Ferrite-core antenna
First Claim
1. A tuned antenna for use in connection with a radio receiver for receiving an electromagnetic signal at a certain frequency, said antenna comprising an elongated ferromagnetic core having a longitudinal axis, a first coil comprising a predetermined number of turns of electrically conductive material disposed around said core, said first coil having a pair of terminals connected to a shunt capacitance, said shunt capacitance resonating with the inductance of said first coil at said frequency, and a second coil of electrically conductive material disposed around said core, wherein said second coil has a plurality of turns in excess of the number of turns of said first coil for connection to an input to said radio receiver.
1 Assignment
0 Petitions
Accused Products
Abstract
A ferrite core antenna for use in the VHF and UHF range has a first coil on the core which is connected to a capacitance selected to resonate with the inductance of the coil at the desired frequency of operation. The ferrite core antenna also has a second coil for providing a signal to the input stage of a radio receiver. In contrast to conventional loopstick antennas for low frequencies, the operation of the ferrite core antenna in the VHF to UHF range is remarkably improved by using an input stage having a relatively high input impedance and using a greater number of turns in the second coil than the first which is tuned instead of the second. Preferably the first coil is centrally disposed and has a single turn in the form of a relatively wide band of conductive metal foil, and the second coil is offset by a certain distance from the first coil and feeds an input signal to the gate of a gallium arsenide field-effect transistor. For operation in the FM broadcast band, the ferrite core preferably has dimensions of 7 cm×1 cm×1.5 cm, and the second coil has about three turns. So that the first coil has a sufficiently high Q, the capacitance for resonating the first coil is provided by a number of capacitors connected in parallel.
-
Citations
20 Claims
- 1. A tuned antenna for use in connection with a radio receiver for receiving an electromagnetic signal at a certain frequency, said antenna comprising an elongated ferromagnetic core having a longitudinal axis, a first coil comprising a predetermined number of turns of electrically conductive material disposed around said core, said first coil having a pair of terminals connected to a shunt capacitance, said shunt capacitance resonating with the inductance of said first coil at said frequency, and a second coil of electrically conductive material disposed around said core, wherein said second coil has a plurality of turns in excess of the number of turns of said first coil for connection to an input to said radio receiver.
-
8. A radio receiver including an antenna for receiving an electromagnetic signal at a certain frequency, and an input stage having a field-effect transistor, wherein said antenna converts said electromagnetic signal to a corresponding electrical signal applied to a relatively high impedance gate terminal of said field-effect transistor, said antenna has an elongated ferrite core having a longitudinal axis and a first coil comprising a predetermined number of turns of electrically conductive material disposed around said core, said first coil;
- has a pair of terminals connected to a shunt capacitance, said shunt capacitance resonates with the inductance of said first coil at said frequency, said antenna has a second coil of electrically conductive material disposed around said core, and wherein said second coil has a plurality of turns in excess of the number of turns of said first coil, and said second coil is connected to said gate terminal of said field-effect transistor.
- View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
- 16. A radio receiver comprising an enclosure, a compact antenna within said enclosure for receiving an electromagnetic signal at a certain frequency in the VHF to UHF range, and an input stage including a gallium arsenide field-effect transistor, wherein said antenna has an elongated ferrite core having a longitudinal axis, said antenna has a first coil including a single turn of conductive metal foil in the form of a band disposed at a central location about said core, said first coil has a pair of terminals connected to a shunt capacitance which resonates with the inductance of said first coil at said frequency, said antenna has a second coil of electrically conductive material disposed around said core, and wherein said second coil has a plurality of turns and is connected to a gate terminal of said field-effect transistor.
Specification