Active elimination of radio frequency interference for improved signal-to-noise ratio for in-situ NMR / NQR applications

核磁共振（NMR --用于医学扫描的磁共振成像或MRI背后的技术）为“真实世界”中的材料检测和表征提供了巨大的机会：即实验室之外的开放访问、电磁非屏蔽应用，需要评估材料的质量、状态或存在。这些应用包括：最大限度地减少延误，以便在施工期间固化混凝土或评估建筑环境中的建筑物退化;管理林业，以决定砍伐哪些树木或最大限度地减少加工过程中木材干燥的能源消耗;或在机场等安全地点检测非法材料;以及用于石油和天然气勘探的井下测井。然而，除了石油和天然气勘探，其中地壳提供了天然的电磁屏蔽，外部射频干扰（RFI）拾取限制了使用负担得起的和实用的轻质、低场强磁体的材料检测极限，并因此抑制了该技术被工业广泛采用。问题是无线电信号的不必要拾取，如航空通信和业余无线电。在开放式探测器中，拾取占主导地位，并掩盖了来自待检测材料的微弱NMR信号。本提案的目的是解决RFI拾取问题。我们提出了一种新的方法来消除拾取，称为主动RFI抑制。我们将在开放式NMR系统中建立一个主动RFI抑制技术演示器。我们的目标是将信噪比提高10倍以上，足以满足建筑、林业和国土安全的需求。该项目利用了移动的通信行业最近在真实的时间信号处理和射频工程方面的快速发展，这些技术使现代设备能够以载波频率在真实的时间内处理无线电信号。有了这些进步，我们能够独立于NMR信号测量RFI拾取。因此，我们可以从NMR信号中消除拾取。该项目的团队由NMR技术和应用以及应用射频电子工程方面的专家组成。该项目建立在2014年与Dstl联合进行的RFI表征和软件可行性研究以及我们在实验室和建筑工地和森林中的“现实世界”中在建筑和林业中使用NMR的经验基础上。Dstl仍然参与其中，并通过支持工程博士研究生，提供技术硬件来构建演示器和详细的安全应用知识。

Nuclear magnetic resonance (NMR - the technology behind magnetic resonance imaging or MRI as used in medical scanning) offers enormous opportunity for materials detection and characterisation in the "real-world": that is open-access, electromagnetically unshielded applications outside of the laboratory where it is necessary to assess the quality, state or presence of materials. These applications include: the minimisation of delays to allow concrete to cure during construction or the assessment of building degradation in the built environment; managed forestry in order to decide which trees to fell or to minimise energy consumption from timber drying during processing; or illicit material detection at secure locations such as airports; and down bore-hole logging for oil and gas well exploration. However, save oil and gas exploration, where the earth's crust provides a natural electromagnetic shield, external radio frequency interference (RFI) pick-up restricts materials detection limits using affordable and practical light-weight, low-field strength magnets and hence inhibits the technology being taken up widely by industry. The problem is unwanted pick-up of radio signals such as aeronautical communications and amateur radio. The pick-up dominates and masks the weak NMR signals coming from materials to be inspected in open-access detectors.It is the purpose of this proposal to address RFI pick-up head on. We propose a new method to eliminate pick-up called active RFI suppression. We will build a technology demonstrator for active RFI suppression in an open-access NMR system. Our target is a greater than 10 times improvement in the signal-to-noise ratio, sufficient to enable take-up in construction, forestry and homeland security. The project takes advantage of recent rapid developments in real time signal processing and radio frequency engineering emanating from the mobile communications industry that enable modern devices to process radio signals in real time at the carrier frequency. With these advances we are able to measure the RFI pick-up independently of the NMR signal. Hence we can eliminate the pick up from the NMR signal. The team assembled for the project uniquely comprise experts in NMR techniques and applications and applied radio frequency electronic engineering. The project builds on an RFI characterisation and software feasibility study carried out jointly with Dstl during 2014 and our own experience of using NMR in construction and forestry both in the laboratory and outside in the "real-world" on construction sites and in forests. Dstl remain involved and contribute through support for an engineering doctorate research student, the provision of technical hardware on which to build the demonstrator and detailed knowledge of security applications.