Circuit for Detecting the Impedance of a Load

• US 20080186032A1
• Filed: 09/09/2005
• Published: 08/07/2008
• Est. Priority Date: 09/14/2004
• Status: Active Grant

• Current Assignee: Qualcomm Technologies Incorporated (Qualcomm, Inc.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van Bezooijen, Adrianus, Chanlo, Christophe
• Granted Patent: US 7,821,273 B2
• Time in Patent Office: Days
• US Class Current: 324/646
• CPC Class Codes: G01R 27/04 in circuits having distributed constants , e.g. having very long conductors or involving high frequencies
• CPC Class Codes: H03H 11/20 Two-port phase shifters providing an adjustable phase shift
• CPC Class Codes: H03H 11/22 providing two or more phase shifted output signals, e.g. n-phase output
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance
• 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

The invention refers to a circuit and a method for detecting the impedance of a load, whereby the circuit and the method can be used by an impedance matching circuit. Impedance matching circuits need a complex algorithm to adjust the impedance accordingly. This algorithm renders the response time to be long. It has been found out that the complexity partially stems from the fact that the phase of the reflection coefficient is not known over the full range of 0° to 360°. A quadrature phase detector is used to provide the full phase information.

Claims

1. Circuit for detecting the impedance or the admittance of a load, comprising:

a) a directional coupler having input terminals being connectable to a radio frequency amplifier and being connectable to the load,

b) the directional coupler having output terminals being connected to

b1) first means for measuring the magnitude of the voltage or the magnitude of the current of the forward wave,

b2) second means for measuring the magnitude of the voltage or the magnitude of the current of the reflected wave,

b3) a quadrature phase detector being arranged to output signals providing information on the phase θ

of the reflection coefficient Γ

within a range of 0°

to 360°

.

2. Circuit according to claim 1, whereby the first means and the second means are peak detectors.

3. Circuit according to claim 2, whereby the peak detector comprises a mixer and an amplitude limiter.

4. Circuit according to claim 1, whereby the first means and the second means comprise buffer amplifiers

5. Circuit according to claim 1, whereby the signals providing information on the phase θ

are a signal proportional to sin (θ

), and a signal proportional to cos (θ

).

6. Circuit according to claim 1, whereby the quadrature phase detector is an all-pass filter comprising a 90°

phase shifter.

7. Impedance matching circuit,

a) with an adjustable output matching network being connectable or being connected to an RF amplifier by means of a feed line

b) the adjustable output matching network being connectable or being connected to a load by means of the feed line

b) with a detector for measuring the impedance or the admittance of the load the detector being connectable or being connected to a node of the feed line

d) with a unit for controlling the output of the adjustable matching network the control unit being connected to the detector

e) whereby the detector is a circuit according to one of the claims 1 to 6.

8. Impedance matching circuit according to claim 7, whereby the node is located between the RF amplifier and the adjustable output matching network

9. Impedance matching circuit according to claim 7, whereby the node is located between the adjustable output matching network and the load

10. Method for detecting the impedance or the admittance of a load, the method comprising the following steps:

a) arranging a directional coupler between a radio frequency amplifier and a load

b) arranging the output of a forward wave by the RF amplifier the forward wave travelling towards the load

c) measuring the magnitude of the voltage or the magnitude of the current of the forward wave,

d) measuring the magnitude of the voltage or the magnitude of the current of the reflected wave,

e) measuring the phase θ

of the reflection coefficient Γ

within a range of 0°

to 360°

.

11. Method according to claim 10, whereby measuring the phase θ

of the reflection coefficient Γ

is done by means of a quadrature phase detector.

12. Method according to claim 10, whereby the measuring the magnitude of the voltage or the magnitude of the current is performed by peak detection.