EQUIVALENT RADIO FREQUENCY NOTCH FILTER, RADIO FREQUENCY CHIP, AND RECEIVER

• US 20110230157A1
• Filed: 05/27/2011
• Published: 09/22/2011
• Est. Priority Date: 11/27/2008
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: YANG, Fan, LIU, Xinfang, WANG, Meng, WANG, Hongyu, YI, Min, CHI, Yusong, HU, Xinrong, ZHOU, Jianjun, HE, Zhuobiao
• Granted Patent: US 8,385,873 B2
• Time in Patent Office: Days
• US Class Current: 455/326
• CPC Class Codes: H03D 7/1441 using field-effect transistors H03D7/145 takes precedence
• CPC Class Codes: H03D 7/1458 Double balanced arrangements, i.e. where both input signals are differential
• CPC Class Codes: H04B 1/26 for superheterodyne receivers multiple frequency-changing H03D7/16

Abstract

An equivalent radio frequency (RF) notch filter, an RF chip, and a receiver are provided. The equivalent RF notch filter includes: a local oscillation (LO) circuit, configured to provide a LO frequency signal; configured to be connected in parallel with the main chain, and down-convert signals of the main chain; and a frequency selective circuit realized by impedance difference, configured to provide different impedances for down-converted signals with different frequencies from the mixing circuit, so as to absorb the signals that need to be suppressed.

Claims

1. An equivalent radio frequency (RF) notch filter, configured to absorb a signal to be suppressed, comprising:

a local oscillation (LO) circuit, configured to provide a LO frequency signal;

a mixing circuit, having an input end electrically connected to a main chain of an RF circuit, configured to be connected in parallel with the main chain, down-convert the signal to be suppressed according to the LO frequency signal, and output a down-converted signal; and

a frequency selective circuit realized by impedance difference, connected to a baseband output end of the mixing circuit, and configured to provide different impedances for down-converted signals with different frequencies from the mixing circuit.

2. The equivalent RF notch filter according to claim 1, wherein the mixing circuit is a differential passive mixing circuit, the frequency selective circuit realized by impedance difference has differential input, and the differential passive mixing circuit comprises four field effect transistors (FETs);

and

wherein a source of a first FET is connected with a source of a second FET at a connection point being an RF differential input positive end, a source of a third FET is connected with a source of a fourth FET at a connection point being an RF differential input negative end, a drain of the first FET is connected with a drain of the third FET at a connection point being a baseband differential output positive end, a drain of the second FET is connected with a drain of the fourth FET at a connection point being a baseband differential output negative end, gates of the first FET and the fourth FET are an input positive end of the LO circuit, and gates of the second FET and the third FET are an input negative end of the LO circuit.

3. The equivalent RF notch filter according to claim 1, wherein the mixing circuit is a single-end passive mixing circuit, the frequency selective circuit realized by impedance difference has a single-end input, and the single-end passive mixing circuit comprises an FET, wherein the FET has a source being an RF input, a drain being the baseband output end of the mixing circuit, and a gate being a LO frequency input end.

4. The equivalent RF notch filter according to claim 1, wherein the mixing circuit is connected in parallel between a first low noise amplifier (LNA) and a mixer in the main chain.

5. The equivalent RF notch filter according to claim 1, wherein the mixing circuit is connected in parallel between a first LNA and a second LNA in the main chain.

6. The equivalent RF notch filter according to claim 1, wherein the mixing circuit is connected in parallel with a high-impedance node in front of the mixer in the main chain.

7. The equivalent RF notch filter according to claim 1, wherein the frequency selective circuit realized by impedance difference has a structure of connecting an inductor in parallel to the ground;

when the mixing circuit is a differential passive mixing circuit, two ends of the inductor are connected with the baseband output end of the mixing circuit; and

when the mixing circuit is a single-end passive mixing circuit, one end of the inductor is connected with the baseband output end of the mixing circuit, and the other end of the inductor is connected to the ground.

8. The equivalent RF notch filter according to claim 1, wherein the frequency selective circuit realized by impedance difference has a structure of connecting a capacitor in parallel to the ground;

when the mixing circuit is a differential passive mixing circuit, two ends of the capacitor are connected with the baseband output end of the mixing circuit; and

when the mixing circuit is a single-end passive mixing circuit, one end of the capacitor is connected with the baseband output end of the mixing circuit, and the other end of the capacitor is connected to the ground.

9. The equivalent RF notch filter according to claim 1, wherein the frequency selective circuit realized by impedance difference has a structure of connecting a low-frequency resonant network in parallel to the ground;

when the mixing circuit is a differential passive mixing circuit, two ends of the resonant network are connected with the baseband output end of the mixing circuit; and

when the mixing circuit is a single-end passive mixing circuit, one end of the resonant network is connected with the baseband output end of the mixing circuit, and the other end of the resonant network is connected to the ground.

10. The equivalent RF notch filter according to claim 1, wherein the frequency selective circuit realized by impedance difference is a low inband impedance trans-impedance circuit;

when the mixing circuit is a differential passive mixing circuit, the low inband impedance trans-impedance circuit is a differential circuit, and

when the mixing circuit is a single-end passive mixing circuit, the low inband impedancetrans-impedance circuit is a single-end circuit.

