WO2021136921A1

WO2021136921A1 - Transceiver apparatus and method

Info

Publication number: WO2021136921A1
Application number: PCT/GB2020/053150
Authority: WO
Inventors: Jimmy Gin Men YIP
Original assignee: Cantor Technologies Ltd.
Priority date: 2019-12-31
Filing date: 2020-12-09
Publication date: 2021-07-08
Also published as: GB202209614D0; GB201919444D0; GB2606094B; GB2606094A

Abstract

A transceiver apparatus is provided comprising a housing, wherein the housing contains: transmitter for transmitting radio waves; a receiver for receiving radio waves; wherein the transmitter and the receiver are electrically coupled to a control circuit; wherein a planar antenna is disposed between the transmitter and the receiver, the planar antenna being configured to absorb radio waves; and wherein a resistive load is coupled to the planar antenna, the resistive load being configured to dissipate energy of the absorbed radio waves.

Description

TRANSCEIVER APPARATUS AND METHOD

The present invention relates to a transceiver apparatus and a method of manufacture thereof. In particular, but not exclusively, the invention provides an energy absorbing and dissipating structure to minimise multiple reflections and/or cross-talk between antennas within a transceiver apparatus.

Typically a transceiver unit includes a housing and a cover encasing a printed circuit board (PCB) onto which an array of transmitters and receivers are printed and electrically connected to a processor. The transmitters emit radio frequency signals, which travel out of the transceiver unit. In the case of a radar unit, the receivers receive back a portion of the transmitted signals which have been reflected off objects within range of the unit. The received signals are amplified and interpreted by the processor to establish data on the objects within range of the radar unit. Alternatively, in the case of, for example a cellular (mobile) phone or cellular (mobile phone) base station, signals are transmitted from remotely-located transmitters to be received by the receivers. The main difference between these two scenarios is that, for mobile telecommunication, the transmitted signal is not the same as the received signal, whereas for radar, it is the transmitted signal that is being received, so it is the same signal.

Some of the radio waves emitted by the transmitters may be reflected internally by the cover. These internally reflected radio waves may be reflected multiple times by the cover, housing and/or PCB and can be picked up by the receivers thereby causing interference with the received signal. The problem is exacerbated in higher frequency applications, where the frequency is of the same order of magnitude as the components of the transceiver. For example, the higher frequency of radio waves used in conjunction with automotive radar may result in an increase in the number of internal reflections and therefore an increase in the amount of 'noise’ in the received signal.

Within certain radar unit designs, the transmitted signal may also propagate inside the radar housing along the surface of the PCB, in the form of a surface wave. Where such a signal reaches the receiver, this undesirable effect is known as "cross-talk”. In view of the above, it is an object of the present invention to address the problem of internally reflected radio waves and/or cross-talk and alleviate at least one of the aforementioned disadvantages.

According to a first aspect of the present invention, there is provided a transceiver apparatus comprising a housing, wherein the housing contains: a transmitter for transmitting radio waves; a receiver for receiving radio waves; wherein the transmitter and the receiver are electrically coupled to a control circuit; wherein a planar antenna is disposed between the transmitter and the receiver, the planar antenna being configured to absorb radio waves; and wherein a resistive load is coupled to the planar antenna, the resistive load being configured to dissipate energy of the absorbeded radio waves.

Thus, the apparatus of the invention provides a radio wave absorbing and dissipating structure in the form of a planar antenna that at least partially fills the space between the transmitter(s) and receiver(s) to minimise cross-talk and absorb reflected radio waves to minimise internal reflection.

The housing according to the invention is generally transparent to the radio waves in question, although it may give rise to total internal reflection, as discussed. In the case of a radar apparatus, the housing is typically a radome. In the case of a cellular (mobile) phone, the housing is the phone case and in the case of a cellular (mobile) phone base station, the housing is typically the casing of the base station.

According to one embodiment of the first aspect, the transceiver apparatus additionally comprises a substrate, wherein the planar antenna is disposed on the substrate.

According to another embodiment of the first aspect, the planar antenna is printed on the substrate. According to a further embodiment of the first aspect, the substrate is a printed circuit board (PCB). The transmitter, the receiver, the control circuit, the planar antenna and the resistive load may be printed onto the PCB.

According to another embodiment of the first aspect the length of the planar antenna is selected so that the planar antenna is configured to absorb energy of a selected frequency of radio waves.

According to one embodiment of the first aspect, the transceiver apparatus comprises at least two planar antennas, each planar antenna being connected to its own resistive load, the respective resistive load being configured to dissipate energy of the radio waves absorbed by the connected planar antenna. According to this embodiment, at least one resistive load may have a different resistance to at least one of the other resistive load.

According to another embodiment of the first aspect, the transceiver apparatus comprises at least two planar antennas, each planar antenna being connected to the resistive load, the resistive load being configured to dissipate energy of the radio waves absorbed by the planar antennas.

According to a further embodiment of the first aspect, the transceiver apparatus comprises at least two planar antennas, wherein the length of the at least one planar antenna is different from the length of the at least one other planar antenna, such that it is configured to absorb energy of a frequency which is different from that planar antenna or those planar antennas.

