QPSK Modulators and BPSK Modulators

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.  

QPSK and BPSK modulators use many different types of RF connectors. Bayonet Neil-Concelman (BNC) connectors have a slotted outer conductor and are used in applications to 2 GHz. Threaded Neil-Concelman (TNC) connectors are similar in size to BNC connectors, but feature a threaded coupling nut for applications that require performance to 11 GHz. Miniature coaxial (MCX) connectors provide broadband capability through 6 GHz and are used in applications where weight and physical space are limited. Ultra high frequency (UHF) connectors are designed with non-constant impedance for use in comparatively low voltage and low frequency applications. Subminiature-A (SMA) connectors directly interface the cable dielectric without air gaps. Subminiature-B (SMB) connectors snap into place and are used for frequencies from DC to 4 GHz. Subminiature-P (SMP) connectors are rated to 40 GHz and, depending on detent type, can withstand from 100 to 100,000 interconnect cycles. Other connectors for QPSK and BPSK modulators include MMCX, Mini-UHF, Type F, Type N, 1.6/5.6, and 7-16 connectors. 

There are several mounting styles for QPSK modulators and BPSK modulators. Surface mount technology (SMT) adds components to a printed circuit board (PCB) by soldering component leads or terminals to the top surface of the board. Through hole technology (THT) mounts components by inserting component leads through holes in the board and then soldering the leads in place on the opposite side of the board. Flat pack (FPAK) devices have flat leads and are available in a variety of body sizes and pin counts. Connectorized devices attach with coaxial or other types of connectors. Waveguide assemblies consist of a hollow metallic conductor with a rectangular, elliptical, or cross-section. Some conductors contain solid or gaseous dielectric materials. 

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