Amplifier linearization by adaptive predistortion

Claim 1

A method of linearizing an amplifier to produce an amplified output sample v a in response to a predistorted input sample v d derived from an input modulation sample v m , such that v a ≃Kv m , where K is the desired constant amplitude gain of said amplifier, said method comprising the steps of: (a) deriving the squared magnitude x m of said input modulation sample v m ; (b) selecting, from a table containing N t values F i where i=0, 1, . . . , N t -1, each of said entries corresponding to a squared magnitude values x mi , and for each of which entries F i G(x mi )|F i | 2 )≃K where G(x) is the complex gain of said amplifier, a table entry F i for which x mi is: (i) the largest table entry less than or equal to x m ; or, (ii) the smallest table entry greater than or equal to x m ; (c) deriving said predistorted sample v d as v d =v m F i in rectangular coordinates, viz: Re(v.sub.d)=Re(v.sub.m)Re(F.sub.i)-Im(V.sub.m)Im(F.sub.i) Im(v.sub.d)=Re(v.sub.m)Im(F.sub.i)+Im(V.sub.m)Re(F.sub.i) where Re(x) is the real component of x and Im(x) is the imaginary component of x; and, (d) driving said amplifier with said predistorted input sample v d .

Claim 2

A method of linearizing an amplifier to produce an amplified output sample v a in response to a predistorted input sample v d derived from an input modulation sample v m , such that v a ≃Kv m , where K is the desired constant amplitude gain of said amplifier, said method comprising the steps of: (a) deriving the squared magnitude x m of said input modulation sample v m ; (b) selecting, from a table containing N t values F i where i=0, 1, . . . , N t -1, each of said entries corresponding to a squared magnitude values x mi , and for each of which entries F i G(x mi )|F i | 2 )≃K where G(x) is the complex gain of said amplifier, a table entry F i for which x mi is: (i) the largest table entry less than or equal to x m ; or, (ii) the smallest table entry greater than or equal to x m ; (c) deriving said predistorted sample v d as v d =v m F i in rectangular coordinates, viz: Re(v.sub.d)=Re(v.sub.m)Re(F.sub.i)-Im(V.sub.m)Im(F.sub.i) Im(v.sub.d)=Re(v.sub.m)Im(F.sub.i)+Im(V.sub.m)Re(F.sub.i) where Re(x) is the real component of x and Im(x) is the imaginary component of x; and, (d) driving said amplifier with said predistorted input sample v d .

Claim 4

A method of linearizing an amplifier to produce an amplified output sample v a (k) in response to a predistorted input sample v d (k) derived from an input modulation sample v m (k), such that v a (k)≃Kv m (k), where K is the desired constant amplitude gain of said amplifier and k denotes the k th such samples, said method comprising the steps of: (a) deriving the squared magnitude x m (k) of said input modulation sample v m (k); (b) selecting, from a table of N t entitles F i where i=0, 1, . . . , N t -1, each of said entries containing a squared magnitude value x mi , and for each of which entries F i G(x mi )|F i | 2 )≃K where G(x) is the complex gain of said amplifier, a table entry F i (x m (k)) for which x mi is: (i) the largest table entry less than or equal to x m (k); or, (ii) the smallest table entry greater than or equal to x m (k); (c) deriving said predistorted sample v d (k) as v d (k) = v m (k)F i (x m (k)) in rectangular coordinates, viz: Re(v.sub.d (k))=Re(v.sub.m (k))Re(F.sub.i (k))-Im(v.sub.m (k))Im (F.sub.i (x.sub.m (k))) Im(v.sub.d (k))=Re(v.sub.m (k))Im(F.sub.i (x.sub.m (k)))+Im(vhd m( k))Re(F.sub.i (x.sub.m (k))) where Re(x) is the real component of x and Im(x) is the imaginary component of x; (d) driving said amplifier with said predetermined input sample v d (k); (e) incrementing k by 1; and, (f) sequentially repeating steps (a) through (e).

Claim 5

A method of linearizing an amplifier to produce an amplified output sample v a (k) in response to a predistorted input sample v d (k) derived from an input modulation sample v m (k), such that v a (k)≃Kv m (k), where K is the desired constant amplitude gain of said amplifier and k denotes the k th such samples, said method comprising the steps of: (a) deriving the squared magnitude x m (k) of said input modulation sample v m (k); (b) selecting, from a table of N t entitles F i where i=0, 1, . . . , N t -1, each of said entries containing a squared magnitude value x mi , and for each of which entries F i G(x mi )|F i | 2 )≃K where G(x) is the complex gain of said amplifier, a table entry F i (x m (k)) for which x mi is: (i) the largest table entry less than or equal to x m (k); or, (ii) the smallest table entry greater than or equal to x m (k); (c) deriving said predistorted sample v d (k) as v d (k) = v m (k)F i (x m (k)) in rectangular coordinates, viz: Re(v.sub.d (k))=Re(v.sub.m (k))Re(F.sub.i (k))-Im(v.sub.m (k))Im (F.sub.i (x.sub.m (k))) Im(v.sub.d (k))=Re(v.sub.m (k))Im(F.sub.i (x.sub.m (k)))+Im(vhd m( k))Re(F.sub.i (x.sub.m (k))) where Re(x) is the real component of x and Im(x) is the imaginary component of x; (d) driving said amplifier with said predetermined input sample v d (k); (e) incrementing k by 1; and, (f) sequentially repeating steps (a) through (e).

