I’ve been fielding quite a few questions lately about polar modulation. Indeed, polar modulators are theoretically more efficient. However, this does not need to be the case. I will highlight (technically, self-promote) a Cartesian scheme that can produce an RF signal as efficiently as a polar modulator—with fewer implementation issues.
Introduction So, we want to break down our continuous-time sigma-delta feedback into two paths: A low-precision tight loop that delivers the first sample to the quantizer A higher-precision loop that goes through a clock delay to minimize “metastability” (indecision)
Introduction Consider our usual continuous-time sigma-delta (CTSD) ADC: x(t) is the analog input and y[n] is the digital output and feedback signal that drives the DAC. H(s) is the loop filter and Q represents the quantizer. One of the main difficulties with continuous-time sigma-delta’s is that when the digital output does not match the analog […]
Introduction The impulse invariant transform (IIT) is a method of taking a continuous-time system H(s) and converting it to a discrete-time system. There are multiple ways of doing this, but the IIT does so with the constraint that the impulse response of the discrete-time system is a sampled version of the impulse response of the […]
Introduction I had been working on a pulse-width-modulation (PWM) design. It was a pseudo-digital implementation, in that the output was clocked by a high-speed clock. The actual switching rate was much lower than this clock. I wanted to simulate this design in Cadence/Spectre by running a transient and then taking an FFT. However, I ran […]
I’ve posted a guest article at Circuit Sage, detailing the derivation of a “Viterbi” over-sampling data converter. I’m quite proud of this one. Go over and check it out.movie Mechanic: Resurrection 2016 streaming FYI: this is also the reason I didn’t post directly to this site this week. I try to do a post per […]
In my prior post, I discussed the use of “chopping” (or pre- and post-mixing) to improve the IM2 of RF/analog circuits. New readers should go back and read that post in order to understand the nomenclature and variable names in this post. Lately, I’ve been considering whether any similar (but different) technique can be used […]
Answers question in I/Q Noise figure, and on how to do stability in Cadence ADE.
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