JPH0827309B2 - Adaptive impedance mismatch detector system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a detector for detecting impedance mismatch between a transmission line and a load impedance. In particular, the present invention relates to impedance mismatch detection systems that process reflection coefficient magnitude information as well as reflection coefficient magnitude information as a basis for determining the presence of a mismatch.

In wireless electronics it is often useful to know if the transmission line is matched or not with the load impedance. A directional coupler circuit such as that shown in FIG. 1 can be used to make this determination. An example of this directional coupler is US Pat. No. 4,494, issued to Warren B. Bruene on January 8, 1985.
It is one of the parts in the 3,112 antenna tuner discriminator. The elements of this combiner circuit are such that when the RF transmission line through the combiner is terminated with a suitable load impedance of, for example, 50 ohms, the voltage drop across resistor R1 is divided by voltage divider C1.
The capacitance of C2 is chosen to be equal and in phase with the voltage across C2. When properly terminated as described above, the forward voltage Vf has a positive value. The voltage drop across the resistor R2 is the same as the voltage drop across the capacitor C2, but the phase is opposite. Since the termination is correct, there is no voltage reflected wave.
That is, the voltage Vr of the reflected wave is zero in magnitude. However, if the load impedance is not a suitable terminating resistor, 50 ohms in this example, a reflected voltage wave will result. Therefore Vr has non-zero magnitude. In this example, the resistances of the resistors R1 and R2 are equal and are considerably smaller than the impedance of the inductor L.

One of ordinary skill in the art will appreciate that the directional coupler can be used as a detector to determine when the load impedance is mismatched with the transmission line. The degree of mismatch is indicated by the magnitude of the reflected voltage wave Vr. The larger the mismatch, the larger the reflected voltage wave,
The voltage standing wave ratio (VSWR) increases accordingly.

As mentioned above, the directional coupler described above can be used to indicate when a mismatched load impedance is present. However, information about the characteristics of the load impedance, that is, whether it is capacitive or inductive,
No information is given as to whether it is resistant or a combination thereof. In other words, the directional coupler of Figure 1 provides no phase information about the impedance under test.

A Smith chart showing the load impedance is shown in FIG. In general, this Smith chart represents all the impedances that the load impedance can take. Those skilled in the art will use Smith charts to plot the load impedance in a manner that indicates the degree of resistance, capacitive, inductive, or their coupling of such impedances.

It can be seen that the load impedance in the specific region easily causes oscillation in a given RF power amplifier. The Smith chart of FIG. 2 includes a shaded area 10 which, for the purposes of this example, is defined to be one such unstable area. That is, area 10 of the Smith diagram represents the area that exhibits various values of load impedance that destabilize an amplifier coupled to such an impedance. The upper right parts of the area 10 of the Smith chart form an area 20 which represents the load impedance which results in stable amplifier operation. As seen in FIG. 2, the region 20 is generally circular in shape and includes a center 22. The ends of the region 20 bounding the unstable region 10 are called threshold circles 24 because the circle 24 represents the boundary between stable amplifier operation and unstable amplifier operation. Center 22 is also called the boundary center.

Prior to the detectors of the present invention, mismatch detectors determined that a particular load impedance was within or outside a bounding circle, such as bounding circle 30 described below centered on the origin of the Smith chart. We were able to. However, such conventional detectors address the problem of determining whether the load impedance is inside or outside a bounding circle, such as the bounding circle 24 centered on a point on the Smith diagram other than the origin. It wasn't.

It is recalled that the directional coupler only determines the magnitude of the reflected voltage signal resulting from the particular load impedance. Therefore, the combiner can be used to determine if a particular load impedance produces a VSWR that exceeds a predetermined value. That is, the coupler has a boundary circle with a certain load impedance centered on the origin,
For example, it is used to determine if it is within or outside the bounding circle 30 of a VSWR of 2.5 to 1. The center or origin of the Smith chart represents a perfectly matched load. As you move away from the center of the Smith chart in any direction, the degree of misalignment,
And the magnitude of VSWR increases. For example, all points on the bounding circle 30 represent various mismatched load impedances that result in a VSWR of 2.5-1. It is noted that the boundary circle 30 of VSWR of 2.5 to 1 touches the unstable region 10 in the shaded area. It is again noted that some mismatch will cause some VSWR, but many impedance mismatches will not cause instability problems. In many cases, only the load impedance of some area, such as the shaded area 10, will cause instability. As will be explained below, conventional directional coupler detector circuits have limited application in these situations. This is because it is not possible to determine if there is an impedance within a bounding circle having a center other than the center of the Smith diagram.

With respect to FIG. 2, it is noted that the shaded unstable region 10 touches the circle 30. Also note that the center of circle 30 is at the origin of the Smith chart. Now assume that the directional coupler of FIG. 1 is used to detect when the load impedance is high or low and such load impedance no longer exists within circle 30. In other words, such directional couplers are used to determine when the load impedance is forced to exceed a given VSWR (eg 2.5-1). The appearance of this condition can be used to trigger the appropriate amplifier stabilization circuit. For circuits that can achieve stabilization in this manner, see “Stabillized” published on Harvey N. Turner, Jr., March 27, 1984.
See US Patent No. 4,439,741 entitled "High Efficiency Radio Frequency Amplifier" and assigned to Motorola, Inc., the assignee of the present invention. The disclosure of US Patent No. 4,439,741 is incorporated herein by reference. There is.

