Linear ultra-broadband NPN-only analog correlator at 33 Gbps in 130 nm SiGe BiCMOS technology

An ultra-broadband analog correlator consisting of a four-quadrant multiplier and an ultra-fast resettable integrator using only NPN transistors was designed, fabricated, and measured. For the integrator, a cross-coupled transistor pair is used as a negative resistance generator. A novel ultra-fast reset circuit is implemented which allows to reset the integrator within very short time of 120 ps. The chip was fabricated using 130 nm SiGe BiCMOS technology with fT of 250 GHz and f
_max
of 300 GHz. In the measurements carried out on printed circuit board, the correlator operated without noticeable performance degradation with inputs up to 33 Gbps which correspond to a bandwidth of more than 24 GHz. The correlator exhibits high linearity with output P1dB of more than 9.9 dBm (700 mV
_diff
) for both inputs. It dissipates 122.5 mW for the core circuit excluding the 50 Ω output driver. To the knowledge of the authors, the circuit represents the fastest analog correlator published so far. It can be used for spread spectrum communication, radar signal processing, and measurement applications.