BIMA Correlation Modes


In cross correlation mode, the number of channels is as given in the diagram below; in auto correlation mode, the number of channels is double that shown. A PostScript version of this figure is available.

The figure that follows describes the window layout in one sideband of the first LO. These same windows are repeated in both sidebands of the first LO. The second LO is fixed. The third LOs are generally identified by the names CORF1, CORF2, ... in the figure below.

The windows marked with bw1, bw2, bw3, and bw4 in the figure below may have the bandwidth values listed in the following table. The number of channels available in a given window depends on the degree of multiplexing; the multiplexing is parameterized here by the variable m. See the figure of correlator modes for how the number of channels in some windows depends on m.

                bw(MHz)      m
                --------------
                6.25         1
                12.5         1
                25           1
                50           2
                100          4

Those windows with the CORF (third LO) shown centered in a fixed 200 MHz bandwidth (e.g. mode 5, CORF2) utilize both the upper and lower sidebands of that CORF. The user is restricted to using the 100 MHz immediately above and below that CORF. However, the data for the two CORF sidebands are written to two separate 100 MHz windows. Note that the number of windows for a given mode is therefore the same as the mode number. This point also applies in mode 8 to CORF1 where the bandwidth of the lower side band of CORF1 is allowed to vary.


Mode 1 bw1 ---------------------------------------------------------------| | 1024/m ch | | | CORF1 Mode 2 bw1 bw2 -------------------------------| |---------------------------- | 512/m ch | | 512/m ch | | | | | CORF1 CORF2 Mode 3 bw1 bw2 bw4 -------------------------------| |------------ |------------ | 512/m ch | | 256/m ch | | 256/m ch | | | | | | | CORF1 CORF2 CORF4 Mode 4 bw1 bw2 bw3 bw4 ------------| |------------ ------------| |------------ | 256/m ch | | 256/m ch | | 256/m ch | | 256/m ch | | | | | | | | | CORF1 CORF2 CORF3 CORF4 Mode 5 bw1 200 MHz 200 MHz -------------------------------| ----|---- ----|---- | 512/m ch | | 64 ch | | 64 ch | | | | | | | CORF1 CORF2 CORF4 Mode 6 bw1 200 MHz bw3 200 MHz ------------| ----|---- ------------| ----|---- | 256/m ch | | 64 ch | | 256/m ch | | 64 ch | | | | | | | | | CORF1 CORF2 CORF3 CORF4 Mode 7 25 MHz 200 MHz 200 MHz 200 MHz ------------| ----|---- ----|---- ----|---- | 256 ch | | 64 ch | | 64 ch | | 64 ch | | | | | | | | | CORF1 CORF2 CORF3 CORF4 Mode 8 bw1** 100 MHz 200 MHz 200 MHz 200 MHz ------------|------- ----|---- ----|---- ----|---- | 128/m ch 32 ch | | 64 ch | | 64 ch | | 64 ch | | | | | | | | | CORF1 CORF2 CORF3 CORF4 note: ** In mode 8, bw1 is restricted to 25, 50, or 100 MHz.

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Page last modified: Monday, 09-Nov-1998 09:26:55 EST.