By examining the Smith diagram of FIG. 2, when the directional coupler of FIG. 1 is used as a mismatch detector, the stabilizing circuit is activated at each point outside the boundary circle 30 and the shaded area tangent to it. It is clear that the amplifier protection in the unstable region 10 must be ensured. Depending on the application, such an arrangement may be useful for many load impedance values where a power consuming stabilizing circuit is not actually needed, i.e., load impedance values outside the shaded instability region 10 and not within the circle 30. It may be undesirable and inefficient because it is activated. This problem arises because the conventional mismatch detectors were limited to determining if a particular load impedance was in a bounding circle centered on the origin of the Smith chart. In contrast to conventional mismatch detectors, the present invention allows the load impedance to be in a region of values that lies outside the bounding circle with the center on the Smith chart, which can be other than the normalized origin of the Smith chart. It is about detecting whether or not.

The features of the invention believed to be novel are set forth in the appended claims. However, the invention itself, as well as its structure and method of operation, may best be understood by reference to the following description in view of the accompanying drawings.

DISCLOSURE OF THE INVENTION One object of the present invention is to detect whether a particular impedance has an impedance value outside a bounding circle centered on a point on the Smith chart that need not be the center or origin of the Smith chart. An adaptive impedance mismatch detector system is provided.

Another object of the present invention is to provide an adaptive impedance mismatch detector system capable of changing the center of the Smith chart boundary circle in response to changes in circuit operating conditions.

Yet another object of the present invention is to provide an adaptive impedance mismatch detector system capable of changing the radius of the Smith chart boundary circle in response to changes in circuit operating conditions.

Another object of the present invention is to provide an adaptive impedance mismatch detector system that corrects for the deficiencies of the other mismatch detectors described above.

In accordance with one embodiment of the present invention, an impedance mismatch detector system is provided for detecting impedance mismatch between first and second impedance exhibiting circuits coupled thereto.
The system has a detector circuit that determines if there is a first impedance indicating circuit within a selected Smith chart boundary circle centered at a point on the Smith chart other than the origin of the Smith chart. The system further includes a radius control circuit that changes the radius of the bounding circle in response to changes in operating conditions or parameters.

In accordance with another embodiment of the present invention, an impedance mismatch detector system is provided to detect an impedance mismatch between the first and second impedance indicating circuits coupled thereto. The system has a detector circuit that determines if the impedance of the first impedance indicating circuit is or not within a selected Smith chart boundary circle centered at a point on the Smith chart other than the origin of the Smith chart. . The system further includes a central control circuit that changes the position of the center of the bounding circle on the Smith chart in response to changes in operating conditions or parameters.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagram of a directional coupler.

FIG. 2 is a Smith chart graph showing the load impedance region that can be detected by the conventional directional coupler and the impedance region that can be detected by the present invention.

FIG. 3 is a schematic circuit diagram of one embodiment of the detector of the present invention.

FIG. 4 is a schematic circuit diagram of another embodiment of the detector of the present invention.

FIG. 5 is a block diagram of an adaptive impedance mismatch detector system that uses the impedance mismatch detector of FIG.

FIG. 6 is a Smith chart graph showing a first bounding circle with a predetermined center and radius used by the mismatch detector system.

FIG. 7 shows a predetermined center different from the boundary circle of FIG.
3 is a Smith chart graph showing a second boundary circle having a radius.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 3, one embodiment of the mismatch detector of the present invention is shown as detector 10. The detector 10 has a node 22,
It is used to detect the presence of an impedance mismatch between the transmission line or other device connected to the port 20 formed by 24 and the load impedance 30 coupled to the detector output port 35 as shown. Node 24 is grounded. Node 22 is coupled to load impedance 30 by induct 40. The remaining end of impedance 30 is grounded. In this particular embodiment, the induct 40 is formed by a conductive line running through the center of the toroid 50. In addition, the inductor 40 and toroid 50 are donut shaped (to
roidal) The transformer 60 is configured, the induct 40 is the primary winding,
The toroid 50 becomes the secondary winding. 1.5 μH at VHF frequency
It has been found that the inductance of is a satisfactory in-inductance value for the toroid inductor 50. The secondary winding of the donut transformer 60 has two ends, shown as ends 61,62. The winding end 61 is coupled to one end of the variable impedance element 70. Winding end 62 is coupled to one end of variable impedance element 80. As shown in FIG. 3, the remaining ends of impedances 70, 80 are connected. The variable impedance elements 70 and 80 include control terminals 72 and 82, respectively. Supplying appropriate control signals, which will be described later, to the control terminals 72 and 82, the impedance element 70
Select specific impedances that each match 80. The node formed between winding end 61 and impedance element 70 is shown as node 75 at which voltage V1 is measured, while the node formed between winding end 62 and impedance element 80 is at voltage V2. Shown as node 85 being measured.

