Feedforward amplifier

• US 6,208,204 B1
• Filed: 12/14/1999
• Issued: 03/27/2001
• Est. Priority Date: 12/14/1998
• Status: Expired due to Term

• Current Assignee: NTT Mobile Communications Network Inc. (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Mobile Communications Network Inc. (Nippon Telegraph and Telephone Corporation)
• Inventors: Suzuki, Yasunori, Nojima, Toshio, Narahashi, Shoichi
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Nguyen, Patricia T.
• Application Number:
  US09/460,707
• Time in Patent Office: 469 Days
• Field of Search: 330/52, 330/149, 330/151
• US Class Current: 330/52
• CPC Class Codes: H03F 1/3229 using a loop for error extraction and another loop for error subtraction

Abstract

In the balance adjustment using a pilot signal in a distortion detector and a distortion canceller of a feed-forward amplifier for amplifying a CDMA transmission signal, a pilot code is spread by a long code different from that of the CDMA transmission signal to obtain the pilot signal. The pilot signal is converted to a signal of the transmission frequency band, and the converted signal is injected into the transmission signal at the input side of the amplifier. The pilot signal frequency band is detected from the output of an auxiliary amplifier of the distortion canceller and converted to the base band, thereafter being despread to detect the pilot signal (code).

Claims

1. A feed-forward amplifier for amplifying a code division multiple access signal, comprising:

a distortion detector which includes a main amplifier for amplifying a signal fed thereto from an input path and detects a nonlinear distortion component of said main amplifier;

a distortion canceller which includes an auxiliary amplifier for amplifying the distortion component detected by said distortion detector and injects said amplified distortion component again into the output of said main amplifier, thereby canceling said distortion component;

first pilot signal generating means for generating a first pilot signal;

second pilot signal generating means for generating a second pilot signal;

multiplexing means provided in said input path, for multiplexing said first pilot signal onto an input transmission signal and for providing the multiplexed signal to said distortion detector;

first variable attenuating means and first phase shifting means inserted in said distortion detector;

second pilot injecting means provided in the path of said main amplifier of said distortion detector, for injecting said second pilot signal;

second variable attenuating means and second variable phase shifting means inserted in said distortion canceller;

first level detecting means inserted in the path of said auxiliary amplifier of said distortion cancellor, for detecting the level of said first pilot signal;

second level detecting means inserted in the output path of said distortion canceller, for detecting the level of said second pilot signal; and

control means for controlling said first variable attenuating means and said first variable phase shifting means in a manner to minimize the detection level of said first level detecting means, and for controlling said second variable attenuating means and said second phase shifting means in a manner to minimize the detection level of said second level detecting means;

wherein said first pilot signal generating means comprises;

code generating means for generating a first pilot code of a predetermined code pattern;

spreading means for spreading said first pilot code by a spreading code in a radio communication system of said code division multiple access;

first signal converting means for converting the output of said spreading means to a signal of a predetermined frequency band to be amplified by said feed-forward amplifier, thereby generating said first pilot signal; and

wherein said first level detecting means comprises;

second signal converting means for frequency converting said predetermined frequency band amplified by said auxiliary amplifier to the base band;

despreading means for spectrum-despreading the output of said second signal converting means by said spreading code; and

code detecting means for detecting the level of said first pilot code from the output of said despreading means.

2. The feed-forward amplifier of claim 1, which further comprises:

power dividing means inserted in said input path of said distortion detector at the input side of said multiplexing means, for dividing a transmission signal to two transmission signals, and for supplying one of said two transmission signal to said distortion detector;

a series circuit of third variable attenuating means, third variable phase shifting means and a second auxiliary amplifying means which is supplied with the other of said two transmission signals divided by said power dividing means; and

power combining means for combining the output of said second pilot signal extracting means and the output of said series circuit, and for providing the combined output to said second level detecting means; and

wherein said control means;

controls said third variable attenuating means and said third variable phase shifting means in a manner to minimize the detection level of said second level detecting means;

controls said first variable attenuating means and said first variable phase shifting means in a manner to minimize the detection level of said first level detecting means; and

controls said second variable attenuating means and said second variable phase shifting means in a manner to minimize the detection level of said second level detecting means.

