| ||||||||||
|
• Информация "download = договор с автором" | ||||||||||
Григо, З.:"A new Microwave Highpass Filter with the Input in Microstrip and the Output in Slotline" | ||||||||||
In this paper a new highpass filter with a rejection band up to 3GHz and a matches transmission band of 4.2 - 6GHz is described. The remarkable thing about this filter is that its input is in microstrip- and its output in slotline-technique and that the equivalent circuit elements of the transition microstrip - slotline are even filter components themselves.
The suggestion to make such a filter based on the task to develop a receiver for 4.2 - 5.0GHz with a IF-band 900-1700MHz and the oscillator frequency below the receiving band. This frequency situation is shown in Fig.2.
For receivers with such IF-band balanced mixers are preferred, where the diodes pair is located at the transition point between a slotline and coplanarline. In such mixers for the X-band the suppression of the oscillator and the image frequencies are realized as a rule by a rejection filter consisting of microstrip resonators crossing the slotline at the other side of substrate. In our case such rejection filter would not be realizable because of the required large relative bandwidth. The idea to take a highpass filter results logically from this situation. Looking at the equivalent circuit of a transition microstrip-slotline [1] you will remark that there are already two elements of a Cauer highpass filter of the degree n=4 (Fig. 1). The remaining elements are good realizable in microstrip technique: the series resonator by a open stub in two steps and the capacitor by a short open coupled line (Fig.3). The filter development was proceeded in following steps: - choice of a suitable Cauer lowpass filter prototype, - conversion of the lowpass prototype into a highpass filter with lumped elements, - optimisation of this highpass filter, - conversion the circuit with lumped elements into such with line elements, - optimisation of this circuit, - realization of a 25mil Al2O3 - substrate. The computer aided simulation was accomplished by the system К А ОS [2]. The practically reached results differ a little from the theoretical results, but they comply with the requirements of the practice. Only a little modification was needed in the first circuit at the length of shorted slotline. After this correction no further. adjustments were necessary in the following samples. Fig.2 shows the measured values in comparison with the theoretical characteristics. The large ripple of S11 in the pass-band is easily explainable by the long slotline (approx. 20mm) at the measurement object and by the effect of the transition to microstrip at second measurement connection.  Following values were reached:
The layout data were formulated in the language МILL [3 ... 5]. The pattern is shown in Fig.3. The data are written in the form of a macro, so the filter can be placed in any position within a superior layout. The МILL - data of the macro are given in Fig.3 as well. (W in the macro-interface, see element 6, "MI", is the width of the slotline.)  Postscript: You can find a supplement the Russian-language-side of this paper in the end. References:
|
