GB2465404A

GB2465404A - Plural antenna elements with a switching arrangement and method

Info

Publication number: GB2465404A
Application number: GB0821132A
Authority: GB
Inventors: Duncan Bremner
Original assignee: ITI Scotland Ltd
Current assignee: ITI Scotland Ltd
Priority date: 2008-11-18
Filing date: 2008-11-18
Publication date: 2010-05-19
Also published as: GB0821132D0

Abstract

An antenna arrangement comprises two or more antenna elements 3, a transmitter 9 and a receiver 7. A first switch S1t— S6tis connected between each respective antenna element 3 and the transmitter 9 and a second switch S1r—S6ris connected between each respective antenna element 3 and the receiver 7. An integrated circuit comprising a transmitter 9, a receiver 7 and first and second switches S associated with each of two or more antenna elements 3 may be provided. The first switch may connect the antenna element 3 to the transmitter 9 and the second switch may connect the antenna element 3 to the receiver 7. Alternatively, an integrated circuit merely comprising first and second switches S may be used in such an antenna arrangement. Further, an integrated circuit comprising a plurality of transceivers 9 and a plurality of respective switches S or comprising a switch S and a transmitter 9 or a receiver 7 may be employed. Also disclosed is a method of operating an antenna arrangement which involves providing a first switch between an antenna element 3 and a transmitter 9 and a second switch between the antenna element 3 and a receiver 7 and where the first and second switches are in a parallel arrangement.

Description

I

ANTENNA ARRANGEMENT AND METHOD

Technical Field

The present invention relates to an antenna arrangement and method, and in particular to an antenna arrangement and method having an integrated radio frequency circuit and antenna front end, for use in ultra-wideband applications.

Background

Ultra-wideband is a radio technology that transmits digital data across a very wide frequency range, 3.1 to 10.6 GHz. It makes use of ultra low transmission power, typically less than -41 dBm/MHz, so that the technology can literally hide under other transmission frequencies such as existing Wi-Fi, GSM and Bluetooth. This means that ultra-wideband can co-exist with other radio frequency technologies. However, this has the limitation of limiting communication to distances of typically 5 to 20 metres.

There are two approaches to UWB: the time-domain approach, which constructs a signal from pulse waveforms with UWB properties, and a frequency-domain modulation approach using conventional FFT-based Orthogonal Frequency Division Multiplexing (OFDM) over Multiple (frequency) Bands, giving MB-OFDM. Both UWB approaches give rise to spectral components covering a very wide bandwidth in the frequency spectrum, hence the term ultra-wideband, whereby the bandwidth occupies more than per cent of the centre frequency, typically at least 500 MHz.

These properties of ultra-wideband, coupled with the very wide bandwidth, mean that UWB is an ideal technology for providing high-speed wireless communication in the home or office environment, whereby the communicating devices are within a range of m of one another.

Figure 1 shows the arrangement of frequency bands in a multi-band orthogonal frequency division multiplexing (MB-OFDM) system for ultra-wideband communication.

The MB-OFDM system comprises fourteen sub-bands of 528 MHz each, and uses frequency hopping every 312 ns between sub-bands as an access method. Within each sub-band OFDM and QPSK or DCM coding is employed to transmit data. It is noted that the sub-band around 5 GHz, currently 5.1-5.8 GHz, is left blank to avoid interference with existing narrowband systems, for example 802.1 la WLAN systems, security agency communication systems, or the aviation industry.

The fourteen sub-bands are organized into five band groups: four having three 528 MHz sub-bands, and one having two 528 MHz sub-bands. As shown in Figure 1, the first band group comprises sub-band 1, sub-band 2 and sub-band 3. An example UWB system will employ frequency hopping between sub-bands of a band group, such that a first data symbol is transmitted in a first 312.5 ns duration time interval in a first frequency sub-band of a band group, a second data symbol is transmitted in a second 312.5 ns duration time interval in a second frequency sub-band of a band group, and a third data symbol is transmitted in a third 312.5 ns duration time interval in a third frequency sub-band of the band group. Therefore, during each time interval a data symbol is transmitted in a respective sub-band having a bandwidth of 528 MHz, for example sub-band 2 having a 528 MHz baseband signal centred at 3960 MHz.

