Circuits and architectures for broadband spectrum channelizers with sub-band gain control

Broadband receiver architectures for full-band or concurrent multi-band reception of signals are required in several applications. One approach to implementing such receivers is a spectrum channelizer that employs a frequency-folded analog-to-digital converter (FF-ADC). The design downconverts and channelizes a broadband input signal into multiple sub-bands at baseband by employing the harmonics of non-overlapping rectangular clocks. The downconverted and aliased baseband signal in each path is digitized by a baseband ADC, referred to as a sub-ADC below, that operates with a sampling rate that is lower than the Nyquist sampling rate set by the full bandwidth of the input signal. Sub-band separation is performed through digital harmonic rejection (HR) and image rejection (IR). The design operates similar to a time-interleaved ADC, except that it significantly reduces the bandwidth requirement of the samplers. If rectangular pulse waveforms are used in the FF-ADC down-converter, all sub-bands experience nearly equal gain during frequency down-conversion. Since all sub-bands are aliased to baseband before they are separated in the digital domain, a sub-band with large relative power can reduce the sub-ADC dynamic range that is available for other sub-bands, in addition to appearing as a blocker for other sub-bands. The research presented in this dissertation addresses approaches to overcome this issue, by embedding sub-band gain control within an FF-ADC. Chapter 2 proposes an approach that employs pulse-width-modulated local oscillator (PWM-LO) waveforms in the polyphase paths of an FF-ADC for scaling individual sub-band signal levels at baseband before digitization. The PWM-LO waveforms, which directly drive switches in each path, can be used to vary the gain in each sub-band by varying the level of harmonics in the waveforms. This is achieved by controlling the pulse-widths of the PWM-LO waveforms. This design avoids the requirement for N ×N switch matrices and variable transconductance cells in prior demonstrated approaches. The proposed architecture makes it possible to vary the spectral response of the FF-ADC with low signal-path complexity. Prediction of pulse widths for the desired harmonic, and hence the gain profile across all sub-bands, is performed using an off-chip supervised learning approach employing a neural network. Chapter 3 presents the implementation of a spectrum channelizer employing the PWM-LO-based sub-band amplitude control. The design allows for scaling the relative gain of the sub-bands over a 20-dB range. This relaxes the compression performance of the channelizer baseband and the sub-ADC dynamic range in the presence of sub-bands with significantly higher signal levels. Gain control on individual sub-bands is performed by employing customized PWM-LO waveforms,where the PWM-LO pulses are generated using delay-locked loops (DLLs). The off-chip neural-network based learning technique for estimating the PWM symbol pulse widths required for setting the desired LO harmonic levels is described. A 1.6 GS/s spectrum channelizer IC is implemented in a 65-nm CMOS process to verify the architecture. The measured channelizer gain is 51.6-56.5 dB without gain scaling and provides a range of 37-59 dB with PWM-LO gain control. Gain-scaling at a specific harmonic improves blocker compression in an unattenuated sub-band from -34 dBm to -16 dBm. The in-band gain compression with gain-scaling also increases from -32 dBm to -17 dBm. Chapter 4 describes a spectrum channelizer that uses voltage-mode downconversion. The approach requires a single voltage-mode input amplifier to drive the downconversion switches. Frequency-folding and sub-band gain control are achieved in a single signal path. This contrasts with the current-mode approach that requires a main FF-ADC path and a separate auxiliary path for sub-band gain control. By avoiding the requirement for an auxiliary input path, the approach presented here significantly simplifies the signal chain with identical gain-scaling capability. The contributions of this research and scope for future related work are summarized in Chapter 5.Electrical and Computer Engineerin

Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease

Background: Experimental and clinical data suggest that reducing inflammation without affecting lipid levels may reduce the risk of cardiovascular disease. Yet, the inflammatory hypothesis of atherothrombosis has remained unproved. Methods: We conducted a randomized, double-blind trial of canakinumab, a therapeutic monoclonal antibody targeting interleukin-1β, involving 10,061 patients with previous myocardial infarction and a high-sensitivity C-reactive protein level of 2 mg or more per liter. The trial compared three doses of canakinumab (50 mg, 150 mg, and 300 mg, administered subcutaneously every 3 months) with placebo. The primary efficacy end point was nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. RESULTS: At 48 months, the median reduction from baseline in the high-sensitivity C-reactive protein level was 26 percentage points greater in the group that received the 50-mg dose of canakinumab, 37 percentage points greater in the 150-mg group, and 41 percentage points greater in the 300-mg group than in the placebo group. Canakinumab did not reduce lipid levels from baseline. At a median follow-up of 3.7 years, the incidence rate for the primary end point was 4.50 events per 100 person-years in the placebo group, 4.11 events per 100 person-years in the 50-mg group, 3.86 events per 100 person-years in the 150-mg group, and 3.90 events per 100 person-years in the 300-mg group. The hazard ratios as compared with placebo were as follows: in the 50-mg group, 0.93 (95% confidence interval [CI], 0.80 to 1.07; P = 0.30); in the 150-mg group, 0.85 (95% CI, 0.74 to 0.98; P = 0.021); and in the 300-mg group, 0.86 (95% CI, 0.75 to 0.99; P = 0.031). The 150-mg dose, but not the other doses, met the prespecified multiplicity-adjusted threshold for statistical significance for the primary end point and the secondary end point that additionally included hospitalization for unstable angina that led to urgent revascularization (hazard ratio vs. placebo, 0.83; 95% CI, 0.73 to 0.95; P = 0.005). Canakinumab was associated with a higher incidence of fatal infection than was placebo. There was no significant difference in all-cause mortality (hazard ratio for all canakinumab doses vs. placebo, 0.94; 95% CI, 0.83 to 1.06; P = 0.31). Conclusions: Antiinflammatory therapy targeting the interleukin-1β innate immunity pathway with canakinumab at a dose of 150 mg every 3 months led to a significantly lower rate of recurrent cardiovascular events than placebo, independent of lipid-level lowering. (Funded by Novartis; CANTOS ClinicalTrials.gov number, NCT01327846.

