Obviousness

Obviousness Analysis of US Patent 8,362,960 under 35 U.S.C. § 103

This analysis identifies combinations of prior art that would render the independent claims of US patent 8,362,960 obvious to a Person Having Ordinary Skill in the Art (PHOSITA) as of the patent's priority date (July 21, 2005) or filing date (December 30, 2011), considering the specific problem-solution approaches presented in the patent. The background of US8362960 explicitly states the recognized problems in the art: the difficulty of integrating a second antenna for wireless connectivity due to scarce PCB space and low isolation with the mobile communication antenna, along with the impracticality of simply separating antennas further or adding costly filter components. This clearly establishes a motivation for a PHOSITA to combine or modify existing technologies to achieve improved isolation and miniaturization in multi-antenna handheld devices.

Claim 1: Handheld Device with Slot Antenna and Parallel Orientation for Isolation

Claim 1: A handheld device comprising a first antenna arranged to operate in at least a first frequency band, and a second antenna arranged to operate in at least a second frequency band, wherein said second frequency band is different from said first frequency band, characterized in that the second antenna comprises a slot antenna comprising at least one slot in at least one conductive layer, and in that the second antenna is arranged substantially parallel to electric currents excited on at least a portion of a printed circuit board (PCB) of the handheld device by a radiating mode of said first antenna for enhancing isolation between the first antenna and the second antenna.

Combination of Prior Art: EP1867175A2 in combination with general knowledge of antenna design and electromagnetic coupling principles (as articulated in the detailed description of US8362960).

Reasoning for Obviousness:
EP1867175A2 (or its related PCT applications WO2007009804A2 and WO2007009803A2), originating from the same assignee (Fractus SA) and including common inventors, broadly discloses a handheld device with multiple antennas and methods for enhancing isolation between them. Crucially, EP1867175A2 mentions the use of a slot antenna for one of the services. The background of US8362960 itself highlights the industry trend of incorporating two separate antennas in handheld devices: a first for mobile communications and a second for wireless connectivity.

A PHOSITA, faced with the known problem of achieving good isolation between a mobile antenna and a wireless connectivity antenna in a compact handheld device (as explicitly stated in the Background of US8362960), would be motivated to consider various antenna types and their placement to optimize performance. EP1867175A2's disclosure of using a slot antenna for one of the services would lead a PHOSITA to consider implementing a slot antenna as the second antenna.

Furthermore, the detailed description of US8362960 itself explicitly teaches the underlying principle for enhancing isolation: "good isolation between antennas can be obtained by appropriately choosing the orientation on the PCB, and by selecting the antenna type (i.e., whether a given antenna substantially behaves as an electric current source, or as a magnetic current source) for each one of the antennas comprised in the handset or handheld device." It further explains that slot antennas "substantially behave as magnetic current sources" and that "good isolation...can be obtained when the electric currents excited on at least a portion of the PCB...by the radiating mode of said first antenna are substantially parallel to the equivalent magnetic currents excited on at least a portion of the extension of said second antenna."

Therefore, a PHOSITA, combining the teaching of EP1867175A2 regarding the use of a slot antenna in a multi-antenna handheld device with the well-understood electromagnetic principle that aligning electric and magnetic fields can improve isolation (which is a core teaching within US8362960 itself for why its approach works), would be motivated to orient the slot antenna (the second antenna) substantially parallel to the electric currents induced by the first antenna on the PCB. This combination is a straightforward application of known principles to solve a recognized problem in the art, namely, achieving enhanced isolation in a compact dual-antenna handheld device. The various miniaturization techniques disclosed in other Fractus patents (e.g., US2005/0275585 A1, US6975269B2, US7327318B2) would also provide a general motivation to make any antenna, including a slot antenna, as compact as possible for handheld device integration.

Claim 15: Method of Modifying First Antenna Geometry for Isolation

Claim 15: A method of enhancing the isolation between a first antenna and a second antenna in a handheld device, the method comprising the step of modifying a geometrical feature of said first antenna to make said geometrical feature electrically longer or shorter to shift an associated resonance frequency away from an operating band of said second antenna for reducing strong electromagnetic coupling between the first antenna and the second antenna.

Combination of Prior Art: EP1867175A2 in combination with general knowledge of antenna design and tuning.

Reasoning for Obviousness:
EP1867175A2 discloses a handheld device with multiple antennas and aims to enhance isolation. The problem of strong electromagnetic coupling between antennas, especially when their resonant frequencies overlap or are close, is a known challenge in RF engineering for multi-antenna systems, as acknowledged in US8362960's detailed description.

A PHOSITA designing antennas for handheld devices would possess fundamental knowledge that adjusting the physical dimensions (a "geometrical feature") of an antenna element (e.g., a radiating arm or a slot) directly impacts its electrical length and, consequently, its resonant frequency. Shortening an element typically shifts its resonance to higher frequencies, while lengthening it shifts resonance to lower frequencies. This is a basic principle taught in any antenna engineering textbook.

