Circuit for matching the load impedance of an electronic device
A circuit matches the load impedance of an electronic device. The circuit comprises an impedance network, a control circuit suitable for varying the impedance of said network and a sensor coupled with said network and said load and suitable for detecting the ratio between the incident and reflected standing waves in transferring power from the electronic device to the load; the sensor is suitable for providing two signals substantially proportional to the incident and reflected amplitude of the waves at the control circuit. The impedance network is a network of variable resistances and the control circuit is suitable for varying the value of the resistances to lower said ratio between the incident and reflected standing waves to a value that ensures the transfer of power from the electronic device to the load.
1. A circuit for matching an impedance of a load of an electronic device, said circuit comprising:
a sensor structured to detect a first value of a ratio between incident and reflected standing waves in transferring power from the electronic device to the load, said sensor being structure to provide first and second signals substantially proportional to amplitudes of the incident and reflected standing waves;
an impedance network of variable resistances; and
a control circuit coupled to receive the first and second signals from the sensor and structured to vary values of the resistances to lower said ratio between the incident and reflected standing waves to a second value that ensures the transfer of power from the electronic device to the load.
2. A circuit according to claim 1 , wherein said network of variable resistances comprises at least a resistance arranged serially between the electronic device and the load and at least a resistance arranged parallel to the electronic device.
3. A circuit according to claim 1 , wherein said electronic device is a radio frequency amplifier and said load is an antenna.
4. A circuit according to claim 1 , wherein said network comprises a succession of variable resistances, some of them arranged serially between the electronic device and the load and others arranged parallel to the electronic device.
5. A circuit according to claim 1 , wherein each resistance is made in digital form with dedicated switches.
6. A circuit according to claim 1 , wherein the network comprises a resistance arranged serially between the electronic device and the load, a resistance arranged parallel to the electronic device, and a switch arranged parallel to the serial resistance and activatable when mismatching is not present.
7. A circuit according to claim 1 , wherein the first value of said ratio between the incident and reflected standing waves detected by said sensor belongs to a first circumference on a Smith chart, said first circumference being a place of points with said detected first value and being tangential to standardized and constant reactance and susceptance circumferences, and the second value of said ratio between the incident and reflected standing waves belongs to a second circumference on the Smith chart, said second circumference being a place of points with said second value and being tangential to the standardized and constant reactance and susceptance circumferences, said control circuit being suitable for varying the values of the resistances for transforming a point belonging to said first circumference in a point belonging to said second circumference moving on the standardized and constant reactance and susceptance circumferences on the Smith chart.
8. A circuit according to claim 7 , wherein said network comprises at least a resistance arranged serially between the electronic device and the load and at least a resistance arranged parallel to the electronic device, said control circuit is suitable for defining the values of said resistances in accordance with the following system:
{
1
r
s
+
V
+
1
r
p
=
1
Vr
1
r
s
+
1
/
V
+
1
r
p
=
Vr
,
having as a solution
{
r
s
=
V
2
-
1
·
(
(
Vr
2
-
1
)
·
(
V
2
(
Vr
2
-
1
)
+
4
V
*
Vr
-
Vr
2
+
1
)
+
(
Vr
2
+
1
)
·
V
2
-
1
)
2
(
V
2
*
Vr
+
V
(
1
-
Vr
2
)
-
Vr
)
r
p
=
V
2
-
1
·
(
Vr
2
-
1
)
·
(
V
2
(
Vr
2
-
1
)
+
4
V
*
Vr
-
Vr
2
+
1
)
+
(
1
-
Vr
2
)
·
(
V
2
+
1
)
2
V
(
Vr
2
-
1
)
.
where r s is the series resistance, r p is the parallel resistance, V is the first value of the ratio between the incident and reflected standing waves detected by the sensor and Vr is the second value of the ratio between the incident and reflected standing waves.
9. A system, comprising:
an electronic device;
a load; and
a circuit coupled to the electronic device and the load and structured to match an impedance of the load, said circuit including:
a sensor structured to detect a first value of a ratio between incident and reflected standing waves in transferring power from the electronic device to the load, said sensor being structure to provide first and second signals substantially proportional to amplitudes of the incident and reflected standing waves;
an impedance network of variable resistances; and
a control circuit coupled to receive the first and second signals from the sensor and structured to vary values of the resistances to lower said ratio between the incident and reflected standing waves to a second value that ensures the transfer of power from the electronic device to the load.
