JPH0449301B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to the method of converting, by means of an electrical network, information on the value of a radio frequency impedance appearing at a port of the network into at least one desired locus in a complex impedance plane. This relates to a related method.

In this case, the electrical network is, for example, a combination of an antenna and an antenna tuning unit, the antenna tuning unit having two ports, one of which is connected to the antenna (which serves as a source of radio frequency signals). ), and the other port would like to be able to obtain information about the impedance that appears due to the above combination. The invention can be used to match antennas to radio receivers and transmitters.

[Conventional technology]

Methods for performing such alignment are already well known. For example, U.S. Pat. No. 3,919,644 describes an automatic antenna combiner for matching an antenna to a transmitter, in which a series of arrangements are made that connect the transmitter to a matching network and connect it to the antenna. The current and voltage components of the signal passing through are
The real part of the impedance or admittance sensed by the pickup and presented to the transmitter is detected and the matching network is controlled thereby. The signals in the above series of arrangements are the result of radio frequency energy provided by a transmitter. That patent discloses an automatic antenna coupler that senses and controls the current and voltage components of radio frequency energy provided by a transmitter.

In addition, British Patent Specification No. 1565166 (US Patent No. 4283794 is also equivalent) describes that the process of obtaining information on the radio frequency impedance of a circuit network is
It is stated that a respective transducer is used to inject a radio frequency current and a radio frequency voltage and the resulting signal is detected by a radio receiver, if the circuitry is a combination of an antenna and an antenna tuning unit. For example, this information can be used to match antennas with radio receivers and transmitters.

[Problem to be solved by the invention]

An object of the present invention is to provide a method for matching the impedance of an antenna with the impedance of a transmitter or receiver in order to obtain the maximum output of the antenna in wireless communication equipment, and the purpose of the present invention is to provide a method for matching the impedance of an antenna with the impedance of a transmitter or receiver, and to perform antenna matching from only transmitted/received signals or ambient noise. The purpose of the present invention is to provide a method using so-called silent tuning.

That is, in the method described at the beginning, the radio frequency impedance information determined by a radio display means (for example, a receiver) having an appropriate sensitivity (assuming its signal-to-noise ratio is also appropriate) is obtained from the above-mentioned signal source ( It is an object of the present invention to provide a method which makes it possible to respond to radio frequency signals from, for example, an antenna, and which does not require the use of other radio frequency signal sources.

That is, in order to adjust the impedance Zt appearing at the antenna tuning unit T, deviations from a predetermined matching impedance are indicated by an audible sound.

[Means to solve the problem]

The features of the method of the invention are as described in the claims.

That is, in this method, auxiliary networks N1 and N2 are connected between the antenna tuning unit T and the radio display means Rx, and N1 and N2 are rapidly switched alternately. Impedance Z1 of N1 and N2,
It is assumed that Z2 and gain (or attenuation) A1, A2 can be appropriately selected so as to be mismatched with Zt (provided that Z1≠Z2, A1≠A2). This N1,
The rapid switching of N2 results in an audio frequency modulation of the signal reaching the radio display means Rx, which when demodulated results in an audible tone. So that this will be silent
This is to adjust Z1, Z2 and A1, A2.

The impedance values and gain values of the two auxiliary networks described can be predetermined or selected at the time of use. That is, two auxiliary circuit networks are connected alternately as signal paths between the circuit network T and the display means Rx, and in both states, the series and parallel reactances constituting the impedance Zt of the network T are connected to the display means Rx. Adjustments are made so that there is no difference in the amplitude or phase of the applied signals. In other words, those numbers are
It is also possible to select a range in which the trajectory in the description passes through a certain desired point in the complex impedance plane,
Or, as an alternative, the boundary of a certain region of the complex impedance plane representing the conditions desired for the radio frequency impedance to satisfy may be selected within a range such that the trajectory described at least approximates the boundary. For example, the conditions are:
The condition is that the impedance or a parameter dependent on it is not smaller or larger than a certain value.

Preferably, the radio display means comprises a radio receiver, whereby a particularly good sensitivity is achieved and a selection function of the receiver allows unwanted signals (including noise) to be excluded; Furthermore, it becomes possible to easily obtain information on the radio frequency impedance in the approximate vicinity of the frequency of interest.

The radio display means may, for example, include means for determining an amplitude demodulated signal from the signal applied to it, thereby making it possible to display the difference between two values of each of the two parameters. Switching the circuit arrangement described above from one state to another can be carried out at a certain frequency within the audio band, so that the amplitude demodulated signal fed to the audio regenerator can give an audible indication. .

