1. Technical Field
This disclosure relates to transmission line filters, and more particularly, to broadband diplexers.
2. Description of the Related Art
Diplexers are well known in the electronic arts. A diplexer is a passive component that performs frequency division multiplexing between a low frequency band and a high frequency band. As such, a diplexer may include a low-pass filter and a high-pass filter. Alternatively, at least one of the filters may be implemented as a bandpass filter. Depending on how a particular diplexer is connected, it may multiplex two ports onto a single port, or may demultiplex one port onto two different ports.
A wide variety of applications exist for diplexers. For example, diplexers may be used in communications systems, e.g., to separate an incoming broadband signal into two separate broadband signals each within its own, unique range of frequencies. In another application, a diplexer may be used to combine signals on an input to a wideband oscilloscope in, e.g., a laboratory environment.
A hybrid diplexer implemented using both planar transmission lines and waveguides is disclosed. In one embodiment, a diplexer includes an input configured to receive a broadband signal, a low-pass filter, and a high-pass filter. The low-pass filter may be implemented using a planar transmission line. The high-pass filter may be implemented using a waveguide. Accordingly, as disclosed herein, a planar transmission line and a waveguide are implemented within a single diplexer.
In one embodiment, a method includes receiving a broadband signal at an input of a diplexer. The method further includes low-pass filtering the broadband signal using a low-pass filter implemented in the diplexer using a planar transmission line. The method further includes high-pass filtering the broadband signal using a high-pass filter implemented in the diplexer using a waveguide.
Another embodiment of a diplexer includes first, second, and third ports to provide interfaces to the external world. A first signal path is implemented between the first port and the second port, using a planar transmission line. A second signal path is implemented between the first port and the third port using a waveguide.
In general, a diplexer as implemented herein includes a low frequency signal path implemented using a planar transmission line. The low frequency signal path does not include any portion implemented as a waveguide. The diplexer as implemented herein also includes a high frequency signal path implemented as a waveguide. A portion of the high frequency signal path may include a planar transmission line(s), which may be used as a transitional medium between a port or ports coupled to the high frequency signal path and the waveguide. In one embodiment, the various ports may be implemented using coaxial transmission lines. However, an embodiment is also possible and contemplated wherein a port coupled to the high frequency signal path is a waveguide port (e.g., a waveguide output).
Other aspects of the disclosure will become apparent upon reading the following detailed description and upon reference to the accompanying drawings, which are now described as follows.
While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and description thereto are not intended to be limiting to the particular form disclosed, but, on the contrary, is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include”, “including”, and “includes” mean including, but not limited to.
Various units, circuits, or other components may be described as “configured to” perform a task or tasks. In such contexts, “configured to” is a broad recitation of structure generally meaning “having circuitry that” performs the task or tasks during operation. As such, the unit/circuit/component can be configured to perform the task even when the unit/circuit/component is not currently on. In general, the circuitry that forms the structure corresponding to “configured to” may include hardware circuits. Similarly, various units/circuits/components may be described as performing a task or tasks, for convenience in the description. Such descriptions should be interpreted as including the phrase “configured to.” Reciting a unit/circuit/component that is configured to perform one or more tasks is expressly intended not to invoke 35 U.S.C. §112, paragraph six interpretation for that unit/circuit/component.
Turning now to
In one embodiment, coaxial port 11 may be used as an input, while coaxial ports 13 and 15 are used as outputs. Moreover, first signal path 12 may implement a low-pass filter constructed of a planar transmission line. The planar transmission line may be a suspended strip line (SSL) in one embodiment, but may be implemented as a microstrip transmission line in another embodiment. The second signal path 14 may implement a high-pass filter using the waveguide. In one embodiment, the waveguide may be a transverse electric (TE) mode E-plane waveguide.
The respective ranges of signal frequencies passed by the low-pass and high-pass filters may be non-overlapping in some embodiments, with the low cutoff frequency of the high-pass filter being greater than the high cutoff frequency of the low-pass filter. In another embodiment, the respective ranges of signal frequencies passed by the low- and high-pass filters may overlap or coincide, and thus the diplexer may pass signals from an overall larger contiguous range of frequencies.
It is noted that the second signal path 14 may in some embodiments include some planar transmission lines to couple the waveguide to coaxial ports 11 and 15. However, these planar transmission lines are arranged in such a manner to pass as much of the spectrum of a received signal as possible to the waveguide of second signal path 14, as will be explained in further detail below.
