I I I I 1 --Lc.GO 1L,9,', -40.00 '11.30 11.90' FREO-CHZ Figure 8 Experimental fixed central frcqucncy results of the active ring resonator filter and measurements is due to the inaccuracy of the electrical model of parasitic connections. However, the filter has a 35-MHz, very narrow bandwidth. It can be observed in Figure 8 that the monolithic circuits perform a 550-MHz central frequency tuning, centered at 1 I .8 GHz. Dimensions of the active filter are 8 X 10 mm, including the monolithic chips and all the biasing elements. The global dc consumption is less than 50 mW, because the low gain level necessary for the compensation of the passive resonator losses.
Compared to the active filter of Section II.A, the advantage of the new solution proposed is that the same monolithic control circuit allows loss compensation and central frequency tuning without mismatching effects. See Figure 9.
CONCLUSION
Active filters are associated at low frequencies with classical operational amplifier circuits. Because of the unavailability of such components in the microwave domain, many solutions have been proposed in the literature to realizc this function. In this article two realizations are presentcd. The first one, resulting from the most classical principle application, shows how the monolithic technology allows a significant reduction in the size of the devices. In comparison, the second one demonstrates that the application of a new and simple concept, with the same monolithic circuit, can lead to both loss compensation and broadband frequency tuning.