JPH06148242A - Yig tuning mixer circuit - Google Patents

Abstract

PURPOSE: To improve sensitivity of a spectrum analyzer by supplying high frequency signal to a tunable band pass filter and the first-the fourth YIG tuning resonators which constitute an imaging improving double balanced mixer, and then applying an even DC magnetic field with an electronic magnet, for tuning four resonators. CONSTITUTION: A YIG tuning resonator filter and mixer circuit is provided with four gloves wherein a routing circuit 102 and two PIN diode microwave integrated circuits are combined and a YIG tuning pre-selector 104, and, it acts as a tunable band pass filter for attenuating needless mixed-frequency. In relation with the fourth YIG glove, a GaAs monolithic integrated circuit comprises odd and even IF ports 106 and 107, and acts as an imaging improving double balanced YID tuning mixer. For obtaining a required signal output IF, the pre-selector 104 is tuned with an input signal RF, and after a local oscillator signal is added to the mixer, an IF switch 108 is switched according to harmonics number.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electronic measuring instruments for detecting or measuring electrical signals, and more particularly to detecting the frequency spectrum of electrical signals, for example from DC to radio frequency (RF). Or, it relates to an electronic measuring instrument. In particular, one embodiment of the present invention provides a routing yttrium iron garnet (YIG) tuned mixer that is particularly adaptable for use in electronic measuring instruments known as spectrum analyzers. Such a mixer can be an odd harmonic mixer or an even harmonic mixer, preferably a switched odd or even harmonic mixer, but routed in combination with at least one other YIG tuned resonator. YIG tuned resonator filters and mixers can also be formed.

[0002]

BACKGROUND OF THE INVENTION Generally, a spectrum analyzer is a scanning receiver that displays the power and modulation characteristics of an electrical input signal over a predetermined frequency band. In order to cover a wide frequency range, for example 0 to 26.5 GHz, it is desirable to split the input signal into a low frequency part and a high frequency part. One aspect of the present invention relates to effectively allocating a route of an input signal between a low frequency signal processing unit and a high frequency signal processing unit of a spectrum analyzer according to a frequency of the input signal.

In this regard, FIG. 1 shows a block diagram illustrating the first signal processing circuit, or "front end," of a conventional spectrum analyzer. Initially, all input signals applied to the input 11 of the spectrum analyzer, for example signals in the frequency range 0 to 26.5 GHz, pass through a step attenuator 12 to a mechanical microwave relay switch 13, which relay switch 13 Selectively sends the input signal to the low frequency signal processing unit via the line 14 or to the high frequency signal processing unit via the line 15. Unfortunately, mechanical microwave relay switches are slow and wear out under heavy use.

On the other hand, low frequency input signals, eg 2.9 GHz
The lower input signal is applied to the low frequency signal processor of the spectrum analyzer. Input signals from 0 to 2.9 GHz are low-pass filter 17, swept YIG tuned local oscillator (LO) 18,
It is switched to the first converter 16 composed of a mixer 19 and a bandpass filter 20. The converter 16 up-converts the low frequency input signal into a constant intermediate frequency (IF) output signal which is applied to the low frequency analysis circuit (not shown) of the spectrum analyzer. On the other hand, high frequency signals, for example 2.
An RF (microwave) input signal with a frequency between 7 and 26.5 GHz passes through a tunable bandpass filter 21.
The passed RF input signal is then down converted by the harmonic mixer 22. The harmonic mixer 22 is a frequency suitable for mixing the RF input signal with the signal generated by the local oscillator (LO) 23 or with the harmonics of the signal from the LO for further processing by the high frequency analysis circuit (not shown) of the spectrum analyzer. Generates a predetermined IF output signal of.

Spectral analysis measurements are performed on the high frequency RF input signal by sweeping the LO signal frequency over a frequency range of interest while monitoring a given IF frequency. The graph of FIG. 2 shows the result of down conversion by the harmonic mixer 22 shown in FIG.
It clearly shows the relationship between each frequency. In FIG. 2, the vertical axis represents signal power, and the horizontal axis represents signal frequency. The frequency of the given IF signal 25 is LO signal (or harmonic) 27 and RF
Since the difference between input signal 29 and RF input signal is LO
Lower than the frequency of the signal is measured by monitoring the set IF frequency of _{f RF = (n) f LO} -f IF. However, the image RF signal at f _RF '= (n) f _LO + f _IF , which is higher than the frequency of the LO signal, also produces a signal at the monitored IF frequency. To resolve this ambiguity, the tunable bandpass filter 21 shown in FIG.
It acts as a tunable bandpass filter over a frequency range including _RF , thereby attenuating all image signals 33 at f _RF '. Therefore, in the pass band of the tunable band pass filter 21 shown in FIG. 1, the center frequency of the pass band is LO.
The swept LO signal must be tracked with the IF signal frequency distant from the frequency (or harmonics).

The tunable bandpass filter shown in FIG.
21 can be a YIG tuned resonator filter or preselector consisting of a YIG sphere suspended between two orthogonal half-loop conductors with the center of the YIG sphere at the intersection of the loop axes.
When the YIG sphere is not magnetized, there is no interaction between the RF input signal and the ferrite (YIG) sphere, and the loops are perpendicular to each other, so the RF input signal is not transmitted between the half loops. However, if there is an externally applied DC magnetic field along the axis perpendicular to the half-loop, the dipole inside the YIG sphere will be DC.
It aligns with the magnetic field and produces a strong net magnetization, M, in the YIG sphere. The RF input signal applied to the input half-loop therefore produces an alternating RF magnetic field perpendicular to the externally applied DC magnetic field,
The dipole inside precesses around a DC magnetic field at the frequency of the RF input signal. The frequency of precession is equal to the frequency of the RF input signal if the frequency of the RF input signal is equal to or very close to the dipole resonance frequency of the spherical YIG resonator. The resonance frequency of the spherical YIG resonator is f _r = γ (H _o ± H _a ). Where H _o is the strength of the externally applied DC magnetic field expressed in Oersted, H _a is the internal anisotropic field inside the YIG material (represented by Oersted), and γ is the gyromagnetic ratio (2.8 M
Hz / Oersted).

[0007] as long addition to the RF input signal is input half loop close to f _r or f _r, YIG material, so precession dipoles produce a circularly polarized magnetic field, shows the co magnetic resonance, externally applied Rotate at the frequency of the RF input signal in a plane perpendicular to the applied DC magnetic field. This rotating magnetic field couples to the output half loop including an RF signal in the output half-loop are shifted resonance frequency f _r 90 degrees phase from the RF input signal. The YIG tuned resonator filter therefore acts as a gyrator. The phase shift in one direction due to the YIG tuned resonator filter differs by 180 from the phase shift in the other direction. The filter function is achieved because RF input signals that are more than a small amount away from the dipole resonance frequency do not couple to the YIG sphere. Since the resonance bandwidth can be made quite narrow, the YIG resonator has a very selective bandpass filter at the RF frequency that can be tuned by changing the strength of the externally applied DC magnetic field. There is. Typical load Q values for YIG tuned resonator filters range from 100 to 400.

However, the prior art circuit shown in FIG. 1 has several disadvantages. RF input signals with frequencies in the range 2.7 to 26.5 GHz are switched to a wide band YIG tuned resonator filter 21 used as a preselector. The filtered signal is applied to the harmonic mixer 22 where it is swept.
YIG tuned local oscillator (LO) 23 is mixed with a fundamental wave or a harmonic wave to generate a predetermined IF output signal. This method has the disadvantage that the microwave harmonic mixer is inefficient, which dramatically reduces the sensitivity of the microwave spectrum analyzer, especially when mixed with high harmonics at high frequencies. Fundamental mixing has been used to overcome the problem of desensitization. This is a wideband LO (ie 5 to 26.5GH
z) or with a narrow band LO (ie 3 to 6.8GH
This is accomplished by multiplying the frequency of the signal from z) to create a wideband LO source for the harmonic mixer 22. Although these methods offer performance advantages, they are expensive to implement.

In addition, a schematic diagram of one known integrated harmonic mixer 22 is shown in FIG. 1A. The mixer comprises a diode D whose first end is connected to the output coupling loop of a YIG tuned resonator. The other end of the diode is connected to one end of the transmission line TL, the other end of which is connected to the LO signal coupler. Narrow band, eg 3 to 6.8 GHz,
The LO signal of is coupled to the transmission line TL via the LO signal coupler. The RF, LO, and IF signals are not isolated. R
The F, LO, and IF currents all flow through the transmission line TL. Harmonic mixing is performed by biasing diode D through resistor R. The following drawbacks are obvious.

