein the transmitter and the receiver are spaced apart to have at east one skip zone between the transmitter and the receiver; transmitting the digital signal via skywave propagation from the transmitter to the receiver; wherein the transmitter clock and the receiver clock are synchronized by the clock synchronization signal without a delay when the transmitter switches from transmitting the analog signal to the digital signal; and correcting for distortions of the digital signal at the receiver using the clock synchronization signal embedded in the analog signal.

11. The method claim 10 , wherein the analog signal is an Amplitude Modulation (AM) signal.

12. The method of claim 10 , wherein the clock synchronization signal is a phase modulated signal.

13. The method of claim 10 , wherein the clock synchronization signal is transmitted during the entirety of the transmission of the analog signal.

14. The method of claim 10 , wherein the clock synchronization signal is transmitted with the analog signal only for the time needed to establish synchronization before the transmitter switches from the analog signal to the digital signal.

15. The method of claim 10 , wherein the analog signal is used for station identification.

16. The method of claim 10 , wherein the analog signal is an audio broadcast.

17. The method of claim 10 , wherein the digital signal transmits financial trading data.

18. The method of claim 10 , wherein the transmitter clock and the receiver clock are set based on time data received from a global positioning system.

19. A system comprising: a transmitter including a transmitter clock, wherein the transmitter is configured to switch between transmission of a digital signal and an analog signal; and a receiver including a receiver clock, wherein the receiver is configured to receive the signal transmitted from the transmitter; wherein the transmitter is configured to transmit a dock synchronization signal; wherein the clock synchronization signal is transmitted between the transmitter and the receiver, wherein the clock synchronization signal is configured to synchronize the transmitter clock and the receiver clock; wherein the dock synchronization signal is embedded in the analog signal so that the clock synchronization signal is transmitted with the analog signal: wherein the transmitter clock and the receiver clock are synchronized by the clock synchronization signal without a delay when the transmitter switches from transmitting the analog signal to the digital signal; wherein the clock synchronization signal is transmitted with the analog signal only for the time needed to establish synchronization before the transmitter switches from the analog signal to the digital signal.

20. The system of claim 19 , wherein the analog signal is an Amplitude Modulation (AM) signal.

21. The system of claim 19 , wherein the clock synchronization signal is a phase modulated signal.

22. The system of claim 19 , wherein the analog signal is used for station identification.

23. The system of claim 19 , wherein the analog signal is an audio broadcast.

24. The system of claim 19 , wherein the digital signal transmits financial trading data.

25. The system of claim 19 , wherein the analog signal is transmitted wirelessly by skywave propagation.

26. The system of claim 19 , wherein the transmitter clock and the receiver clock are set based on time data received from a global positioning system.

27. A system comprising: a transmitter including a transmitter clock, wherein the transmitter is configured to switch between transmission of a digital signal and an analog signal; and a receiver including a receiver clock, wherein the receiver is configured to receive the signal transmitted from the transmitter; wherein the transmitter clock is configured to generate a clock synchronization signal; wherein the clock synchronization signal is transmitted between the transmitter and the receiver, wherein the clock synchronization signal is configured to synchronize the transmitter clock and the receiver clock; wherein the clock synchronization signal is embedded in the analog signal so that the clock synchronization signal is transmitted with the analog signal; wherein the transmitter is configured to transmit the analog signal for an analog time period; wherein the transmitter is configured to transmit the digital signal for a digital time period; wherein the digital time period occurs after the analog time period ceases; wherein the clock synchronization signa

Assignees

• Skywave Networks Llc

Inventors

• Babich Kevin J

Classifications

• H04H20/86

  Arrangements characterised by the broadcast information itself · CPC title

• H04H20/26

  Arrangements for switching distribution systems · CPC title

• H04H40/09

  Arrangements for receiving desired information automatically according to timetables · CPC title

• H04L7/0008 Primary

  Synchronisation information channels, e.g. clock distribution lines · CPC title

• H04H20/33

  by plural channels · CPC title