The common contact between impedance elements 70 and 80 is grounded via inductor 90. The inductor 90 is formed by a conductive wire passing through the center of the toroidal inductor 100.
In addition, the inductor 90 and toroid 100 are the donut transformer 1
05, where the toroid 100 is the primary winding and the inductor 90 is the secondary winding. Such a donut transformer 10
The five primary winding 100 includes winding ends 102, 104. Winding end 102 is coupled to node 22 at the input of mismatch detector 10. The remaining winding ends 104 are grounded as shown. The donut transformer 105 is substantially the same as the transformer 60.

When port 20 is driven with RF energy, the ratio | V2 / V1 |
Gives an indication of whether the load impedance 30 is inside or outside the bounding circle 24. The following description details how this impedance mismatch determination is made.

For each of the equations and relations listed in the following explanation, L
Note that the inductor ₄₀ , ₅₀ , which represents the inductor as ₄₀ , L ₅₀ , constitutes a toroidal transformer 60. The coupling coefficient between the inductors 40 and 50 is indicated by K ₆₀ . The doughnut-shaped transformer 105 is composed of inductors ₉₀ and ₁₀₀ having inductances L ₉₀ and L ₁₀₀ , respectively. Coupling between inductors 40 and 100 is a factor K
Shown at ₁₀₅ . Impedance elements 70, 80 and transformers _{60, 105} meet the following conditions: 1) L ₅₀ = L ₁₀₀ 2) L ₄₀ = L ₉₀ 3) L ₆₀ = L ₁₀₅ 4) | Z ₇₀ | >> ωL ₄₀ (1- K ₆₀ ² ) 5) | Z ₈₀ | >> ωL ₄₀ (1-K ₆₀ ² ) 4) | Z ₇₀ + Z ₈₀ | << ωL ₅₀ Here, Z ₃₀ is the impedance of the load impedance 30. For convenience, let Z ₃₀ be Z _L.

Further, in the case of 8) Z ₇₀ = Z ₈₀ = Z ₀ (where Z ₀ is the characteristic impedance of the transmission line coupled to the impedance mismatch detector 10), Equation 7) is 9) | V2 / V1 | = | (Z _L −Z ₀ ) / (Z _L −Z ₀ ) | = ρ. This represents the magnitude of the reflection coefficient ρ (low).

Now, if the impedance is in the normalized form, ie 10) z = Z / Z ₀ , then 11) z ₇₀ = r ₇₀ + jx ₇₀ 12) z ₈₀ = r ₈₀ + jx ₈₀ .

Ρ plane (Smith chart) expressed in the normalized form of Equation 7)
It can be seen that the boundary circle is a circle having the center (u ₀ , v ₀ ) and the radius P expressed as follows.

13) u ₀ = (1-r ₀ ² -x ₀ ² + R ₀ ² ) / (1 + r ₀ ² + 2r ₀ + x ₀ ² + R ₀ ² ) 14) v ₀ = 2x ₀ / (1 + r ₀ ² + 2r ₀ + x ₀ ² + R ₀ ² ) 15) P = 2R ₀ / (1 + r ₀ ² + 2r ₀ + x ₀ ² + R ₀ ² ) 16) ρ = u + jv 17) r ₀ =-(T ² r ₇₀ + r ₈₀ ) / (T ² _{-1) 18) x 0 = -} (T 2 x 70 + x 80) / (T 2 -1) 19) R 0 2 = [T / (T 2 -1)] 2 [(r 70 + r 80) 2 + (X ₇₀ + x ₈₀ ) ² ] Further 20) If z ₇₀ = 1 + j0, then 21) v ₀ = 2x ₈₀ / [(1 + r ₈₀ ) ² + x ₈₀ ² ] 22) u ₀ = (r ₈₀ ² + x ₈₀ ² -1 _{) / [(1 + r 80} ) 2 + x 80 2] 23) P = 2T / [(1 + r 80) 2 + x 80 2] becomes ^1/2. One of ordinary skill in the art using the Smith chart will understand that equations 21), 22) represent the impedance coordinates of the Smith chart. Thus, for Z ₇₀ = 1 + j0, the center of the bounding circle is at r ₈₀ + jx ₈₀ , as plotted in the Smith chart.

In accordance with the present invention, the following description details the selection of various detector circuit parameters necessary to achieve the bounding circle 24 as shown, for example, in FIG. The normalized impedance of the variable impedance element 70 is selected as follows.

24) Z ₇₀ = 1 + j0 Next, as shown in Fig. 2, plot the center point of the desired boundary circle on the Smith chart. In this example, the center is shown as center 22 and is located at 1 + j2. To achieve this desired centered boundary circle, the impedance z ₈₀ of the impedance element 80 is chosen to be equal to its center value, 1 + j2 in this example.

25) Note that z ₈₀ = r ₈₀ + jx ₈₀ . Further, when rewriting the equation 23), the boundary i.e. trigger ratio T is, 26) T = (P / 2) is given by ^{_{[(1 + r 80) 2}} + x 80 2] 1/2, where P is the boundary circle Represents the desired radius.

