Multi-Block CMOS LNA Design for UWBWLAN Transform-Domain Receiver Loss of Orthogonality 59 Multi-Block CMOS LNA Design for UWBWLAN Transform-Domain Receiver Loss of Orthogonality

Transform-domain ultra-wideband (UWB) receiver (Hoyos & Sadler, 2006), is a new UWB receiver implementation method, considering a novel approach that utilizes, analog basis expansion of the input signal, followed by parallel sampling of the basis coefficients (Hoyos & Sadler, 2004), to face significant implementation challenges, including achieving sufficient front-end dynamic range, to support desired receiver processing gain, and rejection of large narrowband interferers (NBI), and overcoming channel-induced distortion. This method enables parallel digital signal processing, and leads to considerable complexity reduction, while still achieve a performance very close to Nyquist rate digital receivers, even when operating at a Sub-Nyquist sampling rate, without significant BER penalty, if the truncation error is negligible compared with the additive noise, or if the incurred SNR degradation can be mitigated by the channel decoder (Hoyos & Sadler, 2006). Since the receiver has N parallel paths, the sampling rate for each path will be N times lower than if, a Nyquist rate time-domain ADC were used to sample the input signal. If the front-end frequency selectivity of a conventional receiver does not provide the required attenuation of the adjacent frequencies, the remaining unknown and undesired adjacent channel interference, will fold into the signal band. Thus, by using the orthogonality principle in the frequency domain, the transform-domain receiver can select signals with great accuracy, even if strong interferers are nearby. Unfortunately, there are practical limitations to this solution due, to the limited number of frequency samples that can be taken, because of the complexity in the parallel bank of mixers and integrators needed. This limitation requires us to perform frequency sampling over short time windows, which in turn produces bandwidth expansion due, to convolution in the frequency domain. This frequency expansion implies overlapping (aliasing) in the frequency domain, i.e., loss of orthogonality. 4