LO signal, RF signal, image, and multiple (multi
ple) mixed result signals must all flow through the transmission line TL, ending with an AC load. There is no image enhancement where higher order mixed signals are retroreflected by the mixer for further mixing. Also, the AC load must be a broadband load that keeps the mixer response flat over the frequency range of interest. In addition, harmonic mixing is done by biasing diode D. This set of mixers (one diode biased for different harmonics) is not efficient.

A schematic diagram of another known harmonic mixer 22 is shown in FIG. 1B.
Shown in. This mixer is a single balanced fundamental odd harmonic mixer as described in US Pat. No. 4,817,200. The LO and RF signals are separated by the balun effect of the full output coupling loop. This mixer has a frequency f _IF = (2n +
1) f _LO ± f _{RF is} an odd harmonic mixer in which IF signal flows through port 1 and port 2. The LO and RF signals are isolated, eliminating the need for a broadband microwave load required for single diode mixing with the mixer shown in Figure 1A. However, the IF signal must be duplexed from the LO signal through port 1 and port 2 using inductor L and capacitor C. Inductor L is the return path for the IF signal at frequency f _IF = (2n + 1) f _LO −f _RF , but the mixed signal at frequency f _IF = (2n + 1) f _LO + f _RF flows through port 1 to the LO source impedance. Therefore, a mixed signal of frequency (2n + 1) f _LO + f _RF (n = 0 is the image frequency) must be transmitted through the port and terminated at the LO source load. Improvements in image and multiple mixed signals are not achieved.

[0012]

OBJECTS OF THE INVENTION It is an object of the present invention to provide a broadband routing YIG tuned resonator mixer and filter for providing a highly sensitive spectrum analyzer.

[0013]

SUMMARY OF THE INVENTION One embodiment of the present invention is broadband routing.
YIG tuned resonator mixers and filters are provided, where the low frequency signal is at the low frequency output and the high frequency signal is
It is preferably sent to a YIG tuned resonator and mixed to form a tunable bandpass filter and an image enhancing double balanced mixer. The electromagnet has four components that adjust the resonance frequency of the resonator.
A uniform DC magnetic field is generated through the YIG resonator. First
YIG resonator acts as the first stage of the filter, with two PINs
In cooperation with a routing circuit consisting of diodes, it routes the input signal to the low frequency output or to the subsequent stages of the filter and mixer. The second YIG resonator acts as the second stage of the filter. The third YIG resonator acts as the third stage of the filter. The fourth YIG resonator acts as a fourth stage of the filter and as an image enhancing double balanced mixer capable of odd or even and preferably switched odd or even harmonic mixing without the need to bias the mixer. Also works. Mixer
Generates an IF output signal at the IF output by mixing the RF input signal with the fundamental or harmonic of the swept local oscillator (LO) signal.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A block diagram of a preferred embodiment of a routing YIG tuned resonator filter and mixer circuit, indicated generally at 100, in accordance with the present invention is shown in FIG. The routing YIG tuned resonator filter and mixer circuit 100 comprises an electronically switched YIG tuned resonator integrated with a double balanced image enhancing YIG tuned mixer to overcome mechanical switching speed and reliability issues. Increasing the sensitivity of the spectrum analyzer. Routing YIG
The tuned resonator filter and mixer circuit 100 incorporates a diode bridge mixer circuit configuration and preferably employs a high level of integration. The routing YIG tuned resonator filter and mixer circuit 100 can be incorporated into, for example, a high performance portable spectrum analyzer.

As shown in FIG. 3, a routing YIG tuned resonator filter and mixer circuit 100 includes a routing circuit 102 and two PIN diode microwave integrated circuits (M
The four spheres, YI, in which the input spheres combined with IC) have been replaced in place of conventional mechanical microwave relay switches.
The G tuning preselector 104 is provided. Preselector 104
Operates as a highly selective tunable bandpass filter that attenuates unwanted mixed signals such as image and multiple responses. In connection with the fourth YIG sphere, a GaAs monolithic Schottky diode integrated circuit is provided with preferably isolated odd and even IF ports, 106 and 10, respectively.
7, very efficient image enhancement double balanced YIG with
It operates as the tuning mixer 105. To obtain the desired mixed signal, the preselector 104 is tuned to the frequency of the RF input signal, a qualified local oscillator (LO) signal is added to the mixer 105, and the IF switch 108 is turned on, depending on the number of mixed harmonics required. Mixer 105
A predetermined IF signal output is extracted by switching to the even or odd IF port 106 or 107.

As shown in FIG. 4, the routing YIG tuned resonator filter and mixer circuit 100 is mounted on a conductive chassis 109, which is typically constructed of metallized plastic or metallized high resistance metal. The routing YIG tuned resonator filter and mixer circuit 100 preferably comprises an input resonator 110, a first intermediate resonator 112, a second intermediate resonator 114, and an output resonator 116. The chassis 109 is provided with openings for mounting related circuits in addition to the resonators 110, 112, 114, and 116. Resonator 11
0, 112, 114, and 116 are inputs 11 to which the input signal is applied
8 in series with the IF output 120, which is preferably configured from odd and even IF ports 106 and 107. Preferably, the input 118 is a low frequency output 1 as described below.
It is also connected to 22. Input 118, IF output 120, and low frequency output 122 can be in the form of coaxial connections, as shown in FIG.

The input resonator 110 comprises a YIG sphere 124 mounted between the input coupling loop 126 and the coupling loop 128. The resonator 112 comprises a YIG sphere 130 mounted between a coupling loop 128 and a coupling loop 132. Resonator 114 is a YIG mounted between coupling loop 132 and coupling loop 138.
It has a ball 136. Output resonator 116 comprises a YIG sphere 140 mounted between coupling loop 138 and output coupling loop 142. YIG spheres 124, 130, 136, and 140 are supported by support rods 144, 146, 148, and 150, respectively, which are electrically insulated and non-magnetic.

Each coupling loop 126, 128, 132, 138, and
142 is electrically conductive. The input coupling loop 126 forms a half loop, the first end of which is connected to the input 118. Coupling loops 128, 132, and 138 each consist of a double half loop for connecting a subsequent resonator. The output coupling loop 142 has a full loop structure that is operationally equivalent to the half loop connected to the IF output 120. The input and output coupling loops of each resonator are preferably quadrature, but can be deviated from quadrature up to about 10 degrees without significant performance degradation. As shown in FIG. 4, the coupling loops 126, 128, 132, 13
8 and 142 are arranged in a zigzag pattern, and adjacent resonators 11
The spacing between 0, 112, 114, and 116 can be as desired.

As shown in FIG. 4, the first end of input coupling loop 126 is connected to input 118, but coupling loop 126
The second end of is preferably connected to the routing circuit 102. On the other hand, the routing circuit 102 couples the input signal in the frequency range, for example 0 to 2.9 GHz, to the low frequency output 122. A conventional low frequency signal processor (not shown) can be connected to the low frequency output 122. On the other hand, the routing circuit 102 couples the RF input signal greater than about 2.7 GHz by the YIG sphere 124 from the input coupling loop 126 to the coupling loop 128. The routing circuit 102 will be described in more detail later. In an alternative embodiment that attempts to process only high frequency signals, the routing circuit 102 is eliminated and the second end of the input coupling loop 126 is connected to ground (common).

As shown in FIG. 5, the external DC magnetic field H _o is
110, 112, 114, and 116 (in FIG. 5, YIG sphere 1
24, 130, 136, and 140). The DC magnetic field H _o is generated by an electromagnet 160 with a coil 162. Resonators 110, 112, 114, and 116 are fixed spheres 164.
And the rotatable magnetic pole piece 166. The rotatable pole piece is a co-pending application, YIG-TUNED CIRCUIT WITH RO, filed concurrently with this application under the name Hassan Tanbakuchi.
TATABLE MAGNETIC POLEPIECE (Y with rotatable pole pieces
IG Tuning Circuit), the disclosure of which is incorporated herein in its entirety by this reference. Resonator
110, 112, 114, and 116, such information is generally placed in a plane perpendicular to the direction of the DC magnetic field H _o. By varying the magnitude of the DC magnetic field H _o to control the current flowing into the coil 162 of the electromagnet 160, causing the resonant frequency of the resonator 110, 112, 114, and 116 is tuned to the required frequency range. In particular, DC magnetic field H _o
The resonant frequency becomes higher as ω increases.

