Narrow-band filter with linearly adjustable center frequency

Abstract

The invention discloses a narrow-band filter with the linearly adjustable center frequency. The narrow-band filter with the linearly adjustable center frequency mainly solves the problems that an existing narrow-band filter is small in dynamic input range, and the center frequency can not be linearly adjusted. The narrow-band filter with the linearly adjustable center frequency comprises a high-pass capacitor (1), a low-pass capacitor (2), a resistive feedback network (3) and two bipolar transconductance amplifiers (4 and 5), wherein the positive phase input end of the first amplifier is connected with the output end of the high-pass capacitor, the output end of the first amplifier is connected with the positive end of the low-pass capacitor, and the first amplifier is fed back to the negative phase input end through the resistive feedback network, so that a negative voltage feedback structure is formed; the negative input end of the second amplifier is connected with the output end of the first amplifier, the positive phase input end of the second amplifier is grounded, and the output end of the second amplifier is connected with the positive phase input end of the first amplifier, so that a negative current feedback structure is formed. According to the narrow-band filter with the linearly adjustable center frequency, the dynamic input range of the filter is enlarged through the two bipolar transconductance amplifiers, a linearly adjustable transconductance value is provided for the filter, the center frequency can be linearly adjusted, and the narrow-band filter can be used for infrared receiver circuits.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits, in particular to a narrow-band filter, which can be used in an infrared receiver. Background technique [0002] Infrared remote control is widely used in household appliances and car audio-visual navigation systems because of its low cost, high transmission speed, and point-to-point communication interface. The infrared receiver is the most important part of the infrared transmission system, so the performance requirements for the infrared receiving circuit are getting higher and higher. In general, the infrared signal has a long transmission distance in space, and the signal reaching the receiving end is weak, so the infrared receiving chip is easily interfered by the photocurrent generated by ambient light sources, such as sunlight, fluorescent lamps, and incandescent lamps. Therefore, how to effectively suppress various interferences from the external environment to improve the se...

AI Technical Summary

Problems solved by technology

[0007] From the expressions of center frequency and quality factor, it can be seen that there is no connection between these two parameters, so it is easy to achieve quadrature adjustable; but by figure 2 It can also be seen that the traditional narrowband filter uses a CMOS type OTA circuit, the gain value of the CMOS type OTA circuit is low, the gain adjustable range is small, and the dynamic input range is also small, and g m Value sensitivity is high, which greatly limits the adjustment range of the filter

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