Multiple-input and multiple-output amplifier using mutual induction in the feedback network

Abstract

The invention relates to an amplifier capable of producing a plurality of output signals, these output signals being controlled by a plurality of input signals. A multiple-input and multiple-output amplifier of the invention includes 4 signal input terminals, 4 signal output terminals, 4 active sub-circuits and a feedback network. Each active sub-circuit has a sub-circuit input terminals connected to one of the signal input terminals, a sub-circuit output terminal connected to one of the signal output terminals and a sub-circuit common terminal. The feedback network uses mutual induction between windings. The feedback network has terminals connected to the sub-circuit common terminal of the active sub-circuits. The feedback network presents an impedance matrix producing a negative feedback such that the transfer admittance matrix of the multiple-input and multiple-output amplifier approximates a given admittance matrix.

The invention claimed is: 
     
       1. A multiple-input and multiple-output amplifier having one reference terminal, n signal input terminals and n signal output terminals, where n is an integer greater than or equal to 3, the multiple-input and multiple-output amplifier comprising:
 n active sub-circuits, each active sub-circuit having a sub-circuit input terminal, a sub-circuit output terminal and a sub-circuit common terminal, the sub-circuit input terminal being connected to one of said signal input terminals and the sub-circuit output terminal being connected to one of said signal output terminals, each active sub-circuit being configured such that current flowing out of the sub-circuit common terminal and current flowing into the sub-circuit output terminal depend on a voltage between the sub-circuit input terminal and the sub-circuit common terminal, each said signal input terminal being connected to only one sub-circuit input terminal and each said signal output terminal being connected to only one sub-circuit output terminal; and 
 a feedback network having a terminal connected to said reference terminal, the feedback network also having n other terminals each being connected to the sub-circuit common terminal of one of said active sub-circuits, the feedback network presenting, in a known frequency band, a non-diagonal impedance matrix, this impedance matrix being defined with respect to said reference terminal, the feedback network comprising two or more windings arranged in such a way that, in a part of the known frequency band, the mutual induction between the different windings of the feedback network has a non-negligible influence on the value of one or more non-diagonal components of said impedance matrix. 
 
     
     
       2. The multiple-input and multiple-output amplifier of  claim 1 , wherein the feedback network produces a negative feedback such that, in the known frequency band, the transfer admittance matrix of the multiple-input and multiple-output amplifier approximates a given admittance matrix, this given admittance matrix being a non-diagonal and invertible n×n matrix. 
     
     
       3. The multiple-input and multiple-output amplifier of  claim 1 , wherein at least one coefficient of coupling between two windings is greater than or equal to one percent, in said part of the known frequency band. 
     
     
       4. The multiple-input and multiple-output amplifier of  claim 1 , wherein two or more windings of the plurality of windings of the feedback network are arranged in such a way that mutual induction appears between such windings and such windings are windings of a same transformer. 
     
     
       5. The multiple-input and multiple-output amplifier of  claim 1 , wherein two or more windings of the plurality of windings of the feedback network are arranged in such a way that mutual induction appears between such windings and such windings are windings made of printed circuit board traces. 
     
     
       6. The multiple-input and multiple-output amplifier of  claim 1 , wherein two or more windings of the plurality of windings of the feedback network are arranged in such a way that mutual induction appears between such windings and such windings are windings built in an integrated circuit. 
     
     
       7. The multiple-input and multiple-output amplifier of  claim 1 , wherein said feedback network comprises linear, passive and reciprocal circuit elements. 
     
     
       8. The multiple-input and multiple-output amplifier of  claim 1 , wherein said feedback network comprises one or more insulated-gate field-effect transistors. 
     
     
       9. The multiple-input and multiple-output amplifier of  claim 1 , wherein said feedback network is configured such that said non-diagonal impedance matrix is adjustable by electrical means. 
     
     
       10. The multiple-input and multiple-output amplifier of  claim 1 , wherein said active sub-circuits have an absolute value of the ratio of the current flowing out of the sub-circuit common terminal to the voltage between the sub-circuit input terminal and the sub-circuit common terminal that is larger than the absolute values of all components of the inverse of said impedance matrix of the feedback network. 
     
     
       11. The multiple-input and multiple-output amplifier of  claim 1 , wherein the loaded output admittance matrix of the multiple-input and multiple-output amplifier approximates a first wanted matrix. 
     
     
       12. The multiple-input and multiple-output amplifier of  claim 1 , wherein the loaded input admittance matrix of the multiple-input and multiple-output amplifier approximates a second wanted matrix. 
     
     
       13. A multiple-input and multiple-output amplifier, comprising:
 n signal input terminals, n signal output terminals and n active sub-circuits, wherein:
 n is an integer greater than or equal to 3, and 
 each signal input terminal and each signal output terminal is coupled to a unique one of the n active sub-circuits; and 
   a feedback network including a terminal, n other terminals and at least two windings, wherein:
 the terminal is connected to a reference terminal, 
 each one of the n other terminals is connected to the sub-circuit common terminal of a unique one of the n active sub-circuits, and 
 the at least two windings define a mutual induction between them. 
   
