Controlling systematics in ground-based CMB surveys with partial boresight rotation

ABSTRACT Future CMB experiments will require exquisite control of systematics in order to constrain the B-mode polarization power spectrum. One class of systematics that requires careful study is instrumental systematics. The potential impact of such systematics is most readily understood by considering analysis pipelines based on pair differencing. In this case, any differential gain, pointing or beam ellipticity between the two detectors in a pair can result in intensity leakage into the B-mode spectrum, which needs to be controlled to a high precision due to the much greater magnitude of the total intensity signal as compared to the B-mode signal. One well-known way to suppress such systematics is through careful design of the scan-strategy, in particular making use of any capability to rotate the instrument about its pointing (boresight) direction. Here, we show that the combination of specific choices of such partial boresight rotation angles with redundancies present in the scan strategy is a powerful approach for suppressing systematic effects. This mitigation can be performed in analysis in advance of map-making and, in contrast to other approaches (e.g. deprojection or filtering), results in no signal loss. We demonstrate our approach explicitly with time ordered data simulations relevant to next-generation ground-based CMB experiments, using deep and wide scan strategies appropriate for experiments based in Chile. These simulations show a reduction of multiple orders of magnitude in the spurious B-mode signal arising from differential gain and differential pointing systematics.

Analysis and design of a high-gain 100–180-GHz differential power amplifier in 130 nm SiGe BiCMOS

This paper presents the design and measurement results of a high-gain D-band broadband power amplifier (PA) implemented in a 130 nm SiGe BiCMOS technology. The topology of the PA is based on four differential cascode stages with interstage matching networks. A detailed analysis of the frequency behavior of the transimpedance-gain of the common-base stage of the cascode is presented by means of small-signal equivalent circuits, when the proposed four-reactance wideband matching network is used for output matching to the subsequent stage. The effect of the size of the active devices, in achieving a desired gain, bandwidth, and output power, is investigated. The fabricated D-band amplifier is characterized on-wafer demonstrating a peak differential gain and output power of about 25 dB and 11 dBm, respectively, while utilizing a DC power of 262 mW from a 2.7 V supply. The 3-dB small-signal bandwidth of the PA spans from 100 to 180 GHz (limited by the measurement setup), making it the first SiGe-based PA to cover the entire D-band frequency range. The PA achieves a state-of-the-art differential gain-bandwidth product of around 1.4 THz and the highest GBW/PDCratio of 5.2 GHz/mW among all D-Band Si-based PAs.

CDBA based current instrumentation amplifier

This paper presents a novel method to realize a current mode instrumentation amplifier (CMIA) through CDBA (Current difference Buffered Amplifier). It employs two CDBAs and two resistors to obtain desired functionality. Further, it does not require any resistor matching. The gain can be set according to the resistor values. It offers high differential gain and a bandwidth, which is independent of gain. The working of the circuit is verified through PSPICE simulations using CFOA IC based CDBA realization.

Context cue-dependent saccadic adaptation in rhesus macaques cannot be elicited using color

When the head does not move, rapid movements of the eyes called saccades are used to redirect the line of sight. Saccades are defined by a series of metrical and kinematic (evolution of a movement as a function of time) relationships. For example, the amplitude of a saccade made from one visual target to another is roughly 90% of the distance between the initial fixation point (T0) and the peripheral target (T1). However, this stereotypical relationship between saccade amplitude and initial retinal error (T1-T0) may be altered, either increased or decreased, by surreptitiously displacing a visual target during an ongoing saccade. This form of motor learning (called saccadic adaptation) has been described in both humans and monkeys. Recent experiments in humans and monkeys have suggested that internal (proprioceptive) and external (target shape, color, and/or motion) cues may be used to produce context-dependent adaptation. We tested the hypothesis that an external contextual cue (target color) could be used to evoke differential gain (actual saccade/initial retinal error) states in rhesus monkeys. We did not observe differential gain states correlated with target color regardless of whether targets were displaced along the same vector as the primary saccade or perpendicular to it. Furthermore, this observation held true regardless of whether adaptation trials using various colors and intrasaccade target displacements were randomly intermixed or presented in short or long blocks of trials. These results are consistent with hypotheses that state that color cannot be used as a contextual cue and are interpreted in light of previous studies of saccadic adaptation in both humans and monkeys.