3. The feed-forward amplifier of claim 1, which further comprises:

first power dividing means for dividing said first pilot signal into two first pilot signals, and for applying one of said two first pilot signals to said multiplexing means;

a first series circuit of third variable attenuating means, third variable phase shifting means and second auxiliary amplifying means into which the other of said two first pilot signals divided by said first power dividing means is input;

second power dividing means for dividing the output of said main amplifier into two outputs, and for providing one of said two outputs to said distortion canceller;

first power combining means for combining the other of said two outputs from said second power dividing means and the output of said first series circuit;

a second series circuit of fourth variable attenuating means and fourth variable phase shifting means;

third power dividing means for dividing the output of said first power combining means to two outputs, and for providing one of said two outputs to said second series circuit;

third level detecting means supplied with the other of said two outputs from said third power dividing means, for detecting the level of said other output, and for providing the detected level to said control means; and

second power combining means for combining the output of said second series circuit and the output of said first pilot extracting means, and for providing the combined output to said first level detecting means; and

wherein said control means;

controls said third variable attenuating means and said third variable phase shifting means in a manner to minimize the detection level of said third level detecting means;

controls said fourth variable attenuating means and said fourth variable phase shifting means in a manner to minimize the detection level of said first level detecting means; and

controls said second variable attenuating means and said second variable phase shifting means in a manner to minimize the detection level of said second level detecting means.

4. The feed-forward amplifier of claim 3, which further comprises:

fourth power dividing means provided in said input path at the input side of said multiplexing means, for dividing a transmission signal to two transmission signals, and for providing one of said two transmission signals to said multiplexing means;

a third series circuit of fifth variable attenuating means, fifth variable phase shifting means and third auxiliary amplifying means which is supplied with the other of said two transmission signals divided by said fourth power dividing means; and

third power combining means for combining the output of said second power combining means and the output of said third series circuit, and for providing the combined output to said first level detecting means; and

wherein said control means;

controls said fourth variable attenuating means and said fourth variable phase shifting means in a manner to minimize the detection level of said third level detecting means;

controls said fifth variable attenuating means and said fifth variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

controls said first variable attenuating means and said first variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

controls said second variable attenuating means and said second variable phase shifting means in a manner to minimize the detection level of said second level detecting means; and

controls said third variable attenuating means and said third variable phase shifting means in a manner to minimize the detection level of said first level detecting means.

5. The feed-forward amplifier of claim 1, which further comprises:

a first switch provided in said input path at the input side of said multiplexing means, for turning ON and OFF a transmission signal;

first power dividing means for dividing said first pilot signal to two first pilot signals, and for applying one of said two first pilot signals to said multiplexing means;

second power dividing means for dividing the output of said main amplifier to two outputs, and for applying one of said two outputs to said distortion canceller;

a first series circuit of third variable attenuating means and third variable phase shifting means which is supplied with the other of said two outputs of said second power dividing means;

a second series circuit of fourth variable attenuating means, fourth variable phase shifting means and second auxiliary amplifying means which is supplied with the other of said two first pilot signals divided by said first power dividing means;

a second switch for turning ON and OFF a signal extracted at the output of said first pilot extracting means;

first power combining means for combining the output of said first power combining means and the output of said second series circuit; and

second power combining means for combining the output of said first power combining means and the output of said second series circuit, and for applying the combined output to said first level detecting means; and

wherein said control means;

turns OFF the output of said first pilot signal generating means and ON said first and second switches, and controls said third variable attenuating means and said third variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

turns ON the output of said first pilot signal generating means and OFF said first and second switches, and controls said fourth variable attenuating means and said fourth variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

turns ON the output of said first pilot signal generating means and ON said first and second switches, and controls said first variable attenuating means and said first phase shifting means in a manner to minimize the detection level of said first level detecting means, and shifts the controlled variable of said first variable attenuating means from a set value of said fourth variable attenuating means and the controlled variable of said first variable phase shifting means from a set value of said fourth variable phase shifting means; and

controls said second variable attenuating means and said variable second phase shifting means in a manner to minimize the detection level of said second level detecting means.

