WO2010067215A1

WO2010067215A1 - Reconfigurable antenna system for wireless receiver

Info

Publication number: WO2010067215A1
Application number: PCT/IB2009/054871
Authority: WO
Inventors: Ernst Bressau; Kam Choon Kwong; Pieter Lok
Original assignee: NXP BV
Current assignee: NXP BV
Priority date: 2008-12-09
Filing date: 2009-11-03
Publication date: 2010-06-17
Anticipated expiration: 2011-06-09

Abstract

An apparatus has an antenna system for receiving an electromagnetic signal, circuitry for processing the signal, and coupling means coupling the antenna system to the circuitry. The antenna system has a first antenna and a second antenna. The apparatus can be configured in a first state or a second state. In the first state, the first antenna is coupled to the circuitry and the second antenna is decoupled from the circuitry. In the second state, the first and second antennae are both coupled to the circuitry. The coupling means modifies the impedance of the antenna system under control of the first state or the second state. Owing to this intelligent coupling, the antenna configuration controllably switches between a monopole and a higher performance dipole, each using proper matching for optimal performance.

Description

RECONFIGURABLE ANTENNA SYSTEM FOR WIRELESS RECEIVER

FIELD OF THE INVENTION

The invention relates to an apparatus with an antenna system, circuitry, and coupling means between the antenna system and the circuitry for coupling the antenna system to the circuitry. The invention also relates to such coupling means.

BACKGROUND OF THE INVENTION

GB 2347560 discloses a radio apparatus with a transceiver. The apparatus comprises an internal antenna, mounted inside a housing, and an external antenna, arranged to extend away from the housing. The antennae are electrically coupled. The external antenna can be a retractable monopole antenna, e.g. a whip antenna. The internal antenna can be a rectangular element, grounded at one corner and spaced from a ground plane. When the external antenna is in its extended position, it is electrically coupled to the internal antenna, in such a way so that the two antennae form a single dipole antenna. When the external antenna is retracted, it is not coupled to the internal antenna, and only the external antenna is coupled to the feed. A coupling member is provided to electrically couple the antennae when the external antenna is in its extended position, and to electrically decouple the antennae when the external antenna is in its retracted position. By locating components of the aerial system in the housing of the phone, the aerial system becomes less susceptible to damage. By coupling the internal antenna and the external antenna, they act as a balanced antenna. That is to say, the external antenna acts as one pole of a dipole antenna and the internal antenna acts as the other pole of the dipole antenna.

GB 2347560 does not describe the coupling member other than that it can be implemented using galvanic, capacitive or inductive means for electrically coupling the antennae.

SUMMARY OF THE INVENTION

The inventors have realized that the reconfϊgurable antenna system of the known apparatus as described has a problem, in that it will lead, in operational use, to a poor impedance matching between the transceiver and the antenna system in at least the extended state of the external antenna or the retracted state of the external antenna. The transceiver itself of the known apparatus is not modified in dependence on the state of the external antenna.

The inventors therefore propose to reconfigure the electrical properties of the coupling between the antenna system and the further circuitry (e.g., receiver, transmitter or transceiver) under control of the state of the antenna system.

More specifically, the invention relates to an apparatus that comprises an antenna system for at least one of receiving or transmitting an electromagnetic signal. The apparatus also has circuitry for at least processing or generating the signal, and coupling means between the antenna system and the circuitry for coupling the antenna system to the circuitry. The antenna system has a first antenna, a second antenna. The apparatus is configurable to assume a first state or a second state. In the first state, the first antenna is electrically coupled to the circuitry and the second antenna is electrically decoupled from the circuitry, and in the second state, the first and second antennae are electrically coupled to the circuitry. The coupling means is operative to modify an impedance of the antenna system under control of the first state or the second state. Accordingly, if the antenna system is reconfigured, automatically or manually by the user of the apparatus, the coupling means automatically sees to it that the proper impedance matching is obtained. Owing to this intelligent coupling, the antenna configuration controllably switches between a monopole and a higher performance dipole, each using proper matching for optimal performance.

In an embodiment of the invention, the coupling means comprises switching means between the second antenna and the circuitry to selectively couple the second antenna to the circuitry or decouple the second antenna from the circuitry. The switching means comprises e.g., a manual switch for being manually operated, and/or an automatic switch and a sensor to control the automatic switch. The sensor is operative to detect the presence or absence of the second antenna if the latter is removable and can be mounted by the user into a jacket at the housing of the apparatus. The sensor can have any design convenient for this purpose, taking into account the function and configuration of the apparatus. For example, the sensor is operative to detect the presence or absence of the second antenna in a galvanic, electric, magnetic, optical, or mechanical manner. An optical sensor detects whether or not light emitted by, e.g., an LED, is received or not. The jacket for the second antenna is then designed in such a manner that the second antenna blocks the light when mounted to the apparatus. A magnetic sensor can detect the presence and absence of a magnetic field. The second antenna may be designed with a small permanent magnet near its mounting interface of the second antenna so that the magnet is detectable when the second antenna is mounted. A mechanical switch can be designed so as to be mechanically forced into one position by pressing the second antenna into its jacket, and to assume a second position under control of a spring if the second antenna is removed. Another sensor is designed to detect the signal current in the second antenna when mounted to the apparatus, and to thereupon control the switch, etc.