According to an alternative embodiment of the first aspect, the transceiver apparatus comprises at least two planar antennas, wherein the length of each planar antenna is identical to the length of the other planar antenna(s), such that each planar antenna is configured to absorb energy of the same frequency as the other planar antenna(s).

According to an one embodiment of the first aspect, the transceiver apparatus comprises at least two planar antennas, wherein the planes of the planar antennas are aligned. According to an alternative embodiment of the first aspect, the transceiver apparatus comprises at least two planar antennas, wherein the plane of at least one planar antenna is disposed orthogonally relative to the plane of at least one other planar antenna to allow absorption of radio waves having differing polarisations.

According to a further embodiment of the first aspect, the transceiver apparatus additionally comprises a ground point electrically coupled to the planar antenna or to each planar antenna. According to this embodiment, the ground point may be a real ground point or a virtual ground point. Furthermore, the planar antenna or each planar antenna may be connected to its own ground point. Alternatively, the planar antenna or each planar antenna may be connected to the same common ground point.

The ground point may be configured to provide a potential difference across each resistive load to effectively dissipate the energy of each radio wave received by the at least one planar antenna. Providing a ground point is advantageous since it ensures that one side of the resistive load remains at zero volts and therefore maximises the potential difference across the resistive load. This increases current flow across the resistive load and ultimately enables the resistive load to absorb maximum energy from the radio wave by dissipating the energy as heat.

According to a further embodiment of the first aspect of the invention the planar antenna is a patch antenna, a comb-line antenna, or a bow-tie antenna.

According to a further embodiment of the first aspect of the invention, the planar antenna is electrically connected to the resistive load by means of a feedline. A feedline may have advantages over other ways of feeding energy to the patch, such as a via, because it is more difficult to attach a resistor to a via than to a feedline.

According to a second aspect of the invention, a radar apparatus is provided comprising the transceiver apparatus of the first aspect of the invention. According to a third aspect of the invention, an automobile is provided comprising a radar apparatus according to the second aspect of the invention.

According to a fourth aspect of the invention, a cellular phone or cellular base station is provided comprising the transceiver apparatus of the first aspect of the invention.

According to a fifth aspect of the invention, a method of manufacture of transceiver apparatus is provided comprising the steps of: providing a substrate and attaching the following elements to the substrate: a transmitter for transmitting radio waves; a receiver for receiving radio waves; a control circuit which electrically couples the transmitter and the receiver; a planar antenna disposed between the transmitter and the receiver, the planar antenna being configured to absorb radio waves; and a resistive load coupled to the planar antenna, the resistive load being configured to dissipate energy of the absorbeded radio waves; disposing the printed substrate within a housing.

According to an embodiment of the fifth aspect, the substrate is a PCB. According to this embodiment, the elements may be attached to the PCB by printing them onto the PCB.

According to another embodiment of the fifth aspect, the method comprises printing at least two planar antennas and a resistive load connected to each planar antenna, the respective resistive load being configured to dissipate energy of the radio waves absorbed by the connected planar antenna.

According to an alternative embodiment of the fifth aspect, the method comprises printing at least two planar antennas, each planar antenna being connected to the resistive load, the resistive load being configured to dissipate energy of the radio waves absorbed by the planar antennas. Optionally, one or more of the following values may be selected to absorb radio waves of a predetermined frequency, including, but not limited to: the value of the resistive load or resistor; the size of the resistor; composition, parasitic capacitance and/or parasitic inductance of the resistor; the length of the feedline; the width of the feedline; dimensions of the planar antenna; and material and/or composition of the substrate.

The value of the resistive load or resistor may be selected according to the frequency of radio waves to be absorbed. The selected value of the resistive load or the resistor may be based on at least one of the following values: the frequency of the radio waves to be absorbed, dimensions of planar antenna, characteristics of the substrate and parasitic load of the resistor.

The planar antennas may be disposed around the at least one transmitter and the at least one receiver as efficiently as possible to maximise coverage of the space therebetween with the radio absorbing and dissipating structure(s). The planar antennas may be located around and adjacent the at least one transmitter, the at least one receiver and/or other electronic components, while remaining electronically isolated therefrom.

Thus, in use, some radio waves will be internally reflected by the housing. Any internally reflected waves that are picked up by the at least one receiver would interfere with the reflected signal, providing unwanted 'noise’. However, according to the present invention, energy from internally reflected radio waves directed towards the radio wave absorbing and dissipating structure comprising a planar antenna is absorbed such that multiple internal reflections, and therefore undesirable 'noise’ in the received signal, is substantially reduced.

The apparatus may comprise a plurality of transmitters. The apparatus may comprise a plurality of receivers. The apparatus may comprise an antenna array having a plurality of transmitters and receivers.

