Optimization Approaches for Digital Controlled Tunable Filters for Receivers
(Room 204)
18 Oct 18
4:00 PM
-
4:30 PM
Reconfigurable/tunable microwave filters have lots of potential for use in RF receivers in wireless, 5G, radar and satellite communications. Tunable filters are used in pre-selection and IF bandpass filter parts to eliminated unwanted signals in receivers. In this paper, we cover the significance and comparison of these different tunable filters. They ensure greater functionality, better channel selectivity, reduced size, and lower weight for RF receivers. In addition, while they eliminate unwanted signals, LNA linearity is better and power consumption of ADC is reduced in receivers. According to application areas, there is a preference for different solutions, such as RFMEMS, semiconductor diodes, ferroelectric materials, and YIG filters. Q factor is a highly important parameter in the selection among these technologies. In this paper, two different tunable filters are designed and implemented in UHF and S band with varactor diodes and BST ferrolectric capacitors. Theoretical analysis, circuit simulations and momentum analysis are evaluated in ADS. Designing narrowband filters was the main motivation in this work. Center frequencies of filters vary from 468 MHz to 780 MHz with approximately 90 MHz, also 2412 MHz and 2765 with 140 MHz. Finally, we emphasize closed loop filter approach and optimization techniques. In traditional tunable filters, after the filter has tuned the desired position, it is difficult to observe measurement results. So, tuning errors, including hysteresis, non-linearity, frequency drift over temperature, and aging of the components, cannot be compensated. In order to correct these errors, different closed loop systems are used. Some of the more recent and well-known sequential tuning techniques are the optimization tuning technique , look-up table and the time domain tuning technique. For this work, a look-up table is generated and used with 0.1V driving voltage resolution and it is controlled by the microprocessor.