Switch matrix for electromagnetic imaging

Abstract

Apparatus for electromagnetic imaging and switch matrices are disclosed. The switch matrix can include a transmission port couplable to an RF measurement unitto receive an electromagnetic transmission signal, a reception port couplable to the RF measurement unit to transmit an electromagnetic reception signal, a plurality of transceiver ports couplable to transceivers positioned around a subject; and a plurality of PCB layers arranged in a stack, and a control port couplable to a controller for receiving at least one control signal. The PCB layers include a reception layer, a transmission layer, and at least four intermediate layers between the transmission layer and the reception layer. At least two intermediate layers are electrically grounded to provide radio frequency isolation between the transmission and reception layers. The transmission and reception layers includes a plurality of switches. The at least one control signal controls the plurality of switches in a plurality of operating states.

Description

SWITCH MATRIX FOR ELECTROMAGNETIC IMAGINGField

[0001] The described embodiments relate to electromagnetic imaging, and in particular, to systems and apparatus for electromagnetic imaging.Background

[0002] Early stroke detection is one of the most successful preventative strategies for reducing long-term impairments. Strokes can be reliably detected by computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). However, these conventional imaging methods are costly, not widely accessible and tend to be stationary (i.e., not readily transportable).

[0003] Electromagnetic (EM) imaging techniques can involve an array of sensors equipped with multiple transmitting and receiving antennas encircling the subject under examination. Algorithms for electromagnetic imaging rely on the data obtained from measuring electromagnetic signals. The electromagnetic signals can be determined simultaneously for a transmitting sensor and all receiving sensors, or sequentially using a time-division approach. The simultaneous approach can be costly and cumbersome, or compromise the accuracy of some measured signals.

[0004] The time-division approach uses a switch matrix to alter the paths for transmission and reception, enabling one sensor to transmit a radio frequency (RF) signal within the desired frequency band while another sensor receives the RF signal during each time slot. Despite its conventional use, the switch matrix has several challenges.

[0005] When conducting brain imaging, it is typically advantageous, to utilize a considerable number of sensors. However, a higher number of sensors necessitates a larger switch matrix. Regrettably, switch matrices are inherently large and have predetermined physical dimensions, impacting the overall size and weight of the system.Summary

[0006] The various embodiments described herein generally relate to electromagnetic imaging apparatus. A switch matrix for electromagnetic imaging includes: a transmission port couplable to an advanced radiofrequency (RF) measurement unit such as Network Analyzer or other time or frequency RF measurement unitto receive an electromagnetic transmission signal; a reception port couplable to the advanced RF measurement unitto transmit an electromagnetic reception signal; a plurality of transceiver ports couplable to a plurality of transceivers positioned around a subject; and a plurality of printed circuit board (PCB) layers arranged in a stack, and a control port couplable to a controller for receiving at least one control signal. The plurality of PCB layersinclude a reception layer, a transmission layer, and at least four intermediate layers between the transmission layer and the reception layer. At least two intermediate layers of the at least four intermediate layers are electrically grounded to provide radio frequency isolation between the transmission layer and the reception layer. The transmission layer includes a plurality of transmission switches. The reception layer includes a plurality of reception switches. The at least one control signal controls the plurality of transmission switches and the plurality of reception switches in a plurality of operating states. In each operating state of the plurality of operating states, the plurality of transmission switches are operable to provide one transmission path for the electromagnetic transmission signal from the transmission port to a first transceiver port of the plurality of transceiver ports; and the plurality of reception switches are operable to provide one reception path for the electromagnetic reception signal from a second transceiver port of the plurality of transceiver ports to the reception port.

[0007] In some embodiments, the reception layer can be at a top of the stack and the transmission layer is at a bottom of the stack.

[0008] In some embodiments, the transmission layer can be at a top of the stack and the reception layer is at a bottom of the stack.

[0009] In some embodiments, in each operating state of the plurality of operating states, at least one of the transmission path or the reception path is different from the transmission path and the reception path of other operating states of the plurality of operating states.

[0010] In some embodiments, the transmission port can be disposed on the transmission layer.

[0011] In some embodiments, the plurality of transmission switches can be grouped in a plurality of sequential transmission stages. The plurality of transmission stages can include a first transmission stage and one or more subsequent transmission stages. The first transmission stage can include one transmission switch. Each subsequent transmission stage can include a plurality of transmission switches.

[0012] In some embodiments, the reception port can be disposed on the reception layer.

[0013] In some embodiments, the plurality of reception switches can be grouped in a plurality of sequential reception stages. The plurality of reception stages can include a last reception stage and one or more preceding reception stages. The last reception stage can include one reception switch. Each preceding reception stage can include a plurality of reception switches.

[0014] In some embodiments, the plurality of transceivers can include 2ntransceivers.

[0015] In some embodiments, the plurality of transceivers can include at least 8 transceivers.

[0016] In some embodiments, the plurality of transceivers can include at least 128 transceivers.

[0017] In some embodiments, the plurality of transceiver ports can be disposed along a perimeter of the switch matrix.

[0018] In some embodiments, the switch matrix can include an integrated PCB.