6. The feed-forward amplifier of claim 5, which further comprises:

third power combining means inserted between said first switch and said multiplexing means in said input path, for dividing a transmission signal to two transmission signals, and for applying one of said two transmission signals to said multiplexing means;

a third switch supplied with the other of said two transmission signals divided by said third power dividing means;

a third series circuit of fifth variable attenuating means, fifth variable phase shifting means and third auxiliary amplifying means which is supplied with the output of said third switch; and

third power combining means for combining the output of said second power combining means and the output of said third series circuit, and for applying the combined output to said first level detecting means; and

wherein said control means;

turns OFF said first pilot signal generating means, ON said first and second switches and OFF said third switch, and controls said third variable attenuating means and said third variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

turns ON said first pilot signal generating means, OFF said first and second switches and OFF said third switch, and controls said fourth variable attenuating means and said fourth variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

turns ON said first pilot signal generating means, ON said first and second switches and OFF said third switch, and controls said first variable attenuating means and said first variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

shifts the controlled variable of said first variable attenuating means from a set value of said fourth variable attenuating means, and shifts the controlled variable of said first variable phase shifting means from a set value of said fourth variable phase shifting means;

turns ON said first pilot signal generating means, ON said first and second switches and ON said third switch, and controls said fifth variable attenuating means and said fifth variable phase shifting means in a manner to minimize the detection level of said first level detecting means; and

controls said second variable attenuating means and said second variable phase shifting means in a manner to minimize the detection level of said second level detecting means.

13. The feed-forward amplifier of any one of claims 1 through 12, wherein a spreading code different from a spreading code for communication use, assigned to an area where said feed-forward amplifier is placed, is used for spectrum spreading in said spreading means.

14. The feed-forward amplifier of any one of claims 1 through 12, wherein said first pilot signal generating means includes error correcting encoding means for encoding said first pilot code into an error code and for applying it to said spreading means, and said first level detecting means includes an error correcting code decoding means for decoding the output of said despreading means and providing the decoded output to said code detecting means.

15. The feed-forward amplifier of any one of claims 1 through 12, wherein said second pilot signal generating means comprises:

second code generating means for generating a second pilot code of a predetermined second code pattern;

second spreading means for spectrum-spreading said second pilot code by a second spreading code in said code division multiple access radio communication; and

second-pilot first signal converting means for converting the output of said second spreading means to a signal of another frequency band to be amplified by said feed-forward amplifier and for providing said converted signal to said pilot injecting means; and

said second level detecting means comprises;

second-pilot second signal converting means for converting the extracted output of said second pilot signal extracting means to a base band signal;

second despreading means for spectrum-despreading said base band signal by said spreading code; and

second code detecting means for detecting the level of said second pilot code from the output of said second despreading means.

16. The feed-forward amplifier of claim 15, wherein said second pilot signal generating means includes second error correcting encoding means for encoding said second pilot code into an error correcting code and for outputting it to said second spreading means, and said second level detecting means includes decoding means for decoding the output of said second dispreading means.

17. The feed-forward amplifier of any one of claims 1 through 12, wherein said distortion detector comprises:

said input path into which a transmission signal is input;

a main amplifier signal path with said main amplifier inserted therein;

a linear signal path;

a power divider for branching said transmission signal to said main amplifier signal path and said linear signal path;

said first variable attenuating means and said first variable phase shifting means inserted in said main amplifier signal path; and

a power divider/combiner for combining the output of said main amplifier signal path and the output of said linear signal path and for dividing the combined output to two outputs; and

said distortion canceller comprises;

a distortion injection path which is supplied with one of said two outputs of said power combiner/divider and has said auxiliary amplifying means inserted therein;

a main signal path which is supplied with the other of said two outputs of said power combiner/divider;

said output path;

said second variable attenuating means and said second variable phase shifting means inserted in said distortion injection path; and

a power combiner for combining signals from said main signal path and said distortion injection path and for providing the combined output to said output path.

