GB2535294A

GB2535294A - Improvements to the adaptation of a filter performance

Info

Publication number: GB2535294A
Application number: GB1521766.4A
Authority: GB
Inventors: gerald smith David
Original assignee: Global Invacom Ltd
Current assignee: Global Invacom Ltd
Priority date: 2014-12-12
Filing date: 2015-12-10
Publication date: 2016-08-17
Also published as: GB201521766D0

Abstract

The performance of filter 14 is adapted, after testing the operation of the filter, by applying at least one portion of a sheet material 24 (e.g. a dielectric such as polyimide) to the filter, altering its operation. An actual parameter (e.g. limit values for frequency) of the filter 14 is compared with the required value, the material being applied after an unacceptable comparison. The filter may be formed on a PCB and the sheet material may be selected to have particular dimensions, such that it covers only a certain part of the filter as in the figure, or so that a certain thickness (e.g. in the range 30-60 microns) is used. A set with differing dimensions may be available and a reference table used to select them, based on the comparison. The filter may be used for reception of digital television services e.g. in conjunction with Low Noise Blocks (LNBs).

Description

Improvements to the adaptation of a filter performance The invention relates to apparatus for use in the receipt and processing of digital data and, in particular, in relation to one or more filters which are provided in the apparatus and the ability to adapt the operation of the filters to suit specific operational requirements.

In the provision of apparatus to receive digital data signals, such as signals of the type which allow television and/or radio services to he generated therefrom, the apparatus will typically include one or more Low Noise Blocks (LNB's). The Low Noise Block is provided in conjunction with a waveguide and the waveguide and LNB are typically mounted on an arm at a fixed distance from, and positioned in front of, the reflecting surface of an antenna dish. Thus the signals which are received from one or more satellites are reflected from the dish surface towards the waveguide. The waveguide collects the wanted data signals within a given frequency range and the data signals are passed from the waveguide to the LNB at which the data signals are processed to provided the same in a suitable output format.

The suitable output format can vary depending on the particular use of the data output from the LNB, specific frequency ranges at which the data is received and required to be provided at the output and/or the distribution system connected to the output to allow the onward transmission of the data signals to apparatus at which the data signals can be used to generate the video and/or audio on connected display screens and/or speakers.

In different geographical areas, different frequency bands are required to be used and, for example, in Europe, the frequency range used for the transmission of the data signals to the antenna assemblies is 10.7 to 12.75GHz, but this can vary depending on the geographical location at which the apparatus is to be used.

Furthermore, the data signals can he provided with different polarities and with different bands such that, in one example, the data signals can be provided in Vertical Low, Vertical High, Horizontal Low and Horizontal High bands.

Typically, a plurality of Local Oscillators will be provided within the LNB to appropriately locate and separate the different bands as they pass through the processing means and this can include for example, providing a first output with vertical hand data signals and another output with horizontal band signals so that all of the data signals that have been received and are required, can be available from the outputs. The particular data which is subsequently retrieved is dependent upon the user selection of a particular television or radio programme and the appropriate data is identified and the particular output from which the data can be retrieved is identified and used. This can be repeated for each of a plurality of users who have broadcast data receivers which are all connected to the same outputs via a multi user distribution network.

In many cases the received data signals are required to he selectively amplified, mixed and then up and/or downconverted in order to move the received data signal bands into a frequency range which is best suited for separation, processing and onward transmission. However other considerations also have to be taken into account, such as whether the new frequency range will cause interference with other systems (such as mobile phone systems) and/or limitations on the frequency range which can be accommodated in the distribution network (for example coaxial cable has a relatively limited frequency range capability).

As a result of these limitations and possible interference, there is a need for LNB's which are to be provided for particular distribution apparatus to perform accurately in the provision of data signals in terms of the control of the output to be within predefined frequency ranges and, importantly for the LNB to operate continuously in this manner over its life span of operation which may be many years. While this could be achieved by the careful construction of "one off" LNB's for specifically designed apparatus, this is not practical when the system is operated by a satellite broadcast provider which may need to distribute data signals to many thousands or millions of subscribers such that at each subscriber location there is required to be provided at least one LNB which operates in a required manner within relatively tight operational parameters and which, once installed, is required to continue to operate within these tight parameters.