[0019] In some embodiments, the switch matrix can include a plurality of distributed PCBs connected together.

[0020] In some embodiments, the switch matrix can be planar.

[0021] In some embodiments, the switch matrix can be dome-shaped.

[0022] In some embodiments, the switch matrix can be operable in a frequency range of about20 MHz to about 10 GHz.

[0023] In some embodiments, in each operating state of the plurality of operating states, the reception path can be isolated from the transmission path by at least 90 decibels in a frequency range of about 20 MHz to about 10 GHz.

[0024] In some embodiments, the switch matrix can further include one or more insulation layers within the stack.

[0025] In some embodiments, the switch matrix can further include at least one insulation layer between each pair of PCB layers within the stack.

[0026] In some embodiments, the insulation layers can be formed of at least one of a substrate, a prepreg, a core, or a non-conductive material.

[0027] In some embodiments, the at least four intermediate layers can include at least one power and control layer for transmitting power and the at least one control signal to the plurality of transmission switches and the plurality of reception switches.

[0028] In some embodiments, each PCB can include one or more of a standard PCB, a flexible PCB, a rigid-flexible PCB, or a combination thereof.

[0029] In some embodiments, each switch of the plurality of transmission switches and the plurality of reception switches can be a 2x1 , 4x1 , or 8x1 solid-state switch.

[0030] In some embodiments, the switch matrix can further include electromagnetic shielding around the switch matrix.

[0031] In some embodiments, the electromagnetic shielding can include at least two layers of electromagnetic shielding material.

[0032] In some embodiments, the electromagnetic shielding can include the switch matrix being positioned between at least two containers.

[0033] In some embodiments, each container can be a metallic container or a non-metallic container coated with a metallic material.Brief Description of the Drawings

[0034] Several embodiments will be described in detail with reference to the drawings, in which:

[0035] FIG. 1 is a block diagram illustrating an example electromagnetic imaging system, in accordance with an example embodiment;

[0036] FIG. 2 is a schematic diagram illustrating an example plurality of transceivers positioned around a subject, in accordance with an example embodiment;

[0037] FIG. 3 is a schematic diagram illustrating components of an example electromagnetic imaging system, in accordance with another example embodiment;

[0038] FIG. 4 is a schematic diagram illustrating a cross-sectional view of an example PCB stack implementation of an example switch matrix, in accordance with another example embodiment;

[0039] FIG. 5A is a top view of an example switch matrix, in accordance with another example embodiment;

[0040] FIG. 5B is a bottom view of the example switch matrix of FIG. 5A;

[0041] FIG. 5C is a top perspective view of the example switch matrix of FIG. 5A;

[0042] FIG. 5D is a side view of the example switch matrix of FIG. 5A;

[0043] FIG. 6A is a top view of an example interface controller, in accordance with an example embodiment;

[0044] FIG. 6B is a bottom view of the example interface controller of FIG. 6A;

[0045] FIG. 6C is a top perspective view of the example interface controller of FIG. 6A;

[0046] FIG. 6D is a side view of the example interface controller of FIG. 6A;

[0047] FIG. 7 is a perspective view of an example electromagnetic head imaging device, in accordance with an example embodiment; and

[0048] FIG. 8 is a perspective view of another example electromagnetic head imaging device with a distributed switch matrix, in accordance with another example embodiment.

[0049] The drawings, described below, are provided for purposes of illustration, and not of limitation, of the aspects and features of various examples of embodiments described herein. For simplicity and clarity of illustration, elements shown in the drawings have not necessarily been drawn to scale. The dimensions of some of the elements may be exaggerated relative to other elements for clarity. It will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements or steps.Description of Example Embodiments

[0050] The various embodiments described herein generally relate to electromagnetic imaging, and system and apparatus for electromagnetic imaging.

[0051] Medical imaging using electromagnetic techniques can involve employing an array of sensors equipped with multiple transmitting and receiving sensors encircling the subject under examination. The number of sensors can be denoted as N (where N>1). The sensors can be arranged in either two-dimensional or three-dimensional configurations. The sensors can be used to measure electromagnetic signals. Data obtained from measuring electromagnetic signals can be used for tomography imaging algorithms.

[0052] The electromagnetic signals can be determined simultaneously for a transmitting sensor and all receiving sensors, or the electromagnetic signals can be computed sequentially using a time-division approach. With the simultaneous approach, an advanced radiofrequency (RF) measurement unit can include a multiport Vector Network Analyzer (VNA) or integrated transmitter and receiver (i.e., transceiver) components within each sensor. However, the multiport VNA can be both costly and cumbersome, while the embedded transceiver can compromise the accuracy of reflection electromagnetic signals.

[0053] The time-division approach typically involves a 2-port advanced RF measurement unit coupled to a 2xN-port switch matrix, where two ports of a first side of the switch matrix are coupled to the two ports of the advanced RF measurement unit. The remaining N ports of the second side of the switch matrix are coupled to the N sensors. The switch matrix can then cyclically alter the paths for transmission and reception, enabling one sensor to transmit a radio frequency signal within the desired frequency band while another sensor receives it during each time slot.