Further features and advantages of the present invention will become apparent from the following description. Embodiments of the present invention will now be described by way of example only, with reference to the following diagrams, in which: -

Fig. 1 is a sectional schematic view of a radar apparatus comprising a radio absorbing and dissipating structure according to one embodiment of the present invention;

Fig. 2 is a schematic plan view of a first embodiment of the radio frequency absorbing and dissipating structure of Figure 1 showing a single patch antenna and via to ground;

Fig. 3 is a schematic plan view of a second embodiment of the radio frequency absorbing and dissipating structure of Figure 1 showing a single patch antenna and a virtual ground; Fig. 4 is a schematic plan view of a third embodiment of the radio frequency absorbing and dissipating structure of Figure 1 showing two patch antennas electrically connected to a common resistor;

Fig. 5 is a schematic plan view of a fourth embodiment of the radio frequency absorbing and dissipating structure of Figure 1 showing two patch antennas in orthogonal relation, each electrically connected to a respective resistor and a via to ground;

Fig. 6 is a schematic plan view of a fifth embodiment of the radio frequency absorbing and dissipating structure of Figure 1 showing two patch antennas in orthogonal relation electrically connected to a single resistor;

Fig. 7 is a schematic plan view of a sixth embodiment of the radio frequency absorbing and dissipating structure of Figure 1 showing four patch antennas, each associated with a respective resistor and all connected to a via to ground;

Fig. 8 is a schematic plan view of a seventh embodiment of the radio frequency absorbing and dissipating structure of Figure 1 showing four patch antennas each having a respective resistor;

Fig. 9 is a schematic plan view of a eighth embodiment of the radio frequency absorbing and dissipating structure of Figure 1 showing four patch antennas connected to a single resistor; and

Fig. 10 is a schematic plan view of a ninth embodiment of the radio frequency absorbing and dissipating structure of Figure 4 showing the patch antennas arranged in a tessellating pattern. A radar apparatus is shown generally at 21 in Figure 1. The radar apparatus 21 comprises a housing 10 with a base and sidewalls, and a cover 12. The housing 10 and cover 12 are provided to enclose and protect the electronic radar components housed therein. A substrate in the form of a printed circuit board (PCB) 17 is located on the base of the housing 10.

An array of transmitter antennas 15 are printed on the PCB 17. The transmitter antennas 15 are electrically coupled to a control circuit (not shown) and are arranged to emit radio frequency waves. An example of one of the radio waves emitted by the transmitter antennas 15 is shown by an arrow 11. An array of receivers 16 are also printed on the substrate 17. The receivers 16 are coupled to the control circuit via amplifiers (not shown) and are arranged to receive reflected radio waves. The control circuit (not shown) controls the transmitter antennas 15 and receiver antennas 16 and includes a processor and other electronic components (not shown) with electrical interconnections disposed on the PCB 17.

A plurality of frequency selective absorbers or radio wave absorbing and dissipatingabsorbing and dissipating and dissipating structures are shown generally at 14. The radio wave absorbing and dissipating structures 14 are located on the PCB 17 in spaces between the transmitter antennas 15, receiver antennas 16 and other electronic components. Each radio wave absorbing and dissipating structure comprises a patch antenna 18 in the present examples, although other planar antennas, especially those which can be printed onto a PCT, such as comb-line antennas, could be used as an alternative.

Several embodiments of the frequency selective absorbers or radio wave absorbing and dissipating structures 14 are described herein with reference to Figures 2 to 10. In order to minimise repetition, similar features of the radio wave absorbing and dissipating structure 14 described subsequently are numbered with a common two-digit reference numeral and are differentiated by a third and/or fourth digit placed before the two common digits. Such features are structured similarly, operate similarly, and/or have similar functions as previously described unless otherwise indicated. A first embodiment of a radio wave absorbing and dissipating structure 114, comprising one patch antenna 118 is shown in Figure 2. The patch antenna 118 is electrically connected to a resistive load in the form of a resistor 19, by an electrical connection in the form of a first feed line 121. Another electrical connection in the form of a second feed line 122 electrically connects the resistor 19 to a ground via 130.

The ground via 130 extends through the PCB 17 substrate and provides a real direct current (DC) ground for the targeted signal. The presence of the ground via 130 introduces a potential difference across the resistor 19. Due to the potential difference (i.e. voltage) across the resistor 19 in use, current flows through the resistor 19, which energy is then turned into heat, thereby absorbing and dissipating and dissipating the energy from the radio waves.

The patch antenna 118 has a length depicted by an arrow 20. The dimensions of the patch antenna 118 are predetermined to enable radio waves of a particular frequency to be received by the patch antenna 118.

