Distributed effects and coupling in RF integrated circuits

Increasing frequencies and higher levels of integration, including integration of complete systems, results in the increased use of passive components such as transmission lines and inductors. Recent publications of wireless transceivers, for example [1], have shown 15 or more inductors on the same silicon substrate in an area of the order of 10-20 mm2. Because of the increased frequencies, long interconnects may no longer behave like an ideal wire with zero delay. Instead it may be more appropriate to think of long interconnect as distributed transmission lines. It will take signals a finite amount of time to travel along such transmission lines. The delay from input to output is equivalent to a phase shift of the output signal with respect to the input signal. Such delay can be problematic in achieving signal alignment, for example, in clock distribution systems, or in the design of combining circuits in power amplifiers. However, the same effects can be exploited, for example, in the design of distributed amplifiers. As well, because of the increased frequency and higher density of components, there can be coupling between components, for example, via conductive coupling through the substrate or via electromagnetic (typically inductive) coupling, for example, from parallel current-carrying wires. Such coupling can present difficulties in achieving isolation between components. However, coupling can also be exploited in the design of transformers, noninvasive testing, and injection-locked oscillators

A low voltage, low power RF CMOS LNA for bluetooth applications using transmission line transformers

This work presents the design and implementation of a 1.2V-1.8V, 2.5 GHz LNA in a mixed-signal 0.18 μm CMOS technology. A standard differential cascode structure was used with off-chip transmission line transformers. A model for the transmission line transformer is presented that shows matching between the LNA and transformer is critical for optimum results. The LNA consumes 2mA at 1.8V while achieving a gain of 8.9dB, a noise figure of 3.22dB and an IIP3 of-5.6 dBm

Design and analysis of very low voltage charge pumps for RFID tags

The design and analysis of very low-voltage driven charge pumps powered by RF telemetry is proposed. The use of thick oxide zero threshold voltage transistors along with appropriately sized boosting capacitors and matching techniques allows for charge pumps capable of achieving high voltage DC outputs with very low input voltages. Two test chips have been fabricated, an 11 stage pump and a 12 stage pump in 1.2V 0.13-μm standard CMOS process. The pumps are capable of generating an output voltage above 1.2 volts with input voltages below 100mV making them ideal for generating DC supplies from low RF scavenged sources

A 5-GHz Radio Front-End With Automatically Q-Tuned Notch Filter and VCO

A low-voltage receiver front-end for 5-GHz radio applications is presented. The receiver consists of a low-noise amplifier (LNA) with notch filter, a voltage-controlled oscillator (VCO), and a mixer. The LNA/notch filter has an automatic Q-tuning circuit integrated with it to provide good image rejection. On-chip transformers are used extensively in the receiver to improve performance and facilitate low-voltage operation. The receiver has a gain of 19.8 dB, noise figure of 4.5 dB, a third-order input intercept point (IIP3) of -11.5 dBm, and an image rejection of 59 dB, and the VCO had a phase noise of -116 dBc/Hz at 1-MHz offset

Capacitively center-loaded transmission lines for compact E-band 90° couplers

A compact 80-GHz band (81-86 GHz) 90° coupler using capacitively center-loaded microstrip transmission lines is proposed. The coupler is implemented in a 0.15 μm GaAs pHEMT technology and has longitudinal and transverse arms of the same characteristic impedances of 50-Ω to reduce the effect of manufacturing tolerance and to facilitate the layout. The experimental results demonstrated a phase difference close to 87° and an amplitude imbalance of less than 1 dB over the entire frequency band of interest (81-86 GHz). The measured return loss is less than 11 dB and the isolation is better than 15 dB. The proposed coupler is well suited for low-cost, high performance, ultra high data rate transceivers for E-band wireless communication systems