Recent advances in microwave active filter design. Part 2: Tunable structures and frequency control techniques

Abstract

This two-part paper presents a representative sample of recent advances in microwave active filter design. In the second part, we discuss design techniques for tunable structures and frequency control. First, we present switchable and continuously-tunable bandstop filters employing MMIC negative resistances to compensate for losses. Next, we detail several approaches to the design of tunable high-order "recursive-like" filters. Layouts and measurements are given for different MMIC implementations, with simulated results presented in other instances. Finally, we discuss new technologies and processes for future low-cost, low-noise microwave MMIC active functions. The article concludes with the description of a development, including experimental results, of frequency-control techniques based on locked-loop architectures.

Analysis of negative‐resistance characteristics in active capacitance circuit

“…While there have been several attempts to overcome this problem, including active resonator [1][2][3][4][5][6] and RF MEMS [7][8][9][10][11], more progress is still required for actualizing commercial products. Many authors have reported numerous circuits that embody a negative-resistance circuit, however, most of them have drawbacks with regard to the equivalent resistance and reactance values at the center frequency.…”

Ferroelectric-based agile devices—Application to tunable filters

“…Over the last decades, several solutions have been investigated to get agility. One of them was the use of lumped elements such as FET transistor, PIN diode, and varactor diode [1]. These devices are interesting for bias voltage and commutation time.…”