In order to further suppress the 2 nd and 3 rd harmonics simultaneously, the two types of rectangular loops as EBG structures are combined alternatively on the middle layer. The simulated performances of the parallel-coupled BPF without and with two types of EBG structure are shown in Figure 4. It is interesting to note that the simulated performances of the parallel-coupled BPF with two types of rectangular loops on the middle layer has spurious suppression at Ϫ32 and Ϫ42 dB for the 2 nd and 3 rd harmonics, respectively, as clearly shown in Figure 4. The designed filter is then fabricated on two FR4 GD substrates with relative permittivity r ϭ 4.4, loss tangent ␦ ϭ 0.02, and 0.8-mm thickness. The performances of the proposed BPF are characterized using an Agilent 8753E network analyzer. For practical measurements, the 2 nd and 3 rd harmonics are all below the level of Ϫ30 dB; in particular, the 3 rd harmonic is suppressed below Ϫ60 dB, which is extremely beneficial for the output of the active devices. In addition, the parallel-coupled BPF with EBG structure has a central frequency of 2.02 GHz and insertion loss S 21 ϭ Ϫ2.79 dB. The low insertion loss verifies that the conductor loss does not increase, as the EBG cells are constructed in the middle plane. The slight difference of the measured center frequency may result from the two FR4 boards not being pressed together closely, thus causing the to permeate the two FR4 boards; hence, the effective dielectric constant drops and the center frequency rises. According to the above results, the spurious characteristic of the parallel-coupled BPF with our designed EBG structure is superior to that without the EBG structure. In particular, it is noted the designed EBG structure may be cause the error of shifting the center frequency in the measured results. For example,in [3], the center frequency of the filter added to the PBG structure shifted to a lower frequency of about 15%, corresponding to the original designed center frequency of the filter without the EBG structure. However, the center frequency of our filter with EBG loops added shifted 1% higher, corresponding to the originally designed center frequency. It was found that our EBG periodic cells on the middle layer that depart from the microstrip have no significant effect on the original frequency response, as compared to the results in [3]. CONCLUSIONA novel microstrip parallel-coupled BPF using two types of rectangular EBG loops has been proposed. Two types of rectangular EBG loops on the middle layer have been designed to avoid the package problem and to achieve multiple suppressions. We have shown that this proposed PBG BPF has the superior characteristic of Ϫ30-dB spurious suppression for the same dimensions as those of conventional parallel-coupled BPFs. The EBG periodic cells on the middle layer that depart from the microstrip line have no significant effect on the original passband response and insertion loss.

Absrrrrcf -This paper firstly presents a broad band uniplanar balanced mixer using coplanar waveguide-slotline hybrid-ring. .Experimental results show that the best conversion loss is less than 5.5dB. The isolation between RF and LO ports is about -20dB from 4.0GHz to 5.2GHz.The voltage standing wave ratio (VSWR) of port RF is less than 2.0 from 3.SGHz to jSGHz, and the VSWR of IF port is less than 2.0 with IF below 55OMHz.