Referring again to FIG. 4, the YIG sphere support rod 1
44, 146, 148, and 150 are mounted on ball positioning assemblies 184, 186, 188, and 190, respectively. Sphere positioning assemblies 184, 186, 188, and 190 are YIG sphere 12
It allows the position of each of 4, 130, 136, and 140 to be adjusted in three Cartesian directions (ie, along the X, Y, and Z axes) and the rotation of each YIG sphere. Sphere positioning assemblies 184, 186, 188, and 190 ensure that each YIG sphere is optimally positioned with respect to its associated input / output coupling loop. In addition, the sphere positioning assemblies 184, 186, 188, and 190 have YIG spheres 124, 13
Rotate 0, 136, and 140 so that the crystal axis of each YIG sphere is in the required orientation with respect to the DC magnetic field H _o . Sphere Positioning Assemblies 184, 186, 188, and 190, YIG SPHERE POSITIO, a co-pending patent application filed concurrently with this application under the names of Thomas W. Finkle and Terry A. Jones.
NING APPARATUS (YIG Sphere Positioning Device) is described in detail, the entire disclosure of which is incorporated herein by this reference.

In the exemplary embodiment of the routing YIG tuned resonator filter and mixer circuit 100 shown in FIG.
The diameter of 124, 130, 136, and 140 is approximately 0.3 mm, and the radius of each coupling loop 126, 128, 132, 138, and 142 is approximately
It is 0.4 mm. YIG sphere support rods 144, 146, 148, and 1
50 is preferably aluminum oxide. Binding loop 12
The ends of 8, 132, and 138 are grounded.

In operation, the input signal received at input 118 causes current to flow through input coupling loop 126. In the preferred embodiment with routing circuit 102, for example,
An input signal at a frequency of 0 to 2.9 GHz is passed from the input coupling loop 126 through the routing circuit 102 to the low frequency output 122.
Flow to. For example, an input signal with a frequency from 2.7 to 26.5 GHz will cause an RF current in the coupling loop 126, which causes Y
An RF magnetic field is generated near the IG sphere 124. Without the YIG sphere 124, the RF field will not couple to the quadrature coupling loop 128.
However, when an externally applied DC magnetic field H _o causes the YIG sphere 124 to have a resonant frequency at or near the frequency of the RF input signal, the RF signal causes the dipoles of the YIG sphere 124 to precess at the frequency of the RF signal. . The precession dipole produces a circularly polarized RF magnetic field, which couples with the coupling loop 128. Therefore, the resonator 110 is
It carries an RF signal at the same or nearly the same resonant frequency as the G sphere 124. Resonators 112, 114, and 116 operate in the same manner to become a very selective tunable RF bandpass filter. By varying the DC magnetic field H _o which serves to vary the current through the coil 162 of the electromagnet 160, the resonator 11
The passband of the tunable bandpass filter consisting of 0, 112, 114, and 116 is tuned over a wide frequency range.

In the embodiment of the routing YIG tuned resonator filter and mixer circuit 100 shown in FIG. 4, the output resonator 1
The 16 also includes an image enhancement double balanced YIG tuned mixer 105. LO signal is LO input 194 and microstrip circuit 1
Add to mixer 105 through 96. LO input 194 can be in the form of a coaxial connection as shown in FIG. Preferably, the IF output signal of mixer 105 is divided into an odd number depending on whether an odd or even harmonic mixing signal occurs.
IF output 120 consisting of IF port 106 and even IF port 107
Appear in. The mixer 105 will be described in more detail later. But first, the routing circuit 102
Will be described next.

Preferably, the mechanical microwave relay switch comprises a routing circuit 102 that forms a dual shunt PIN diode with the routing YIG tuned resonator filter and the YIG tuned resonator filter of mixer circuit 100, as shown in FIG. Are eliminated by incorporating. In one aspect of the present invention, the routing circuit 102 has the following circuit configuration, and alternately performs the required switching operation in the low frequency band and the high frequency band as follows. As shown in FIG.
The input signal applied to input 118 propagates through input coupling loop 126. The input coupling loop 126 associated with the routing circuit 102 and the associated bias circuit 202 provide a low frequency input signal to the low frequency output 122, as described in more detail below.
And a high-frequency input signal is coupled to the coupling loop 128 through the input resonator 110 and down-converted to form a low-loss electronic switch. On the other hand, for example, from 0
Input signals in the frequency range up to 2.9 GHz are transmitted to the low frequency output 122 with a maximum loss of 1 dB. On the other hand, the RF input signal in the frequency range from 2.9 to 26.5 GHz is coupled to the input resonator 110 by the input coupling loop 126.

As shown in FIG. 4 and FIG.
Circuit 102 is coupled to the second end of input coupling loop 126 and the low frequency output.
The first transmission line TL connected in series with the force 122₁and
Second transmission line TL₂Is equipped with. Routing circuit 102
Is, on the other hand, a second end of the input coupling loop 126 and a first conductor.
Transmission line TL₁In series between the junction with and on the other hand the earth
Connected capacitor C₁And diode D₁Also equipped with
There is. The routing circuit 102 further includes, on the one hand, the first and
Second transmission line TL₁And TL₂To the junction, and on the other hand to the ground
Capacitor C connected in series between₂And diode
D ₂Is equipped with. Diode D₁And D₂Is preferably a PIN
It is a diode. In addition, the routing circuit 102 is
The ass circuit 202 is provided. Bias circuit 202 has a first end
Is the capacitor C₁And diode D₁Connected to the junction with
Resistor R₁, And the first end is capacitor C₂And dio
D₂Resistor R connected to the junction with₂Equipped with
Resistor R₁And R₂The second end of each of the resistors is a resistor R₃The first
It is connected to one end. Resistor R₃The second end of the is inda
Connected to the first end of the inductor L
Is preferably a series of coils L, as shown in FIG.₁, L₂,
L₃, And L_FourIt consists of Capacitor C₃Is in
It is connected between the second end of the ductor L and the ground. Ba
The bias voltage V + is selectively connected to the second end of the inductor L
Being a diode D₁And D₂Biased to "on" at the same time
To do. Diode D otherwise₁And D₂Is "O
"F".

In operation, a low frequency input signal from 0 to 2.9 GHz is applied to the low frequency output 122, and thus the low frequency signal processor (not shown), by biasing diodes D ₁ and D ₂ “off”. ). Due to the combination of the input coupling loop 126 and the inductance of the transmission lines TL ₁ and TL ₂ and the “off” capacitance of the diodes D ₁ and D ₂ , for example, input signals below 2.9 GHz are only slightly affected (ie the insertion Loss ≤ 1dB), low frequency output 12
A low pass filter is created that passes up to 2. From 2.7
For RF input signals up to 26.5 GHz, diodes D ₁ and D ₂ are forward biased (“turned on”) by applying a bias voltage V +, which provides a low impedance at the second end of input coupling loop 126. Show. This ensures that the RF input signal is efficiently coupled to the YIG sphere 124.

Considering in more detail, the routing circuit
The 102 operates as follows. From 0 added to input 118
Signals in the frequency range up to 2.9 GHz flow through the input coupling loop 126. With diodes D ₁ and D ₂ reverse-biased (“off”), the “off” capacitances of diodes D ₁ and D ₂ are coupled to input coupling loop 126 and first and second transmission lines TL ₁ and TL. Together with the inductance of ₂ , a low loss low pass filter with a cutoff frequency of preferably 6 GHz is constructed. Biasing circuit 202 causes resistors R ₁ , R ₂ , and R _{3 to} be coupled to the first of input coupling loop 126 as the frequency of the input signal rises above, for example, about 100 MHz, thus reducing the impedance of capacitors C ₁ and C ₂ . It is configured to appear as a load at the junction between the end of 2 and the transmission line TL ₁ . In addition, an inductor L composed of coils L ₁ , L ₂ , L ₃ , and L ₄ and a capacitor C ₃
Is a resistor R ₁ , as the frequency of the input signal increases,
R ₂ and R ₃ increase the effective impedance presented to capacitors C ₁ and C ₂ .

For RF input signals in the frequency range from 2.7 to 26.5 GHz, diodes D ₁ and D ₂ are forward biased (“turned on”). As a result, the diode D ₁ has a very low impedance at the second end of the input coupling loop 126, allowing the RF input signal to be coupled through the YIG sphere 124.
Combine to 128. The low frequency output 122 is connected to an unknown impedance in parallel with a series combination of diode D ₁ and capacitor C ₁ and associated connecting inductance,
At some frequencies in the frequency band from 2.7 to 26.5 GHz, parallel resonance can occur if capacitor C ₂ and diode D ₂ are not present. However, if there is a diode D ₂ and a capacitor C ₂ that are forward biased (“on”), the unknown impedance connected to the low frequency output 122 will be low for capacitor C ₂ and diode D ₂ . "on"
Capacitor C with an unknown impedance connected to the low frequency output 122, loaded by a series combination of resistors.
The possibility of parallel resonance of ₁ and diode D ₂ is avoided.

