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.
Category Archives: Analog Professional
Polar vs Cartesian RF Modulator Efficiency
Posted in Analog Professional Tagged cartesian, mixer, modulator, polar, RF, switching Leave a comment
Impulse Invariant Transform
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 [...]
Non-Radix-2 FFT in Cadence/Ocean/Skill/Spectre | Using Cadence IPC to talk to Matlab (or anything else)
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 [...]
The Viterbi Sigma-Delta (at CircuitSage)
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. FYI: this is also the reason I didn’t post directly to this site this week. I try to do a post per week, but the article [...]
Posted in Analog Professional Tagged CircuitSage, data converter, Delta Sigma, oversampling, sigma delta, Viterbi Leave a comment
Asymmetric chopping for improved IM3 | A dead-end research topic?
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 [...]
Reader Round-Up (vol 1)
Answers question in I/Q Noise figure, and on how to do stability in Cadence ADE.
Posted in Analog Professional Tagged cadence, downconverter, noise figure, quadrature, spectre, stability Leave a comment
Chopping to alleviate IM2,
IM2 Consider the fully differential amplifier shown below:
Posted in Analog Professional Tagged chopping, IM2, IP2, matching, mixer, pseudonoise, spread spectrum 3 Comments