The trigger ratio T is defined as the ratio of | V2 | and | V1 | required to achieve a particular bounding circle with a selected radius. For example, as shown in FIG. 2, when z ₈₀ = 1 + j2 and P = 1.15, the trigger ratio is 1.6 according to equation 26). For the boundary circle 24 and the shaded area 10 outside this circle, if the ratio of | V2 | and | V1 | is less than T, the load impedance 30 is
Has an impedance value within. In other words, the value of V2 is
If it is less than 1.6 times the value of V1, the load impedance is 3
0 is located within the boundary circle 24 of the Smith chart. Conversely, | V2 | and |
If the ratio of V1 | is greater than T, the load impedance 30 will have an impedance value outside the bounding circle 24 and will exhibit an undesired impedance value. In other words, if the value of V2 exceeds 1.6 times the value of V1, the load impedance 3
0 is in the shaded area 10 of the Smith chart. Thus, the ratio of the output voltage | V1 |, | V2 | of the mismatch detector 10 can be an indication of the impedance of the impedance element 30, that is, whether this impedance is inside or outside the boundary circle 24. Recognize.

FIG. 4 shows another embodiment of the mismatch detector according to the present invention.
Shown as 110. Detector 110 includes an impedance mismatch between a transmission line or other device connected to port 120 formed by nodes 122, 124 and a load impedance 130 coupled to detector output port 135 as shown. Used to detect presence. Node 124 is grounded. Node 122 is coupled to load impedance 130 by inductor 140 as shown in FIG. In this particular embodiment, the inductor 140 is formed by a conductive line passing through the center of the toroid inductor 150. Further, the inductor 140 and the toroid 150 form a donut transformer 160, the inductor 140 serves as its primary winding, and the toroid 150 serves as its secondary winding. To use at VHF frequency, 1.
It was found that the inductance of 5 μH is a value that should be satisfied as the inductance of the toroid inductor 150.
The secondary winding 150 of the donut transformer 160 includes two ends labeled 161, 162. Winding end 161 is coupled to one end of variable impedance element 170. The node thus formed between winding end 161 and impedance element 170 is designated node 175, and the voltage there is designated V3. Winding end 162 is coupled to one end of variable impedance element 180. The node thus formed between winding end 162 and impedance element 180 is designated node 185, and the voltage there is designated V4.

The remaining end of the impedance element 170 is the inductor 190
Grounded through. Inductor 190 is formed by a conductive wire passing through the center of toroid inductor 200. The inductor 190 and the toroid 200 constitute a donut transformer 205, and the toroid 200 is the primary winding and inductor.
190 is the secondary winding. It has been found that for VHF, an inductance of 1.5 μH is a satisfactory value for the inductance of the primary winding 200. This donut transformer 205
Primary winding 200 includes winding ends 202, 204. Winding end 202 is coupled to node 122 at the input of mismatch detector 110. The remaining winding ends 204 are grounded as shown.

The remaining end of impedance element 180 is inductor 210
Grounded by. Inductor 210 is formed by a conductive wire passing through the center of toroid inductor 220. Further, the inductor 210 and the inductor 220 form a donut transformer 230, in which the inductor 210 is the primary winding,
The toroid 220 becomes the secondary winding. It has been found that a value of 1.5 μH is suitable for VHF.
The secondary winding of the donut transformer 230 includes winding ends 222,224. The winding end 222 is connected to the inductor 140 as shown in FIG.
And is coupled to one end of impedance element 130. Winding end 224 is grounded and impedance element 130
To be joined to the rest of the.

When port 120 is driven with RF energy, the ratio | V4 | / | V
3 | gives an indication of whether the load impedance 130 is inside or outside the bounding circle 24.

In the mismatch detector embodiment 110 of FIG. 4, the impedance of the load impedance 130 of FIG.
When located at 4, it is obtained from Example 10 of the detector of FIG. 3 by the conversion of 27) | V3 | = | V4 |. The magnitude of the radio frequency (RF) voltages V3, V4 as in Eq. 26) is usually obtained by processing the V3, V4 voltages using non-ideal diodes as envelope detectors. By creating the desired boundary when | V3 | = | V4 |
3, dependency on absolute level of V4 is removed.

