JPH033407A - Amplifier, which can be utilized in ultra-high frequency region and gain of which can be adjusted - Google Patents

Abstract

PURPOSE: To provide a gain adjustable MMIC(Monolithic Microwave Integrated Circuit) monolithic amplifier by applying a control voltage to one of the terminals of an MMIC monolithic circuit. CONSTITUTION: At least one MMIC 5 provided with the two terminals 2 and 4 for grounding is utilized, one 4 of the terminals is grounded by self induction 13 and the other 2 is grounded by a capacitance 14 cascade connected with an impedance 16 adjustable from the outside. Then, by applying a voltage V to the adjustable impedance, for instance a PIN diode, and changing it, not only an operation is performed at a high frequency but also the automatic control of this amplifier is made possible. Thus, an ultra high frequency monolithic amplifier gain adjustable by external control is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention applies in the very high frequency range, at intermediate frequencies (70 to 140 MHz for the sake of clarity), as well as at radio frequencies (e.g. around 1 GHz) or low frequencies (e.g. 10 MHz). The present invention relates to an adjustable gain amplifier that can be used in.

In the receiving network, the demodulators required to reproduce the information must be started at a constant level in order to function correctly.

Conversely, the receive level can vary by several decibels as a function of flow rate, receive section configuration (cross type, cable type, etc.) or propagation loss. Adjustable gain amplifiers are therefore required to have automatic or manual control of gain.

Adjustable gain is traditionally implemented using an adjustable attenuator inserted into the amplifier network preceding the demodulator. This type of attenuator must maintain linearity in its amplitude/frequency characteristics as a function of attenuation and must not produce intermodulation interference lines for high input levels.

Conventionally used amplification channels typically include a constant gain amplifier followed by this variable attenuator.

This has been found necessary to hide the relatively significant noise factor of the attenuator and to avoid too low levels at low received fields.

Problems arise with these classical devices when the input level dynamics are large. This is because the same channel must be able to operate with both low and high input levels without generating intermodulation interference lines.

The main types of variable attenuators commonly used at intermediate frequencies (70 to 140 MHz) are:

Connection to φ ring type modulator double lattice field effect transistor/Connection to PIN diode.

For the first two types above, the saturation point is at the lowest point for maximum attenuation (whereas the received level is highest), which is not ideal.

Conversely, PIN diode attenuators are less sensitive at received levels, but their amplitude/frequency characteristics as a function of attenuation are less linear. Moreover, they are quite cumbersome to realize if one wishes to obtain large dynamic characteristics.

In short, regardless of the type of attenuator used, a constant gain amplifier placed at the input risks saturating for high input levels and having too low a gain for low received levels.

The present invention aims to rectify these drawbacks by proposing an amplifier with a gain adjustable by external control, which does not use an adjustable attenuator and only has one or several MM IC (Monol)
ithic IJicrov*wc InjeHrxt
edCircaN or ultra-high frequency monolithic integrated circuit)
Integration is easily possible by using an amplifier. At issue is the type of adjustable-gain amplifier that utilizes the well-known principle of voltage-current inverse reaction (subtracting from the input voltage a voltage equal to the output current). The present amplifier consists of at least one amplification stage including at least one MMIC amplifier, the terminal of which is proposed by the designer for connection to earth, on the one hand, which is connected to the MMIC amplifier in opposition to the passage of the alternating current signal to be amplified. It is grounded by means of at least one shock self-induction which closes the bias circuit of the module, and on the other hand by means of an externally adjustable value impedance followed by a separating capacitor.

In some cases, this adjustable impedance is a purely manually adjustable impedance (such as a rheostat).
or a PIN diode whose impedance is adjusted by its bias voltage, thus allowing automatic gain control of this gain-adjustable amplifier.

In any case, the invention will be better understood, and its advantages and other features will become apparent, from the following description of some non-limiting embodiments of the invention with reference to the accompanying drawings. .

Referring to FIG. 1, an MMIC amplifier is an integrated circuit or
It is represented in the form of a chip 5 and includes four access terminals:

- The two terminals on the chip, generally designated 2 and 4, must be grounded as shown.

- In general, the input terminal indicated by 1 is connected via a coupling capacitor 6 to an AC signal (radio frequency, etc.) receiving terminal 7 for amplification.

- The output terminal, generally indicated at 3, can be connected to an AC output terminal 9 via a coupling capacitor 8, and further applied at 12 via a bias resistor 11 and an impulse self-induction 10 (optional depending on the frequency). DC bias +Vc
Receive.

Referring now to FIG. 2, this same MMIC amplifier 5 is used to create an adjustable inverse response of the voltage-current type (
Subtracting the voltage proportional to the output current from the input voltage () is used in a variety of ways.

In fact, if the input circuit (upstream of terminal l) and the output (or bias) circuit on terminal 3 remain unchanged, then on the contrary terminals 2 and 4 are not directly grounded as specified by the designer. Terminal 4 is coupled to ground across a shock self-induction 13, which self-induction forms a quasi-infinite impedance for the alternating current voltage to be amplified, while allowing the connection of the DC bias circuit of chip 5, and on the other hand the terminal 2 is
A variable resistor 15, constituted for example by a potentiometer mounted as a rheostat, is connected to ground through a subsequent DC current stopping capacitor 14.

By manually adjusting the value of resistor 15, the reverse reactivity on amplifier 5 is adjusted, thus modifying its gain, while retaining the advantages of voltage-current reverse reaction to achieve wide range non-saturation operation. be able to.

