1. A memory cell for a magnetic memory device comprising:
a first hard magnetic layer having a first fixed magnetization vector;
a second hard magnetic layer having a second fixed magnetization vector,
a first soft magnetic layer having a first alterable magnetization vector and disposed adjacent to the first hard magnetic layer, and
a second soft magnetic layer having a second alterable magnetization vector and disposed adjacent to the second hard magnetic layer;
wherein the first and the second soft magnetic layers are magnetostatically coupled antiparallel to each other to form a flux-closed structure.
2. The memory cell as recited in claim 1, wherein the first and the second soft magnetic layers are disposed between the first and the second hard magnetic layers.
3. The memory cell as recited in claim 1, wherein the first and the second hard magnetic layers are disposed between the first and the second soft magnetic layers.
4. The memory cell as recited in claim 1, further comprising an anti-ferromagnetic layer disposed adjacent to one of the first and the second hard magnetic layers to fix the orientation of the magnetization vector therein.
5. The memory cell as recited in claim 4, further comprising an assistant magnetic layer disposed adjacent to one of the first and the second hard magnetic layers, wherein the assistant magnetic layer having a magnetization vector anti-parallelly aligned with one of the first and the second hard magnetic layers to reduce the static magnetic field thereof.
6. The memory cell as recited in claim 1, further comprising an electrically conductive layer disposed between the first and the second soft magnetic layers for passing an electric current therethrough.
7. The memory cell as recited in claim 6, wherein the memory cell is adapted to allow passing of an electric current in a first direction and at least one of the magnetization vectors of the first and the second hard magnet layers is orientated along a second direction oblique to the first direction.
8. A magnetic memory device comprising a plurality of memory cells as claimed in claim 1.
9. The magnetic memory device as recited in claim 8, further comprising an electrically conductive line coupled to the plurality of memory cells.
10. The magnetic memory device as recited in claim 9, further comprising a plurality of gate members each coupled to the plurality of memory cells through the electrically conductive line for controllably supplying an electric current to the respective memory cell through the electrically conductive line.
11. The magnetic memory device as recited in claim 9, wherein the electrically conductive line is provided for performing both a writing operation and a reading operation.
12. A memory cell for a magnetic memory device comprising:
a first hard magnetic layer having a first fixed magnetization vector,
a second hard magnetic layer having a second magnetization vector;
a first soft magnetic layer disposed adjacent to the first hard magnetic layer, the first soft magnetic layer having a first alterable magnetization vector; and
a second soft magnetic layer disposed adjacent to the second hard magnetic layer, the second soft magnetic layer having a second alterable magnetization vector,
wherein the memory cell is adapted to allow passing of an electric current in a first direction and at least one of the first fixed magnetization vector and the second fixed magnetization vector is oriented oblique with respect to the first direction of the electric current.
13. The memory cell as recited in claim 12, further comprising an electrically conductive layer disposed between the first and the second soft magnetic layers for allowing the electric current to pass through.
14. The memory cell as recited in claim 13, wherein the first and the second soft magnetic layers are magnetostatically coupled antiparallel to each other to form a flux-closed structure.
15. A magnetic memory device comprising a plurality of memory cells as recited in claim 12.
16. The magnetic memory device as recited in claim 15, further comprising an electrically conductive line coupled to the plurality of memory cells for passing an electric current therethrough.
17. The magnetic memory device as recited in claim 16, further comprising a plurality of gate members each coupled to the plurality of memory cells through the electrically conductive line for controllably passing an electric current to the respective memory cell through the electrically conductive line.
18. The magnetic memory device as recited in claim 15, wherein the electrically conductive line is provided for performing both a writing operation and a reading operation.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A base station that has a plurality of antennas and transmits a modulated signal for each independent channel from each antenna of said plurality of antennas, comprising:
a plurality of modulators that form a modulated signal independently for each antenna;
a receiver that receives feedback information from a communication terminal that receives said modulated signal; and
a transmission power controller that controls a transmission power of each transmission channel independently for each channel by controlling outputs of the plurality of modulators independently without combining the outputs, based on said feedback information of a corresponding channel, and modifies, independently for each antenna, the transmission power of the modulated signal transmitted from each antenna.
2. The base station according to claim 1, wherein:
said feedback information includes information indicating channel fluctuation of each modulated signal between each antenna of said base station and each antenna of said communication terminal, and information indicating received field strength of each antenna of said communication terminal; and
said transmission power control section controls transmission power of said each transmission channel independently for each channel based on said channel fluctuation value and said received field strength.
3. The base station according to claim 1, wherein said transmission power control section controls transmission power of each transmission channel independently for each channel by multiplying the modulated signal of said each independent channel by a multiplication coefficient obtained based on said channel fluctuation value of corresponding channel and a multiplication coefficient obtained from an eigenvalue of a channel fluctuation matrix that has a channel fluctuation value of each modulated signal between each antenna of said base station and each antenna of said communication terminal as an element.
4. The base station according to claim 1, wherein:
said modulation section forms an OFDM signal as said modulated signal;
said feedback information includes information generated based on a channel fluctuation value of each channel and each carrier; and
said transmission power control section controls transmission power independently for each channel and each subcarrier based on said feedback information of each channel and each carrier.
5. The base station according to claim 2, wherein:
said modulation section forms an OFDM signal as said modulated signal;
said feedback information includes information generated based on said channel fluctuation and said received field strength of each channel and each carrier; and
said transmission power control section controls transmission power independently for each channel and each subcarrier based on said feedback information and said received field strength of each channel and each carrier.
