US3710268A

US3710268A - Parametric amplifier

Info

Publication number: US3710268A
Application number: US00013437A
Authority: US
Inventors: D Neuf
Original assignee: RHG ELECTRONICS LABOR Inc
Current assignee: ADAMS-RUSSELL ELECTRONICS Co Inc 1380 MAIN ST WALTHAM MA 02154 ("A-R") A CORP OF; RHG ELECTRONICS LABOR Inc
Priority date: 1970-02-24
Filing date: 1970-02-24
Publication date: 1973-01-09
Anticipated expiration: 1990-01-09

Abstract

A parametric amplifier having four substantially identical variable reactance diodes arranged in a bridge circuit supplied with a pump voltage and a signal voltage and developing an idler voltage when these voltage sources are each connected to the diagonally opposed terminals of the bridge and the idler current is contained within the bridge arms. The bridge arrangement provides inherent isolation of two and in some cases the three voltage frequencies. The aforementioned abstract is neither intended to define the invention of the application which, of course, is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

Description

United States Patent [191 Neuf Y 1 Jan. 9, 1973 [75] Inventor:

[73] Assignee: RHG Electronics Laboratory, Inc.,

[54] PARAMETRIC AMPLIFIER Donald Neuf, Wantagh, N.Y.

Farmingdale, L.l., N.Y.

[22] Filed: Feb. 24, 1970 21 Appl. No: 13,437

[52] U.S. Cl. ..330/4.9, 307/883, 330/7 [51] Int. Cl ..H03t 7/00 [58] Field of Search ..330/4.9, 7; 307/883 [56] References Cited UNITED STATES PATENTS 2,850,585 1 9/1958 .Green ..330/7 3,433,976 3/1969 Mare chal r. ..330/7 3,510,674 5/1970 Biard 3,249,831 5/1966 De Niet..... 3,230,464 1/1966 Grace ..330/4.9 3,526,781" 9/1970 Janning ..330/4.9

Primary Examiner-John Kominski Assistant Examiner-Darwin R. Hostetter Attorney-Leonard l-l. King [57] ABSTRACT A parametric amplifier having four substantially identical variable reactance diodes arranged in a bridge circuit supplied with a pump voltage and a signal voltage and developing an idler voltage when these voltage sources are each connected to the diagonally opposed terminals of the bridge and the idler current is contained within the bridge arms. The bridge arrangement provides inherent isolation of two and in some cases the three voltage frequencies.

The aforementioned abstract is neither intended to define the invention of the application which, of course, is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

6 Claims, 10 Drawing Figures PATENTEDJAN 9l975 3.710.268

sum 1 [IF 6 INPUT ONE-PORT PARAMETEIC PUMP AMPLIFIER OUTPUT F] G 1 INPUT INPUT 7W0 P0127 Z I ARAMETR/C wpur ISOZATION ISOLATION T 15 AMPLIFIER 16 f 17 PUMP /14 FIG. 2

INVENTOR.

DONALD NE ATTORNE PATENIEUJMI 9 ma 3.710.268

SHEET 2 OF 6 INSTANHNEOl/S' 38 L PUMP CURRENT ClFTes e-szawu.

FIG. 3

INVENTOR. DONAL-D lly! ATTORNEY PATENTEUJAH 9 I975 SHEET 3 BF 6 $1 GNAL CURRENT PUMP CURBEIVT INVENTOR.

46 G 'JDL 'ER FIG. 4

ATTORNEY PATENTEDJAH 9 I973 3.710.268

sum u 0F F] G. 6 INVENTOR. DONALD MEI/F ATTORNEY PATENTED JAN 9 I975 SHEET 5 BF 6 FIG. 8

ENVENTOR. DONALD NJ'UF ATTORNEY PATENTEDJAN 9 I973 SHEET 6 [1F 6 FIG. 10

I8 0 P0 WEE DIV/DER INVENTOR. DONALD NEUF ATTORNEY PARAMETRIC AMPLIFIER This invention relates to amplifiers and specifically to the parametric amplifier employing a variable reactance element.

