This patent application is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates to printed circuit boards for forming a diplexer circuit, more particularly but not exclusively to a diplexer circuit for a base station transceiver of a mobile communication system.
"Modern base station transceivers need to be operated at high efficiency levels to provide users of a mobile communication system with high data rate and quality services while keeping the power consumption and radiated power at a possible minimum. Therefore, power amplifiers (PA for abbreviation) and low noise amplifiers (LNA for abbreviation), building the high-frequency (HF for abbreviation) -front-end of a base station, should experience as low noise and interference as possible. One possible source of noise and interference is a potential connection or crosstalk of the transmitter branch with the PA and the receiver branch with the LNA through a commonly used antenna, i.e. parts of the transmit signal may occur in the reception branch. Therefore, respective filter circuits can be utilized to attenuate such crosstalk.
"One example of such a filter circuit is a so-called diplexer, which is a passive device that implements frequency domain multiplexing. Communication systems may us time division duplex (TDD for abbreviation) or frequency division duplex (FDD for abbreviation). In TDD, transmission and reception are separated in the time domain, i.e. for a given time either transmission or reception is carried out at the base station transceiver. In FDD, transmission and reception are separated in the frequency domain, i.e. different frequency bands are used for transmission and reception. Diplexers can be based on two band-pass filters, separating the transmission band from the reception band in an FDD system. Two ports (e.g., L and H, as abbreviations for low and high frequency band) are multiplexed onto a third port (e.g., S as abbreviation for signal), which connects an antenna or antenna system. The signals on ports L and H occupy disjoint frequency bands. Theoretically, the signals on L and H can coexist on port S without interfering with each other.
"Typically, the signal on port L may occupy a single low frequency band and the signal on port H may occupy a higher frequency band. In that situation, the diplexer can consist of a low-pass filter connecting ports L and S and a high-pass filter connecting ports H and S.
"Ideally, all the signal power on port L is transferred to the S port and vice versa, and all the signal power on port H is transferred to port S and vice versa. Ideally, the separation of the signals is complete, i.e. none of the low band signal is transferred from the S port to the H port. In the real world, some power will be lost, and some signal power will leak to the wrong port.
"The isolation between the transmit-frequency band and the receive-frequency band in a FDD radio system is a very essential performance requirement for a base station transceiver. Due to the very high sensitivity of the receiver and the relatively much larger output power, the isolation, which is usually required between these two bands may be in the order of 70, 80, 90 or even 100 dB."
In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventor's summary information for this patent application: "Embodiments can be based on the finding that such degrees of isolation are very hard to achieve and the physical arrangement of such filters may determine very much the performance of the filter-architecture and therewith of an HF-front-end. Especially in active antenna array systems, this is important, since the required level of integration of the devices is high, which means that the TX-filter and RX-filter are placed very close together, which again causes coupling between the devices, reducing the isolation.
"Embodiments provide a printed circuit board (PCB for abbreviation) for forming a diplexer circuit comprising a first connector for connecting a first filter and a second connector for connecting a second filter, wherein the first connector and the second connector are located on opposite sides of the printed circuit board. Such an embodiment may enable to arrange two filters on opposite sides of the PCB. It is a further finding that the isolation or the attenuation from one side of a PCB to the other may enable high integration level and high isolation levels at the same time. In other words, when placing the two filter circuits on opposite sides of the PCB they can be close together and well isolated from each other at the same time, so crosstalk may be suppressed to a high degree.
"The term 'connector' is to be understood as an interconnect or means for mounting electronic devices, i.e. the first or the second filter. Such a connector may be implemented as a solder-patch, which can provide mechanical support and electrical support for a filter. The connectors may enable mounting of the filters on the front side and the back side of the PCB, where the PCB is between the connectors. In embodiments solder-patches may be used to mount the filters and connect the housing of a filter to a certain voltage or reference potential. For example, the housing of a filter can be soldered to a solder patch and connected to ground potential at the same time. Embodiments may also comprise a method for manufacturing a PCB with mounting a first connector on a first side and mounting a second connector on a second side of the PCB. The connectors may be connected among each other through the PCB or to a buried ground plane within the PCB. Moreover, embodiments may comprise a method for manufacturing a diplexer circuit; such method may comprise a step of mounting a first filter on the first connector and mounting a second filter on the second connector of the PCB. These steps may comprise electrically connecting the first filter and the second filter with each other, with a buried ground plane and/or with a reference or ground potential.
"In embodiments the printed circuit board may therefore be adapted for forming a diplexer of a base station transceiver, wherein the first filter corresponds to a transmission signal filter and the second filter corresponds to a reception signal filter. The first connector may correspond to a first solder-patch and the second connector may correspond to a second solder patch. In other words, the two solder-patches may enable mechanical and electrical connection of the filters to the PCB, achieving a mechanically stable and electrically well isolated implementation of both filters in close vicinity.
