DE102006007475A1 - Circuit arrangement for automatically adjusting high frequency generator, has current sensor measuring supply direct current of generator, and digital control calculating optimal adjustment of tuning units based on analysis result - Google Patents

Abstract

The arrangement has an impedance adjustment network (5) e.g. pi-low pass filter, with two separate adjustable tuning units (6) arranged between a high frequency generator (1) and a consumer (4) e.g. antenna. A current sensor (3) measures supply direct current of the generator, and a digital control (7) analyzes the measured current value for differently adjusted tuning units. The digital control calculates an optimal adjustment of the tuning units based on analysis results by detection of reflection factors, and adjusts the tuning units based on calculation results.

Description

The The invention relates to a circuit arrangement for automatic adaptation a high-frequency generator to any consumer.

The optimal delivery of the power of a high frequency generator to a Consumer assumes that the output impedance of the generator is ideal adapted to the consumer impedance. This is achieved by that both impedances behave in complex conjugate to each other. In the case of a mismatch, the power delivered is reflected, so that, on the one hand, less energy is available to the consumer, on the other hand, the generator can be damaged by the reflux.

To the Balancing a high frequency generator with a consumer is it is already known to tune the high-frequency resonant circuit to optimum standing wave ratio, either by connecting an external standing wave meter or integration a standing wave measuring bridge between high-frequency generator and consumer. Here are the going back and forth Waves extracted and related to each other. The lower the amplitude of the return Wave in proportion to the traveling wave, the better is the standing wave ratio. alternative can determines the phase angles of voltage and current at the consumer become. The adjustment is then to be carried out such that the phase shift becomes minimal at the ohmic load.

The for this However, necessary metrology technique is quite complex, which et al as a result, two measured quantities are always recorded and in relation to each other must be set. About that In addition, the method is prone to error, as in the wrong choice of Line lengths between Generator and consumer the possibility exists an optimal standing wave ratio although the consumer does not achieve the optimum setting has been.

It is still out EP 404 150 known to tune a coupled via a transformer to a transmitter output stage resonant circuit by a lying in the resonant circuit tuning element is adjusted by measurements of the DC supply current of a transmitter output stage so that the DC supply current reaches a maximum value.

This However, the procedure assumes that the output impedance of the generator is precisely known, subject to minor variances and different from Magnitude and phase complex complex to the consumer impedance behave which is often not the case in practice and only by the use of extremely expensive Components approximately can be achieved. In addition, it is often not possible, the amounts the output impedance of the generator with the load impedance in accordance bring to. Another disadvantage of this method is to see that it is only for a special type of consumer is suitable, in this case a series resonant circuit. In a parallel resonant circuit, this is the measurement of the maximum On the other hand, current-oriented methods are not applicable because the current flow minimal here with optimal tuning.

Of the The invention is based on the object, a high-frequency generator with any consumer while avoiding the disadvantages listed to vote, in particular without the use of expensive measuring technology and more expensive Components. About that In addition, the consumer should be spatially separated by a connecting cable can be placed by the high frequency generator.

The The object is achieved by an impedance matching network with at least two separately adjustable Tuning elements, which between high-frequency generator and consumer is arranged, a current sensor, the DC supply current of the high-frequency generator and a digital controller, the current readings with differently adjusted tuning elements analyzed, based on the analysis result under determination of the reflection factor the optimum setting of the tuning elements is calculated, the tuning elements according to the calculation result, then the current flow further monitored and if significantly changed the tuning process is repeated.

Of the achieved with the invention advantage is that with simple metrological means achieved a reliable voting result becomes. For the Voting is only necessary to determine a single measure, which is carried out only with the aid of a current sensor. The otherwise necessary complex Measurement technology is avoided altogether. The circuit arrangement can about that out with common ones Components are realized. Manufacturer-specific tolerances in the Components and in the production of boards can by at least two Degrees of freedom of the impedance matching network are balanced. Also aging and environmental influences can be easily compensated become. The transformation of the impedance conditions is without restrictions possible. By determining the reflection factor is the circuit arrangement according to the invention after all universal for all Types of consumer resonant circuits can be used. A conceivable consumer is for example also a 50 Ohm coaxial cable.

advantageous Embodiments of the invention are given in claims 2 to 4.

