Patent Description:
eLoran is a low-frequency radio navigation system that operates in the frequency band of <NUM> to <NUM>. eLoran is built on internationally standardized Loran-C, and provides a high-power PNT service for use by all modes of transport and in other applications. eLoran is an independent dissimilar complement to GNSS. It allows GNSS users to retain the safety, security and economic benefits of GNSS even when their satellite services are disrupted. eLoran meets a set of worldwide standards and operates wholly independently of GPS, GLONASS, Galileo, or any future GNSS. Each eLoran receiver is operable in all regions where an eLoran service is provided. eLoran receivers work automatically, with minimal user input. The core eLoran system comprises modernized control centers, transmitting stations and monitoring sites. eLoran transmissions are synchronized to an identifiable, publicly-certified, source of Coordinated Universal Time (UTC) by a method wholly independent of GNSS. This allows the eLoran Service Provider to operate on a time scale that is synchronized with but operates independently of GNSS time scales. Synchronizing to a common time source also allows receivers to employ a mixture of eLoran and satellite signals. The principal difference between eLoran and traditional Loran-C is the addition of a data channel on the transmitted signal. This conveys application-specific corrections, warnings, and signal integrity information to the user's receiver. It is this data channel that allows eLoran to meet the very demanding requirements of landing aircraft using non-precision instrument approaches and bringing ships safely into harbor in low-visibility conditions. eLoran is also capable of providing the exceedingly precise time and frequency references needed by the telecommunications systems that carry voice and internet communications.

eLoran has many uses. Typically, an antenna for an eLoran system is rather bulky. However, a ship, airplane or other vehicle can incorporate such a device. A desirable application of the eLoran technology is in smaller devices. For example hand held devices or portable phones could benefit from the technology. However, the size of the antennas currently known make such implementation unmanageable or impossible.

<CIT> provides wired earphones in which the earphone cable functions as an antenna wire. <CIT> provides a compact smart antenna for a communications device, such as a cell phone. <CIT> provides a miniaturised planar antenna for a digital television.

In one aspect of the invention, there is provided an antenna as defined in claim <NUM>. The antenna includes a dielectric substrate having a planar shape. The dielectric substrate has a first side and a second side. An elongated feed is disposed on the first side of the substrate. A ground plane is disposed adjacent to and spaced apart from the feed on the first side of the substrate. A meander has a first end coupled to the elongated feed. The meander comprises a second end disposed opposite the first end. A first extension extends from the second end adjacent to the meander. A second extension extends from the second end adjacent to the meander.

In an aspect of the invention, there is provided a system as defined in claim <NUM>.

The antenna may have various size features for the individual parts of the antenna. The antenna is used to receive eLoran signals, although other uses are not precluded.

Referring now to <FIG>, a high level diagrammatic view of an eLoran communication system <NUM> is set forth. In general, eLoran signals travel over the surface of the earth and are subject to small propagation delays that depend on the electrical conductivity of the ground. A high level of accuracy is achieved by correcting for propagation delays.

The system includes a control center <NUM> that is in communication with a plurality of transmitting stations <NUM>. The transmitting stations <NUM> transmit signals to the user devices <NUM>. The control center <NUM> typically runs unattended with service personnel on call. Monitoring sites <NUM> act as receivers and provide real-time information to the control center <NUM> for detecting abnormalities. Feedback from the monitoring sites <NUM> may be used for providing differential corrections.

The transmitting stations transmit signals to different types of users. In this example, a user device <NUM> may be disposed in various vehicles or may be hand held type devices. As illustrated, an airplane 16A, a ship 16B, an automotive vehicle 16C and a portal device 16D may incorporate a receiving system. In this example, the portal device 16D is a cellular phone. An antenna <NUM> is used for receiving signals at the various devices. The signals received may be time signals and location signal. As well, a data channel is also established within the eLoran system. The data channel conveys corrections, warnings and signal integrity information to the receivers associated with the user devices <NUM>.

Referring now to <FIG>, the antenna <NUM> may be associated with a band pass filter <NUM> and an amplifier <NUM>. The antenna <NUM>, the band pass filter <NUM> and the amplifier <NUM> may be disposed on a substrate <NUM>. The substrate <NUM> may be a dielectric substrate. However, the band pass filter <NUM> and the amplifier <NUM> may be disposed as separate components coupled between the antenna <NUM> and a receiver <NUM>. Details of the antenna <NUM> are described in more detail below. The band pass filter <NUM> is used for filtering higher frequencies and lower frequencies than the band provided. In one example, a Chebyshev band pass filter is used. In an eLoran system, the center frequency is <NUM> and the desirable frequencies are between <NUM> and <NUM> to provide a total bandwidth of <NUM>. Of course, for other systems, the band pass filter <NUM> may be tuned differently.

