CMOS RF Transmitter Using Pulsewidth Modulation for Wireless Smart Sensors

Abstract

This paper presents the radio frequency (RF) transmitter using pulsewidth modulation (PWM) method. The proposed transmitter can perform with lower power consumption compared to other RF transmitters using a conventional ring oscillator because the proposed voltage-controlled oscillator (VCO) is operated by ON-/ OFF-time of the PWM signal. Moreover, the proposed VCO with a metal-oxide semiconductor switch can reduce the power consumption significantly due to the reduction of idle current loss. The power dissipation of the transmitter is measured as 0.75 mW at a carrier of 315 MHz. The transmission of the modulated signal is performed by the on-chip antenna with bond-wire inductor. The on-chip antenna has gain of −34.33 dBi. The radiated power is measured as −32.3 dBm at a distance of 10 cm between the receiver and the transmitter.Index Terms-Bond-wire inductor, pulsewidth modulation (PWM), radio frequency (RF), transmitter.

Power‐efficient burst‐mode RF transmitter based on reference‐adaptive multilevel pulse‐width modulation

“…Also, for the reference waveforms, we have: where is a period of ref i ( t ) and f PWM = 1/ T PWM . Figure shows the common structure used to implement ( M + 1)‐level AMPWM transmitter . The coding efficiency of this transmitter for constant envelope RF input with magnitude of a ∈ [0,1] is derived as: …”

“…Figure 4 shows the common structure used to implement (M + 1)level AMPWM transmitter. 18,30 The coding efficiency of this transmitter for constant envelope RF input with magnitude of a ∈ [0,1] is derived as 32 : Figure 5 plots η c versus a, for the AMPWM example of Figure 3. Based on (5), it can be shown there are 3 (=M − 1) points in [0,1], where η c reaches unity (100%).…”

“…The S vector could be chosen to avoid such repetitions. Hence, the number of unity points for the proposed N-state M-path RAMPWM modulator can reach to the number of unique solutions for (18), which is (M + N) ! /M !…”

“…In recent years, the concept of burst‐mode operation has been widely addressed as a promising approach toward highly efficient RF transmitters . In a conventional carrier amplitude‐burst transmitter, the RF magnitude is converted into a 2‐level square wave with variable pulse‐width.…”

“…In recent years, the concept of burst-mode operation has been widely addressed as a promising approach toward highly efficient RF transmitters. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] In a conventional carrier amplitude-burst transmitter, the RF magnitude is converted into a 2-level square wave with variable pulse-width. Two common techniques to encode the magnitude into a pulse-width are delta-sigma and pulse-width modulations which the latter is the focus of this paper.…”