Docking unit and vehicle power adapter with frequency modulated audio signal injection for connecting portable media player and/or communications device to vehicle FM radio and audio system for playback of digital audio broadcast stream
View Patent ↗A cigarette lighter adapter (CLA) is provided with a main body configured to be connected at one end thereof to a vehicle cigarette lighter socket or auxiliary power socket. The main body of the cigarette lighter adapter is also connected to one end of a coaxial cable. The other end of the coaxial cable is preferably terminated with a standard low cost DC connector for connection to a portable media player (e.g., with integrated or separate satellite radio receiver) or other content source that provides a frequency modulated (FM) radio frequency signal with audio content onto the coaxial cable 60 . The FM signal is amplified by an amplifier in the main body of the CLA and then injected into the vehicle power system through the contacts in the mechanical housing of the main body and the vehicle cigarette lighter socket.
1. A vehicle power adapter for providing frequency modulated (FM) radio frequency signals from an external device to an FM receiver in a vehicle using the vehicle's existing wiring system without modification of the vehicle's electrical connections behind the vehicle's dashboard and without over-the-air transmission of the FM signals, the vehicle power adapter comprising:
a main body configured to be received in a cigarette lighter socket of the vehicle, the main body having a first connector to receive direct current (DC) power from the vehicle power system when inserted into the vehicle cigarette lighter socket;
a coaxial cable having a first end connected to the main body and a second end extending therefrom; and
a second connector connected to the second end of the coaxial cable and configured for detachable connection to an external device;
wherein the main body comprises an amplifier circuit configured to receive the FM signals from the external device via the coaxial cable and to amplify the FM signals to a selected signal level that allows for their transmission to the FM receiver in the vehicle via the vehicle's existing and unmodified wiring system for reception and playback by the FM receiver, the main body being configured to provide the amplified FM signals to the vehicle's existing and unmodified wiring system when inserted into the cigarette lighter socket.
2. A vehicle power adapter as claimed in claim 1 , wherein the main body further comprises a DC to DC converter configured to convert the DC power that is received from the vehicle power system when the vehicle power adapter is inserted into the cigarette lighter socket to a selected DC signal, and the coaxial cable is configured to deliver the selected DC signal to the external device.
3. A vehicle power adapter as claimed in claim 2 , wherein the coaxial cable is configured to carry the selected DC signal to the external device while carrying the FM signals from the external device to the main body.
4. A vehicle power adapter as claimed in claim 2 , wherein the DC to DC converter comprises filters to reject stray FM radiation.
5. A vehicle power adapter as claimed in claim 1 , further comprising an attenuator circuit configured to attenuate the FM signals received from the external device to a selected level that complies with at least one of Federal Communications Commission Part 15 and regulatory limits for an intentional radiator.
6. A vehicle power adapter as claimed in claim 1 , wherein the amplifier circuit is configured to provide matched impedance to the coaxial cable, amplify the FM signals from signal loss due to the coaxial cable, and provide isolation to the cigarette lighter socket from unwanted signal reflection that could cause unwanted radiation of the FM signals.
7. A vehicle power adapter as claimed in claim 1 , wherein the main body consists of a unitary housing enclosing the amplifier.
8. A vehicle power adapter as claimed in claim 1 , wherein the main body is configured to provide the amplified FM signals to the vehicle's existing and unmodified wiring system for output by the FM receiver in the vehicle without additional components or modifications to the vehicle's wiring.
9. A method for providing frequency modulated (FM) radio frequency signals from an external device to an FM receiver in a vehicle via a vehicle power adapter using the vehicle's existing wiring system without modification of the vehicle's electrical connections behind the vehicle's dashboard and without over-the-air transmission of the FM signals, the method comprising: receiving direct current (DC) power from the vehicle power system at a main body inserted into a cigarette lighter socket of the vehicle; receiving the FM signals from the external device at the main body via a coaxial cable having a first end connected to the main body and a second end configured to be at least detachably connected to the external device; amplifying the FM signals at the main body to a selected signal level that allows for their transmission to the FM receiver in the vehicle via the vehicle's existing and unmodified wiring system for reception and playback by the FM receiver; and providing the amplified FM signals to the vehicle's existing and unmodified wiring system when the main body is inserted into the vehicle cigarette lighter socket.
10. A method as claimed in claim 9 , further comprises:
converting the DC power that is received from the vehicle power system when the main body is inserted into the cigarette lighter socket to a selected DC signal; and
providing the selected DC signal to the external device.
11. A method as claimed in claim 10 , wherein said receiving the FM signals and said providing the selected DC signal are performed using the same coaxial cable.
12. A method as claimed in claim 11 , wherein the coaxial cable is configured to carry the selected DC signal to the external device while carrying the FM signals from the external device to the main body.
13. A method as claimed in claim 9 , further comprising containing the FM signals within the coaxial cable using shielding provided by the coaxial cable.
14. A method as claimed in claim 9 , further comprising: providing matched impedance to the coaxial cable; amplifying the FM signals from signal loss due to the coaxial cable; and providing isolation to the cigarette lighter socket from unwanted signal reflection that could cause unwanted radiation of the FM signals.
15. A method as claimed in claim 9 , further comprising attenuating the FM signals received in the main body from the external device to a selected level that complies with at least one of Federal Communications Commission Part 15 and regulatory limits for an intentional radiator.