The values of the components of the detector 110 are displayed as follows for convenience of description below. The inductors 140, 150 of the transformer 160 have an inductance of L ₁₄₀ , L ₁₅₀ , respectively, and are coupled together by a mutual inductance M ₁₆₀ . The inductances ₁₉₀ , ₂₀₀ of the transformer 205 have an inductance of L ₁₉₀ , L ₂₀₀ respectively and are coupled to each other by a mutual inductance M ₂₀₅ . Inductor 210, 22 of transformer 230
0 has the inductances of L ₂₁₀ and L ₂₂₀ , respectively, and are mutually coupled by the mutual inductance M ₂₃₀ . Then, 28) | V4 / V3 | = P ₀ | Z ₁₃₀ −P ₂ Z ₁₈₀ | / | Z ₁₃₀ −P ₁ Z ₁₇₀ |. Where 29) P ₁ = (M ₁₆₀ / M ₂₀₅ ) (L ₂₀₀ / L ₁₅₀ ) 30) P ₂ = (M ₁₆₀ / M ₂₃₀ ) (L ₂₂₀ / L ₁₅₀ ) 31) P ₀ = (M ₂₃₀ / M ₂₀₅ ) (L ₂₀₀ / L ₂₂₀ ) = P ₁ / P ₂ Detector of FIG. 3 as shown in the Smith diagram of FIG.
From the description of the embodiment of _{10, T = 1.6, z 70} = 1 + j0, z 80 =
It is recalled that it is 1 + j2. Now, let's use this example as a detector
Turning to 110 examples. For the detector 10 embodiment, 32) | V2 / V1 | = 1.6 (at the boundary), but now 33) | V4 / V1 | = 1 (at the boundary) P ₀ = 1 / 1.6, P ₁ = _1, P ₂ = 1.6 Then, 34) by setting the _{z 170 = 1 + j0 35)} z 160 = 1 / 1.6 + j2 / 1.6 = 0.625 + j1.25, 36) | V4 / V3 | = (1 / 1.6) | [Z ₁₃₀ − (1 + j2)] / (Z ₁₃₀ +1) | Therefore, when the load impedance 130 is on the circle 24, 37) | V4 / V3 | = 1 38) | V4 | / | V3 | The load impedance z ₁₃₀ is located within the shaded area 24 in FIG. Note that the boundary center of the Smith chart is still at 1 + j2, even with the normalized impedance z ₁₈₀ = 0.625 + j1.25.

From the equations P ₁ and P ₂ , three donut transformers 160, 205,
230 relationships are obtained. Since P ₁ = 1
205 will be the same. The following equations relating the coupling coefficient for self-inductance and mutual inductance, 39) M ₁₆₀ = K ₁₆₀ (L ₁₄₀ / L ₁₅₀ ) ^1/2 40) M ₂₃₀ = K ₂₃₀ (L ₂₁₀ / L ₂₂₀ ) ^1/2 Substituting into the formula for P ₂ , the following design relation 41) P ₂ = (K ₁₆₀ / K ₂₃₀ ) (L ₁₄₀ / L ₂₁₀ ) ^1/2 (L ₂₂₀ / L ₁₅₀ ) ^1/2 is obtained. In the example under consideration, P ₂ = 1.6. Keeping the other transformer parameters the same, L ₁₄₀ = 10n
With H, L ₂₁₀ = 3.9 nH, the desired result described above is obtained.

In summary, the output voltage V4, V3 of the mismatch detector 110 is an indication of the impedance of the impedance element 130, ie whether this impedance is inside or outside the bounding circle 24. When the ratio of | V4 | and | V3 | is smaller than T (T = 1 in this example), the impedance element 130 has an impedance value within the boundary circle 24. In other words, the value of V4 is V3
Is less than 1.0 times the value of
The impedance of is in the boundary circle 24 of the Smith chart. Conversely, when the ratio of | V4 | and | V3 | is greater than T, the load impedance 30 has an impedance value outside the bounding circle 24, exhibiting an undesirable impedance value. In other words, when the value of V4 exceeds 1.0 times the value of V3, the impedance of the impedance element 130 is outside the boundary circle 24 and within the shaded area 10 of the Smith chart.

FIG. 5 shows an adaptive mismatch detector system using the mismatch detector 10 of FIG. Those skilled in the art will readily appreciate that the detector 110 of FIG. 4 can also be used as the mismatch detector of the mismatch detector system of FIG. Fifth
The detector system shown has some elements in common with the detector circuit of FIG. 3, with like elements given the same reference numbers. The detector system comprises a radio frequency amplifier 300 having an input 300A to which a radio frequency signal is applied for amplification.
Have. The appropriate power supply voltage is coupled to the voltage supply input 300B. The amplified radio frequency signal thus generated at the amplifier output 300C is coupled to the input port 20 of the mismatch detector 10. For this embodiment a 50 ohm transmission line amplifier
Used to couple 300, detector 10 and impedance 30 (discussed below).

Impedance element 30, eg, load impedance, is coupled to output port 35 of mismatch detector 10 as shown. The impedance of this impedance element 30 is tested by the mismatch detector 10 to determine whether it is within or outside the selected bounding circle. The mismatch detector system of FIG. 5 has the ability to change the position and radius of the bounding circle of the Smith chart as a function of changing circuit conditions and parameters, which will be described below. This is a highly desirable feature of mismatch detection systems. Because under certain operating conditions the particular impedance value of the impedance element 30 does not cause any problems in circuit operation, but under other operating conditions (e.g. temperature, supply voltage, increase in current or drive level, or operating frequency). The same impedance value may cause undesired effects in the associated circuit coupled to it.

The detector system is capable of sensing circuit conditions and parameters for changes in the circuit coupled to or away from the mismatch detector 10 at a sensing input 310E.
And a detection circuit 310 having. In the embodiment shown in FIG. 5, the sensing circuit 310 is coupled to the amplifier 300 in such a manner that it can sense the operating temperature of the amplifier 300. Those skilled in the art will appreciate that a thermocouple (not shown) or similar device may be conveniently used to provide such temperature information to the sensing circuit 310. Detection circuit 31
0 has sense outputs 310A and 310B coupled to mismatch detector control terminals 72 and 82, respectively. The control signal thus supplied to the mismatch detector 10 determines the impedance value of the variable impedance elements 70 and 80 in the detector 10. It is recalled that the impedance values of impedance elements 70 and 80 determine the center of the bounding circle represented by detector 10. Thus, it can be seen that in this embodiment of the invention, the position of the bounding circle on the Smith chart is controlled by the temperature of amplifier 300. That is, the temperature information sensed by sensing circuit 310 causes control terminals 72 and 82 to generate control signals that select the impedance values of impedance elements 70 and 80, respectively, thereby determining the center of the boundary circle.

