| Description |
C-2C, Split-array switched-capacitor power amplifier (SA-SCPA) are presented toovercome the challenges of simultaneously designing SCPAs with high resolution and high output power. Split-arrays allow a capacitance array to be subdivided with the aid of an attenuation capacitor, CA, to balance the charge between the arrays, regardless of the size of the arrays, or their associated capacitance. This allows a reduction in area and allows for array capacitance to be scaled to usable values for high resolution arrays. C-2C arrays are widely used because of the low ratio of the maximum-to-minimum capacitance, which allows for better capacitor matching, at the expense of sensitivity to parasitic effects. The size of the C-2C array increases linearly with the resolution, thus occupying less area then a binary-weighted array. The sizes of the capacitors are fixed and small, making the switches see approximately the same small capacitive load, thus easing the switch design as well as the layout, since the entire topology is composed of the replicas of a small C-2C block. Based on the SA-SCPA mentioned above, a multiphase interpolating digital power amplifier for TX beamforming is presented. This work consists of four key concepts. First, A 13b, 16-phase split-array multiphase SCPA (SAMP-SCPA) is fabricated, which is not just a power amplifier, but a versatile digital transmitter front-end. SAMP-SCPAs can achieve similar output power and system efficiency to prior art in digital PAs, while offering reduced OOB noise. Second, a fully-digital phased-array system that comprises 4 chains implemented as SAMP-SCPAs is fabricated, which can significantly improve the effective SNR at the output, when configured as a beamformer. Third, the phased-array implemented in SAMP-SCPA consists of a phase and amplitude decoder logic as a phase shifter and amplitude weight to precisely control the direction angle when steering a radio frequency beam, in a smaller area with lower losses than conventional digital phases-arrays, which can simply the whole circuit and reduce the power. Finally, the digital phased-array system can achieve high resolution when electronically steering the beam. Any necessary phase/amplitude shift can be added to the amplitude and phase modulation. A 4-element digital modulated multiphase phased-array TX in 65nm CMOS is designed and fabricated to demonstrate the prototype, which to my knowledge is the first of its kind. It can achieve < 1° phase resolution and <1 dB gain error with the 9-bit SAMP-SCPA while obtaining 24.4 dBm peak output power and 24% peak SE with no digital predistortion (DPD). |