While the embodiment shown in
Diplexer 10 in the embodiment shown is an assembly of components A, B, C, D, and E, each of which will be discussed in further detail below. When assembled as shown, diplexer 10 is an ultra-broadband diplexer that includes a first signal path implemented using one or more planar transmission lines, and a second signal path that is implemented at least in part using a waveguide. The first signal path does not include any waveguide portions, and thus diplexer 10 combines a waveguide path and a planar transmission line path in the same unit. The first signal path may be used to convey signals in a lower frequency band, while the second signal path may convey signals in an upper frequency band. For example, in one embodiment, a first signal path may implement an ultra-wideband low-pass filter capable of passing signals in a range of frequencies from 0 Hz to 35 GHz, while the second signal path may implement an ultra-wideband filter capable of passing signals in a frequency range from 35 GHz up to at least 65 GHz. Thus, the overall frequency response of such an embodiment is within a contiguous range of frequencies from 0 Hz up to at least 65 GHz. It is noted however that the overall frequency range for other embodiments is not necessarily contiguous, and thus the upper cutoff frequency of the low-pass filter may be less than the lower cutoff frequency of the high-pass filter. Embodiments in which bandpass filters are implemented with one or both signal paths are also possible and contemplated, and the overall frequency range passed by the two paths collectively may or may not be contiguous, depending on the specific implementation.
Section 30 of the planar transmission line in the embodiment shown is coupled to a section 31 of the planar transmission line. Section 31 includes a number of stubs extending perpendicularly from the main axis thereof, and thus implements a wideband low-pass filter. Section 30 is not implemented as a low-pass filter, instead passing as much energy across the spectrum of a received signal as possible. Sections 30 and 31 in the embodiment shown are implemented within printed circuit board 35. At the junction of sections 30 and 31, a waveguide stub 25 extends into waveguide backshort portion 23. Thus, waveguide stub 25 is a transition point from planar transmission line 30 to waveguide in this embodiment of diplexer 10.
The implementation of both planar transmission lines and a waveguide in diplexer 10 may provide allow a wider range of frequencies to pass compared to diplexers that are implemented exclusively with planar transmission lines or exclusively with waveguides. A diplexer implemented exclusively with waveguides is not capable of reaching the lower frequencies all the way down to DC (0 Hz). Diplexers implemented exclusively with planar transmission lines may be unable to efficiently pass some of the higher frequencies that may otherwise pass through a waveguide. Nevertheless, implementation of a hybrid waveguide/planar transmission line diplexers as discussed herein may present challenges in terms of mechanical design and packaging that are not present with prior art diplexers. Accordingly, various embodiments of diplexer 10 as discussed herein overcome the problems of combining the two approaches, waveguide and planar transmission line, while providing the advantages of both.
Turning now to
While the above embodiments have been discussed in terms of a diplexer, similar embodiments implemented as a tri-plexer, quad-plexer, etc., are possible and contemplated. In general, the discussion herein may be applied to splitters and combiners of any number of inputs/outputs that include at least one signal path implemented primarily using planar transmission lines and at least one signal path implemented primarily using a waveguide.
Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.
Number | Name | Date | Kind |
---|---|---|---|
3879690 | Golant et al. | Apr 1975 | A |
4498061 | Morz et al. | Feb 1985 | A |
6008706 | Holme et al. | Dec 1999 | A |
6917256 | Emrick et al. | Jul 2005 | B2 |
7332982 | Yun et al. | Feb 2008 | B2 |
20060145782 | Liu et al. | Jul 2006 | A1 |
20070139135 | Ammar et al. | Jun 2007 | A1 |
20110254640 | Gehring et al. | Oct 2011 | A1 |
20130002373 | Robert et al. | Jan 2013 | A1 |
Number | Date | Country |
---|---|---|
1170818 | Sep 2002 | EP |
1492194 | Dec 2004 | EP |
Entry |
---|
Rehner, R., et al.; “A Quasi-Lumped Ultra-Broadband Contiguous SSL-Diplexer from DC to 80 GHz”; Microwave Symposium Digest, 2009; Jun. 7-12, 2009; MTT '09; IEEE MTT-S International; pp. 1037-1040. |
Manchec, A., et al; “High Rejection Planar Diplexer on Liquid Crystal Polymer Substrates Using Oversizing Techniques”; Microwave Conference, 2005 European (vol. 1); Oct. 4-6, 2005; 4 pages. |
Menzel, W., et al.; “Planar Integrated Waveguide Diplexer for Low-Loss Millimeter-Wave Applications”; Microwave Conference, 1997; 27th European (vol. 2); Sep. 8-12, 1997; pp. 676-680. |
Number | Date | Country | |
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20150077195 A1 | Mar 2015 | US |