In order to achieve the operation of the LNB to process and produce reliable and usable data signals within the required frequency range parameters, and without the need to provide switching means in the LNB, the LNB can be provided with at least one filter which filters out and hence prevents data signals at unwanted frequencies from being processed and passed on for distribution. However it is critical for the successful operation of the LNB that the filter performs with sufficient accuracy to allow the required frequency parameters to he achieved, especially when, in certain cases, the whole frequency band of required signals is to he transmitted to and along the distribution cable and therefore the frequency bandwidth isrelatively wide and therefore potentially very close to other frequencies which may be used for other purposes and which therefore may be a potential source of interference to the service if the frequency bandwidth uses is inaccurate.

The filters are typically formed of conductive material applied to, and provided as part of, a. printed circuit board within the LNB and, while this is a practical means of providing the filter it is found that the dielectric constant value of the PCB material on which the filter is formed varies so that this and other manufacturing parameters such as variations in the depth of the filter track material or the width of the track, can cause the operation of the filter to vary from one LNB to another. The result of this is that the filtering parameters can differ from LNB to another which, in turn, can mean that many of the LNB's may operate outside of the acceptable limits.

In order to overcome this problem, a conventional step could be to test each filter and then tune the same as required at a point during the manufacture of the I,NB's but the time required to manually tune each filter is time consuming and is unacceptable for large scale manufacturing of many thousands of the LNB's. .Another possible solution is to test the performance of each filter of each LNB and, if it is detected that the filter is operating outside of required parameters, to add solder material to the PCB in order to change the operating parameters of the filter. However, the use of solder material is difficult to control with sufficient accuracy during the manufacturing process and therefore does not achieve the required alteration in the performance of the filter, Furthermore the return loss from the filter is uncontrollable in this process.

An aim of the present invention is therefore to provide an LNB apparatus which includes at least one filter and in which the filter can be more accurately adapted, if required, to operate within predetermined operating parameters. A further aim of the present invention is to provide a method which allows the efficient alteration of the performance of a filter within the LNB during the manufacturing process and in a manner which allows the testing and alteration to be reliably performed and in a sufficiently efficient manner so as to allow the same to be performed in large volume manufacturing of the ',NB.

In a first aspect of the invention there is provided a method for the adaptation of the performance of a filter for use to provide a required frequency range of received data signals for use by apparatus in relation to which the filter is in connection, said method including the steps of; testing the operation of the filter to identify the actual value of at least one parameter, comparing the actual value with a required value for the at least one parameter and wherein, if the actual value differs from the required value by more than an acceptable amount, applying at least one portion of a sheet material to the filter to change the actual value so that the difference between the actual and required values are at, or less than, said acceptable amount.

In one embodiment the said at least one parameter is indicative of the limit values for the frequency range for data signals to pass through the filter in operation and it is the filter frequency range which is altered by the application of the portion of sheet material.

In one embodiment the test performed on the operation of the filter is with regard to the level of image rejection of the filter which is then compared with a predetermined acceptable image rejection value and if the detected value is at or below the acceptable value then the filter is deemed acceptable and no adaptation is required but if the detected value is greater, adaptation of the filter is required by the application of a selected portion of sheet material to the filter.

In one embodiment the method includes the step of forming the filter on a base material.

Typically the said at least one portion of sheet material is adhered to filter by a layer of adhesive provided on the portion of sheet material.

In one embodiment the said limit value is an end limit of the required frequency range of the data signals which can pass through the filter.

In one embodiment both the upper and lower limit values of the frequency range are adjusted. Typically the upper and lower limit values of the frequency range are adjusted such that the bandwidth is maintained but is moved downwardly in frequency to have reduced upper and lower frequency limit values by the application of an appropriately dimensioned portion of the sheet material thereto.

Typically the sheet material which is applied alters the dielectric value of the filter.

In one embodiment the base is a printed circuit board (PCB). Typically the filter is formed in a conventional manner such as on both surfaces and through the said PCB.

In one embodiment the sheet material is selected to have a particular dimension in order to achieve a required adaptation of operation. In one embodiment a set of portions of the sheet material is provided with the dimension of the respective portions in the set differing so as to provide a different effect on the filter when applied thereto and such that the appropriate portion in the set can be used to achieve the required adaptation of performance of the specific filter.

Typically the method includes the step of determining the extent to which the actual frequency range differs from the required frequency range and a portion of the material is selected from the set of portions which is appropriate to alter the performance of the filter to a sufficient extent to bring the same within the acceptable range of operation of the required frequency range.

