Small, battery operated RF transmitter for portable audio devices for use with headphones with RF receiver
Patent 5771441 Issued on June 23, 1998. Estimated Expiration Date: 
April 10, 2016. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
April 10, 2016. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesInventorApplicationNo. 630502 filed on 04/10/1996US Classes:455/66.1, Having diverse art device343/718, Body-attached or connected343/720, Combined with diverse-type art device381/14, Having transmitter381/309, Stereo earphone455/67.11, Having measuring, testing, or monitoring of system or part455/67.12, Using a chamber (e.g., room testing or audio surveillance, etc.)455/67.13, Noise, distortion, or unwanted signal detection (e.g., quality control, etc.)455/95, Mobile or portable455/129With coupled antennaExaminersPrimary: Urban, Edward F.Assistant: Sobutka, Philip J. Attorney, Agent or FirmInternational ClassH04B 001/034AbstractA portable RF transmitter having an audio plug extending therefrom which mates with the earphone or output jack of an audio source such as a portable battery operated CD or tape player and having no external antenna. The portable RF transmitter modulates audio signals from the audio source onto an FM carrier and transmits them to an FM receiver mounted on a headset worn by a user. The RF transmitter uses its own ground circuit and the ground circuit of the audio source as two elements of a short dipole. The two ground circuits are electrically isolated at RF by an RF choke but connected together at audio frequencies by the low impedance of the choke at audio. The choke's leakage inductance also reduces the capacitive reactance of the dipole antenna for better power dissipation. A transformer coupling the RF output to the dipole transforms the impedance of the dipole to a value closer to the output impedance of the RF transmitter.Field of SearchWith coupled antennaTRANSMITTER Mobile or portable Body attached or connected With variation of antenna impedance or dimension for modulation With wave collector (e.g., antenna) Power-line or receiver element used as wave collector With coupling to a stage of the receiver Transmission line Wave filter, coil, or wave trap Single antenna switched between transmitter and receiver Base station selection Body-attached or connected Combined with diverse-type art device HEADPHONE CIRCUITS VEHICLE Having transmitter Crystal | |
