Electronic circuits typically include a number of components. These components can be discrete devices, or provided as part of integrated circuits. Whether provided as discrete devices or integrated circuits, multiple electronic components are often interconnected to one another by placing those components on a common printed circuit board. In addition to providing a structural member to which components can be attached, a printed circuit board typically provides traces on one or more layers to conduct power and signals to and between attached components. When used in connection with implementing complex circuits, the design of the individual circuit boards can also become quite complex. In addition, where a large number of components are to be interconnected to a printed circuit board, the area of the board can become quite large, and a relatively large number of layers may be required to provide the necessary connective traces. In addition to providing conductive traces, certain electronic components can be integrated directly into a printed circuit board.
One consideration in the design of electronic circuits is the size of those circuits. In particular, by making devices smaller, certain performance parameters can be improved, and the device can be easier to package and transport. Also, it can be desirable to maintain electronic circuitry within size limits that are defined by certain components of a device implemented using the electronic circuitry or a component of that circuitry.
One example of electronic circuitry that can be quite complex, but that is desirably deployed within a relatively small area, is a phased array antenna. In a phased array antenna, multiple antenna elements or radiators are deployed across a surface. The size of each antenna element is generally determined by the intended operating frequency or frequencies of the antenna. Furthermore, as more antenna elements are provided, the antenna beam can be more narrowly focused and directed by applying selected phase delays to the signal comprising the beam that is delivered to (or received from) each of the antenna elements. That is, by varying the delay of a signal, the corresponding beam can be scanned along one dimension for a one dimensional array of antenna elements and along two dimensions for a two dimensional array of elements. In addition, the maximum scanning angle that can be provided by an antenna will increase as the space between antenna elements is decreased. Accordingly, the radiator or antenna elements of a phased array antenna generally occupy an area that is defined by the size of the individual antenna elements, the number of antenna elements, and the spacing between antenna elements.
Within the area defined by the antenna elements of a phased array antenna, on a side of a circuit board opposite the side on which the antenna elements are formed, circuits have been developed that allow the phase delay of two separate beams to be controlled. However, where a phased array antenna is intended for simultaneous communications with or tracking of a larger number of targets, it is desirable to increase the number of beams that can be individually controlled. This has been difficult or impossible to achieve using conventional techniques in connection with the circuit board on which the antenna elements are formed. In addition, because higher frequencies generally require a smaller antenna element, it has been especially difficult to provide supporting circuitry for systems designed to operate at high frequencies.
In order to provide the area necessary for complex beam forming networks, additional circuit boards containing components of the beam forming network can be placed behind the board on which the antenna elements are formed, for example on circuit boards arranged perpendicular to the antenna element boards. That is, the space available for circuitry can be expanded into three dimensions. Although such systems provide a place for the circuitry required to provide a number of steered beams, they do not address issues of design difficulty and ease of expansion. In particular, each board or other unit of circuitry typically includes elements that are unique to that board.