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For impulse radio ultrawideband communications an 'antenna plus generator' system is co-designed and an on chip generator is integrated into the antenna. This approach does away with the need for intermediate transmission lines conventionally placed between an RF device/generator and an antenna and therefore eliminates the need for a balun, prevents excitation of the common-mode currents and allows the device to be mounted directly on the antenna. The antenna and generator are designed taking into account both impedance matching and the generator's influence on the antenna's radiation properties. The suggested approach is verified experimentally at a scaled up version of the antenna. Index Terms--Antenna feed, antenna matching, balun, impulse radio (IR), integrated circuits, ultrawideband (UWB) antenna.

A novel procedure to approximate wavelet bases using analog circuitry is presented. First, an approximation is used to calculate the transfer function of the filter, whose impulse response is the required wavelet. Next, for low-power low-voltage applications, we optimize the state-space description of the filter for dynamic range, sensitivity and sparsity requirements. The filter design that follows is based on an orthonormal ladder structure with log-domain integrators as the main building blocks. Simulations demonstrate that it approximates the required wavelet base (i.e., Morlet) in an excellent way. The circuit operates from a 1.2-V supply voltage and a bias current of 1.2 [micro]A. Index Terms--Analog electronics, log-domain filters, orthonormal ladder filter, wavelet transform (WT).

Analog RF front-end circuits are typically designed to perform one specific task, while key parameters such as dynamic range, bandwidth and selectivity are fixed by the hardware design and not by the communication system in an adaptive way. As a result, today's receiver topologies are designed to function under the most stringent conditions, which increases circuit complexity and power consumption. However, the conditions under which the RF circuits operate are not fixed but vary widely and depend upon a multitude of factors. Therefore, a concept of design for adaptivity is introduced in this paper. It establishes a trajectory for an all-round performance characterization of adaptive oscillators with an explicit qualitative and quantitative description of all the existing relations and tradeoffs among the oscillator performance parameters. As a proof of concept, an 800-MHz adaptive voltage-controlled oscillator is designed with phase-noise tuning range of 7 dB and more than a factor 3 saving in power consumption, suitable for unobtrusive mobile equipment, foreseen to operate in this band. Index Terms--Adaptive circuits, analog circuits, loop gain, low-power integrated circuit (IC) design, phase-noise tuning, RF circuits, voltage-controlled oscillators (VCOs).

A multistandard/multiband adaptive voltage-controlled oscillator (VCO) satisfying the phase-noise requirements of both second- and third-generation wireless standards is described in this paper (1.8-GHz DCS1800, 2.1-GHz wide-band code division multiple access, and 2.4-GHz wireless local area network, Bluetooth, and digital enhanced cordless telecommunications standards). The design procedure for the VCO is based on an adaptive phase-noise model. A factor of 12 reduction in power consumption with a phase-noise tuning range of 20 dB is demonstrated by adapting the VCO bias to the desired application. The VCO achieves -123-, -110-, and -103-dBc/Hz phase noise at 1-MHz offset in a 2.1-GHz band at supply currents of 6, 1.2, and 0.5 mA, respectively. Index Terms--Adaptive circuits, loop gain, multistandard (MS)/multiband (MB) circuits, phase noise, phase-noise tuning, voltage-controlled oscillators (VCOs).

Translinear filters exhibit unconventional noise characteristics, due to the internal nonlinear behavior. In this paper, the maximal signal-to-noise-ratio and the dynamic range properties of translinear filters are discussed, and the relation between these two specifications and the inherent instantaneous companding is described. Index Terms - Companding, continuous-time filters, noise, translinear.

Log-domain or translinear filters are regarded as being a promising alternative in the area of low-voltage filter design. To date, most publications have reported on synthesis of translinear filters. Although synthesis is more powerful than analysis, it must go together with a generally applicable analysis method in the same domain. In this paper, a general current-mode analysis method is proposed. By using a current-mode approach, we stay close to the existing theory on static translinear circuits, which might be beneficial in developing a general, possibly more powerful synthesis method.

Though the MOS transistor is a four-terminal device, it is most often used as a three-terminal device. Therefore, a large number of possible MOS circuits are overlooked. In this brief, the four-terminal point of view is elaborated with respect to MOS weak inversion translinear circuits, a class of circuits naturally very suitable for low-voltage and low-power applications. Some new circuits are described which sometimes are more suitable for low-voltage applications than bipolar translinear networks performing the same function. It is also shown that, using the back gate, translinear networks can be derived which cannot be realized with bipolar transistors. These network topologies increase the possibilities offered by translinear technology. As an example, measurement results of a low input-voltage current mirror and a sin-circuit are shown.

In this paper, the front-end of a universally applicable analog integrated circuit for hearing instruments is presented. This IC comprises the following functions: a microphone preamplifier, a pickup-coil preamplifier, a second-order high-pass filter and a second-order low-pass filter, both with a controllable cutoff frequency, and an input-controlled automatic gain control with an adjustable knee level. By applying a compression/expansion system and operating all the circuits in the current domain as much as possible, all these functions can be implemented in a single IC, without the need for external components. The test chip demonstrates operation down to 1.05 V and a current consumption between 120 and 175 [[micro]ampere]. The full-custom chip area in a 2.5-[[micro]meter] BiCMOS process (using only vertical NPN's and lateral PNP's) amounts to 2.4 [mm.sup.2].

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.