John Leete

CMOS mixers and polyphase filters for large image rejection

This paper presents an in-depth treatment of mixers and polyphase filters, and how they are used in rejecting the image in transmitters and receivers. A powerful phasor-based analysis is used to explain all common image-reject topologies and their limitations, and it is shown how this can replace complex trigonometric equations commonly found in the literature. Practical problems in design and layout that limit the performance of image-reject upconversion and downconversion mixers are identified, and solutions are presented or limits explained. This understanding is put to work in a low-IF CMOS wideband, low-IF downconversion circuit, which repeatedly rejects the image by 60 dB over the wide band of 3.5 to 20 MHz without trimming or calibration.

Analysis and Optimization of Direct-Conversion Receivers With 25% Duty-Cycle Current-Driven Passive Mixers

The performance of zero-IF receivers with current-driven passive mixers driven by 25% duty-cycle quadrature clocks is studied and analyzed. It is shown that, in general, these receivers outperform the ones that utilize passive mixers with 50% duty-cycle clocks. The known problems in receivers with 50% duty-cycle mixers, such as having unequal high- and low-side conversion gains, unexpected IIP2 and IIP3 numbers, and IQ crosstalk, are significantly lowered due to the operating principles of the 25% duty-cycle passive mixer. It is revealed that with an intelligent sizing of the design parameters, the 25%-duty-cycle-mixer-based receiver is superior in terms of linearity, noise, and elimination of IQ crosstalk.

Analysis and Optimization of Current-Driven Passive Mixers in Narrowband Direct-Conversion Receivers

Properties of the current-driven passive mixer are explored to maximize its performance in a zero-IF receiver. Since there is no reverse isolation between the RF and baseband sides of the mixer, the mixer reflects the baseband impedance to the RF and vice versa through simple frequency shifting. It is also shown that in an IQ down-conversion system the lack of reverse isolation causes a mutual interaction between the two quadrature mixers, which results in different high- and low-side conversion gains, and unexpected IIP2 and IIP3 values. With a thorough and accurate mathematical analysis it is shown how to design this mixer and its current buffer, and how to size components to get the best linearity, conversion gain and noise figure while alleviating the IQ cross-talk problem.

A Fully Integrated MIMO Multi-Band Direct-Conversion CMOS Transceiver for WLAN Applications (802.11n)

A single-chip multi-band direct-conversion CMOS MIMO transceiver (2 times 2) targeted for WLAN applications is presented. This transceiver is capable of satisfying the requirements of the Enhanced Wireless Consortium and achieves PHY rates of >270Mb/s. The receivers and transmitters achieve an EVM of better than -41 dB (0.9%) and -40dB (1.0%) operating in legacy g and a modes, respectively. From a 1.8V supply and with both cores operating, the chip draws 275mA in RX mode and 280mA in TX mode.

A 2.4-GHz low-IF receiver for wideband WLAN in 6-/spl mu/m CMOS-architecture and front-end

This paper presents the 2.4-GHz front-end and the first downconversion section of a fully integrated low-IF receiver. The dual-conversion receiver rejects the image repeatably by 60 dB using integrated polyphase filters without calibration or tuning. The gain of the RF mixer and IF amplifier is switchable to slide the available dynamic range of the following stages based on the conditions of the input signal. The front-end and downconversion sections drain 35 mA on average from a 3.3-V supply. Minimum cascade noise figure is 7.2 dB, and maximum cascade IIP3 is -3.4 dBm.

A quad-band GSM/GPRS/EDGE SoC in 65nm CMOS

A quad-band 2.5G SoC integrates all the RF, DSP, ARM, audio and other baseband processing functions into a single 65nm CMOS die. The radio draws a battery current of 49mA in the RX-mode, and 86mA in the GMSK TX-mode. The low-IF receiver achieves a sensitivity of −110dBm at the antenna, corresponding to a noise figure of 2.4dB at the device input. The 8PSK ±400kHz modulation mask is −64.1/62.7dBc for high/low bands, with an RMS EVM of 2.45/1.95%.

A Quad-Band GSM/GPRS/EDGE SoC in 65 nm CMOS

A quad-band 2.5G SoC integrating all the RF, DSP, ARM, audio and other baseband processing functions into a single 65 nm CMOS die is described. The paper focuses on the radio portion mostly, and addresses the challenges of realizing a complete GSM/EDGE SoC with the RF integrated along with the rest of digital baseband circuitry. Several circuit level as well as architectural techniques are presented to realize a very low-cost and low-power 2.5G radio while meeting the stringent cellular requirements with wide margin. The radio draws a battery current of 49 mA in the receiver-mode, and 86/77 mA in the GMSK/8PSK transmit-mode. The low-IF receiver achieves a sensitivity of -110 dBm at the antenna, corresponding to a noise figure of 2.4 dB at the device input. The 8PSK±400 kHz modulation mask is - 64.1/62.7 dBc for high/low bands, with an RMS EVM of 2.45/1.95%. The radio core area is 3.95 mm2 .

A Differential Digitally Controlled Crystal Oscillator With a 14-Bit Tuning Resolution and Sine Wave Outputs for Cellular Applications

This paper describes the design topologies and considerations of a differential sinusoidal-output digitally controlled crystal oscillator (DCXO) intended for use in cellular applications. The oscillator has a fine-tuning range of ±44 ppm, approximately 14 bits of resolution, and an average step size of 0.005 ppm. All signals connecting externally to I/O pins are sine waves for reducing noise, interference, and spurs couplings. The 26 MHz DCXO fabricated in 65 nm CMOS achieves a phase noise of -149.1 dBc/Hz at 10 kHz offset measured at the sine wave buffer output. The DCXO is capable of meeting the stringent phase noise requirements for IEEE 802.11n 5 GHz WLAN devices. A typical frequency pulling of 0.01 ppm due to turning on/off the sine wave buffer is measured. The DCXO dissipates 1.2 mA of current, whereas each sine wave output buffer draws 1.4 mA. The DXCO occupies a total silicon area of 0.15 mm2 .

A Fully Integrated Quad-Band GPRS/EDGE Radio in 0.13μm CMOS

This radio integrates all the receive and transmit functions required to support a quad-band GSM/GPRS/EDGE application into a single CMOS chip. Compared to the published work, this transceiver is implemented in low-cost digital 0.13 mum CMOS, achieves a superior receive and transmit performance, and yet has up to 2x lower receive power consumption, a key requirement in cellular applications.

A Rel-12 2G/3G/LTE-Advanced 3CC Cellular Receiver

This work presents a receiver capable of receiving three simultaneous cellular channels with an aggregate bandwidth of 60 MHz, enabling a 300 Mb/s downlink rate. The receiver has 16 RF LNA ports covering the cellular bands within the 572-2700 MHz frequency range. It supports LTE-advanced Rel-12 Cat6, HSPA+ Rel-11, TD-SCDMA Rel-9, and GSM/EDGE Rel-9. The 40 nm CMOS receiver consumes 13.7 and 17.6 mA of battery current in 3G and LTE modes, respectively, including the PLL, DCXO, and biasing for a single channel.