U.S. patent number 3,718,862 [Application Number 04/837,809] was granted by the patent office on 1973-02-27 for wireless microphone and adapter kit.
This patent grant is currently assigned to Sound Systems International, Inc.. Invention is credited to Elwood G. Norris.
United States Patent |
3,718,862 |
Norris |
February 27, 1973 |
WIRELESS MICROPHONE AND ADAPTER KIT
Abstract
A wireless microphone assembly is disclosed which uses a
frequency modulated transmitter having improved radiation
characteristics and eliminates the need for a separate external
antenna. An adapter unit is disclosed as being connectable to a
conventional microphone with the adapter unit including a
transmitting oscillator having its input circuit coupled with the
conventional microphone output circuit via plug connectors and with
the output circuit of the frequency modulated oscillator being
connected via a grounding terminal to the case of the conventional
microphone. The case of the conventional microphone then acts as a
radiating antenna giving rise to high strength signals without the
need for any protruding antenna arrangements. Mechanical
construction details as well as schematic circuit diagrams are
provided.
Inventors: |
Norris; Elwood G. (Seattle,
WA) |
Assignee: |
Sound Systems International,
Inc. (Seattle, WA)
|
Family
ID: |
25275494 |
Appl.
No.: |
04/837,809 |
Filed: |
June 30, 1969 |
Current U.S.
Class: |
455/95;
455/117 |
Current CPC
Class: |
H04B
5/06 (20130101); H04R 1/08 (20130101); H04R
2420/07 (20130101) |
Current International
Class: |
H04B
5/06 (20060101); H04B 5/00 (20060101); H04R
1/08 (20060101); H04b 001/02 () |
Field of
Search: |
;325/105,111,118,119,150
;179/41A,82 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Phinney, "Vagabond Wireless Microphone System," Tele-Tech and
Electronic Industries, March, 1954 p. 86t..
|
Primary Examiner: Griffin; Robert L.
Assistant Examiner: Leibowitz; Barry L.
Claims
What is claimed is:
1. A hand-held portable microphone assembly comprising in
combination:
a. a conventional microphone unit including a transducer element
having electric circuit means connected thereto; a housing member
having said element disposed therein, and including means defining
a radio frequency antenna, said housing member being a metal
microphone case having an electrical ground lead connected thereto
with the case serving as the antenna means; and
b. an adapter unit for said conventional microphone unit including
a radio frequency transmitter having said electric circuit means
connected thereto as an input circuit, a second housing member
having said transmitter disposed therein means insulating said
second housing member from said metal microphone case and means
connecting the output circuit of the transmitter to said ground
lead and to said second housing member, whereby said metal
microphone case and said second housing member act as the antenna
for said transmitter.
2. The apparatus of claim 1 including a first electrical connector
assembly secured to said housing and a second connector assembly
connected to said second housing member, said first and second
connector assemblies being a matching pair and adapted for
connection and disconnection.
3. The apparatus of claim 1 wherein said transmitter is a frequency
modulated transmitter.
4. The apparatus of claim 1 including first and second inductors
connected in the input circuit of said transmitter, each of said
inductors being connected in series between said transducer element
and said transmitter to substantially block radio frequency signals
but pass audio frequency signals.
5. An adapter unit for converting a conventional hand-held
microphone unit having a metal case and a transducer therein and a
connector assembly including a pair of output leads connected to
said transducer and a lead connected to the metal case, into a
portable wireless microphone transmitter comprising: a housing
member, a radio frequency transmitter disposed within said housing
member having first and second signal input leads, a signal
transmission output lead, and a ground lead connected to said
housing member; and an electrical connector assembly having said
each of said three leads connected thereto and arranged for
connection to the connector assembly of the microphone unit with
said output lead connected to the lead in the microphone unit which
is connected to the metal case and said first and second signal
input leads connected to said pair of output leads, said electrical
connector assembly further including means insulating said housing
member from said metal case.
6. The apparatus of claim 5 including circuit means in the input
circuit of said transmitter blocking radio frequency input signals
and passing audio frequency signals.
7. The apparatus of claim 6 wherein said circuit means includes
first and second inductors connected to said input leads.
Description
At the present time microphone units of the "wireless" type are
available. In general such units include a frequency modulated
transmitter together with some sort of protruding antenna in
combination with a pickup unit. The transmitter output is modulated
in a conventional manner by the voice or other sound input to the
pickup unit. The use of a protruding antenna gives rise to an
unwieldy unit from the standpoint of appearance and use.
It is an object of the present invention to provide a low cost
wireless microphone unit having increased radiating strength while
requiring lower input power than is required by presently available
units. Another object of the present invention is to provide a low
cost adapter unit for converting conventional wire-type microphones
to a wireless microphone assembly.
Another object of the present invention is to provide a wireless
microphone assembly wherein the body of the microphone pickup unit
is made of metal and acts as the radiating antenna for radiation of
modulated signals to an associated receiver. Another object is to
provide a novel electronic circuit for use in a wireless
microphone.
The above as well as other advantages of the invention are achieved
through the use of a compact frequency modulated oscillator which
is plugged into the base of a conventional microphone for the
receipt of audio signals from the conventional microphone. Most
microphones presently in use are provided with a plug-in connector
assembly for coupling the lead wires of the microphone to an
amplifier in a quick disconnect arrangement. The adapter unit of
the present invention couples with the conventional plugs of most
microphones and then makes use of the ground connection of the
microphone as the output lead of the radiating oscillator. Since
most microphones have the metallic cases thereof electrically
grounded via a ground connector output the present adapter unit
utilizes the ground connection of the microphone as the output
circuit of the radiating oscillator. As a result the entire case of
a conventional microphone serves as an antenna and high strength
radiating characteristics are achieved even though the output power
applied is very low. The output circuit of the radiating oscillator
is heavily loaded from an electrical standpoint so that shorting of
the output circuit has little or no effect on the field strength of
the radiated signal. The input circuit to the oscillator includes
an inductor which presents a high impedance to the r.f. signal to
be transmitted but passes the audio input signals. As a result a
highly efficient wireless microphone is provided with the power
requirements being extremely low.
