Band-stop filters (BSFs) are one of the indispensable components for radio frequency and microwave circuits` applications. They are widely used in RF wireless communication systems for their effective suppression of spurious signals and unwanted wideband noises, to allow desired signals to pass through. Recently, BSFs have recently become an attractive research field for scientists since they can be used in both receivers and transmitters and has been integrated into nonlinear circuits such as mixer, oscillator, and amplifier to enhance their performances.
The RF device studied in this analysis is made of microstrip line (MSL) band-stop filter (BSF) by using a quarter-wavelength open circuited stub. Figure 1 shows the working prototype of the proposed implementation for the first order narrow-band BSF with an open metal housing.
In order to predict its maximum achieved temperature for a given input power under a well-defined environmental condition, an S-parameters study with thermal coupling of HFWorks tool, was used.
The working prototype was realized by a standard printed board fabrication technique. The circuit is consisting of a uniform width strip-line of a 50 impedance with a quarter-wave central open-circuit stub. It is implemented on a Megtron 6 substrate (from Panasonic) and an open metal housing made of Aluminum, like shown in the figure 2. The geometrical dimensions are detailed in table 1.
Geometrical parameter | Dimension (mm) |
30 | |
25 | |
20 | |
0.93 | |
2 | |
4.3 | |
0.15 | |
5.93 |
The S-parameters solver of HFWorks is used coupled to the thermal case for a working frequency range of [4GHz-16GHz]. The properties of the used materials are summarized in table 2.
Material | Relative permittivity | Dielectric loss tangent | Electrical conductivity (S/m) | Thermal conductivity (W/m.K) |
Megtron 6 | 3.6 | 0.006 | 0 | 0.4 |
Aluminum | 1 | 0 | 3.5 E+7 | 237 |
Copper | 1 | 0 | 5.96E+7 | 401 |
A fast sweep S-parameters study for the frequency range of [4GHz-16GHz] revealed the next results for a resonant frequency of 10GHz:
The next figures are showing the 2D plot of the S-parameters results: S11 and S21 (Return and insertion losses) for HFWorks tool and the experimental measurement, versus frequency. The deepest rejection is about 25dB at the mid-band frequency of 10GHz. The obtained 10dB Stopband bandwidth =5.1%: [9.8 GHz-10.41GHz].
After solving the main electromagnetic study, HFWorks feeds the thermal loads (conductor and dielectric losses) to the thermal solver. Under a power excitation of 2W applied to the input port, the simulation revealed the next temperature distribution results across the BSF by taking into consideration the applied thermal boundary conditions. The temperature achieves a maximum value of 47°C which is in a good coincident with the experimental measurement according to the Reference [1].