Patent 3573628 - ANTENNA FOR MINIATURE RADIO RECEIVER INCLUDING PORTIONS OF RECEIVER HOUSING AND CHASSIS
|United States Patent||Patent Number 3,573,628|
|Cramer, Jr. , et al.||Issued April 6, 1971|
ANTENNA FOR MINIATURE RADIO RECEIVER INCLUDING PORTIONS OF RECEIVER HOUSING AND CHASSIS
Antenna for radio receiver of the capacitively loaded vertical ground plane type wherein an active vertical portion is formed by parts of the receiver and is connected to a conductive escutcheon to form a capacitive loading structure for the vertical antenna. The lower end of the vertical antenna is connected to shield cans and grounded conductors on the chassis which form an effective ground plane. The signal from the top of the vertical antenna is coupled through a matching circuit to the base of a transistor. A jack for connecting an external antenna is connected between the ground plane and a point on the vertical antenna.
|Inventors:||Jr Joseph F Cramer (Downers Grove IL)|
Thomas M Yackish (Hammond IN)
|Assignee:||Motorola, Inc. (Franklin Park, IL)|
|Filed:||July 15, 1968|
|Current U.S. Class:||455/269 - 343/702 - 455/301 - 455/351|
|Current CPC Class:||H01Q 1/243 (20130101)|
|Current International Class:||H01Q01/24 (20060101)|
|Field of Search:||;343/702 ;325/119,354,365,361|
Assistant Examiner:Anthony H Handal
1. An antenna for a miniature radio device having an insulating housing with a part thereon formed of conductive material, and having a chassis within the housing with conducting means at a reference potential, such antenna including conductor means extending vertically within the housing when the radio device is in the position of use to form an active antenna element, first conductive means connecting the upper end of said conductor means to the conductive part of the housing and forming therewith a capacitor for loading said antenna element, and second conductive means connecting the lower end of said conductor means to the conducting means of the chassis to form an effective ground plane for said antenna element.
2. The antenna of claim 1 wherein said conductor means is formed of a plurality of parts, at least one of which has a further function in the radio device.
3. The antenna of claim 1 including conducting shield cans on the chassis which form at least a part of the ground plane for said antenna element.
4. A miniature radio receiver including in combination, an insulating housing having an escutcheon thereon formed of conductive material, a chassis within the housing with conducting means at a reference potential, conductor means on said chassis extending vertically within the housing when the receiver is in the position of use to form an active antenna element, first conductive means connecting the upper end of said conductor means to said escutcheon and forming therewith a capacitor for loading said antenna element, and second conductive means connecting the lower end of said conductor means to said conducting means of said chassis to form an effective ground plane for said antenna element.
5. The structure of claim 4 including a conductive bracket which forms a part of said conductor means and which has a portion in electrical connection with said escutcheon.
6. The structure of claim 5 wherein said bracket supports a jack for connecting an external antenna to the receiver, and said jack has a first connector connected to said conductor means and a second connector connected to said second conductive means.
7. The structure of claim 4 wherein said escutcheon includes a conductive finger, and wherein said conductor means and said first conductive means are formed in part by a conductive bracket having a portion engaging said conductive finger.
8. The structure of claim 4 including a transistor forming the first stage of the receiver, and a matching circuit connected from said first conductive means to said transistor for applying signals thereto.
9. The structure of claim 8 wherein said transistor has base, emitter and collector electrodes and said matching circuit is connected to said base electrode, and including means connecting said emitter electrode to said second conductive means, and tuned circuit means connected between said collector electrode and said second conductive means.
10. The structure of claim 9 including conductive shield cans on said chassis which form at least a part of the ground plane, and wherein said transistor and said tuned circuit means are provided in one of said shield cans.
BACKGROUND OF THE INVENTION
In small radio receivers and transmitters which may be carried in the hand, a problem has existed in providing a satisfactory antenna for picking up or radiating signals. Ferrite antennas have been used for receivers operating in the broadcast and VHF bands, but these are not satisfactory for ultrahigh frequency use. Vertical rod antennas have been used, but these are objectionable in that they protrude from the receiver and may unintentionally engage some object. They are also subject to breaking. In some miniature radio units an antenna has been provided in a cord extending from the unit, such as a cord connecting a microphone to a transmitter, or an earpiece to a receiver. However, in many cases such a projecting cord is not needed or desired, and this arrangement cannot therefore be used.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an antenna for a radio device which is formed as an integral part of the housing and chassis of the device.
Another object of the invention is to provide an antenna for an ultrahigh frequency radio receiver which is entirely self-contained and has no protruding parts.
A further object of the invention is to provide an antenna for a miniature radio receiver by providing cooperation between parts having other functions in the receiver so that the cost of the antenna is a minimum.
The antenna of the invention is formed by a conductive escutcheon plate of the housing of the radio unit, a conductive bracket for jack connectors, and parts of the chassis of the unit including shield cans. The antenna acts as a capacitively loaded vertical antenna with the vertical section being formed by a portion of the bracket, conducting material on the chassis and a strap connected to a shield can. The capacitive loading structure is formed by part of the bracket and the escutcheon plate which includes a finger engaging the bracket. The ground plane is formed by the shield cans and the ground conductors on the chassis. When used in a receiver, signal is derived from the top of the vertical antenna section by a connection from the bracket through a matching network to the base of a transistor. The transistor is provided in one of the shield cans and has its collector connected to a coil therein which is coupled to other coils which provide the radio frequency selectivity for the receiver.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view of a radio receiver incorporating the antenna of the invention;
FIG. 2 is a perspective view partly broken away of the parts of the receiver forming the antenna;
FIG. 3 is a cross-sectional view showing the parts of the receiver forming the antenna; and
FIG. 4 is a view similar to FIG. 3 showing the circuit connected to the antenna in schematic form.
