Esa Tiiliharju

An active differential broad-band phase splitter for quadrature-modulator applications

Area-efficient single-ended-to-differential phase-splitter (balun) integration is difficult for frequencies below 6 GHz. Few broad-band solutions are available, and those given in the literature often introduce quite high amplitude and/or phase errors to differential signaling. In this paper, a cascade of differential pairs is shown always to outperform any single-stage solution, and the measurement data for a two-amplifier prototype are supplied to support the theory. The prototype circuit was realized on 0.8-mum SiGe as a 2.5-V RF integrated circuit measuring 1.2times1.2 mm2 including pads. The measured gain error is better than -1 dB up to 4.6 GHz, while phase difference is between 179.7deg-180.9deg in 0.6-4.1 GHz. The application of the realized phase splitter in a broad-band quadrature modulator is discussed

A 0.75-3.6GHz SiGe direct-conversion quadrature-modulator

A 0.75-3.6GHz SiGe direct-conversion quadrature-modulator has been implemented in 0.8/spl mu/m SiGe with integrated baluns in its RF-signal paths. Measured performance in 0.75-3.6GHz includes IRR better than -40dBc with output power levels in excess of -20dBm. For this performance circuit draws 46mA from a single 2.5V supply.

Low voltage circuits for a single chip 2 GHz transceiver for mobile telecommunication

Low voltage circuit solutions for a 2 GHz radio receiver/transmitter have been developed. The circuitry consists of a broad-band low noise amplifier, 2 GHz AGC and mixer circuits, circuits for the AGC-gain control, IF high Q band-pass and low-pass filters and high speed IF A/D- and D/A converters. All the circuit blocks and the whole RF front-end have been realized. The main design requirement has been a low supply voltage below 3 V. The matched RF port impedance is 50 /spl Omega/.

Current-mode up-converting D/A-interface for mobile communication transmitter applications

A low voltage low power current-mode D/A interface with smoothing filter and upconversion mixer is presented. The D/A-converter is a binary weighted current-switching converter with 8-bit resolution. The uni-directional D/A-output currents are converted to bi-directional input currents for a differential current-mode 1 MHz low-pass filter by a common-mode feedforward circuit. The smoothing filter and current gain amplifier use high-gain current amplifiers using dynamically biased low distortion transconductance output stage. The filtered and amplified current is then fed to a current-switching mixer with off-chip loads. The filter operates with down to a 3 V supply voltage while the D/A-converter can operate even with 2.5 V supply. The harmonic distortion of the filter is typically lower than -50 dBc and thus more than 8-bit spurious free range can be achieved by oversampling.

A Low-Power 3V Lowpass OTA-C Filter for Megahertz Range

By applying a signal-flow graph (SFG) based filter synthesis an active OTA-C topology for integration of a 5-degree elliptic lowpass (LP) filter has been designed. The dynamic range has been maximized for this single-ended OTA-C filter, which has floating capacitors. This has been done through the use of an optimizing circuit simulator. Thus low-voltage (3V) operation despite high signal amplitudes (1Vpp) has been achieved. A linearized operational transconductance amplifier (OTA) has been designed and optimized for the filter. For comparison purposes the single-ended design has been converted to a fully differential one with an additional +6dB of gain. Integrated filters realized with a 1.2 μm CMOS process have been thoroughly measured. The filters are especially applicable for mobile communications because of low power consumption.

Complementary bipolar devices for base station applications

A high dynamic range (DR) current reuse mixer and a linear push-pull buffer with an active area of 0.11 mm times 0.1 mm were realized for base station applications in a 5-V complementary 0.4-mum SiGe process. At 2 GHz, a test block with the proposed mixer achieves a nominal measured DR of +154 dB, while drawing 29 mA from a 3.3-V supply, whereas the push-pull buffer outputs an OP1dB of +9 dBm, while drawing 33 mA from a 5-V supply.

A quadrature-modulator for 0.6-2.6 GHz with frequency doubler

The proposed quadrature-modulator integrates a frequency doubler with a five-stage polyphase filter driven quadrature modulator for single-sideband transmitter applications. Application of a dual-feedback buffering amplifier produces a combination of high output power, low distortion components and power dissipation.

Up-conversion mixers in a complementary 0.4/spl mu/m SiGe process

In this paper a 0.4/spl mu/m complementary SiGe process is used to fabricate up-conversion mixers for base-station applications. A current feedback mixer, and a mixer with a folded input, was designed in order to test benefits obtainable from the use of equally fast PNP-and NPN-transistors. The target was to improve linearity and to increase output compression point (OP/sub -1dB/) of the mixers. A +5dBm output compression point at 2GHz was measured while drawing 43mA from 5V voltage supply.

A biased low-voltage BiCMOS mixer for direct up-conversion

A biased BiCMOS mixer with increased V/sub IN/,/sub CMR/ for low-voltage direct up-conversion applications is proposed. The mixer reduces power dissipation by as much as -48% as compared to prior solutions. Simultaneously linearity and dynamic range are increased. This BiCMOS mixer cell achieves nominal conversion gain performance with a supply voltage as low as 1.8 volts.

Direct-conversion quadrature-modulator for 0.8-GHz with flip-chip passives [BiCMOS RF IC]

This direct-conversion quadrature-modulator for 0.8-1 GHz combines a highly linear DC-connected DB-mixer, 50 /spl Omega/ matched input and output buffers, a two-stage polyphase filter for in/quadrature-phase local generation, and flip-chip passives for better than 42 dB spurious attenuation.