Hong-Teuk Kim

A Wideband CMOS Low Noise Amplifier Employing Noise and IM2 Distortion Cancellation for a Digital TV Tuner

A wideband CMOS low noise amplifier (LNA) with single-ended input and output employing noise and IM2 distortion cancellation for a digital terrestrial and cable TV tuner is presented. By adopting a noise canceling structure combining a common source amplifier and a common gate amplifier by current amplification, the LNA obtains a low noise figure and high IIP3. IIP2 as well as IIP3 of the LNA is important in broadband systems, especially digital terrestrial and cable TV applications. Accordingly, in order to overcome the poor IIP2 performance of conventional LNAs with single-ended input and output and avoid the use of external and bulky passive transformers along with high sensitivity, an IM2 distortion cancellation technique exploiting the complementary RF performance of NMOS and PMOS while retaining thermal noise canceling is adopted in the LNA. The proposed LNA is implemented in a 0.18 mum CMOS process and achieves a power gain of 14 dB, an average noise figure of 3 dB, an IIP3 of 3 dBm, an IIP2 of 44 dBm at maximum gain, and S11 of under -9 dB in a frequency range from 50 MHz to 880 MHz. The power consumption is 34.8 mW at 2.2 V and the chip area is 0.16 mm2.

Low-loss and compact V-band MEMS-based analog tunable bandpass filters

This paper presents compact V-band MEMS-based analog tunable bandpass filters with improved tuning ranges and low losses. For compact size and wide tuning range, the two-pole filters are designed using the lumped-elements topology with metal-air-metal (MAM) bridge-type capacitors as tuning elements. Capacitive inter-resonator coupling has been employed to minimize the radiation loss, which is the main loss contributor at high frequencies. Two filters have been demonstrated at 50 and 65 GHz. The 65-GHz analog tunable filter showed a frequency tuning bandwidth of 10% (6.5 GHz) with low and flat insertion losses of 3.3 /spl plusmn/ 0.2 dB over the entire tuning range.

V-band 2-b and 4-b low-loss and low-voltage distributed MEMS digital phase shifter using metal-air-metal capacitors

Low-loss digital distributed phase shifters have been developed using micromachined capacitive shunt switches for V-band applications. Instead or conventional metal-insulator-metal capacitors, high-Q metal-air-metal capacitors were used in series with the microelectromechanical system (MEMS) shunt capacitive switches to minimize the dielectric loss. The operation voltage for the phase shifters was also reduced by applying the bias directly to the MEMS shunt switches through choke spiral inductors. Fabricated 2-b (270/spl deg/) and 4-b (337.5/spl deg/) distributed phase shifters showed low average insertion losses of 2.2 dB at 60 GHz and 2.8 dB at 65 GHz, respectively. The average phase errors for 2-b and 4-b phase shifters were 6.5% and 1.3%, respectively. The return losses are better than 10 dB over a wide frequency range from 40 to 70 GHz. Most of the circuits operated at 15-35-V bias voltages. These phase shifters present promising solution to low-loss integrated phase shifting devices at the V-band and above.

Low-loss analog and digital micromachined impedance tuners at the Ka-band

Presents new types of analog and digital micromachined impedance tuners. Analog impedance tuners using resonant unit cells realized by tunable micromachined capacitors showed a wide tuning range equivalent to almost two quadrants of the Smith chart with a maximum voltage standing-wave ratio (VSWR) of 21.2 at the Ka-band. Frequency variability is also provided through the use of J-inverters with tunable capacitors. Also presented is a digital micromachined tuner, where the short-circuited shunt stubs are loaded with microelectromechanical system (MEMS) capacitive switches. The electrical length of the stub and the overall impedance of the tuner are thus controlled according to the switching states of the MEMS capacitors. The digital tuner presented impedance ranges suitable for load impedances of the RF power transistors and showed a high maximum VSWR of 32.3. Compared with the state-of-the art tuners using field-effect transistors, micromachined tuners of this paper show superior VSWR ranges as well as wide impedance ranges. Micromachined tuners are very promising for low-loss tuning of the monolithic circuits as well as for accurate noise and power characterization.

A CMOS Harmonic Rejection Mixer With Mismatch Calibration Circuitry for Digital TV Tuner Applications

A harmonic rejection mixer with mismatch calibration circuitry in direct-conversion receiver architecture for digital TV tuner applications is designed and fabricated in 0.18-mum CMOS technology. Odd harmonic mixing in the 48-862 MHz digital TV frequency band between the input signal and the local oscillator harmonics is a critical problem for direct-conversion receivers which require a harmonic rejection of over -60 dBc for ATSC terrestrial and cable digital TV standards. Without calibration, harmonic rejection mixers show a rejection ratio of the third and fifth harmonics in the range of -30 to -40 dBc due to phase and/or gain mismatch. The implemented harmonic rejection mixer with the proposed calibration circuitry consistently achieves more than -70 dBc of third harmonic rejection without degrading other performances such as gain, noise figure, linearity, and power consumption.

