A 2.4-GHz Quadrature Local Oscillator Buffer Insensitive to Frequency-Dependent Loads for Bluetooth Low Energy Applications

In this letter, a 2.4-GHz quadrature local oscillator (LO) buffer insensitive to frequency-dependent loads is presented for Bluetooth low energy (BLE) applications. An LC tank is used as a load in the proposed buffer to provide a sufficient voltage gain and large voltage swing at the operating frequencies of BLE. Furthermore, the effect of the frequency-dependent impedance of the LC tank on the gain and phase mismatches is reduced by adding compensating transistors. The proposed buffer can provide accurate quadrature signals without additional circuitry in the LO path, minimizing the current consumption of the receiver. It is implemented in 65-nm CMOS technology. It achieved a voltage gain of 5.6 dB, a gain mismatch less than 0.3 dB, a phase mismatch less than 1.1 degrees, and an output P-1dB of 3 dBm. It draws an average current of 3.8 mA from a supply voltage of 0.8 V. The active die area is 0.55 mm(2).