The present invention is not limited to sensing temperature and controlling the position of the Smith chart boundary circle in response. Sensing temperature operating conditions is merely exemplary. For those skilled in the art,
The sensing circuit 310 includes RF drive level supplied to the amplifier input 300A, power supply voltage supplied to the amplifier 300, current consumed by the amplifier 300 or other device, operating frequency of the amplifier 300, temperature of the load 30, etc. It will be appreciated that it can be used to sense operating conditions and circuit parameters. In this case, such changes in operating conditions and parameters are responsive to impedance element 70 and
Used to determine the center of the Smith chart boundary circle by varying the value of 80. Two examples of such a boundary circle center control including Smith chart will be described later.

It is recalled that nodes 75, 85 are locations within the mismatch detector 10 where the voltages V1, V2 are measured, respectively. Also,
It should be recalled that the ratio of the voltages V1 and V2 gives information about whether the impedance of the impedance element 30 is inside or outside the selected Smith chart boundary circle. Nodes 75 and 85 are coupled to envelope detectors 320 and 330, respectively. Diodes are convenient to use as such an envelope detector. Since the envelope detectors 320 and 330 detect the envelopes of the V1 and V2 RF signals given thereto, the output signals of the envelope detectors 320 and 330 are the absolute value or magnitude of the input signal, that is, FIG. Absolute value of V1 (| V
1 |) and the absolute value of V2 (| V2 |).

Outputs of envelope detectors 320 and 330 are bypass capacitors.
Grounded by 340 and 350. The output of envelope detector 320 is coupled to the input 360A of electronically activatable voltage divider 360. Output 360B of voltage divider 360 is coupled to negative terminal 400A of comparator 400. In this embodiment, the comparator 400 is configured to turn on when the impedance 30 is outside the bounding circle of the selected Smith chart. Voltage divider 400
The degree of partial pressure or pressure reduction caused by is determined by the control signal applied to control terminal 360C. One convenient way to look at the voltage divider 400 is to have a potentiometer style where the resistors R1, R2 are represented as shown in FIG. 5 and the values of R1, R2 are determined by the position of the wiper corresponding to the output 360B. To consider the mechanical aspects of

The second voltage divider circuit 370, which is substantially the same as the voltage divider circuit 360, has an output terminal 370B of which is the positive terminal 400A of the comparator 400.
Is joined to. Input 370A, output 370B of voltage divider 370,
The control terminal 370C and the resistors R1 'and R2' are
Corresponds to A, output 360B, control terminal 360C, and resistors R1 and R2. Voltage divider input terminal 370A is coupled to the output of envelope detector 330.

In summary, the voltage dividers 360, 370 are for reducing the voltage level of the | V1 |, | V2 | signals to the desired degree before applying such signals to the inputs 400A, 400B of the comparator 400. . Again, the ratio of | V1 | and | V2 | signals is impedance 30
It is recalled to have information about whether is inside or outside the selected bounding circle. Resistance part (R1, R2,
Changing the values of R1 ', R2') causes a change in the radius of the selected Smith chart boundary circle. This is because the point at which the comparator 400 is triggered on will change due to such changes.

Previously, it was shown that in other embodiments of the present invention the sensing circuit 310 senses the temperature of the amplifier 300, or other operating conditions and parameters. Sensing circuit 310 has outputs 310C, 310D coupled to control terminals 360C, 370C, respectively. To what extent the | V1 |, | V2 | voltages should be divided or reduced in response to sensed temperature, other operating conditions or other parameters before being applied to the input of the comparator 400. The detection circuit 310 generates control signals for instructing the voltage dividers 360 and 370 at the outputs 310C and 310D. In this way, the radius of the selected bounding circle is changed with the sensed temperature or other parameter. Considering that the radius of the bounding circle can vary with selected operating conditions or other parameters, when the impedance of impedance element 30 is shown to be outside the bounding circle defined by the current radius and center. At any time, it can be seen that the output 400C of the comparator 400 turns on. Thus, an undesired impedance mismatch is indicated.