11. The equivalent RF notch filter according to claim 1, wherein the frequency selective circuit realized by impedance difference parallels with the baseband output end of the mixing circuit and the mixing circuit is a passive mixing circuit.

12. A radio frequency (RF) chip, comprising a main chain including at least one low noise amplifier (LNA) and a mixer, and further comprising an equivalent RF notch filter, wherein the equivalent RF notch filter comprises:

a local oscillation (LO) circuit, configured to provide a LO frequency signal;

a mixing circuit, having an input end electrically connected to the main chain, configured to be connected in parallel with the main chain, down-convert a signal that need to be suppressed according to the LO frequency signal, and output a down-converted signal; and

a frequency selective circuit realized by impedance difference, connected to a baseband output end of the mixing circuit, and configured to provide different impedances for down-converted signals with different frequencies from the mixing circuit.

13. The RF chip according to claim 12, wherein the mixing circuit is a differential passive mixing circuit, the frequency selective circuit realized by impedance difference has differential input, and the differential passive mixing circuit comprises four field effect transistors (FETs);

and

wherein a source of a first FET is connected with a source of a second FET at a connection point being an RF differential input positive end, a source of a third FET is connected with a source of a fourth FET at a connection point being an RF differential input negative end, a drain of the first FET is connected with a drain of the third FET at a connection point being a baseband differential output positive end, a drain of the second FET is connected with a drain of the fourth FET at a connection point being a baseband differential output negative end, gates of the first FET and the fourth FET are an input positive end of the LO circuit, and gates of the second FET and the third FET are an input negative end of the LO circuit.

14. The RF chip according to claim 12, wherein the mixing circuit is a single-end passive mixing circuit, and the frequency selective circuit realized by impedance difference has a single-end input, and the single-end passive mixing circuit comprise a FET, wherein the FET has a source being an RF input, a drain being the baseband output end of the mixing circuit and a gate being a LO frequency input end.

15. The RF chip according to claim 12, wherein the frequency selective circuit realized by impedance difference has a structure of connecting an inductor in parallel to the ground;

when the mixing circuit is a differential passive mixing circuit, two ends of the inductor are connected with the baseband output end of the mixing circuit; and

when the mixing circuit is a single-end passive mixing circuit, one end of the inductor is connected to the the baseband output end of the mixing circuit, and the other end of the inductor is connected to the ground.

16. The RF chip according to claim 12, wherein the frequency selective circuit realized by impedance difference has a structure of connecting a capacitor in parallel to the ground;

when the mixing circuit is a differential passive mixing circuit, two ends of the capacitor are connected with the baseband output end of the mixing circuit; and

when the mixing circuit is a single-end passive mixing circuit, one end of the capacitor is connected with the baseband output end of the mixing circuit, and the other end of the capacitor is connected to the ground.

17. The RF chip according to claim 12, wherein the frequency selective circuit realized by impedance difference has a structure of connecting a low-frequency resonant network in parallel to the ground;

when the mixing circuit is a differential passive mixing circuit, two ends of the resonant network are connected with the baseband output end of the mixing circuit; and

when the mixing circuit is a single-end passive mixing circuit, one end of the resonant network is connected with the baseband output end of the mixing circuit, and the other end of the resonant network is connected to the ground.

18. The RF chip according to claim 12, wherein the frequency selective circuit realized by impedance difference is a low inband impedance trans-impedance circuit;

when the mixing circuit is a differential passive mixing circuit, the low inband impedance trans-impedance circuit is a differential circuit, and

when the mixing circuit is a single-end passive mixing circuit, the low inband impedance trans-impedance circuit is a single-end circuit.

19. A receiver, comprising a radio frequency (RF) chip and a main chain including at least one low noise amplifier (LNA) and a mixer, wherein the RF chip comprises:

a local oscillation (LO) circuit, configured to provide a LO frequency signal;

a mixing circuit, having an input end electrically connected to the main chain, configured to be connected in parallel with the main chain, and down-convert a signal of that need to be suppressed according to the LO frequency signal, and output a down-converted signal; and

a frequency selective circuit realized by impedance difference, connected to a baseband output end of the mixing circuit, and configured to provide different impedances for down-converted signals with different frequencies from the mixing circuit.

20. The receiver according to claim 19, wherein the mixing circuit is a differential passive mixing circuit, and the frequency selective circuit realized by impedance difference connected to the differential passive mixing circuit has differential input, and the differential passive mixing circuit comprises four field effect transistors (FETs);

and

wherein a source of a first FET is connected with a source of a second FET at a connection point being an RF differential input positive end, a source of a third FET is connected with a source of a fourth FET at a connection point being an RF differential input negative end, a drain of the first FET is connected with a drain of the third FET at a connection point being a baseband differential output positive end, a drain of the second FET is connected with a drain of the fourth FET at a connection point being a baseband differential output negative end, gates of the first FET and the fourth FET are an input positive end of the LO circuit, and gates of the second FET and the third FET are an input negative end of the LO circuit.