# US 9,872,379 B2 · Flexible printed circuit with radio frequency choke > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,872,379 B2 - Document ID: US9872379B2 - Status: Granted - Kind: B2 - Application number: 15/071,481 - Filed: 2016-03-16 - Published: 2017-09-21 - Granted: 2018-01-16 - Earliest claimed: 2016-03-16 - Assignees: Microsoft Technology Licensing, LLC - Applicants: Microsoft Technology Licensing LLC - Inventors: Patrick Codd; Agustya Mehta - Web page: https://patentgrep.com/patent/US9872379B2 ## CPC - H05K 1/0233: {Filters, inductors or a magnetic substance} - G02B 27/017: {Head mounted} - H04N 23/54: Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils - H04N 23/57: Mechanical or electrical details of cameras or camera modules specially adapted for being embedded in other devices - H04N 25/617: for reducing electromagnetic interference, e.g. clocking noise - H05K 1/028: {Bending or folding regions of flexible printed circuits (H05K1/0283 takes precedence)} - H05K 1/189: characterised by the use of flexible or folded printed circuits - H01F 27/065: {Mounting on printed circuit boards} - H05K 3/4691: {Rigid-flexible multilayer circuits comprising rigid and flexible layers, e.g. having in the bending regions only flexible layers} - H05K 2201/1003: Non-printed inductor - H05K 2201/10151: Sensor - H05K 2201/10189: Non-printed connector - H05K 2201/2009: Reinforced areas, e.g. for a specific part of a flexible printed circuit - H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES ## Abstract In an electronic device that employs high-speed differential signaling on one or more pairs of conductors in a flexible printed circuit, RF chokes are placed in the differential signal path and mounted directly on the flexible printed circuit which is used to interconnect a peripheral device, such as an image sensor, through a connector to another device component such as a main printed circuit board. The RF chokes are configured to suppress common-mode noise propagating in the differential pairs of conductors. In one illustrative embodiment, the RF chokes are located on the flexible printed circuit adjacent to the peripheral device to suppress common-mode noise near its source. In another illustrative embodiment, the RF chokes are mounted adjacent to the connector to suppress the common-mode noise before it has an opportunity to escape the flexible printed circuit at the major discontinuity presented by the connector. ## Claims ### Claim 1 A flexible printed circuit assembly for use in an electronic device, comprising: a flexible printed circuit comprising conductors disposed on a flexible substrate and including at least one planar portion; a set of conductors configured to route a signal as a differential pair from a peripheral device utilized in the electronic device as an input to the flexible printed circuit; a connector coupled to the set of conductors configured to route the signal as an output from the flexible printed circuit; a first radio frequency common-mode choke connected in series with the differential pair of clock signal conductors; and a second radio frequency common-mode choke connected in series with the differential pair of data signal conductors, wherein the first and second radio frequency common-mode chokes are mounted on the planar portion of the flexible printed circuit proximate to the connector. ### Claim 2 (depends on 1) The flexible printed circuit assembly of claim 1 in which the connector is configured for connection to an electronic component that supports an application processor. ### Claim 3 (depends on 1) The flexible printed circuit assembly of claim 1 in which the signal comprises a high-speed differential signal. ### Claim 4 (depends on 1) The flexible printed circuit assembly of claim 1 in which at least one of the chokes is a common-mode choke comprising first and second windings around a common core. ### Claim 5 (depends on 1) The flexible printed circuit assembly of claim 1 in which at least one of the chokes is a common-mode choke implemented in silicon. ### Claim 6 (depends on 1) The flexible printed circuit assembly of claim 1 in which the flexible printed circuit includes a stiffener configured to stiffen the planar portion of the flexible printed circuit and at least one of the chokes is mounted on the stiffened planar portion. ### Claim 7 (depends on 1) The flexible printed circuit assembly of claim 1 in which the connector comprises one of a tab, finger, or tail portion of the flexible printed circuit that is configured for mateable insertion with a corresponding connector disposed on a component of the electronic device. ### Claim 8 (depends on 7) The flexible printed circuit assembly of claim 7 in which the component includes one of a rigid printed circuit board or a second flexible printed circuit. ### Claim 9 An electronic device, comprising: at least one processor; a main circuit board on which the at least one processor is mounted; a flexible printed circuit comprising conductors disposed on a flexible substrate and including at least one planar portion; an image sensor coupled to the flexible printed circuit and configured to generate a differential signal that is transmitted over a pair of conductors in the flexible printed circuit; a connector configured to electrically interconnect the flexible printed circuit with the main circuit board so that the image sensor is operatively coupled to the at least one processor; a first radio frequency common-mode choke connected in series with the differential pair of clock signal conductors; and a second radio frequency common-mode choke connected in series with the differential pair of data signal conductors, wherein the first and second radio frequency common-mode chokes are mounted on the planar portion of the flexible printed circuit proximate to the connector. ### Claim 10 (depends on 9) The electronic device of claim 9 in which at least one of the common-mode chokes is mounted adjacent to the connector so as to reduce electro-magnetic interference from escaping the flexible printed circuit at a discontinuity presented by the connector. ### Claim 11 (depends on 9) The electronic device of claim 9 in which at least one of the common-mode chokes is mounted adjacent to the image sensor so as to attenuate common-mode noise near an active noise source. ### Claim 12 (depends on 9) The electronic device of claim 9 in which the image sensor is configured to generate multiple differential signals each of the differential signals being transmitted over different respective pairs of conductors in the flexible printed circuit. ### Claim 13 (depends on 12) The electronic device of claim 12 in which a first differential signal is a clock signal and a second differential signal is a data signal. ### Claim 14 (depends on 9) The electronic device of claim 9 as embodied in a head mounted display device. ### Claim 15 An image sensor assembly, comprising: a flexible printed circuit including etched conductors disposed on one or more flexible substrate layers and including at least one planar portion; an image sensor mounted on the flexible printed circuit that is configured to generate differential clock and data signals that are transmitted on different respective pairs of conductors; a connector portion of the flexible printed circuit that is configured to enable the pairs of conductors to be connected to an external system; a first radio frequency common-mode choke connected in series with the differential pair of clock signal conductors; and a second radio frequency common-mode choke connected in series with the differential pair of data signal conductors, wherein the first and second radio frequency common-mode chokes are mounted on the planar portion of the flexible printed circuit proximate to the connector portion. ### Claim 16 (depends on 15) The image sensor assembly of claim 15 in which the planar portion is rigidized using one of stiffener or hybrid rigid-flex printed circuit. ### Claim 17 (depends on 15) The image sensor assembly of claim 15 in which the first and second radio frequency common-mode chokes are configured to attenuate common-mode noise in the respective clock and data signals. ### Claim 18 (depends on 15) The image sensor assembly of claim 15 in which the image sensor and external system communicate according to the MIPI (Mobile Industry Processor Interface) specification. ### Claim 19 (depends on 15) The image sensor assembly of claim 15 in which the image sensor assembly is utilized as an inward sensor or an outward sensor in a head mounted display device or wearable computing device.