DETAILED DESCRIPTION OF THE EMBODIMENT ILLUSTRATED
In FIG. 1 there is shown the portable receiver 10 which may be a paging receiver to be carried by a person so that he can receive messages. Such a paging receiver can be used over a limited area, such as in a city, or within a building or complex of buildings. The receiver has an insulating housing including a louvered section 11 behind which a loud speaker 17 (FIG. 3) is mounted for producing tone and/or voice signals. At the top of the housing is a metal escutcheon plate 12 which has a first right angle portion extending across the top of the receiver and a second portion extending downwardly to the top of the louvered section 11. Jacks 13 and 14 are provided at the top of the receiver for connection of an external antenna and an external earpiece, respectively. The escutcheon plate 12 has openings through which the jacks extend. A thumb operated control 15 operates a switch to turn on the receiver and also a volume control to control the level of the sound reproduced. A second push operated switch 16 may be used to provide a further operation. In some paging receivers a signalling tone is first received and the switch button 16 must be pressed and held to hear a voice message. In other units the voice message is heard automatically following the tones, and the switch button 16 may be used to reset the receiver for response to another tone code.
FIG. 2 shows portions of the receiver with the housing not shown. The conducting escutcheon plate 12 is shown and this includes an integral upwardly turned finger 20 which is engaged by the edge of a conducting bracket 22 which supports the jacks 13 and 14. The bracket 22 is riveted to the chassis 24, which may be formed by an insulating printed circuit board, by conducting rivets 25. The chassis 24 has conducting coatings 26 and 27 on the rear thereof, with the coating 27 including electrical ground connections between various parts mounted on the chassis. Some of these parts are provided in the conducting shield cans 28 and 29 which extend from the top side of the chassis 24. A conducting strap 30 is electrically connected to the coating 26, which is in turn connected to the bracket 22 by rivets 25. The strap 30 has an angle portion electrically connected to the shield can 28.
The vertical portion of the bracket 22 together with the conducting coating 26 on the backside of the chassis and the vertical portion of the strap 30 form a vertical antenna. The conducting rivets 25 electrically connect the bracket 22 to the coating 26 and the strap 30 is soldered to the coating 26. The bottom end of the vertical antenna is connected to the ground plane formed by the shield cans 28 and 29 and also by the conducting coating 27 which extends on the insulating chassis 24 below the shield cans. These conducting portions form an effective ground plane for the antenna. The horizontal top portion of the bracket 22 in cooperation with the metal escutcheon 12 and the connecting finger 20 form a capacitor which loads the upper end of the vertical antenna. As shown in FIG. 3, a resilient pad 21 is provided back of the finger 20 to apply pressure thereto so that the finger 20 presses against the edge of the bracket 22. When the chassis is placed within the housing, the edge of the bracket wipes against the finger 20. This provides a good electrical connection between the bracket and the escutcheon.
FIGS. 3 and 4 show the electrical connections from the antenna to the receiver. Connection is made from the upper horizontal portion of the bracket 22 through the coil 32 and variable capacitor 34 to the base of transistor 35. The coil and capacitor are shown physically in FIG. 3 and a schematic diagram of these elements and the transistor is shown in FIG. 4. As indicated by FIG. 4, the transistor 35 is in the shield can 28 along with the coil 36 connected to the collector of transistor 35. The emitter of transistor 35 is connected to ground through the chassis. Coil 36 is part of a tuned output circuit including capacitor 37 and capacitor 38. Capacitor 38 isolates the coil 36 from ground for direct current so that the bias potential for the collector of transistor 35 can be applied through this coil. The bias potential is applied at terminal 40 which is bypassed by capacitor 41. The potential is applied through a voltage divider including resistors 42, 43 and 44, with the voltage across resistor 44 being applied to the base electrode of transistor 35, and the voltage across resistors 43 and 44 being applied through coils 45 and 36 to the collector electrode. Capacitor 47 and resistor 48 provide feedback from the tuned output circuit to the base electrode. The coil 36 of the tuned circuit may be coupled to other tuned circuits to provide the radio frequency selectivity of the receiver.
As shown in FIG. 4, the jack for receiving a plug connected to an external antenna has a connector 50 connected to the shield can 28 (ground) and a connector 51 connected to the rivet 25. The input from the external antenna is therefore connected to a tap on the vertical antenna element to match the impedance of the external antenna to the antenna formed by the receiver components.
The receiver circuit may include a selective calling system which responds to a code including particular frequencies. These frequencies are selected by reed devices 55 (FIG. 2).
The receiver as illustrated in FIG. 1 of the drawing, has the following dimensions; 21/2 inches wide, 51/4 inches high and 1 1/16 inches thick. The weight of the receiver including a battery which is positioned at the bottom of the housing is between 11 and 12 ounces, depending on the particular battery used. The escutcheon is approximately 21/8 inches long with the top portion having a width of about three-fourths of an inch and the front portion having a width of about one-half of an inch. The length of the active vertical antenna element is approximately three-eights of an inch.
The antenna as described has been found to be highly effective to pick up signals under various different operating conditions. Since it is formed by parts having other functions in the receiver, it is provided at very low cost.
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