Tunable microwave multiplexer

Details Tunable microwave multiplexer Tunable microwave multiplexer

2000-02-29

2004-10-19

Lee, Benny (Department: 2817)

Wave transmission lines and networks

Plural channel systems

Having branched circuits

C333S202000, C333S206000, C333S230000

Reexamination Certificate

active

06806791

ABSTRACT:

FIELD OF THE INVENTION
The invention is related to the field of tunable multiplexers. More particularly, this invention relates to a tunable multiplexer which can effectively couple ceramic or metallic resonator filters with TEM resonator filters. The multiplexer provides contiguous channel spacing and wide resonant frequency band tuning.
BACKGROUND OF THE INVENTION
Multiplexers are used to combine a plurality of channels, each centered at a different frequency, into one combined signal. The same multiplexer can be used to separate a single signal carrying many frequencies or channels into the constituent channels, each channel located at its respective frequency.
In the prior art, multiplexers have been designed by connecting bandpass filters in parallel or series to combine the plurality of channels. Relatively simple decoupling techniques work to separate the constituent channels provided that the channels are separated by frequency spacings equivalent to several passbands of the individual filters. However, when the channels of the multiplexer are too close in frequency, the interaction of the nearby channels will significantly degrade the performance of the multiplexer. Simple decoupling techniques prove ineffective at frequencies this close.
When the channels of the multiplexer are contiguous, the multiplexer should be designed as an integral unit. One method of achieving this is disclosed in the paper “A Technique for the Design of a Multiplexer Having Contiguous Channels
1
,” hereby incorporated by reference. The channel filters are connected in parallel using high
1
G. L. Matthaei and L. Young, “A Technique for the Design of Multiplexer Having Contiguous Channels,”
IEEE Trans. Microwave Theory Tech
., vol. MTT-12, pp. 88-93, January 1964. impedance coupling wire. In addition, a susceptance-anulling network using a low-impedance line added at the common port results in a nearly constant total input admittance. However, it is very difficult to design and manufacture the coupling wires needed to achieve the required couplings and low imaginary impedance over all channels or frequency bands at the common port.
The paper “A Generalized Multiplexer Theory
2
,” hereby incorporated by reference, discloses the use of a common transformer to produce planar structure duplexers, star shaped combline filters and interdigital multiplexers. However, this method is limited to use with TEM resonator structures.
2
J. D. Rhodes ad R. Levy,
IEEE Trans. Microwave Theory Tech
., vol. MTT-27, pp. 111-123, February 1979.
U.S. Pat. No. 5,262,742, hereby incorporated by reference, discloses a half wavelength transmission line used as a common resonator or common transformer. The common resonator is used to couple two combline filters to a common antenna port. However, like the method disclosed in “A Generalized Multiplexer Theory,” this method is limited to use with TEM resonator structures.
SUMMARY OF THE INVENTION
Referring now to the figures, in which like numerals refer to like elements, the present invention is shown. The invention comprises a tunable microwave multiplexer. Within the multiplexer is a plurality of channel filters comprising at least one resonator for filtering microwave and RF signals. The channel filters are coupled to a combining/dividing mechanism. The combining/dividing mechanism comprises a common port and a common resonator coupled to the common port.
In another embodiment, the invention comprises a microwave communication system comprising a receiver for receiving RF and microwave signals, a transmitter for transmitting RF and microwave signals, a signal processor coupled to the receiver and transmitter for processing signals and at least one antenna coupled to the receiver and the transmitter. Either the receiver or the transmitter can comprise a tunable microwave multiplexer. The tunable microwave multiplexer comprises a plurality of channel filters comprising at least one resonator for filtering RF and microwave signals. In addition, the multiplexer contains a combining/dividing mechanism coupled to the plurality of channel filters via coupling apertures. The combining/dividing mechanism comprises a common port and a multiple half-wavelength coaxial resonator coupled to the common port. In addition, the tunable microwave multiplexer contains transmission ports coupled to the plurality of filters.
In still another embodiment, the invention comprises a method of multiplexing a plurality of microwave channel frequencies. This method includes the steps of inputting a signal comprising a plurality of frequency channels into a common resonator. In addition, the phase difference between a common port of a common resonator to each RF port of a plurality of cavity channel filters is maintained at approximately 0 or 180 degrees. Furthermore, the signal comprising a plurality of frequency channels is separated into its constituent frequency signals. Still furthermore, at least one of said plurality of frequency channels is output.


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