ISSN 1063-7397, Russian Microelectronics, 2006, Vol. 35, No. 6, pp. 405–413. © Pleiades Publishing, Inc., 2006.
Original Russian Text © A.S. Korotkov, D.V. Morozov, A.A. Tutyshkin, 2006, published in Mikroelektronika, 2006, Vol. 35, No. 6, pp. 471–480.
1. CHANNEL-SELECT LOWPASS FILTERS:
FUNCTIONS AND BASIC PERFORMANCE DATA
Nowadays, communications systems tend to use a
low or even zero intermediate frequency (IF); the
basic conﬁguration of a zero-IF receiver is shown in
Unlike in superheterodyne receivers, a lowpass ﬁlter
(LPF) rather than a bandpass ﬁlter performs channel
selection with desired selectivity, in conjunction with
quadrature demodulation. This feature represents a sig-
niﬁcant advantage because an LPF is easily integrated
with the rest of a receiver, a further step toward the
implementation of the system-on-chip concept. By
contrast, bandpass ﬁlters with a comparatively high
center frequency and suitable selectivity are still real-
ized as a bulky and costly off-chip component, surface-
acoustic-wave ﬁlters being an example.
Table 1 contains basic performance data on a wide
variety of channel-select LPFs designed for communi-
cations purposes in recent years. Table 2 presents this
data in summary form for the reader’s convenience.
There are several points that can be made about the
results listed in the tables:
(1) The orders of the LPFs are not less than ﬁve.
Low-Power CMOS Switched-Capacitor
Lowpass Filter Using Current Conveyors
A. S. Korotkov, D. V. Morozov, and A. A. Tutyshkin
St. Petersburg State Technical University, St. Petersburg, Russia
Received October 20, 2005
—A new approach is proposed to the design of high-order switched-capacitor LPFs of megahertz cut-
off frequency for communications channel selection. It essentially uses current conveyors instead of op amps
to achieve low power consumption. A ﬁfth-order Chebyshev LPF with a 1-MHz cutoff frequency is thus syn-
thesized and fabricated in a 0.35-
m CMOS technology. The LPF consumes less than 10 mW from a 3-V power
supply and exhibits a third harmonic distortion better than –54 dB in response to a 1-V sinusoidal input at the
cutoff frequency. The rms noise voltage is at most 1.9 mV in a 2-MHz bandwidth.
PACS numbers: 84.30.Vn
Block diagram of the basic zero-IF receiver. Legend: ADC—analog-to-digital converter, DSP—digital signal processor,
LFA—controllable-gain low-frequency ampliﬁer, LNA—low-noise ampliﬁer, LO—local oscillator, LPF—channel-select lowpass
ﬁlter. The LO is realized as a voltage-controlled oscillator.