Tools supporting design in Telkom-Telmor
It's a long way from idea to implementation, but..
We use tools to support the design of RF electronic devices.
Before an RF electronic device (in particular an SMATV device such as an antenna, amplifier or filter) is put into serial production, it usually goes a long way.
The following stages can be distinguished in the classic approach to design a new device:
- market research and definition of technical requirements;
- development and design of the model;
- model measurements, corrections;
- developing and making a prototype;
- prototype measurements, corrections;
- repeating the stage, if necessary, until the desired acceptable parameters are achieved.
In an effort to reduce the number of design stages, more or less sophisticated tools to support the design of RF devices (simulators) can be helpful.
Through their use, the time required to achieve the final product can be significantly minimised by reducing the repetition of certain design stages. Simulations with the use of software, leading to the right result, replace iterations involving the execution and measurement of successive physical models. In this way, the process of creating a new device can be minimised to include the following steps:
- market research and definition of technical requirements;
- development of a preliminary model design using CAD software;
- carrying out a sequence of simulations until the desired effect is achieved;
- designing the model;
- model measurements, corrections.
Nowadays, a number of advanced tools (programs - simulators and measuring equipment) are available to facilitate either the direct design of the devices themselves or the control of the electrical parameters obtained by measuring prototype models. The ability to use them can significantly minimise the time and cost of implementation and thus influence the lower price of these devices.
The use of modern tools and techniques to design RF equipment allows for faster optimisation and achievement of the required parameters, and thus an earlier market launch. Many of these are used by Telkom-Telmor, and some of the more interesting and advanced ones are:
- 3D EM field simulators (e.g. Ansys HFSS);
- RF circuit simulators (e.g. Nuhertz FilterSolutions filter synthesiser);
- 3D printers;
- Advanced measuring equipment.
In the process of developing a new product with the use of modern design tools, the various stages of designing, e.g. a TV antenna (with preamplifier) would look like this:
- market research and definition of technical requirements;
- development of a preliminary model design using CAD software (electronic and mechanical areas);
- carrying out a sequence of simulations until the desired effect is achieved (Nuhertz, HFSS ANSYS);
- model construction using 3D modelling (3D printer), tooling department, electronics prototype department;
- model measurements, corrections (using vector analysers, noise meter, digital parameters meter, RF generators);
- environmental measurements (including wind tunnel and climate chamber);
- SURGE tests, EM tests.
Below, we will focus on a general overview of the above-mentioned RF device design support programs.
The Nuhertz FilterSolutions filter design software is one of the simpler, yet extremely helpful tools used at the very beginning of the design of an RF device to quickly synthesise a filter with given parameters.
Among the many options available, the program allows the user to select the appropriate type of filter (Bessel, Butteworth, Chebyshev, Eliptic), its type (low-pass, high-pass, band-pass, band-stop) and its method of implementation (inter alia lumped constants [Lumped LC], distributed constants [Transmission Line], Active).
Below is an example of a band-pass filter with Hairpin-type distributed constants realised using coupled microstrip lines.
Nuhertz, in combination with more advanced simulators that also allow optimisation of e.g. the distribution parameters S21, S11, (e.g. ADS or Ansys HFSS), makes it possible to design the required filter quite precisely and quickly.
An interesting and useful feature of Nuhertz is the ability to automatically export a filter realised using elements with distributed constants to Ansys HFSS software. This 3D EM field simulator enables filter optimisation to be carried out to achieve the required parameters in a given frequency range, such as S11 mismatch attenuation or S21 attenuation. The results of the obtained calculations of such a filter are very close to the actual measurements.
Below, a Hairpin FPP filter modelled (imported from Nuhertz) in Ansys HFSS simulator.
Due to the need to filter out unwanted signals in RF equipment (especially SMATV equipment), many different types of filters are used. Their optimisation to achieve the desired parameters is often very labour-intensive.
The (example) RF circuit design tools presented above minimise the time and cost required to achieve the required device parameters, eliminating the need to make further models to achieve them.
The above example of the use of Ansys 3D HFSS simulator, is just one of its many computational capabilities used by the designers from Telkom-Telmor’s development office.
One of the most complex design processes for which the HFSS Ansys three-dimensional EM field simulator is used at Telkom-Telmor is the TV antenna design process.
The programme enables the creation of a 3D model of the antenna and its operation to be simulated, taking into account the properties of the materials from which it is made, the mounting elements or the elements that integrate the entire structure. At the same time, the antenna model can be supplemented with electronic components such as a symmetrizer or preamplifier, making the calculations more precise and closer to reality.
Below is an example of an antenna modelled in Ansys HFSS, along with its gain characteristics in 3D space.
The simulation makes it possible to accurately determine the antenna's gain, radiation direction, power of the main and side lobes, or many other parameters important to the antenna designer.
Depending on our needs, the simulation results in the antenna’s radiation characteristics (so-called antenna gain) in 3D space, or the matching at its output (S11), so that we can assess its performance in the projected operating band.
The use of the Ansys HFSS program in the antenna design process allows, to a much greater extent than Nuhertz, the minimisation of the number of physical models needed to obtain specific parameters, which has its tangible benefits:
- time saving (execution of mechanical components, electronics);
- costs minimisation (materials are saved);
- reduced number of detailed measurements and tests.
The antenna design process is an excellent example where another innovative tool can be applied, which is being increasingly used in prototype manufacturing (and beyond). We are talking about 3D modelling and specifically about 3D printers.
This solution makes it possible to quickly and relatively inexpensively manufacture, for example, housings for electronic devices or plastic components, e.g. for integrating active antenna elements, on the basis of documentation prepared in CAD programs (digital source files, usually in SCL format).
The use of 3D printers makes it possible, among other things, to test different variants of a manufactured component and then, once satisfactory results have been obtained, to make the necessary adjustments to the design, even before making expensive moulds for plastic castings or ZnAl alloys (zinc-aluminium alloys). This saves the time needed to make the models and minimises the costs associated with preparation of production of the designed antenna.
A number of detailed tests and measurements of the physical models are required before the design work is completed and the final parameters of the RF equipment are accepted, which should be in accordance with the requirements set at the outset of the project. Most of these are carried out by the Telkom-Telmor designers in in-house laboratories.
However, in the case of TV antennas, there is a need for some tests to be carried out at certified bodies with suitable facilities for specific tests. One such test is environmental testing (related to safety of use), which involves testing the mechanical resistance of the antenna to wind gusts. This type of testing is carried out by the Institute of Aviation in Warsaw in a special wind tunnel. New antennas designed at Telkom-Telmor are also subjected to such tests.
Below is a test of the antenna in the wind tunnel at the Łukasiewicz – Institute of Aviation in Warsaw.
Summary:
The examples presented above show that now there are many modern tools to optimise the development process of new electronic devices by reducing the time and cost of prototyping. The tools presented in the article are just one of many that can be used. At the same time, it should be noted that in order to remain competitive in the RF equipment industry (including SMATV), it is necessary to follow new technologies by investing in modern solutions, through the implementation of both design support software and measuring equipment, which Telkom-Telmor is apparently doing.
Author: Andrzej Osiecki – Constructor of Electronics W.Cz. - Research and development department