Switchable combiner/splitter

Details Switchable combiner/splitter Switchable combiner/splitter

1998-07-01

2001-06-26

Ton, Dang (Department: 2832)

Multiplex communications

Pathfinding or routing

Through a circuit switch

C333S017300

Reexamination Certificate

active

06252871

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates generally to high power, high frequency RF signal manipulation, and in particular to a combiner/splitter for handling high power RF signals.
Switched power combiners for operation at RF frequencies are well known in the art. These units provide the capability of combining the output of several preferably coherent, in phase, signal sources to achieve a higher combined output power. For purposes of this description, it is assumed that all of the signals sources are in phase.
The goal of any design of an N-way power combiner (where N is any positive integer) is to be able to combine the signals on the various input lines, having coherent sources, with little or no penalty due to insertion loss or input VSWR, regardless of how many of the inputs are selected at any given time.
In order to achieve this result, many known configurations have been developed for providing switching along with low insertion loss. Thus, for example, a simple circuit such as that illustrated in
FIG. 1
provides a plurality of switched half-wave coaxial transmission lines having a common summing point and connected from that point, through a half-wavelength line to an output. The half-wave-length lines are often implemented as two quarter wave length transmission lines connected in series. Such switchable configurations, however, are typically tuned for a known number of closed switches. As different numbers of switches are closed, the impedance seen at the summing point varies and substantial insertion losses, due to mismatches, can be incurred.
Various techniques have been used to ameliorate this problem so that, for example, different numbers of closed switches will all incur some, but not a lot, of insertion loss.
In one practical application, for example where a cellular base station is provided, it is desirable to use only one signal input source initially and to add additional sources as the volume of calls and users increases. In this situation, the addition of new sources can also require a complete retuning of the combiner, or even its replacement. This is an inconvenience not easily tolerated. Further if a source should fail, its removal could cause a significant power loss, due to mismatching, far beyond the loss of the source itself.
As a result, therefore, it would be desirable to enable hot switching of RF sources without adversely affecting the impedance match of other sources. It is also desirable to provide the ability to vary the number of sources without having to remove or replace the combiner.
SUMMARY OF THE INVENTION
The invention relates to an apparatus and method for combining or splitting a plurality of high frequency RF signal inputs. The combining apparatus features a first combining section for switchably combining selected ones of the RF signal inputs and providing a common signal output. The apparatus further features a switchable matching section connected at its input to the common signal output and switchably inserting matching lines between its input and its own output. The switchable matching section is able, by a selected switch pattern, to substantially match the impedance presented to it by the common signal output. Thus, as the RF inputs to the first combining section can be switchably changed, so the matching section can be switchably changed in accordance therewith to minimize and substantially eliminate insertion loss through the combiner apparatus.
The method for combining a plurality of high frequency RF signal inputs features the steps of switchably combining selected ones of the RF signal inputs and providing a common summed signal output, switchably inserting matching lines between the common summed signal output and a combined output for matching the impedance presented by the switchably combined signal inputs, and switchably inserting the matching lines in correspondence to switchably combining the RF signal inputs to provide a minimized insertion loss from the RF signal inputs to a combined output.
The apparatus for splitting a high frequency RF signal input into a plurality of RF signal outputs features a splitting section for switchably splitting an RF signal input from the output of a matching section, a switchable matching section connected at its input to the high frequency RF signal input and able to switchably insert matching lines between its input and its output, the switchable matching section being able, by a selected switch pattern, to substantially match the impedance presented to it by the splitting section, whereby the number of RF outputs from the splitting section can be switchably changed, and the matching section can be switchably changed to minimize insertion loss through the splitting apparatus.
The method for splitting a high frequency RF signal input features the steps of splitting selected ones of the RF signal inputs from the common summed signal output, switchably inserting matching lines between a common summed signal output and the RF signal input for matching the impedance presented by a splitting section, and switchably inserting the matching lines in correspondence to switchable splitting of the RF signal input to provide a minimized insertion loss from the RF signal input to split the outputs.
Advantages of the invention include a minimization or elimination of insertion loss by enabling a matching section to be switchably configured to the combining/splitting section.
Other advantages of the invention are the convenience of enabling hot swamping without adversely affecting the combining/splitting of other RF input signals, and the ability to “grow” a system without the need for revising or replacing the combiner/splitter apparatus.


REFERENCES:
patent: 4315222 (1982-02-01), Saleh
patent: 4472691 (1984-09-01), Kumar et al.
patent: 5179332 (1993-01-01), Kang
patent: 5304943 (1994-04-01), Koontz
patent: 5661434 (1997-08-01), Brozovich et al.
patent: 5754082 (1998-05-01), Swanson
patent: 5867060 (1999-02-01), Burkett, Jr. et al.
patent: 5872491 (1999-02-01), Kim et al.

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