[0054] With medical imaging of the brain, it is typically advantageous to utilize a considerable number of sensors. However, a higher number of antennas necessitates a larger switch matrix. However, switch matrices can inherently be large and have predetermined physical dimensions, which can significantly impact the overall size and weight of the system. Additionally, the sequential approach can lack scalability. For example, when additional antennas are required, the switch matrix can require redesign with increasingly complex configurations.

[0055] For electromagnetic imaging, the sensors can be immersed in matching media. The matching media can have dielectric properties similar to that of the average human brain tissues. The material of both the matching media and the human brain can be highly lossy. Thus, there is a decrease in magnitude of the transmitted signals. The attenuation, in turn, requires the use of high Radio Frequency (RF) isolation switch matrices. High RF isolation switch matrices are usually electromechanical switches. The electromechanical switches can have long switching times. When the measurements are carried out sequentially, a separate measurement must be carried out for each combination of transmitting and receiving sensors. Thus, for example, if all possible measurements are made in a system with 128 sensors and the switching time for each state be 10 milliseconds, there are a total of 128 x 128 measurement periods which require a total measurement time of 128 x 128 x 10 milliseconds, which totals around 3 minutes. Operation of the switch matrix to adjust control from one pair of sensors to another requires still further time. Unfortunately, it is difficult for the human body to remain completely free of movement for several minutes. Taking measurements over such a long period of time inevitably introduces additional "movement" noise into the results.

[0056] In some EM imaging systems, the antenna of sensors can be immersed in the matching media. The antenna can have a fixed position around the human head. The space between the antenna and human head can attenuate the transmitted signals. Also the matching media can act as a coupling channel and increase the noise level in the receiver sides. In this structure, the sensitivity of received sensors and microwave circuit should be high to compensate for the attenuation in the matching media. Thus, the RF isolation level in switch matrix and RF measurement unit dynamic range should be high for the time-division approach. In this way, the switch matrix should be electromechanical, which is bulky, heavy, and expensive.

[0057] On the other hand, in some structures, the sensors can fit the human head and the sensitivity of receiver sides can decrease to around -90 dBm when the transmitter sensor has power around 0 dBm. Therefore, for the time-division approach, the switch matrix isolation level and the RF measurement unit dynamic range can be around 90dB. In this way, the switch matrix can be developed with solid-state RF switches. This design can be compact, light, and low-cost.

[0058] Referring now to FIG. 1 , shown therein is a block diagram 100 illustrating components of an example electromagnetic imaging system 110. The system 110 can include an image processing unit 122, a control unit 124, an advanced RF measurement unit 126, a switch matrix 130, an interface controller 128, and a plurality of transceivers 120a, 120b, ... 120n (collectively referred to herein as transceivers 120). As shown, the system 110 can include any number of transceivers 120.

[0059] System 110 can be based on a sequential time-division approach or other time or frequency RF measurement unit. The RF measurement unit 126 can be a vector network analyzer (VNA). Although one bidirectional arrow is shown in FIG. 1 between the RF measurement unit126 and the switch matrix 130, with a sequential time-division approach, the RF measurement unit 126 can have two ports, namely an input port and an output port. Further, the switch matrix 130 can be a 2xN device, where N is greater than 1.

[0060] The interface controller 128 can control the switch matrix 130 and the transceivers 120. The control unit 124 can control the RF measurement unit 126 and the interface controller 128 to collect data from the transceivers 120 from a subject. The data can be any type of electromagnetic signals, which can be used to construct an image of the subject. The electromagneticdata can be sent to the image processing unit 122 to construct the image of the subject.

[0061] Referring now to FIG. 2, shown therein is a schematic diagram 200 illustrating an example plurality of transceivers 220Ra, 220Rb, 220Rc, 220Ta, 220Tb, and 220Tc (collectively referred to herein as transceivers 220) positioned around a subject 202. The transceivers 220 can collect electromagnetic data from the subject 202. The transceivers 220 can be transceivers 120 of system 110. Although FIG. 2 shows six transceivers 220, any number of transceivers can be positioned around the subject 202 to collect electromagnetic data.

[0062] As shown in FIG. 2, each transceiver 220Ra, 220Rb, 220Rc, 220Ta, 220Tb, and 220Tc can include a matching media 226Ra, 226Rb, 226Rc, 226Ta, 226Tb, and 226Tc (collectively referred to as matching media 226) proximal to the subject 202. The matching media 226 can be flexible to allow it to conform to the shape of the subject 202. In some embodiments, the matching media 226 can be approximately 5 millimeters (mm) thick.

[0063] Each transceiver 220 can also include an antenna 224Ra, 224Rb, 224Rc, 224Ta, 224Tb, and 224Tc (collectively referred to as antennas 224) and a microwave circuit 222Ra, 222Rb, 222Rc, 222Ta, 222Tb, and 222Tc (collectively referred to as microwave circuits 222). The microwave circuits 222 and antennas 224 can be operable in different modes. For example, the microwave circuits 222 can operate as a transmitter to transmit an electromagnetic signal. In addition, the microwave circuits 222 can operate as a receiver with a low noise amplifier to receive an electromagnetic signal and to amplify the received electromagnetic signal.