The basic timing structure of a UWB system is a superframe. A superirame consists of 256 medium access slots (MAS), where each MAS has a defined duration, for example 256 ts. Each superframe starts with a Beacon Period, which lasts one or more contiguous MASs. The start of the first MAS in the beacon period is known as the "beacon period start".

The technical properties of ultra-wideband mean that it is being deployed for applications in the field of data communications, For example, a wide variety of applications exist that focus on cable replacement in the following environments: -communication between PCs and peripherals, i.e. external devices such as hard disc drives, CD writers, printers, scanner, etc. -home entertainment, such as televisions and devices that connect by wireless means, wireless speakers, etc. -communication between handheld devices and PCs, for example mobile phones and PDAs, digital cameras and MP3 players, etc. Current UWB designs utilize omni-directional or smart antennas, whereby switches are used to select different antenna sectors within the smart antenna module.

Figure 2 is an example of a typical antenna arrangement comprising a smart antenna 1 having a plurality of antenna elements 3 to 36. The antenna elements 3 to 36 are connected to an RF front end circuit 6 comprising an RF receiver 7. The RF front end circuit 6 is separate from the antenna 1. A switching unit 5 comprising a plurality of switches S1 to S6 is connected between the plurality of antenna elements 3 to 36 and the RE front end circuit 6. The plurality of switches 3 to 36 enable the RF receiver 7 of the RE front end circuit 6 to selectively receive an incoming signal from each of the sectors served by the respective antenna elements 3 to 36. It is noted that the switching unit 5 can form a separate unit interposed between the antenna 1 and the RE front end circuit.

Figure 3 shows an example of an antenna arrangement similar to that of Figure 2, but where the smart antenna 1 is connected to an RE transmitter 9 in the RE front end circuit 6. In such an arrangement the plurality of switches S1 to S6 of the switching unit are connected between the respective plurality of antenna elements 3 to 36 and the RF transmitter 9 of the RE front end circuit 6, such that the RE transmitter 9 can selectively transmit a signal to each of the sectors served by the respective antenna elements 3 to 36.

Figure 4 shows an antenna arrangement in which the smart antenna 1 is to be connected to an RE receiver 7 and an RF transmitter 9 in the RF front end circuit 6. To enable the plurality of antenna elements 3 to 36 to be selectively connected to both the RE receiver 7 and the RF transmitter 9, a further switch S7 must be placed in series with the plurality of switches S1 to S6.

A disadvantage of the arrangement shown in Figure 4 is that the switches used to switch the various antenna elements tend to have inherent losses which degrade the signal being received or transmitted by the antenna 1, which cannot be corrected in subsequent stages of the signal processing. This disadvantage is heightened in the embodiment providing both transmit and receive functions due to the fact that the signal must pass through two switches, i.e. one of the switches S1 to S6 and the switch S7 which directs the signal between the RE receiver 7 and the RF transmitter 9.

It is an aim of the present invention to provide an antenna arrangement that does not suffer from the disadvantages mentioned above.

Summary of invention

According to a first aspect of the invention, there is provided an antenna arrangement comprising: two or more antenna elements; a transmitter for transmitting a signal via the antenna elements; a receiver for receiving a signal from the antenna elements; wherein for each of the two or more antenna elements there is provided: a first switch connected between the antenna element and the transmitter; a second switch connected between the antenna element and the receiver; such that the first switch and the second switch are arranged in parallel.

According to another aspect of the present invention, there is provided an integrated circuit for use with an antenna having two or more antenna elements. The integrated circuit comprises: a transmitter for transmitting a signal via the antenna elements; a receiver for receiving a signal via the antenna elements; wherein for each of the two or more antenna elements the integrated circuit further comprises: a first switch connected between said antenna element and the transmitter; and a second switch connected between said antenna element and the receiver.

According to a further aspect of the present invention, there is provided an integrated circuit for use with an antenna having two or more antenna elements. The integrated circuit comprises: a first switch connected between an antenna element and a transmitter; and a second switch connected between said antenna element and a receiver.