The output 400C of the comparator 400 is coupled to the input of a condition control circuit 410 which turns on when the output 400C goes high. In this embodiment, condition control circuit 410 is coupled to amplifier 300. One condition control circuit that can be used as the control circuit 410 is the above-mentioned US Pat. No. 4,439,741.
It is the stabilizing circuit described in No. In this case, a high comparator output 400C indicates an unwanted mismatch and the stabilization circuit is turned on for the duration of the mismatch and the amplifier 300
Stabilize. The present invention also controls other condition control circuits by the control circuit 41.
Intended to be used as 0. For example, one of the present invention
In the exemplary embodiment, condition control circuit 410 is a cooling device that is energized by comparator output 400C going high during an undesired impedance mismatch. Such a cooling device serves to cool amplifier 300 or other associated circuitry for the duration of the mismatch. Also, known voltage-current protection circuits can be used as condition control circuit 410 to protect amplifier 300 or other devices from unwanted high voltage and current levels during periods of unwanted impedance mismatch.
As mentioned above, the condition control circuit 410 need not be coupled to the amplifier 300. Condition control circuit 410 is coupled to other circuitry connected to or remote from detector 10 to control one or more conditions, one or more parameters of such other circuitry. For example, in one embodiment, condition control circuit 410 is an electronically tunable circuit that is coupled to impedance 30 under test. Impedance 30 (as indicated by the higher comparator output 300C)
When presenting a value outside the bounding circle 24, such an electronically tunable circuit couples an appropriate amount of inductive or capacitive reactance into the impedance 30 to determine the combined impedance of such an element (comparator output). Place it within the bounding circle 24 (as indicated by the lower 300C). That is, such an electronically tunable circuit tunes until the comparator output 300C goes low. Those skilled in the art will appreciate that other condition control circuits could simply be used in addition to the circuits described above.

Two examples are shown in which the mismatch detection system shows different Smith chart boundary circles with different centers and radii. Thus, an aspect is presented in which the mismatch detection system exhibits a first bounding circle in response to a predetermined operating condition or parameter, and then a second bounding circle in response to another operating condition or parameter. Be done.

For the purposes of the first example, assume that the sensing circuit 310 of FIG. 5 is a temperature sensing circuit that senses the operating temperature of the amplifier 300. Also, when the amplifier 300 is operating at normal temperature, eg 40 ° C., the Smith chart boundary circle 420 has a center 430 at 1 + j2 and a radius P of 1.15, as measured on the Smith chart reflection coordinate scale. , It is desired to use a mismatch detector system. These center and radius values are plotted on the Smith chart of FIG. To allow the impedance mismatch detection system to use such a bounding circle 420, the sensing circuit 310 outputs 310A and 3A.
Variable impedance 7 by generating appropriate control signal to 20B
0, ₈₀ (z ₇₀ , z ₈₀ ) indicate 1 + j0, 1 + j2, respectively. Substituting these values into the trigger ratio equation 26) reveals that the trigger ratio T = 1.6. In order to achieve the desired bounding circle 420 described above, the comparator 400 must trigger on when | V2 | = 1.6 | V1 |.
To cause this, the resistor sections of the voltage divider 360, 370 are appropriately adjusted so that no voltage dividing action occurs in the voltage divider 360. Thus, the total voltage | V1 | reaches the comparator input 400A,
In the voltage divider 370, R2 ′ / (R1 ′ + R2 ′) = 1 / 1.6.
Therefore, | V2 | = 1.6 |
At V1 |, the voltages applied to comparator inputs 400A and 400B are equal and comparator 400 turns on. Of course, if the above adjustment of the resistance part of the voltage divider 360, 370 is desired,
It may be done manually. However, in the embodiment shown in FIG. 5, detected operating conditions (eg, temperature of 40 ° C.)
In response, the sensing circuit 310 produces a suitable control signal at the outputs 310C, 310D, causing the resistive portion of the voltage divider 360, 370 to have a bounding circle with a radius which appears to be suitable for such operating conditions.
Allow 420 to have the resistance needed to present an impedance mismatch system.

Thus, during the mismatch test, the impedance, i.e., impedance 30, shows an acceptable impedance if it lies within the bounding circle 420, but
If the action of the comparator 400 reveals that the impedance 30 is not within such a boundary circle, the condition control circuit
410 is turned on, changing selected operating conditions of amplifier 300 and stabilizing amplifier 300, for example, as described above.

Now assume that the temperature operating conditions of the amplifier 300 increase such that the first bounding circle 420 shown in FIG. 6 is no longer suitable. For example, as the amplifier temperature increases to a higher temperature, eg, 75 ° C., the load impedance value of impedance 30, which previously did not cause any stability problems, now attempts to destabilize amplifier 300. A second Smith chart boundary circle 440, shown in FIG. 7, having a radius smaller than the boundary circle 420 and a different center 450 is now appropriate. Boundary circle 440 has a center 450 located at 1 + j1 where the reflection coefficient scale was measured on the Smith chart and a radius of 0.8.

In order for the impedance mismatch detection system to use such a bounding circle 440, the sensing circuit 310 outputs 31
0A, 320B generates an appropriate control signal, and the variable impedance 70, 80 to show the impedance of 1 + j0, 1 + j1
Instruct (z ₇₀ , z ₈₀ ). These values are the trigger ratio equation
By substituting in (26), it can be seen that the trigger ratio T = 0.89. Therefore, the desired bounding circle 440 described above
To achieve, comparator 400 must trigger on when | V2 | = 0.89 | V1 |. In order to cause this, the resistance part of the voltage divider 360, 370 is R2 /
Since (R1 + R2) = 0.89, the voltage divider 370 does not perform any voltage dividing operation and is appropriately adjusted so that the total voltage | V1 | reaches the comparator input 400B. Thus, by such a voltage dividing operation, when | V2 | = 0.89 | V1 |, the voltages supplied to the comparator inputs 400A and 400B become equal, and the comparator 400 turns on. The above adjustment of the resistive portion of the voltage divider 360, 370 may be done manually if desired. However, in the embodiment shown in FIG. 5, changed sensing operating conditions (eg,
Sensing circuit 310 outputs 310
Appropriate control signals are generated by C and 310D so that the resistances of the voltage dividers 360 and 370 have values such that R2 / (R1 + R2) = 0.89. Thus, the mismatch detection system will use the boundary circle 440 shown in FIG.