In one embodiment a table is provided which indicates which of particular portion in the set of portions of material should be selected to he used in dependence upon the particular detected difference between the actual frequency range limit values and the required frequency range limit values. The provision of the table to direct the selection of the appropriate portion which is to be attached to the filter allows the standardisation of the adjustment action which. can be performed in the same uniform way by a plurality of personnel in the manufacturing process.

Tn one embodiment the method includes the steps of retesting the performance of the filter once the portion of material has been applied thereto to check whether or not the filter is then operating with a required frequency range or an acceptable frequency range if there is still a variation.

In one embodiment the sheet material used does not have any significant impact on any other operating parameters of the filter such that, for example, the return loss value of the filter is unaffected.

In one embodiment the sheet material portion, when applied, has the effect of reducing the upper and lower limits of the frequency range of the data signals which can pass through the filter.

In one embodiment the filter is provided with a plurality of arms and it is the number of the arms on which the portion of material is applied which determines the extent to which the frequency range limits are reduced so that, for example a shorter length portion of material will contact a smaller number of filter arms than a longer length portion of the material of the same width and so the shorter length portion will provide less of an adaptation in the frequency range of operation than the longer portion of material, when applied to the filter.

In one embodiment the sheet material has a constant dielectric value.

Typically the portion of material has the effect of increasing the length of the arms or tracks of the filter and the extent to which this is increased is determined by the dimension of the portion which is selected to be applied to the filter.

In one embodiment the sheet material used is a polyimide film.

In one embodiment the sheet material is provided with an adhesive on at least one surface in order to allow the same to be applied to the filter/PCB surface and be retained in position.

In one embodiment the sheet material has a thickness in the range of 30-60 microns and has a substantially constant dielectric value.

In one embodiment the sheet material used is poly (4,4'-oxydiphenylene-pyromellitimide) and which is commonly sold under the Registered Trade Mark Kapton.

In a further aspect of the invention there is provided an LNB incorporating at least one filter formed in accordance with the method as herein described.

In a yet further aspect of the present invention there is provided a method of manufacturing a Low Noise Block LNB wherein said method includes the steps of providing at least one filter for data signals received by the LNB, said filter provided intermediate the inputs and outputs of the LNB, and said method includes the step of testing the performance of the filter to identify its actual image rejection value, comparing the actual value to a required value and if the comparison is unacceptable, adapting the filter by selecting and applying a portion of polyimide sheet material of known dimensions to the filter, testing the performance of the filter again to ensure that the new actual value is acceptable with respect to the said required value.

In a further aspect of the invention there is provided apparatus for receiving digital data and providing the same at a plurality of outlets within a predefined frequency range for selective retrieval and onward processing, said predefined frequency range at least partially controlled by at least one filter formed on a printed circuit board provided within or connected to an LNB and wherein the operating frequency range of the said filter is adapted, if required, to meet or be within an acceptable amount of difference from a required frequency range of by the selective application of a portion of sheet material thereto.

Specific embodiments of the invention are now described with reference to the accompanying drawings; wherein Figure 1 illustrates an antenna assembly in one embodiment; Figure 2 illustrates a filter of the type with which the current invention can be applied; Figures 3a-e illustrate the filter of Figure 2 adapted in accordance with the invention in one embodiment; and Figures 4a-c, 5a-b and 6a-c respectively illustrate graphically the effect of variations in the dimensions of the portion of the sheet material which is applied.

Referring firstly to Figure 1 there is illustrated in a schematic manner an antenna assembly 2 for the reception of data signals which are transmitted from one or more broadcast satellites. The data is received by the surface 4 of the antenna dish 6 and deflected towards the waveguide and Low Noise Block assembly 8 which is mounted at the end of an arm 10 which, in turn, is connected to a mounting bracket 12 (not shown) at the rear of the dish. The mounting bracket then allows the assembly to be mounted to a support surface such as an external wall. The data signals which are received and processed by the waveguide and LNB are transmitted within a predefined frequency range via a cable connection 12 to one or more broadcast data receivers which are located within premises. The user of each of the broadcast data receivers can select to view and/or listen to television and/or radio programmes and, upon a user selection being made, the broadcast data receiver will select the appropriate data from the range of data which is distributed from the T,NB, A constant aim is to be able to keep the components within the LNB at a minimum while, at the same time allowing the maximum performance to be obtained from the LNB and ensuring that the data signals are available all of the time within the predefined frequency range.

