Link budget vs distance
Desired sideband power at the receiver. Sensitivity shown dashed.
Load states
Reflection coefficients on the Smith chart. Ring = ideal target.
Image rejection
IRR vs state-1 phase and amplitude error. 20 dB contour drawn.
Spectrum at receiver
Carrier leakage and tag harmonics at fc + k·fsw. BLE advertising channels shaded.
Table view
Bistatic coverage
Desired sideband power over tag position. Carrier at origin, receiver at (d0, 0). Contour = sensitivity.
Model
- Bistatic radar equation: Prx = Ptx Gtx Gtag² Grx λ⁴ |ck|² / ((4π)⁴ d1² d2²), minus switch loss twice.
- Tag cycles through N load states with equal dwell. Harmonic k of the stepped Γ(t) has coefficient ck = sin(πk/N)/(πk) · e−jπk/N · Σ Γn e−j2πkn/N.
- Ideal N-phase stepping keeps only k ≡ 1 (mod N). N = 2 is DSB (image at −fsw equals the desired sideband). N ≥ 3 is SSB.
- Carrier leakage is free-space path loss over d0 minus the isolation you enter. No multipath, phase noise or polarization loss.