S-band / L-band BPM Electronics

Non-intercepting beam position measurement

Optimal for S-band /L-band





2.856 GHz and 2.999 GHz


Based on the pioneering work of Robert E. Shafer at Los Alamos Laboratory, the Log-Ratio BPM derives beam position from logarithm of the ratio of opposite pickup signals: Log(A/B).
Position measured by this method is more linear, over a wider range, than difference-over-sum.


Signal processing

Signals from the pickups are stretched to produce bursts. This is essential to measure the single pass of a bunch. Four parallel logarithmic amplifiers detect the burst envelopes.
Amplifiers’ response is log of amplitude. Logs of opposite pickups are subtracted.
If pickups are rotated, axes are translated to obtain X and Y positions. The process is all-analog, wideband.


Front-end Filter / Amplifier FEFA

One Front-end Filter / Amplifier is required for every BPM pickup electrode.
It is tuned to the beam RF or an harmonic and powered from the S–BPM module via the coaxial cable linking them together.
S-BPM FEFA must be installed close to the BPM pickup block, e.g. 1 meter.












  • The S-band / L-band Beam Position Monitor (S-BPM) is an electronics module for fast analog processing of beam pickups signals.
  • Single-pass bunch and macropulses can be measured thanks to parallel processing of inputs.
  • Macropulses and single bunches up to 2MHz repetition rate can be measured individually. X and Y coordinates are memorized until the next macropulse or bunch.
  • CW beam can be measured continuously. X and Y coordinates are available permanently. Beam position motions up to 5MHz can be observed.
  • X and Y outputs are strong analog ±2V signals.
  • S-band / L-band BPM is compatible with other Bergoz’ BPM. They can be plugged in the same chassis.
  • Precise phase matching of input signals is not required.

Beam intensity range



All filter frequencies are made to order


2 standard frequencies: 2.856GHz and 2.999GHz

Output frequency

<5MHz rep rate: individual position is measured
>5MHz rep rate: average position is measured with 5MHz bandwidth


X and Y: -2V…0...+2V, 40mA max
Sum of logs: 0...+2V, 40mA max

X and Y gain

1.5V = ½ of aperture radius for orthogonal pickups
1.0V = ½ of aperture radius for rotated pickups


array(5) { [0]=> int(1) [1]=> int(2) [2]=> int(3) [3]=> int(4) [4]=> int(5) }