According to a further aspect of the present invention, there is provided an integrated circuit for use with an antenna having a first antenna element and a second antenna element. The integrated circuit comprises: a transmitter or a receiver for transmitting or receiving a signal to or from the first antenna element or the second antenna element; a switch provided in the signal path for selectively connecting a signal between said transmitter or receiver and one of said first or second antenna elements.

According to a further aspect of the present invention, there is provided an integrated circuit for use with an antenna having a plurality of antenna elements. The integrated circuit comprises: a plurality of transceivers, each transceiver corresponding to a respective antenna element; and a plurality of switches, each switch corresponding to a respective transceiver and configured to selectively connect a transmitter or a receiver of said transceiver to the corresponding antenna element.

According to a further aspect of the present invention, there is provided a method of connecting two or more antenna elements of an antenna with a transmitter for transmitting a signal via the antenna elements and a receiver for receiving a signal from the antenna elements. The method comprises the steps of: providing a first switch between an antenna element and the transmitter; providing a second switch between said antenna element and the receiver; wherein the first switch and the second switch are arranged in parallel.

Brief description of the drawings

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the following drawings, in which: Figure 1 shows the multi-band OFDM alliance (MBOA) approved frequency spectrum of a MB-OFDM system; Figure 2 shows an antenna arrangement configured as a receiver; Figure 3 shows an antenna arrangement configured as a transmitter; Figure 4 shows an antenna arrangement configured as a receiver and a transmitter; Figure 5 shows an antenna arrangement according to an embodiment of the present invention; * Figure 6 shows an antenna arrangement according to another embodiment of the present invention; Figure 7 shows an antenna arrangement according to another embodiment of the present invention; Figure 8 shows an antenna arrangement according to another embodiment of the present invention; Figure 9 shows an antenna arrangement according to another embodiment of the present invention; and Figure 10 shows an antenna arrangement according to another embodiment of the present invention.

Detailed description of preferred embodiments

The invention will be described below in relation to a smart antenna having six antenna elements. However, it will be appreciated that the invention is not restricted to embodiments having six antenna elements, but is equally applicable to an antenna having any number of antenna elements, and in particular an antenna having two or more antenna elements. The antenna elements may comprise antenna dipoles, monopoles, or any other form of antenna structure, or any combination thereof.

Furthermore, it is noted that the invention will be described in the context of an ultra-wideband antenna and communication system. However, it will be appreciated that the invention is also applicable to other antenna or communication systems.

Figure 5 shows an antenna arrangement according to a first aspect of the present invention. The antenna arrangement comprises a plurality of antenna elements 3 to 36 which are to be selectively connected to an RE receiver 7 and an RE transmitter 9.

According to a first aspect of the invention, an antenna element, for example antenna * element 3 has a first switch Sir connected between the antenna element 3 and the RF receiver 7, and a second switch S1 connected between the antenna element 3 and * the RF transmitter 9. The first switch Sir and the second switch S1 are effectively arranged in parallel with one another. As such, since the first and second switches Sir and S1 are arranged in parallel, an antenna element 3 can be selectively connected to either the RF receiver 7 or the RF transmitter 9without the signal having to pass through two switches connected in series (as shown in Figure 4), and hence without having two switching losses.

The invention has the advantage of providing an antenna arrangement that can selectively connect a plurality of antenna elements to a transceiver, but without requiring high cost switching devices. Although the invention uses more switching elements than the prior art technique, the switching elements can be of a lower quality than would otherwise be required if two switches were connected in series, thus providing an overall cost saving.

According to one embodiment of the invention as shown in Figure 6, the RF circuitry (that is, the RF receiver 7 and the RF transmitter 9) and the antenna front end comprising the switches Sir/Sit to S6rIS6t are integrated into the same electronic circuit module or single integrated circuit 60. By integrating these functions within the same semiconductor process, the switching function can be reduced in cost.

According to an alternative embodiment as shown in Figure 7, the switching function can be removed from the RF circuitry, with the switching function being provided in an integrated switching function within a single electronic module or integrated circuit 71, separate from the RF circuitry 73. As above, by integrating the switching function within the same semiconductor process, the switching function can be reduced in cost.