7. A feed-forward amplifier for amplifying a code division multiple access signal, comprising:

a distortion detector which includes a main amplifier for amplifying a signal fed thereto from an input path and detects a nonlinear distortion component of said main amplifier;

a distortion canceller which includes an auxiliary amplifier for amplifying the distortion component detected by said distortion detector and injects said amplified distortion component again into the output of said main amplifier, thereby canceling said distortion component;

first pilot signal generating means for generating a multiplexed signal of a transmission signal and a first pilot signal, and for applying said multiplexed signal to said distortion detector via said input path;

second pilot signal generating means for generating a second pilot signal;

first variable attenuating means and first variable phase shifting means inserted in said distortion detector;

pilot injecting means provided in the path of said main amplifier of said distortion detector, for injecting said second pilot signal;

second variable attenuating means and second variable phase shifting means inserted in said distortion canceller;

first level detecting means inserted in the path of said auxiliary amplifier of said distortion cancellor, for detecting the level of said first pilot signal;

second level detecting means inserted in the output path of said distortion canceller, for detecting the level of said second pilot signal; and

control means for controlling said first variable attenuating means and said first variable phase shifting means in a manner to minimize the detection level of said first level detecting means, and for controlling said second variable attenuating means and said second phase shifting means in a manner to minimize the detection level of said second level detecting means;

wherein said first pilot signal generating means comprises;

code generating means for generating a first pilot code of a predetermined code pattern;

spreading means for spreading said first pilot code by a spreading code in a radio communication system of said code division multiple access to generate a base-band first pilot signal;

multiplexing means for multiplexing said base-band first pilot signal from said spreading means onto a base-band transmission signal; and

first signal converting means for converting the output of said multiplexing means to a signal of a predetermined frequency band to be amplified by said feed-forward amplifier, thereby generating said first pilot signal multiplexed onto said transmission signal; and

wherein said first level detecting means comprises;

second signal converting means for converting a signal of said predetermined frequency band amplified by said auxiliary amplifier to a base band signal;

despreading means for spectrum-despreading the output of said second signal converting means by said spreading code; and

code detecting means for detecting the level of said first pilot code from the output of said despreading means.

8. The feed-forward amplifier of claim 7, which further comprises:

third signal converting means supplied with said base band transmission signal, for converting it to a transmission signal of said predetermined frequency band;

a series circuit of third variable attenuating means, third variable phase shifting means and second auxiliary amplifying means which is supplied with the output of said third signal converting means; and

power combining means for combining the output of said second pilot signal extracting means and the output of said series circuit, and for applying the combined output to said second level detecting means; and

wherein said control means;

controls said first variable attenuating means and said variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

controls said third variable attenuating means and said third variable phase shifting means in a manner to minimize the detection level of said second level detecting means; and

controls said second variable attenuating means and said second variable phase shifting means in a manner to minimize the detection level of said second level detecting means.

9. The feed-forward amplifier of claim 7, which further comprises:

third signal converting means supplied with said base band first pilot signal from said spreading means, for converting it to a signal of said predetermined frequency band;

a first series circuit of third variable attenuating means, third variable phase shifting means and second auxiliary amplifying means which is supplied with the output of said third signal converting means;

second power dividing means for dividing the output of said main amplifier to two outputs, for applying one of said two outputs to said distortion canceller;

first power combining means for combining the other of said two outputs divided by said second power dividing means and the output of said first series circuit;

a second series circuit of fourth variable attenuating means and fourth variable phase shifting means;

third power dividing means for dividing the output of said first power combining means to two outputs, and for applying one of said two outputs to said second series circuit;

third level detecting means supplied with the other of said two outputs divided by said third power dividing means, for detecting the level of said other output and applying the detected output to said control means; and

second power combining means for combining the output of said second series circuit and the output of said first pilot extracting means; and

wherein said control means;

controls said third variable attenuating means and said third variable phase shifting means in a manner to minimize the detection level of said third level detecting means;

controls said fourth variable attenuating means and said fourth variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

controls said first variable attenuating means and said first phase shifting means in a manner to minimize the detection level of said first level detecting means; and

controls said second variable attenuating means and said second variable phase shifting means in a manner to minimize the detection level of said second level detecting means.

