Amplifiers – With distributed parameter-type coupling means – Push-pull
Reexamination Certificate
1999-06-01
2001-07-24
Pascal, Robert (Department: 2817)
Amplifiers
With distributed parameter-type coupling means
Push-pull
C330S286000, C333S247000
Reexamination Certificate
active
06265937
ABSTRACT:
S
TATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to push-pull amplifiers, and in particular to push-pull amplifiers having active devices connected to coplanar transmission lines having coplanar conductors formed on a base substrate.
2. Related Art
Because GaAs integrated circuits are comparatively expensive, it is common to make microwave and millimeter (mm) wave circuits as hybrid circuits. The active devices that require the use of GaAs are fabricated on GaAs chips which are then mounted on a motherboard or base substrate made of a less expensive material, such as silicon, Al
2
O
3
, BeO, and AIN.
Conventional circuits having a plurality of active devices are made by fabricating a separate integrated circuit or chip for each of the active devices. Circuit metalization and passive devices are printed on the base substrate and each chip is then mounted at an assigned site on the base substrate. The integrated circuit on the chip can be very simple, such as a single FET. It may also be more complex, incorporating a variety of devices to provide an overall function, such as is provided by an amplifier.
A complex circuit may require that numerous such chips be made and mounted. The resultant requirement for individual handling of small chips also tends to make the fabrication process somewhat costly. Alternatively, when a chip has a complex circuit, it is more expensive to make since it requires a larger GaAs substrate than its more simple cousin, and the benefits of hybrid circuit structure are not as fully realized.
There is thus a need for a method of hybrid circuit construction, and thereby a hybrid circuit structure that, when applied to microwave and mm-wave circuits, has reduced size and is simple to fabricate, thereby providing for efficient fabrication at reduced cost.
SUMMARY OF THE INVENTION
These benefits are achieved in the present invention which is directed to a push-pull amplifier having a plurality of pairs of active devices connected to a corresponding plurality of coplanar transmission lines formed on a base substrate. More particularly, the present invention is directed to a push-pull amplifier having first and second coplanar transmission lines on a substrate surface and having respective first and second pairs of conductors. The first conductor of each pair conducts a signal in phase opposition relative to a signal conducted on the second conductor of the pair. An active device associated with each conductor has an input or output terminal connected to the associated conductor, whereby each pair of active devices is connected in push-pull configuration.
A first embodiment of a push-pull amplifier made according to the invention comprises a first pair of active devices, such as field-effect transistors (FETs), having respective control terminals (gates) and current-carrying terminals (drains and sources). One of the current-carrying terminals of each of the active devices is coupled to a reference potential, such as a circuit or virtual ground. An input electromagnetic coupler, such as a transformer or balun, has an input primary conductor electrically coupled between the input terminal and the control terminal of a first one of the pair of active devices. An input secondary conductor is electromagnetically coupled to the input primary conductor and electrically coupled between an input reference potential and the control terminal of a second one of the pair of active devices.
An output electromagnetic coupler has a primary conductor electrically coupled between the other of the current-carrying terminals of the first active device and the output terminal. An output secondary conductor is electromagnetically coupled to the output primary conductor and is electrically coupled between the other of the current-carrying terminals of the second active device and the reference potential of the output primary conductor.
As a result, the signal on the output terminal is a combination of the signals being conducted by the pair of active devices. The pair of active devices may be formed on a single chip having separate terminals connected to the active devices which are flip-mounted onto corresponding terminals on a substrate on which the transformers or baluns are formed. The input and output transformers or baluns may also be formed as slotlines or coplanar waveguides on the substrate. Dual pairs of active devices are connected in series to form a higher power amplifier.
In a second embodiment of a push-pull amplifier made according to the invention, balanced signals in phase opposition are fed via each pair of conductors of a slotline to a corresponding pair of active devices. Pairs of such push-pull amplifiers are connected in parallel. Adjacent conductors of adjacent slotlines preferably conduct in-phase signals. When the signal applied is an unbalanced signal and the common or ground potential is applied to the outer conductors, the signal lines are shielded.
It will thus be apparent that the present invention provides a circuit which is simple and economical to construct, while providing improved operational benefits. These and other features and advantages of the present invention will be apparent from the preferred embodiments described in the following detailed description and illustrated in the accompanying drawings.
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Mohwinkel Clifford A.
Vaughan Mark J.
Anderson Edward B.
Endgate Corporation
Nguyen Khanh Van
Pascal Robert
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