Complex filter with automatic tuning capabilities
OwnerSeeteck Tan, Du Dingkun +1inventors
InventorsSeeteck Tan, Du Dingkun, Li Yongming
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Abstract
A complex filter with automatic tuning capabilities for filtering a complex signal is disclosed. The complex filter includes a first lowpass filter, a second lowpass filter, a plurality of resistors, an integrator, a comparator, and a digital unit. The complex filter includes an imaginary component and a real component. The integrator, the comparator and the digital unit forms a tuning circuit. The tuning circuit can generate a plurality of control signals to tune the complex filter to a predetermined frequency. The tuning circuit can be turned off after a predetermined period.
Claims23
A complex filter with automatic tuning capabilities for filtering a complex signal, the complex signal having an imaginary component and a real component, the complex filter comprising:
- a first lowpass filter capable of receiving the imaginary component of the complex signal and generating a signal as an output signal of the complex filter;
- a second lowpass filter capable of receiving the real component of the complex signal;
- a plurality of resistors coupled between the first and the second lowpass filters;
- an integrator capable of receiving a first reference voltage and generating an output signal;
- a comparator capable of comparing the output signal from the integrator with a second reference voltage and generating a digital signal according to a result of comparison;
- and
- a digital unit capable of receiving the digital signal and generating a first control signal, a second control signal, a third control signal and a fourth control signal, the fourth control signal being delivered to the first and the second lowpass filters.
A tuning system for a complex filter, the tuning system comprising:
- a tuning circuit capable of generating a latch up signal, the tuning circuit including:
- an integrator capable of receiving a first reference voltage and generating an output signal;
- a comparator capable of comparing the output signal from the integrator with a second reference voltage and generating a digital signal;
- and
- a digital unit capable of receiving the digital signal and generating a first control signal, a second control signal, a third control signal and a fourth control signal, the fourth control signal being capable of tuning the complex filter to a predetermined frequency;
- a transistor receiving the latch up signal, the transistor being controlled by the latch up signal;
- and
- a final latch capable of receiving the latch up signal and transferring the fourth control signal to the complex filter in a tuning mode and turning off the tuning circuit after a predetermined period.
A receiver for processing a radio frequency (RF) signal, comprising:
- a bandpass filter (BPF) capable of filtering the RF signal;
- a low noise amplifier (LNA) capable of amplifying the filtered RF signal;
- two radio frequency-to-intermediate frequency (RF-IF) mixers capable of receiving the amplified RF signal and converting the amplified RF signal to an IF signal, the IF signal being a complex signal and including an imaginary component and a real component;
- a complex filter capable of receiving the IF signal and generating an analog signal, the complex filter being a BPF;
- a variable gain amplifier (VGA) with an automatic gain control (AGC) loop capable of amplifying the analog signal;
- an analog-to-digital converter (ADC) capable of converting the amplified analog signal to a digital signal for further processing;
- and
- a digital circuit capable of processing the digital signal from the ADC and transferring the digital signal to an external element.
A method for automatically tuning a complex filter, comprising the steps of:
- (a) generating a charge current;
- (b) generating a voltage signal through charging and discharging a capacitor bank;
- (c) comparing the voltage signal with a reference voltage;
- (d) generating a digital signal based upon a result of the comparison;
- (e) generating a charge control signal, a discharge control signal, a first switch control signal, and a second switch control signal at a digital unit based upon the digital signal;
- and
- (f) tuning the complex filter to a predetermined frequency through the second switch control signal from the digital unit.
Dependencies are inferred from the claim text.