Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2001-10-19
2004-02-03
Clinger, James (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S715000, C343S713000
Reexamination Certificate
active
06686882
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to transmission of radio frequency signals (e.g., SDARS signals) from an antenna across a dielectric such as glass to a receiver disposed in a vehicle, as well as the transmission across glass of power from the receiver to antenna electronics. The invention also relates to an antenna system having DC and RF coupling across a dielectric which uses a relatively low supply voltage and low loss circuit boards and patch arrangement for optimal RF coupling.
BACKGROUND OF THE INVENTION
With reference to
FIG. 1
, a number of antenna systems have been proposed which provide for the transfer of radio frequency (RF) energy through glass or other dielectric surface to avoid having to drill holes, for example, through the windshield or window of an automobile for installation. Glass-mount antenna systems ate advantageous because they obviate the necessity of having to provide a proper seal around an installation hole or other window opening in order to protect the interior of the vehicle and its occupants from exposure to external weather conditions.
In the conventional antenna system
20
depicted in
FIG. 1
, RF signals from an antenna
22
are conducted across a glass surface
24
via a coupling device
26
that typically employs capacitive coupling, slot coupling or aperture coupling. The portion of the coupling device
26
on the interior of the vehicle is connected to a matching circuit
28
which provides the RF signals to a low noise amplifier (LNA)
32
at the input of a receiver
34
via an RF or coaxial cable
30
. The matching circuit
28
can comprise passive components or traces on a circuit board, for example. The antenna system
20
is disadvantageous because the matching circuit
28
, losses associated with the cable
30
and RF coupling (e.g., on the order of 2 to 4 dB or more) cause an increase in system noise. RF coupling losses increase as frequency increases. To reduce coupling losses, a conventional antenna system
20
is preferably implemented using ceramic compositions for circuit boards that are relatively expensive (e.g., Rogers 3003, 4003, 3010, and the like available from Rogers Corporation, Chandler, Ariz.). The cost associated with using these types of materials is 5 times that of a standard FR4 circuit board. A need therefore exists for an antenna system that achieves low RF coupling loss using low cost circuit boards.
Another proposed antenna system
40
, which is described with reference to
FIG. 2
, has an RF coupling device similar to that used in the antenna system
20
depicted in
FIG. 1
, as well as DC coupling components to provide power to the antenna electronic circuitry. The antenna system
40
is configured to transmit video signals from satellite antenna electronics through a glass window
46
into a structure such as a residence or office building without requiring a hole through the glass. An exterior module
42
is mounted, for example, on the exterior of the structure, while an interior module
44
and receiver
48
are provided within the structure. RF coupling units
50
a
and
50
b
are provided on opposite sides of the glass
46
which is typically a window in the building. RF coupling unit
50
b
is connected to the exterior module
42
via a coaxial cable
54
to allow the exterior module
42
to be located remotely therefrom (e.g., on the building rooftop). The exterior module
42
encloses an antenna
52
and associated electronics (e.g., an LNA
56
) to receive RF signals, which are then provided from the LNA
56
to the coupling device
50
b
via the cable
54
for transfer through the glass
46
.
With continued reference to
FIG. 2
, RF energy transferred through the glass
46
is processed via a matching circuit
58
. The matching circuit
28
is connected to a receiver
48
by another coaxial cable
60
. In addition, DC power is provided from the interior module
44
to the exterior module
42
(e.g., to provide power for the LNA
48
) by low frequency coupling coils
62
a
and
62
b
mounted opposite each other on either side of the glass
46
. In a conventional satellite TV system, electrical power for the satellite antenna electronics is provided from the receiver
48
on the same coaxial cable that provides video signals from the antenna
52
to the receiver
48
.
While the provision of DC power to antenna electronics is useful, the matching circuit and cable losses associated with the antenna system
40
are not desirable for such applications as a Satellite Digital Audio Radio Services (SDARS) system antenna for a vehicle. At 800 MHz, the coupling loss experienced with conventional glass mount antenna arrangements can be as much as 3 dB. At higher frequencies, the coupling loss increases substantially. For such high frequency applications as satellite radio operating at 2.4 GHz, the coupling loss is expected to be unacceptably high (e.g., 2 to 4 dB), making reception difficult. A need therefore exists for a glass or other dielectric-mounted antenna arrangement for high frequency wireless communication applications, and particularly, satellite radio applications, that reduces coupling loss and that is also compact.
Further, noise temperature is a significant parameter in an antenna system such as one that receives a satellite signal which is then amplified by an LNA. The noise temperature needs to be as low as possible. A need therefore exists for an antenna system that achieves that transfer of DC power across a dielectric (e.g., from the inside to the outside of a vehicle through the windshield) without significant degradation on system noise temperature.
SUMMARY OF THE INVENTION
The above described disadvantages are overcome and a number of advantages ate realized by an antenna system whereby RF coupling devices for mounting on opposite sides of a dielectric are made of low cost and low loss materials, and the transfer of RF energy across the dielectric occurs without significant degradation due to increased system noise.
The RF coupling devices ate also compact in design. Quarterwave patches are mounted on a circuit board and attached to a dielectric such that the patch is against the dielectric. The patch is provided with one or mote feeds, depending on the number of RF signals to be processed.
In accordance with another aspect of the present invention, the antenna system achieves DC coupling across the dielectric even though the supply voltage (e.g., the voltage supplied from a tuner to an antenna module located on the opposite side of a dielectric) is relatively low (e.g., 5 volts, as opposed to between 12 and 18 volts).
In accordance with an embodiment of the present invention, a DC voltage supplied on one side of a dielectric is increased to a higher voltage and then converted to an AC voltage to transfer electrical power across a dielectric via magnetic inductance.
In accordance with another aspect of the present invention, the DC coupling is not enabled until the interior antenna assembly is connected to the receiver and the receiver is powered on.
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patent:
Nguyen Anh
Petros Argy A.
Clinger James
Roylance Abrams Berdo & Goodman LLP
XM Satellite Radio Inc.
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