to the chip input. The output constellation for this configuration is shown in Figure 4(b). Only a slight degradation of the constellation compared to the electrical back-to-back measurement cab be observed.
CONCLUSIONSWe have shown the feasibility of a 40 Gb/s IM/DD communication system using 10G optical components based on a BEM scheme of the SCM type and the use of DSP. Increased circuit complexity is of reasonable proportion and processing is implemented in lowcost CMOS IC technology. We demonstrated the transmission of a single microwave channel through 30 km of SMF using a test chip that by itself constitutes the highest-speed integrated CMOS QAM transceiver to our knowledge. Potential applications for the current system span different types of short reach low-cost interconnects (such as backplane, box-to-box and storage area networks). The integrated electrical transceiver can potentially be connected to other optical channels for low-cost metro applications. . Typically, the planar dual-band BPFs consisted of two circuits are individually designed for each one band [3]. However, these approaches need extra impedance matching networks for a diplexer-like structure, causing the large circuit size. Another way for designing dual-band BPF is developed by using a cascade of open-stub structures to achieve a dual-band performance [4]. Therefore, design of a compact and low loss BPF is a real challenge to the circuit designers nowadays. Among the popular resonator structures, stepped impedance resonator (SIR) is usually used. It was originally presented that the SIR can not only reduce the circuit size but also control the harmonics by properly tuning its impedance ratio (K) [5][6][7][8]. For instance, a dual-band BPF by using one-wavelength SIR with dual-mode structure was reported [6]. However, the second passband frequency was only dominated by the impedance ratio of the SIR. A slightly high insertion loss of two passbands and low passband selectivity were introduced because of the large discontinues appeared in SIR with very high K.In this letter, we propose a new compact dual-band BPF using trisection SIRs, which introduced two passbands located at 2.4/5.2 GHz through a single filter topology. The theory and guidelines for selecting the geometric parameters of SIRs are clearly presented in next section. Finally, the compact dual-band BPF is optimally designed, fabricated and characterized. K cot 2 ϭ tan 1 (odd-mode)(1)It is noted that the impedance ratio (K) and length of SIRs are varied to adjust the fundamental and the second resonances over a wide frequency range to obtain more design freedom. Thus, the 2 is proportional to the electrical length of SIR in this study, and the length ratio ␣ of the SIR is defined asSubstituting (3) into (1) and (2) can find:To appropriately design the dual-band frequency response, the relationship of resonant length t and length ratio ␣ for a SIR with K ϭ 0.5, 1, and 2 is shown in Figure 2. It is found the nth resonant mode occurs as functions of the impedance ratio (K) an...