171
Experimental Study of Phase Noise in Synchronized
HF Class E Oscillator
Vladimir V. Krizhanovskii
Abstract - The phase noise of synchronized HF class E
oscillator built on MOS power transistor was measured, the
experimental results were analyzed.
Keywords - Class E oscillator, Phase noise, Frequency locking,
Synchronization curve.
I. INTRODUCTION
High-efficiency class E amplifiers and oscillators are
candidates for application in telecommunication systems.
Therefore, their noise characteristics represent particular
importance. In order to characterize the effect of
synchronization on the phase noise of class E oscillators, a
series of HF oscillator's phase noise measurements was
performed.
Fig.2 Measured synchronization curves.
Phase noise measurements were performed using Agilent
E4440A power spectrum analyzer and Agilent 33250A signal
generator. For every value of synchronization signal power
the phase noise was measured in the centre of the
synchronization band as well as near the boundaries. Fig.3
shows sample results of phase noise measurements.
II. RESULTS AND DISCUSSION
The Device under test was a 5 MHz class E oscillator with
1 W output power built on MOS power device 2N7000, Fig.1.
The topology and parameters of the output signal of the
oscillator are similar to those in [1].
Fig.3 Phase noise at Psync = -4.1 dBm.
Table 1 compares the phase noise level of free-running
oscillator and that of synchronized oscillator with various
power of synchronization signal for two frequency offsets.
TABLE 1
PHASE NOISE POWER, dBc/Hz
Fig.1 Oscillator schematic; In is the input of synchronization signal.
It is known that the phase noise of synchronized oscillators
is related with the shape of synchronization curves in the
frequency-voltage plane [2]. Fig.2 shows experimentally
observed synchronization curves with the power of
synchronization signal as a parameter. The solid lines are
interpolations of the experimental results with ellipses, while
dashed lines correspond to unstable parts of the
synchronization ellipses that cannot be realized in the
experiment. In obtained experimental results, the tilt of the
synchronization ellipses correspond to the shape of transfer
function of the output network used in class E amplifiers and
oscillators. The frequency synchronization range is delimited
by points where the tangent line to the ellipse becomes
vertical. It can be seen that the frequency synchronization
range of the class E oscillator is not symmetrical with respect
to the frequency of the free-running oscillator.
Vladimir V. Krizhanovskii – Ph.D. Student, Donetsk National
University, Universytetska str., 24, Donetsk 83001, UKRAINE.
E-mail: dangervoves@gmail.com
Psync, dBm
Free-running
0,8
-6,6
Δf = 1 kHz
-73,2
-97
-90,3
Δf = 10 kHz
-86,7
-97.9
-88
III. CONCLUSION
Experimental investigation of synchronized HF class E
oscillator on MOS power transistor was presented. It was
demonstrated that the characteristics of the device under
study comply with the general theory of synchronized
oscillators as long as the peculiarities of class E operation are
taken into account. The typical phase noise of the
synchronized oscillator was measured to be -97 dBc/Hz at
1 kHz frequency offset.
REFERENCES
[1] В. В. Крыжановский, Д. В. Чернов, Экспериментальное исследование фазового шума ВЧ автогенератора класса Е // Вісник Донецького національного
університету, Сер. А: Природничі науки, 2010, Вип.
2.–С. 123-126.
[2] F. Ramírez, M. Pontón, S. Sancho, A. Suárez, PhaseNoise Analysis of Injection-Locked Oscillators and
Analog Frequency Dividers // IEEE Trans. On Microwave
Theory Techn., vol. 56, No. 2 pp.393-407, Feb. 2008.
TCSET'2012, February 21–24, 2012, Lviv-Slavske, Ukraine
Lviv Polytechnic National University Institutional Repository http://ena.lp.edu.ua