"In further embodiments the printed circuit board can comprise two layers of a non-conductive substrate and a conductive layer between the two non-conductive substrate layers. The conductive layer may serve as a shielding for fringing fields and leaking currents. The conductive layer may therefore be connected to a certain potential, e.g. it may be grounded. Therefore, the conductive layer may have a connector for grounding the conductive layer. Moreover, there may be at least one connection or via between the first connector and the conductive layer. There may also be at least one connection or via between the second connector and the conductive layer. In other words, there may be an electrical connection between the two connectors and the conductive layer, so all three can be connected to a certain potential, e.g. to ground.
"The printed circuit board may further comprise another conductive layer separated from the conductive layer by an isolating layer. The conductive layer, the other conductive layer and the isolating layer can be between the two non-conductive substrate layers. In other words, there may be two conductive parallel layers in the substrate, which may be isolated from each other, in some embodiments there may be substrate between them as well. Thus, there can actually be five layers, first substrate, first conductive layer, second substrate, second conductive layer, and third substrate. The conductive layer and the other conductive layer, i.e. the first and the second conductive layer, may be parallel and forming a wave guide structure. The wave guide structure may guide electromagnetic waves, fringing fields, or leaking currents away from the two filter structures and therewith enable a higher attenuation between the two filter structures.
"The wave guide structure can be adapted to a quarter of the wavelength of a center frequency based on a transmission band determined by the first filter and a reception band determined by the second filter. In other words, there is a certain bandwidth the transmission signals may have, located around a center frequency. The wave guide structure may be geometrically adapted to a certain wavelength for which the attenuation should be raised or for which the crosstalk should be suppressed. This wavelength could correspond to the center frequency of the transmission band, the center frequency of the reception band or any other frequency in between. Basically the geometry of such a structure can be adapted to the strongest interference or crosstalk in embodiments, where the wavelength of the strongest interference may depend on the filter structures, their transfer function characteristics, etc. Embodiments may therefore be based on the finding that a conductive structure within a PCB can be geometrically adapted to a crosstalk between filter structures located on opposite sides of the PCB to suppress said crosstalk.
"The conductive layer and the other conductive layer, i.e. the first and the second conductive layer, may form a projection around the connector for the first filter and around the connector of the second filter. The conductive layer and the other conductive layer can be connected through a further connector or a via underneath the first and second connectors, wherein the projection may extend at least a quarter of the wavelength from the further connector or via. Generally, the printed circuit board may comprise any means for guiding an electromagnetic wave, the means for guiding the wave can be adapted for guiding the electromagnetic wave for at least a quarter of a wavelength of the wave. The printed circuit board may further comprise isolating means for isolating a side of the first connector from a side of the second connector to achieve attenuations for transmission band signals of more than 70, 80, 90 or 100 dB.
"Embodiments may also provide a diplexer circuit comprising an embodiment of the above circuit board, a first filter connected to the first connector for filtering a transmit signal in a transmission band, and a second filter connected to the second connector for filtering a receive signal in a reception band. The first and the second filter can be further connected to an antenna using a first feed-line and a second feed-line, wherein the first feed-line and the second feed-line can be located in parallel to the printed circuit board, or the first and the second filter are connected to the antenna using a common antenna port, wherein the printed circuit board comprises a feed connector or via for connecting the first and the second filter to the common antenna board. The diplexer may use a printed circuit board comprising two non-conductive substrate layers and at least one conductive layer between the two non-conductive substrate layers, wherein the conductive layer is adapted for providing attenuations between the transmission signal and the reception signal, which are higher than 70, 80, 90 or 100 dB.
BRIEF DESCRIPTION OF THE FIGURES
"Some other features or aspects will be described using the following non-limiting embodiments of printed circuit boards and diplexer circuits by way of example only, and with reference to the accompanying figures, in which
"FIG. 1a shows an embodiment of a printed circuit board;
"FIG. 1b shows two embodiments of diplexer circuits, each using an embodiment of a printed circuit board, one with separate and one with a common antenna port;
"FIG. 1c shows a connector of an embodiment;
"FIG. 1d shows another connector of an embodiment;
"FIG. 1e shows another embodiment of a diplexer circuit using an embodiment of a printed circuit board with a wave guide structure;
"FIG. 2a shows an embodiment of a diplexer circuit;
"FIG. 2b shows another embodiment of a diplexer circuit;
"FIG. 3a shows a diplexer circuit in a single housing; and
"FIG. 3b shows a diplexer circuit in separate housings."
URL and more information on this patent application, see: Pivit,
Keywords for this news article include: Electronics, Circuit Board,
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