With the advance in microwave communications, there resulted a great need for microwave devices which can amplify one frequency or convert a signal from one frequency to another while providing power amplification. Mixing devices using non-linear elements have generally been used. The mixing devices exchange the energy in a controlled manner from a high power source signal to a lower power signal at a different frequency, thereby achieving gain at the latter frequency.

The variable reactance diode has been especially useful in parametric amplifiers because of its low-noise properties. Because of this very small amount of internal noise generated during the amplifying process, the parametric amplifier has been used as the front end" of sensitive receiving stations.

In operation the parametric amplifier generally uses a variable capacitance diode as the reactance element; The reactance is varied at a pump frequency and an input signal to be amplified is applied. The pump frequency is generally much higher than the input signal frequency. The amplifier develops a difference frequency between the pump and signal frequencies, commonly called the idler frequency. In some modes of operations the pump frequency is approximately twice the signal frequency, whereby the. idler frequency will equal the input frequency. In other modes, the pump frequency is greater than twice the signal frequency, so that the signal frequency and the idler frequencies differ from each other.

When the signal and idler frequencies overlap each other, it is referred to as degenerate mode; otherwise it is called non-degenerate mode.

With the idler frequency being different from the signal frequency, the output can be taken either at the signal frequency or at the idler frequency. When the input and output frequencies are different, the amplifier is commonly referred to as a two-port sum or difference frequency amplifier, depending upon whether the sum or difference of the pump and signal is used as the output frequency. If the amplifier input and output terminal is the same, it is termed, one-port operation. In the one-port operation a circulator is required to separate the input and output signals. The input signal is applied to one side of the circulator and thereafter transferred to a second side of the circulator. Such circulators are well known in the microwave art.

Owing to the negative input impedance of the oneport-non degenerate mode, andthe subsequent power reflection coefficient which can be greater than unity, it is possible to obtain a reflected signal from the oneport-non degenerate mode, which is greater thanthe input signal. This reflected or amplified output is transferred by the circulator to the output side. In this manner the inherent one port of the one-port-non degenerate parametric amplifier is made into a usable system with separate input and output ports.

In addition to the inherent low noise of the parametric amplifier it is also preferred to other types of mixers because it can convert the frequency of an input signal without loss in power; in fact, depending upon the impedance levels at the signal and! idler frequency terminals of the parametric amplifier, almost any desirable amount of gain can be achieved with a corresponding reduction in bandwidth.

It is generally desirous to improve the amplifier by making it tunable over a large bandwidth while maintaining low noise and a large gain-bandwidth product. The most significant problem in dealing with improve ments in parametric amplifiers is providing adequate isolation of the three frequencies (pump, signal and idler). While it is required that the three signals be tightly coupled to the variable reactance diode, it is also necessary that at the same time these signals be decoupled from each other.

In the prior art, the need forisolation has resulted in designs using sophisticated coupling mechanisms, and elaborate filters associated with each signal. In general, these schemes involve a degradation of the gain bandwidth product.

The present invention provides a double-balanced bridge configuration using at least four variable reactance diodes whereby the signals are each applied across independent terminals resulting in complete isolation of each frequency from the other. The pump signal is applied across one set of cross terminals, the

input signal is applied across a second set of cross terminals, and the idler signal is completely contained within the bridge arms, independent of the circuitry external to the bridge.

Accordingly, it is an object of this invention to provide an improvedparametric amplifier having greater isolation between ports.

Another object is to provide a parametric amplifier using four variable reactance diodes connected in a bridge configuration.

Yet another object is to provide a microwave amplifier using a diode bridge arrangement wherein two of the three frequencies are isolated by virtue of the balanced properties of the bridge configuration.

Still another object is to provide a variable reactance diode bridge arrangement.

Another object is to provide a one-port parametric amplifier wherein the pump signal and input signal are applied at cross terminals and. the idler signal is completely contained within the bridge.