Global perspective of familial hypercholesterolaemia: a cross-sectional study from the EAS Familial Hypercholesterolaemia Studies Collaboration (FHSC)

Background The European Atherosclerosis Society Familial Hypercholesterolaemia Studies Collaboration (FHSC) global registry provides a platform for the global surveillance of familial hypercholesterolaemia through harmonisation and pooling of multinational data. In this study, we aimed to characterise the adult population with heterozygous familial hypercholesterolaemia and described how it is detected and managed globally. Methods Using FHSC global registry data, we did a cross-sectional assessment of adults (aged 18 years or older) with a clinical or genetic diagnosis of probable or definite heterozygous familial hypercholesterolaemia at the time they were entered into the registries. Data were assessed overall and by WHO regions, sex, and index versus non-index cases. Findings Of the 61 612 individuals in the registry, 42 167 adults (21 999 [53·6%] women) from 56 countries were included in the study. Of these, 31 798 (75·4%) were diagnosed with the Dutch Lipid Clinic Network criteria, and 35 490 (84·2%) were from the WHO region of Europe. Median age of participants at entry in the registry was 46·2 years (IQR 34·3–58·0); median age at diagnosis of familial hypercholesterolaemia was 44·4 years (32·5–56·5), with 40·2% of participants younger than 40 years when diagnosed. Prevalence of cardiovascular risk factors increased progressively with age and varied by WHO region. Prevalence of coronary disease was 17·4% (2·1% for stroke and 5·2% for peripheral artery disease), increasing with concentrations of untreated LDL cholesterol, and was about two times lower in women than in men. Among patients receiving lipid-lowering medications, 16 803 (81·1%) were receiving statins and 3691 (21·2%) were on combination therapy, with greater use of more potent lipid-lowering medication in men than in women. Median LDL cholesterol was 5·43 mmol/L (IQR 4·32–6·72) among patients not taking lipid-lowering medications and 4·23 mmol/L (3·20–5·66) among those taking them. Among patients taking lipid-lowering medications, 2·7% had LDL cholesterol lower than 1·8 mmol/L; the use of combination therapy, particularly with three drugs and with proprotein convertase subtilisin–kexin type 9 inhibitors, was associated with a higher proportion and greater odds of having LDL cholesterol lower than 1·8 mmol/L. Compared with index cases, patients who were non-index cases were younger, with lower LDL cholesterol and lower prevalence of cardiovascular risk factors and cardiovascular diseases (all p<0·001). Interpretation Familial hypercholesterolaemia is diagnosed late. Guideline-recommended LDL cholesterol concentrations are infrequently achieved with single-drug therapy. Cardiovascular risk factors and presence of coronary disease were lower among non-index cases, who were diagnosed earlier. Earlier detection and greater use of combination therapies are required to reduce the global burden of familial hypercholesterolaemia. Funding Pfizer, Amgen, Merck Sharp & Dohme, Sanofi–Aventis, Daiichi Sankyo, and Regeneron

Apolipoprotein B, Residual Cardiovascular Risk After Acute Coronary Syndrome, and Effects of Alirocumab.

Background: Apolipoprotein B (apoB) provides an integrated measure of atherogenic risk. Whether apoB levels and apoB lowering hold incremental predictive information on residual risk after acute coronary syndrome beyond that provided by low-density lipoprotein cholesterol is uncertain. Methods: The ODYSSEY OUTCOMES trial (Evaluation of Cardiovascular Outcomes After an Acute Coronary Syndrome During Treatment With Alirocumab) compared the proprotein convertase subtilisin/kexin type 9 inhibitor alirocumab with placebo in 18 924 patients with recent acute coronary syndrome and elevated atherogenic lipoproteins despite optimized statin therapy. Primary outcome was major adverse cardiovascular events (MACE; coronary heart disease death, nonfatal myocardial infarction, fatal/nonfatal ischemic stroke, hospitalization for unstable angina). Associations between baseline apoB or apoB at 4 months and MACE were assessed in adjusted Cox proportional hazards and propensity score–matched models. Results: Median follow-up was 2.8 years. In proportional hazards analysis in the placebo group, MACE incidence increased across increasing baseline apoB strata (3.2 [95% CI, 2.9–3.6], 4.0 [95% CI, 3.6–4.5], and 5.5 [95% CI, 5.0–6.1] events per 100 patient-years in strata 35–<50, and ≤35 mg/dL, respectively). Compared with propensity score–matched patients from the placebo group, treatment hazard ratios for alirocumab also decreased monotonically across achieved apoB strata. Achieved apoB was predictive of MACE after adjustment for achieved low-density lipoprotein cholesterol or non–high-density lipoprotein cholesterol but not vice versa. Conclusions: In patients with recent acute coronary syndrome and elevated atherogenic lipoproteins, MACE increased across baseline apoB strata. Alirocumab reduced MACE across all strata of baseline apoB, with larger absolute reductions in patients with higher baseline levels. Lower achieved apoB was associated with lower risk of MACE, even after accounting for achieved low-density lipoprotein cholesterol or non–high-density lipoprotein cholesterol, indicating that apoB provides incremental information. Achievement of apoB levels as low as ≤35 mg/dL may reduce lipoprotein-attributable residual risk after acute coronary syndrome. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01663402.gov; Unique identifier: NCT01663402.URL: https://www