In the present invention the LNB is provided with a filter as part of the data processing path in order to enable all of the required data signals to he provided within a predefined frequency range which can be carried by the capacity of the distribution cable 12, whilst at the same time avoiding the need to include switching means within the LNB and, yet further, ensuring that the predefined frequency range is met for each LNB so as to avoid possible interference with other services such as mobile phone services operating in frequency ranges which are relatively close to the predefined frequency range. As already discussed, the problem addressed is how to ensure that the filter operation can be ensured to be acceptable when it is known that the characteristics of the PCB on which the filter is formed, and other possible manufacturing processes, can cause failure of the filter to operate in the required manner. This problem is further exacerbated by the fact that the LNB's are required to be manufactured in large volumes and the time and economic pressures of the manufacturing process make it impractical to use possihle conventional solutions to change the operation of the filter.

Figure 2 shows one such filter 14 which is formed in a conventional manner by the application of a conductive track 16 having a number of arms spaced along its length on a printed circuit board 18. The input 20 and output 22 of the filter are connected to further processing components which may be of a standard form and arc therefore not described in detail here.

In accordance with the invention, the filter is formed such that it will operate to allow data signals to pass therethrough which are within a range defined by predefined upper and lower frequency values so that data signals within the required frequency range will be emitted from the output 22.

The current method is provided to allow the adaptation of the filter so as to lower at least the upper frequency limit of the frequency range but typically both the upper and lower limits to thereby move the frequency range of operation down, if required, When the filter has been formed, it is tested to detect the image rejection value of the filter and thereby determine whether the filter is operating within the required frequency range. If it is, then no further action is required. However, if it isn't, then the method of adaptation in accordance with the invention can be used.

In the preferred method there are provided a series of sets of portions of sheet material such as polyamide sheet material, which have a substantially constant dielectric value. A first set may comprise at least one portion of the sheet material of a first dimension, a second set has at least one portion of the sheet material of a second dimension, a third set has at least one portion of sheet material of a third dimension, a fourth set has at least one portion of sheet material of a fourth dimension and a fifth set has at least one portion of sheet material of a fifth dimension.

Typically, also provided is a reference table which illustrates the particular portion set to be selected dependent upon the extent of deviation of the operation of the filter from the predetermined operation parameter value. Typically the greater the deviation then the greater the adaptation of the filter which is required and this will typically mean that a greater size portion of the sheet material is required to be applied to the filter.

An example of this is shown in Figures 3a-e where, in each case, the filter 14 has been found to be operating outside of the predetermined parameter. In Figure 3a, the deviation of operation is relatively small so a relatively small portion 24 of sheet material is selected from set 1 and applied, typically via adhesive, to the filter 14. In Figure 3b, the deviation of operation is in the next deviation value group and so a larger portion 24 of sheet material is selected from set two and applied to the filter 14. In Figure 3c, the deviation of operation is in the next greater deviation value group and so a larger portion 24 of sheet material is selected from set three and applied to the filter 14. In Figure 3d, the deviation of operation is in the next greater deviation value group and so a larger portion 24 of sheet material is selected from set four and applied to the filter 14.

Finally in Figure 3e, the deviation from the predetermined parameter is such that a portion of the sheet material is selected from set five and applied along the length of the filter 14.

Figures 4a illustrates graphically the effect of providing a portion 24 of a length as shown in Figure 4b to the filter. Figure dc illustrates that lmin and 2nam widths of the sheet material portion have been added to the filter. The provision of no sheet material has the highest frequency range limit values (trace 3 in Figure 4a) when the filter is operated but it will be seen that the selective application of the 1mm or 2mm portions of the sheet material to the filter (trace 1/2 for 1mm and trace 4 for the 2mm portion) allow the frequency range limit values of the filter to be lowered and that the amount of the adaptation of the frequency range reduction can be selected by the selection of the portion with appropriate dimensions. Figures 5a and b illustrate a similar effect with further sheet material portions as indicted in Figure 5b.

Figures Ga-c illustrate the manner in which, even with a relatively large portion of sheet material 24 added to the filter 14, the return loss value of the filter is not adversely affected.

It will therefore be appreciated that by adding the sheet material of the type described herein, so the filter can be adapted to alter its frequency range of operation at the manufacturing process, but without adversely affecting other operating parameters of the filter. The ability to provide the reference table and portions of predetermined sizes which can be selected to be applied based on the extent of the deviation of the operation of the filter from the required parameter, means that the adaptation process can be implemented within the manufacturing process with minimal impact on the cost and time increase of the manufacturing process and without any specific skill requirements of the personnel involved. It also means that the adaptation can be made without the need to make any other adjustments or tests of the apparatus as the adaptation has no significant impact on other operation of the apparatus.

