Introduction
There will be 20 sampler modules available which will have access to one of two 50MHz bands.
Each sampler module will receive an IF in the range 25MHz through 75MHz. Initially they will pick out either a 5MHz or 10MHz band from the available IF. This is downconverted to quadrature baseband. Following this is a low pass anit-aliasing filter and finally sampling stages. There is a VU style display to indicate the power being sampled. The sampler will only sample when selected by the interface module. The sample rate is also determined in the interface module.
Hardware
(Background information)
Please note that the IF bandpass filters are fixed in a hardware tuned circuit. There will be a choice of filters available in either 5MHz or 10MHz bandwidths covering a range from 25MHz through 75MHz. These simply plug into the sampler module.
In a similar way, the low pass, anti-aliasing filters are fixed at either 2.5MHz or 5MHz.
Programming
Programming the Sampler Module is via the Adlink/Interface board.
There is an 8 bit word available to each sampler board, of which 7 bits have been implemented, as follows:
| Register flag | D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 | |
| -spare- | BANDSW | ATTR3 | ATTR2 | ATTR1 | ATTL3 | ATTL2 | ATTL1 | ||
BANDSW selects between the two available frequency bands as follows:
| BANDSW | Frequency Band | |
| 0 | Band 1 | |
| 1 | Band 2 | |
ATTL(3:1) sets the left hand attenuation, and ATTR(3:1) the right. This is a logical relationship as shown below:
| ATTx3 | ATTx2 | ATTx1 | Attenuation dB | |
| 0 | 0 | 0 | No Attenuation | |
| 0 | 0 | 1 | 1dB | |
| 0 | 1 | 0 | 2dB | |
| 0 | 1 | 1 | 3dB | |
| 1 | 0 | 0 | 4dB | |
| 1 | 0 | 1 | 5dB | |
| 1 | 1 | 0 | 6dB | |
| 1 | 1 | 1 | 7dB | |
The address table relating to each Interface Board/Adlink Card is as follows:
| Address $00 | Presets for Sampler0 | |
| Address $01 | Presets for Sampler1 | |
| Address $02 | Presets for Interface | |
| Address $03 | Presets for Interface | |
| Address $04 | Presets for LO0 | |
| Address $05 | Presets for LO1 | |
The address must be sent to the upper 8 bits of the PB word, and the programmed data to the lower 8 bits of the PB word.
| PB15 | PB14 | PB13 | PB12 | PB11 | PB10 | PB9 | PB8 | PB7 | PB6 | PB5 | PB4 | PB3 | PB2 | PB1 | PB0 |
| A7 | A6 | A5 | A4 | A3 | A2 | A1 | A0 | D7 | D6 | D5 | D4 | D3 | D2 | D1 | D0 |