[0064] In some embodiments, the microwave circuits 222 can have a frequency band of approximately 1 gigahertz (GHz) to 2 gigahertz (GHz). In some embodiments, the frequency band can be extended to frequencies greater than 2 GHz. For example, the frequency range can be about 1 GHz to about 10 GHz. In some embodiments, the frequency band can be extended to frequencies lower than 1 GHz. For example, the frequency range can be about 20 MHz to about 10 GHz.

[0065] Pairs of the transceivers 220 positioned opposite to one another around the subject 202 can be operable together. For example, in a first instance, transceivers 220Ta can be operable as a transmitter while transceiver 220Ra can be operable as a receiver. Similarly, 220Tband 220Tc can be operable as transmitters while transceivers 220Rb and 220Rc can be operable as receivers. In another instance, transceivers 220Ra, 220Rb, and 220Rc can be operable as transmitters while transceivers 220Ta, 220Tb, and 220Tc can be operable as receivers.

[0066] The transceiver 220Ta can transmit an electromagnetic wave to the subject 202. The electromagnetic wave can be attenuated by the subject 202. The receiver 220Ra can receive the attenuated electromagnetic wave corresponding to the electromagnetic wave transmitted by the transmitter 220Ta.

[0067] Referring now to FIG. 3, shown therein is a schematic diagram 300 illustrating components of an example electromagnetic imaging system 310, in accordance with some embodiments. Similar to system 110, system 310 can include a plurality of transceivers 320a, 320b, ... 320n-1 , 320n (collectively referred to as transceivers 320) positioned around a subject 302, a switch matrix 330, and an advanced RF measurement unit 326. Although not shown, system 310 can also include a control unit and image processing unit, similar to control unit 124 and image processing unit 122, respectively.

[0068] As shown in FIG. 3, the switch matrix 330 can have a first side A and a second side B. The first side A can be coupled to the RF measurement unit 326. The first side A can have two ports, a transmission port A_1 and a reception port A_2. The transmission port A_1 can be coupled to the RF measurement unit 326 to receive an electromagnetic transmission signal from the RF measurement unit 326. The reception port A_2 can be coupled to the RF measurement unit 326 to transmit an electromagnetic reception signal to the RF measurement unit 326.

[0069] The second side B can be coupled to the transceivers 320. The second side B can have any plurality of transceiver ports, B_1 , B_2, ... B_N-1 , and B_N. Each of the plurality of transceiver ports can be coupled to a corresponding transceiver of the plurality of transceivers 320 positioned around the subject 302.

[0070] The switch matrix 330 can have multiple, sequential stages 332a, 332b, 332c, 332d, 332e, ... 332n, 332n+1 (collectively referred to as stages 332). The multiple stages are between the first side A and the second side B. Each stage can have a corresponding number of solid- state switches.

[0071] Each stage can include a plurality of 2x1 , 4x1 , or 8x1 RF switches. Theswitches can be solid state switches. In particular, each stage can have 2nswitches that are 2x1 . In the example shown in FIG. 3, a first stage 332a has 2 2x1 switches (n=1); a second stage 332b has 4 2x1 switches (n=2), a third stage 332c has 8 2x1 switches (n=3), a fourth stage 332d has 16 2x1 switches (n=4), and a fifth stage 332e has 32 2x1 switches (n=5). Further, stage 332n and a last, or terminal stage 332n+1 can have 2n+12x1 switches. The number of switches of each of stage 332n and the last stage 332n+1 can correspond to the number of ports on the second side B.

[0072] Half of the 2x1 switches in each stage of stages 332a to 332n provide RF paths from side A to side B and half of the 2x1 switches in each stage of stages 332a to 332n provide RF paths from side B to side A. For example, as shown in FIG. 3, the upper half of the 2x1 switches (herein referred to as transmission switches 336t) provide an RF path to transmit an electromagnetic signal from input port A_1 from the first side A to a port on the second side B, namely one of ports B_1 to B_N. The plurality of transmission switches 336t can be grouped in a plurality of sequential transmission stages, including a first transmission stage and one or more subsequent transmission stages. As shown in FIG. 3, the first transmission stage includes one transmission switch of stage 332a and each subsequent transmission stage includes a plurality of transmission switches of stages 332b to 332n.

[0073] The lower half of the 2x1 switches (herein referred to as reception switches 336t) provide an RF path to receive an electromagnetic signal from a port on the second side B, namely one of ports B_1 to B_N, to output port A_2 on the first side A. The plurality of reception switches 336r can be grouped in a plurality of sequential reception stages, including a last reception stage and one or more preceding reception stages. As shown in FIG. 3, the last reception stage includes one reception switch of stage 332a and each preceding reception stage includes a plurality of reception switches of stages 332b to 332n.

[0074] The direction of the 2x1 switches in the last stage 332n+1 (i.e., the terminal stage switches) are inversed to allow for the selection of whether to connect a transmitting signal (e.g., port A to port B) or a reception signal (e.g., port B to port A).