The amplifier <NUM> is used for amplifying the signal communicated from the band pass filter <NUM>. In one example, a two stage amplifier using an LT6235 from Analog Devices Corp. The LT6235 is a low noise, low power instrumentation amplifier. A second amplifier in series with the first amplifier was used. The LT1206 amplifier is a current feedback amplifier with high output current drive capability. However, various types of signal and multi-stage amplifiers may be used depending upon the signal received and the desired output characteristics. The receiver <NUM> receives the amplified signal from the amplifier <NUM>. The receiver <NUM> processes the amplified signal to determine location, timing and other data therefrom.

An isolation transformer <NUM> may be coupled to the substrate <NUM> or to the receiver <NUM> or both. The isolation transformer filters additional noise from the received signal. It was found that the isolation transformer <NUM> allows lower level signals to be discerned from the received signal.

Referring now to <FIG> and <FIG>, the antenna <NUM> is illustrated on a substrate <NUM>. In this example, the substrate <NUM> contains only the antenna <NUM> and the circuitry such as the band pass filter <NUM>, the amplifier <NUM> and the isolation transformer <NUM>. In this example, the antenna <NUM> is formed from a planar outer conductive layer of a circuit board. A connector <NUM> is coupled to the circuit board. The connector <NUM> illustrated as a subminiature version A (SMA) connector. The SMA connector <NUM> is a semi-precision coaxial RF connector. The connector <NUM> has an outer portion <NUM> and an inner portion <NUM>. The outer portion <NUM> is coupled to a ground plane <NUM> that has two ground plane portions 46A, 46B. The ground plane 46A, 46B are electrically in communication through the outer portions <NUM>. The ground planes 46A, 46B are disposed laterally relative to an elongated feed <NUM>. The feed <NUM> has two elongated sides <NUM> adjacent to and spaced apart from the first ground plane 46A and the second ground plane 46B by gaps 50A and 50B in the electrically conductive layer of the substrate <NUM>. Gaps 50A, 50B are used to separate the ground plane 46A from the feed <NUM> while gap 50B is used to space the ground plane 46B from the feed <NUM>. In this example, the feed <NUM> comprises a first feed portion 48A and a second feed portion 48B that are spaced apart by a gap <NUM> in the conductive layer of the substrate <NUM>.

Coupling components <NUM> may be disposed over the gaps 50A, 50B and <NUM>. That is, the coupling components <NUM> may be a combination of one or more electrical components. For example, a capacitor, a very high resistance resistor, such as a one megohm and diodes may be used as the coupling components. The coupling components may be also be an inductor. The size of the components, for example, the capacitance, the resistance, the inductance or the type of diode varies depending upon the characteristics of the received signal.

The antenna <NUM> has a longitudinal axis LA that extends through the connector and through the feed portions 48A, 48B. The longitudinal sides <NUM> of the feeds 48A, 48B including the gaps 50A, 50B are parallel to the longitudinal axis LA. In this example, the first end <NUM> of the feed <NUM> is triangular or angled and is coupled to the inner portion <NUM> of the connector <NUM>. A second end <NUM> of the feed <NUM> is coupled to a meander <NUM>. The meander <NUM> has a first end <NUM> coupled to the second end <NUM> of the feed <NUM>. The meander <NUM> has a second end <NUM> that may be referred to as a common node as will be described in further detail below. The meander <NUM> has a longitudinal length between the first end <NUM> and the second end <NUM>, which, in this example, is less than the longitudinal length of the feed. The meander <NUM> has a plurality of turns <NUM> that are formed from a plurality of lateral portions <NUM> and a plurality of longitudinal portions <NUM> that space out the lateral portions <NUM> in the longitudinal direction. The lateral portions <NUM> and the longitudinal portions <NUM> form right angles. The longitudinal portions <NUM>, except the first and last longitudinal portions, extend symmetrically on each side of the longitudinal axis LA and have a length longer than the combination of the feed <NUM> and the gaps 50A, 50B. The number of turns <NUM> formed by the lateral portions <NUM> and the longitudinal portions <NUM> increase the efficiency. In this example, the number of turns <NUM> is twelve. However, at least <NUM> turns may be used. The resonant frequency of the meander <NUM> decreases as the length of the longitudinal portions <NUM> increase. Thus, the size of the meander <NUM> varies depending upon the characteristics of the signal to be received. The meander <NUM> is elongated and the total length of the lateral portions <NUM> is longer than the longitudinal portions <NUM>.

The second end <NUM> is coupled to a first extension 80A and a second extension 80B. In this example, the first extension 80A comprises a first lateral portion 82A and the second extension 80B comprises a second lateral portion 82B. The lateral portions 82A, 82B extend laterally wider than the longitudinal portions of the turns <NUM> of the meander <NUM>. The first extension 80A also has a longitudinal portion 84A extending longitudinally from the lateral portion 80A. The second extension 80B has a longitudinal portion 84B extending longitudinally from the lateral portion 82B. The longitudinal portion 84A, 84B are parallel to the longitudinal axis, in this example. The lateral portion 82A forms a right angle with the longitudinal portion 84A. The lateral portion 82B forms a right angle with the longitudinal portion 84B. Longitudinal portion 84A extends toward the ground plane 46A. The longitudinal portion 84B extends toward the ground plane 46B.

