System and method for modulating a signal at an antenna
View Patent ↗A Direct Spatial Antenna Modulation (DSAM) antenna structure makes use of the instantaneous electromagnetic field state of a radiating antenna structure to achieve direct modulation of a transmitted signal within the antenna. In contrast to existing amplitude and phase-only based digital modulation techniques, this innovative technique utilizes an inherent spatial modulation component, mapping data spatially to different locations in the antenna structure, where each location has different transmitting and receiving properties. This spatial component of the modulation can enable, for example, a unique increase in data transmission speed in a fixed spectral bandwidth with no increase in bit error rate over current phase and amplitude only modulation techniques. Additionally, the DSAM antenna structure affords important benefits in reduced hardware complexity, reduced supply current consumption, and relaxed amplifier linearity requirements. This abstract is not to be considered limiting, since other embodiments may deviate from the features described in this Abstract.
1. A direct spatial antenna modulation (DSAM) system comprising:
a radiating structure comprising a plurality of spatial points of origination, wherein a unique data symbol is associated with one or more of the plurality of spatial points of origination;
a common feed point for receiving an excitation signal; and
a switching system responsive to a baseband data signal, wherein in response to the presence of the unique data symbol in the baseband data signal, the switching system directs the excitation signal to the one or more spatial points of origination associated with the particular unique data symbol, and wherein the one or more spatial points of origination associated with the unique data symbol determine a characteristic of a signal emitted by the radiating structure.
2. The DSAM system of claim 1 , wherein the excitation signal is an unmodulated carrier.
3. The DSAM system of claim 1 wherein the signal emitted by the radiating structure comprises characteristics of a modulated signal selected from the group consisting of a quadrature phase shift keying (QPSK) signal, a binary phase shift keying (BPSK) signal, a dual circular polarized QPSK signal, a linearly polarized signal and a circularly polarized signal.
4. The DSAM system of claim 3 , wherein the circular polarization is selected from the group consisting of left hand circular polarization and right hand circular polarization.
5. The DSAM system of claim 1 , wherein the antenna structure comprises a square microstrip patch antenna further comprising:
a ground layer;
a top layer, wherein the top layer is situated above the ground layer and separated therefrom by a first dielectric layer and wherein the top layer comprises:
feed ports located opposite of a mid-point of each side of the square microstrip patch antenna, wherein each feed port establishes a signal path to a spatial point of origination;
top layer switching system elements at each corner; and
top layer transmission lines, wherein the top layer transmission lines are situated parallel to the edges of the top layer and connect the top layer switching elements in response to the digital data signal; and
a bottom layer, wherein the bottom layer is situated below the ground layer and is separated therefrom by a second dielectric layer, and wherein the bottom layer comprises:
bottom layer switching system elements each associated with a single feed port; and
bottom layer transmission lines, wherein the bottom layer transmission lines connect a first side of a bottom layer switching element to the common feed point and a second side of the bottom layer switching element to the single feed port associated with the bottom layer switching element in response to the digital data signal,
wherein, the top layer transmission lines, top layer switching elements, bottom layer transmission lines and bottom layer switching elements are configured so as to cause the square microstrip patch antenna to provide an odd multiple of ¼ guided wavelength electrical delay over the desired operating band of the device with respect to the common feed location, spatial points of origination, and switching system elements.
6. The DSAM system of claim 1 , wherein the switching system comprises a switching RF PIN diode.
7. The DSAM system of claim 1 , wherein the excitation signal is an unmodulated carrier and wherein the unique data symbol is associated with at least two spatial points of origination, and wherein in response to the presence of the unique data symbol in the baseband data signal, the switching system directs the unmodulated carrier signal to the at least two spatial points of origination associated with the unique data symbol.
8. The DSAM system of claim 7 , wherein the radiating structure is excited by the unmodulated carrier signal at the at least two spatial points of origination.
9. A method for determining a characteristic of a signal using a radiating structure, wherein the radiating structure comprises a plurality of spatial points of origination, a switching system and a common feed point, the method comprising:
associating a unique data symbol with one or more of the plurality of spatial points of origination;
directing an excitation carrier signal to the common feed point; and
applying a baseband data signal to the switching system, wherein in response to the presence of the unique data symbol in the baseband data signal, the switching system directs the excitation signal to the one or more spatial points of origination associated with the particular unique data symbol and wherein the one or more spatial points of origination associated with the unique data symbol determine a characteristic of a signal emitted by the radiating structure.
10. The method of claim 9 , wherein the excitation signal is an unmodulated carrier.
11. The method of claim 9 , wherein the signal emitted by the radiating structure comprises characteristics of a modulated signal selected from the group consisting of a quadrature phase shift keying (QPSK) signal, a binary phase shift keying (BPSK) signal, a dual circular polarized QPSK signal, a linearly polarized signal, and a circularly polarized signal.
12. The method of claim 11 , wherein the circular polarization is selected from the group consisting of left hand circular polarization and right hand circular polarization.
13. The method of claim 9 , wherein the switching system comprises a switching RF PIN diode.
14. The method of claim 9 , wherein the excitation signal is an unmodulated carrier and wherein the unique data symbol is associated with at least two spatial points of origination, and wherein applying a baseband data signal comprising the unique data symbol to the switching system comprises applying the baseband data signal comprising the unique data symbol to the switching system to direct the unmodulated carrier signal to the at least two spatial points of origination associated with the unique data symbol.
15. The method of claim 14 , wherein the radiating structure is excited by the unmodulated carrier signal in the at least two spatial points of origination.