In FIG. 2, variable resistor 15 is shown for general understanding of the method of the invention. It is clear that this type of resistor is practically only considered for low frequencies (eg around 10 MHz).

For even higher frequencies, this variable resistor 15 can be
It is advantageous to replace it with a PIN diode, such as the one indicated by reference numeral 16 in the figure. The resistance of this PIN diode 16 is made variable by varying the voltage V applied to terminal 40 and is further biased via resistor 17. This method not only operates at higher frequencies (intermediate frequencies, and even radio frequencies if minimal care is taken), but the amplifier This shows the advantage that it also enables automatic control of the gain.

An embodiment of this adjustable amplifier is shown in FIG.

At issue here is a two-stage amplifier, which allows quite significant dynamics (around about 30 dB).

Furthermore, since these two-stage amplifiers are supplied with DC power, power consumption can be reduced.

The amplifier in FIG. 4 has two MMIs designated 18 and 19.
C amplifier, input and output terminals 7 and 9 respectively
are connected in cascade between them. The output terminal 3 of the second MMIC 19 is coupled to the output terminal 9 via the coupling capacitor 8 as described above, and further via the impulse self-induction 10 (decoupled to ground by the capacitor 20) and the supply terminal via the bias resistor 11. (receives DC voltage element Vc).

Terminal 4 of this amplifier 19 is connected to shock self-induction 21 and 33 (
which is also decoupled to ground by a capacitor 22) to the output terminal 3 of the first MMIC 18;
On the other hand, the terminal 4 of the first MMIC is grounded by the shock self-induction 23, thereby loop-connecting the series bias circuit of the two MMICs 19 and 18.

From another point of view, the output 3 of MMIC1B is connected to the input 1 of MMIC19 via the coupling capacitor 24.

As in the case of the amplifier of FIG.
It is coupled to ground via IN diodes 27 and 28. The control voltage V of these PIN diodes is applied to the terminal 4G via the series impulse self-induction 2g and a common decoupling circuit to the parallel capacitance 30 and the respective bias resistors 31 and 32.

As mentioned earlier, the control voltage V is connected to the PIN diodes 27 and 2.
8 and thus the total gain of this two-stage amplifier. This connection method is realized by two 13 dB MMIC amplifiers and guarantees a dynamic characteristic of approximately 30 dll (+1 adn to -12 dB) of first order as an amplitude/frequency response as a function of the gain, and also for a minimum gain without saturation phenomena. Allows input levels of +SdBm.

The device of the invention can be used in microwave trunk lines or ground stations in intermediate frequency reception channels between 70 and 140 MHz. It can also be used in radio frequency channels of, for example, 1 gigahertz, provided that the ultra-high frequency implementation rules are also observed. In this case, integration of the PIN diode into the MMIC monolithic circuit is highly recommended. In this way, an MMIC monolithic amplifier of one stage or several stages whose gain can be adjusted by applying a control voltage V to one of the terminals is obtained.

Of course, the invention is not limited to the embodiments described above, but can be realized in other equipartition formats, for example by combining terminals 2 and 4 of each used MMIC amplifier into one.

The invention finds its most advantageous application in the implementation of gain automatic or manual amplifiers. Although FIG. 4 shows an embodiment of a two-stage amplifier, it would of course be possible to include two or more stages of amplifiers, preferably fed in series as in the case of the amplifier of FIG.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram of a conventional MMIC amplifier, Fig. 2 is a connection diagram of the adjustable amplifier of the present invention, which is a single-stage amplifier with manual adjustment, and Fig. 3 is a connection diagram of the tunable amplifier of the present invention, which is a single-stage amplifier with manual adjustment. A connection diagram of a modified example of the amplifier and FIG. 4 are an implementation diagram of a two-stage adjustable amplifier. 2.4... terminal, 5... monolithic microwave integrated circuit amplifier module, 13...
...Impact self-inductance, 15. lIi...
...Variable impedance, ■...External bias voltage. Integrated monolith 41 with dynamically controlled terminals 40
−

Claims (5)

[Claims] (1) An adjustable gain amplifier usable in the very high frequency range, consisting of at least one stage of amplifier, including at least one MMIC amplifier, the terminal of which is normally proposed by the designer to be connected to earth. is grounded on the one hand by at least one shock self-induction which closes the bias circuit of the MMIC module against the passage of the alternating current signal to be amplified, and on the other hand by an externally adjustable value impedance followed by a separating capacitor. An amplifier characterized by being grounded. (2) at least one MMI containing two separate terminals proposed by the designer to ground each;
2. A device according to claim 1, characterized in that one of these terminals is grounded by the shock self-induction and the other is grounded by the isolation capacitance followed by the adjustable impedance. Gain adjustable amplifier. 3. The adjustable gain amplifier of claim 1, wherein the adjustable impedance is a PIN diode, the impedance of which is made adjustable by application of an external bias voltage. (4) Claim 3 characterized in that it is realized by being integrated on a monolithic circuit of one or several MMIC modules together with a gain control terminal using an external voltage.
Adjustable gain amplifier as described in . (5) including at least two stages of cascaded amplifiers, each amplifier including an MMIC module coupled as described above to an adjustable impedance, and all of these modules having an output of the first stage; Claim 1 characterized in that the second stage MMIC module is powered in series, including the self-induction and grounding circuits of the second stage MMIC module coupled to the terminal, and the subsequent stages, if any, continue in the same order. 5. The gain adjustable amplifier according to claim 4.