Yen-Horng Chen

A 14-band Frequency Synthesizer for MB-OFDM UWB Application

A 14-band frequency synthesizer for UWB application is realized in a 0.18 mum CMOS process. It uses two PLLs and three mixers. The unwanted spurs due to frequency mixing are at least 35dB lower than the output carriers by using a quadrature divide-by-3 circuit and a 2-stage single-sideband mixer. The core circuit area is 1.5 mm2 and the power consumption is 160mW

A SAW-Less GSM/GPRS/EDGE Receiver Embedded in 65-nm SoC

A quad-band GSM/GPRS/EDGE receiver, implemented in 65 nm CMOS, complies with the ETSI standard without the need of external SAW filters. By exploring the properties of passive mixers and current-mode operation from RF to baseband, the receiver can achieve a SAW-filter-like selectivity with inexpensive on-chip components such as resistors and capacitors. In addition, to alleviate the linearity bottleneck at the LNA input stage, Class-AB self-bias LNTA is employed to break the conventional trade-offs among NF, linearity and power consumption. For single-to-differential conversion, external LC-CL baluns (instead of on-chip baluns) are used to balance the on-chip die and external BOM cost. This receiver solution is embedded as a part of a cellular phone SoC and achieves <; - HOdBm sensitivity, >; +1 dBm Out-of-Band Pι dB and consumes 58.9 mA. In FTA test, the receiver passes out-of-band blocker test with >; 4 dB margin.

A SAW-less GSM/GPRS/EDGE receiver embedded in a 65nm CMOS SoC

Over the last decade, significant progress has been made towards increasing integration and reducing bill of material (BOM) for GSM/GPRS/EDGE cellular systems. In modern cellular phones, transmit SAW filters have been largely eliminated with innovative TX architecture and circuits [1] while receive SAW filters are still present. This remains as one of the few bottlenecks in achieving a true low-cost single-chip solution which offers a genuine advantage for high-volume applications. The main challenges of eliminating SAW-based bandpass filters from multiband 2G/2.5G receivers lie in noise-figure (NF) degradation and gain desensitization induced by 0dBm blockers at merely 20MHz away from the −99dBm in-band signal at GSM850/900 band. Furthermore, these unfiltered inter-ferers cause a strong reciprocal mixing effect and result in additional SNR degradation. Therefore, a SAW-less RX is required to have an extremely high dynamic range while maintaining best-in-class NF, LO wideband phase noise (PN) and spur performance.

A 0.13

This paper presents a single-chip CMOS quad-band (850/900/1800/1900 MHz) RF transceiver for GSM/GPRS/EDGE applications which adopts a direct-conversion receiver, a direct-conversion transmitter and a fractional-N frequency synthesizer with a built-in DCXO. In the GSM mode, the transmitter delivers 4 dBm of output power with 1deg RMS phase error and the measured phase noise is -164.5 dBc/Hz at 20 MHz offset from a 914.8 MHz carrier. In the EDGE mode, the TX RMS EVM is 2.4% with a 0.5 dB gain step for the overall 36 dB dynamic range. The RX NF and IIP3 are 2.7 dB/-12 dBm for the low bands (850/900 MHz) and 3 dB/-11 dBm for the high bands (1800/1900 MHz). This transceiver is implemented in 0.13 mum CMOS technology and occupies 10.5 mm2. The device consumes 118 mA and 84 mA in TX and RX modes from 2.8 V, respectively and is housed in a 5 times 5 mm2 40-pin QFN package.

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With limited frequency allocation in the radio spectrum, spectral efficiency has always been the core development of communication systems. To accommodate the increase in demand for wireless data services, RF systems have been challenged to provide better in-channel SNR (EVM) and lower out-of-channel emission. As performance requirements become more stringent, second-order RF circuit impairments, that were previously insignificant, have become major design considerations. One example is the Long-Term-Evolution (LTE) [1]. Compared with previous generations, channel bandwidth has been expanded to 9MHz in most of the sub-GHz bands and 18MHz in the GHz bands. For spectral efficiency, the TX OFDM subcarriers are grouped into Resource Blocks (RBs) that can be dynamically allocated within the channel bandwidth. Noise and spurious emission requirements have become more challenging in the sub-GHz bands, so that Counter 3d-order Intermodulation products (CIM3) has been recognized as an important design parameter [2-4] for LTE RF systems. CIM3 is the result of the lower 3d-order intermodulation (IM3) product of signals at around 1×LO and 3×LO by using mixers with 25% or 50% duty-cycle LO. If an fBB tone is being fed to the TX baseband input, after the mixer and the RF amplifier, the TX RF output will produce the desired signal tone at fLO+fBB and an unwanted CIM3 tone at fL0-3fBB [3]. The adverse effects of CIM3 are shown in Fig. 9.7.1, using LTE Band 13 as an illustration. Band 13 has User-Equipment (UE) TX band from 777 to 787MHz, and RX band at -31 MHz away from TX. Extreme cases of full RB and single RB are considered. At full RBs, modulated CIM3 has a bandwidth three times the desired signal, and it folds directly into the TX channel, degrading the TX EVM and the 1st ACLR (E-UTRA). Furthermore, the ACLR of bandwidth-expanded CIM3 falls into the RX band causing desensitization. When single RB is transmitted, the CIM3 may fall into the restricted bands and violate the spectral emission requirement. Consider the Public Safety Band, where the LTE standard dictates that the emission from 769 to 775MHz has to be less than -57dBm/6.25KHz [1]. If the output power at the antenna is +23dBm and only single RB is being transmitted, the power density is 23dBm/180kHz. Normalizing to power density from 180KHz to 6.25KHz, the power density is 8.4dBm/6.25KHz, resulting in a CIM3 requirement of -65.4dB/6.25KHz. This is challenging for linearity, and also for noise requirement in the case of a SAW-less system. CIM3 suppression techniques such as harmonic rejection and power mixing have been proposed [2-5], but these techniques require extra calibrations and/or off-chip filtering components, which will be described in later paragraphs. This work presents a CIM3 suppression technique by removing the undesired 3rd-harmonic component in the LO signal through LO duty-cycle selection. With this direct root-cause elimination method, the TX meets CIM3 and RX band noise requirements for SAW-less LTE RF systems over process and temperature without calibration and off-chip filtering.