The antenna system may function as a monopole antenna in the first state, and as a dipole antenna in the second state. The first antenna may be internal to the apparatus, and the second antenna may extend outside the apparatus in operational use of the second antenna. The second antenna can be designed to be removably connected to the apparatus. The coupling means comprises, e.g., at least one of: a balun, a transformer, and an LC network.

Examples of an apparatus of the invention comprise: a mobile or portable digital TV, e.g., operating in a frequency range of 170 MHz - 860 MHZ, VHF III to UHF; a global positioning system (GPS) device such as a navigational aid, a telephone complying with Global System for Mobile communications (GSM) or with Universal Mobile Telecommunications System (UMTS).

The invention also relates to coupling means for being used in an apparatus according to the invention. For completeness, antenna tuners, also referred to as transmatch units or antenna tuning units (ATUs), are known. An ATU matches a transceiver with fixed impedance (typically 50 Ohms) to a load impedance (of the combination of feed line and antenna) that is unknown, complex or otherwise does not match. This mismatch usually arises when an antenna is being used that does not have the correct electrical length as compared to the wavelength of the signal. An ATU allows the use of a single antenna for a broad range of frequencies.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in further detail, by way of example and with reference to the accompanying drawing, wherein:

Fig. 1 is a block diagram of an apparatus in the invention; Fig. 2 is a block diagram of a first embodiment of an apparatus in the invention;

Figs. 3 and 4 are diagrams of a first embodiment of the coupling means; Fig. 5 is a block diagram of a second embodiment of an apparatus in the invention; and

Figs. 6 and 7 are diagrams of a second embodiment of the coupling means. Throughout the Figures, similar or corresponding features are indicated by same reference numerals.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 is a diagram of an apparatus 100 in the invention. Apparatus 100 comprises an antenna system 102 for at least one of receiving or transmitting an electromagnetic signal. Apparatus further has circuitry 104 for at least processing or generating the signal, and coupling means 106 between antenna system 102 and circuitry 104. Coupling means 106 serves to couple antenna system 102 to circuitry 104. Antenna system 102 has a first antenna 108, and a second antenna 110. Coupling means 106 comprises a switch 112 and a combiner 114. Switch 112 is operative to reconfigure apparatus 100 to assume a first state or a second state. In the first state, first antenna 108 is electrically coupled to circuitry 104 and second antenna 110 is electrically decoupled from circuitry 104. In the second state, first and second antennae 108 and 110 are both electrically coupled to circuitry 104. Combiner 114 is operative to modify an impedance of antenna system 102 for matching with circuitry 104 in dependence on the first state or the second state. Combination 114 combines the signals, received via antenna 108 and 110 when antenna system 102 is in the second state, as further explained below, by means of, e.g., a proper passive impedance transformation and balun conversion, or active impedance matching without a transformer and/or balun. Circuitry 104 has a low-noise amplifier (LNA) 116, known in the art, and further signal processing circuits (not shown here). Apparatus 100 comprises, e.g., a mobile telephone, or a mobile media player such as a mobile TV receiver for receipt of content information as a wireless signal from an external source, for being rendered by apparatus 100.

In the example of Fig. 1, first antenna 106 is a fixed monopole antenna and internal to apparatus 100, and antenna 108 is an external antenna that, when antenna system 102 has assumed the second state, forms a dipole antenna with internal monopole antenna 106. Also, in the example of Fig. 1, circuitry 104 comprises a receiver for processing signals received via antenna system 102.

Switch 112 is operative to electrically connect or disconnect external antenna 110 from combiner 114. Switch 112 is, e.g., a manual switch operated by the user of apparatus 100. Alternatively, switch 112 is controlled by a sensor (not shown here) that automatically detects the presence or absence of antenna 110 if the latter is removable and can be mounted by the user into a jacket (not shown) at the housing of apparatus 100. The sensor can have any design convenient for this purpose, taking into account the function and configuration of apparatus 100. For example, the sensor is operative to detect the presence or absence of antenna 110 in a galvanic, electric, magnetic, optical, or mechanical manner.

Fig. 2 is a diagram illustrating details of a first embodiment 200 of apparatus 100. In embodiment 200, low-noise amplifier 116 is a balanced LNA. As known in the art, a balanced amplifier is an electronic amplifier with a pair of identical signal paths connected in such a manner that the amplifier operates with the inputs in phase-opposition and with the output connections in phase, each balanced to signal-ground. The advantage of employing a balanced configuration is that common-mode noises and distortions can be cancelled out at the output. The result is an amplifier with lower noise and lower distortion than with amplifiers not employing a balanced configuration. The outputs of LNA 116 are coupled to a mixer 202 via a filter 204. Mixer 202 supplies the mixed signal to further receiving circuitry (not shown here). Combiner 114 comprises impedance matching means 206 that is operative to modify an impedance of antenna system 102 for matching with amplifier 116 under control of the state of switch 112. Means 206 comprises, e.g., a balun or a transformer.