     
     
       14. The multiple-input and multiple-output amplifier of claim 13, wherein each active sub-circuit is configured such that current flowing out of a sub-circuit common terminal and current flowing into a sub-circuit output terminal depend on a voltage between a sub-circuit input terminal and the sub-circuit common terminal. 
     
     
       15. The multiple-input and multiple-output amplifier of claim 14, wherein:
 the feedback network presents, in a known frequency band, a non-diagonal impedance matrix, the non-diagonal impedance matrix being defined with respect to the reference terminal; and   the at least two windings are arranged in such a way that, in a part of the known frequency band, the mutual induction has a non-negligible influence on a value of at least one non-diagonal component of the non-diagonal impedance matrix.   
     
     
       16. The multiple-input and multiple-output amplifier of claim 13, wherein the feedback network presents, in a known frequency band, a non-diagonal impedance matrix, the non-diagonal impedance matrix being defined with respect to the reference terminal. 
     
     
       17. The multiple-input and multiple-output amplifier of claim 16, wherein the at least two windings are arranged in such a way that, in a part of the known frequency band, the mutual induction has a non-negligible influence on a value of at least one non-diagonal component of the non-diagonal impedance matrix. 
     
     
       18. A method for multiple-input and multiple-output amplification, wherein n is an integer greater than or equal to 3, comprising:
 connecting each of n signal input terminals of an amplifier to a sub-circuit input terminal of a unique one of n active amplifier sub-circuits;   connecting each of n signal output terminals of the amplifier to a sub-circuit output terminal of a unique one of the n active amplifier sub-circuits;   connecting a terminal of an amplifier feedback network to a reference terminal of the amplifier; and   connecting n other terminals of the amplifier feedback network to a sub-circuit common terminal of a unique one of the n active amplifier sub-circuits, wherein the amplifier feedback network includes at least two windings that define a mutual induction between them.   
     
     
       19. The method for multiple-input and multiple-output amplification of claim 18, further comprising:
 configuring each of the n active amplifier sub-circuits such that current flowing out of a sub-circuit common terminal and current flowing into the sub-circuit output terminal depend on a voltage between the sub-circuit input terminal and the sub-circuit common terminal.   
     
     
       20. The method for multiple-input and multiple-output amplification of claim 19, further comprising:
 configuring the amplifier feedback network to present, in a known frequency band, a non-diagonal impedance matrix, the non-diagonal impedance matrix being defined with respect to the reference terminal; and   arranging the at least two windings in such a way that, in a part of the known frequency band, the mutual induction has a non-negligible influence on a value of at least one non-diagonal component of the non-diagonal impedance matrix.   
     
     
       21. The method for multiple-input and multiple-output amplification of claim 18, further comprising:
 configuring the amplifier feedback network to present, in a known frequency band, a non-diagonal impedance matrix, the non-diagonal impedance matrix being defined with respect to the reference terminal.   
     
     
       22. The method for multiple-input and multiple-output amplification of claim 21, further comprising:
 arranging the at least two windings in such a way that, in a part of the known frequency band, the mutual induction has a non-negligible influence on a value of at least one non-diagonal component of the non-diagonal impedance matrix.   
     
     
       23. An apparatus for multiple-input and multiple-output amplification, wherein n is an integer greater than or equal to 3, comprising:
 means for connecting each of n signal input terminals of an amplifier to a sub-circuit input terminal of a unique one of n active amplifier sub-circuits;   means for connecting each of n signal output terminals of the amplifier to a sub-circuit output terminal of a unique one of the n active amplifier sub-circuits;   means for connecting a terminal of an amplifier feedback network to a reference terminal of the amplifier; and   means for connecting n other terminals of the amplifier feedback network to a sub-circuit common terminal of a unique one of the n active amplifier sub-circuits, wherein the amplifier feedback network includes at least two windings that define a mutual induction between them.   
     
     
       24. The apparatus for multiple-input and multiple-output amplification of claim 23, further comprising:
 means for configuring each of the n active amplifier sub-circuits such that current flowing out of a sub-circuit common terminal and current flowing into the sub-circuit output terminal depend on a voltage between the sub-circuit input terminal and the sub-circuit common terminal.   
     
     
       25. The apparatus for multiple-input and multiple-output amplification of claim 24, further comprising:
 means for configuring the amplifier feedback network to present, in a known frequency band, a non-diagonal impedance matrix, the non-diagonal impedance matrix being defined with respect to the reference terminal; and   means for arranging the at least two windings in such a way that, in a part of the known frequency band, the mutual induction has a non-negligible influence on a value of at least one non-diagonal component of the non-diagonal impedance matrix.   
     
     
       26. The apparatus for multiple-input and multiple-output amplification of claim 23, further comprising:
 means for configuring the amplifier feedback network to present, in a known frequency band, a non-diagonal impedance matrix, the non-diagonal impedance matrix being defined with respect to the reference terminal.   
     
     
       27. The apparatus for multiple-input and multiple-output amplification of claim 26, further comprising:
 means for arranging the at least two windings in such a way that, in a part of the known frequency band, the mutual induction has a non-negligible influence on a value of at least one non-diagonal component of the non-diagonal impedance matrix.