| In recent years, with the rapid development of microwave device and technology, the requirement of performance on microwave mixer in modern radar and communication became higher and higher. To reduce noise figure and improve receiver sensitivity, the heterodyne receiver model have become more widely available in the communication system. The rejection to image frequency interference has become the last problem for a low-noise receiver. However, in radio communication, because of the lower signal frequency, the dimension of microwave IRM (Image Rejection Mixer) which is made of microstrip line is just too large to integrate. In order to reduce the dimension of the receiver, the study on the miniaturization for microwave IRM is necessary.First, this paper gives a brief introduction and research to the balun which is usually used in microwave mixer. Besides, two miniaturized frequency-tuned microstrip balun are proposed. Single-layer and double-layer miniaturized frequency-tuned microstrip balun can operate at 730MHz-1160MHz and 620MHz-1020MHz, respectively. The two realized baluns have a dimension of 18.5mm×15.5mm and 19.6mm×16.8mm, respectively. The Miniaturized balun is cost-saving and easy to integrate with circuits. Tunability makes the balun can operate at different frequency bands, which increase the flexibility and improve the performance.Then, the working principle of microwave mixer is introduced. Besides, the microwave IRM is analysed systematically. Further more, a single-balanced mixer, RF Power divider in phase, LO quadrature coupler and IF quadrature coupler are designed in this paper. On this basis, a microwave IRM has been processed successfully. The realized mixer has a dimension of 30.7 mm×40.1 mm. The IRM area has been reduced by 77 percent compared to that without miniaturization. For the input RF signal operating between 2.85GHz and 2.95GHz, the conversion loss is less then 7dB and image frequency rejection ratio is greater than 20dB. Then, the test results and simulation results of IRM are compared and analyzed, and good agreement was obtained, which has proven that this method is feasible and valid.At the end of this paper, manufacturing process and test systems of passive device have been provided. Besides, the test methods of mixer and frequency-tuned balun have been introduced in details. |