Referring again to FIG. 4, the routing YIG
In the tuned resonator filter and mixer circuit 100, a four stage YIG tuned bandpass filter or preselector 104 composed of resonators 110, 112, 114 and 116 is used to provide a high degree of selectivity (image and multiple Mixed result signal
90 dB or more) is achieved. The RF input signal in the frequency range from 2.7 to 26.5 GHz is filtered by the first, second and third stages of the preselector 104 and then added to the fourth stage. The fourth stage, consisting of the resonator 116, acts both as the fourth filter stage and as the image enhancing double balanced YIG tuned mixer 105, down converting the RF input signal to the desired IF output signal.

FIG. 7 shows a schematic diagram of the image enhancing double balanced YIG tuning mixer 105 in addition to the fourth stage of the preselector 104. As shown in FIGS. 4, 7, and 8, the mixer 105
Is composed of the second half loop of coupling loop 138 and full output coupling loop 142. The output coupling loop 142 ends at the first end with a capacitor C ₄ , and a diode D ₃ ,
It terminates at the second end with a monolithic GaAs diode integrated circuit consisting of a diode bridge with D ₄ , D ₅ , and D ₆ . Diodes D ₃ , D ₄ , D ₅ , and D ₆ are preferably Schottky diodes. Diodes D ₃ , D ₄ ,
There is no need to bias D ₅ and D ₆ . The mixer 105 also comprises a capacitor C ₅ connected between each end of the capacitor C ₄ and ground. The mixer 105 further includes a first IF unbalance transformer 302 having an input connected in parallel with a capacitor C ₄ at a first end of the output coupling loop 142.
Is equipped with. IF balanced-unbalanced transformer 302 is an even harmonic IF
Operates as a balanced-unbalanced transformer. IF balanced-unbalanced transformer
The output of 302 is connected to odd IF port 107.

As shown in FIGS. 4 and 7, the image enhancement double balanced YIG tuned mixer 105 has a diode bridge D ₃ ,
Capacitors Connected Across D ₄ , D ₅ , and D ₆
It has a C ₆ . The mixer 105 further comprises a capacitor C ₇ connected in series across the capacitor C ₆ .
The junction between capacitors C ₇ is connected to LO input 194. The image-enhancing double-balanced YIG tuned mixer 105 also comprises inductors L ₅ and L ₆ whose first end is connected to the respective junction of the capacitor C ₆ on the one hand and to the capacitor C ₇ on the other hand. Mixer 105 further includes a second input whose input is connected across the second ends of inductors L ₅ and L ₆ .
The IF balance unbalance transformer 304 is provided. The IF balance-unbalance transformer 104 operates as a fundamental wave and odd harmonic IF balance-unbalance transformer. The output of the IF balance / unbalance transformer 304 is connected to the odd IF port 106. Finally, the mixer 105
On the one hand is the inductor L ₅ and the IF balanced-unbalanced transformer 30
4 and a capacitor C ₈ connected between the respective junctions of the inductor L ₆ and the IF unbalance transformer 304, and on the other hand to ground.

The YIG sphere 140 is R flowing through the coupling loop 138.
The F input signal is converted to a balanced circular current that flows into output coupling loop 142 via capacitor C ₄ . Output coupling loop 142
And the combination of the capacitor C ₄ works effectively as a tunable microwave balanced-unbalanced transformer. The circulating RF input signal mixes with the LO signal applied to the LO input 194, or an appropriate harmonic of the LO signal, resulting in an odd or even harmonic mixed signal at the odd or even IF port 106 or 107, respectively. To achieve improved image and multiple mixed signals,
Capacitors C ₄ and C ₆ are included and the high frequency mixed signal (ie, ≧ 3 GHz) is retroreflected to mixer 105 and remixed.
This is a very efficient mixer. Odd or even
The only mixed signal that flows to the IF port 106 or 107 is a predetermined IF signal (for example, f _IF = 310.7 MHz). As shown in Fig. 7, the required harmonic mixed signal is selected by the preselector.
Tune the 104 to the RF input signal and get the correct LO signal to the mixer 105
In addition, by switching the IF switch 108 to the odd or even IF port 106 or 107.

The LO and odd harmonic IF signals are fed by capacitor C ₇
And duplexed through C ₈ and inductors L ₅ and L ₆ . Nodes 1, 2, 5, and 6 are virtual ground ports for RF input signals. Nodes 5 and 6
The AC ground node for the LO signal, creating the LO return path through capacitor C ₅ . The odd harmonic mixed signal enters node 1 and exits node 2. Nodes 3 and 4 are odd harmonic mixed signals (ie, f _IF = (2n + 1) f _LO ± f _RF ).
Is a virtual ground port for. Capacitor C ₆ is shorted to the odd IF creation signal at high frequencies. The high frequency short circuit retroreflects the high frequency odd harmonic mixed signal back to mixer 105 for remixing. This remixing increases the efficiency of mixer 105 at a given IF (ie, image and multiple enhancement).
At the same time, a given IF signal can flow to the IF balance / unbalance transformer 304. The even mixed creation signal flows out from the node 4 and flows into the node 3. Also, nodes 1 and 2 are virtual ground ports for even mixed signals (ie, f _IF = 2nf _LO ± f _RF ). The capacitor C ₄ becomes a short circuit for the even harmonic IF generation signal at high frequencies. The high frequency short circuit retroreflects the high frequency even harmonic mixed signal back to mixer 305 for remixing. This remixing increases the efficiency of the mixer 105 at a given IF (ie, image and multiple enhancement) so that only the given IF can flow to the IF balance-unbalance transformer 302. The odd and even IF ports 106 and 107 are isolated. Therefore, odd IF port 106 does not load even IF port 107. The reverse is also true.

The signal paths for the LO, RF, and even and odd IF currents are shown in FIG. 9A as image enhancement double balanced YIG tuned mixer 105.
Further details can be considered in connection with the schematic diagram of FIG.
The LO signal is applied through capacitor C ₇ . Inductor
The combination of L ₅ and L ₆ and the capacitor C ₈ appears as a high impedance to the LO signal, little effect on the order LO signal power. The LO current flows through diodes D ₄ and D ₆ during the positive half cycle of the LO signal,
During the negative half cycle of the signal, it flows through diodes D ₃ and D ₅ , which are in series with output coupling loop 142 and capacitor C ₅ , but with forward biasing of each diode pair. Turn it on. LO
The signal is isolated from the RF inputs that make up the second half-loop of the coupling loop 138 because the complete output coupling loop 142 is orthogonal to the coupling loop 138. The LO current flows through the output coupling loop 142 in common mode and the YIG sphere 140 is tuned to the frequency of the RF input signal.

Each diode D ₃ , D ₄ , D ₅ , and D ₆ is
It can be represented by a time-varying inductance, as shown in 9B. Conductance g (t) represents the time-dependent conductance of diodes D ₄ and D ₆ as driven by the positive half cycle of the LO signal. Similarly, diodes D ₃ and D ₅ are driven by the negative half cycle of the LO signal and g (t + T
/ 2). Here, T is the period of the LO signal.
The RF input signal from the third stage of the filter is applied to the second half loop of coupling loop 138. This induces a balanced circulating RF current in the full output coupling loop 142. Node 1,
Node 2, node 3, and node 4 are virtual ground ports for RF input signals. Therefore, the RF input signal is the LO input
Isolated from 194 and odd and even IF ports 106 and 107.

As shown in FIG. 9C, the diodes D ₃ , D ₄ ,
The current through D ₅ and D ₆ is given by: i ₁ (t) = V _RF · g (t + T / 2) i ₂ (t) = V _RF · g (t) i ₃ (t) = − V _RF · g (t + T / 2) i ₄ (t) = −V _RF・ g (t)

By performing the Fourier transform of the above equation, it is possible to analyze the current at frequencies for all combinations of LO signals, RF input signals, and mixed product signals. The asterisk ( ^* ) in the following equation is the convolution function
Represents i ₁ (f) = V _RF (f) ^* G (f) ・ exp (j2πfT / 2) i ₂ (f) = V _RF (f) ^* G (f) i ₃ (f) = -V _RF (f ) ^* G (f) ・ exp (j2πfT / 2) i ₄ (f) = −V _RF (f) ^* G (f) current i ₁ (f), i ₂ (f), i ₃ (f), and i ₄ (f) represents all possible mixed signals between the LO signal and the RF input signal in the frequency domain.

