C. van den Bos

Effect of smooth nonlinear distortion on OFDM symbol error rate

Nonlinear distortion of OFDM signals can significantly increase the receiver symbol error rate (SER). Currently, distortion analyses rely on simulation, not yielding insight into the problem, or apply to specific nonlinearities only. In this letter, general analytic results are presented on the errors resulting from distortion. The results are applicable to smooth nonlinear distortion of an OFDM signal, which is the most common distortion. Simple analytical expressions are derived which allows a designer to determine the SER before performing simulations. Further, it is shown that the error on each OFDM subcarrier is approximately equally large.

The effect of mismatch and disturbances on the quadrature relation of a cross-coupled relaxation oscillator

Cross-coupled relaxation oscillators are capable of producing two stable and highly accurate, quadrature output signals. We present a complete high-level model of the cross-coupled relaxation oscillator in terms of circuit parameters, from which we obtain explicit expressions for duty-cycle, oscillation frequency and output phase relation. They predict the influence of mismatches and other disturbances such as delays, at circuit level. The results provide useful guidelines for the design of a high performance circuit of such an oscillator. The theoretical results are confirmed by simulation and by experiment.

The influence of non-linear distortion on OFDM bit error rate

The influence of bandpass non-linear distortion on an OFDM signal is investigated. The spectrum of the distorted signal and the resulting detection errors are determined. Non-linear distortion of OFDM signals can significantly increase the receiver BER. Previous analyses rely on simulation, or apply to specific non-linearities only. Here, an analysis is presented which is applicable to any weakly non-linear distortion of an OFDM signal. Simple analytical expressions are derived which allow a designer to choose parameters without performing simulations. Further, it is shown that the error on each OFDM subcarrier is approximately equally large.

A 5-GHz combined oscillator/mixer

In this paper, an IQ oscillator/mixer circuit is presented in which the mixers are an integral part of the oscillator. The oscillator alone has accurate quadrature outputs, even in the presence of component mismatch. This precise quadrature is preserved when mixers are incorporated in the oscillator. An oscillator/mixer core for a carrier frequency of 5 GHz, suitable for a low-IF front-end, was designed and tested. The power consumption is 30 mW from a 2.5 V supply, and a phase error of 1deg was measured

Frequency division using an injection-locked relaxation oscillator

In this paper, the use of an injection-locked relaxation oscillator as frequency divider is proposed. An injection-lock divider can achieve high division ratios at a power consumption which is lower than that of a divide-by-two flipflop divider while operating at the same input frequency, making it suitable as a first divider in a frequency synthesizer. The theoretical performance of an injection-locked relaxation oscillator divider is discussed. From this, it is concluded that its phase-noise performance can be brought arbitrarily close to that of the signal to be divided, thus approaching the ideal frequency divider. A test design and measurement results are presented in support of this claim.

A quadrature relaxation oscillator-mixer in CMOS

This paper describes the design of a quadrature cross-coupled oscillator circuit integrated which also realizes the mixer function in a phase lock loop (PLL). This should be able to provide a very accurate phase relation (<1/spl deg/). This combined oscillator/mixer is first evaluated using a high-level model, in up and downconverter configurations. A circuit implementation is then carried out, in which all the variables are kept independent at circuit level, ensuring a practical implementation close to that of the high-level model. The circuit is designed in a standard 0.35 /spl mu/m CMOS technology with an oscillation frequency of 900 MHz, it has an overall area of 521 /spl times/ 515 /spl mu/m/sup 2/ (157 /spl times/ 119 /spl mu/m/sup 2/ for the IQ oscillator/mixer circuit) and a power consumption of 70 mW with a 3 V power supply. The circuit performance is evaluated by simulation.

A 5.8-GHz quadrature cross-coupled oscillator

This paper describes the implementation of a quadrature cross-coupled relaxation oscillator to be used in an OFDM RF front-end transceiver. A prototype of the oscillator was realized in a SiGe BiCMOS technology, and an oscillation frequency of 5.8 GHz was obtained which is 1/6 of the maximum fT of the bipolar transistors. The circuit performance is evaluated by simulation and by experiment.

Effect of smooth non-linear distortion on OFDM BER

Non-linear distortion of OFDM signals can significantly increase the receiver BER. Currently, distortion analyses rely on simulation, not yielding insight into the problem, or apply to specific non-linearities only. In this paper, general analytic results are presented on the errors resulting from distortion. The results are applicable to smooth non-linear distortion of an OFDM signal, which is the most common distortion. Simple analytical expressions are derived which allows a designer to determine the BER before performing simulations. Further, it is shown that the error on each OFDM subcarrier is approximately equally large.