A LOW POWER, LOW PHASE NOISE CMOS LC OSCILLATOR

Int. Journal of Electrical & Electronics Engg.

Vol. 2, Spl. Issue 1 (2015)

e-ISSN: 1694-2310 | p-ISSN: 1694-2426

A LOW POWER, LOW PHASE NOISE CMOS LC OSCILLATOR 1

Pankaj Aseri, 2R.C Gurjar 1,2 Microelectronics and VLSI Design, E&I Department, Shri G. S. Institute of Technology and Science, Indore, M.P, India 1

pankajaseri17@gmail.com,2rgurjar@sgsits.ac.in

Abstract:- In this paper a Double Cross Coupled Inductor capacitor based Voltage Control Oscillator (LC-VCO) is designed. In the proposed circuit the phase noise, tuning range with respect to control voltage, output power and the power dissipation of the circuit is analysed. Phase noise of approximate -96 dBc/Hz at frequency of 1MHz, frequency tuning range of 4.8 to 8.3 GHz (corresponding to 53.0% tuning range) obtained by varying the control voltage from 0 to 2.0 V, Output power of circuit -8.92 dBm at 50 Ohm resistance terminal and the power consumption of Circuit is 3.8 mW. This VCO are designed for 5.5 GHz. The circuit is designed on the UMC 180nm CMOS technology and all the simulation results are obtained using cadence SPECTRE Simulator.

Keywords:- Phase Noise, LC-Tank, CMOS, Voltage controlled Oscillator (VCO), Low power.

I. INDTRODCTION The typical performance parameters of a VCO are phase noise, tuning range, output power and DC power consumption [1]. The VCO is the most important building block of RF IC design. It play a vital role in many applications such as GSM, Bluetooth, WLAN, Wireless Personal Area Network (WPAN) and Wireless Sensor Network etc. [2]. The most difficult task is to design the Voltage Control Oscillator in the Front end block of RF-IC design. In the today’s world of perfection in technology there is a need to design and develop the circuit with Low power and Low noise at the Higher Frequency. Out of the total power consumption of a system the oscillator power consumption can be a significant portion. So over- all power consumption can be reduced by minimizing the power consumption of the VCO [2]. Some basic oscillator circuits such as local oscillator are limited to the Mixer circuits at receiver end. But, at the high frequency the different topology of oscillators are used that are capable to provide low phase noise and most important term smaller power at high frequency range i.e. Radio frequency range.

For higher quality receivers, an L C oscillator topology is chosen over a relaxation oscillator because the band pass nature of the resonant tank in the L C oscillator provides the lowest phase noise [3]. In this paper, LC Voltage Controlled Oscillator is designed, the proposed circuit shows frequency tuning range in Giga Hertz due to variation in control voltage variation.

In the SECTION II and SECTION III of this paper provides information about the LC-VCO circuit description and theoretical analyses of proposed circuit.

SECTION IV and SECTION V shows the simulation results and conclusion.

II. LC-VCO CIRCUIT DESCRIPTION The schematic circuit of the double cross coupled differential LC-VCO including the differential buffer at the output side is shown in Fig.1. The proposed LC-VCO form by the PMOS and NMOS, inductor, and capacitor. This LC-VCO is having of Cross Coupled PMOS transistors (M4, M5) and Cross Coupled NMOS transistors (M0, M3).

Here PMOS and NMOS pairs are in parallel and due to this negative resistance is generated. M14 and M12 transistors are used as an output buffer. For biasing proposed circuit a current mirror technique is used. (M1, M2) transistors are being used as a current mirror. The Oscillation frequency can be obtain from M14 and M12 NMOS transistors. This proposed circuit provides better Phase Noise performance measure because of double switch Cross Coupled structure.

Fig: 1. Cross Coupled double switch LC-VCO. III.THEORITICAL ANALYSES OF PROPOSED CIRCUIT The proposed circuit shown in the fig.1 consists of inductor and voltage controlled capacitor (capacitor design through MOS transistor) these two passive element forms or resonant tank circuit. In the proposed circuit MOS transistors (M1, M2) and (M3, M4) are cross coupled transistors, which forms negative resistance and this negative resistance basically compensated the resonator losses. Voltage across the tank circuit is given by:-

≈ A sin( )

(1)

Where = ωt, ω being the angular frequency of oscillation.

Equations for bias current ( ) in NMOS and PMOS pair is as follows:-

NITTTR, Chandigarh

EDIT -2015

18

Int. Journal of Electrical & Electronics Engg.

Vol. 2, Spl. Issue 1 (2015)

+

=

(2)

+

=

(3)

And also for PMOS pair

If transconductance PMOS and NMOS are gmp and gmn respectively, from the small signal behaviour and analyse we can relate negative resistance Rnegative with the transcondutances of NMOS and PMOS shown below:-

If gmp = gmn = gm. Then we have >

=−

e-ISSN: 1694-2310 | p-ISSN: 1694-2426

Fig: 4 The Phase Noise performance of circuit.

Fig: 5 The Tuning range response of circuit i.e. graph between Frequency v/s Vcn (Control Voltage).

By varying of Control Voltage from 0 Volts to 2 Volts, the Oscillation frequency varies from 4.8 GHz to 8.3 GHz. The percentage tuning is measured to be 53%.

