Can AD8285 be used in digital beamforming automotive FMCW radar ? Normally one would need to sample all inputs of ADC at the same time.
The acquired waveforms of sequential channels will be predictably offset from each other in time. Each channel would be one clock period behind the next. To the extent that your algorithm can handle this adjustment, you may use this part for beam forming.
We used 4 channels of AD8285. As datasheet, "Channel A is usually the first converted input", but we found CH-D is the first converted input.
We input the same sine wave to 4 channels. ADC setting is
adc_spi_write ( 0x0C, 0x06 ); // adc output 4 channels A B C D adc_spi_write ( 0xFF, 0x01 ); // sync register
Please find following figure. CH-D is the first converted input obviously.
We are sure CH-A and CH-D are not mixed. So we go on to next test.
Input the same sine wave to CH-A B C and input the difference frequecncy to AUX, ADC setting is
adc_spi_write ( 0x0C, 0x07 ); // adc output 4 channels A B C AUXadc_spi_write ( 0xFF, 0x01 ); // sync register
Please see the test result. Channel A is always the last converted input.
Is there anything wrong? Confused...
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