A further object is to provide a two-port parametric amplifier having a diode bridge arrangement wherein the pump signal and one other signal is applied at the cross terminals and the idler signal is coupled out of the bridge.

Yet another object is to provide a microwave device for use as a parametric amplifier having a variable reactance diode bridge arrangement.

Still yet another object is to provide a bridge arrange ment of four variable reactance diode chips mounted in a microwave parametric amplifier.

A still further object is to provide a balanced 3 BRIEF DESCRIPTIOn OF THE DRAWING FIG. 1 is a block diagram of a generalized one-port amplifier configuration as is known in the art;

FIG. 2 is a block diagram of a generalized two-port amplifier configuration as is known in the art;

FIG. 3 is a circuit diagram of the parametric amplifier for a one-port configuration in accordance with the teachings of this invention;

FIG. 4 is a circuit diagram of a parametric amplifier for a two-port configuration in accordance-with the teachings of this invention;

FIG. 5 is a top view of an assembled microwave parametric amplifier embodiment of this invention for one-port operation;

FIG. 6 is a bottom plan view of the device of FIG. 5;

FIG. 7 is a perspective view of the variable reactance diode bridge as arranged for a microwave parametric amplifier component;

FIG. 8 is a perspective view of the bridge shown in FIG. 7 as it is assembled within an amplifier component;

FIG. 9 is a plan view of an assembled microwave parametric amplifier embodiment of this invention for two-port operation; and

FIG. 10 is a perspective view illustrating another microwave embodiment of one-port parametric amplifier.

Referring to FIG. 1, an input signal is supplied to port (a) of a circulator l0 and is transferred by the circulator to port (b) for amplification by a one-port parametric amplifier 11. The amplified output signal returns to the circulator through port (b) and is directed to an output port (0) of the circulator. Circulators of this type are well known in the microwave art and will not be described in detail. A pump source 12 provides the pump frequency for the parametric amplifier 11. This figure shows the one-port amplifier configuration as is generally used in the art.

The two-port amplifier configuration which is generally used is shown in FIG. 2. For two-port operation the input signal and the output signal are not restricted to be at the same frequency. The input signal is supplied at 15 to a two-port parametric amplifier 13 and the output signal is derived at 16. The pump source is provided at 14. In order to insure stable operation isolators are placed on the input and output side of the

amplifier

17, 18. The isolators are typically designed to pass only the frequency of the signal on its side.

FIG. 3 shows a one-port parametric amplifier 11 which can be used in the one-port amplifier configuration shown in FIG. 1. Four substantially identical

variable reactance diodes

20, 21, 22, 23 are each connected in respective arms of a bridge. The diodes are connected such that each one is reversed from the ones in its adjacent arms. For example, referring to diode as forward, diode 21 would be reversed, diode 22 forward and diode 23 reversed. Technically, all diodes are reverse biased (at DC) but RF signals are applied in both forward and reversed polarity (see arrows). The signal voltage is supplied at 24 and is applied to the bridge circuit through a signal transformer 25. The input signal is connected to one set of

bridge cross terminals

26, 27. Interconnected in the supply lines between the transformer 25 and the bridge are

inductances

28, 29 which serve as a signal tuning reactance as well as providing some isolation from any pump signal which may develop on these lines.

The pump voltage is provided at 30 across pump transformer 31 to the remaining set of

cross terminals

32, 33. Interconnected between the pump transformer and the bridge terminals are

capacitors

34, 35 which serve as coupling capacitors for the pump voltage as well as providing isolation against the signal voltage and any DC signal.

