New beam position monitor system design for the APS injector. Page: 4 of 8
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The receiver is partitioned as shown in Figure 1. There is a front-end board, four
log amplifier boards, and a control and regulation board for each receiver. The boards
are housed in an EMI-shielded aluminum case. The receivers are installed in a 19-
inch-wide, 4-U height card crate where up to eight receivers can be installed.
Front-End and Self Test Board
The rf front-end board provides the gain and self-test capabilities for the system.
The four signals from the input bandpass filters are sampled via 15-dB directional
couplers, which are printed on the circuit board. This provides the ability to trouble-
shoot the system without disconnecting any cables. The directional couplers also serve
as feeds for the self-test oscillators. In the self-test mode the coupler is switched from
a 50-Q termination to a voltage-controlled oscillator. The oscillator drives a two-way
equal power divider that is also printed on the circuit board and provides an equal
input to one plane of the BPM. This same layout is duplicated for each plane. The
board employs a selectable gain stage to shift the operating range by 20 dB. Presently
we are using a low-noise Stanford Microdevices SGA-3586 cascadeable gain block
with a noise figure of 2.5 dB. There are other amplifiers in this series with different
gain and noise parameters that could be implemented in the future. This amplification
will shift the input operating range while maintaining the same system gain (Gsystem).
This feature will be used in some applications and has the effect of extending the
The front-end and self-test rf board was designed using microstrip transmission
lines and components laid out on Rogers R03006 microwave board materials. The
impedance was calculated using Eq. (4) and was optimized in the lab . The
dielectric constant of the ceramic PTFE composite material is 6.15 and the loss
tangent is 0.0025 @ 10 GHz. One of the design goals was keeping the rf board
construction process as simple as possible by avoiding bonding substrates. This
equates to a two-layer board with a thickness of 0.025 inch to insure the trace width of
0.036 inch for 50-2 lines. The boards are designed to be drop-in replacements for
352- or 2856-MHz applications.
377 8h 1 W 2 11 4]
Z& ~e x [In - + - - -- In -+- In - (4)
2;z ,Y+ 1) W 8 2h 2 E, +1 2 E, ; '
where Z=microstrip impedance, E, =substrate dielectric constant, h=substrate
thickness, and W=microstrip width.
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Lill, R.; Singh, O. & Arnold, N. New beam position monitor system design for the APS injector., article, May 15, 2002; Illinois. (digital.library.unt.edu/ark:/67531/metadc741928/m1/4/: accessed August 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.