The currents I ₁ (f), I ₂ (f), I ₃ (f), and I ₄ (f) shown below flow out of the diode bridges D ₃ , D ₄ , D ₅ , and D _6. This is a current flowing into the nodes 1 to 4. I ₁ (f) = i ₁ (f) −i ₂ (f) = V _RF (f) ^* G (f) [exp (j πfT) −1] I ₂ (f) = i ₄ (f) −i ₃ (f) = V _RF (f) ^* G (f) [exp (j πfT) −1] I ₃ (f) = i ₁ (f) −i ₄ (f) = V _RF (f) ^* G ( f) [exp (j πfT) +1] I ₄ (f) = i ₂ (f) −i ₃ (f) = V _RF (f) ^* G (f) [exp (j πfT) +1] LO is pure For a spectrum analyzer that is a sinusoidal signal, these equations can be written as:

[0040]

[Equation 1]

In equations 1 and 2, since f _LO = 1 / T, the expression [exp (jnπf _LO T) −1] becomes the expression [exp (jnπ) −1], and the real part of n is It is equal to 0 when it corresponds to an even number. Also, the expression [exp (jnπf _LO T) +1] becomes the expression [exp (jnπ) +1], and its real part is equal to 0 when n corresponds to an odd number. Equations 1 and 2 can be transformed into the following equations:

[0042]

[Equation 2]

From equation 3 it is clear that the real part of the current flowing into nodes 1 and 2 is only the odd harmonics of the LO signal which mix with the RF input signal. The even harmonic mixed signals are canceled. Similarly, it is clear from Equation 4 that the real part of the current flowing into nodes 3 and 4 is only the even harmonics of the LO signal mixed with the RF input signal. The odd harmonic mixed signals are canceled. Therefore, the mixer 105 operates as an odd and even harmonic mixer with the odd and even ports isolated from each other. Routing circuit 102 and image enhanced double balanced YIG
The parameter values of the elements of the tuning mixer 105 are routing YIG
It depends on the frequency range in which the tuned resonator filter and mixer circuit 100 is intended to operate. 0 to 26.5 GHz
For one embodiment of a routing YIG tuned resonator filter and mixer circuit 100 intended to operate at, the parameter values for the elements are:

Capacitor: C ₁ = 27pF C ₂ = 150pF C ₃ = 1500pF C ₄ = 6pF C ₅ = 4pF C ₆ = 4pF C ₇ = 5pF C ₈ = 4pF

Inductor: L (L ₁ , L ₂ , L ₃ , and L ₄ ) = 40nH L ₅ = 8nH L ₆ = 8nH Resistor: R ₁ = 10Ω R ₂ = 10Ω R ₃ = 350Ω

Such a configuration of the routing YIG tuned resonator filter and mixer circuit 100 has improved sensitivity,
The spectrum analyzer is typically <-144 dBm / Hz, and the frequency response is improved, typically <± 2.2 dB. Preselector 10 to select the correct mixed signal
Tune 4 to the frequency of the RF input signal of interest and
This is done by selecting the signal frequency and switching the IF switch 108 to the correct odd or even IF port 106 or 107. An example of basic mixing is as follows. f _RF = 4GHz (tunes preselector 104 to 4GHz) f _LO = 4.3GHz

Node 1 and Node 2: Odd harmonic mixed signal f _IF = (2n + 1) f _LO ± f _RF only (No even harmonic mixed signal exists at Nodes 1 and 2.) When n = 0, 4.3 ± 4 GHz 8.3 GHz (shorted by capacitor C ₆ ) 0.3 GHz (flows through IF balanced-unbalanced transformer 304), if n = 1, 12 ± 4.3 GHz 16.3 GHz (recycled by capacitor C ₆ ) 7.7 GHz (Recycled by capacitor C ₆ )

There are no odd harmonic mixing signals at nodes 3 and 4. Node 3 and node 4: Even harmonic mixed signal f _IF = 2nf
_LO ± f _RF only (the odd harmonic mixing the node 3 and node 4 are not present.) For n = 1, 8.3 ± 4GHz 12.3GHz ( recirculated by capacitor C ₄₎ 4.3 GHz (the capacitor C ₄ The results are the same for n = 2, 3, 4, ..., M.
Therefore, the IF switch 108 is connected to the odd IF port 106.

An example of the second harmonic mixing is as follows. f _RF = 8.3 GHz (tunes preselector 104 to 8.3 GHz) f _LO = 4 GHz 2nd harmonic mixing node 1 and node 2: odd harmonic mixing signal f _IF = (2n
+1) f _LO ± f _RF only (no even harmonic mixing signals on nodes 1 and 2) for n = 0, 4 ± 8.3GHz 12.3GHz (recirculated by capacitor C ₆ ) 4.3GHz ( when the capacitor C ₆ of recycled is) n = 1, 12 ± 8.3GHz 20.3GHz ( recirculated by capacitor C ₆₎ 3.7 GHz (recirculated by capacitor C ₆₎

Node 3 and node 4: Even harmonic mixed signal f _IF = 2nf _LO ± f _RF only (no odd harmonic mixed signal exists at node 3 and node 4) When n = 1, | 8 ± 8.3 ｜ GHz 0.3GHz (flows to even IF balanced / unbalanced transformer 302) 16.3GHz (recycled by capacitor C ₄ ) When n = 2, ｜ 16 ± 8.3 ｜ GHz 24.3GHz (recycled by capacitor C ₄₎ 7.7 GHz (recycled by capacitor C ₄ ), the IF switch 108 is therefore connected to the IF port 107.

The conversion loss measurements of the above-described embodiment of the routing YIG tuned resonator filter and mixer circuit are 12 dB for fundamental mixing, 14 dB for second harmonic mixing, and 4 dB.
It was 16 dB for harmonic mixing. This conversion loss is due to the routing circuit 102, the preselector 104, the mixer 105 including the IF unbalance transformers 302 and 304, and the IF switch 108.
Equivalent to the loss of. With routing circuit 102, preselector 104, IF unbalance transformers 302 and 304, and IF switch 108 removed, the result is about 4 dB for fundamental mixing, 6 dB for second harmonic mixing, and It corresponds to a mixer with a conversion loss of 8 dB for the 4th harmonic mixing. This is a significant improvement over existing biased harmonic mixers, which typically have conversion losses of 8, 12, and 22 dB for fundamental, second, and fourth harmonic mixing, respectively. Other improvements in insertion loss and flatness are also apparent from integrated mixer 105 with preselector 104. Third-order intercept (TOI) is generally greater than ± 20 dBm.

When the routing YIG tuned resonator filter and mixer circuit 100 is incorporated into a high performance portable microwave spectrum analyzer, the sensitivity is improved by 16 dB with 4th harmonic mixing compared to the previous harmonic mixing front end. . By comparison, this performance level can only be exceeded at high frequencies by a fundamental mixing spectrum analyzer, such as the HP 71210C modular spectrum analyzer available from Hewlett-Packard Company, Palo Alto, CA.

4, FIG. 7, FIG. 8 and FIG. 9 show an image enhanced double balanced YIG tuned mixer that produces a switched IF output signal based on odd or even harmonic mixing.
Reference numeral 0 is a schematic diagram of an image enhancement double-balanced YIG tuning mixer 305 that mixes the fundamental or odd harmonics of the LO signal with the RF input signal to produce a predetermined low frequency IF signal output. As shown in FIG. 10, the mixer 305 comprises a second half loop of the coupling loop 138 and a full output coupling loop 142.
42 is continuous at the first end and is connected to the LO input 194.
Output coupling loop 142 includes diodes D ₃ , D ₄ , D ₅ , and D
It terminates at the second end with a monolithic GaAs diode integrated circuit consisting of a diode bridge consisting of _six . Diodes D ₃ , D ₄ , D ₅ , and D ₆ are preferably Schottky diodes. The mixer 305 is also provided with a diode bridge _{D 3, D 4, D 5} , and D ₆ capacitor C ₉ connected across. Mixer 305 further input is provided with a diode bridge _{D 3, D 4, D 5} , and D ₆ are connected across a single IF balun 306. I
The F balance / unbalance transformer 306 operates as a fundamental wave and odd harmonic IF balance / unbalance transformer. IF balanced-unbalanced transformer 306
The output of is connected to the odd IF port 106. Finally,
The mixer 305 has a diode bridge D ₃ , D ₄ , D on one side.
₅ and D ₆ and a capacitor C ₁₀ connected between the respective junctions of the IF balance-unbalance transformer 306 and the ground on the other side. Even IF port associated with mixer 305
107 does not exist. As a result, the IF switch 108 is unnecessary.

The capacitor C ₉ is a diode bridge D ₃ ,
Connected across D ₄ , D ₅ , and D ₆ . The connection inductance of the capacitor C ₁₀ is node 1 and node 2
May cause high impedance across
The impedance between node 1 and node 2 is very low for high frequency odd harmonic mixed signals (eg ≧ 2 GHz). The inductance of the full output coupling loop 142 is small enough (ie, ≤0.4nH) so that the current produced by the even harmonic mixing signal is retroreflected to the mixer 305 without substantial phase change.