When the present invention is applied to an impedance matching process between an antenna and a radio receiver or a radio transceiver, the receiver is connected to the antenna for radio reception during the matching process, so the radio waves to be transmitted are This has the advantage of being able to continue to receive it (even if it is attenuated by the passive auxiliary network and probably at a lower level than normal).
This is because the radio waves that are sent out are the signals that are generated by the antenna, which are used to obtain information on radio frequency impedance. Similar considerations apply to the use of the present invention in matching carrier telephone receivers to cables with adjustable equalizers.

The present invention will be explained in detail below with reference to the drawings.

〔Example〕

In FIG. 1, an electrical network containing a source of a radio frequency signal, for example an antenna tuning network arranged in series with an antenna, is represented by a two-port network T with a radio frequency voltage source E, Assume that a voltage source E is connected to both ends of one port, and an impedance Zt appears at the other port P. The impedance Zt is the impedance from which information is desired. Also, one port of the two-port auxiliary network N1 is connected to port P of the network T, and both ends of the other port are connected to the radio receiver Rx.
The network N1 is therefore arranged in cascade between the port P of the network T and the receiver Rx.
It is assumed that an impedance Z1 appears at the port P due to the combination of N1 and Rx, and a gain A1 exists between the port P and the receiver Rx. For passive auxiliary networks, A1 is typically less than 1. The voltage Es across the receiver Rx is given by the following formula: Es=EA1Z1/(Zt+Z1) ().

The radio receiver Rx may be integrated with a radio transmitter (not shown).

FIG. 2 shows a circuit arrangement including a pair of auxiliary networks N1, N2 and a receiver Rx. By means of two electronic or electromechanical switches B and D, the circuit arrangement can be coupled to a port P of the network T in two different states. The two different states are such that the auxiliary network N1 or N2 is arranged in cascade between the port P and the receiver Rx, respectively, so that in each case a different impedance Z1 or Z2 appears at the port P, and the port P
and the receiver Rx have different gains A1 or A2, respectively. The circuit arrangement also includes a pulse generator L that provides a square wave switching waveform to switches B and D, whereby the receiver Rx is alternately routed through one auxiliary network or the other. and connects to port P.

The network T is preferably an antenna tuning unit with a reactor network connected in series and in parallel, for example consisting of two parallel variable capacitors with a series variable coil. The network has an impedance Zt, the value of which it is desired to obtain information. An antenna tuning unit is connected between an antenna and its associated transmitter/receiver. The values of the series and parallel reactors are adjusted, for example manually or electrically or electronically, to match the impedance of the antenna to the output impedance of the transmitter. It is convenient to analyze the impedance transformation process by plotting it on a complex impedance plane.

The two auxiliary circuit networks N1 and N2 provided between the receiver Rx and the antenna tuning unit T are switched alternately by switches B and D.
It is connected to the signal path between Rx and the antenna tuning unit T. The auxiliary circuit networks N1 and N2 have impedances Z1 and Z2 and gains A1 and A2, respectively,
The selection of these values Z1, Z2, A1, A2 is determined to provide a wide selection of trajectories. The auxiliary networks N1, N2 are switched and connected to the circuit by a square wave generator L operating in the audio frequency range.

In operation, the series and parallel reactances that make up the impedance Zt of the antenna tuning unit T are connected to the receiver Rx in both of these two connection states.
The idea is to adjust the amplitude and phase of the signals applied until there is no difference.

Assuming that the voltage of the radio frequency signal source is the same in the two states of the circuit arrangement, i.e. assuming that a radio signal with a stable carrier amplitude is incident on the antenna, from equation (), |(A1Z1)/ (Zt+Z1) | = (A2Z2)/(Zt+Z2) |
...(), the signals supplied to the receiver Rx via the networks N1 and N2, respectively, will have equal amplitudes. This can be written as |Zt+Z1|=|A|×|Zt+Z2| () by putting A=(A1Z1)/(A2Z2) ().

The value of Zt that satisfies equation () is on a certain locus in the complex impedance plane. (This plane is
For example, it is a complex plane defined by orthogonal axes representing pure real impedance and pure imaginary impedance. ) This trajectory forms a circle, the center of which is
It is on a straight line passing through Z1 and Z2, and the following formula is used: Za=(|A|Z2−Z1)/(1−|A|)
...() Zb=(-|A|Z2-Z1)/(1+|A|)
...It intersects this straight line at points Za and Zb given by (). Also, the center of this circle is Zc=(|A| ² Z2−Z1)/(1−|A| ² )
... is given by ().