[0075] Although not shown in FIG. 3, the switch matrix 330 also includes a control port couplable to an interface controller, such as interface controller 128 of system 110, for receiving at least one control signal. The control signal can control the plurality of transmission switches 336t, the plurality of reception switches 336r, and the plurality of terminal stage switches 332n+1 in a plurality of operating states of the switch matrix 330. That is, the interface controller 128 can control the operation of each of the 2x1 switches to provide an RF path across the switch matrix 330.

[0076] In each operating state of the plurality of operating states of the switch matrix 330, the plurality of transmission switches 336t are operable to provide one transmission path for an electromagnetic transmission signal from the transmission port A_1 to a transceiver port of the plurality of transceiver ports B_1 to B_N or the plurality of reception switches 336r are operable to provide one reception path for an electromagnetic reception signal from a transceiver port of the plurality of transceiver ports B_1 to B_N to the reception port A_2. As can be seen from FIG. 3, in each operating state of the plurality of operating states, each the transmission path and each reception path is unique, or distinct from each of the other transmission paths and the reception paths. That is, each operating state corresponds to a distinct transmission or reception path.

[0077] In each operating state, the switch matrix 330 can provide a transmission path and a reception path with a pre-determined minimum isolation between the transmission and reception paths. For example, in some embodiments, the pre-determined minimum isolation can be 90 dB in a pre-determined frequency range. That is, in each operating state, the transmission path has an RF isolation of at least 90 dB from the reception path in the operating frequency band of the switch matrix. In some operating states, the transmission path can have an RF isolation of more than 90 dB from the reception path.

[0078] Further, in some embodiments, the position of each switch within the switch matrix can be arranged such that the length of each reception path and each transmission path is substantially similar.

[0079] In some embodiments, the switch matrix 330 can be an integrated printed circuit board (PCB). When formed of an integrated PCB, the switch matrix 330 can have a generally planar shape. Further, the planar switch matrix 330 can have any two-dimensional shape, such as but not limited to a circle, square, rectangle, hexagon, octagon, decagon etc...

[0080] In some embodiments, the switch matrix 330 can be a plurality of distributed PCBs connected together. Distributed PCBs can be connected together with coaxial cables. When formed of distributed PCBs connected together, the switch matrix 330 can have any three- dimensional shape, such as but not limited to a dome-shape. The PCBs, whether integrated or distributed, can be standard (e.g., rigid) PCBs, flexible PCBs, or rigid-flexible PCBs, or a combination thereof.

[0081] Electromagnetic shielding can be provided around the switch matrix 330. In some embodiments, the electromagnetic shielding can be provided by multiple layers of electromagnetic shielding material around the switch matrix 330. In some embodiments, the electromagnetic shielding can be provided by positioning the switch matrix 330 between two containers. The switch matrix 330 can be sandwiched between the two containers. In some embodiments, fasteners such as but not limited to screws, can couple the switch matrix 330 and / or containers together. Each of the two containers can be formed of electromagnetic shielding material. For example, each container can be metallic containers or a non-metallic container coated with a metallic material. The metallic material can be any suitable material, including but not limited to copper, silver, or nickel. In some embodiments, the non-metallic container can be a 3D-printed container or box.

[0082] Referring now to FIG. 4, shown therein is a schematic diagram 400 illustrating a cross- sectional view of an example PCB stack implementation of an example switch matrix 430, in accordance with some embodiments. The switch matrix 430 can be switch matrix 130 of system 110.

[0083] The PCB stack 430 can include top and bottom overlays 432a and 432b (collectively referred to as overlays 432) and top and bottom solder layers 434a and 434b (collectively referred to as solder layers 434) on the inner sides of the overlays. A plurality of PCB layers 436a, 436b, 436c, 436d, 436e, 436f (collectively referred to as PCB layers 436) are sandwiched between the top and bottom solder layers. Further, each of the PCB layers 436 are separated by at least one insulation layer 438a, 438b, 438c, 438d, 438e (collectively referred to as insulation layers 438).

[0084] The example PCB stack 430 includes six PCB layers 436a, 436b, 436c, 436d, 436e, 436f (collectively referred to as layers 436). The outer PCB layers, 436a, 436f, that is the top and bottom layers or the first and sixth layers can be provided for routing RF signals. In particular, one of the outer PCB layers can be a transmission layer for routing an electromagnetic transmission signal and the other outer PCB layer can be a reception layer for routing an electromagnetic reception signal. In some embodiments, the top layer 436a can act as the reception layer while the bottom layer 436f can act as the transmission layer. In other embodiments, the top layer 436a can act as the transmission layer while the bottom layer 436f can act as the reception layer. It can be advantageous for the reception layer to be proximal to the subject to allow for better reception than otherwise with the transmission layer being proximal to the subject. For example, if the switch matrix 430 is positioned on top of a helmet structure, such as that shown in FIG. 7, the bottom layer 436f will be proximal to the subject. Accordingly, the bottom layer 436f can act as the reception layer.

[0085] Further, the transmission port A_1 can be disposed on the transmission layer and the reception port A_2 can be disposed on the reception layer. For example, when the top layer 436a is the reception layer, the reception port A_2 can be disposed on the top layer 436a and the transmission port A_1 can be disposed on the bottom layer 436f.