The second feedline 122 can have a different length and width compared with the first feedline 121. The dimensions (length and width) of the two feedlines 121, 122 determine the placement position, size and resistive value of the resistor 19 with the aim of absorbing and dissipating energy of the received radio wave by matching the resistor 19 value with the impedance of the incoming wave. For most applications, the resistance value ranges from a few ohms to a few hundred ohms. Factors such as the composition, parasitic capacitance and induction of the resistor 19, must be considered for high frequency applications, in which these parameters have more significant effects on the absorption of the radio waves received by the patch antenna 118. As a result, the length of the patch antenna 118, the length and width of the feedlines 121, 122, and the location, size and value of the resistor 19 are used to determine the frequency of radio waves to be absorbed. These parameters can be controlled to allow radio waves of a pre-determined frequency to be absorbed. A second embodiment of a radio wave absorbing and dissipating structure 214 incorporating the single patch antenna 118 is shown in Figure 3. The second feed line 122 is electrically connected to the resistor 19 at one end and a radial stub 141 at a distal end. The radial stub 141 creates a virtual ground for alternating current (AC) at point 140. The virtual AC ground point 140 introduces a potential difference across the resistor 19 so that the energy of the received radio wave in use, is absorbed by the flow of current therethrough.

According to an alternative embodiment, the virtual ground 140 is created by a straight stub (not shown) as an open transmission line, although the radial stub 141 of Figure 3 is advantageous as it can function with radio waves having a broader bandwidth.

The resistor 19 can be any suitable component that functions to provide a resistive load. Examples of suitable resistors include surface mount technology (SMT) resistors, printed resistor, in which resistive ink is printed directly on to PCB 17 or thin film resistor. SMT resistors are advantageous since they are inexpensive and have a reliable resistive value.

Again, the dimensions of the patch antenna 118 such as a length of the patch depicted by arrow 20 is preselected according to the frequency of radio waves to be absorbed. Advantageously, the length 20 is equivalent to about half of the wavelength of the radio waves to be absorbed. Other values such as resistive load of the resistor 19 and the length of the first and second feedlines 121, 122 are also preselected based on the frequency of radio waves to be dissipated. Additional influencing factors such as dielectric constants and characteristics of the PCB 17 are either taken into account or actively managed to ensure the absorption of radio waves of a certain frequency.

Other embodiments may include different patch antenna 118 designs or antenna arrays, some examples of which are described below.

A third embodiment of a radio wave absorbing and dissipating structure 314 including two patch antennas 218, 318 is shown in Figure 4. Each patch antenna 218, 318 is aligned and a resistive load in the form of a resistor 119 is electrically connected therebetween using first and second feedlines 221, 222, respectively. The length 120, 220 of the patch antennas 218, 318 as well as the size and resistance of the resistor 119 are calculated based on the frequency of radio waves to be dissipated, and other factors such as dielectric constants and characteristics of the PCB 17. Advantageously, the length 120 and 220 is equivalent to about half of the wavelength of the radio waves to be absorbed.

In use, energy from the internally reflected radio wave 13 or surface waves along the PCB 17 is absorbed by the patch antennas 218, 318 and dissipated by the resistor 119. A virtual ground point (not shown) is created at a location inside the resistor 119 or on the first and second feedlines 221, 222 depending on the precise design, properties and dimensions of the radio wave absorbing and dissipating structure 314. Alternatively, patch antennas 218 and 318 may provide a virtual ground for one another.

Values such as the length of the feedlines 221, 222, the location and value of the resistor 119 can be varied according to the design of the radio wave absorbing and dissipating structure 314. Since the length 120, 220 of the patch antennas 218, 318 defines the frequency of the signal absorbed by the antennas 120, 220, modifying the lengths of the patch antennas 218, 318 and feedlines 221, 222 can enable the radio wave absorbing and dissipating structure 314 to received and absorb at least two different frequencies of radio waves simultaneously.

According to a fourth embodiment shown in Figure 5, an alternative arrangement of a radio wave absorbing and dissipating structure 414 is shown. The radio wave absorbing and dissipating structure 414 includes two patch antennas 418, 518 arranged in orthogonal relation. The patch antenna 418 covers electric field in a vertical polarisation and the patch antenna 518 covers electric field in a horizontal polarisation. Each patch antenna 418, 518 is electrically connected to a respective resistor 219 by a respective first feedline 321, 421, and then to a common ground via 230 by a second feedline 322, 422. The resistors 219 can have the same value, in which case the feedlines 321, 421 will have similar dimensions. Alternatively, the resistors 219 have a different size and value. Again, variables such as lengths and widths of feedlines 321, 322, 421, 422 and resistor 219 properties are pre-selected according to the desired radio wave frequency absorption.

According to a fifth embodiment shown in Figure 6, another arrangement of a radio wave absorbing and dissipating structure 514 is shown. The radio wave absorbing and dissipating structure 514 comprises two patch antennas 618, 718 are arranged in orthogonal relation with a common resistor 319 located therebetween. Again, this arrangement is advantageous to allow different polarisations of radio waves to be received, where the reflected waves might be affected by polarisation. As for the embodiment of Figure 4, patch antennas 618 and 718 may provide a virtual ground for one another.

Alternative arrangements and different patterns and combinations of patch antennas 18, 118, 218, 318, 418, 518, 618, 718 can be applied to the PCB 17 with further embodiments shown in Figures 7 to 9, each of which shows four patch antennas 818, 918, 1018, 1118, positioned at right angles to one another.