The values of Z1, Z2 and A1, A2 can be selected such that the locus defined by equation () at least approximates the boundary line of the region in the complex impedance plane that represents the condition to be satisfied for impedance Zt. I can do it. And that condition is Zt or the real part of Zt, that is, the conductance corresponding to Zt or
This means that the voltage standing wave ratio (VSWR) brought about by Zt is not smaller or larger than a certain value.

By means of amplitude modulation, the signal applied to the impedance Zt, ie the fundamental modulation frequency at that time, is recovered at the receiver. Since Zt is adjusted to match the impedance to which it is connected, this fundamental modulation frequency will approach zero, ie the amplitude of the audible sound will be zero. This state is
It is indicated by a vector representing the impedance under test Zt that approaches a circular null locus in the impedance complex plane. This trajectory generally takes the form of Figure 4a. In this figure, the coordinate axes represent resistance R and impedance X. If the carrier energy applied to the voltage converter in the impedances N1 and N2 of Figure 2 is not modulated, the 0 locus is still circular, with one intersection Zb with the R axis as shown in Figure 4b. comes to the origin. If the modulation is equal in amplitude and opposite in phase, the 0 locus is a circle centered on the origin, and one intersection point Zb with the R axis is -Za, as shown in Figure 4c.
is equal to If either impedance changes, the center and radius of the circle will change, but one intersection point Za with the R axis can be set to a certain point Z0. (The conditions will be discussed later.) Referring to FIG. Means N1, N2 are shown, and this rapid switching of mismatches
Causes audio frequency modulation of all signals reaching the receiver. The nature of this modulation is a function of the mismatch introduced by the antenna unit, and the receiver output is an audible signal indicative of the impedance match, which is silent if matching is achieved, and silent if there is mismatch. There is an audible sound.

If Zt is adjustable, which is the case in this embodiment, it may be desirable to adjust it to bring it within a region in the complex impedance plane.

Also, as an alternative to or in addition to the above, the values of Z1, Z2 and A1, A2 can be selected such that point Za lies at a certain point Z0, and the corresponding condition is ( ) From the formula, |A|=(Z0+Z1)/(Z0+Z2) ().

Furthermore, from equations () and (), when arg (Zt + Z1) = arg (Zt + Z2) + argA (), in contrast to the reference phase signal at the signal source, the signal at the receiver via circuit networks N1 and N2.
There will be no difference in the phase of the signals fed to Rx. This equation defines another locus for Zt in the complex impedance plane. If Z1, Z2 and A are all positive real numbers, this locus becomes the real axis of the complex impedance plane, and of course Z1, Z2
pass through. Therefore, if Z1, Z2 and A1, A2 are selected to satisfy this condition and equation (), the locus defined by equation () and equation () will be at point Z0 on the real axis. intersect. Therefore, if we adjust the impedance Zt until the receiver indicates that there is no difference in either the amplitude or the phase of the signal supplied to the receiver Rx in the two states of the above circuit arrangement, then Zt can be made equal to Z0.

Using a pulse generator L as shown in FIG.
Using the radio receiver to switch the circuit arrangement between two states and to indicate whether or not amplitude modulation is present at the fundamental switching frequency in the signal supplied to the receiver, respectively. (preferably by amplitude demodulating the signal), whether there is a difference in the amplitude of the signal or not can be determined by
Can be easily displayed. If circuits N1 and N2 are set to switch alternately at some frequency within the audio band (e.g. 300Hz-3kHz) emitted by pulse generator L, the amplitude demodulated signal (with no necessary amplification) The presence of amplitude modulation can be indicated by an audible signal that reproduces the fundamental switching frequency.

The direction of change in amplitude modulation is determined by which side of the locus defined by equation () the impedance Zt is on. The impedances on opposite sides of the trajectory (i.e. inside and outside the circle in Figure 4c) change synchronously with switching the circuit arrangement, i.e. when the circuit arrangement is in one state and in the other state. , can be identified by detecting the amplitude demodulated signal.

Whether there is a difference in the phase of the signal provided to the receiver in two states of the circuit arrangement, compared to the reference phase at the signal source, can be indicated by indicating whether phase modulation is present. This can also be achieved by amplitude demodulating the signal at the receiver, since the phase difference itself does not result in any difference in amplitude between the two states, but it The instantaneous change in phase at each instant of switching to the state results in a change in amplitude at twice the switching frequency, so if the switching frequency is less than a quarter of the frequency bandwidth of the receiver. This is because the receiver can detect it. In this way, a radio receiver designed to only respond to amplitude modulation can also be used to indicate the presence of phase modulation.

