[Show abstract][Hide abstract]ABSTRACT: Compact 3-dB 90° and 180° couplers with harmonic suppression using lumped-element bandstop resonators are proposed. The bandstop resonators are not only used to provide the high-pass and low-pass characteristics of conventional couplers, but also have a significant harmonic band rejection at the same time. Therefore, the required lumped-element inductors with a low quality factor are reduced as much as possible, enabling significant circuit size reduction. Further, minimum bulky via holes are employed in these topologies, thus carrying them out on the monolithic microwave integrated circuit is beneficial. Detailed design and theoretical analysis are presented for the proposed couplers with harmonic rejection. To validate the design concept, two proposed couplers implemented on an FR-4 printed circuit board at 2.45 GHz are demonstrated. Promising agreements between the simulation and measurement can be observed. Experimental results reveal that the 90° and 180° couplers suppressed the second harmonic below 26 and 30 dB, respectively, within the 0.6-dB amplitude imbalance and 2° phase error at the center frequency.
Article · Dec 2010 · IEEE Transactions on Microwave Theory and Techniques
[Show abstract][Hide abstract]ABSTRACT: A low-power PMOS Colpitts voltage controlled oscillator (VCO) topology using the technique of gate inductive feedback is demonstrated. The topology enhances the negative conductance and overcomes the start-up difficulty of the conventional Colpitts VCO. This enables the Colpitts VCO to be operated in low-power consumption. The fabricated VCO operates from 7.4 to 7.9 GHz with 7% tuning range, a power consumption of 4.9 mW, and a supply voltage of 1.5 V. The measured phase noise at 1 MHz offset is 108.3 dBc/Hz at 7.9 GHz.
Article · May 2010 · IEEE Microwave and Wireless Components Letters
[Show abstract][Hide abstract]ABSTRACT: A low phase noise differential Colpitts voltage-controlled oscillator (VCO) with the bottom series PMOS cross-coupled current source is presented. The core Colpitts VCO adopts a pair of PMOS as the biased current source at the bottom, instead of a conventional NMOS topology, to achieve a better phase noise performance as the PMOS has lower flicker and white noise than those of NMOS and the output power spectral density of PMOS operated in bottom-biased type is further less than that in top-biased one in the same power consumption. The fabricated VCO operates from 4.9 to 5.46 GHz with 10.6% tuning range when the power consumption is below 6.4 mW with a supply voltage of 1.8 V. The measured phase noise at 100 kHz offset is -100.3 dBc/Hz at 5.46 GHz and achieves a good FOM performance of -187 dBc/Hz.
[Show abstract][Hide abstract]ABSTRACT: A novel configuration of a subharmonic mixer utilizing third local oscillation (LO) harmonic is presented. The mixer is capable of down-converting a Ka-Band radio frequency (RF) signal with the third harmonic of an X-band LO signal to produce a 2 GHz intermediate frequency signal. It is fabricated on a 4 mil substrate using a 0.15 mum GaAs PHEMT process. A novel quadrature hybrid is realized by using compact lumped elements, and it is beneficial for the reduction of chip size for an LO at a relatively low frequency in this topology. This is because it does not need any bulky via holes. Compared with published subharmonic mixers, it provides a more flexible requirement for an LO source at a relatively low frequency for an overall communication system design. The measured results show that the best conversion loss is about 13.2 dB at a RF frequency of 29 GHz as a 10.5 dBm 9 GHz LO signal is pumped. The chip area of the mixer is less than 3.14 mm<sup>2</sup>.
[Show abstract][Hide abstract]ABSTRACT: In this letter, a novel compact quadrature hybrid using low-pass and high-pass lumped elements is proposed. This proposed topology enables significant circuit size reduction in comparison with former approaches applying microstrip branch line or Lange couplers. In addition, it provides wider bandwidth in terms of operational frequency, and provides more convenience to the monolithic microwave integrated circuit layout since it does not have any bulky via holes as compared to those with lumped elements that have been published. In addition, the simulation and measurement of the fabricated hybrid implemented using PHEMT processes are evidently good. With the operational bandwidth ranging from 25 to 30 GHz, the measured results of the return loss are better than 17.6 dB, and the insertion losses of coupled and direct ports are approximately 3.4plusmn0.7 dB, while the relative phase difference is approximately 92.3plusmn1.4<sup>deg</sup>. The core dimension of the circuit is 0.4 mm times 0.15 mm.
[Show abstract][Hide abstract]ABSTRACT: A 2.4-GHz low noise amplifier (LNA) for the direct conversion application with high power gain, low supply voltage and plusmn4 KV human body model (HBM) electrostatic discharge (ESD) protection level implemented by a 90-nm RF CMOS technology is demonstrated. At 12.9 mA of current consumption with a supply voltage of 1.0 V, the LNA delivers a power gain of 21.9 dB and the noise figure (NF) of 3.2 dB, while maintaining the input and output return losses below -11 dB and -18.3 dB, respectively. The power gain and NF are only 0.2 dB lower and 0.64 dB higher than those of LNA without ESD protection
Article · Dec 2006 · IEEE Microwave and Wireless Components Letters
[Show abstract][Hide abstract]ABSTRACT: A novel compact quadrature hybrid using low–pass and high-pass lumped elements is proposed in this paper. The topology of the quadrature couplers has two combinations of lumped elements and these proposed topologies enable both significant circuit size reduction in comparison with former approaches applying microstrip branch lines or Lange couplers. In addition, they provide a wider bandwidth in terms of operational frequency and provide more convenience to the monolithic microwave integrated circuit (MMIC) layout because they do not have any bulky via holes as compared to those with lumped elements that have been published. To verify the design concept, two proposed quadrature hybrids implemented on an FR-4 printed circuit board (PCB) at 2.4 GHz are designed and fabricated. Promising agreements between the simulation and measurement can be observed.