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The dynamic range (DR) of signals in wireless communications can be very large compared to the required SINAD for demodulation of the wanted channel. Conventional receivers use analog filters and programmable gain amplifiers (PGA) to reduce the DR to fit the ADC with the required SINAD ( Fig. 4.8.1a). In receivers with fulldigital baseband processing, these difficult analog blocks are replaced by flexible digital processing (Fig. 4.8.1b). The burden however is on the ADC as it needs a large bandwidth and SINAD to handle both the wanted and the interferer channels. In the presented filtering ADC (Fig. 4.8.1c), the analog filter and PGA are merged in a Σ∆ A/D converter. Well-known features of continuous-time Σ∆ ADCs, such as the anti-aliasing behavior and low power dissipation, are combined with a filtering signal transfer function (STF). This filtering STF makes the ADC immune to wide-band interferers even if they exceed the maximum allowed input level for the wanted channel. In addition, the input stage features programmable gain control. The merged design is easier to implement than the conventional baseband of Fig. 4.8.1a, while providing the same functionality. Compared to the full-digital architecture of Fig. 4.8.1b, while providing it offers similar flexibility. Area and power consumption are less than those of state-of-the-art implementations of both Fig. 4.8.1a and 4.8.1b.Conventional single-bit Σ∆ ADCs with a feedforward and a feedback loop filter are depicted in Fig. 4.8.2a and b. Due to the high SINAD and the anti-aliasing filtering of the continuous-time implementation, interferers -outside the conversion bandwidth (BW) can be applied. The allowed interferer amplitude is limited by the frequency dependent full-scale of the ADC. Beyond this limit, overloading occurs, and the noise within the conversion BW increases rapidly, degrading the SINAD of the wanted channel. The frequency-dependent full-scale level is, to a first-order approximation, inversely proportional to the linearized STF of the ADC. In the feedforward type ADC, nearby interferers are slightly amplified compared to the wanted channel. The feedback type ADC provides filtering for nearby interferers. Therefore, the input level of these interferers may be higher than the maximum allowed input level for wanted channels. However, the feedback type ADC has poorer power efficiency than the feedforward type because the entire output dynamic range is fed back to every internal node of the loop filter. In the feedforward type, only the first filter stage needs to handle a large dynamic range. The new filtering ADC combines the low power consumption of the feedforward type ADC with the filtering STF of the feedback type.The filtering Σ∆ ADC designed for interferer immunity is depicted in Fig. 4.8.3. The feedforward loop filter, the quantizer and the DAC constitute the conventional Σ∆ ADC. A high-pass filter H HPF (s) has been added in the feedback path. A complementary low-pass filter H LPF (s) has been added to the forward path. Since H HPF (s)+H L...

The Dynamic range (DR) of EA modulators It consists of an analog input X, a CT loopfilter H, a depends on the jitter characteristics of the applied clock.quantizer Q, a digital output Y, and a feedback DAC. If the This paper presents a method to calculate the maximum quantizer is modeled by a gain C and a noise source N, the allowed phase noise and spurious tones on the clock transfer function of the input signal X and quantization which can be applied to the EA modulator (SAM) noise N to the output can be calculated easily. Jitter on the preserving its DR. Equations are derived for four quantizer clock is not a problem because the jitter induced is different feedback DAC topologies used in a SAM . The shaped by the loop gain. The jitter on the DAC clock equations are verified by measurements. however, is directly at the input of the SAM, and will manifest itself at the output of the ADC, and consequently

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It is postulated that the stiffness of current acetabular designs compromises long-term component stability. We present a novel acetabular component design that is horseshoe shaped and has a large diameter bearing. It is made from composite materials and is designed to match the stiffness of subchondral bone. It is intended that stress shielding will be minimised and that the distribution of stress will be improved. The mechanical and biological suitability of the composite has been confirmed. A range of standard and non-standard, pre-clinical, tests have established the robustness and safety of the new component. The efficacy of the new design has been evaluated by clinical trial on 50 patients. Optimal results were obtained using the hydroxyapatite (HA) coated cups. Our results support the new design concept, with the caveat that biological fixation is imperative. Minor design modifications are recommended.