As in the case of amplitude modulation, the direction of change in phase modulation is also determined by determining which side (i.e., inside or outside of the circle in Figure 4 c) of the locus to which the impedance Zt is related, that is, the locus defined by equation (). It depends on that. Impedances on opposite sides of the trajectory (i.e., inside and outside the circle in Figure 4c) are demodulated synchronously with the switching of the circuit arrangement using receivers designed to respond to frequency modulation or phase modulation. The identification can be made by detecting the detected signal.

If the electrical network represented by voltage source E and network T in the figure is an antenna and an antenna tuning unit, the present invention is used to match the antenna to a desired impedance at a particular frequency. , after performing the matching process, switch port P directly to the wireless receiver using switches F and G shown in Figure 2.
Preferably connected directly to the Rx (or a radio transmitter associated with it). If the antenna is used with a radio transmitter, Z0 will normally be the output impedance of the transmitter, but the impedance is (although not necessarily) the input impedance of the receiver. Good too.

The ports of the circuit network for which radio frequency impedance information is determined according to the present invention are not necessarily the ports that constitute the output ports of the network under normal use (as described above). Alternatively, it may be a port specifically provided within the circuit configuration for the purpose of obtaining radio frequency impedance information. For example, another port may be provided between two side-by-side reactances of the antenna tuning unit, so that the effect of changing the reactance between the other port and the antenna can be more easily seen. .

In the embodiment shown in FIG. 3, the circuit arrangement has a four-port hybrid transformer HT, and by simply terminating one port of the hybrid section with two different impedances, A radio receiver Rx can be coupled to port P of network T in one of two states. Port 1 of the hybrid part can be coupled to port P via switch F, port 2 can be coupled to the receiver via switch G, port 3 can be terminated with some suitable impedance, and port 4 are each terminated with two different impedances in two different states. In this case, the hybrid converter is of a symmetrical 3 dB type with a characteristic impedance Z0, and some suitable impedance terminating at port 3 means that the matched load (for both states of the circuit arrangement) M and the two impedances at port 4 are pulse generator L
The open and short conditions are determined by switch J controlled by a square wave switching waveform from . Then, when the impedance Zt appearing at port 1 also constitutes a matched load (i.e. has an impedance Z0), ports 2 and 4 are isolated from each other and the state of the termination at port 4 changes from one to the other. It will be seen that the changes have no effect on the signal provided to the receiver. More generally, there will be predetermined conditions that the impedances terminating to ports 1 and 3 must satisfy in order for ports 2 and 4 to be isolated from each other.

From the above explanation regarding the circuit layout in Figure 3, it can be seen that Zt
is centered on the origin as shown in Figure 4c, and Za=
It exists on a circle passing through the point Z0, that is, on the 0 trajectory, and the two states correspond to equations () and (), so for these two states, Z1 = Z0/3, Z2 = 3Z0, And A=j. When there is no difference in the amplitude of the signal supplied to the receiver in the two states, the locus of Zt in the complex impedance plane is a circle centered on the origin and passing through the point Za = Z0, as shown in Figure 4c. becomes.

If at least one of the impedances terminating at port 4 were to change from the values stated above, the radius and center position of the above circle would change, but the circle would still pass through point Z0.

The above given suitable impedance terminating to port 3 may be a single impedance different from the matched load, in which case if Zt is the complex conjugate of the single impedance, then There will be no difference in the amplitude and phase of the supplied signals. Another alternative is port 3
The impedance terminating at port 4 may assume different values in the two states; for this purpose, another switch is provided at port 3, and the pulse generator L switches the switch J at port 4.
It may also be controlled in synchronization with.

A hybrid converter suitable for the circuit arrangement of FIG. 3 is the THV50 broadband device (2-200 MHz) manufactured by ANZAC, USA and having a characteristic impedance of 50 ohms. This device includes a matched load terminating to one port.

Hybrid converters do not necessarily have to be of the symmetrical 3dB type. For example, a device that provides unequal power division can produce a weaker but more strongly modulated signal than with a 3 dB type device when at least one of the parameters has unequal values in the two states. can give.

