A regenerative frequency divider with a differential transimpedance amplifier (TIA) active load using 0.35 mm SiGe HBT technology is demonstrated. The differential TIA is beneficial for higher frequency and lower sensitivity operation, and the inductive peaking enhances the bandwidth of the output buffer. From the experimental results, the operating frequency ranges from 5 to 27 GHz (f max =f min ¼ 5.2) for a supply voltage of 5 V and core power consumption of 49.5 mW. The chip size is 0.86 Â 0.822 mm.

A frequency divider with super-dynamic D-type flip-flop is demonstrated in 2 mm GaInP=GaAs HBT (f T ¼ 40 GHz) technology. By biasing the HBT devices around the peak transit-time frequency (f T), the operating frequency of a D-FF with ECNFP (emitter-coupled negative feedback pairs) can be improved. At a supply voltage of 5 V, a divide-by-two function of 9.5 GHz is achieved.

determined by the 3-dB AR, is about 540 MHz or 20.8% (2.33-2.87 GHz) and 480 MHz or 19.6% (2.21-2.69 GHz) with minimum AR of 0.87 dB at 2.6 GHz and 0.88 dB at 2.45 GHz, respectively, for L t ϭ 0 and L t ϭ 19 mm. Both of the CP bandwidths are larger than 19%. It is evident that the length of the protruded metallic strips has larger effect on the port isolation level, but has less effect on the CP bandwidth. As for the antenna with L t ϭ 19 mm, both impedance matching (referred to 10 dB return loss) and low coupling level (referred to 20 dB isolation) are achieved within the CP operating band. Figure 4 shows the measured far-field radiation patterns of the antenna with length of L t ϭ 19 mm at 2.45 GHz in the LHCP and RHCP operation. It is observed that the cross-polarization levels are about 26 dB in the broadside direction in both states. The maximum radiation direction of the antenna displaces a little from the z-axis. It should be noted that the backside radiation pattern is a mirror image of the front pattern, and the polarization senses of both sides are opposite to each other. The antenna radiates almost the same amount of energy into both sides. CONCLUSIONA novel design of broadband dual CP square slot antenna has been investigated and successfully implemented. Two orthogonal modes of the proposed antenna are excited in series through the coupling between the T-junction and the T-shaped strip. By loading the four metallic strips at the slot corners, high port isolation level is achieved. The measured 3-dB AR bandwidth is 480 MHz or 19.6% and the isolation between two ports is better than 20 dB over the band. The proposed antenna has excellent dual CP characteristics and is suitable for polarization diversity operation.

downward and eventually approaches Ϫ/Ϫ180°. Within the region between 2 /90°and Ϫ 2 /Ϫ90°, plane waves are reflected in-phase, rather than out-of-phase. Next, we removed the FSS-layer to examine its influence on the antenna-system. Although this shifted the resonance frequency, it was still within the desired range (860Ϫ960 MHz), and the input impedance also remained within the acceptable range (Fig. 23); consequently, it should be possible to shrink the size of the antenna by a factor of 1.05. We note from Figure 24 that the directivity shows some minor (around 1.2) differences in the range between 900 and 950 MHz.By comparing the input impedance ( Fig. 25) of the antenna composite, we observe that there is a resonance type of behavior that may be attributed to the FSS-layer, which has its own resonance in this range. The inclusion of the FSS-layer yields a higher level of delivered power (ϳ94%) but the bandwidth is slightly smaller in this case as may be seen from Figure 25. This could be attributed to the relatively narrow frequency range in which we have the AMC behavior.In addition, we found that, in general, while using an AMC shift, the input impedance characteristics shift toward a lower frequency; hence, we can decrease the size of the antenna, though only slightly (5-10%). However, designing the antenna/FSS composite for maximum delivered power is quite difficult because its input impedance as well as the ratio between the real and imaginary parts of this impedance is very sensitive to any change in the antenna length.This leads us to conclude that the gain improvement we realized to the RFID system by using an AMC-structure is at best marginal, and more research is needed to fully analyze the complex behavior of the metamaterials for RFID applications. , The design synthesis of multiband artificial magnetic conductors using high impedance frequency selective surfaces, IEEE Trans Antenna Propagat 53 (2005), pp. 8 -17. ABSTRACT: This paper demonstrates a 4-GHz monolithic SiGe heterojunction bipolar transistor quadrature voltage-controlled oscillator (QVCO) using superharmonic coupling topology. The QVCO at 4.17 GHz has phase noise of Ϫ116 dBc/Hz at 1 MHz offset frequency, output power of Ϫ6 dBm, and the figure of merit Ϫ179 dBc/Hz. The core current consumption is 3.2 mA at 3 V supply voltage. The die size is about 1.4 mm ϫ 1.2 mm.

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