Headphone receiver apparatus for use with low power transmitters
View Patent ↗A headphone receiver apparatus for use with low power transmitters includes a pair of headphone speaker enclosures connected by a headband. An antenna element in the form of a spring steel band or a plastic cable/antenna band where one of the conductors is utilized as the antenna is configured generally concentric with but offset from the headband and the user's head by at least 0.5 inches over at least some length of the antenna. Low-noise performance is improved by a low noise amplifier incorporated before the receiver IC, and a bandpass filter interposed between the low noise amplifier and the receiver IC. A base-loading inductor is used to tune the antenna element to resonance, with or without capacative end-loading. Lumped inductors, ferrite beads, or a parallel resonant LC circuit may be used to isolate the shield conductor at RF frequencies, and/or to reduce the loading of the other conductors.
1. A headphone receiver apparatus for use with low power transmitters, said apparatus comprising: a pair of headphone speaker enclosures connected by a headband; receiver electronics contained in one of said enclosures; an antenna element generally concentric with but radially offset from said headband, said antenna element disposed between and connected to each of the speaker enclosures in said pair of head phone speaker enclosures and positioned such that a spacing from the user's head of at least 0.5 inches is maintained over substantially all of the length of said antenna element; wherein said receiver electronics includes a receiver integrated circuit (IC), further including a low noise amplifier connected to said receiver IC and a lumped-element band pass filter interposed between said antenna element and said low noise amplifier so as to minimize the level of other strong inband signals presented to the low noise amplifier, thereby minimizing intermodulation products.
2. The headphone receiver apparatus of claim 1 wherein said antenna element comprises a spring steel band.
3. The headphone receiver apparatus of claim 1 wherein said antenna element comprises a plastic cable/antenna band where one of the conductors is utilized as an antenna conductor.
4. The headphone receiver apparatus of claim 3 wherein said antenna conductor is isolated to reduce loading from other nearby conductors at RF frequencies by series lumped inductors.
5. The headphone receiver apparatus of claim 3 wherein said antenna conductor is isolated to reduce loading from other nearby conductors at RF frequencies by series ferrite beads.
6. The headphone receiver apparatus of claim 3 wherein said antenna conductor is isolated to reduce loading from other nearby conductors at RF frequencies by series parallel resonant LC circuit.
7. The headphone receiver apparatus of claim 1 further including a varactor-tuned bandpass filter interposed between said low noise amplifier and said receiver IC.
8. The headphone receiver apparatus of claim 1 further including a base-loading inductor to tune said antenna element to resonance.
9. The headphone receiver apparatus of claim 1 wherein said antenna element includes capacitive end-loading.