[0086] The example PCB stack 430 includes four intermediate PCB layers 436b, 436c, 436d, 436e between the outer PCB layers 436a, 436f. The second outermost PCB layers, 436b, 436e, that is, the second and fifth layers, can be provided for RF isolation. In particular, the second outermost PCB layers can be electrically grounded to provide RF isolation between the transmission and reception layers 436a, 436f.

[0087] The innermost PCB layers, 436c, 436d, that is, the third and fourth layers, can be provided for routing power and control signals. That is, power and control signals to control the plurality of transmission switches 336t, the plurality of reception switches 336r, and the plurality of terminal stage switches 332n+1.

[0088] Although the PCB stack 430 is shown as having six PCB layers, in other embodiments, the PCB stack 430 can have more PCB layers. With six PCB layers, the switch matrix 430 can achieve an isolation of at least 90 dB within the frequency range of the switch matrix 330 between the electromagnetic transmission signal routed through the transmission layer 436a and theelectromagnetic reception signal routed through the reception layer 436f. In particular, electromagnetic transmission signal routed through any transmission path can be isolated by at least 90 dB within about 20 MHz to about 10 GHz from the electromagnetic reception signal routed through any reception path.

[0089] The insulation layers 438a, 438b, 438d, 438e can each be formed of prepreg. At least one of the insulation layers 438 can be a non-conductive substrate layer. For example, in the PCB stack 430, insulation layer 438c can be a non-conductive substrate layer. The non-conductive substrate layer 438c can be a core, or formed of a non-conductive material, such as but not limited to FR4 (or FR-4) and / or Rogers R04003. Although the third insulation layer 438c is shown as being the non-conductive substrate layer, in other embodiments, the first insulation layer 438a, the second insulation layer 438b, the fourth insulation layer 438d, or the fifth insulation layer 438e can be the non-conductive substrate layer. Further, although only one insulation layer 438c is shown as being a non-conductive substrate layer, in other embodiments, more than one insulation layer 438 can be non-conductive. As shown, the PCB stack can include contacts 440a, 440b, 440c, and 440d for interconnecting the PCB layers. For example, one or more contacts can be for transferring the RF signal between PCB layers or for ground connections.

[0090] In some embodiments, last stages of the transmission path and the reception paths that connect switches to ports A and port B can each be located within opposite outer layers 436a, 436f to achieve high RF isolation.

[0091] Referring now to FIG. 5A, 5B, 5C, and 5D, shown therein is a top view 500, a bottom view 502, a top perspective view 504, and a side view 506 of an example switch matrix 530, in accordance with some embodiments. Switch matrix 530 can be switch matrix 130 of system 110. Example switch matrix 530 is a 2x64 implementation.

[0092] Switch matrix 530 has 64 transceiver ports 542i to 54264 (collectively referred to as transceiver ports 542) disposed along the perimeter of the switch matrix 530. As shown, switch matrix 530 has an octagonal shape (e.g., eight sides). Further, the transceiver ports 542 are equally disposed along the sides of the switch matrix 530. In particular, eight transceiver ports 542 are disposed along each of the eight edges of the octagonal switch matrix 530.

[0093] Other configurations are possible. For example, switch matrix 530 can have fewer or more transceiver ports 542. Switch matrix 530 can have 2ntransceiver ports. In some embodiments, switch matrix 530 can have 8 transceiver ports 542. In some embodiments, switch matrix 530 can have 128 transceiver ports 542. Although switch matrix 530 is shown as being octagonal, other shapes are possible, including but not limited to circles, ovals, squares, rectangles, etc.

[0094] As shown in FIG. 5A and FIG. 5B, the top layer 536a and bottom layer 536b includes a plurality of switches 544i ... 544I27 (collectively referred to as switches 544). When the top layer536a is the reception layer, the reception port 5462is disposed on the top layer 536a and the transmission port 546i is disposed on the bottom layer 536b. In some embodiments, the top layer 536a is transmission layer, the transmission port 546i is disposed on the top layer 536a and the reception port 5462is disposed on the bottom layer 536b.

[0095] As shown in FIG. 5B, the control port 548 can be disposed on the bottom layer 536b. In other embodiments, the control port 548 can be disposed on the top layer 536a.

[0096] Referring now to FIG. 6A, 6B, 6C, and 6D, shown therein is a top view 600, a bottom view 602, a top perspective view 504, and a side view 506 of an example interface controller 628, in accordance with some embodiments. Interface controller 628 can be interface controller 128 of system 110. That is, interface controller 628 can be used to control transceivers 120 and switch matrix 130, in particular, the RF routing of the switch matrix 130.

[0097] For example, interface controller 628 can be used to control switch matrix 530 of FIG. 5A, and more specifically switches 544. As shown in FIG. 6A to 6D, interface controller 628 can have a octagonal shape to match the octagonal shape of switch matrix 530 and provide a more compact form factor. Interface controller 628 can be expandable to control switch matrix of different configurations, such as a 2x128 switch matrix or a 2x64 switch matrix etc..

