A SUB-HARMONIC MIXER AND A METHOD THEREIN FOR CONVERTING RADIO FREQUENCY SIGNALS TO INTERMEDIATE FREQUENCY SIGNALS

• US 20170025999A1
• Filed: 12/02/2013
• Published: 01/26/2017
• Est. Priority Date: 12/02/2013
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Bao, Mingquan
• Granted Patent: US 9,912,293 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H03D 7/12 by means of semiconductor devices having more than two electrodes H03D7/14 - H03D7/22 take precedence
• CPC Class Codes: H03D 7/125 with field effect transistors
• CPC Class Codes: H03D 7/163 the local oscillations of at least two of the frequency changers being derived from a single oscillator

Abstract

A sub-harmonic mixer two or more cascaded stages for converting a Radio Frequency signal to an Intermediate Frequency signal. Each stage comprises a common-emitter transistor or a common-source transistor and each stage having an input and an output, the output of each stage is coupled to the input of a next stage by a capacitor. An Alternating Current choke is coupled at a collector or drain of each transistor. An LO input is coupled to the input of a first stage of the two or more stages; an RF input is coupled to the output of the first stage of the two or more stages; and an IF output is coupled to the output of a last stage of the two or more stages.

Claims

1. A sub-harmonic mixer for converting a Radio Frequency, RF, signal to an Intermediate Frequency, IF, signal, the sub-harmonic mixer comprising:

a Local Oscillator, LO, input to receive an LO signal;

an RF input to receive the RF signal;

an IF output to output the IF signal; and

a circuit comprising two or more cascaded stages, wherein

each stage having an input and an output, the output of each stage is coupled to the input of a next stage by a capacitor;

each stage comprising a common-emitter transistor having a base, a collector and an emitter, or a common-source transistor having a gate, a drain and a source;

the input of each stage is at the base or gate of the transistor, the output of each stage is at the collector or drain of the transistor;

an Alternating Current, AC, choke is coupled at the collector or drain of each transistor; and

the emitter or source of each transistor is connected to a ground; and

wherein

the LO input is coupled to the input of a first stage of the two or more stages;

the RF input is coupled to the output of the first stage of the two or more stages; and

the IF output is coupled to the output of a last stage of the two or more stages.

2. The sub-harmonic mixer according to claim 1, wherein the RF input is coupled to the output of the first stage of the two or more stages through a high pass filter.

3. The sub-harmonic mixer according to claim 1, wherein the IF output is coupled to the output of a last stage of the two or more stages through a low-pass filter and matching network.

4. The sub-harmonic mixer according to claim 1, wherein the base or gate of each transistor is coupled to a respective Direct Current, DC, supply through a resistor.

5. The sub-harmonic mixer according to claim 1, wherein the LO input is coupled to the input of a first stage of the two or more stages through a capacitor.

6. The sub-harmonic mixer according to claim 1, wherein the sub-harmonic mixer is a multi-band sub-harmonic mixer operating with different LO harmonic signals for converting RF signals having different frequencies to an IF signal.

7. The sub-harmonic mixer according to claim 6, wherein different LO harmonic signals comprises LO harmonics from 4th up to 7th order.

8. The sub-harmonic mixer according to claim 1, wherein the sub-harmonic mixer is situated in a wireless communication device.

9. A method in a sub-harmonic mixer for converting a Radio Frequency, RF, signal to an Intermediate Frequency, IF, signal, wherein the sub-harmonic mixer comprises a circuit having two or more cascaded stages each stage having an input and an output, the output of each stage is coupled to the input of a next stage by a capacitor;

the method comprising;

receiving a Local Oscillator, LO, signal at an input of a first stage of the two or more cascaded stages;

receiving the RF signal at an output of the first stage;

amplifying the LO signal and generating LO harmonic signals in the first stage;

generating a first IF signal by mixing the RF signal with one of generated LO harmonic signal in the first stage;

amplifying the generated first IF signal in stages of the two or more cascaded stages following the first stage;

generating a second IF signal by mixing the RF signal with one of the generated LO harmonic signal in the stages of the two or more cascaded stages following the first stage;

generating the IF signal by combining the amplified first IF signal and the generated second IF signal at an output of a last stage of the two or more cascaded stages; and

outputting the generated IF signal to an IF output.

10. The method according to claim 9, wherein receiving the RF signal at the output of the first stage comprises receiving the RF signal at the output of the first stage through a high pass filter.

11. The method according to claim 9, wherein outputting the generated IF signal to the IF output comprises outputting the generated IF signal to the IF output through a low-pass filter and matching network.

12. The method according to claim 9, wherein receiving a Local Oscillator, LO, signal at an input of a first stage of the two or more cascaded stages comprises receiving the LO signal at the input of the first stage through a third capacitor.

13. The method according to claim 9, wherein the sub-harmonic mixer is a multi-band sub-harmonic mixer operating with different LO harmonic signals for converting RF signals having different frequencies to an IF signal.

14. The method according to claim 13, wherein different LO harmonic signals comprises LO harmonics from 4th up to 7th order.