Methods and apparatus for detecting the envelope of RF power signals

• US 20040018821A1
• Filed: 04/18/2003
• Published: 01/29/2004
• Est. Priority Date: 06/03/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Paragon Communications Limited
• Inventors: Bar-David, Israel, Veinblat, Alexander
• Granted Patent: US 7,257,384 B2
• Time in Patent Office: Days
• US Class Current: 455/149
• CPC Class Codes: H03C 1/36 by means of semiconductor device having at least three electrodes H03C1/34, H03C1/50, H03C1/52, H03C1/62 take precedence
• CPC Class Codes: H03F 3/193 with field-effect devices H03F3/195 takes precedence

Abstract

Apparatus for detecting the envelope of an RF signal that comprises an RF transistor operating essentially at a non-linear operating point at the RF frequency range; a DC power supply for feeding the RF transistor; a dummy load for terminating the output of the RF transistor; and at lease one impedance, through which the DC power supply feeds the RF transistor, for obtaining an indication signal developed across the impedance. The indication signal represents the envelope, from the fluctuating current drawn by the RF transistor from the DC power supply during the time period when the RF signal is applied to the feeding input.

Claims

1. A method for detecting an envelope of an RF signal, comprising:

(a) providing an RF transistor operating essentially at a nonlinear operating point at the RF frequency range, said RF transistor being fed by a DC power supply through an RF filter and terminated by a dummy load for RF components in an output signal of said RF transistor;

(b) feeding an RF signal into a input of said RF transistor; and

(c) obtaining an output signal representing said envelope from a fluctuating current drawn by said RF transistor from said DC power supply during a time period when said RF signal is applied to said input.

2. A method according to claim 1, wherein the output signal is obtained by filtering out the RF components from the fluctuating current, thereby obtaining the mean detected current, being monotonically related to the envelope of the RF signal.

3. A method according to claim 2, wherein whenever the RF transistor is a FET having a grounded source or a bipolar transistor having a grounded emitter, wherein the output signal is obtained by performing the following steps:

(a) connecting a first contact of an RF filter to one of a drain of said FET and a collector of said bipolar transistor;

(b) connecting a negative contact of the DC power supply to ground;

(c) connecting a positive contact of said DC power supply to a second contact of said RF filter through an impedance; and

(d) coupling the voltage developed across said impedance by a coupling capacitor, thereby determining the polarity of the output signal to be opposite to the polarity of said DC power supply.

4. A method according to claim 2, wherein the RF transistor is one of a FET having a drain and a bipolar transistor having an collector, being connected to a positive contact of the DC power supply, wherein the output signal is obtained by performing the following steps:

(a) connecting a negative contact of the DC power supply to ground;

(b) connecting one of a source of said FET and the emitter of said bipolar transistor to ground through a impedance;

(c) biasing one of a gate of said FET and the base of said bipolar transistor, through a biasing resistor connected in series with an RF filter, connected to said gate or to said base;

(d) connecting a capacitor between a common contact of said RF filter and said biasing resistor, and said source or said emitter; and

(e) coupling the voltage developed across said impedance by a coupling capacitor, thereby determining the polarity of the output signal to have polarity being similar to the polarity of said DC power supply.

5. A method according to claim 4, further comprising obtaining two output signals having opposite polarities by performing the following steps:

(a) connecting a first contact of an RF filter to one of a drain of said FET and a collector of said bipolar transistor;

(b) connecting the negative contact of the DC power supply to ground;

(c) connecting the positive contact of said DC power supply to the other contact of said RF filter through a first impedance;

(d) connecting one of the source of said FET and the emitter of said bipolar transistor to ground through a second impedance;

(e) biasing one of the gate of said FET and the base of said bipolar transistor through a biasing resistor connected in series with an RF filter, connected to one of said gate and said base;

(f) connecting a capacitor between the common contact of said RF filter and said biasing resistor, and said source or said emitter;

(g) coupling the voltage developed across said first impedance by a coupling capacitor, thereby determining the polarity of the output signal to be opposite to the polarity of said DC power supply; and

(h) coupling the voltage developed across said second impedance by a coupling capacitor, thereby determining the polarity of the output signal to have polarity being similar to the polarity of said DC power supply.

