This paper describes the design and experimental results of a 1.8-V single-chip CMOS MMIC front-end for 2.4-GHz band short-range wireless communications, such as Bluetooth and wireless LANs. The IC consists of fundamental RF building circuits-a power amplifier (PA), a low-noise amplifier (LNA), and a transmit/receive-antenna switch (SW), including almost all on-chip matching elements. The IC was fabricated using a 0.18-m standard bulk CMOS technology which has no extra processing steps to enhance the RF performances. Two new circuit-design techniques are introduced in the IC in order to minimize the insertion loss of the SW and realize a higher gain for the PA and LNA despite the utilization of the standard bulk CMOS technology. The first is the derivation of an optimum gate width of the SW to minimize the insertion loss based on small-signal equivalent circuit analysis. The other is the revelation of the advantages of interdigitated capacitors (IDCs) over conventional polysilicon to polysilicon capacitors and the successful use of the IDCs in the LNA and PA. The IC achieves the following sufficient characteristics for practical wireless terminals at 2.4 GHz and 1.8 V: a 5-dBm transmit power at a 1-dB gain compression, a 19-dB gain, an 18-mA current for the PA, a 1.5-dB insertion loss, more than 24-dB isolation, an 11-dBm power handling capability for the SW, a 7.5-dB gain, a 4.5-dB noise figure, and an 8-mA current for the LNA.

We are approaching an age of IoT, in which sensors and controllers in all types of devices, including smart phones and PCs, are connected together. The strongest candidate for a wireless interface is the Bluetooth Low Energy® (BLE) standard because it is already widely used in smart phones. Many markets, especially for wearable devices like smart watches, demand BLE devices with a small module area and low current consumption. In previous research, solutions to the requirements for BLE have been widely discussed such as using the sliding IF (SIF) architecture in the RX [1,2] and a Class-D amplifier [2] with HD2 calibration [4] in the TX to achieve lower current consumption. The SIF architecture, however, involves RF image blocking violation without exception rule or the use of additional off-chip filters. In the TX, meanwhile, the calibration incurs a weakness in terms of the offset issue. Moreover, there is no approach to achieve "zero" external components for the RF port. In this paper, a BLE transceiver, with a reconfigurable filter, embedded into an on-chip matching network without any external components, is presented.

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