• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1143-1149
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• 2006

The microstrip square open loop resonator has been employed to reduce the phase noise in VCO. The microstrip square open loop resonator has the large coupling coefficient value, which makes a high Q value, and has reduced the phase noise of VCO. To increase the tuning range of VCO, varactor diode has been connected at the tunable negative resistance in VCO. The output power and harmonic characteristics of VCO has been obtained 4.83 dBm and -28.83 dBc, respectively. The phase noise of VCO has been $-112.33{\sim}-116.16dBc/Hz$ @ 100 kHz in the tuning range, $5.735{\sim}5.845GHz$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.262-268
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• 2010

In this paper, a high power active tunable bandpass filter made of dielectric resonators and varactor diodes is designed using the active capacitance circuit generating negative resistance for tuning cellular TX, RX band. An active capacitance circuit's series feedback circuit using GaAs HFET whose $P_{1dB}$ is 32 dBm is used for compensating the losses from the varactor diodes of the tunable bandpass filter. The tuning elements, the varactor diodes are used as the back-to-back configuration to achieve the high power performance, The designed active capacitance circuit improves the insertion loss characteristics. The designed 2-stage active tunable dielectric bandpass filter at cellular band can cover from 800 MHz to 900 MHz. The insertion losses at 836 MHz and 881.5 MHz with 25 MHz bandwidth are 0.48 dB and 0.39 dB, respectively. The $P_{1dB}$ of the designed bandpass filter at TX and RX band are measured as 19.5 dBm and 23 dBm, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.847-853
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• 2007

In this paper, a novel push-push voltage-controlled oscillator(VCO) using microstrip square open loop resonator and tunable negative resistance is presented. The microstrip square open loop resonator has the large coupling coefficient value, which makes a high Q value, and has reduced phase noise of VCO. The VCO with 1.8V power supply has phase noise of $-124.67{\sim}-122.67dBc/Hz\;@\;100 kHz$ in the tuning range, $5.744{\sim}5.859 GHz$. The FOM of this VCO is $-202.83{\sim}-201dBc/Hz\;@\;100 kHz$ in the same tuning range. When it has been compared with single-ended VCO using microstrip square open loop resonator, and push-push oscillator using microstrip line resonator, the reduced phase noise has been -8.51dB, and -33.67dB, respectively.

• Journal of electromagnetic engineering and science
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• v.17 no.1
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• pp.34-38
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• 2017

In this paper, we propose an active tunable bandpass filter (BPF) for efficient spectrum sensing in the TV White Space (TVWS) band. By designing a narrow bandwidth, it is possible to improve the sensing probability. The basic circuit configuration involves switching the PIN diode compromising capacitor bank to change the capacitance of the LC resonant circuit. To cover the whole TVWS band effectively, we add a varactor diode, and the bandwidth is set to 25-MHz. We improve the insertion loss by using the active capacitance circuit. The tunable BPF in the TVWS band with a 20-MHz interval is designed to have 11 channels with a bandwidth of 25 MHz and a low insertion loss of 1.7-2.0 dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.12
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• pp.16-21
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• 2007

In this paper, the dual-band voltage-controled oscillator (VCO) using the composite right/left-handed (CRLH) transmission line (TL) and the tunable negative resistance based on the fin diode is presented. It is demonstrated that the CRLH TL can lead to metamaterial transmission line with the dual-band tuning capability. The dual-band operation of the CRLH TL is achieved by the frequency offset and the phase slope of the CRLH TL, and the frequency ratio of the two operating frequencies can be a non-integer. Each frequency band of VCO has to operate independently, so we have used the tunable negative resistance based on the pin diode. When the forward bias has been into the pin diode, the phase noise of VCO is $-108.34\sim-106.67$ dBc/Hz @ 100 kHz in the tuning range, $2.423\sim2.597$ GHz, whereas when the reverse bias has been fed into the pin diode, that of VCO is $-114.16\sim-113.33$ dBc/Hz @ 100 kHz in the tuning range, $5.137\sim5.354$ GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.9
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• pp.813-819
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• 2011

In this paper, a new design method of a tunable oscillator using a suspended-stripline resonator is presented. The negative resistance of an FET mounted on microstrip line(MSL) is combined with a high Q suspended-stripline(SSL) resonator to produce a tunable oscillator with good phase noise. The new MSL-SSL transition facilitates the easy connection between the MSL-based circuits and the SSL module. The proposed oscillator is also frequency-tunable using a tuner located on the top of the SSL housing. The measured phase noise of the implemented oscillator at 3.37 GHz is -108.03 dBc@100 kHz and -135.09 dBc@1 MHz with 50 MHz of frequency tuning.

• ETRI Journal
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• v.31 no.5
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• pp.576-584
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• 2009

A novel tunable transconductor is presented. Input transistors operate in the triode region to achieve programmable voltage-to-current conversion. These transistors are kept in the triode region by a novel negative feedback loop which features simplicity, low voltage requirements, and high output resistance. A linearity analysis is carried out which demonstrates how the proposed transconductance tuning scheme leads to high linearity in a wide transconductance range. Measurement results for a 0.5 ${\mu}m$ CMOS implementation of the transconductor show a transconductance tuning range of more than a decade (15 ${\mu}A/V$ to 165 ${\mu}A/V$) and a total harmonic distortion of -67 dB at 1 MHz for an input of 1 Vpp and a supply voltage of 1.8 V.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.77-80
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• 2008

In this paper, low phase noise VCO using novel compact microstrip spiral resonator is proposed. A spiral resonator has super compact dimension, low insertion losses in the passband and high level of rejection in the stopband with sharp cutoff and a large coupling coefficient value, which makes a high Q value, and has reduced the phase noise. To increase the tuning range of VCO, varactor diode has been connected at the tunable negative resistance in VCO. This VCO has presented the oscillation frequency of $5.686{\sim}5.841GHz$, harmonics -29.83 dBc and phase noise of $-115.16{\sim}-115.17dBc/Hz$ at the offset frequency of 100 KHz.