A Current-reused VCO with Degenerated RC Components

Wang, Ruey-Lue; Liu, Chien-Hsuan; Tsai, Guo-Ruey; Lin, Yuping; Lin, Zhicheng; Su, Yan–Kuin

doi:10.1109/edssc.2007.4450163

Cited by 1 publication

(5 citation statements)

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“…Recently, a VCO using a couple of NMOS and PMOS transistors in the cross-connected pair as a negative conductance generator has been presented [1,2]. The series stack of N-and P-MOSFETs allows supply current to be reduced by half that of the conventional LCVCO.…”

Section: Introductionmentioning

confidence: 99%

“…That means that the proper choice of device parameters will result in the symmetrical behavior of charge and discharge at the two output terminals, and then differential output signals. Degeneration resistances and degeneration capacitors are added to enhance the symmetry of the differential output signals [1,2,3]. Hence, it is an important issue that source-degenerated components r1, r2 must be optimized to enhance the symmetry of output waveforms.…”

Section: Introductionmentioning

confidence: 99%

“…The FOM of the designed VCO is -185.55 at the 2.359 GHz. Table II lists the comparisons of measured performances with those of other references [1,2,4,6]. The proposed topology offers the probable solutions of low power, small size (i.e.…”

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confidence: 98%

“…Among the building blocks of any transceiver, a voltage controlled oscillator (VCO) is an important building block. A great deal of research has focused on the LC-tank VCO's consisting of passive inductors, transformers, and varactors, which are available with advancement of CMOS technology.Recently, a VCO using a couple of NMOS and PMOS transistors in the cross-connected pair as a negative conductance generator has been presented [1,2]. The series stack of N-and P-MOSFETs allows supply current to be reduced by half that of the conventional LCVCO.…”

mentioning

confidence: 99%

“…In this paper, we present a modified topology to reduce influence degree of the device parameters on the circuit performances. In addition, the larger VCO gain (KVCO) brings about the worse phase noise [2]. Hence, the topology of switching capacitor is used to enhance the characteristics of phase noise by dividing the wanted frequency band into four sections.…”

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confidence: 99%

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A switched-capacitor current-reused VCO with symmetrical differential outputs

Wang

Lin

Tzeng

et al. 2008

2008 Asia-Pacific Microwave Conference

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IntroductionPortable devices are required to operate for extended periods of time without need to charge or change exhausted batteries. This means the importance of low-power circuits on portable systems. Among the building blocks of any transceiver, a voltage controlled oscillator (VCO) is an important building block. A great deal of research has focused on the LC-tank VCO's consisting of passive inductors, transformers, and varactors, which are available with advancement of CMOS technology.Recently, a VCO using a couple of NMOS and PMOS transistors in the cross-connected pair as a negative conductance generator has been presented [1,2]. The series stack of N-and P-MOSFETs allows supply current to be reduced by half that of the conventional LCVCO. This topology is prone to have differential output signals which are not fully differential. In the reference [1], a degeneration source resistor is used to arrive at the output symmetry. In this paper, we present a modified topology to reduce influence degree of the device parameters on the circuit performances. In addition, the larger VCO gain (KVCO) brings about the worse phase noise [2]. Hence, the topology of switching capacitor is used to enhance the characteristics of phase noise by dividing the wanted frequency band into four sections. Fig.1 shows the schematic of the presented switching-capacitor current reused VCO. The current-reused LC-VCO consists of cross-connected pair transistors M1 and M2, LCtank and two switched capacitors. The current-reused VCO must usually be designed carefully to arrive at symmetrically differential output signals [1]. The equivalent drain capacitance and the transconductance g m resulted from the NMOS and PMOS transistors must be balanced in order that the output wave is fully differential. That means that the proper choice of device parameters will result in the symmetrical behavior of charge and discharge at the two output terminals, and then differential output signals. Degeneration resistances and degeneration capacitors are added to enhance the symmetry of the differential output signals [1,2,3]. Hence, it is an important issue that source-degenerated components r1, r2 must be optimized to enhance the symmetry of output waveforms. In addition, the sourcedegenerated RC topology forms a low-pass filter and is capable of reducing noise. Circuit designThere are two switched capacitors in the presented VCO which could be turn on and off to form four sub-bands. To suppress the loading effect, two inverters are used as output buffers.In the conventional LC-VCOs with a tail current source, the transistors switch alternately. Phase noise is produced by down-conversion of the current source noise component at the 2nd harmonic of the oscillation frequency [3]. However, the presented VCO does not have a common-source node and NMOS and PMOS transistors switch on and 978-1-4244-2642-3/08/$25.00 ©2008 IEEE off at the same time. Therefore, the VCO is inherently immune to the phase noise degradation caused by second-harmonic terms at the comm...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 98%

mentioning

confidence: 99%

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confidence: 99%

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