[0098] Interface controller 628 can be formed of multiple layers of PCB. In some embodiments, interface controller 628 can include four layers of PCB.

[0099] Referring now to FIG. 7, shown therein is a perspective view 700 of an example electromagnetic head imaging device 750, in accordance with some embodiments. A subject head can be positioned within the electromagnetic head imaging device 750.

[0100] As shown in FIG. 7, the electromagnetic head imaging device 750 can include a plurality of transceivers 720i. 7202. 7203, ... (collectively referred to as transceivers 720). Transceivers 720 can be transceivers 120 of system 110. Transceivers 720 can be integrated in the sidewalls of the helmet structure of device 750. When a subject head is positioned within the device 750, in particular, within the helmet structure, the transceivers 720 can be positioned around the subject head.

[0101] As shown in FIG. 7, the electromagnetic head imaging device 750 can include a switch matrix 730. Switch matrix 730 can be switch matrix 130 of system 110. Switch matrix 730 can be installed at the top of the device 750. Switch matrix 730 can have a generally planar, round shape.

[0102] Referring now to FIG. 8, shown therein is a perspective view 800 of another example electromagnetic head imaging device 850, in accordance with some embodiments. Similar to device 750, a subject head can be positioned within the electromagnetic head imaging device 850.

[0103] As shown in FIG. 8, the electromagnetic head imaging device 850 can include a plurality of transceivers 820i. 8202, 8203, ... (collectively referred to as transceivers 820). Transceivers 820 can be transceivers 120 of system 110. Similar to transceivers 720, transceivers 820 can be integrated in the sidewalls of the helmet structure of device 850.

[0104] Similar to device 750, the electromagnetic head imaging device 850 can include a switch matrix 830. Switch matrix 830 can be switch matrix 130 of system 110. In contrast to device 750, switch matrix 830 can be integrated in the sidewalls of the helmet structure of device 850. That is, switch matrix 830 can be distributed within the helmet structure of the device 850. Integration of the switch matrix 830 within the helmet structure allows the device to be more compact, wearable, and lighter weight.

[0105] It will be appreciated that numerous specific details are set forth in order to provide a thorough understanding of the example embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Furthermore, this description and the drawings are not to be considered as limiting the scope of the embodiments described herein in any way, but rather as merely describing the implementation of the various embodiments described herein.

[0106] It should be noted that terms of degree such as "substantially", "about" and "approximately" when used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of the modified term if this deviation would not negate the meaning of the term it modifies.

[0107] In addition, as used herein, the wording “and / or” is intended to represent an inclusive- or. That is, “X and / or Y” is intended to mean X or Y or both, for example. As a further example, “X, Y, and / or Z” is intended to mean X or Y or Z or any combination thereof.

[0108] It should be noted that the term “coupled” used herein indicates that two elements can be directly coupled to one another or coupled to one another through one or more intermediate elements.

[0109] The embodiments of the systems and methods described herein may be implemented in hardware or software, or a combination of both. These embodiments may be implemented in computer programs executing on programmable computers, each computer including at least one processor, a data storage system (including volatile memory or non-volatile memory or other data storage elements or a combination thereof), and at least one communication interface. For example and without limitation, the programmable computers (referred to below as computing devices) may be a server, network appliance, embedded device, computer expansion module, apersonal computer, laptop, personal data assistant, cellular telephone, smart-phone device, tablet computer, a wireless device or any other computing device capable of being configured to carry out the methods described herein.

[0110] In some embodiments, the communication interface may be a network communication interface. In embodiments in which elements are combined, the communication interface may be a software communication interface, such as those for inter-process communication (IPC). In still other embodiments, there may be a combination of communication interfaces implemented as hardware, software, and combination thereof.

[0111] Program code may be applied to input data to perform the functions described herein and to generate output information. The output information is applied to one or more output devices, in known fashion.

[0112] Each program may be implemented in a high-level procedural or object-oriented programming and / or scripting language, or both, to communicate with a computer system. However, the programs may be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language. Each such computer program may be stored on a storage media or a device (e.g., ROM, magnetic disk, optical disc) readable by a general or special purpose programmable computer, for configuring and operating the computer when the storage media or device is read by the computer to perform the procedures described herein. Embodiments of the system may also be considered to be implemented as a non-transitory computer-readable storage medium, configured with a computer program, where the storage medium so configured causes a computer to operate in a specific and predefined manner to perform the functions described herein.

[0113] Furthermore, the system, processes and methods of the described embodiments are capable of being distributed in a computer program product comprising a computer readable medium that bears computer usable instructions for one or more processors. The medium may be provided in various forms, including one or more diskettes, compact disks, tapes, chips, wireline transmissions, satellite transmissions, internet transmission or downloadings, magnetic and electronic storage media, digital and analog signals, and the like. The computer useable instructions may also be in various forms, including compiled and non-compiled code.

[0114] Various embodiments have been described herein by way of example only. Various modification and variations may be made to these example embodiments without departing from the spirit and scope of the invention, which is limited only by the appended claims.

