Capacitively coupled patch antenna
Systems and methods relating to patch antennas and signal combiner circuits. The invention relates to a circuit with discrete capacitors, inductors and amplifiers arrayed in an arrangement with 2 input ports and one output port. The circuit provides a high degree of reverse electrical isolation between the input ports and the output at the radio frequency. The circuit provides an output that is the vector sum of signals present at the first and second input ports. The circuit additionally provides for introduction of a 90 degree phase shift into either of the two inputs. This circuit can be used with dual feed patch antennas.
1. A circuit for use in combining signals for an antenna, the circuit comprising:
a first amplifier receiving a first signal feed from said antenna;
a second amplifier receiving a second signal feed from said antenna;
a common combining node;
a capacitor coupled between said first amplifier output and said common combining node;
an inductor coupled between said second amplifier output and said common combining node;
wherein said first and second amplifiers are matched amplifiers, and wherein said antenna comprises:
a resonant metal plate;
a ground plate;
a dielectric substrate sandwiched between said resonant metal plate and said ground plate; and
at least two feed pins for electrically coupling said antenna with said circuit,
wherein each of said at least two feed pins is located in said substrate; each of said at least two feed pins protrudes through a hole in said ground plane, said at least two feed pins being physically unconnected to said ground plane; and none of said at least two feed pins is directly physically connected to said resonant metal plate.
2. The circuit according to claim 1 , wherein said antenna is a dual feed patch antenna.
3. The circuit according to claim 1 , wherein said first and second amplifiers are matched with respect to at least one of: input impedance, output impedance, gain, and phase shift.
4. The circuit according to claim 1 , wherein said antenna is a circularly polarized patch antenna.
5. The circuit according to claim 1 , wherein each of said at least two feed pins is coupled across said dielectric substrate to said resonant metal plate by a capacitive reactance.
6. The circuit according to claim 1 , wherein none of said at least two feed pins is directly physically connected to said resonant metal plate.
7. The circuit according to claim 5 , wherein each of said at least two feed pins is offset from said center of the resonant metal plate by an offset distance and a patch impedance for each of said at least two feed pins is determined by said offset distance and said capacitive reactance.
8. The circuit according to claim 7 , wherein, for a given offset distance, said patch impedance is lower when compared to an impedance for a feed pin which is directly physically coupled to said resonant metal plate.
9. The circuit according to claim 1 , wherein said circuit has a transfer function equivalent to a transfer function of a unidirectional 90 degree hybrid coupler.
10. A circuit for use in splitting signals for transmission by a dual feed antenna, the circuit comprising:
a first amplifier having a first input and a first output for driving a first feed pin of said dual feed antenna;
a second amplifier having a second input and a second output for driving a second feed pin of said dual feed antenna;
a common splitting node;
a capacitor coupled between the common splitting node and the first input of said first amplifier;
an inductor coupled between the common splitting node and the second input of said second amplifier;
wherein said first and second amplifiers are matched amplifiers, and wherein said dual feed antenna comprises:
a resonant metal plate;
a ground plate;
a dielectric substrate sandwiched between said resonant metal plate and said ground plate; and
at least two feed pins for electrically coupling said antenna with said circuit,
wherein each of said at least two feed pins is located in said substrate; each of said at least two feed pins protrudes through a hole in said ground plane, said at least two feed pins being physically unconnected to said ground plane; and none of said at least two feed pins is directly physically connected to said resonant metal plate.
11. The circuit according to claim 10 , wherein said antenna is a circularly polarized patch antenna.
12. The circuit according to claim 10 , wherein each of said at least two feed pins is coupled across said dielectric substrate to said resonant metal plate by a capacitive reactance.
13. The circuit according to claim 10 , wherein none of said at least two feed pins is directly physically connected to said resonant metal plate.
14. The circuit according to claim 12 , wherein each of said at least two feed pins is offset from said center of the resonant metal plate by an offset distance and a patch impedance for each of said at least two feed pins is determined by said offset distance and said capacitive reactance.
15. The circuit according to claim 14 , wherein, for a given offset distance, said patch impedance is lower when compared to an impedance for a feed pin which is directly physically coupled to said resonant metal plate.
16. The circuit according to claim 10 , wherein said circuit has a transfer function equivalent to a transfer function of a unidirectional 90 degree hybrid splitter.