Poly-phase filter
View Patent ↗Provided is a poly-phase filter capable of removing an image frequency of a terrestrial digital multimedia broadcasting (T-DMB) receiver in a low intermediate frequency (IF) structure applied to a mobile communication terminal and a receiver having the poly-phase filter. The poly-phase filter includes: a calibration control block for generating first and second filter characteristic control signals which determine electrical characteristics of the filter in response to a control signal including instructions for changing the characteristics of the poly-phase filter and holding the changed values; and a poly-phase filter block for performing filtering on a plurality of input signals having different phases from each other in response to the first and second filter characteristic control signals. Accordingly, the poly-phase filter has advantages of having constant electrical characteristics regardless of changes in a manufacturing process and temperature and a high-performance image rejection function.
1. A poly-phase filter comprising:
a calibration control block generating a first filter characteristic control signal and a second filter characteristic control signal for determining electrical characteristics of the filter in response to first and second control signals; and
a poly-phase filter block performing filtering on a plurality of input signals having different phases from each other in response to the first and second filter characteristic control signals,
wherein the poly-phase filter block comprises at least one poly-phase filter circuit which performs filtering on a plurality of input signals having different phases from each other in response to the first and second filter characteristic control signals,
wherein the poly-phase filter circuit comprises a number of phase filters corresponding to a plurality of the input signals,
wherein a plurality of the input signals are first to fourth input signals having phases which are different from each other by 90°, and
wherein a number of the phase filters comprise:
a first phase filter performing filtering on the first input signal based on the second input signal;
a second phase filter performing filtering on the second input signal based on the third input signal;
a third phase filter performing filtering on the third input signal based on the fourth input signal; and
a fourth phase filter performing filtering on the fourth input signal based on the first input signal, and
wherein filter characteristics of the four phase filters are controlled by the first and second filter characteristic control signals.
2. The poly-phase filter of claim 1 ,
wherein each of the first to fourth phase filters includes the first type device and the second type device,
wherein the first type device is a variable resistor having a resistance that is determined by the first filter characteristic control signal, and
wherein the second type device is a variable capacitor having a capacitance that is determined by the second filter characteristic control signal.
3. The poly-phase filter of claim 2 ,
wherein the first phase filter comprises a first variable resistor having a terminal connected to the first input signal and the other terminal generating a first output signal and a first variable capacitor having a terminal connected to the other terminal of the first variable resistor and the other terminal connected to the second input signal;
wherein the second phase filter comprises a second variable resistor having a terminal connected to the second input signal and the other terminal generating a second output signal and a second variable capacitor having a terminal connected to the other terminal of the second variable resistor and the other terminal connected to the third input signal;
wherein the third phase filter comprises a third variable resistor having a terminal connected to the third input signal and the other terminal generating a third output signal and a third variable capacitor having a terminal connected to the other terminal of the third variable resistor and the other terminal connected to the fourth input signal; and
wherein the fourth phase filter comprises a fourth variable resistor having a terminal connected to the fourth input signal and the other terminal generating a fourth output signal and a fourth variable capacitor having a terminal connected to the other terminal of the fourth variable resistor and the other terminal connected to the first input signal.