Claim 6

A method of linearizing an amplifier to produce an amplified output sample v a (k) in response to a predistorted input sample v d (k) derived from an input modulation sample v m (k), such that v a (k)≃Kv m (k), where K is the desired constant amplitude gain of said amplifier and k denotes the k th such sample, said method comprising the steps of: (a) deriving the squared magnitude x m (k) of said input modulation sample v m (k); (b) selecting, from a table of N t entries F i (k) where i= 0, 1, . . . , N t -1, each of said entries containing a squared magnitude value x mi (k), and for each of which entries F i (k)G(x mi (k)|F i (k)| 2 )≃K where G(x) is the complex gain of said amplifier, a table entry F i (k) for which x mi is: (i) the largest table entry less than or equal to x m (k); or, (ii) the smallest table entry greater than or equal to x m (k); (c) deriving said predistorted sample v d (k) as v d (k)= v m (k)F I (k) in rectangular coordinates, viz: Re(v.sub.d (k))=Re(v.sub.m (k))Re(F.sub.i (k))-Im(V.sub.m (k))Im( F.sub.i (k)) Im(v.sub.d (k))=Re(v.sub.m (k))Im(F.sub.i (k))+Im(V.sub.m (K)) Re(F.sub.i (K)) where Re(x) is the real component of x and Im(x) is the imaginary component of x; (d) driving said amplifier with said predistorted input sample v d (k); (e) deriving said amplified output sample v a (k); (f) deriving an error sample e(k)-(v a (k)-Kv m (k))v m * (k); (g) deriving an adjusted value F=hd i(k+1) of said selected table entry F i (k), where: ##EQU14## where α is an appropriately chosen constant; (h) replacing said table entry F i (k) with said adjusted value F i (k+1); (i) incrementing k by 1; and, (j) sequentially repeating steps (a) through (i).

Claim 7

A method of linearizing an amplifier to produce an amplified output sample v a (k) in response to a predistorted input sample v d (k) derived from an input modulation sample v m (k), such that v a (k)≃Kv m (k), where K is the desired constant amplitude gain of said amplifier and k denotes the k th such sample, said method comprising the steps of: (a) deriving the squared magnitude x m (k) of said input modulation sample v m (k); (b) selecting, from a table of N t entries F i (k) where i= 0, 1, . . . , N t -1, each of said entries containing a squared magnitude value x mi (k), and for each of which entries F i (k)G(x mi (k)|F i (k)| 2 )≃K where G(x) is the complex gain of said amplifier, a table entry F i (k) for which x mi is: (i) the largest table entry less than or equal to x m (k); or, (ii) the smallest table entry greater than or equal to x m (k); (c) deriving said predistorted sample v d (k) as v d (k)= v m (k)F I (k) in rectangular coordinates, viz: Re(v.sub.d (k))=Re(v.sub.m (k))Re(F.sub.i (k))-Im(V.sub.m (k))Im( F.sub.i (k)) Im(v.sub.d (k))=Re(v.sub.m (k))Im(F.sub.i (k))+Im(V.sub.m (K)) Re(F.sub.i (K)) where Re(x) is the real component of x and Im(x) is the imaginary component of x; (d) driving said amplifier with said predistorted input sample v d (k); (e) deriving said amplified output sample v a (k); (f) deriving an error sample e(k)-(v a (k)-Kv m (k))v m * (k); (g) deriving an adjusted value F=hd i(k+1) of said selected table entry F i (k), where: ##EQU14## where α is an appropriately chosen constant; (h) replacing said table entry F i (k) with said adjusted value F i (k+1); (i) incrementing k by 1; and, (j) sequentially repeating steps (a) through (i).

Claim 11

A method of linearizing an amplifier to produce an amplified output sample v a in response to a predistorted input sample v d derived from an input modulation sample v m , such that v a ≃Kv m , where K is the desired constant amplitude gain of said amplifier, said method comprising the steps of: (a) deriving the squared magnitude x m of said input modulation sample v m ; (b) deriving, by interpolation on a table containing N t values F i where i=0, 1, . . . , N t -1, each of said entries corresponding to a squared magnitude value x mi , and for each of which entries F i G(x mi |F i | 2 )≃K where G(x) is the complex gain of said amplifier, a value F(x m ); (c) deriving said predistorted sample v d as v d =v m F(x m ) in rectangular coordinates, viz: Re(v.sub.d)=Re(v.sub.m)Re(F(x.sub.m))-IM(V.sub.m)Im(F(x.sub.m)) Im(v.sub.d)=Re(v.sub.m)Im(F(x.sub.m))+Im(V.sub.m)Re(F(x.sub.m)) where Re (x) is the real component of x and Im(x) is the imaginary component of x; and, (d) driving said amplifier with said predistorted input sample v d .

Claim 12

A method of linearizing an amplifier to produce an amplified output sample v a in response to a predistorted input sample v d derived from an input modulation sample v m , such that v a ≃Kv m , where K is the desired constant amplitude gain of said amplifier, said method comprising the steps of: (a) deriving the squared magnitude x m of said input modulation sample v m ; (b) deriving, by interpolation on a table containing N t values F i where i=0, 1, . . . , N t -1, each of said entries corresponding to a squared magnitude value x mi , and for each of which entries F i G(x mi |F i | 2 )≃K where G(x) is the complex gain of said amplifier, a value F(x m ); (c) deriving said predistorted sample v d as v d =v m F(x m ) in rectangular coordinates, viz: Re(v.sub.d)=Re(v.sub.m)Re(F(x.sub.m))-IM(V.sub.m)Im(F(x.sub.m)) Im(v.sub.d)=Re(v.sub.m)Im(F(x.sub.m))+Im(V.sub.m)Re(F(x.sub.m)) where Re (x) is the real component of x and Im(x) is the imaginary component of x; and, (d) driving said amplifier with said predistorted input sample v d .