A non-magnetic material frequency selective limiter circuit has first and second resonators and a non-linear coupling component. The first resonator oscillates at a fundamental frequency. The second resonator oscillates at one half of the fundamental frequency. The non-linear coupling component non-linearly and parametrically couples the first resonator and the second resonator. The first resonator, second resonator and the non-linear coupling component are arranged so as to reduce the amplitude of an output signal for an input signal of frequency when an input signal amplitude is above a voltage threshold value, by converting part of the input signal to a signal at the frequency /2. The first resonator, second resonator and the non-linear coupling component are formed of non-magnetic materials.

A non-magnetic material frequency selective limiter circuit has first and second resonators and a non-linear coupling component. The first resonator oscillates at a fundamental frequency. The second resonator oscillates at one half of the fundamental frequency. The non-linear coupling component non-linearly and parametrically couples the first resonator and the second resonator. The first resonator, second resonator and the non-linear coupling component are arranged so as to reduce the amplitude of an output signal for an input signal of frequency when an input signal amplitude is above a voltage threshold value, by converting part of the input signal to a signal at the frequency /2. The first resonator, second resonator and the non-linear coupling component are formed of non-magnetic materials.

A resistive attenuator and a method for improving linearity of the resistive attenuator are provided. The resistive attenuator includes a first transistor, an attenuation circuit and a compensation circuit, wherein both the first transistor and the attenuation circuit are coupled between an input terminal and an output terminal of the resistive attenuator, and the compensation circuit is coupled to the first transistor. The first transistor is configured to provide a first signal path between the input terminal and the output terminal. The attenuation circuit is configured to provide a second signal path between the input terminal and the output terminal, wherein signal attenuation of the second signal path is greater than signal attenuation of the first signal path. The compensation circuit is configured to compensate nonlinear distortion caused by the first transistor.

There is provided a phase shifter circuit of an optical encoder. The phase shifter circuit receives a first signal, a second signal, a third signal and a fourth signal sequentially having a 90-degree phase shift, and includes a first cascaded resistor string, a second cascaded resistor string, a third cascaded resistor string and a fourth cascaded resistor string. The first, second, third and fourth cascaded resistor strings respectively delay the first, third, second and fourth signals by selecting a switch connected at a tap-out node of the first, second, third and fourth cascaded resistor strings to correct phase deviations between incremental signals and an index signal and/or between incremental signals.