In prior art amplifiers it has been known to use a pair of identical diodes to form a balanced amplifier. The diodes are generally placed in opposition to each other whereby the noise components will be reduced while the signal will be enhanced. The circuit of FIG. 3 uses a double balanced amplifier design which further provides for signal isolation. For an explanation of the capabilities assume the instantaneous polarity of the signals as shown. Terminal 30a of the pump voltage is positive with respect to terminal 30b. Similarly terminal 24a of the signal voltage is positive with respect to terminal 24b. The diodes of the bridge are substantially identical, to provide the same characteristics and reactances. Accordingly, during balanced operations the voltage drop of the pump voltage through one set of

arms including diodes

20 and 21 will exactly equal the voltage drop through the other set of

arms including diodes

23, 22. Since the four diodes are identical, the

pump voltage at terminal 26 will exactly equal the.

pump voltage at terminal 27 and no pump current will flow through

lines

36 and 37.

The signal voltage applied across

terminals

26 and 27 will be the same through the set of bridge

arms including diodes

21 and 22 and the set of arms including the

diodes

20 and and 23. Also, because of the identical diodes,

terminals

32 and 33 will have the same signal voltage and no signal current will flow in

lines

38, 39. The pump and signal voltages are therefore completely isolated from each other. Should there be any slight unbalance in the diodes, whatever minimal pump current might flow on

lines

36, 37 would be blocked by the

reactances

29, 28 which are tuned to the signal frequency. Similarly, any signal voltage which might cause a signal current to flow on

lines

38, 39 would be blocked by

capacitors

34, 35.

With the voltages of the pump and signal sources as shown in FIG. 3, the signal current would flow from terminal 26 to terminal 27 through both parallel

paths including diodes

23, 20 and 22, 21. The pump current would flow from terminal 32 to terminal 33 through the two parallel paths, the one containing

diode

21, 20; the other containing the

diodes

22, 23.

As a result of the diode arrangement and the polarity of the applied pump and signal voltages, the difference voltage or idler frequency signal is excited within the bridge arms such that idler current will be completely contained within the bridge arms. Furthermore, it will be independent of external circuit loading since at the pump and signal terminals no idler voltage exists.

In the double balanced bridge circuit the three signals will therefore be isolated from each other. The pump and signal voltages will be isolated because of the inherent balance of the two sides of the bridge. The idler current will be isolated because of the resultant cancellations of the idler at the signal and pump terminals.

The reactance characteristic of the variable reactance diode is such as to vary as a function of the reverse voltage across the diode. As the reverse bias voltage is increased the capacitance decreases. Thus considerable adjustment in the capacitance can be obtained by varying the bias on the diodes. RF chokes 48 and 41 are added at

terminals

32 and 33 for introducing the DC bias on the diodes. RF chokes 42 and 43 are added at

terminal

26 and 27 for the DC bias return.

FIG. 4 shows a two-port parametric amplifier 13 which can be used in the two-port amplifier configuration of FIG. 2. The basic concept of the two-port amplifier is similar to that discussed for the one-port amplifier in connection with FIG. 3. The additional requirements are that the output be taken at either the signal voltage or more usually the idler voltage. In FIG. 4

. components which are the same as those of FIG. 3 are similarly numbered.

The bridge consists of four arms each containing

variable reactance diodes

20, 21, 22, 23. The diodes are placed so that each is in the same direction as one adjacent arm and in opposite direction to theother adjacent arm. Following the designation of FIG. 3 wherein diode was there in the forward direction, in FIG. 4 diode 20 is in the reverse direction, diode 21 in the forward direction, diode 22 in the forward direction and diode 23 in the reverse direction.

Pump voltage is applied at 30 across the transformer 31 to

terminals

32 and 33 by means of

lines

38 and 39. Capacitors 34 in

line

38 and 35 in line 39 serve as pump coupling capacitors and also provide a DC block and isolate the signal voltage. The signal voltage is applied at 24 across transformer by means of

lines

36 and 37 to the

same terminals

32,33 as the pump voltage. Inductors 28 in

line

36 and 29 in line 37 provide a signal tuning reactance and serves to isolate the pump voltage from the signal voltage. In addition, capacitor 44 in series with inductor 28 and capacitor 45 in series with inductor 29 acts as DC blocking capacitors permitting only signal voltage to pass.