Claims

Claims 1. A method for the adaptation of the performance of a filter for use to provide a required frequency range of received data signals for use by apparatus in relation to which the filter is in connection, said method including the steps of; testing the operation of the filter to identify the actual value of at least one parameter, comparing the actual value with a required value for the at least one parameter and wherein, if the actual value differs from the required value by more than an acceptable amount, applying at least one portion of a sheet material to the filter to change the actual value so that the difference between the actual and required values are at, or less than, said acceptable amount.
2. A method according to claim 1 wherein the said at least one parameter is indicative of the limit values for the frequency range for data signals to pass through the filter in operation and it is the frequency range which is altered by the application of the portion of sheet material.
3. A method according to claim 2 wherein the upper and lower limits of the frequency range are adjusted such that the bandwidth is maintained but is moved.
4. A method according to claim I_ wherein the sheet material which is applied alters the dielectric value of the filter.
5. A method according to any of the preceding claims wherein the test performed on the operation of the filter determines an actual value for the level of image rejection of the filter which is then compared with the required image rejection value.
6 A method according to claim 5 wherein if the difference between the values is at or below the acceptable amount then the filter is deemed acceptable and no adaptation is required.
7 A method according to claim 5 wherein if the difference between the values is greater than the acceptable amount adaptation of the filter is required by the application of a selected portion of sheet material to the filter.
8. A method according to claim 1 wherein the filter is formed on a base.
9 A method according to claim 8 wherein the filter is formed on and between opposing surfaces of a base in the form of a Printed Circuit Board (PCB).
A method according to claim 1 wherein the sheet material portion which is added is selected to have a particular dimension in order to achieve the required adaptation of the actual value of the at least one parameter of the filter.
11 A method according to claim 1 wherein a set of sheet material portions are provided, with the dimensions of the respective portions in the set differing so as to provide different adaptation effects on the filter when selected to be applied thereto.
12 A method according to claim 11 wherein a particular portion from the set of portions is selected to be used once it is known what the difference value is and the extent of the adaptation of the filter operation which is required to be achieved by the attachment of the said sheet material portion is.
13 A method according to claim 11 wherein a reference table is provided which indicates which of the particular portions of material should be used in dependence upon the particular detected difference in the actual and required values.
14 A method according to any of the preceding claims wherein the method includes the step of retesting the performance of the filter once the portion of material has been applied thereto.
A method according to claim 1 wherein the application of a sheet material portion does not impact to any significant extent on any other parameter of operation of the filter.
16 A method according to claim 1 wherein the filter is provided with a plurality of arms and it is the number of the arms on or over which the said portion of sheet material is applied which determines the extent to which the operation of the parameter value of the filter is adjusted.
17 A method according to claim 16 wherein the sheet material is applied has increases the effective length of the arms or tracks of the filter and the extent of increase is determined by the dimension of the portion which is selected to be applied to the filter.
18 A method according to any of the preceding claims wherein the sheet material portions are formed of a polyimide film.
19 A method according to claim 18 wherein the sheet material has a thickness in the range of 30-60 microns.
A method according to any of the preceding claims wherein the sheet material from which the portions are formed has a substantially constant dielectric value.
21. A method of manufacturing a Low Noise Block LNB wherein said method includes the steps of providing at least one filter for data signals received by the LNB, said filter provided intermediate the inputs and outputs of the LNB, and said method includes the step of testing the performance of the filter to identify its actual image rejection value, comparing the actual value to a required value and if the comparison is unacceptable, adapting the filter by selecting and applying a portion of polyimide sheet material of known dimensions to the filter, testing the performance of die filter again to ensure that the new actual value is acceptable with respect to the said required value.
22. A Low Noise Block (LNB) incorporating at least one filter formed, tested and, if required, adapted in accordance with the method of claim 21.
23. Apparatus for receiving digital data and providing the same at a plurality of outlets within a predefined frequency range for selective retrieval and onward processing, said predefined frequency range at least partially controlled by at least one filter formed on a printed circuit board provided within or connected to an LNB and wherein the operating frequency range of the said filter is adapted, if required, to meet or be within an acceptable amount of difference from a required frequency range of by the selective application of a portion of sheet material thereto.

24 Apparatus according to claim 23 wherein the portion of sheet material is a substantially dielectrically constant material.