Amplifiers – Hum or noise or distortion bucking introduced into signal...
Reexamination Certificate
1999-11-03
2001-02-13
Pascal, Robert (Department: 2817)
Amplifiers
Hum or noise or distortion bucking introduced into signal...
C330S304000, C375S296000, C455S127500
Reexamination Certificate
active
06188279
ABSTRACT:
BACKGROUND
The present invention relates generally to power amplifiers, and more particularly, to a miniature broadband linearizer for use with power amplifiers.
Heretofore, Lockheed Martin Corporation has developed a broadband linearizer that is implemented using passive FET technology. This broadband linearizer is discussed in a paper entitled “MMIC Linearizers for C and Ku-Band Satellite Applications”, by R. Dorval, published in 1998 IEEE MTT-S International Microwave Symposium Workshop”.
Nippon Electric Company (NEC) manufactures linearizers for use with power amplifiers. Such linearizers are disclosed in a report entitled “INTELSAT-VII Linearizer for Ku-Band TWTA”, and a “Linearizer for Ku-Band TWTA Performance Specification” (Specification No. E021307). The NEC linearizers use commandable switched frequency bands to cover a wide bandwidth. However, the basic design for each band of the NEC linearizers are narrow band. Also, the NEC linearizers use FET amplifiers as nonlinear elements.
Alcatel has developed a linearized channel amplifier that uses a MMIC amplifier as a nonlinear element.
AEG (Daimler-Benz AG) has developed a linearizer preamplifier that includes a nonlinear Schottky diode circuit, a phase shifter and three MMIC amplifiers. This preamplifier is disclosed in a paper entitled “Pseudomorphic Ku-Band GaAs HFET Linearizer Preamplifier Front End for Satellite TWT-Amplifiers”, published in the 1995 IEEE GaAs IC Symposium.
In general, however, these conventional linearizers also do not provide for a simple, compact low cost design that does not involve complex commandable switched band selection operation.
Accordingly, it would be advantageous to have a broadband linearizer that may be used with a power amplifier to improve the linearity and efficiency performance of the power amplifier across a wide frequency bandwidth.
SUMMARY OF THE INVENTION
The present invention provides for an improved miniature broadband linearizer that is a nonlinear circuit located before a power amplifier. The broadband linearizer improves the linearity and efficiency performance of the power amplifier across a wide frequency bandwidth.
The present invention provides for an improvement over a broadband linearizer described in U.S. Pat. Application Ser. No. 09/203,257 filed Dec. 1, 1998, entitled “Broadband Linearizer for Power Amplifiers”, assigned to the assignee of the present invention. The miniature broadband linearizer provides for a simplified version of this previous broadband linearizer, and uses a simplified bridge circuit, MMIC amplifiers, and a simplified control circuit disposed in a low cost, kovar housing, although other housing materials may be used, such as aluminum or aluminum silicon carbide, for example.
The broadband linearizer may be manufactured using a single level assembly, carrierless package approach. A batch production process may be used to manufacture the broadband linearizer, and a typical lot includes about 20 units. The broadband linearizer may be manufactured in production using automatic assembly and test systems.
Compared to the broadband bridge approach in the previous patent application, this bridge circuit is much simplified, the complex phase shifter circuit is eliminated and a second equalizer after the output combiner is added to flatten the gain performance over a wide frequency band.
The control circuit is simplified in that it has a single bias applied thereto, and has no command and telemetry circuitry. The low cost kovar housing has glass feedthroughs that are used for DC and RF connectors. A limiting function is implemented in the broadband linearizer to improve the linearity performance of the power amplifier near saturation. The low-cost nature of the broadband linearizer is realized by providing RF circuit simplification, including the use of the MMIC amplifiers, a simplified linearizer bridge, which requires minimal circuit tuning, a simplified single bias control circuit and single level carrierless packaging.
The miniature broadband linearizer may be used at any frequency band, including L, C, X, Ku, K, Ka, Q, V or W-band. The reduced to practice embodiment of the broadband linearizer operates over a wide bandwidth, 11.060 to 12.531 GHz in a reduced to practice embodiment. The miniature broadband linearizer also may be used with any type of power amplifier such as a travelling wave tube amplifier (TWTA) or solid state power amplifier (SSPA), for example.
The mass of a reduced to practice embodiment of the linearizer is less than 50 gm. The compact size of a reduced to practice embodiment of the broadband linearizer is 47 millimeters by 48 millimeters by 7 millimeters. The broadband linearizer has low power consumption, and consumes less than 1.2 Watts of DC power. The linearizer characteristics are shaped to complement the characteristics of travelling wave tube amplifiers or solid state power amplifiers to which they are mated as a function of both input power level and frequency.
The broadband linearizer has a simple, compact, low cost design that does not involve complex commandable switched band selection operation as is found in conventional broadband linearizers. When compared certain prior art linearizers, the present linearizer provides for greater broadband performance. The linearizer can compensate the gain and phase of power amplifier over a wide bandwidth (>20%). The broadband linearizer has a simplified control circuit. The linearizer uses a single bias (+8V), and has no command and telemetry functions. The control circuit provides regulated voltage bias to the MMIC amplifiers and temperature compensated current bias to the attenuators.
REFERENCES:
patent: 4752743 (1988-06-01), Pham et al.
patent: 5291148 (1994-03-01), Reisner et al.
patent: 5789978 (1998-08-01), Zhang et al.
patent: 5966049 (1999-10-01), Yuen et al.
Adams Mark D.
Fuchs James A.
Laursen Kirk G.
Yang Steve S.
Yuen Cindy H. C.
Choe Henry
Float Kenneth W.
Pascal Robert
Space Systems Loral, Inc.
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