A new micromachined overlay CPW structure with low attenuation over wide impedance ranges and its application to low-pass filters

In this paper, a new micromachined overlay-coplanar-waveguide (OCPW) structure has been developed and its characteristics are studied in detail as a function of the line parameters. In OCPW, the edges of the center conductors are lifted by micromachining techniques and partially overlapped with the ground plane to facilitate low-impedance lines. The elevated center conductors help to reduce the conductor loss by redistributing the current over a broad area. Comparative experiments on low-loss and lossy substrates also confirm the screening effect from the substrate losses by confining the electric field in the air between the overlapped conductor plates. Compared with the coplanar-waveguide (CPW) lines, the OCPW lines show wider impedance range (25-80 /spl Omega/) and lower loss (<0.95 dB/cm at 50 GHz). The advantages of OCPW for low-Z/sub 0/ lines are utilized to realize a high-performance stepped-impedance low-pass filter at X-band. The OCPW filter shows distinct advantages over the conventional CPW filter in terms of size, loss, skirt, and stopband characteristics.

A CMOS Wideband RF Front-End With Mismatch Calibrated Harmonic Rejection Mixer for Terrestrial Digital TV Tuner Applications

A wideband direct-conversion RF front-end for Advanced Television Systems Committee terrestrial digital TV (DTV) tuner applications is realized in a 0.18-μm CMOS technology. In order to effectively solve the critical local oscillator (LO) harmonic mixing problem in an ultra-wideband frequency environment of 48-860 MHz, the combination of a mismatch calibrated harmonic rejection mixer (HRM) and a simple preceding integrated third-order passive RF tracking filter with an external inductor is utilized to obtain 60-80 dB of harmonic rejection for all odd-order harmonic mixing within the DTV spectrum. In addition, an efficient novel calibration algorithm for the HRM is proposed in order to simplify the compensation process. The RF front-end also includes a broadband noise-canceling low-noise amplifier, an attenuator to cover the wide dynamic range, an LO multiphase generator, and peripheral circuits such as an I2C serial interface for digital control. The implemented CMOS RF front-end achieves a total gain of 40 dB, output third-order intercept point of 30 dBm, and noise figure of 5.5 dB while consuming a low power of 140 mW from a 1.8-V supply voltage.

Millimeter-wave micromachined tunable filters

Novel types of MM-wave tunable filters using micromachined variable capacitors are presented. In order to demonstrate this concept, two bandpass filters, one with 2-pole lumped elements and the other with 2-pole resonators are designed at Ka-band and fabricated using MEMS technology. With applied bias, the center frequency shifts as much as 1.1 GHz (4.2%) at 26.6 GHz, and 0.8 GHz (2.5%) at 32 GHz, was measured for lumped elements and resonators filter, respectively. These results show the potentials of micromachined tunable filters for low cost, highly integrated transmitter and receiver for MM-wave multi-band communication systems.

A compact V-band 2-bit reflection-type MEMS phase shifter

Air-gap overlay CPW couplers and low-loss series metal-to-metal contact microelectromechanical system (MEMS) switches have been employed to reduce the loss of reflection-type MEMS phase shifters at V-band. Phase shift is obtained by changing the lengths of the open-ended stubs using series MEMS switches. A 2-bit [135] reflection-type MEMS phase shifter showed an average insertion loss of 4 dB with return loss better than 11.7 dB from 50 to 70 GHz. The chip is very compact with a chip size as small as 1.5 mm /spl times/ 2.1 mm.

Tunable millimeter-wave filters using a coplanar waveguide and micromachined variable capacitors

In this paper, new micromachined tunable bandpass filters for multi-band millimeter-wave telecommunication systems are proposed. Two types of millimeter-wave tunable filters have been fabricated using micromachining technology and the responses of the filters have been measured: one type is a two-pole lumped element filter and the other a two-pole resonator filter. The frequency tunability of the filter has been achieved by changing the gap between a common coplanar waveguide ground plate and a movable cantilever beam connected to the transmission line with a controllable range of 2.5 µm. The deflection of the cantilever beam has been measured with applied dc voltage. With the applied bias voltage from 0 to 50 V, the fabricated filters have shown center frequency shifts of 0.6 GHz (2.3%) at 26.6 GHz and 0.8 GHz (2.5%) at 32 GHz for the lumped element and resonator filters, respectively. The mechanical lifetime of the fabricated gold cantilever structure has been tested by observing the existence of the spring memory phenomenon; there is no memory phenomenon or breakdown until a repeated actuation of 1.6×108 cycles.