The microwave frequency band is extensively used for many applications such as GPS navigation, mobile phone communication, satellite television broadcasting or weather radars.
The microwave mixer is a crucial component of every transmitter and receiver unit. In a transmitter the mixer is used to modulate a carrier signal and in a receiver it downconverts the received signal to an intermediate frequency for which filter and amplifier design is more preferable.
The aim of this B.Sc. thesis is to design a transistor mixer and the required filter circuits, realize them on a microstrip structure, carry out measurements and evaluate the results.
In my thesis, first I review the phenomenon of mixing and summarize the microwave mixing methods. Besides listing the properties of mixers I present the theoretical knowledge needed for design. The design was aided by the AWR Microwave Office software. I explain the steps of the circuit design and then evaluate the results of the measurements performed on the mixer.
I chose a topology which may be used both as an upconverter and a downconverter. I measured the conversion loss, the upper limit of the dynamic range and the isolations between ports. Besides the frequency conversion of carrier signals I also examined the transmission of modulated signals (QPSK, 16-QAM).