Considering in more detail, the image enhancement double balance
In the case of YIG tuned mixer 305, for example, a swept LO signal from 3 to 6.8 GHz or a wideband LO signal from 3 to 26.5 GHz will have diode bridges D ₃ , D ₄ , D ₅ , and D _{6 connected} to node 1
Can be driven through. The LO current return path is through capacitor C ₁₀ . The RF input signal from the second half loop of the coupling loop 138 couples through the YIG sphere 140, producing a circulating RF current through the full output coupling loop 142. The RF input signal is the LO signal diode bridge D ₃ , D ₄ , D ₅ , and D ₆
, And generates an odd harmonic signal of frequency (2n + 1) f _LO ± f _RF . Node 1, node 2, and node 3 are virtual ground ports for RF input signals. Therefore, LO input 19
The 4 and odd IF ports 106 are isolated from the RF input consisting of the second half loop of the coupling loop 138 and the LO input 194 is isolated from the RF input and the odd IF ports. The IF signal is isolated from node 1. Frequency (2n + 1) f _LO ± f _RF IF
The signal flows through node 2 and node 3, while node 1 is a virtual ground port for these mixed signals.
Also, at nodes 1, 2, and 3, the even harmonic mixing signals of frequency 2nf _LO ± f _IF cancel. Therefore, the only nodes through which the odd IF signals flow are node 2 and node 3, which are loaded by capacitor C ₁₀ . Odd IF
The mixed signal flowing through the port 106 has a frequency f _IF = (2n + 1) f _LO
-F is only the low frequency portion of the _RF of the IF signal, which is, for example, about 300 MHz. All other mixed signals, especially those of frequency (2n + 1) f _LO + f _RF , are filtered back and remixed to improve the mixed signal at the IF signal frequency (2n + 1) f _LO −f _RF .

The image enhancement double balanced YIG tuned mixer 305 only mixes the fundamental and odd harmonics. Advantageously, the odd harmonic mixing signals are separated at node 1 (ie virtual grounded). In the image enhancement double balanced YIG tuned mixer 305, all higher order mixed signals are shorted through an external capacitor or through a circuit configuration (virtual ground port). Therefore, the image and the multiple are improved, and the efficiency is further improved. Also, the RF and IF signals are perfectly balanced. Since the IF signal is balanced, no return path through the perfect output coupling loop 42 or LO input 194 is required.

The signal paths for the LO, RF, and odd IF currents can be discussed in detail in connection with the schematic diagram of the image enhancement double balanced YIG tuned mixer 305 shown in FIG. LO signal is LO
A full output coupling loop 142 is applied through input 194.
The LO signal is split equally between the upper and lower halves of the output coupling loop 142 to prevent the diode during the positive half cycle of the LO signal.
It flows through D ₃ and D ₅ and through diodes D ₄ and D ₆ during the negative half cycle of the LO signal, biasing each diode pair into its conducting state. These diodes are in series with output coupling loop 142 and capacitor C ₁₀ . The LO signal is output by the output coupling loop 142 to the coupling loop 138.
Is orthogonal to and is therefore isolated from the RF port consisting of the second half loop of coupling loop 138. LO current flows in common mode (ie, in the same direction) through the upper and lower halves of output coupling loop 142 and YIG sphere 140 is tuned to the frequency of the RF input signal.

Each diode D ₃ , D ₄ , D ₅ , and D ₆ is
It can be expressed as a time-varying conductance, as shown in 11B. Conductance g (t) represents the time-dependent conductance of diodes D ₃ and D ₅ are driven by the positive half cycle of the LO signal. Similarly, diodes D ₄ and D ₆ are driven on the negative half cycle of the LO signal and are represented by g (t + T / 2). However, T is the period of the LO signal. The RF input signal from the third stage of the filter is applied to the second half loop of coupling loop 138. This induces a balanced circulating RF current in the full output coupling loop 142. Node 1, node 2, and node 3 are virtual ground ports for RF input signals.
Therefore, the RF input signal is isolated from both the LO input 194 and the odd IF port 106. As shown in FIG. 11C, the current through diodes D ₃ , D ₄ , D ₅ , and D ₆ is given by the equation: i ₁ (t) = V _RF · g (t) i ₂ (t) = V _RF · g (t + T / 2) i ₃ (t) = − V _RF · g (t) i ₄ (t) = − V _RF・ g (t ＋ T / 2)

By performing the Fourier transform of the above equation, the current at frequencies of all combinations of LO signal, RF input signal, and mixed signal can be analyzed. In the following equation, the asterisk ( ^* ) represents the synergistic function. i ₁ (f) = V _RF (f) ^* G (f) i ₂ (f) = V _RF (f) ^* G (f) exp [(j2πfT / 2)] i ₃ (f) = -V _RF ( f) ^* G (f) i ₄ (f) = −V _RF (f) ^* G (f) exp [(j2πfT / 2)] Current i ₁ (f), i ₂ (f), i ₃ (f) , And i ₄ (f) represent all possible mixed signals between the LO signal and the RF input signal in the frequency domain.

The currents I ₁ (f), I ₂ (f), I ₃ (f), and I ₄ (f) shown below flow out of the diode bridges D ₃ , D ₄ , D ₅ , and D _6. Current flowing into nodes 4 and 5 and into the upper and lower halves of full output coupling loop 142. I ₁ (f) = i ₁ (f) −i ₂ (f) = V _RF (f) ^* G (f) [1−exp (jπfT)] I ₂ (f) = i ₄ (f) −i ₃ (f) = V _RF (f) ^* G (f) [1−exp (jπfT)] I ₃ (f) = i ₁ (f) −i ₄ (f) = V _RF (f) ^* G (f) [1 + exp (jπfT)] I ₄ (f) = i ₂ (f) −i ₃ (f) = V _RF (f) ^* G (f) [1 + exp (jπfT)] LO is a pure sine wave spectrum In the case of an analyzer, these equations can be transformed into the following equations.

[0061]

[Equation 3]

In equations 5 and 6, since f _LO = 1 / T, equation [1-exp (jnπf _LO T)] is transformed into equation [1-exp (jnπ)], and the real part of this equation Is equal to 0 when n corresponds to an even number. Also, the formula [1 + exp (jnπf _LO T)] is the formula [1 + exp
(jnπ)] and its real part is equal to 0 when n corresponds to an odd number. Equations 5 and 6 can be transformed into the following equations:

[0063]

[Equation 4]

The real part of the current flowing into nodes 2 and 3 from equation 7 is only the odd harmonics of the LO signal that mix with the RF input signal, and at nodes 4 and 5 the odd harmonics of the LO signal that mix with the RF input signal. It is clear that the waves will cancel out. This means that nodes 1, 4, and 5 are virtual grounds for the odd harmonic mixed signal, and the odd harmonic mixed signal does not require a return path through node 1. Therefore, the odd harmonic mixed signal can be extracted from nodes 2 and 3 through the odd IF balanced / unbalanced transformer 306. Similarly, it is clear from Equation 8 that the real part of the current flowing into nodes 4 and 5 is only the even harmonics of the LO signal mixed with the RF input signal. The odd harmonic mixed signals are canceled. Thus, mixer 305 is a double balanced mixer that operates as a fundamental and odd harmonic mixer.

Capacitors C ₉ and C ₁₀ are incorporated at nodes 2 and 3 to enhance the image and multiple mixed signals. As a result, high frequency odd mixed signals (ie ≧ 2GH
z) is retroreflected by the mixer 305 and remixed. Also, node 1 shorts to the even harmonic mixing currents I ₃ (f) and I ₄ (f) and retroreflects them into mixer 305 for remixing.
The result is a very efficient mixer. The mixed signal that can flow to the odd IF port 106 is
Only the F signal (ie f _IF 1 GHz).

FIG. 12 shows another image enhancing double balanced YIG tuned mixer 405 that mixes the fundamental or odd harmonics of the LO signal with the RF input signal to produce a predetermined low frequency IF signal output. In contrast to mixer 305 shown in FIG. 10, the LO signal is injected at a different location in mixer 405 shown in FIG. In the image enhancement double balanced YIG tuned mixer 405 shown in FIG. 12, the first end of the full output coupling loop 142 is grounded. The mixer 405 additionally comprises a capacitor C ₁₁ connected in series across the capacitor C ₉ . The junction between capacitors C ₁₁ is connected to LO output 194. The mixer 405 also comprises inductors L ₇ and L ₈ whose first end is connected to the respective junction of the capacitor C ₉ on the one hand and to the capacitor C ₇ on the other hand. The second ends of the inductors L ₇ and L ₈ are, on the one hand, at the respective junctions of the capacitor C ₁₀ .
On the other hand, it is connected to the IF balance-unbalance transformer 306.

