Compact high linearity switchable dual-mode microstrip bandpass filters

A compact highly linear microstrip dual-mode electronically switchable filter is presented. The key characteristics of the dual-mode switchable filter are investigated and described. A second order filter design procedure is outlined to facilitate the realisation of Butterworth and Chebyshev functions. The proposed filter was built and tested with NXP pin diode model BAP65-03. The measured and simulated results are in good agreement. The measured insertion loss in the ON state was 3.0 dB the isolation in the OFF state was 45 dB at the centre frequency. An evaluation of filter distortion is presented for digitally modulated 16 QAM and QPSK signals.

Highly linear reconfigurable UWB filters with independently controlled dual bandnotch

This letter proposes a high-linearity reconfigurable lower ultra-wideband (3.1–5.25 GHz) filter with independently controlled dual bandnotch at WiMAX 3.5 GHz band and satellite communication systems 4.2 GHz band. Reconfigurability has been achieved by the implementation of Graphene based switches (simulation only) and PIN diodes (measurements). The simulation and measurement results in OFF state show an entire bandpass response from 3.1 GHz to 5.25 GHz and with a very low insertion loss. In ON state, the results show that sharp rejections at 3.5 GHz and 4.2 GHz are achieved, with a low passband insertion loss. The two bandnotch operate independently of each other; thus allowing to control the behaviour of the required bandnotch. The third order intermodulation products were also measured in OFF and ON states and the linearity results have been presented. The filter is able to achieve a high performance with good linearity and no significant loss.

Two-Path All-pass Based Half-Band Infinite Impulse Response Decimation Filters and the Effects of Their Non-Linear Phase Response on ECG Signal Acquisition

This paper is based on the novel use of a very high fidelity decimation filter chain for Electrocardiogram (ECG) signal acquisition and data conversion. The multiplier-free and multi-stage structure of the proposed filters lower the power dissipation while minimizing the circuit area which are crucial design constraints to the wireless noninvasive wearable health monitoring products due to the scarce operational resources in their electronic implementation. The decimation ratio of the presented filter is 128, working in tandem with a 1-bit 3rd order Sigma Delta (ΣΔ) modulator which achieves 0.04 dB passband ripples and -74 dB stopband attenuation. The work reported here investigates the non-linear phase effects of the proposed decimation filters on the ECG signal by carrying out a comparative study after phase correction. It concludes that the enhanced phase linearity is not crucial for ECG acquisition and data conversion applications since the signal distortion of the acquired signal, due to phase non-linearity, is insignificant for both original and phase compensated filters. To the best of the authors’ knowledge, being free of signal distortion is essential as this might lead to misdiagnosis as stated in the state of the art. This article demonstrates that with their minimal power consumption and minimal signal distortion features, the proposed decimation filters can effectively be employed in biosignal data processing units.