According to another aspect of the present invention shown in Figure 8, there is provided an antenna arrangement in which the RF transceiver (i.e. comprising the RF transmitter and RF receiver) is replicated, such that a transceiver is provided for each antenna element. For example, in an integrated circuit an RF transmitter/receiver circuit can be replicated as a functional block, such that a functional block is available for each antenna element. In this embodiment there is provided a transmitter/receiver stage (TxRx stage) TR1 to TR6 corresponding to each antenna element 3 to 36, and a corresponding switch S1 to S6 for selectively connecting a signal to/from a respective antenna element to the transmitter or receiver of each TxRx stage TR1 to TR6.

This integrated circuit or semiconductor approach has a relatively low cost of adding multiple RF stages to the RF electronic block. An advantage of this embodiment is that a signal only has to pass through one switch resistance, thereby reducing any degrading effect on a signal being transmitted to, or received from an antenna element.

Furthermore, this approach has added functionality in that an increased application flexibility can be provided In addition, by providing the antenna with separate transmitter/receiver stages selectively connected to each antenna element, it is possible to vector add the signals using well known DSP methods which further improve the performance of the wireless link by optimising the wireless link.

Figure 9 shows a further aspect of the present invention, whereby the switches for selectively connecting a signal between two or more antenna element (six shown in the embodiment) and the transmitter or receiver are provided on the same integrated circuit as the RF circuitry. The integrated circuit 90 comprises an RE receiver 7 and an RE transmitter 9. To enable the plurality of antenna elements 3 to 3 to be selectively connected to either the RF receiver 7 or the RF transmitter 9, a first switch S7 is provided in the signal path for selectively connecting a signal to the RE receiver 7 or the RE transmitter 9. A second switch S is provided in the signal path for selectively connecting the signal to one of the antenna elements. For example, for an antenna having first and second antenna elements, the switch S, is configured to selectively connect the signal to the first antenna element or the second antenna element. For an antenna having six antenna elements 3 to 36 as shown in Figure 9, the switch S may comprise a six-way switch S1 to S6 for selectively connecting a signal to or from the first to sixth antenna elements.

The embodiment of Figure 9 has an advantage over Figure 4 in that the switches can be fabricated using the same process as that used to fabricate the RE circuitry. As such, the switches can be manufactured more cost effectively, such than better quakty switches can be used to reduce the effect of having two switches connected in series.

It is noted that the bank of switches S1 to S6 of Figure 9 can also be realised in a similar manner to Figure 4, whereby the switches S1 to S6 are separate switches arranged in parallel, and having one end of each switch connected together (i.e. as an alternative to the arrangement shown in Figure 9 whereby the bank of switches is realised as a 1-to-6 way switch, or 1-to-N way switch for an antenna having N antenna elements).

Figure 9 has the advantage that the switches are integrated on the same integrated circuit as the RF circuitry, thereby enabling the switches to be fabricated using the same process as that used for fabricating the RF circuitry.

According to another aspect of the invention, the invention relates to an integrated circuit having just a transmitter or just a receiver, and a plurality of switches integrated with the transmitter or receiver for connecting a signal to/from one of a plurality of antenna elements.

According to yet another alternative embodiment as shown in Figure 10, the switching function and/or RF circuitry shown in Figures 5, 6, 7, 8 or 9 can be integrated within the antenna itself, i.e. with the antenna elements. This embodiment has the advantage of minimising signal path losses between the antenna elements and the transmitter/receiver.

The integration of the switches and RF circuitry within the antenna enables pre-processing to be carried out close to the antenna elements, which in turn enables accurate frequency conversion (mixing) to be carried out. This has the advantage of reducing the output frequency, and hence further desensitises the RF circuitry from high frequency layout issues. This is particularly important when trying to vector combine the signals to or from each of the antenna elements.

According to yet a further aspect of the invention, one or more front end processing blocks, for example a low noise amplifier LNA, down-mixer stages, up-mixer stages, power amplifier or digital signal processing (DSP) circuitry can be incorporated into the integrated circuit having the combined RF stages and antenna switches. This can be done using a low cost process, for example a CMOS process. By having the one or more front end processing blocks integrated on the same device as the RF stages and antenna switches, it is possible to process lower frequency signals on the same device, thereby avoiding signal losses. Additionally, and in line with more complex schemes, the signals, instead of simply being switched on/off, can be combined in a manner such that the vector addition of the different signals improve the overall link conditions.