The idler voltage output is taken at 46 from

bridge terminals

26, 27 through lines 50, 51 and across transformer 47. Capacitors 48 in line 50 and 49 in line 51 serve as DC blocking capacitors and permit idler voltage passing through. The DC bias for the diodes is provided through Rf chokes 52, 53, each connected to one i of the idler lines 50, 51 and RF choke 52 is connected to the positive supply, and RF choke 53 is connected to the DC negative supply.

To understand the operation of the circuit of FIG. 4, the various instantaneous voltages have polarities as shown. Pump voltage supply terminal a is positive with respect to 30b. The voltage from terminals 32 to 33 is across parallel

paths comprising diodes

20, 21 and 23, 22. Because

diodes

20 and 23 are oppositely biased, their reactances differ and a small pump voltage will appear between

terminals

26 and 27.

The signal voltage at 24 has a polarity such that 24 is a positive with respect to 24b. The signal voltage will appear between

terminals

32 and 33. The pump voltage and the signal voltage will combine in each diode to form the difference or idler voltage at

terminals

26, 27. The idler voltage will be the output voltage appearing at 46 with terminals 464 positive and 46b negative.

With the voltage polarities as shown, the currents in the bridge will be as indicated. The pump and signal currents flow concurrently through the bridge from terminals 33 to terminal 32, through both parallel bridge paths, including

diodes

20, 23 and 21, 22. The idler between the idler signal and the other signals. Because of the substantially identical diodes and their orientation there will be no idlervoltage between

terminals

32 and 33. The pump and signal voltages will thus be isolated from the idler voltage. In this configuration, the bridge does not provide any inherent isolation between the pump and signal voltages. However, the pump and signal frequencies are sufficiently separated such that the simple filtering networks of

capacitors

34, 35 and

inductors

28, 29 are sufficient to isolate the signal and pump voltages. The reactance of the

pump coupling capacitors

34, 35 will be considerably higher at the low signal frequency thus providing the necessary pump to signal isolation. The inductive reactance of

inductors

28, 29 would prevent the pump from coupling to the signal port.

If the particular use was such that the signal and pump frequencies were close together and the idler frequency was the lowest and separated from theothers, FIG. 4 would be altered. such that the idler frequency would be taken out at

terminals

32, 33 and the signal voltage would be applied at the

opposite terminals

26, 27. In this case, by interchanging, the idler and signal supply circuits, the inherent bridge configuration would isolate the signal from the pump while the idler voltage being at a separated frequency, would be isolated by filter means.

Although the circuit of FIG. 4 is best used for a twoport amplifier configuration, it can also be used for a one-port configuration where access to the idler circuit is required. The circuit of FIG. 4 allows external coupling to the idler circuit in order'to vary the resistance of the idler circuit. The output from the circuit of FIG. 4 when used as a one-port amplifier would be taken from the signal voltage terminals 24a and 24b.

FIGS. 5 and 6 indicated one microwave embodiment of the one-port parametric amplifier shown in FIG. 3. FIG. 5 represents the top view of the device and FIG. 6 shows the ground side of the device. A housing 55 consists of a frame holding a dielectric substrate sheet 56 securely fastened to the frame on two

sides

57, 58. A space is left 59, 60 between the substrate 56 and the remaining sides of the frame. The space is filled in with lossy RF material to reduce reflections. Situated at either end of the

frame members

57,58 are

coaxial cable connections

61, 62 securely fastened to the housing 55. Situated on the substrate are four variablereactance diodes electrically connected in a bridge arrangement as hereinbefore described in connection with FIG. 3. The diodes are attached with two diodes, 20, 23 connectedon the top side of the substrate and two diodes 22, ZIconnected on the ground side of the substrate.

FIG. 7 shows a schematic of the packaging arrangement of the diode bridge assembly. The four

diodes

20, 21, 22, 23, electrically connected as hereinbefore described are physically placed such that

diodes

20 and 23 are in a single plane with an electrical contact 32 connected therebetween. Similarly

diodes

21 and 22 are in the same plane.

