Abstract
This paper presents a fast-switching Transmit/Receive (T/R) Single-Pole-Double-Throw (SPDT) Radio Frequency (RF) switch. Thorough analyses have been conducted to choose the optimum number of stacks, transistor sizes, gate and body voltages, to satisfy the required specifications. This switch applies six stacks of series and shunt transistors as big as 3.9 mm/160 nm and 0.75 mm/160 nm, respectively. A negative charge pump and a voltage booster generate the negative and boosted control voltages to improve the harmonics and to keep Inter-Modulation Distortion (IMD) performance of the switch over 100 dBc. A Low Drop-Out (LDO) regulator limits the boosted voltage in Absolute Maximum Rating (AMR) conditions and improves the switch performance for Process, Voltage and Temperature (PVT) variations. To reduce the size, a dense custom-made capacitor consisting of different types of capacitors has been presented where they have been placed over each other in layout considering the Design Rule Checks (DRC) and applied in negative charge pump, voltage booster and LDO. This switch has been fabricated and tested in a 90 nm Silicon-on-Insulator (SOI) process. The second and third IMD for all specified blockers remain over 100 dBc and the switching time as fast as 150 ns has been achieved. The Insertion Loss (IL) and isolation at 2.7 GHz are −0.17 dB and −33 dB, respectively. This design consumes 145 uA from supply voltage range of 1.65 V to 1.95 V and occupies 440 × 472 µm2 of die area.
Highlights
The rapid growth of wireless communication standards at different frequency bands such as Global Systems for Mobile communications (GSM), Code-Division Multiple Access (CDMA) and the expansion of other non-cellular wireless services, such as WiFi, Bluetooth, and Global Positioning System (GPS), place the Radio Frequency (RF) switches in an increasingly vital role in the RF front-end module for mobile terminals [1].In Time-Division Duplexing (TDD) systems, when the signal transmission and reception happens at different time slots, a circulator is employed in remote antenna unit to provide the isolation between the Tx and Rx connected to the same antenna
In order to reduce the area of analog parts, which is dominated by capacitors in Bandgap Reference (BGR), Negative Charge Pump (NCP), etc., a custom-made capacitor has been made
This paper presented a fast-switching T/R SPDT RF switch
Summary
The rapid growth of wireless communication standards at different frequency bands such as Global Systems for Mobile communications (GSM), Code-Division Multiple Access (CDMA) and the expansion of other non-cellular wireless services, such as WiFi, Bluetooth, and Global Positioning System (GPS), place the Radio Frequency (RF) switches in an increasingly vital role in the RF front-end module for mobile terminals [1]. Inter-Modulation Distortion (IMD) is another important parameter in RF switch design, but it is usually not being reported in papers. Silicon-on-Insulator (SOI) has become dominant in the design of RF switches [12,13,14,15,16,17,18,19,20,21] recently, due to its capabilities to operate and fabricate at a low supply voltage, as well as to integrate Complementary Metal–Oxide–Semiconductor (CMOS). We discuss a low power, fast switching time Single Pole Double Throw (SPDT) RF switch design in a thick SOI process. We discuss and analyze the switch core design considerations such as size of transistors, number of stacks and gate/body control voltages thoroughly.
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