LOW NOISE AMPLIFIER AND RELATED METHOD

• US 20060066410A1
• Filed: 09/24/2004
• Published: 03/30/2006
• Est. Priority Date: 09/24/2004
• Status: Active Grant

• Current Assignee: Realtek Semiconductor Corp.
• Original Assignee: Realtek Semiconductor Corp.
• Inventors: Razavi, Behzad, Kang, Han-Chang
• Granted Patent: US 7,084,707 B2
• Time in Patent Office: Days
• US Class Current: 330/302
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• CPC Class Codes: H03F 3/189 High-frequency amplifiers, e.g. radio frequency amplifiers

Abstract

A low noise amplifier (LNA) for filtering an input signal to generate an output signal. The low noise amplifier includes a switched loading circuit having a plurality of loading units, each of the loading units determining a corresponding center frequency of the low noise amplifier. The switched loading circuit selectively enables a loading unit having the desired corresponding center frequency. At least one converters coupled to the switched loading circuit converts a voltage of the input signal into a loading current and passes the loading current through the enabled loading unit to generate the output signal.

Claims

1. A low noise amplifier (LNA) for filtering an input signal to generate an output signal, comprising:

a switched loading circuit comprising a plurality of loading units, each of the loading units determining a corresponding center frequency of the LNA, the switched loading circuit for selectively enabling at least one loading unit having the corresponding center frequency; and

at least one converter coupled to the switched loading circuit for converting the input signal into a loading current and passing the loading current through the enabled loading unit to generate the output signal.

2. The LNA of claim 1, wherein the loading units include a first loading unit and a second loading unit, and the switched load circuit further comprises:

a first switch coupled to the first loading unit and the converter, wherein if the first switch is switched on, the first loading unit is coupled to the at least one converter; and

a second switch coupled to the second loading unit and the converter, wherein if the second switch is switched on, the second loading unit is coupled to the at least one converter.

3. The LNA of claim 1, wherein each of the loading units comprises an inductor.

4. The LNA of claim 3, wherein each of the loading units further comprises a capacitor coupled to the inductor in parallel.

5. The LNA of claim 4, wherein each of the loading units further comprises a resistor coupled to the inductor in series.

6. The LNA of claim 1 further comprising:

a gain controller for controlling the at least one converter according to a desired gain.

7. The LNA of claim 6, wherein the at least one converter comprises a controlled loading unit for adjusting the input impedance to a predetermined value.

8. The LNA of claim 1 being applied to a wideband communication system.

9. A low noise amplifier (LNA) for filtering an input signal to generate an output signal, comprising:

a switched loading circuit comprising a plurality of loading units, each of the loading units determining a corresponding center frequency, the switched loading circuit for selectively enabling at least one loading unit;

a first converter coupled to the switched loading circuit for converting the input signal into a first loading current; and

a second converter coupled to the switched loading circuit for converting the input signal into a second loading current;

wherein the output signal is generated according to the first loading current or the second loading current or both.

10. The LNA of claim 9, wherein the controlled loading unit is enabling according to the operation situation of the first and the second converters.

11. The LNA of claim 9, further comprising:

a controlled loading unit for adjusting the input impedance of the LNA to a predetermined value.

12. The LNA of claim 9, further comprising:

a gain controller for driving the first and the second converters according to a desired gain.

20. The method of claim 9 being applied to a wideband communication system.

13. A low noise amplifying method for filtering an input signal to generate an output signal, comprising:

providing a plurality of loading units, each of the loading units determining a corresponding center frequency;

selectively enabling at least one loading unit; and

converting the input signal into a loading current and passing the loading current through the enabled loading unit to generate the output signal.

14. The method of claim 13, wherein the loading units include a first loading unit and a second loading unit, and the step of selectively enabling comprises:

providing a first switch and a second switch;

switching on the first switch to enable the first loading unit; and

switching on the second switch to enable the second loading unit.

15. The method of claim 13, wherein each of the loading units comprises an inductor.

16. The method of claim 15, wherein each of the loading units further comprises a capacitor coupled to the inductor in parallel.

17. The method of claim 16, wherein each of the loading units further comprises a resistor coupled to the inductor in series.

18. The method of claim 13 further comprising:

converting the input signal into a second loading current and passing the second loading current through the enabled loading unit according to a desired gain to generate the output signal.

19. The method of claim 13 further comprising:

controlling a controlled loading unit to match the input impedance to a predetermined value.