Figure 7 shows a radio wave absorbing and dissipating structure 614 consisting of four patch antennas 818, 918, 1018, 1118 each electrically connected to a respective resistor 419 and a common DC ground via 330. The individual resistors 419 associated with each patch antenna 818, 918, 1018, 1118, enable different frequencies of radio waves to be absorbed by controlling the size and value of each resistor 419 and the dimensions of each antenna patch 818, 918, 1018, 1118 as well as the width and length of the feedlines. The arrangement of the patch antennas 818, 918, 1018, 1118 at right angles means that both horizontal and vertical polarisations of radio waves can be absorbed by the radio wave absorbing and dissipating structure 614. The common ground via 330 is used to provide a ground for each of the four patch antennas 818, 918, 1018, 1118. The resistors 419 may all have a different value, in which case the dimensions of the feedlines will differ to absorb the energy from radio waves of different frequencies. Alternatively, the resistors 419 may all have the same value. Figure 8 shows a radio wave absorbing and dissipating structure 714 similar to that shown in Figure 7. However, a virtual ground 240 is created around the centre of the radio wave absorbing and dissipating structure 714 instead of the real ground via 330.

An alternative embodiment of a radio wave absorbing and dissipating structure 814 is shown in Figure 9, in which the patch antennas 818, 918, 1018, 1118 are joined by feedlines to a common resistor 519. The resistor 519 is a thin film or a printed resistor, rather than a surface mount resistor.

According to a further embodiment, the patch antennas can be arranged in any suitable pattern according to the desired degree of radio wave absorption and anticipated amount of interference from cross-talk and/or reflected radio waves. The patch antennas may be positioned between the transmitter antennas 15 and the receiver antennas 16. This ensures the space between electronic components on the PCB 17 is usefully filled with antennas to absorb radio waves and minimise cross-talk and/or internal reflections.

According to another embodiment, patch antennas are arranged to maximise coverage of radio wave absorbing and dissipating structure in any free space on the PCB 17. Figure 10 shows an energy absorbing and dissipating structure 914 in which the patch antennas 218, 318 are arranged in a tessellating pattern to efficiently cover available space between transmitter antennas 15 and receiver antennas 16 to maximise the opportunity for absorption of internally reflected radio waves 13 and radio waves propagating along the surface of the PCB 17.

The radar apparatus 21 may comprise a plurality of radio wave absorbing and dissipating structures. The radar apparatus 21 may include any embodiment or any combination of embodiments of radio wave absorbing and dissipating structures 14, 114, 214, 314, 414, 514, 614, 714, 814, 914. Thus a plurality of any of the radio wave absorbing and dissipating structures 14, 114, 214, 414, 514, 614, 714, 814, 914 may be disposed on the PCB 17 substrate. Prior to assembly of the radar apparatus 21, the electronic components are manufactured. The PCB 17 is cut to the requisite size. According to one embodiment of a method of manufacture, electronic components are then printed onto the PCB 17, such as the transmitter antennas 15, receiver antennas 16, control circuitry and electrical interconnections. A printing step is used to locate the radio wave absorbing and dissipating structure 14 in the form of patch antennas 18 and resistors 19 in the remaining spaces between other electronic components. The radio wave absorbing and dissipating structure 14 remains electrically isolated from the transmitter antennas 15, receiver antennas 16 and the control circuitry. Thus, the printing of the radio wave absorbing and dissipating structure 14 consists of one additional printing pattern in the manufacturing process which is simple and cost effective.

The printed PCB 17 is disposed within the housing 10 and the cover 12 is sealed in place so that the radar apparatus 21 is ready for use.

According to an alternative embodiment of the method of manufacture includes the step of providing a surface mount resistor, which is soldered in place on the surface of the PCB 17 simultaneously with the soldering of other electronic components.

In use, the radar apparatus 21 is used as a detection system whereby the transmitter antennas 15 emit radio waves. The radio waves pass through the cover 12 and reflect off surrounding objects. Reflected radio waves are picked up by the receiver antennas 16. These signals are amplified and processed by the processer to determine properties of the objects, such as the range, angle, or velocity. The radar apparatus 21 can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.

Some of the radio waves emitted by the transmitter antennas 15 are reflected internally within the housing 10 by the cover 12 of the radar apparatus 21 as depicted by arrow 13. Where these internally reflected radio waves 13 are directed to the spaces between the transmitter antennas 15 and the receiver antennas 16, they are picked up by the patch antennas 18. The patch antennas 18 receive the internally reflected radio wave and the energy from the waves is dissipated by the resistive load 19. Thus, the number of multiple internal reflections from the housing 10 and the cover 12 are minimised by the presence of the radio wave absorbing and dissipating structure 14.

Although particular embodiments of the invention have been disclosed herein in detail, this is by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the statements of invention. The Figures 1 to 10 are schematic and illustrative drawings only and are not to be considered accurate or scale representations of components therein or their relative dimensions.

It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the scope of the invention as defined by the statements of invention. For example, the patch antennas 18 may be disposed on the PCB 17 to occupy the majority of the remaining space alongside the radar circuitry and components. The angle at which the patch antennas 18 are disposed may be variable and optimally selected for each radar apparatus 21. Various types of resistor have been described as optional embodiments of the resistive load. Any other resistor type or electronic component that functions as a resistive load can be used as part of the radio wave absorbing and dissipating structure 14.

