What spread spectrum communications technique uses a high-speed binary bit stream to shift the phase of an RF carrier?
Why Direct sequence spread spectrum multiplies the data by a much faster pseudorandom binary code (the chipping sequence), and each chip flips the phase of the RF carrier. Because the chip rate is far higher than the data rate, the spectrum is spread over a wide bandwidth; the receiver despreads it by correlating with the identical code. The key phrase in the pool is 'high-speed binary bit stream' shifting carrier phase.
Watch out Frequency hopping is the other common spread spectrum method, but it shifts the carrier frequency in a pseudorandom pattern rather than shifting its phase. Plain binary phase-shift keying does shift phase, but only at the data rate, so it is ordinary narrowband modulation and does not spread the signal.
Two spread spectrum flavors: hopping moves the frequency, direct sequence moves the phase.