It can be seen that, when the temperature is increased (FIG. 7), the center of the boundary circle is changed and the radius of the boundary circle is decreased, as compared with the previous case (FIG. 6). Eventually, a small number of impedance values will be allowed for the impedance during the mismatch test, i.e. impedance 30. Correspondingly, a small number of values of impedance
Enter within 440. This is because the amplifier 3
It can be said that the stability of 00 becomes more dangerous and more value of the load impedance 30 causes the potential stability problem. Of course, other amplifiers can cause instability problems at low temperatures. Those skilled in the art will appreciate that the present invention can be modified to accommodate such situations.

So far, impedance values outside the bounding circle have been shown as unacceptable values, but this is merely a matter of practice. Impedance value within the boundary circle is acceptable,
It is possible to imagine a situation where the impedance inside and outside the boundary cannot be tolerated.

The description so far has been for impedance mismatch detectors and adaptive impedance mismatch detector systems using such detectors. The detector has the advantage of detecting if a particular impedance has a value outside the bounding circle centered on a point on the Smith chart which may be other than the center or origin of the Smith chart. When used in connection with the mismatch detector system described above, the detector operates in an adaptive manner. That is, the mismatched load impedances of different selected regions can be detected when properly directed as described above.

While only certain desirable features of the present invention have been illustrated, many variations and modifications will be apparent to those skilled in the art. Therefore, the claims should be understood to include all variations and modifications that are within the true spirit of the invention.

Claims (3)

[Claims] 1. An impedance mismatch detector for detecting an impedance mismatch between a first impedance indicating circuit (30) and a second impedance indicating circuit (20) coupled thereto, comprising: The first and second magnitudes change relative to each other depending on whether the impedance of the impedance indicating circuit (30) is inside or outside the selected Smith chart boundary circle.
Voltage (V ₂ and V ₁ or V ₄ and V ₃ ) of the first impedance indicating circuit (30) is selected and the impedance of the first impedance indicating circuit (30) is selected by comparing the magnitudes of the first and second voltages. Circuit means (10) for determining whether it is inside or outside the Smith chart boundary circle, the boundary circle having a center at a position other than the origin of the Smith chart, and the first and second voltage ( V ₂ and V ₁ or V ₄ and V ₃ ) are obtained with respect to the center of the boundary circle, whereby the first impedance indicating circuit (3
The impedance mismatch detector is characterized in that the presence of impedance mismatch is detected when the impedance of 0) is outside the Smith diagram boundary circle. 2. An impedance mismatch detector system for detecting impedance mismatch between a first impedance indicating circuit (30) and a second impedance indicating circuit (20) coupled to the first impedance indicating circuit (30). First and second magnitudes change relatively depending on whether the impedance of the impedance indicating circuit (30) is inside or outside the selected Smith chart boundary circle
Voltage (V ₂ and V ₁ or V ₄ and V ₃ ) of the first impedance indicating circuit (30) is selected and the impedance of the first impedance indicating circuit (30) is selected by comparing the magnitudes of the first and second voltages. A detector circuit means (10) for determining whether it is inside or outside the Smith chart boundary circle, said boundary circle having a center at a position other than the origin of the Smith chart and said first and second The voltage (V ₂ and V ₁ or V ₄ and V ₃ ) is obtained relative to the center of the bounding circle and is further coupled to the detector circuit means and is responsive to a predetermined control signal the radius of the bounding circle. An impedance mismatch detector system comprising radius control circuit means (360, 370, 400) for controlling. 3. An impedance mismatch detector system for detecting an impedance mismatch between a first impedance indicating circuit (30) and a second impedance indicating circuit (20) coupled to the first impedance indicating circuit (30), wherein First and second magnitudes change relatively depending on whether the impedance of the impedance indicating circuit (30) is inside or outside the selected Smith chart boundary circle
Voltage (V ₂ and V ₁ or V ₄ and V ₃ ) of the first impedance indicating circuit (30) is selected and the impedance of the first impedance indicating circuit (30) is selected by comparing the magnitudes of the first and second voltages. Detecting circuit means (10) for determining whether it is inside or outside the Smith chart boundary circle, said boundary circle having a center at a position other than the origin of the Smith chart, and said first and second voltages. (V ₂ and V ₁ or V ₄ and V ₃ ) is obtained as to the center of the boundary circle, and is further coupled to the detector circuit means and is responsive to a predetermined control signal to define the boundary on the Smith diagram. An impedance mismatch detector system comprising central control circuit means (310) for controlling the position of the center of the circle.