The structure of the radio wave absorbing and dissipating structure 14 is not limited to that shown in the embodiments. Any number, layout and/or arrangement of patch antennas and coupled resistive loads can be used providing that the configuration results in the absorption of the energy of received radio waves.

Various aspects and embodiments of the invention are defined by the following numbered clauses:

1. A radar apparatus comprising a housing, wherein the housing is configured to contain: at least one transmitter for transmitting radio waves; at least one receiver for receiving reflected radio waves; wherein the at least one transmitter and receiver are electrically coupled to a control circuit; and at least one radio wave absorbing structure, wherein the radio wave absorbing structure is located in at least a portion of the space between the at least one transmitter and receiver.

2. The radar apparatus of clause 1, wherein the at least one radio wave absorbing structure at least partially fills the space between the transmitter(s) and receiver(s) to minimise cross-talk and absorb reflected radio waves to minimise internal reflection.

3. The radar apparatus of clause 1 or 2 comprising a plurality of radio wave absorbing structures.

4. The radar apparatus of any preceding clause, wherein the radio wave absorbing structure(s) is/are configured to absorb energy of a pre-selected frequency of radio waves.

5. The radar apparatus of any preceding clause, wherein, the radio wave absorbing structure (s) is/are disposed around the at least one transmitter and the at least one receiver to occupy at least a portion of the area therebetween.

6. The radar apparatus of any preceding clause further comprising electronic components coupled to the control circuit, the at least one radio wave absorbing structure being disposed around the electronic components to occupy at least a portion of the space therebetween.

7. The radar apparatus of any preceding clause, wherein the at least one radio wave absorbing structure is electrically isolated from the at least one transmitter, the at least one receiver, the electronic components and the control circuit.

8. The radar apparatus of any preceding clause, wherein the radio wave absorbing structures are arranged to occupy at least half of the space surrounding the at least one transmitter, the at least one receiver, the electronic components and/or the control circuit components of the radar apparatus.

9. The radar apparatus of any preceding clause, wherein the at least one radio wave absorbing structure is located on a substrate, preferably wherein the at least one radio wave absorbing structure is printed on a substrate.

10. The radar apparatus of clause 9, wherein the substrate is a printed circuit board (PCB).

11. The radar apparatus of any of clauses 1 to 8, wherein at least part of the at least one radio wave absorbing structure is attached to a substrate.

12. The radar apparatus of clause 11, wherein at least part of the, or each, radio wave absorbing structure is soldered into position on the substrate.

13. The radar apparatus of any preceding clause, wherein the radio wave absorbing structure comprises at least one patch antenna adapted to receive a radio wave.

14. The radar apparatus of clause 13, wherein the at least one patch antenna is adapted to receive a radio wave of a preselected frequency range.

15. The radar apparatus of any preceding clause, wherein the radio wave absorbing structure further comprises a resistive load electrically coupled to the at least one patch antenna, wherein the resistive load and the patch antenna are configured such that the resistive load dissipates the energy of the received radio wave.

16. The radar apparatus of clause 15, wherein the resistive load comprises a resistor, preferably a resistor selected from the group consisting of surface mount resistors, printed resistors and thin film resistors. 17. The radar apparatus of any preceding clause, wherein the radio wave absorbing structure comprises at least two patch antennas, each adapted to receive a radio wave

18. The radar apparatus of clause 17, where wherein the at least two patch antennas are adapted to receive a radio wave of a preselected frequency range.

19. The radar apparatus of clause 17, wherein the at least two patch antennas are adapted to receive radio waves of different preselected frequency ranges.

20. The radar apparatus of any of clauses 17 to 19, wherein the patch antennas are aligned.

21. The radar apparatus of any of clauses 17 to 19, wherein the patch antennas are arranged at an angle relative to one another, preferably wherein the patch antennas are disposed orthogonally relative to one another.

22. The radar apparatus of any of clauses 17 to 19, wherein the at least two patch antennas are arranged to receive radio waves of at least two different polarisations. Optionally, at least two of the patch antennas are arranged in orthogonal relation.

23. The radar apparatus of any of clauses 17 to 22 comprising a resistive load electrically coupled to the at least two patch antennas, wherein the resistive load and the patch antennas are configured such that the resistive load dissipates the energy of the received radio waves.

24. The radar apparatus of any of clauses 17 to 22, comprising at least two resistive loads, each electrically coupled to a respective patch antenna, wherein the resistive loads and the patch antennas are configured such that the respective resistive load dissipates the energy of the received radio wave from each associated patch antenna. 25. The radar apparatus of any preceding clause comprising four patch antennas each adapted to receive a radio wave.

26. The radar apparatus of clause 25, wherein the at least four patch antennas are adapted to receive radio waves of a preselected frequency range.

27. The radar apparatus of clause 25, wherein the at least four patch antennas adapted to receive radio waves of different preselected frequency ranges.