(4) (5)

The transistors (M5, M6) are current mirror which provide or maintain the tail current of VCO and provide current mirror action. Transistor (M7, M8) act as common drain output buffer and having large input impedance.

IV.SIMULATION RESULTS In this section, we have shown all simulation results of double cross coupled LC-VCO. This VCO is designed using UMC 180nm CMOS technology and is simulated with Cadence Spectre simulator. This work has used estimated value of inductance as L= 2nH and a variable MOS based capacitor. For all measurements, we have chosen following parameters as Vdd (power supply) = 1.8V and biasing current Ibias, M1 = 1mA. The DC power consumption of about <= 3.8 mW is obtained. Fig. 2 shows the Oscillation waveform of LC-VCO. This Oscillation is produced by the tank circuit, i.e. inductor (L) and Capacitor (Ceq) in parallel connection forms the parallel RLC circuit.

Fig. 4 The Phase Noise performance of circuit.

Fig: 5 The Tuning range response of circuit.

Fig: 2 Oscillation Waveform of LC VCO

Fig: 3 Oscillation of frequency at two output nodes Vout+ and Vout- of LC-VCO. 19

NITTTR, Chandigarh

EDIT-2015

Int. Journal of Electrical & Electronics Engg.

Vol. 2, Spl. Issue 1 (2015)

TABLE.1 COMPARISON AND PERFORMANCE SUMMARY OF LC-OSCILLATOR WITH EARLIER WORKS Parameters This [1] [4] [5] Work Process (nm)

180

250

180

180

Oscillation Frequency (GHz)

5.5

5.5

4.2

4.25

Core Current (mA)

1

0.83

6

4

Supply voltage (V)

1.8

2.5

1

2

Power Dissipation(m W) Tuning range (%)

3.8

2.075

6.0

8.0

53

16.9

42

30

Phase Noise (dBc/Hz)

-95.6 @1MH z

-89.77 @1MH z

-116 @1MH z

-114 @1MH z

7)

8)

e-ISSN: 1694-2310 | p-ISSN: 1694-2426

technique”, IEEE Microw. Wireless Compon. Lett. , vol. 19, no. 4, Apr. 2009, pp. 230-232.

M. Ebrahmzadeh, "Design of an Ultra-Low Power Low Phase Noise CMOS LC Oscillator," International Scholarly and Scientific Research & Innovation, vol. 5, IEEE 2011, pp. 931-934, Wen-Cheng Lai1, J. F. Huang, C. M. Hsu and Wang-Tyng LAY, “A 10-GHz Low Power CMOS Voltage Controlled Oscillator Chip Design for Wireless Application” Computer, Consumer and Control (IS3C), 2014 International Symposium on Department of Electronic Engineering, IEEE 2014, pp. 1034 – 1036.

V.CONCLUSION This design shows improved performance of Double cross coupled LC-VCO. The integrated CMOS LC-VCO uses double cross coupled transistor, an inductor and a capacitor (using MOS varactors). This CMOS LC-VCO is implemented using UMC 180nm CMOS technology and is simulated using Cadence SPECTRE simulator. This design has measured phase noise performance of -95.6 dBc/Hz at 1MHz and -116.3 dBc/Hz at 3MHz. It consume 3.8mW power at 1.8V DC voltage supply. The tuning range of this circuit is from 4.3 GHz to 8.3 GHz for 0V to 2V control Voltage respectively i.e. about 53% tuning range. This design finds its application in RF field because of its low power, low area and high speed. Comparison and performance summary of this work and earlier Oscillator work is shown in Table.1 REFERENCE 1)

2)

3)

4)

5)

6)

S. Haddadinejad, Achim Noculak and Michael Hinz, A Low Power, Small Area, Fully Integrated 5.5 GHz CMOS LC-VCO, Microelectronics and Electronics (PRIME), 2014 10th Conference on Ph.D. Research in IEEE 2014, pp. 1-4.

U K Nanda, P K Rout D P Acharya, S K Patra, Department of ECE, National Institute of Technology, Rourkela, India. “Design of Low Power 3.3-4 GHz LC VCO using CMODE” International Conference on Emerging Trends in Computing, Communication and Nanotechnology (ICECCN 2013), IEEE 2013, pp. 717-720.

T.I. Ahrens and T. H. Lee, “A 1.4-GHz 3-mW CMOS LC Low Phase Noise VCO using Tapped Bond Wire Inductances”, International Symposium on Low Power Electronics and Design, pp. 16-19, 1999.

S. Rong and H. C. Luong, “A 1 V 4 GHz-and-10 GHz transformerbased dual-band quadrature VCO in 0.18 m CMOS”, in IEEE CICC 2007, pp.817-820.

S. Y. Lee and C. Y. Chen, “Analysis and design of a wide-tuningrange VCO with quadrature outputs”, IEEE Trans. Circuits Syst. II, Exp. Briefs, vol. 55, no. 12, Dec. 2008, pp. 1209-1213.

S. L. Jang, S. H. Huang, C. C. Liu, and M. H. Juang, “CMOS Colpitts quadrature VCO using the body injection-locked coupling

NITTTR, Chandigarh

EDIT -2015

20