24 GHz Low-Noise Amplifiers using High Q Series-Stub Transmission Lines in 0.18μm CMOS

Single-ended and differential low-noise amplifiers (LNAs), designed in 0.18 μm CMOS for operation at 24 GHz, are introduced in this paper. Novel, high-Q series-stub transmission lines (SSTLs) are used in the matching networks of both LNAs. This SSTL structure shows a notable Q factor improvement over the commonly used spiral inductor, which helps to minimize the losses and noise produced in the LNA matching networks, making these topologies suitable for sensitive receiver front ends. The single-ended amplifier uses two cascade stages to help improve gain and reverse isolation when compared to common source stages. Results show that the cascade LNA is able to produce an excellent compromise between ease of design, gain and noise. After optimizing transistor sizes to produce minimum noise, the single-ended amplifier produces a simulated noise figure of only 4.9 dB and a gain of 17.4 dB. The differential LNA uses two capacitive neutralized stages to improve reverse isolation. Chip production has been delayed by the foundry, but simulated results of the differential LNA show an excellent noise figure of 4.2 and a gain of 12.3 dB