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Microwave filter with controlled bandwidth

DOI 10.18127/j00338486-201901-08


W.I. Kaganov – Dr.Sc.(Eng.), Professor, RTU MIREA (Moscow)
Fam Ky – Undergraduate, Post-graduate Student, RTU MIREA (Moscow)

The structure of the microwave bandpass filter on microstrip lines, to which varicaps are attached, is discussed. A computer program allows you to calculate the attenuation characteristics of such a filter. With the example of a filter with a center frequency of 6 GHz, it is shown that by changing the capacitance of the varicaps, it is possible, within certain limits, to vary the bandwidth, which will allow operative control of the parameters of the radio engineering system under varying operating conditions, for example, an increased level of intentional interference.
In multi-channel telecommunication systems, multiple access to a radio channel due to changing operating conditions, it is necessary to quickly change the parameters of devices serving the system. This also applies to the microwave channel of the radio receiving device, whose bandwidth it is desirable to change, depending on the load of a communication channel and interference situatio.
The microwave channel of the radio receiving device, whose bandwidth is desirable to change, depending on the load of a communi-cation channel and interference situation.
In the framework of this general problem, we consider a method for quickly controlling the bandwidth of a microwave filter on the associated microstrip lines by connecting to the open inputs of varicaps.
The attenuation characteristic of such a filter can be calculated from a computer program, passing successively from one link to another, using the reflection coefficient at the input of each link as a recurrence formula for the calculation.
By this computer program, a 4-unit bandpass filter with a frequency of 6 GHz was calculated. The attenuation characteristics of the bandpass filter were constructed for different values of the varicap capacitance, the voltage at which varies rapidly depending on the required bandwidth.

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