Active-only variable-gain low-pass filter for dual-mode multiphase sinusoidal oscillator application

Abstract

Abstract:This research presents an active-only low-pass (LP) filter whose pole frequency and gain are independently tunable by means of bias current manipulation. The realization of the proposed LP filter required one operational amplifier, two operational transconductance amplifiers, and two MOS transistors. The multiphase sinusoidal oscillator (MSO) was subsequently realized by cascading n LP filters ( n = 3) and loop-backing the output of the last LP filter to the input of the first LP filter. Simulations were carried out and the results revealed that the MSO could simultaneously achieve low impedance voltage and high impedance current outputs without the circuit topology alteration. The frequency of oscillation and the condition of oscillation could also be electronically tuned without disturbing each other.Furthermore, the sinusoidal signal of the MSO exhibited relatively low total harmonic distortion of about 0.8% at 2.75MHz. To verify, a prototype of the active-only LP-based MSO ( n = 3) was constructed and experiments were performed.The experimental findings were agreeable with the simulation results.

Electronically Tunable Voltage-Mode Multiphase Sinusoidal Oscillator with Low Output Impedance Nodes Employing VD-DIBAs

“…The multiphase sinusoidal oscillator (MSO) is one important type of oscillator, which is useful for various electronic applications in communication systems, control systems, instruments, power electronics, single-sideband generators [1], etc. The MSO is designed by first-order circuits, such as an all-pass filter [2][3][4][5][6], a high-pass filter [7][8], and a low-pass filter [9][10][11][12][13][14][15][16][17][18][19]. To achieve the same magnitude and phase difference of each output sinusoidal waveform, the MSO should be designed from the same sub-circuit without an additional amplifier.…”

“…In the literature, numerous types of multiphase sinusoidal oscillators employing active building blocks have been proposed [2-5, 7-8, 10-19]. The proposed multiphase sinusoidal oscillators in [2][3][4][5] are based on the first-order all-pass (AP) filter, the high-pass (HP) filter [7][8], and the low-pass (LP) filter [10][11][12][13][14][15][16][17][18][19]. Each phase of the proposed sinusoidal oscillators in [3,[7][8]13] requires two active elements.…”

“…The proposed multiphase sinusoidal oscillators in [2][3][4][5] are based on the first-order all-pass (AP) filter, the high-pass (HP) filter [7][8], and the low-pass (LP) filter [10][11][12][13][14][15][16][17][18][19]. Each phase of the proposed sinusoidal oscillators in [3,[7][8]13] requires two active elements. The control of the frequency and condition are not independently controlled [10][11][12][13][15][16][17].…”

“…Each phase of the proposed sinusoidal oscillators in [3,[7][8]13] requires two active elements. The control of the frequency and condition are not independently controlled [10][11][12][13][15][16][17]. Some such MSOs require a floating capacitor, which is undesirable for integrated circuit implementation [3-4, 10, 12-13].…”