28. The radar apparatus of any of clauses 25 to 27, wherein the at least four patch antennas are arranged to receive radio waves of at least two different polarisations.

29. The radar apparatus of any of clauses 25 to 28 further comprising a resistive load electrically coupled to the at least four patch antennas, wherein the resistive load and the patch antennas are configured such that the resistive load dissipates the energy of the received radio waves.

30. The radar apparatus of any of clauses 25 to 28 comprising at least four resistive loads, each electrically coupled to a respective patch antenna, wherein the resistive loads and the associated patch antennas are configured such that the resistive loads dissipate the energy of the received radio wave from each patch antenna.

31. The radar apparatus of clauses 15 to 30, wherein the resistive load is coupled to the, or each, patch antenna by a feedline.

32. The radar apparatus of clauses 13 to 31, wherein the at least one radio wave absorbing structure comprises a ground point electrically coupled to each patch antenna.

33. The radar apparatus of clause 32, wherein the ground point is located on one side of a resistive load and the patch antenna is located on an opposing side of the resistive load. The radar apparatus of clause 32 or 33, wherein the ground point is a virtual ground. The radar apparatus of clause 34, wherein the ground point is an alternating current (AC) ground. The radar apparatus of clause 33, wherein the ground point is a real ground. The radar apparatus of clause 36, wherein the ground point is a direct current (DC) ground. The radar apparatus of clause 37, wherein the DC ground is provided on a substrate. The radar apparatus of clause 38, wherein the substrate is a PCB and the DC ground comprises a via extending through a PCB. The radar apparatus of any preceding clause, wherein the patch antennas are disposed around the at least one transmitter and the at least one receiver as efficiently as possible to maximise coverage of the space therebetween with the radio absorbing structure (s). The radar apparatus of any preceding clause, wherein each radio wave absorbing structure is arranged in a tessellating pattern to maximise coverage of space between the electronic components of the radar apparatus. The radar apparatus of any preceding clause comprising a plurality of transmitters and/or a plurality of receivers. The radar apparatus of any preceding clause, wherein the control circuit comprises a processor adapted for calculation and processing of data, preferably wherein the control circuit is electrically isolated from the radio wave absorbing structure. 44. An automotive radar system comprising the radar apparatus of any preceding clause.

45. A method of manufacture of radar apparatus comprising the steps of: providing a substrate, printing a radar antenna array and connecting circuitry on the substrate; and adding at least one radio wave absorbing structure on at least a portion of the remaining space around the radar antenna array and circuitry.

46. The method of clause 45, wherein the substrate comprises a printed circuit board.

47. The method of clause 45 or 46, wherein the radio wave absorbing structure comprises at least one patch antenna configured to receive radio waves, and electrically connected to a resistive load.

48. The method of clause 46 including the step of printing a plurality of patch antennas onto at least a portion of the remaining space around the radar antenna array and circuitry.

49. The method of clause 48 including the step of printing patch antennas on the substrate in a tessellating pattern.

50. The method of any of clauses 47 to 49, wherein the resistive load comprises a resistor.

51. The method of clause 50, including the step of printing the resistor onto the substrate.

52. The method of clause 51 including printing resistors on tracks of a printed circuit board. 53. The method of any of clauses 47 to 52 including printing resistive ink on to the substrate to form the resistive load.

54. The method of clause 50, including the step of bonding surface resistors to the substrate as part of the radio wave absorbing structure.

55. The method of clause 54 includingthe step of soldering a surface mountable resistor to a printed circuit board.

56. The method of clause 50 including the step of providing a thin-film resistor coupled to the substrate and electrically connecting the thin film resistor to the radio wave absorbing structure.

57. The method of clause 47 including electrically coupling one end of the resistive load to the patch antenna and an opposing end of the resistive load to a ground point.

58. The method of clause 57, wherein the ground point is a real direct current (DC) ground.

59. The method of clause 57, wherein the ground point is a virtual ground point.

60. The method of any of clauses 45 to 59, including providing a plurality of radio wave absorbing structures.

61. A radar apparatus comprising: a substrate, a radar antenna array located on the substrate, and a radio wave absorbing structure located on the substrate and electrically isolated from the radar antenna array.

62. The radar apparatus of clause 61, wherein radio wave absorbing structure is configured to absorb energy from reflected radio waves. 63. The radar apparatus of clause 62, wherein radio wave absorbing structure comprises at least one patch antenna electrically connected to a resistor.

64. The radar apparatus of any of clauses 61 to 63, wherein the radio wave absorbing structure comprises two aligned patch antennas with a resistor therebetween.

65. The radar apparatus of any of clauses 61 to 63, wherein the radio wave absorbing structure comprises two aligned patch antennas and wherein the patch antennas are arranged at an angle relative to one another, with a resistor substantially centrally located.

66. The radar apparatus of clause 65, wherein the patch antennas are disposed orthogonally relative to one another.

67. The radar apparatus of any of clauses 61 to 66, wherein the radio wave absorbing structure is printed on the substrate.

68. The radar apparatus of any of clauses 61 to 67, comprising a housing to contain the substrate and printed electronic components.

