31 October 2026
FIR filter quantization
A 63-tap lowpass, 48 kHz sample rate, passband to 4.8 kHz and stopband from 7.2 kHz. The floating-point Parks–McClellan design is compared with two 10-bit versions: round the coefficients, or let firpmq optimize them as integers. Plots are rendered on the dark theme.
- Floating-point
firpm: 0.024 dB passband ripple, stopband peak −56.2 dB.
- Naïve 10-bit rounding: ripple 0.098 dB, stopband peak −38.7 dB.
firpmq at 10 bits: ripple 0.067 dB, stopband peak −46.0 dB — 7.3 dB better rejection than rounding.
31 October 2026
RF amplifier analysis
What a two-port measurement says about a low-noise amplifier, from the first look at the VNA panel through a conjugate-match design. The device is a synthetic 2-port, swept from 1 to 6 GHz, so every figure can be recomputed.
- The 2×2 review of |S11|, |S21|, |S12|, and |S22|, then phase, unwrapped phase, and group delay.
- VSWR, return loss, and insertion loss at each frequency.
- Unconditional stability: Rollett’s K and the µ factors, both greater than 1 across the band.
- Simultaneous conjugate match, Γms and Γml, and maximum available gain.
- Input stability circles and constant-gain circles on the Smith chart.
- Resampling onto a finer frequency grid, a TDR-style step response, and mixed-mode S-parameters for a differential pair.