Diodes

20 and 21 are electrically interconnected in common with terminal 26 and

diodes

22 and 23 have terminal 27 electrically interconnected therebetween.

Referring back to FIGS. and 6, coaxial connection 61 is used to provide the signal voltage while connection 62 is for the pump voltage. In between the coaxial connections and the diode package is placed a microstrip transformer. The signal transformer is comprised of the

metallic strips

63a and 63b having the dielectric substrate therebetween. The pump transformer comprises

metallic strips

64a and 64b with the dielectric substrate between them.

The coaxial input to the amplifier is unbalanced while the microstrip lines needed to power the diodes is balanced. A balancing unit or balun is used to accomplish the transition from the unbalanced to the balanced condition. This is accomplished by gradually tapering the conventional ground plane side of the metallic strip material until it becomes equal in width to the metallic strip on the opposite side of the dielectric. The signal balun is comprised of sections 65a on the top side and 65b on the conventional ground side of the dielectric. Metallic strip 65b is tapered from its broad width at the signal input terminal 61, until its narrow width at the transformer connection. The narrow width of strip 65b is made equal to the width of the balun strip 65a. Similarly for the pump balun, the conventional ground side metallic strip 66b is tapered from its broad width at the pump input terminal 62 to a narrow width equal to the top side strip 66a. The narrow end is connected to the transfer 64.

FIG. 8 illustrates a detail view of the diode package of FIGS. 5, 6 and shows the interconnections between the diode bridge and the signal and pump voltages. The interconnecting lead 26 between diodes and 21 (FIG. 7) is brought to the top side of the substrate and is connected to one end of the signal transformer 63a by means of signal tuning inductance 28. On the conventional ground side, the other end of the signal transformer 63b would be connected to terminal 27 by means of signal tuning inductance 29. One end of the pump transformer 64a is connected to tenninal 32 by means of the pump coupling capacitance 34. The other end of the pump transformer 64b would be connected on the ground side to terminal 33 by means of coupling capacitor 35.

In order to introduce DC bias miniature coils wound on finely threaded dielectric screws 67 are used. The DC bias is introduced through an RF bypass capacitor included in

terminals

68a and 68b, then through

coils

67a and 67b to the

terminals

32, 33. The DC bias return is taken out through RF coil 670.

FIG. 9 illustrates a possible microwave equivalent of the two-port parametric amplifier shown in FIG. 4. The basic configuration of the diode package, the balanced microstrip transformers and baluns are similar to that described for FIGS. 5 through 8. For the two-port configuration, however, the diode would be biased as shown in F IG. 4. Also, for the two-port case a separate port must be provided for the idler voltage. In FIG. 9 coaxial connector 61 provides the pump input which is connected by means of the microstrip balun and transformer to terminal 32. The idler output is taken from terminal 26 through the microstrip to coaxial connector 62. The signal voltage is coupled to the diode bridge by means of coaxial connector 69. Instead of microstrip, a coupling coil of fine wire wound on to a dielectric member 70 is used. The coupling coil serves to isolate the pump signal as well as provide 'a tuned reactance for the signal voltage. The signal and idler terminals can be interchanged depending upon the relative frequencies as hereinbefore described.

FIG. 10 illustrates another possible microwave equivalent of a one-port parametric amplifier as described in FIG. 3. The bridge of

variable reactance diodes

20, 21, 22, 23 have

cross terminals

32, 33 and 26, 27 as before. The pump voltage is provided by a waveguide type feed through pump waveguide 71 to the

terminals

32, 33 representing one port. The signal input is provided through a phase reversing power divider 72. The signal input is coaxial providing a hybrid feed as is known in the art. The coaxial signal input is connected to

opposite bridge terminals

26, 27. The idler currents are generated such that they are confined to the bridge diodes and are independent of the waveguide circuitry as hereinbefore explained.