Claims

CLAIMS:1 . A switch matrix for electromagnetic imaging comprising: a transmission port couplable to a radiofrequency (RF) measurement unit to receive an electromagnetic transmission signal; a reception port couplable to the RF measurement unit to transmit an electromagnetic reception signal; a plurality of transceiver ports couplable to a plurality of transceivers positioned around a subject; a plurality of printed circuit board (PCB) layers arranged in a stack, the plurality of PCB layers comprising a reception layer, a transmission layer, and at least four intermediate layers between the transmission layer and the reception layer, at least two intermediate layers of the at least four intermediate layers being electrically grounded to provide radio frequency isolation between the transmission layer and the reception layer, the transmission layer comprising a plurality of transmission switches, the reception layer comprising a plurality of reception switches; and a control port couplable to a controller for receiving at least one control signal, the at least one control signal for controlling the plurality of transmission switches and the plurality of reception switches in a plurality of operating states; wherein: in each operating state of the plurality of operating states, the plurality of transmission switches are operable to provide one transmission path for the electromagnetic transmission signal from the transmission port to a first transceiver port of the plurality of transceiver ports; and the plurality of reception switches are operable to provide one reception path for the electromagnetic reception signal from a second transceiver port of the plurality of transceiver ports to the reception port.

2. The switch matrix of claim 1 , wherein the reception layer is at a top of the stack and the transmission layer is at a bottom of the stack.

3. The switch matrix of claim 1 , wherein the transmission layer is at a top of the stack and the reception layer is at a bottom of the stack.

4. The switch matrix of any one of claims 1 or 2, wherein in each operating state of the plurality of operating states, at least one of the transmission path or the reception path is different from the transmission path and the reception path of other operating states of the plurality of operating states.

5. The switch matrix of claim 4, wherein the transmission port is disposed on the transmission layer.

6. The switch matrix of any one of claims 1 to 5, wherein the plurality of transmission switches are grouped in a plurality of sequential transmission stages, the plurality of transmission stages comprising a first transmission stage and one or more subsequent transmission stages, the first transmission stage comprising one transmission switch, each subsequent transmission stage comprising a plurality of transmission switches.

7. The switch matrix of any one of claims 1 to 6, wherein the reception port is disposed on the reception layer.

8. The switch matrix of any one of claims 1 to 7, wherein the plurality of reception switches are grouped in a plurality of sequential reception stages, the plurality of reception stages comprising a last reception stage and one or more preceding reception stages, the last reception stage comprising one reception switch, each preceding reception stage comprising a plurality of reception switches.

9. The switch matrix of any one of claims 1 to 8, wherein the plurality of transceivers comprise 2ntransceivers.

10. The switch matrix of any one of claims 1 to 9, wherein the plurality of transceivers comprise at least 8 transceivers11. The switch matrix of any one of claims 1 to 10, wherein the plurality of transceivers comprise at least 128 transceivers.

12. The switch matrix of any one of claims 1 to 11 , wherein the plurality of transceiver ports are disposed along a perimeter of the switch matrix.

13. The switch matrix of any one of claims 1 to 12, wherein the switch matrix comprises an integrated PCB.

14. The switch matrix of any one of claims 1 to 12, wherein the switch matrix comprises a plurality of distributed PCBs connected together.

15. The switch matrix of any one of claims 1 to 14, wherein the switch matrix is planar.

16. The switch matrix of any one of claims 1 to 14, wherein the switch matrix is dome-shaped.

17. The switch matrix of any one of claims 1 to 16, wherein, the switch matrix is operable in a frequency range of about 20 MHz to about 10 GHz.

18. The switch matrix of any one of claims 1 to 17, wherein in each operating state of the plurality of operating states, the reception path is isolated from the transmission path by at least 90 decibels in a frequency range of about 20 MHz to about 10 GHz.

19. The switch matrix of any one of claims 1 to 18, further comprising one or more insulation layers within the stack.

20. The switch matrix of claim 19, further comprising at least one insulation layer between each pair of PCB layers within the stack.21 . The switch matrix of any one of claims 19 or 20, wherein the insulation layers are formed of at least one of a substrate, a prepreg, a core, or a non-conductive material.

22. The switch matrix of any one of claims 1 to 21 , wherein the at least four intermediate layers comprise at least one power and control layer for transmitting power and the at least one control signal to the plurality of transmission switches and the plurality of reception switches.

23. The switch matrix of any one of claims 1 to 22, wherein each PCB comprises one or more of a standard PCB, a flexible PCB, a rigid-flexible PCB, or a combination thereof.

24. The switch matrix of any one of claims 1 to 23, wherein each switch of the plurality of transmission switches and the plurality of reception switches is a 2x1 , 4x1 , or 8x1 solid- state switch.

25. The switch matrix of any one of claims 1 to 24, further comprising electromagnetic shielding around the switch matrix.

26. The switch matrix of claim 25, wherein the electromagnetic shielding comprises at least two layers of electromagnetic shielding material.

27. The switch matrix of any one of claims 25 or 26, wherein the electromagnetic shielding comprises the switch matrix being positioned between at least two containers.

28. The switch matrix of claim 27, wherein each container comprises a metallic container or a non-metallic container coated with a metallic material.

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