6. A method according to claim 1, further comprising matching the input and the output of the RF transistor, thereby causing said RF transistor to be unconditionally stable under any load and/or level of RF signal.

7. A method according to claim 1, wherein the non-linear operating point is selected from the following classes of operation:

Class B;

Class AB;

Class C.

8. A method according to claim 1, wherein the impedance is a pure resistance or a pure reactance or any combination thereof.

9. Apparatus for detecting an envelope of an RF signal, comprising:

(a) an RF transistor operating essentially at a non-linear operating point at the RF frequency range;

(b) a DC power supply for feeding said RF transistor;

(c) a dummy load for terminating the output of said RF transistor; and

(d) at lease one impedance, through which said DC power supply feeds said RF transistor, for obtaining an indication signal developed across said impedance, said indication signal representing said envelope, from the fluctuating current drawn by said RF transistor from said DC power supply during the time period when said RF signal is applied to the feeding input.

10. Apparatus according to claim 9, in which the indication signal is proportional to the envelope of the detected RF signal.

11. Apparatus according to claim 9, further comprising circuitry for matching an input and an output of the RF transistor, for causing said RF transistor to be unconditionally stable under any load and/or level of RF signal.

12. Apparatus according to claim 9, comprising:

(a) an RF power transistor biased to operate essentially under Class B condition at the RF frequency range;

(b) a DC power supply for feeding said RF transistor, connected to ground by a first capacitor, and to an output port of said RF transistor through an RF filter for isolating RF frequency components from reaching said DC power supply;

(c) an input matching circuitry for matching said RF transistor to the source of the RF signal, the amplitude of which is detected;

(d) an output matching circuitry for matching said RF transistor to a dummy load, terminating said output port; and

(e) an output contact, connected to a contact of said RF filter, at which an indication signal representing said amplitude, or variations in said amplitude, from the fluctuating current drawn by said RF transistor from said DC power supply during the time period when said RF signal is applied by said source, is developed.

13. Apparatus according to claim 9, wherein the RF transistor is a FET having a grounded source or a bipolar transistor having a grounded emitter, comprising:

(a) an RF filter, connected to one of a drain of said FET and a collector of said bipolar transistor;

(b) a DC power supply, having a negative contact being connected to ground and a positive contact being connected to the other contact of said RF filter through a impedance; and

(c) a coupling capacitor, connected to said other contact, for coupling the voltage developed across said impedance, the polarity of which being opposite to the polarity of said DC power supply.

14. Apparatus according to claim 9, in which the RF transistor is a FET having a drain or a bipolar transistor having a collector, being connected to the positive contact of the DC power supply through an RF filter, the negative contact of which is connected to ground, comprising:

(a) a first impedance, connected between one of a source of said FET and an emitter of said bipolar transistor, and ground;

(b) a biasing resistor, connected in series with an RF filter that is connected to one of the gate of said FET and the base of said bipolar transistor, for biasing said gate or said base;

(c) a capacitor, connected between a common contact of said RF filter and said biasing resistor, and one of said source and said emitter; and

(d) a first coupling capacitor, connected to the ungrounded contact of said first impedance, for coupling the voltage developed across said first impedance, the polarity of which being similar to the polarity of said DC power supply.

15. Apparatus according to claim 14, further comprising:

(a) a second impedance, connected in series between the RF filter and the DC power supply; and

(b) a second coupling capacitor, connected to a common contact between said second impedance and said RF filter, for coupling the voltage developed across said second impedance, the polarity of which being opposite to the polarity of said DC power supply.

16. Apparatus according to claim 9, in which the non-linear operating point is selected from the following classes of operation:

Class B;

Class AB;

Class C.

17. Apparatus according to any claim 9, in which the impedance is a pure resistance or a pure reactance or any combination thereof.