It is understood that the diode bridge is usually mounted in a ceramic or glass package to facilitate connections to other components. However, the diode could also be mounted as chips without the aid of special packaging.

While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the scope of the invention.

What I claim as new and desire to secure by said Let ters Patent is:

l. A parametric amplifier comprising:

a. four substantially matched variable reactance diodes connected in a double balanced bridge arrangement, each of said diodes positioned in its respective bridge arm in opposite poled arrangement with the diodes in both adjacent bridge arms;

b. means for supplying a pump voltage frequency across a first pair of diagonally opposing bridge terminals;

c. means for supplying a signal voltage across a second pair of diagonally opposing bridge terminals; and

(1. means for containing the developed idler voltage completely within the bridge arrangement and independent of external loads.

2. A parametric amplifier as in claim 1 and wherein said means for supplying a pump voltage frequency and said means for connecting a signal voltage frequency each include filter means to permit the passage of the frequency supplied but isolating the other frequencies.

3. A parametric amplifier as in claim 1 and further including DC bias means for applying and returning a DC bias to said diodes.

4. A parametric amplifier as in claim 1 for use at microwave frequencies as a' one-port amplifier further comprising a housing, a dielectric substrate mounted in said housing, first and second coaxial connections for respectively connecting with the pump frequency source and the signal frequency source, said coaxial connections mounted on said housing, said diode bridge arrangement mounted onto said substrate, first the opposite side of the substrate whose width at one end matches the coaxial connections and being tapered until the other end matches the width of said first metallic strip, and a plurality of miniature coils connected to said bridge for supplying and removing a DC bias from each side.

5. In a parametric amplifier having a double balanced bridge arrangement of four substantially matched variable. reactance diodes and supplied with pump and signal frequencies along unbalanced coaxial cables, the balancing arrangement comprising balanced microstrip baluns having a first and second metallic strip separated by a dielectric wherein said first metallic strip is at a uniform width and said second metallic strip is tapered from its broad end matching the unbalanced coaxial cable to its narrow end matching the width of said first metallic strip.

6. A parametric amplifier as in claim 5 wherein each of said diodes is arranged within its respective bridge arm in opposite poled arrangement with the diodes in both adjacent bridge arms.

Claims

1. A parametric amplifier comprising: a. four substantially matched variable reactance diodes connected in a double balanced bridge arrangement, each of said diodes positioned in its respective bridge arm in opposite poled arrangement with the diodes in both adjacent bridge arms; b. means for supplying a pump voltage frequency across a first pair of diagonally opposing bridge terminals; c. means for supplying a signal voltage across a second pair of diagonally opposing bridge terminals; and d. means for containing the developed idler voltage completely within the bridge arrangement and independent of external loads.

4. A parametric amplifier as in claim 1 for use at microwave frequencies as a one-port amplifier further comprising a housing, a dielectric substrate mounted in said housing, first and second coaxial connections for respectively connecting with the pump freQuency source and the signal frequency source, said coaxial connections mounted on said housing, said diode bridge arrangement mounted onto said substrate, first and second balanced microstrip transformers each respectively connected to said first and second pair of diagonally opposing bridge terminals, first and second balanced microstrip baluns respectively interconnected between said coaxial connections and said transformers, said baluns having a first metallic strip on one side of said substrate with a uniform width whose width matches the transformer, and a second metallic strip on the opposite side of the substrate whose width at one end matches the coaxial connections and being tapered until the other end matches the width of said first metallic strip, and a plurality of miniature coils connected to said bridge for supplying and removing a DC bias from each side.

5. In a parametric amplifier having a double balanced bridge arrangement of four substantially matched variable reactance diodes and supplied with pump and signal frequencies along unbalanced coaxial cables, the balancing arrangement comprising balanced microstrip baluns having a first and second metallic strip separated by a dielectric wherein said first metallic strip is at a uniform width and said second metallic strip is tapered from its broad end matching the unbalanced coaxial cable to its narrow end matching the width of said first metallic strip.