Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-03-09
2001-12-11
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S702000, C343S841000, C333S202000
Reexamination Certificate
active
06329949
ABSTRACT:
TECHNICAL FIELD
This invention relates to the structure and manufacturing of wireless transmitters and/or receivers.
BACKGROUND OF THE INVENTION
Transmitter and/or receiver (henceforth referred to generically as “transceiver”) technology has evolved over the decades from the use of wires, electro-mechanical components, and machined waveguide structures to the use of coax and thick film/thin film microstrip/stripline-based circuitry. But even with this evolution, the recent proliferation of, and resulting stiff competition among, wireless communications products have led to price/performance demands on transceivers that conventional technologies find difficult to meet. A transceiver conventionally comprises a protective enclosure, an antenna, “front end” filters (e.g., a duplexer), amplifiers and other transceiver circuitry, and connectors and cabling. The most expensive components typically are the antenna, the filters, and the amplifiers. To permit obtaining these components from different sources, to permit easy interconnection of these components, and to permit easy testing and alignment, the electrical interfaces between the components have been standardized at 50&OHgr; and are generally made via 50&OHgr; coaxial cables and connectors. These components not only add to the cost of the transceiver, but also reduce the overall performance thereof. Moreover, the impedance conversion required to achieve 50&OHgr; adds cost and degrades the performance of the active components of the transceiver.
High-volume manufacturing techniques have been used to reduce the costs of some conventional antennas and filters. However, these techniques do nothing to improve the performance of these components, nor do they improve the costs of low- and medium-volume components. Moreover, they do nothing to reduce the amount and the cost of cabling and connectors between the antenna and the filters. Others have sought to reduce the cost of antennas and filters at the expense of other parts of the transceiver; essentially, by shifting the cost to these other parts. One example is replacing standard front-end components with ones that have a better performance to make up for the poor performance of cheap antennas and filters, such as replacing the low-noise pre-amplifier (LNA) with one that has a lower noise figure and a higher dynamic range (i.e., higher 1-dB compression or higher third-order intercept (TOI)), or replacing the output power amplifier (PA) with one that has a higher output power. The problem with these approaches is that they merely transfer the cost to another area of the transceiver without substantially lowering the cost of the transceiver as a whole. In fact, they generally increase the complexity and the cost of the transceiver.
SUMMARY OF THE INVENTION
This invention is directed to solving these and other problems and disadvantages of the prior art. Generally according to the invention, the antenna and the “front end” filters of a transceiver are integrated into a single multi-layer structure that decreases complexity and transceiver cost and improves transceiver performance. The transceiver is constructed as a stacked assembly of its constituent parts, with some parts performing “double duty” in the assembly, thereby decreasing its complexity and cost. For example, the antenna and “front-end” filters of the transceiver are integrated into one metal laminate assembly such that shielding of the filter forms a ground plane of the antenna, thereby decreasing transceiver complexity and cost. Moreover, the assembly is simple and inexpensive to put together, and at the same time improves transceiver performance. Preferably, the circuit board that carries the transceiver circuitry is also integrated into the structure such that the shielding of the filter forms both a mount for the circuit board and a shield for the circuitry.
Specifically according to the invention, a transceiver stacked assembly comprises at least four layers: a first layer that forms an antenna, a third layer that forms one or more “front-end”, or radio frequency (RF) filters, a second layer interposed between the antenna and the filters that forms a ground plane of the antenna as well as a part of an electrical isolation enclosure for the filter, and a fourth layer that together with the second layer forms the electromagnetic isolation enclosure of the filter. The layers are stacked next to (“on top of”) each other and are preferably epoxied, soldered, or welded together. Each layer preferably comprises a single metal layer. Illustratively, the first layer including the antenna is stamped out of a single sheet of metal, as is the third layer including the filters. Also, each layer preferably has a cake-pan shape, forming walls that both space the rest of the layer from an adjacent layer and mount the layer on the adjacent layer. The filters and the antenna are conductively or capacitively interconnected in a connectorless manner—illustratively by flanges that extend through orifices in the second layer and that are preferably made integrally with the filters or the antenna—thus eliminating the use of conventional connectors and cables. Further preferably, a fifth layer that defines the electronic circuitry of the transceiver, such as a printed circuit board with electronic components mounted thereon, is mounted to and electromagnetically shielded by the fourth layer. The electronics and the filters are conductively or capacitively connected together by flanges that extend through orifices in the fourth layer and that are preferably made integrally with the filters, again eliminating the use of conventional connectors and cables.
The invention has numerous benefits. For example, designing the antenna and filters as one common assembly (one unit) introduces design options or degrees of freedom not possible with separate, discrete, antennas and filters. To illustrate, the filters and the antenna need not have a 50&OHgr; input and output impedance; rather, the impedance can be whatever yields the best performance, since both the antenna and filter performance are under control of the same designer. Also, the connection from the filters to the radio need not be 50&OHgr;, but can be separately optimized to a non-50&OHgr; impedance to advantageously match to a particular design. Furthermore, functions (e.g., the combiner) that are normally associated with the duplexer can be designed into the antenna, and vice versa. The invention yields lower losses and improved performance than conventional designs, due to the all-metal design. The noise figure of the transceiver can likewise be improved. Elimination of connectors and cabling between the antenna, filter, and PC board also reduces transceiver costs and increases transceiver reliability. Also, precise control of the interconnection leads to better performance. Moreover, the integrated antenna and filter assembly can be manufactured more easily, as one unit. On balance, the invention yields a transceiver with fewer parts, a simpler mechanical structure, fewer manufacturing steps, and easier assembly.
These and other features and advantages of the invention will become more apparent from the following description of an illustrative embodiment of the invention considered together with the drawing.
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Barnett Ron
Korisch Ilya Alexander
Ma Zhengxiang
Schwartz Richard F
Wu Hui
Avaya Technology Corp.
Phan Tho
Volejnicek Davik
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