MIT Haystack Observatory has been at the forefront of VLBI technology development since the birth of the technique many decades ago. The broadband signal chain of the new KPGO radio telescope is a major contribution that results from this development. The KPGO signal chain builds on the successful designs already implemented at the GGAO 12-m and the Westford 18-m telescopes. This two-element prototype of a VGOS baseline is the only fully functional broadband VGOS system completed to date.

The signal chain encompasses a series of novel VGOS components along which the incoming radio signal propagates once it enters the telescope, from the delicate cryogenically-cooled feed and receiver up in the antenna front end, through sensitive coaxial and fiber optic cables that connect the front and back ends, to advanced sampling and recording subsystems down in the back end. If the fully-steerable VGOS antenna structure can be viewed as a mechanical "listening ear," the signal chain is its electronics "beating heart."

The VGOS signal is broadband because it spans a bandwidth of over 10 GHz, with microwave frequencies ranging between approximately 2 GHz (15-cm wavelength) and 14 GHz (2-cm wavelength). The signal, which is analog in the front end, is transmitted via cables to the back end, where carefully selected sections of the entire broadband are digitized. To meet the stringent accuracy requirements of VGOS, the signal chain also incorporates a highly sophisticated calibration system that tracks the various delays introduced by each component along the entire broadband signal path. Interferometry is ultimately realized when the signals recorded at KPGO and other broadband VGOS-compliant systems, independently but simultaneously, are brought together for complex correlation and post-processing, and geodetic analysis and beyond.