Abstract
This paper presents an ultra-low-power receiver based on the injection-locked oscillator (ILO), which is compatible with multiple modulation schemes such as on-off keying (OOK), binary frequency-shift keying (BFSK), and differential binary phase-shift keying (DBPSK). The receiver has been fabricated in 0.18- $\mu \text{m}$ CMOS technology and operates in the ISM band of 2.4 GHz. A simple envelope detection can be used even for the demodulation of BFSK and DBPSK signals due to the conversion capability of the ILO from the frequency and phase to the amplitude. In the proposed receiver, a $Q$ -enhanced single-ended-to-differential amplifier is employed to provide high-gain amplification as well as narrow band-pass filtering, which improves the sensitivity and selectivity of the receiver. In addition, a gain-control loop is formed in the receiver to maintain constant lock range and hence frequency-to-amplitude conversion ratio for the varying power of the BFSK-modulated receiver input signal. The receiver achieves the sensitivity of −87, −85, and −82 dBm for the OOK, BFSK, and DBPSK signals respectively at the data rate of 50 kb/s and the BER lower than 0.1% while consuming the power of $324~\mu \text{W}$ in total.
Highlights
As a variety of services and applications based on the internet of things (IoT) have been widely developed, the demands on ultra-low-power wireless techniques for data transmission and reception have grown rapidly
We propose a low-power receiver design based on injection-locked oscillator (ILO), which can support multiple modulation schemes: on-off keying (OOK), binary frequency-shift keying (FSK) (BFSK), and differential binary phase-shift keying (PSK) (DBPSK)
Two of them are the on-chip inductors used for the Pre-AMP and ILO, and the other is the off-chip inductor with high Q used for the single-ended-to-differential amplifier (SDA)
Summary
As a variety of services and applications based on the internet of things (IoT) have been widely developed, the demands on ultra-low-power wireless techniques for data transmission and reception have grown rapidly. The amplitudemodulated signal generated by the ILO is down-converted by the envelope detector as in the conventional low-power OOK receiver This structure, faces significant challenges in that the amplitude of the signal injected to the ILO should be sufficiently large for guaranteeing proper injectionlocking operation and kept relatively constant for maintaining consistent frequency-to-amplitude conversion ratio. The external MCU generates a gain control signal for the SDA based on the output amplitude of the baseband amplifier (BB AMP), which is measured by the peak detector Through this closed-loop control, the magnitude of the RF signal injected to the ILO can be kept fairly constant, and a significant change in the frequency-toamplitude conversion ratio of the ILO can be prohibited when the BFSK signal is received. Note that the output of the ED behaves like an RZ signal, which requires a conversion to the NRZ signal for input data recovery [11]
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