As described above as an embodiment of the present invention,
Although the radio display means has been described as a radio receiver, it is possible to display the difference in the amplitude or phase of the signal supplied thereto in two states (relative to the reference amplitude and reference phase signals at the signal source, respectively). and also for specific display processes, such as the modulation resulting from switching between two states (as mentioned above) or the direct comparison of numerical values. Anything can be used as a display means.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an equivalent circuit of a circuit configuration used in an embodiment of the invention, FIG. 2 is a diagram showing a first embodiment of the invention, and FIG. 3 is a diagram showing an equivalent circuit of a circuit configuration used in an embodiment of the invention. FIG. 4 is a diagram showing a locus in a complex impedance plane. B, D, F, G, J...changeover switch, E
... Radio frequency voltage source (signal source), HT ... 4-port hybrid converter, L ... Pulse generator,
M...matched load, N1, N2...2-port auxiliary network, P...second port of network T,
Rx...Radio receiver (wireless display means), T...2 port circuit network.

Claims (1)

[Scope of Claims] 1. Information on the value of radio frequency impedance Zt appearing at port P of the electrical circuit network T, E is transmitted to at least one point in the complex impedance plane.
A method for determining in relation to two desired trajectories, which method makes use of a reference signal supplied by a source E of radio frequency signals contained in said network T, E, and Its radio frequency impedance
using a circuit arrangement comprising circuitry means N1, N2 auxiliary to said circuitry T, E of which it is desired to determine information about the value of Zt, and display means Rx responsive to said radio frequency signal; The method includes sequentially connecting the circuit arrangement to the port P in two different states, and
Indicates whether there is a difference between the respective values in two states of the two parameters, amplitude and phase, of the signal supplied to the display means Rx when the reference signal is supplied by the signal source E. using display means Rx, the characteristics of said auxiliary network means N1, N2 being chosen to define said at least one desired locus in a complex impedance plane, said locus comprising two 2 for each one of the parameters
It expresses the condition that the difference between the values in two states is 0, whereby the radio frequency impedance Zt is substantially on one of the loci or not, the impedance provided to the port P by the circuit arrangement having different values Z1, Z2 in each of the two states; and mutually different values A1, A2 in each of the two states of the gain set between the port P and the display means Rx by the auxiliary network means N1, N2.
This means that there is no difference between the respective values in the two states of amplitude according to the following equation |(A1Z1)/(Zt+Z1)|=|(A2Z2)/(Zt+
Z2) (A2Z2), one desired locus in the complex impedance plane, as shown by the radio frequency impedance value Zt satisfying the following equation arg (Zt + Z1) = arg (Zt + Z2) + argA. or to define one of two desired trajectories. 2. In the method according to claim 1, the radio frequency impedance Zt of the circuit networks T and E
are adjustable, and the numbers Z1, Z2, A1, A2 define the boundaries of a certain region of the complex impedance plane representing the conditions that the radio frequency impedance Zt is desired to satisfy, such that one of the trajectories at least and the display means Rx is operable to detect an impedance in a region (complex) of a complex impedance plane separated by the locus, and the method further includes: , a method for determining radio frequency impedance, comprising: adjusting the radio frequency impedance Zt so as to bring the radio frequency impedance Zt within the specific region. 3. In the method according to claim 1, the radio frequency impedance Zt of the circuit networks T and E
is adjustable, and the numbers Z1, Z2, A1, and A2 are the locus 2 of the point where the difference between the values taken by each of the two parameters is 0.
are chosen to intersect at a point in the complex impedance plane representing some desired value of said radio frequency impedance Zt, and the method further includes reducing all said differences to approximately zero for each parameter. and thereby adjusting the radio frequency impedance Zt so as to make it approximately equal to a desired value. 4. A method according to any one of claims 1 to 3, comprising alternatingly switching the circuit arrangement from one state to another, and further comprising: The means Rx is adapted to indicate any of said differences in the signal supplied to said display means Rx by indicating the presence of at least one of two modulations: amplitude modulation and phase modulation. A method for determining radio frequency impedance, characterized in that it is used. 5. A method according to claim 4, comprising: determining a demodulated signal in the display means Rx from the signal applied thereto; detecting the demodulated signal synchronously with being switched to the state, thereby detecting an impedance in a region of a complex impedance plane separated by respective trajectories. How to determine radio frequency impedance. 6. A method according to claim 4 or 5, comprising: determining a signal at an intermediate frequency in the display means Rx from the signal supplied thereto; and determining an amplitude demodulated signal from the signal. and further performing the switching at a frequency not exceeding approximately one quarter of the intermediate frequency bandwidth of the display means Rx;
A method for determining radio frequency impedance, characterized in that it also comprises: a component of the amplitude demodulated signal at twice the switching frequency indicates the presence of phase modulation.