EVALUATION OF A CHARGE IMPEDANCE AT THE OUTPUT OF A DIRECTIONAL COUPLER

• US 20110199100A1
• Filed: 12/03/2010
• Published: 08/18/2011
• Est. Priority Date: 12/18/2009
• Status: Active Grant

• Current Assignee: Stmicroelectronics Tours SAS (STMicroelectronics NV)
• Original Assignee: Stmicroelectronics Tours SAS (STMicroelectronics NV)
• Inventors: Dupont, François, Charley, Sylvain, Bonnet, Benoît
• Granted Patent: US 8,471,568 B2
• Time in Patent Office: Days
• US Class Current: 324/649
• CPC Class Codes: G01R 31/2822 of microwave or radiofrequency circuits of attenuation, gain, e.g. using network analyzers G01R27/28
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H

Abstract

A method and circuit for evaluating a charge impedance at the output of a directional coupling having a first line adapted to convey a wanted signal between a first terminal and a second terminal adapted to be connected to an antenna, and having a second line coupled to the first one including a third terminal on the side of the first terminal and a fourth terminal on the side of the second terminal, wherein the signal present on the fourth terminal is submitted to a homodyne detector having its local oscillator signal sampled from the third terminal.

Claims

1. A circuit for evaluating a charge impedance at the output of a directional coupler (4) having a first line (41) adapted to convey a wanted signal between a first terminal (42) and a second terminal (44) adapted to be connected to an antenna (2), and having a second line (43) coupled to the first one comprising a third terminal (46) on the side of the first terminal and a fourth terminal (48) on the side of the second terminal, the circuit (5) comprising:

a first input terminal (57) adapted to be connected to said third terminal of the coupler;

a second input terminal (59) adapted to be connected to the fourth terminal of the coupler;

a homodyne detector (60) having a first input for a signal to be processed connected to said second input terminal and having a second local oscillator input connected to said first input terminal;

a first low-pass filter (66) having an input connected to a first output of the homodyne detector and providing first data (S66) relative to the charge impedance; and

a second low-pass filter (67) having an input connected to a second output of the homodyne detector and providing second data (S67) relative to the charge impedance.

2. The circuit of claim 1, wherein a first variable-gain amplifier (62) is coupled between said second input terminal (59) of the circuit (5) and said first input of the homodyne detector (60), the gain being set according to the signal level received on said first input (57) of the circuit.

3. The circuit of claim 2, wherein a logarithmic detector (61) is coupled between said first input terminal (57) of the circuit (5) and said second input of the homodyne detector, an output of said detector being connected to a gain control input of said amplifier (62).

4. The circuit of claim 3, wherein the homodyne detector (60) comprises:

a first multiplier (63) having two inputs respectively connected to the first and second inputs of the detector, and having an output connected to the first output of the detector providing said first data (S66); and

a second multiplier (65) having two inputs respectively connected directly to the first input of the detector and, via a 90°

phase shifter (64), to the second input of the detector, and having an output connected to the second output of the detector.

5. The circuit of claim 4, wherein third data relative to the amplitude of the charge impedance are obtained by calculating the square root of the sum of the squares of the first and second data.

6. The circuit of claim 5, wherein fourth data relative to the phase of the charge impedance are obtained by calculating the arc tangent of the ratio of the second data to the first data.

7. A radio frequency transceiver circuit comprising:

a directional coupler (4) having a first line (41) adapted to convey a wanted signal between a first terminal (42) and a second terminal (44) adapted to be connected to an antenna (2), and having a second line (43) coupled to the first one comprising a third terminal (46) on the side of the first terminal and a fourth terminal (48) on the side of the second terminal; and

a circuit (5) for evaluating a charge impedance at the output of the directional coupler of claim 1, the first (57) and second (59) input terminals of the circuit being respectively connected to the third (46) and fourth (48) terminals of the coupler.

8. A method for evaluating a charge impedance at the output of a directional coupler (4) having a first line (41) adapted to convey a wanted signal between a first terminal (42) and a second terminal (44) adapted to be connected to an antenna (2), and having a second line (43) coupled to the first one comprising a third terminal (46) on the side of the first terminal and a fourth terminal (48) on the side of the second terminal, wherein:

the signal present on the fourth terminal is submitted to a homodyne detector (60) having its local oscillator signal sampled from the third terminal.

9. The method of claim 8, wherein:

the signal present on the fourth terminal is multiplied by the signal present on the third terminal, then submitted to a low-pass filtering to provide first data (S66) relative to the charge impedance; and

the signal present on the third terminal is phaseshifted by 90°

(64), then multiplied (65) by the signal present on the fourth terminal, the result of the multiplication being submitted to a low-pass filtering (67) to provide second data (S67) relative to the charge impedance.