Figs. 3 and 4 are diagrams 300 and 400 with more details of embodiment 200 in the second state and in the first state, respectively, of apparatus 100. In diagram 300, external antenna 110 is electrically coupled to the input of balanced LNA 116 via a transformer 206 providing a balanced antenna input signal to LNA 116. In diagram 300, antenna system 102, formed by antennae 108 and 110, has assumed a dipole configuration. In diagram 400, external antenna 110 is removed from apparatus 100 and, therefore, electrically decoupled from LNA 116. Switch 112 now connects the input connection for antenna 110 to signal-ground. The input to LNA 116 is now unbalanced. Antenna system 102 has now assumed a monopole configuration.

Fig. 5 is a diagram illustrating details of a second embodiment 500 of apparatus 100. In embodiment 500, low-noise amplifier 116 is an unbalanced LNA. Combiner 114 comprises impedance matching means 206 that is operative to modify an impedance of antenna system 102 for matching with amplifier 116 under control of the state of switch 112. Means 206 comprises, e.g., a balun or a transformer.

Figs. 6 and 7 are diagrams 600 and 700 with more details of embodiment 200 in the second state and in the first state, respectively, of apparatus 100. In diagram 600, external antenna 110 is electrically coupled to the input of unbalanced LNA 116 via a transformer 206. One coil of transformer 206 galvanically connects internal antenna 108 to the input of LNA 116, and the other coil galvanically connects external antenna 110 to signal ground. The end of the other coil, no connected to antenna 110, is connected to signal- ground. The signal in external antenna 110 is therefore inductively coupled to the input of LNA 116. In diagram 600, antenna system 102, formed by antennae 108 and 110, has assumed a dipole configuration. In diagram 700, external antenna 110 is removed from apparatus 100 and is, therefore, electrically decoupled from LNA 116. Switch 112 now connects the relevant coil, used in diagram 600 to inductively couple external antenna 110 to the input of LNA 116 to signal-ground. The input to LNA 116 is now unbalanced.

In above diagrams, switch 112 is located between external antenna 110 and combiner 114. Functionally equivalent locations for switch 112 include, e.g., between combiner 114 and LNA 116, and inside LNA 116.

Claims

CLAIMS:

1. An apparatus (100), comprising an antenna system (102) for at least one of receiving or transmitting an electromagnetic signal, circuitry (104) for at least processing or generating the signal, and coupling means (106) between the antenna system and the circuitry for coupling the antenna system to the circuitry, wherein: - the antenna system has a first antenna (106), a second antenna (108); the apparatus is configurable to assume a first state or a second state; in the first state, the first antenna is electrically coupled to the circuitry and the second antenna is electrically decoupled from the circuitry; in the second state, the first and second antennae are electrically coupled to the circuitry; and the coupling means is operative to modify an impedance of the antenna system under control of the first state or the second state.

2. The apparatus of claim 1, wherein the coupling means comprises switching means (112) between the second antenna and the circuitry to selectively couple the second antenna to the circuitry or decouple the second antenna from the circuitry.

3. The apparatus of claim 2, wherein the switching means comprises at least one of: - a manual switch for being manually operated; and an automatic switch and a sensor to control the automatic switch, the sensor being operative to detect the presence or absence of the second antenna.

4. The apparatus of claim 1, 2 or 3 wherein the antenna system functions as a monopole antenna in the first state, and as a dipole antenna in the second state.

5. The apparatus of claim 1, 2, 3 or 4, wherein the first antenna is internal to the apparatus, and wherein the second antenna extends outside the apparatus in operational use of the second antenna.

6. The apparatus of claim 1, 2, 3, 4 or 5, wherein the coupling means comprises at least one of: a balun, a transformer, and an LC network.

7. Coupling means (106) for use in an apparatus (100), the apparatus comprising an antenna system (102) for at least one of receiving or transmitting an electromagnetic signal and circuitry (104) for at least processing or generating the signal, wherein the coupling means is configured for being connected between the antenna system and the circuitry for coupling the antenna system to the circuitry; - the antenna system has a first antenna (106), a second antenna (108); the apparatus is configurable to assume a first state or a second state; in the first state, the first antenna is electrically coupled to the circuitry and the second antenna is electrically decoupled from the circuitry; in the second state, the first and second antenna are electrically coupled to the circuitry; and the coupling means is operative to modify an impedance of the antenna system under control of the first state or the second state.

8. The coupling means of claim 7, comprising switching means (112) for being connected between the second antenna and the circuitry to selectively couple the second antenna to the circuitry or decouple the second antenna from the circuitry.

9. The coupling means of claim 8, wherein the switching means comprises at least one of: - a manual switch for being manually operated; and an automatic switch and a sensor to control the automatic switch, the sensor being operative to detect the presence of absence of the second antenna.