Have a look at Hi-Link from China (on Aliexpress).

They offer 50GHz, 10GHz, 24GHz and 60GHz FMCW radar module boards for 10-30€ which are easy to reverse engineer on firmware and PCB level.

A lot of them are CW radars, a few FMCW and they also use the Infineon 60GHz radar chips. Very unusual for Infineon: with all tools and datasheets available without signing a NDA. Down to the register level.

There's an interesting Chinese company around (ICLink with their ICL1122/ICL1112) which offer highly integrated radar ICs. They can spit out raw ADC measurements of their downmixed baseband using Quad SPI at 20 or 40MHz when switching on their debug mode. Price range: ~10€. But datasheets are difficult to find. Example board: LD2410S.

The analog ones are easy to play with. You just need a DAC to drive their VCO and then can sample the I/Q pins with an ADC. That how a lot of the 24GHz modules (like the LD1125H) work.

> The analog ones are easy to play with. You just need a DAC to drive their VCO and then can sample the I/Q pins with an ADC

Do you have any reference or notes on how to access the IQ pins on one of these devices (ideally one of the FMCW ones)? I've been wanting to play around with one of these 24 GHz or 60 GHz units for coherent radar but it seems like most of the boards only report on distances over serial links. If there's an easy way to tap into the analog IF signal after down conversion I'd love to see how to do that!