Quadrature phase shift keying (QPSK) modulator
Quadrature phase shift keying (QPSK) and binary phase shift keying (BPSK) modulators are used to change the amplitude, frequency, and/or phase of a carrier signal in order to transmit information. QPSK devices modulate input signals by 0°, 90°, 180°, and 270° phase shifts. BPSK devices modulate input signals by 0° and 180° phase shifts. Both QPSK modulators and BPSK modulators are used in conjunction with demodulators that extract information from the modulated, transmitted signal. Some QPSK modulators and BPSK modulators include an integral dielectric resonator oscillator. Others are suitable for military or wireless applications. QPSK modulators and BPSK modulators with root raised cosine (RRC) and Butterworth filters are also available.
Performance specifications for QPSK modulators and BPSK modulators include input carrier frequency, insertion loss, amplitude unbalance, phase unbalance, and voltage standing wave ratio. Insertion loss is the total RF power transmission loss through the device. Amplitude unbalance is the different in power between the I output signal and the Q output signal. Phase unbalance is the deviation from 90° of the phase angle difference of the I and Q output signals. Voltage standing wave ratio (VSWR) is a unitless ratio ranging from 1 to infinity that expresses the amount of reflected energy at the input of the device. A value of 1 indicates that all of the energy passes through. Any other value indicates that a portion of the energy is reflected. Other performance specifications for QPSK modulators and BPSK modulators s include frequency range, return loss, and reflected power.