The RF circuitry and antenna switches in the embodiments described above may be formed using any suitable process, including but not limited to CMOS and/or GaAs processes.

The antenna according to the present invention has the advantage of incorporating the RF stages and the antenna switches of a UWB transceiver within the same integrated circuit (and optionally within the antenna unit), which results in a lower path loss and higher performance.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim, "a" or "an' does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the claims. Any reference signs in the claims shall not be construed so as to limit their scope.

Claims

CLAIMS1. An antenna arrangement comprising: two or more antenna elements; a transmitter for transmitting a signal via the antenna elements; a receiver for receiving a signal from the antenna elements; wherein for each of the two or more antenna elements there is provided: a first switch connected between the antenna element and the transmitter; a second switch connected between the antenna element and the receiver; such that the first switch and the second switch are arranged in parallel.
2. An antenna arrangement as claimed in claim 1, wherein the transmitter, receiver, first switch and second switch are provided on the same integrated circuit.
3. An antenna arrangement as claimed in claim 1, wherein the first switch and second switch are provided on the same integrated circuit.
4. An integrated circuit for use with an antenna having two or more antenna elements, the integrated circuit comprising: a transmitter for transmitting a signal via the antenna elements; a receiver for receiving a signal via the antenna elements; wherein for each of the two or more antenna elements the integrated circuit further comprises: a first switch connected between said antenna element and the transmitter; and a second switch connected between said antenna element and the receiver.
5. An integrated circuit for use with an antenna having two or more antenna elements, the integrated circuit comprising: a first switch connected between an antenna element and a transmitter; and a second switch connected between said antenna element and a receiver.
6. An integrated circuit as claimed in claim 5, wherein the transmitter and receiver are formed in the integrated circuit.
7. An integrated circuit for use with an antenna having a first antenna element and a * second antenna element, the integrated circuit comprising: a transmitter or a receiver for transmitting or receiving a signal to or from the first antenna element or the second antenna element; a switch provided in the signal path for selectively connecting a signal between said transmitter or receiver and one of said first or second antenna elements.
8. An integrated circuit as claimed in claim 7, wherein the integrated circuit comprises a transmitter and a receiver, the integrated circuit further comprising: a second switch provided in the signal path for selectively connecting a signal to said transmitter or said receiver.
9. An integrated circuit for use with an antenna having a plurality of antenna elements, the integrated circuit comprising: a plurality of transceivers, each transceiver corresponding to a respective antenna element; and a plurality of switches, each switch corresponding to a respective transceiver and configured to selectively connect a transmitter or a receiver of said transceiver to the corresponding antenna element.
10. An integrated circuit as claimed in any one of claims 4 to 9, wherein the integrated circuit further comprises at least one of: a low noise amplifier; a down-mixer stage; an up-mixer stage; a power amplifier; or digital signal processing circuitry.
11. An integrated circuit as claimed in any one of claims 4 to 10, wherein the integrated circuit is formed using CMOS fabrication techniques.
12. An integrated circuit as claimed in any one of claims 4 to 10, wherein the integrated circuit is formed using GaAs fabrication techniques.
13. A method of connecting two or more antenna elements of an antenna with a * transmitter for transmitting a signal via the antenna elements and a receiver for receiving a signal from the antenna elements; the method comprising the steps of: * providing a first switch between an antenna element and the transmitter; providing a second switch between said antenna element and the receiver; wherein the first switch and the second switch are arranged in parallel.
14. A method as claimed in claim 13, wherein the transmitter, receiver, first switch and second switch are provided on the same integrated circuit.
15. A method as claimed in claim 13, wherein the first switch and second switch are provided on the same integrated circuit.
16. A method as claimed in claim 14 or 15, wherein the integrated circuit is formed using CMOS fabrication techniques.
17. A method as claimed in claim 14 or 15, wherein the integrated circuit is formed using GaAs fabrication techniques.