The signal paths for the LO, RF, and odd IF currents can be discussed in more detail in connection with the schematic diagram of the image enhancement double balanced YIG tuned mixer 405 shown in FIG. 13A. The LO signal is applied through the junction of capacitor C ₁₁ . The combination of inductors L ₇ and L ₈ and capacitor C ₁₀ provides a high impedance load for the LO signal at nodes 2 and 3. Therefore, the LO signal flows through diodes D ₄ and D ₆ during the positive half cycle of the LO signal and through diodes D ₃ and D ₅ during the negative half cycle of the LO signal, causing each diode pair to its conductive state. Bias to. These diodes are in series with output coupling loop 142 which is grounded through node 1. The LO signal is isolated from the RF port, which is composed of the second half loop of coupling loop 138, as output coupling loop 142 is orthogonal to coupling loop 138. The LO current is in common mode through the upper and lower halves of output coupling loop 142 (ie,
Flowing in the same direction), the YIG sphere 140 is tuned to the frequency of the RF input signal. Each diode D ₃ , D ₄ , D ₅ , and D ₆ is
It can be expressed as a time-varying conductance, as shown in B. Conductance g (t) represents the time-dependent conductance of diode D ₄ and D ₆ is driven by the positive half cycle of the LO signal. Similarly, diodes D ₃ and D ₅
Is driven by the negative half cycle of the LO signal, g (t + T / 2)
Represented by However, T is the period of the LO signal.

The RF input signal from the third stage of the filter is applied to the second half loop of coupling loop 138. This induces a balanced circulating RF current in the full output coupling loop 142. Node 1, node 2, and node 3 are virtual ground ports for RF input signals. Therefore, the RF input signal is LO
Isolated from both input 194 and IF port 106.
As shown in Figure 13B, diodes D ₃ , D ₄ , D ₅ , and D ₆
The current through is given by the following equation. i ₁ (t) = V _RF · g (t + T / 2) i ₂ (t) = V _RF · g (t) i ₃ (t) = − V _RF · g (t + T / 2) i ₄ (t) = −V _RF・ g (t)

By performing the Fourier transform of the above equation, it is possible to analyze the current for all frequency combinations of the LO signal, the RF input signal, and the mixed signal. The asterisk ( ^* ) in the following equation represents the synergistic function. i ₁ (f) = V _RF (f) ^* G (f) exp [(j2πfT / 2)] i ₂ (f) = V _RF (f) ^* G (f) i ₃ (f) = -V _RF ( f) ^* G (f) exp [(j2πfT / 2)] i ₄ (f) = −V _RF (f) ^* G (f) Current i ₁ (f), i ₂ (f), i ₃ (f) , And i ₄ (f) represent all possible mixed signals between the LO signal and the RF input signal in the frequency domain.

The currents I ₁ (f), I ₂ (f), I ₃ (f), and I ₄ (f) shown below flow out of the diode bridges D ₃ , D ₄ , D ₅ , and D ₆ , Current flowing into nodes 4 and 5 and into the upper and lower halves of full output coupling loop 142. I ₁ (f) = i ₁ (f) −i ₂ (f) = V _RF (f) ^* G (f) [exp (jπfT) −1] I ₂ (f) = i ₄ (f) −i ₃ (f) = V _RF (f) ^* G (f) [exp (jπfT) −1] I ₃ (f) = i ₁ (f) −i ₄ (f) = V _RF (f) ^* G (f) [1 + exp (jπfT)] I ₄ (f) = i ₂ (f) −i ₃ (f) = V _RF (f) ^* G (f) [1 + exp (jπfT)] LO is a pure sine wave spectrum In the case of an analyzer, these equations can be transformed into the following equations.

[0071]

[Equation 5]

In equations 9 and 10, since f _LO = 1 / T, the expression [exp (jnπf _LO T) −1] can be transformed into the expression [exp (jnπ) −1], and its real number The part is equal to 0 when n corresponds to an even number. Also, the formula [1 + exp (jnπf _LO T)] is the formula [1
+ Exp (jnπ)], the real part of which is equal to 0 when n corresponds to an odd number. Equations 5 and 6 can be transformed into the following equations:

[0073]

[Equation 6]

The real part of the current flowing into nodes 2 and 3 from equation 11 is only the odd harmonics of the LO signal that mix with the RF input signal, and at nodes 4 and 5 the odd harmonics of the LO signal that mix with the RF input signal. The waves are clearly offset. This means that nodes 1, 4, and 5 are virtual grounds for the odd harmonic mixed signal, and the odd harmonic mixed signal does not require a return path through node 1. Therefore, the odd harmonic mixed signal can be extracted from nodes 2 and 3 through the odd IF balanced / unbalanced transformer 306. Similarly, it is clear from Equation 12 that the real part of the current flowing into nodes 4 and 5 is only the even harmonics of the LO signal mixed with the RF input signal. The odd harmonic mixed signals are canceled. Thus, mixer 305 is a double balanced mixer that operates as a fundamental and odd harmonic mixer.

To enhance the image and multiple mixing signals, incorporate capacitor C ₉ at nodes 2 and 3. As a result, the high frequency odd mixed signal (ie ≧ 2 GHz) is retroreflected by mixer 305 and remixed. Also, node 1 is shorted to the even harmonic mixed currents I ₃ (f) and I ₄ (f),
They are reflected back to the mixer 305 and remixed. This results in a very efficient mixer. Odd IF port 106
The only mixed signal that can flow into is the predetermined low frequency IF signal (ie f _IF 1 GHz).

4, FIG. 7, FIG. 8 and FIG. 9 show an image enhanced double balanced YIG tuned mixer that produces a switched IF output signal based on odd or even harmonic mixing.
4 is an image enhancement double balance that mixes the even harmonic generation signal of the LO signal with the RF input signal to produce the desired low frequency IF signal output
FIG. 6 is a schematic diagram of a YIG tuning mixer 505. As shown in Figure 14,
The mixer 505 comprises a second half loop of the coupling loop 138 and a full output coupling loop 142, the first end of the output coupling loop 142 ending with a capacitor C ₁₁ and the second end with diodes D ₃ , D _4. , D ₅ , and D _{6 end} up with a monolithic GaAs diode integrated circuit consisting of a diode bridge. Diodes D ₃ , D ₄ , D ₅ , and D ₆ are preferably Schottky diodes. LO input 194 is connected across diode bridges D ₃ , D ₄ , D ₅ , and D ₆ . Mixer 505 further comprises a single IF balance-unbalance transformer 302 whose input is connected across capacitor C ₁₁ . The IF balance-unbalance transformer 302 operates as an even harmonic IF balance-unbalance transformer. The output of the IF balance-unbalance transformer 302 is connected to the even IF port 107. Finally, the mixer 5
05 comprises, on the one hand, the respective junctions of the capacitor C ₁₁ and the IF balun, and, on the other hand, the capacitor C ₁₂ connected between it and the ground. There is no odd IF port 106 associated with mixer 505. Therefore, the IF switch 108 is unnecessary.

The LO signal is sent through node 1 and node 2 to the image enhancement double balanced YIG tuned mixer 505. The return path for the LO current is through capacitor C ₁₂ . The RF current passes through full output coupling loop 142 and capacitor C ₁₁ and mixes with the LO signal at diode bridges D ₃ , D ₄ , D ₅ , and D ₆ . Nodes 1 and 2 are virtual ground ports for RF input signals. Therefore the return path of the RF current is the diode D ₃ ,
It is a closed loop through D ₄ , D ₅ , and D ₆ . The odd harmonic mixed signal only flows out of node 1 and into node 2. Therefore, LO input 194 is a virtual ground port for odd IF mixed signals. Therefore, IF signal and LO
The signal is isolated. At the same time, since nodes 1 and 2 are tied together, all odd harmonic mixing signals are retroreflected into diode bridges D ₃ , D ₄ , D ₅ , and D ₆ ,
Remixed for even better efficiency. Diodes D ₃ and D ₆ are anti-parallel to the LO and RF signals, thus producing an even IF mixed signal of frequency 2nf _LO ± f _RF that flows into node 3 in the direction of RF current flow. Also, the diodes D ₄ and D ₅ are anti-parallel to the RF and LO signals and therefore the frequency 2nf _LO flowing out at node 4 is
Produces an even harmonic mixed signal of ± f _RF . At the same time, nodes 1 and 2 are virtual ground ports for even harmonic mixed signals.

The even harmonic mixing signal circulating through the full output coupling loop 142 has a predetermined low frequency IF, say about 30.
At 0MHz IF, it appears across capacitor C ₁₁ which appears as high impedance. Thus, a given low frequency IF exits node 4, enters node 3 through the IF unbalance transformer 302, enters the upper half of the full output coupling loop 142 and enters node 5. The high frequency even mixed signal circulates through output coupling loop 142 and capacitor C ₁₁ .
The output coupling loop 142 has a very short length, for example 26.
Since .ltoreq..lambda. / 16 at 5 GHz, all high frequency even mixed signals are effectively shorted across nodes 3 and 4, producing an image enhancement effect and further efficiency. Therefore, the mixer
505 is a double-balanced mixer in which the even harmonic mixing signal is isolated from nodes 1 and 2 connected to the LO input 194 to provide image and multiple enhanced mixing for greater efficiency.

