19.7-MHz Chebyshev LPF Targets IEEE 802.11n

March 12, 2008
The IEEE 802.11n wireless-local-area-networking (WLAN) standard employs a high-throughput extension option. As a result, a WLAN system's bandwidth can be 40 MHz in support of higher data rates. When the direct-conversion architecture is ...

The IEEE 802.11n wireless-local-area-networking (WLAN) standard employs a high-throughput extension option. As a result, a WLAN system's bandwidth can be 40 MHz in support of higher data rates. When the direct-conversion architecture is employed for these systems, a lowpass filter (LPF) with a bandwidth of 10 and/or 20 MHz is required. The design of a wideband LPF involves the selection of both the filter inductor-capacitorresistor (LCR) prototype (i.e., Butterworth or Chebyshev) and Gm C and active-RC. Shouhei Kousai and Mototsugu Hamada from Toshiba Corp.'s Center for Semiconductor Research and Development and Fui Ito and Tetsuro Itakura from Toshiba's Mobile Communication Laboratory have presented a quality-factor (Q) -tuning scheme that realizes wideband Chebyshev active-RC filters with reduced biasing current requirements.

This fifth-order LPF with a Q-tuning circuit has been implemented for draft IEEE 802.11n in 0.13-m CMOS technology. According to the researchers, the proposed Q-tuning technique results in a low-power, 19.7-MHz, active-RC Chebyshev LPF. The filter boasts 2 dB gain, 30 nV/Hz input-referred noise, and -113 dBV input power at 1-dB compression. With an area of just 0.2 mm2, it draws 7.5 mA current from a 1.5-V supply.

When the pole frequency is comparable to an amplifier's gain-bandwidth (GBW) product, one should take into account the pole of a variable resistance to tune the bandwidth. In addition, the insertion of a variable resistor into a lossy integrator is critical to the compensation of poles. See "A 19.7-MHz, Fifth-Order Active-RC Chebyshev LPF for Draft IEEE 802.11n with Automatic Quality-Factor Tuning Scheme," IEEE Journal of Solid-State Circuits, November 2007, p. 2326.

Sponsored Recommendations

Frequency Modulation Fundamentals

March 14, 2024
The development of crystal-clear FM communications was an innovation of genius and toil. Utilized today in applications such as radar, seismology, telemetry and two-way radios...

44 GHz Programmable Signal Generator

March 14, 2024
The Mini-Circuits SSG-44G-RC is a 0.1 to 44 GHz signal source with an RF output range of -40 to +17 dBm with fine resolution. This model supports CW and pulsed (? 0.5 ?s) outputs...

Webinar: Introduction to OTA Measurement for mmWave and Sub-THz

Feb. 19, 2024
Join Jeanmarc Laurent, a leading expert from MilliBox, for an exclusive live webinar showcasing a complete Over-the-Air (OTA) testing system setup. In this immersive session, ...

Using a CMT VNA with Socket Server

Feb. 19, 2024
This application note describes use of a software application CMT Socket Server which is distributed and supported by Aphena Ltd. Please email [email protected] regarding purchase...