69. An apparatus comprising: at least one transmitter for transmitting an electromagnetic wave signal; at least one receiver for receiving a reflected electromagnetic wave signal; wherein the at least one transmitter and receiver are electrically coupled to a control circuit; and a frequency selective absorber, wherein the frequency selective absorber is located in at least a portion of the space between the at least one transmitter and receiver, and configured to absorb a preselected electromagnetic wave signal.

70. The apparatus of clause 69, wherein the frequency selective absorber comprises a means for absorbing an electromagnetic wave signal, preferably wherein the frequency selective signal absorber is in the form of a radio wave absorbing structure located around and between the at least one transmitter and receiver.

Claims

1. A transceiver apparatus comprising a housing, wherein the housing contains: a transmitter for transmitting radio waves; a receiver for receiving radio waves; wherein the transmitter and the receiver are electrically coupled to a control circuit; wherein a planar antenna is disposed between the transmitter and the receiver, the planar antenna being configured to absorb radio waves; and wherein a resistive load is coupled to the planar antenna, the resistive load being configured to dissipate energy of the absorbed radio waves.

2. The transceiver apparatus of claim 1 additionally comprising a substrate, wherein the planar antenna is disposed on the substrate.

3. The transceiver apparatus of claim 2, wherein the planar antenna is printed on the substrate.

4. The transceiver apparatus of claim 2 or 3, wherein the substrate is a printed circuit board (PCB).

5. The transceiver apparatus of claim 4, wherein the transmitter, the receiver, the control circuit, the planar antenna and the resistive load are printed onto the PCB.

6. The transceiver apparatus of any preceding claim, wherein the length of the planar antenna is selected so that the planar antenna is configured to absorb energy of a selected frequency of radio waves.

7. The transceiver apparatus of any preceding claim comprising at least two planar antennas, each planar antenna being connected to its own resistive load, the respective resistive load being configured to dissipate energy of the radio waves absorbed by the connected planar antenna.

8. The transceiver apparatus of claim 7, wherein at least one resistive load has a different resistance to at least one other resistive load.

9. The transceiver apparatus of any of claims 1 to 6 comprising at least two planar antennas, each planar antenna being connected to the resistive load, the resistive load being configured to dissipate energy of the absorbed radio waves absorbed by the planar antennas.

10. The transceiver apparatus of any of claims 7 to 9, wherein the length of the at least one planar antenna is different from the length of the at least one other planar antenna, such that it is configured to absorb energy of a frequency which is different from that planar antenna or those planar antennas.

11. The transceiver apparatus of any of claims 7 to 9, wherein the length of each planar antenna is identical to the length of the other planar antenna(s), such that each planar antenna is configured to absorb energy of the same frequency as the other planar antenna(s).

12. The transceiver apparatus of any of claims 7 to 11, wherein the planes of the planar antennas are aligned.

13. The transceiver apparatus of any of claims 7 to 11, wherein the plane of at least one planar antenna is disposed orthogonally relative to the plane of at least one other planar antenna to allow absorption of radio waves having differing polarisations.

14. The transceiver apparatus of any preceding claim, additionally comprising a ground point electrically coupled to the planar antenna or to each planar antenna.

15. The transceiver apparatus of claim 14, wherein the ground point is a real ground point or a virtual ground point.

16. The transceiver apparatus of claim 14 or 15, wherein the planar antenna or each planar antenna is connected to its own ground point.

17. The transceiver apparatus of claim 14 or 15, wherein the planar antenna or each planar antenna is connected to the same common ground point.

18. The transceiver apparatus of any preceding claim, wherein the planar antenna is a patch antenna, a comb-line antenna or a bow-tie antenna.

19. The transceiver apparatus of any preceding claim, wherein the planar antenna is electrically connected to the resistive load by means of a feedline.

20. A radar apparatus comprising the transceiver apparatus of any preceding claim.

21. An automobile comprising a radar apparatus of claim 20.

22. A cellular phone or cellular base station comprising the transceiver apparatus of any of claims 1 to 19.

23. A method of manufacture of transceiver apparatus comprising the steps of: providing a substrate and attaching the following elements to the substrate: a transmitter for transmitting radio waves; a receiver for receiving radio waves; a control circuit which electrically couples the transmitter and the receiver; a planar antenna disposed between the transmitter and the receiver, the planar antenna being configured to absorb radio waves; and a resistive load coupled to the planar antenna, the resistive load being configured to dissipate energy of the absorbed radio waves; disposing the printed substrate within a housing.

24. The method of claim 23, wherein the substrate is a PCB.

25. The method of claim 24, wherein the elements are attached to the PCB by printing them onto the PCB.

26. The method of claim to 25 comprising printing at least two planar antennas and a resistive load connected to each planar antenna, the respective resistive load being configured to dissipate energy of the radio waves absorbed by the connected planar antenna.

27. The method of claim 25, comprising printing at least two planar antennas, each planar antenna being connected to the resistive load, the resistive load being configured to dissipate energy of the radio waves absorbed by the planar antennas.