VCO in Radar Transceiver

[gk1994]

Hi All,

I was looking at several papers of radar transceiver that operates at 77GHz to 88 GHz focusing on the VCO and Chirp PLL architecture.

So if we want the output of the VCO to be 77GHz to 88 GHz, all the papers for radar transceivers use VCO with a multiplier to generate frequencies in the range of 77GHz to 88 GHz. (Say 20 * 4 or 38*2 )

What would be the technical reason to use multipliers? why can't we just have an architecture of the VCO that operates at 77 GHz?

Please let me know

 

[davenn]

What would be the technical reason to use multipliers? why can't we just have an architecture of the VCO that operates at 77 GHz?

because with today's tech, it's almost impossible

 

[hevans1944]

why can't we just have an architecture of the VCO that operates at 77 GHz?

Follow the money. Electronics design is always a trade-off between cost and performance. The only semiconductors that I am aware of that will operate at 70
GHz are gallium arsenide, and then probably only as oscillators embedded in an integrated circuit. Rotsa ruck designing a GaAs-based IC with a 70GHz oscillator and PLL control. Might want to carefully check to see if that hasn't already been done for a car manufacturer. You need a Doppler ranging capabiity to determine closure rate for anti-collision radar. Pulsed radar that is chirped to effectively narrow the pulse "width" for better range resolution is another consideration to look at when you go off to design a VCO architecture that operates at 77 GHz. Might as well build a high-performance computing engine into that chip while you are at it, one that can be used to automatically apply braking or initiate air bag deployment if an imminent collision is detected.