Wave transmission lines and networks – Plural channel systems – Having branched circuits
Reexamination Certificate
1999-10-15
2001-11-27
Pascal, Robert (Department: 2817)
Wave transmission lines and networks
Plural channel systems
Having branched circuits
C333S101000, C333S104000
Reexamination Certificate
active
06323742
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to power combiners and splitters. It finds particular application in conjunction with impedance transforming power combiners and splitters, and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other like applications.
Impedance transformation networks arc utilized in radio frequency (“RF”) circuitry to step up or step down the impedance level between pairs of ports for input and output circuits having different source and load impedances, respectively. The impedance transformation network is typically arranged so that the load impedance provided to the input circuit by the impedance transformation network matches as nearly as possible the source impedance of the input circuit. Similarly, the network is arranged so that the source impedance provided to the output circuit by the impedance transformation network matches as nearly as possible the load impedance of the output circuit. Impedance matching is desirable since under these conditions there is a maximum power transfer and a minimum of signal distortion and/or reflection between the input and output circuits.
Power dividers and combiners are useful in a wide variety of circuits. Specific applications include combining multiple power amplifier stages in order to achieve a desired high power output. Since most solid state power devices, such as MESFETs, PHEMTs, and bipolar transistors have low input and output impedances, successive impedance transformations are often necessary to achieve 50 ohm input and output impedance levels.
There are several technologies currently available that provide power combining/splitting, including radial combiners, split lines and branch line combiners.
For example, a power combiner/splitter known as the Wilkinson power combiner/splitter offers binary combining/splitting (i.e., successive multiplications or divisions by two (2)). However, the Wilkinson power combiner/splitter is limited in that the multiplications/divisions are always by a factor of two (2). Furthermore, the input and output impedances are all equal to a characteristic impedance Z
0
. The Wilkinson design does not facilitate the use of different input and output impedances regardless of whether it is used as a combiner or a splitter. Since the Wilkinson power combiner/splitter uses quarter-wavelength lines in each multiplication/division and is binary, each multiplication/division past the first requires space for the additional quarter-wavelength lines. Moreover, the Wilkinson power combiner/splitter does not offer N-way combining.
While conventional power combining/splitting methods and apparatuses are suitable for many applications, they do not provide for selective power combining/splitting any number (e.g., N-way) of RF input signals into a single RF output.
The present invention provides a new and improved apparatus and method which overcomes the above-referenced problems and others.
SUMMARY OF THE INVENTION
A signal combiner includes a plurality of inputs receiving respective input signals. Each of the inputs has a respective input impedance. A first transforming device, having a first transforming impedance, receives a first transforming device input signal formed from at least one of the input signals. An equivalent impedance is determined as a function of a number of the inputs forming the first transforming device input signal. An output, having an output impedance, is electrically connected to the first transforming device. An output signal, which is formed as a function of the first transforming device input signal, is produced by the output. The first transforming device matches the equivalent impedance to the output impedance within an acceptable tolerance.
In accordance with one aspect of the invention, a second transforming device has a second transforming impedance. A first switch is electrically connected to at least one of the inputs. The first switch also is electrically and selectively connected to a chosen one of the transforming devices, which is determined at least as a function of the equivalent impedance and the respective impedances of the transforming devices. The output is electrically connected to the chosen transforming device.
In accordance with another aspect of the invention, a second transforming device has a second transforming impedance. Each of the transforming devices includes a plurality of transformers having respective impedances. One of the transformers in each of the transforming devices provides the respective transforming impedance. A first switch is electrically connected to one of the inputs. The first switch also is electrically and selectively connected to a first chosen one of the transformers within the first transforming device, which is determined at least as a function of the impedance of the first input and the respective impedances of the transformers within the first transforming device. A second switch is electrically connected to another one of the inputs. The second switch also is electrically and selectively connected to a second chosen one of the transformers within the second transforming device, which is determined at least as a function of the impedance of the second input and the respective impedances of the transformers within the second transforming device. The output is electrically connected to the first and second chosen transformers.
In accordance with another aspect of the invention, the plurality of inputs include four inputs. At least three of the inputs provides the respective input signals, and not a high impedance, to the first transforming device. The first transforming impedance transforms the equivalent impedance to within the tolerance of the output impedance when either one of three and four of the inputs provide the respective input signals, and not a high impedance, to the first transforming device.
One advantage of the present invention is that it provides for selectively combining any number (e.g., N-way) of RF input signals into a single RF power output.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.
REFERENCES:
patent: 5754082 (1998-05-01), Swanson
Fay Sharpe Fagan Minnich & McKee LLP
Glenn Kimberly E
Lucent Technologies - Inc.
Pascal Robert
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