10. A system according to claim 9 , wherein said network of variable resistances comprises at least a resistance arranged serially between the electronic device and the load and at least a resistance arranged parallel to the electronic device.
11. A system according to claim 9 , wherein said electronic device is a radio frequency amplifier and said load is an antenna.
12. A system according to claim 9 , wherein said network comprises a succession of variable resistances, some of them arranged serially between the electronic device and the load and others arranged parallel to the electronic device.
13. A system according to claim 9 , wherein each resistance is made in digital form with dedicated switches.
14. A system according to claim 9 , wherein the network comprises a resistance arranged serially between the electronic device and the load, a resistance arranged parallel to the electronic device, and a switch arranged parallel to the serial resistance and activatable when mismatching is not present.
15. A system according to claim 9 , wherein the first value of said ratio between the incident and reflected standing waves detected by said sensor belongs to a first circumference on a Smith chart, said first circumference being a place of points with said detected first value and being tangential to standardized and constant reactance and susceptance circumferences, and the second value of said ratio between the incident and reflected standing waves belongs to a second circumference on the Smith chart, said second circumference being a place of points with said second value and being tangential to the standardized and constant reactance and susceptance circumferences, said control circuit being suitable for varying the values of the resistances for transforming a point belonging to said first circumference in a point belonging to said second circumference moving on the standardized and constant reactance and susceptance circumferences on the Smith chart.
16. A system according to claim 15 , wherein said network comprises at least a resistance arranged serially between the electronic device and the load and at least a resistance arranged parallel to the electronic device, said control circuit is suitable for defining the values of said resistances in accordance with the following system:
{
1
r
s
+
V
+
1
r
p
=
1
Vr
1
r
s
+
1
/
V
+
1
r
p
=
Vr
,
having as a solution
{
r
s
=
V
2
-
1
·
(
(
Vr
2
-
1
)
·
(
V
2
(
Vr
2
-
1
)
+
4
V
*
Vr
-
Vr
2
+
1
)
+
(
Vr
2
+
1
)
·
V
2
-
1
)
2
(
V
2
*
Vr
+
V
(
1
-
Vr
2
)
-
Vr
)
r
p
=
V
2
-
1
·
(
Vr
2
-
1
)
·
(
V
2
(
Vr
2
-
1
)
+
4
V
*
Vr
-
Vr
2
+
1
)
+
(
1
-
Vr
2
)
·
(
V
2
+
1
)
2
V
(
Vr
2
-
1
)
.
where r s is the series resistance, r p is the parallel resistance, V is the first value of the ratio between the incident and reflected standing waves detected by the sensor and Vr is the second value of the ratio between the incident and reflected standing waves.
17. A method, comprising:
matching an impedance of a load of an electronic device, the matching including:
detecting a first value of a ratio between incident and reflected standing waves in transferring power from the electronic device to the load, the detecting including providing first and second signals substantially proportional to amplitudes of the incident and reflected standing waves; and
lowering said ratio between the incident and reflected standing waves to a second value that ensures the transfer of power from the electronic device to the load by varying values of resistances of an impedance network coupled between the electronic device and the load based on the first and second signals.
18. A method according to claim 17 , wherein said network of variable resistances comprises at least a resistance arranged serially between the electronic device and the load and at least a resistance arranged parallel to the electronic device.
19. A method according to claim 17 , wherein said network comprises a series resistance and a parallel resistance, wherein varying the values of the resistances includes defining the values of said resistances in accordance with the following system:
{
1
r
s
+
V
+
1
r
p
=
1
Vr
1
r
s
+
1
/
V
+
1
r
p
=
Vr
,
having as a solution
{
r
s
=
V
2
-
1
·
(
(
Vr
2
-
1
)
·
(
V
2
(
Vr
2
-
1
)
+
4
V
*
Vr
-
Vr
2
+
1
)
+
(
Vr
2
+
1
)
·
V
2
-
1
)
2
(
V
2
*
Vr
+
V
(
1
-
Vr
2
)
-
Vr
)
r
p
=
V
2
-
1
·
(
Vr
2
-
1
)
·
(
V
2
(
Vr
2
-
1
)
+
4
V
*
Vr
-
Vr
2
+
1
)
+
(
1
-
Vr
2
)
·
(
V
2
+
1
)
2
V
(
Vr
2
-
1
)
.
where r s is the series resistance, r p is the parallel resistance, V is the first value of the ratio, and Vr is the second value of the ratio between the incident and reflected standing waves.