In In a preferred embodiment, a plurality of binary weighted Capacitors per tuning element used, giving a maximum variance with minimal effort of space and costs allowed.

In Another preferred embodiment is the impedance matching network a Pi low-pass filter that can achieve high quality. simultaneously can be a pi low-pass filter Especially easy to run with few components, specifically the realization of the (switchable) capacities due to the mass related tuning capacitances easy falls. In addition, the low-pass filter characteristic can be exploited to avoid unwanted harmonics To keep away from the consumer, which due to the high quality especially good.

It may be desired be that a (further) consumer, e.g. an antenna, remote from the high-frequency generator is placed. This can be so according to the invention be realized that the antenna via a cable to the impedance matching network is connected. The cable is then according to the invention as the consumer Radio frequency generator adjusted while the additional consumer, the antenna, again separately by another tuning process adapted to the cable. However, this second tuning process can avoided by a further preferred embodiment of the invention in which the cable is formed within a Pi low-pass filter Impedance matching network is integrated. Will the digital controller pass the cable length and from this into the calculation of the optimum setting of the tuning elements included Cable and (further) consumers in a single tuning process summarized become. The cable integrated into the Pi low-pass filter can be used be any length.

The Invention will be described below with reference to an embodiment with reference closer to a drawing explained. The single figure shows the circuit arrangement according to the invention as Block diagram, with the consumer directly to impedance matching network and RF generator and the impedance matching network is formed with two tuning elements.

The high-frequency generator ( 1 ) is replaced by a source ( 2 ) supplied with direct current. The direct current is supplied by a current sensor ( 3 ). Between high-frequency generator ( 1 ) and consumers ( 4 ) is an impedance matching network ( 5 ), which has at least two tuning elements ( 6 ). The tuning elements ( 6 ) are controlled by a digital controller ( 7 ). After each new adjustment of the tuning elements ( 6 ) of the impedance matching network ( 5 ) calls the digital controller ( 7 ) by a current sensor ( 3 ) measured value of the DC supply current of the high-frequency generator ( 1 ). This process is repeated until the digital controller ( 7 ) sufficient values to calculate the optimal setting of the tuning elements ( 6 ) be available. The tuning elements ( 6 ) are controlled by the digital controller ( 7 ) is then optimally adjusted according to the result of the calculation, so that the impedance matching network ( 5 ) the load impedance of the consumer ( 4 ) is transformed such that it is conjugate complex to the output impedance of the high-frequency generator ( 1 ) behaves. After the digital control ( 7 ) the tuning elements ( 6 ) of the impedance matching network ( 5 ) optimally monitors the current from the current sensor ( 3 ) and, in the case of a significant change, starts again with the setting of the tuning elements ( 6 ).

1

High-frequency generator

2

power source

3

current sensor

4

consumer

5

impedance matching

6

tuning

7

digital control

Claims (4)

Circuit arrangement for automatic adaptation a high-frequency generator to any consumer, marked by - one Impedance matching network with at least two separately adjustable Tuning elements, which are arranged between high-frequency generator and consumer is - one Current sensor, the DC supply current of the high-frequency generator measures, - one digital controller that sets the current readings at different Voting elements analyzed based on the analysis result below Determination of the reflection factor the optimal adjustment of the tuning elements calculated, the tuning elements according to the calculation result then continue to monitor the current flow and if there is a significant change the tuning process is repeated. Circuit arrangement according to claim 1, characterized in that - the tuning elements of the impedance matching network are variable capacitances, which are each through a plurality of binary weighted and switchable capacitors are formed. Circuit arrangement according to Claim 1 or 2, thereby marked that - the Impedanzanpassnetzwerk is formed as a Pi low-pass filter. Circuit arrangement according to Claim 3, thereby marked that - within the Pi low-pass filter, a cable of any length is integrated, - the digital Control the length of the cable in the calculation of the optimal setting of the tuning elements involves.