The invention will be more clearly understood from the following
description when read with reference to the accompanying
drawings.
FIG. 1 is a perspective view of a preferred embodiment of the
wireless microphone assembly of the present invention.
FIG. 2 is a perspective view of the adapter unit containing the
electronics package together with the connector end of the pickup
unit.
FIG. 3 is an end view of the input jack assembly for the microphone
pickup unit and of the jack assembly for the microphone pickup unit
and of the jack assembly for the adapter unit.
FIG. 4 is an exploded view of the components contained inside the
housing of the adapter unit.
FIG. 5 is a schematic circuit diagram of the circuitry for a
preferred embodiment of the invention.
Turning now to the drawings, there is illustrated in FIG. 1 a
wireless microphone including a conventional pickup unit 10 having
a base connector 11 connected to the adapter unit 12 which houses
the r.f. transmitter assembly. The base 11 of the pickup unit 10
will be seen in FIGS. 2 and 3 to have three bayonet-type connectors
14, 15 and 16. The base of the unit 10 can have either the male or
female connectors units, but since many presently available
microphones use male connectors the unit of FIGS. 1, 2 and 3 has
male connectors. In a typical wiretype microphone assembly the wire
connector 14 serves as a ground connector which is electrically
connected to the case 10A of the microphone. This is shown by the
lead 17 in FIG. 2. Connectors 15 and 16 are connected to the
microphone element 27 (FIG. 5) for providing the output signals to
the oscillator described below. These three connector pins 14, 15
and 16 are typically plugged into a cable via a mating jack
assembly for grounding the microphone housing 10A for providing
signals to an amplifier.
In accordance with the present invention the adapter unit 12 is
provided with the female connector members 18, 19 and 20 which are
respectively adapted to receive the male connectors 14, 15 and 16.
An insulating collar 21 supports the jack receptacles 18, 19 and 20
and is of a length such that when the adapter and pickup units are
assembled in the manner indicated in FIG. 1, the adapter unit 12 is
electrically insulated from the metal case 10A of the pickup unit.
A small set screw 23 enters the insulating member 21 and holds it
in position inside the case of the adapter unit 12. In practice the
case 12A of the adapter unit is an elongated cylindrical member
similar to a length of metal tubing. The insulating collar member
21 is provided with an elongated support section 21A which serves
to support the electronic circuitry 22 illustrated in FIG. 5. A
battery 23 has its positive terminal at its end 23A for engagement
with the circuitry 22 and its negative terminal connected via the
switch 24 to the metal casing 12A of the adapter unit.
Turning now to FIG. 5 the details of one embodiment of the
invention found to work well will be described. As seen in FIG. 5,
terminal 16 of the pickup unit connects with terminal 20 of the
modulation and transmitter unit so that input signals are applied
via inductor 25 and capacitor 30 to the base of the preamplifier
transistor 31. Signals from the preamp are coupled by capacitor 32
to the base of the frequency modulated oscillator circuit which
includes the transistor 33. The L-C tank circuit 34 determines the
frequency of the oscillator with capacitor 35 being adjustable for
frequency selection. A bias circuit composed of resistors 36 and 37
provides the usual bias for transistor 33. Frequency modulated
signals are provided via capacitor 39 to the r.f. amplifier which
includes transistor 40 having the low Q inductor 41 in the
collector thereof. Adjustable capacitor 42 connected to the
collector of transistor 40 together with the output capacitor 43
and the low Q inductor 44 connected to output pin 18 form part of a
pi network which is tuned by capacitor 42.
The circuit shown in FIG. 5 operates in the conventional manner so
that a frequency modulated r.f. signal is applied via output
terminal 18 to the input terminal 14 of the pickup unit 10. Since
the terminal 14 of the pickup unit 10 is electrically connected to
the metal frame 10A of the pickup unit 10 it will be seen that the
entire frame or housing 10A acts as a radiating antenna. The output
of the r.f. amplifier is heavily loaded so that shorting of the
case 10A to the case 12A does not prevent proper circuit operation.
The capacitor 43 provides D.C. isolation and thus prevents damage
to the output transistor 40. An inductor 45 connected to the input
terminal 19 and the inductor 25 connected to terminal 20 act as
high impedances to any r.f. signals which would otherwise be
capacitively coupled from the case 10A (which acts as the antenna)
to the leads 47 and 48 extending from the microphone element 27 to
the pins 15 and 16. In one system the output frequency was
approximately 90 megahertz with inductors 25 and 45 having been 1
millihenry.
It will be seen that the present invention provides not only a
composite wireless microphone but also a removable adapter unit
which is suited for use with virtually all presently available
standard wire-type microphones. The particular jack configuration
for the standard microphones might vary but in general it has been
found that standard microphones typically include a lead which is
electrically connected to the metal frame of the pickup unit
together with a pair of power leads for the pickup unit itself.
Thus it is only necessary to provide a different physical
configuration for the jack connection of the adapter unit to
utilize the illustrated electronic circuitry for virtually all
conventional microphones. From a practical standpoint this is of
extreme importance since a person or organization already having
standard wire-type microphones need only purchase the adapter unit
and a low cost frequency modulated tuner for receiving the FM
output signals radiated from the microphone housing 10A.
The invention has been disclosed by reference to the presently
preferred embodiment. The inventive concepts lend themselves well
to modifications and adaptations which will be obvious to a person
skilled in the art.
* * * * *