Given a scenario where coupling is problematic due to a resonance of the first antenna falling within the operating band of the second antenna, a PHOSITA would be motivated to apply this fundamental knowledge to shift the problematic resonance. The method described in claim 15—modifying a geometrical feature of the first antenna to make it electrically longer or shorter to shift an associated resonance frequency away from the operating band of the second antenna—is a direct application of routine antenna tuning techniques to mitigate inter-antenna coupling. The specific examples given in US8362960's FIG. 9b (shortening a conducting arm) and FIG. 9c (folding a conducting arm to shorten the effective slot length) or FIG. 11a (meander-like slot to increase electrical length) and FIG. 11b (adding a metal strip to increase electrical length) illustrate these well-known tuning mechanisms to achieve the desired frequency shift. The motivation is clear: to reduce "strong electromagnetic coupling" by moving "higher order resonant modes or spurious modes" away from the operating band of the other antenna.

Claim 20: Method of Modifying PCB Geometry for Isolation

Claim 20: A method of enhancing the isolation between a first antenna and a second antenna in a handheld device, the method comprising the step of modifying the geometry of the PCB of said handheld device to introduce on said PCB a feature able to increase the isolation between the first antenna and the second antenna in at least one frequency band.

Combination of Prior Art: EP1867175A2 in combination with general knowledge of PCB design for RF applications and EMI/EMC techniques.

Reasoning for Obviousness:
EP1867175A2 discloses multi-antenna handheld devices and aims to improve isolation. The PCB in a handheld device serves as a common ground plane for antennas, and currents flowing on this ground plane can significantly contribute to coupling between antennas, as recognized in US8362960. A PHOSITA working in RF/antenna design for compact devices would be aware of the impact of the ground plane on antenna performance and coupling.

Modifying the geometry of the PCB, particularly the ground plane, to control current paths and reduce electromagnetic coupling is a standard technique in RF and electromagnetic compatibility (EMC) design. Introducing slots in a ground plane is known to alter current distributions and can be used to create high impedance paths or redirect currents, thus affecting coupling. This is evident from the classification H01Q13/10 (Resonant slot antennas) and H01Q13/106 (Microstrip slot antennas), demonstrating the prevalence of slots in conductive layers. Similarly, shorted conductive strips (often functioning as quarter-wave stubs) are routinely employed in RF circuits to present high impedance at specific frequencies.

US8362960 itself provides specific examples of such PCB modifications in its detailed description: FIG. 13a shows "introducing a slot on the PCB", and FIG. 13b shows "placing a conductive stripe above the PCB that is shorted on one end to the PCB". The patent clearly states the purpose: to "present a high impedance path to the currents flowing on the perimeter of the ground plane" or to "alter the phase and amplitude of the coupling and to generate multiple signal coupling paths such that those multiple signals cancel or partially cancel each other."

Therefore, a PHOSITA, recognizing the problem of inter-antenna coupling in a handheld device (EP1867175A2) and understanding that PCB ground plane currents contribute to this coupling, would be motivated to modify the PCB geometry using known RF techniques like introducing slots or shorted conductive strips. This is a routine engineering choice to achieve the desired goal of increased isolation at specific frequencies, directly addressing the stated problem of low isolation.

Claim 23: Handheld Device with Parasitic Element for Isolation

Claim 23: A handheld device comprising a first antenna for at least one mobile communication service, a second antenna being a slot antenna for at least one wireless connectivity service, and a conducting strip placed in the vicinity of the first antenna and the second antenna, wherein said conducting strip is not connected to the ground plane of the PCB of the handheld device, and wherein an unfolded length of the conducting strip is approximately half of an operating wavelength at a frequency for which the isolation between the first antenna and the second antenna is to be enhanced, and wherein said conducting strip functions as a shield for electromagnetic radiation between the first antenna and the second antenna.

Combination of Prior Art: EP1867175A2 in combination with general knowledge of parasitic elements, resonant structures, and electromagnetic shielding in antenna design.

Reasoning for Obviousness:
EP1867175A2 discloses a handheld device with multiple antennas (e.g., mobile and wireless connectivity) and focuses on enhancing isolation. A PHOSITA attempting to improve isolation between antennas in a compact space would consider passive elements that interact electromagnetically without direct connection. The use of parasitic elements is a well-established practice in antenna engineering to influence radiation patterns, impedance matching, or to enhance isolation.

Furthermore, the concept of a half-wavelength resonant structure is fundamental in antenna theory. A conductive strip with an unfolded length approximately half of an operating wavelength will resonate at that frequency and can effectively absorb and reradiate, or reflect, electromagnetic energy, thus acting as a shield or a filter. The detailed description of US8362960 explicitly states that the conductive strip (parasitic element) "functions as a shield for the electromagnetic radiation between the two antennas" and that its "unfolded length... has been selected to be approximately half of the wavelength at the frequency for which the isolation between antennas needs to be enhanced."

Therefore, a PHOSITA encountering isolation issues in a dual-antenna handheld device (EP1867175A2) would be motivated to introduce a parasitic element to act as a shield. Knowing the resonant properties of half-wavelength conductors, it would be obvious to design such a parasitic strip to be approximately half of an operating wavelength at the frequency where isolation needs improvement, thereby leveraging its resonant characteristics for effective shielding. This is a direct application of known electromagnetic principles and antenna design techniques to solve the recognized problem of inter-antenna coupling in handheld devices.