[hpsdr] Chip could provide at least 50% of the world's population with RADAR.

[Jay Salsburg]

This Chip could provide at least 50% of the world's population with Passive
RADAR.

This new tuner chip, like no other I can find, breaks out all the important
signals of an FM Radio transmission and digitizes them for use in RADAR. The
main drawback of using those cheap RTL-SDR Tuner Dongles is they are only 8
bit in dynamic range, a serious limitation. The Si4777 offer 16 bit
resolution increasing dynamic range by 256 times. High dynamic range
provides high resolution Doppler Velocity and high value False Alarm
filtering.
 
A complete SDR is possible with only 20 discrete components. What interests
me, this new device is a self-contained zero-IF digital tuner, with the big
advantage of high definition digital output. Without getting too technical,
the device may receive a Standard FM Transmission including the entire
spectrum of a HD Station's Digital transmission at high dynamic range or 16
bit resolution, and stream the Station's modulation as a Zero I/Q (ZIF)
signal through an I2S serial interface, making post signal processing much
easier. The Tuner chip does all the heavy lifting eliminating the need for
expensive and cumbersome Analog to Digital conversion. A muti-Tuner RADAR
Receiver may be crafted form a set of these Chips, a very attractive
prospect.


>From the Si4777 DATASheet.

4.9. Digital ZIF I/Q Interface (Si4777 Only) (ZIF - Zero Intermediate
Frequency)
The digital ZIF I/Q output can provide the down converted channelized AM/FM
signal at baseband to a third-party processor for... signal processing. The
Si4777 provide a 500 kHz BW signal... The ZIF I/Q 4-pin interface consists
of two data serial lines containing I and Q data, a bit clock, and a word
frame for each data sample. The interface operates in master mode and
supports five different data formats:

 I2S ZIF
 Left-Justified ZIF
 Right-Justified ZIF
 DSP ZIF
 DSP Left-Justified ZIF

4.9.1. ZIF I/Q Data Formats
In DSP format, the IQFS becomes a pulse with a width of 1 IQCLK period.
There are two options in transferring the digital baseband I/Q data in DSP
format: the MSB of I and Q data can be transferred on the first rising edge
of IQCLK following the IQFS pulse (left-justified DSP format) or on the
second rising edge.
The number of baseband I/Q bits is configured for 16 bits.

Table 14. ZIF I/Q Interface Description

Pin 		Description

IOUT 		16-bit baseband I word
QOUT 		16-bit baseband Q word
IQFS 		Word frame sync for I and Q words
IQCLK 	Bit clock for I and Q data


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