10. The feed-forward amplifier of claim 9, which further comprises:

fourth signal converting means supplied with said base band transmission signal, for converting it to a transmission signal of said predetermined frequency band;

a third series circuit of fifth variable attenuating means and fifth variable phase shifting means which is supplied with said transmission signal from said fourth signal converting means; and

third power combining means for combining the output of said second power combining means and the output of said third series circuit, and for applying the combined output to said first level detecting means; and

wherein said control means;

controls said third variable attenuating means and said third variable phase shifting means in a manner to minimize the detection level of said third level detecting means;

controls said fourth variable attenuating means and said fourth variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

controls said fifth variable attenuating means and said fifth phase shifting means in a manner to minimize the detection level of said first level detecting means;

controls said first variable attenuating means and said first variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

shifts setting of said third and fifth variable attenuating means and said third and fifth phase shifting means by the controlled variables of said first variable attenuating means and said first variable phase shifting means; and

controls said second variable attenuating means and said second variable phase shifting means in a manner to minimize the detection level of said second level detecting means.

11. The feed-forward amplifier of claim 7, which further comprises:

a first switch for turning ON and OFF said base band transmission signal that is input into said multiplexing means of said first pilot signal generating means;

second power dividing means for dividing the output of said main amplifier to two outputs, and for applying one of said two outputs to said distortion canceller;

a first series circuit of third variable attenuating means and third variable phase shifting means which is supplied with the other of said two outputs divided by said second power dividing means;

a second series circuit of fourth variable attenuating means, fourth variable phase shifting means and second auxiliary amplifying means which is supplied with the output of said spreading means;

a second switch for turning ON and OFF the signal extracted by said first pilot extracting means;

first power combining means for combining the output of said second switch and the output of said first series circuit; and

second power combining means for combining the output of said first power combining means and the output of said second series circuit; and

wherein said control means;

turns OFF said first pilot signal generating means and ON said first and second switches, and controls said third variable attenuating means and said third variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

turns ON said first pilot signal generating means and OFF said first and second switches, and controls said fourth variable attenuating means and said fourth variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

turns ON said first pilot signal generating means and ON said first and second switches, and controls said first variable attenuating means and said first variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

shifts the controlled variable of said first variable attenuating means from a set value of said fourth variable attenuating means, and shifts the controlled variable of said fist variable phase shifting means from a set value of said fourth variable attenuating means; and

controls said second variable attenuating means and said second variable phase shifting means in a manner to minimize the detection level of said second level detecting means.

12. The feed-forward amplifier of claim 11, which further comprises:

a third switch supplied with said base band transmission signal, for turning ON and OFF its passage therethrough;

second signal converting means for converting the output of said third switch to a transmission signal to a transmission signal of said predetermined frequency band;

third series circuit of fifth variable attenuating means, fifth variable phase shifting means and third auxiliary amplifying means which is supplied with said transmission signal from said second signal converting means; and

third power combining means for combining the output of said second power combining means and the output of said third series circuit, and for applying the combined output to said first level detecting means; and

wherein said control means;

turns OFF said first pilot signal generating means, ON said first and second switches and OFF said third switch, and controls said third variable attenuating means and said third variable phase shifting means;

turns ON said first pilot signal generating means, OFF said first and second switches and OFF said third switch, and controls said fourth variable attenuating means and said fourth variable phase shifting means in a manner to minimize the detection level of said first level detecting means;

turns ON said first pilot signal generating means, ON said first and second switches and OFF said third switch, and controls said first variable attenuating means and said first variable phase shifting means to minimize the detection level of said first level detecting means;

shifts the controlled variable of said first variable attenuating means from a set value of said fourth variable attenuating means, and shifts the controlled variable of said first variable phase shifting means from a set value of said fourth variable phase shifting means;

turns ON said first pilot signal generating means, ON said first and second switches and ON said third switch, and controls said fifth variable attenuating means and said fifth variable phase shifting means in a manner to minimize the detection level of said first level detecting means; and

controls said second variable attenuating means and said second variable phase shifting means in a manner to minimize the detection level of said second level detecting means.