Amplifiers – With control of power supply or bias voltage – With control of input electrode or gain control electrode bias
Reexamination Certificate
1999-06-09
2001-06-05
Lee, Benny (Department: 2817)
Amplifiers
With control of power supply or bias voltage
With control of input electrode or gain control electrode bias
C330S289000, C330S284000
Reexamination Certificate
active
06242976
ABSTRACT:
BACKGROUND
The present invention relates generally to linearized channel amplifiers, and more particularly, to an improved low cost linearized channel amplifier designed for use with high power amplifiers.
Lockheed Martin Corporation has developed a linearized channel amplifier that is described in a paper entitled “Linearized Traveling Wave Tube Amplifiers for Space”, by Shabbir Moochalla, published in 1998 IEEE MTT-S International Microwave Symposium & Exhibition. The Lockheed Martin linearized channel amplifier uses a passive FET technology developed by Lockheed Martin that is used to implement the linearizer circuit.
Nippon Electric Corporation has developed a linearized channel amplifier that is described in a document entitled “INTELSAT-VII Linearizer for Ku-Band TWTA”. The NEC linearized channel amplifier uses an FET amplifier as the nonlinear element for the linearizer.
Alcatel has developed a linearized channel amplifier that is described in a data sheet published by the company. The Alcatel linearized channel amplifier uses a MMIC amplifier as the nonlinear element for the linearizer.
Bosch Telecom, GmbH has developed a linearized channel amplifier that is described in a data sheet published by the company. The Bosch linearized channel amplifier uses a passive diode as the nonlinear element for the linearizer.
All of the four above-mentioned designs are different from the design approach used in the present invention. It would be desirable to have a low cost linearized channel amplifier designed for use with high power amplifiers that improves upon currently available approaches, such as those mentioned above.
SUMMARY OF THE INVENTION
The present invention provides for low cost linearized channel amplifier comprising a linear channel amplifier circuit and a nonlinear linearizer circuit located immediately before a high power amplifier. A common control circuit controls the linear channel amplifier and nonlinear linearizer circuits. The linearized channel amplifier functions as a driver amplifier and also improves the linearity and efficiency performance of the high power amplifier across a desired frequency bandwidth.
The linearized channel amplifier of the present invention may be used in any frequency band including L, C, X, Ku, K, Ka, Q, V, and W-Band, for example. The linearized channel amplifier may also be used with any high power amplifier including traveling wave tube amplifiers (TWTA) and solid state power amplifiers (SSPA).
The novelty of the present linearized channel amplifier is a result of a number of factors. The linearizer circuit is based on concepts developed by the assignee of the present invention disclosed in U.S. Pat. No. 5,789,978, entitled “Ku-Band Linearizer Bridge”. The linearized channel amplifier uses a simple low cost temperature compensation design approach. Also, the linearized channel amplifier uses a novel methodology to provide for all command and control functions that includes a measurement, analytical calculation and setting process. The conventional time-consuming tune and test process over temperature is thus eliminated. This translates to lower production costs.
The linearized channel amplifier may use an external personality plug to set the performance of the channel amplifier and linearizer. The use of the external personality plug makes the design extremely flexible for setting linearized channel amplifier performance to match to the high power amplifier performance. Alternatively, the functions of the external personality plug may be implemented in the control circuit.
Various advantages are provided by the linearized channel amplifier. A preferred embodiment of the linearized channel amplifier includes a channel amplifier and a linearizer integrated into one single package to save size, weight, interface complexity and cost. The interface of the linearized channel amplifier may transmit and receive either pulse commands or serial interface adapter (SIA) commands.
A reduced-to-practice embodiment of the channel amplifier provides both fixed gain operation (31 steps with 1 dB step) and ALC mode operation (31 steps with 0.5 dB step) over more than a 40 dB dynamic range. The channel amplifier has the ability to telemetry fixed gain/ALC mode (TTL) and output power (analog) status. The linearizer has independent controls of gain and phase over input power level and across wide bandwidth. The design of the linearizer is flexible to compensate power amplifiers (TWTA or SSPA) with any variation of gain and phase performance.
The linearizer has both active and bypass modes. A reduced-to-practice embodiment of the linearizer has a commandable output power range of 7.5 dB with 0.5 dB step size and an output level limiting capability. The linearizer has the ability to telemetry linearizer activelbypass mode (TTL) and output level (analog) status. The linearizer may be realized on a compact size, single alumina substrate using PIN and Schottky diodes or using MMIC chips to minimize production cost. Reduced-to-practice embodiments of both the channel amplifier and the linearizer may be temperature compensated to within less than +/−0.25 dB using a novel temperature compensation circuit.
REFERENCES:
patent: 4554511 (1985-11-01), Braun
patent: 5862460 (1999-01-01), Rich
patent: 5977831 (1999-11-01), Davis
patent: 6118336 (2000-09-01), Pullen et al.
Adams Mark
Ethridge David
Smith Kevin
Yang Steve S.
Yuen Cindy
Float Kenneth W.
Lee Benny
Nguyen Khanh V.
Space Systems Loral, Inc.
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