6. A communication system comprising a base station that has a plurality of antennas and transmits a modulated signal of each independent channel from each antenna and a communication terminal that receives modulated signals transmitted from said plurality of antennas and demodulates each modulated signal, wherein:
said base station comprises:
a modulation section that forms a modulated signal transmitted from each antenna;
a receiving section that receives from said communication terminal feedback information when said each modulated signal is received; and
a transmission power control section that controls transmission power of each transmission channel independently for each channel based on said feedback information of corresponding channel and modifies transmission power of the modulated signal transmitted from each antenna independently for each antenna, and
said communication terminal comprises:
a channel fluctuation estimation section that estimates channel fluctuation values of the received plurality of modulated signals;
an effective reception power calculation section that finds an effective reception power value of said modulated signals based on the estimated channel fluctuation values; and
a demodulation section that performs received signal demodulation processing using the calculated effective reception power value.
7. The communication system according to claim 6, wherein:
said effective reception power calculation section calculates an eigenvalue of a channel fluctuation matrix that has said channel fluctuation values as elements and takes that eigenvalue as an index of said effective reception power value; and
said demodulation section performs received signal demodulation processing using said eigenvalue.
8. The communication system according to claim 6, wherein said effective reception power calculation section finds effective reception power of said modulated signals using received field strength at an antenna in addition to said channel fluctuation modulation value.
9. A communication terminal used in a communication system comprising a base station that transmits different modulated signals from a plurality of antennas and a communication terminal that receives the modulated signals transmitted from said plurality of antennas at a plurality of antennas and demodulates each modulated signal, said communication terminal comprising:
a channel fluctuation estimation section that estimates channel fluctuation values of the received plurality of modulated signals;
an eigenvalue calculation section that calculates an eigenvalue of a channel fluctuation matrix that has said channel fluctuation values as elements; and
a demodulation section that performs received signal demodulation processing using the calculated eigenvalue, wherein:
said eigenvalue calculation section creates combinations of the plurality of antenna received signals, forms a channel fluctuation matrix for each combination, and calculates an eigenvalue of a channel fluctuation matrix of each combination; and
said demodulation section selects a combination of antenna received signals for which minimum power of said eigenvalue is greatest and performs demodulation processing thereon.
10. A communication terminal used in a communication system comprising a base station that transmits different modulated signals from a plurality of antennas and a communication terminal that receives the modulated signals transmitted from said plurality of antennas at a plurality of antennas and demodulates each modulated signal, said communication terminal comprising:
a channel estimation section that estimates channel fluctuation values of the received plurality of modulated signals;
an eigenvalue calculation section that calculates an eigenvalue of a channel fluctuation matrix that has said channel fluctuation values as elements; and
a demodulation section that performs received signal demodulation processing using the calculated eigenvalue, wherein:
said eigenvalue calculation section creates combinations of the plurality of antenna received signals, forms a channel fluctuation matrix for each combination, and calculates an eigenvalue of a channel fluctuation matrix of each combination; and
said demodulation section separates each modulated signal using each combination of antenna received signals and said channel fluctuation matrix corresponding to that combination, and also performs weighting and combining of modulated signals separated in each combination using a channel fluctuation matrix eigenvalue used at the time of separation.
11. A communication terminal used in a communication system comprising a base station that transmits different modulated signals from a plurality of antennas and a communication terminal that receives the modulated signals transmitted from said plurality of antennas and demodulates each modulated signal, said communication terminal comprising:
a channel fluctuation estimation section that estimates channel fluctuation values of the received plurality of modulated signals;
an eigenvalue calculation section that calculates an eigenvalue of a channel fluctuation matrix that has said channel fluctuation values as elements; and
a demodulation section that performs received signal demodulation processing using the calculated eigenvalue,
wherein said demodulation section comprises:
a soft decision value calculation section that calculates a weighted soft decision value using said eigenvalue; and
a decoding section that obtains a digital signal from the weighted soft decision value.
12. A communication terminal used in a communication system comprising a base station that transmits different modulated signals from a plurality of antennas and a communication terminal that receives the modulated signals transmitted from said plurality of antennas at a plurality of antennas and demodulates each modulated signal, said communication terminal comprising:
a channel fluctuation estimation section that estimates channel fluctuation values of the received plurality of modulated signals;
an eigenvalue calculation section that calculates an eigenvalue of a channel fluctuation matrix that has said channel fluctuation values as elements;
a received field strength detection section that detects received field strength of said each antenna received signal; and
a demodulation section that performs received signal demodulation processing using said eigenvalue corrected in accordance with received field strength of each antenna received signal.
13. The communication terminal according to claim 12, wherein said eigenvalue calculation section corrects said channel fluctuation matrix based on received field strength of each antenna received signal so that power of said each channel fluctuation value becomes equal, and calculates said eigenvalue using the corrected channel fluctuation matrix.
14. The communication system according to claim 6, wherein said communication terminal comprises a reception level control section that detects a signal level of said each antenna received signal and makes the signal level of said each antenna received signal equal.
15. A transmitting method that provides a plurality of antennas and transmits a modulated signal for each independent channel from each antenna of the plurality of antennas, comprising:
forming a modulated signal independently for each antenna;
receiving feed back information from a communication terminal that receives said modulated signal; and
controlling a transmission power of each transmission channel independently for each channel by controlling outputs of the plurality of modulators independently without combining the outputs,_based on the received feedback information of a corresponding channel, the transmission power of the modulated signal transmitted from each antenna being modified independently for each antenna.