The signal paths for the LO, RF, and odd IF currents can be discussed in more detail in connection with the schematic diagram of the image enhancement double balanced YIG tuning mixer 505 shown in FIG. The LO signal goes through the LO input 194 to the diode bridge D ₃ , D ₄ , D ₅ ,
And added to D ₆ . The LO signal flows through diodes D ₄ and D ₆ during the positive half-cycle of the LO signal and through diodes D ₃ and D ₅ during the negative half-cycle of the LO signal, turning each diode pair into its conducting state. Bias to.
The diodes are in series with output coupling loop 142 and capacitor C ₁₁ . LO signal is output coupling loop 1
Since 42 is orthogonal to bond loop 138, bond loop 138
Isolated from the RF port consisting of the second half-loop of LO current flows in common mode (ie, in the same direction) through the upper and lower halves of output coupling loop 142,
The YIG sphere 140 is tuned to the frequency of the RF input signal. Each diode D ₃ , D ₄ , D ₅ , and D ₆ can be represented by a time varying conductance, as shown in FIG. 15B. Conductance g (t) represents the time-dependent conductance of diode D ₄ and D ₆ is driven by the positive half cycle of the LO signal. Similarly, diodes D ₃ and D ₅ are driven by the negative half cycle of the LO signal and are represented by g (t + T / 2). However, T is the period of the LO signal.

The RF input signal from the third stage of the filter is applied to the second half loop of coupling loop 138. This induces a balanced circulating current in the full output coupling loop 142.
Node 1, node 2, node 3, and node 4 are virtual ground ports for RF input signals. Therefore, the RF input signal is isolated from the LO input 194 and the even IF port 107. As shown in FIG. 15B, the current through diodes D ₃ , D ₄ , D ₅ , and D ₆ is given by the equation: i ₁ (t) = V _RF · g (t + T / 2) i ₂ (t) = V _RF · g (t) i ₃ (t) = − V _RF · g (t + T / 2) i ₄ (t) = −V _RF・ g (t)

By performing the Fourier transform of the above equation, the current at frequencies of all combinations of LO signal, RF input signal, and mixed signal can be analyzed. The asterisk ( ^* ) in the following equation represents the synergistic function. i ₁ (f) = V _RF (f) ^* G (f) exp [(j2πfT / 2)] i ₂ (f) = V _RF (f) ^* G (f) i ₃ (f) = -V _RF ( f) ^* G (f) exp [(j2πfT / 2)] i ₄ (f) = −V _RF (f) ^* G (f) Current i ₁ (f), i ₂ (f), i ₃ (f) , And i ₄ (f) represent all possible mixed signals between the LO signal and the RF input signal in the frequency domain.

The currents I ₁ (f), I ₂ (f), I ₃ (f) and I ₄ (f) shown below flow out of the diode bridges D ₃ , D ₄ , D ₅ and D ₆ , The current flowing into node 1 and node 2 and into the upper and lower halves of full output coupling loop 142. I ₁ (f) = i ₁ (f) −i ₂ (f) = V _RF (f) ^* G (f) [exp (jπfT) −1] I ₂ (f) = i ₄ (f) −i ₃ (f) = V _RF (f) ^* G (f) [exp (jπfT) −1] I ₃ (f) = i ₁ (f) −i ₄ (f) = V _RF (f) ^* G (f) [1 + exp (jπfT)] I ₄ (f) = i ₂ (f) −i ₃ (f) = V _RF (f) ^* G (f) [1 + exp (jπfT)] LO spectrum analyzer with pure sine wave In case of, these equations can be transformed into the following equations.

[0083]

[Equation 7]

In equations 13 and 14, since f _LO = 1 / T, the expression [exp (jnπf _LO T) −1] is transformed into the expression [exp (jnπ) −1], and its real part is n. Is equal to 0 when corresponds to an even number. Also, the formula [1 + exp (jnπf _LO T)] is the formula [1 ＋ exp (jnπ)]
And its real part is 0 when n corresponds to an odd number.
be equivalent to. Equations 5 and 6 can be transformed into the following equations:

[0085]

[Equation 8]

From equation 15 the only real part of the current flowing into nodes 1 and 2 is the odd harmonics of the LO signal that mix with the RF input signal, and at nodes 3 and 4 the odd harmonics of the LO signal that mix with the RF input signal. The waves are clearly offset. This means that nodes 3 and 4 are virtual grounds for odd harmonic mixed signals. Similarly, it is clear from Equation 16 that the real part of the current flowing into nodes 3 and 4 is only the even harmonics of the LO signal mixed with the RF input signal. At nodes 1 and 2, the even harmonics of the LO signal that mix with the RF input signal are cancelled. This means that nodes 1 and 2 are ground ports for even harmonic mixing signals, and even harmonic mixing signals do not require a return path through nodes 1 and 2. Therefore, even harmonic mixed signals
It can be extracted from nodes 3 and 4 by the balance-unbalance transformer 302.

To achieve image enhancement and multiple mixed signal enhancement, capacitor C ₁₁ is incorporated between nodes 3 and 4. As a result, high frequency even mixed signals (ie ≧ 2GH
z) is reflected back to the mixer 505 and remixed. Also, node 1 and node 2 are connected together, causing a short circuit for the odd harmonic mixing currents I ₁ (f) and I ₂ (f), retroreflecting them to mixer 505 for remixing. As a result, the efficiency of the mixer is further improved. The mixed signal that can flow to the even IF port 107 is a given low frequency IF signal (ie, f _IF
1 GHz) only.

[0088]

As described above, the sensitivity of the spectrum analyzer can be improved by using the present invention. Further, the speed and reliability of mechanical switching can be improved as compared with the case of using a conventional mechanical microwave relay switch.

[Brief description of drawings]

FIG. 1 is a block diagram of a conventional spectrum analyzer.

1A is a schematic diagram of a conventional mixer circuit used in the apparatus of FIG.

1B is a schematic diagram of another conventional mixer circuit used in the apparatus of FIG.

FIG. 2 is a diagram showing a relationship between RF, LO, and IF signals in the device of FIG.

FIG. 3 illustrates an embodiment of a routing YIG tuned resonator filter and image enhancement double balanced mixer circuit according to the present invention.

FIG. 4 is a perspective view of the circuit shown in FIG.

5 is a simplified elevational view of the circuit shown in FIG.

FIG. 6 is a schematic diagram showing an embodiment of a routing circuit that is preferably incorporated in the circuit shown in FIG.

7 is a schematic diagram illustrating one embodiment of an image enhancement double balanced YIG tuned mixer incorporated into the circuit shown in FIG.

FIG. 8 is a detailed perspective view of an image enhancement double balanced YIG tuned mixer incorporated into the circuit shown in FIG.

9A is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 7. FIG.

9B is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 7. FIG.

9C is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 7. FIG.

FIG. 10 is a schematic diagram showing an embodiment of an image enhancement double balanced YIG tuned mixer.

11A is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 10. FIG.

11B is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 10. FIG.

11C is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 10. FIG.

FIG. 12 is a schematic diagram showing another embodiment of an image enhancement double balanced YIG tuned mixer.

13A is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 12. FIG.

13B is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 12. FIG.

FIG. 13C is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 12.

FIG. 14 is a schematic diagram illustrating one embodiment of an image enhancement double balanced YIG tuned mixer.

15A is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 14. FIG.

FIG. 15B is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 14.

FIG. 15C is a schematic diagram for explaining the operation of the image enhancement double balanced YIG tuned mixer shown in FIG. 14.

[Explanation of symbols]

 104: YIG tuning preselector 108: IF switch

Claims (1)

[Claims] 1. A routing YIG tuned resonator filter and mixer arrangement in which a low frequency signal is delivered to a low frequency output and a high frequency signal is delivered to a high frequency output, comprising a tunable bandpass filter and an image enhancing double balanced mixer. A first, a second, a third, and a fourth YIG tuning resonator coupled to supply, and an electronic magnet for providing a uniform DC magnetic field across these resonators for tuning the resonance frequencies of said four resonators. , And the first YIG resonator has two PINs.
Acting as a first stage of a filter in combination with a routing circuit having a diode, it sends an input signal to the low frequency output or a subsequent stage of the filter and mixer, the second, third and fourth YIG resonators respectively A device that operates as the second, third, and fourth stages of the filter.