Referring now also to <FIG>, the substrate <NUM> has a first side 26A and a second side 26B. The first side 26A has the components <NUM> illustrated in <FIG>, namely the ground plane 46A, 46B, the components of the meander <NUM> and the extensions 80A, 80B and its components making them coplanar. The ground plane <NUM> does not extend opposite the meander <NUM> of the substrate <NUM>. The first side components <NUM> generally refer to the components described above on the first side 26A of the substrate <NUM>. To improve the reception, a second ground plane <NUM> may be disposed on the second side 26B of the substrate <NUM>. The ground plane <NUM> may extend under the ground plane <NUM> and under the meander <NUM> and the first extension and the second extension 80A, 80B. However, the ground plane <NUM> is optional. It should be noted that the components <NUM> may be etched from the circuit board. That is, the substrate <NUM> may include a first metal side and a second metal side separate by a dielectric. The dielectric may be exposed in areas by cutting or chemically etching so that the components forming the meander are formed. The components forming the meander <NUM> may be referred to as a circuit trace. Likewise, the gaps 50A, 50B and <NUM> may be formed in a similar manner by etching or chemical removal. Another process for forming the antenna <NUM> is three dimensional printing.

Referring now to <FIG>, the ground plane <NUM>' is separated from the second side of the substrate 26B. That is, the ground plane <NUM>' may not be formed as part of the substrate <NUM> but rather a separate component or a component of the vehicle or device that is it mounted. For example, the ground plane <NUM>' may be the outer skin of a ship, airplane or car.

In the present example, a center frequency of <NUM> is used with a <NUM> bandwidth. The size of the various components used in one constructed embodiment are as follows: the length A of the lateral portions <NUM> was <NUM>. The length B of the lateral spacing between the longitudinal portions 84A, 84B was <NUM>. The length C corresponding to the lateral extent of the ground plane <NUM> was <NUM> in. The length D corresponding to the distance between the end of the longitudinal portions 84A, 84B of the first extension 80A and the second extension 80B was <NUM>. The length E corresponding to the distance between the ground plane and the lateral portions 82A, 82B was <NUM>. The length F between the furthest extent of the lateral portions 82A, 82B to the ground plane <NUM> is <NUM> in. The length G corresponds to the thickness of the meanders is <NUM>. The length H corresponding to the distance between two adjacent lateral portions of the meander is <NUM>. The length I corresponds to the longitudinal distance of the feed <NUM> and the length longitudinally of the ground plane <NUM>. The length J corresponding to the distance from the angle to the connector <NUM> is <NUM>. The length K corresponding to the distance from the end of the terminals <NUM> to the connector <NUM> is <NUM>. The length L corresponding to the width of the feed <NUM> is <NUM>. The gap between the feed and each ground plane 46A, 46B is <NUM> in. The width end corresponding to the width of the end of the feed is <NUM>. The length O of the gap between the first end <NUM> of the feed <NUM> and the ground planes 46A and 46B is <NUM>.

Example embodiments are provided so that this disclosure will be thorough and will fully convey the scope to those who are skilled in the art.

Claim 1:
An antenna (<NUM>) comprising:
a dielectric substrate (<NUM>) having a planar shape, said dielectric substrate comprising a first side (26A) and a second side (26B);
an elongated feed (<NUM>) disposed on the first side of the substrate, said elongated feed comprising a first longitudinally extending side (<NUM>) and a second longitudinally extending side (<NUM>), said elongated feed comprising a first portion (48A) spaced apart from a second portion (48B) by a coupling element (<NUM>);
a ground plane (<NUM>) disposed adjacent to and spaced apart from the feed on the first side of the substrate, wherein the ground plane comprises a first ground plane portion (46A) adjacent to and spaced apart from the first longitudinally extending side and a second ground plane portion (46B) adjacent to and spaced apart from the second longitudinally extending side;
a meander (<NUM>) having a first end (<NUM>) coupled to the elongated feed, said meander comprising a second end (<NUM>) disposed opposite the first end, wherein the elongated feed and the meander are coaxial about a longitudinal axis (LA), wherein the second end extends longitudinally, is coaxial with the longitudinal axis and forms a common node;
a first extension (80A) extending from the second end adjacent to the meander at the common node, said first extension comprising a first lateral portion (82A) extending from the second end and a first longitudinal portion (84A) extending from the first lateral portion and disposed adjacent to the meander; and
a second extension (80B) extending from the second end adjacent to the meander at the common node, said second extension comprising a second lateral portion (82B) extending from the second end and a second longitudinal portion (84B) extending from the second lateral portion and disposed adjacent to the meander on an opposite side of the meander from the first longitudinal portion.