High frequency heterodyne mixer

Abstract

Apparatus and methods for detecting a system with a heterodyne mixer having a local oscillator (LO) input, a radio frequency (RF) input, an intermediate frequency (IF) output, and a suspended waveguide structure having a quartz substrate and a patterned metal transmission line with a plurality of suppression slots.

Description

Technical Field

[0001] This disclosure relates to high-frequency electronic equipment and detection systems, and more particularly to heterodyne mixers and methods of manufacturing them. Background Technology

[0002] A mixer is an electronic device that can generate an output signal with a frequency different from that of a received signal. For example, when two input signals are applied to a mixer, the mixer can generate an output signal with frequencies equal to the sum and difference of the input signals or their harmonics. In this way, a mixer can be used to down-convert a detected signal to a lower frequency, for example, to simplify subsequent processing.

[0003] WO 2007 / 125326 illustrates a mixer that receives an incoming radio frequency (RF) signal, receives a local oscillator (LO) signal, and generates an intermediate frequency (IF) signal from a diode chip. This design uses separate RF, LO, and IF circuit paths, along with a wire-based stub tuner, to optimize conversion efficiency and perform power matching.

[0004] However, there is still a need for a mixer design that is effective across the entire wide frequency range (e.g., at very high frequencies) and compatible with the fabrication and assembly techniques used for small components, such as those required when circuit elements are scaled down as the signal wavelength of a given system decreases. Summary of the Invention

[0005] According to an embodiment, a mixer device, such as a heterodyne mixer, is disclosed. The mixer may include: a first input, such as a local oscillator (LO) input; a second input, such as a radio frequency (RF) input; an output, such as an intermediate frequency (IF) signal output; a suspended signal transmission element including a plurality of suppression slots and filter elements; and a diode circuit mounted on the suspended signal transmission element. The suspended signal transmission element may be, for example, a waveguide. In some aspects, the suspended signal transmission element is a waveguide comprising: a substrate having a first surface and a second surface; and a transmission line located on the first surface, wherein the substrate is a quartz substrate and the transmission line is a patterned metal microstrip line (also called a stripline) transmission line. Further, the first input (e.g., LO) may be located between the second input (RF) and the output (e.g., IF), and the transmission element may be configured to transmit the IF signal generated in the diode circuit from the diode circuit to the output along the longitudinal axis of the transmission element.

[0006] According to one embodiment, a heterodyne mixer device has a waveguide component, wherein the waveguide component includes a filtering component, a transmission component, and a suppression component. One or more semiconductor devices may be mounted on the surface of the waveguide component.

[0007] According to an embodiment, a mixer having one or more slotted filter elements is provided. In some aspects, the slots in the filter are relatively small compared to the free-space wavelength. For example, the slots may be less than λ / 10.

[0008] According to an embodiment, a mixer is provided having an RF signal input at a first end, an IF signal output at a second end, and an LO signal input between the two ends (e.g., in the middle). In some aspects, a waveguide transmission element extends from the first end to the second end. The transmission element may be suspended and may also have multiple suppression slots and filter elements. Further, a diode circuit may be mounted at the first end of the mixer and close to the RF signal input. In some embodiments, the IF signal generated in the diode circuit propagates along the transmission element to the IF signal output at the other end of the mixer. The mixer may be arranged in a detector block having RF and LO input channels along a first axis and an IF output along a second axis perpendicular to the first axis.

[0009] According to some embodiments, a detector, such as a terahertz camera, is provided. The detector may include, for example: one or more mixers described herein; one or more horn-shaped feeders coupled to an input of at least one of the mixers (e.g., providing an RF signal); a local oscillator coupled to another input of at least one of the mixers; a coaxial line (or other transmission element) coupled to the output (e.g., an IF signal) of at least one of the mixers; and one or more of a low-noise amplifier (LNA), a power detector, and an analog-to-digital converter (ADC) circuit element connected to the coaxial line and configured to process the output IF signal. The detector may further include additional filtering and image processing, for example, to generate an image of an object or scene from which it receives input radiation. In some aspects, the one or more mixers include a plurality of mixers optimized at 250 GHz and a plurality of mixers optimized at 375 GHz. The group of mixers may further include a plurality of mixers optimized at 125 GHz.

[0010] According to some embodiments, a method for operating a mixer is provided. The method may include, for example, the steps of: receiving an RF signal at a first input of a mixer device having suspended transmission line elements, multiple suppression elements, and diode circuitry; providing a local oscillator signal to the mixer; and outputting an IF signal generated by the diode circuitry, wherein outputting the IF signal includes propagating the signal along the longitudinal direction of the mixer through multiple filters.

[0011] According to some embodiments, a method for manufacturing a mixer device (such as one or more mixers described herein) is provided. The method may begin with a machining step, comprising: (1) machining a first housing component comprising a first radio frequency channel portion, a first local oscillator portion, a first intermediate frequency channel portion, a first cavity portion, a first mounting bracket portion, and a second mounting bracket portion; and (2) machining a second housing component comprising a second radio frequency channel portion, a second local oscillator portion, a second intermediate frequency channel portion, a second cavity portion, a third mounting bracket portion, and a fourth mounting bracket portion. Signal transmission elements (e.g., waveguides) may be suspended in the first cavity portion and / or the second cavity portion by mounting the waveguide elements on the first and second mounting bracket portions and / or the third and fourth mounting bracket portions. Alternatively, the first housing component may be attached to the second housing component to form a block. For example, the block may be a receiver array block of a detector (such as a terahertz camera).

[0012] According to one embodiment, a detector block is provided, comprising a housing and one or more mixers mounted within the housing. The housing may include: one or more horn-shaped feeders coupled to an RF input of at least one of the mixers; one or more local oscillator channels coupled to an LO input of at least one of the mixers; and one or more output channels coupled to an IF output of at least one of the mixers. One or more of the mixers may include suspended signal transmission elements mounted on a first mounting structure and a second mounting structure of the housing. In some embodiments, the one or more horn-shaped feeders and the one or more local oscillator channels extend along a first axis of the housing, and the one or more output channels extend along a second axis of the housing, and the first axis and the second axis are perpendicular. Additionally, the suspended signal transmission element may include: a substrate having a first surface and a second surface; and a transmission line located on the first surface, wherein the transmission line is a patterned metal microstrip line transmission line including one or more suppression slots and filter elements.

[0013] According to an embodiment, a terahertz camera is provided, comprising: one or more mixers including an IF output, a LO input, and an RF input; one or more horn feeders coupled to the RF input of at least one of the mixers; a local oscillator coupled to the LO input of at least one of the mixers; and one or more of a low-noise amplifier, a power detector, and an analog-to-digital converter connected to the IF output and configured to process the output IF signal from at least one of the mixers. Additionally, at least one of the mixers may further include: a suspended signal transmission element including a plurality of suppression slots and filter elements; and a diode circuit mounted on the suspended signal transmission element and configured to generate the IF output signal based on radiation received on one or more of the horn feeders and a power signal from the local oscillator. In some embodiments, the received radiation is in a frequency band centered at 125 GHz, 250 GHz, or 375 GHz. Attached Figure Description

[0014] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments.

[0015] Figure 1 The illustration shows a mixer device according to some implementation schemes.

[0016] Figure 2A and Figure 2B The illustration shows a mixer device according to some implementation schemes.

[0017] Figure 3A and Figure 3B The illustration shows details of a mixer device according to some implementation schemes.

[0018] Figure 4 It is a flowchart illustrating a process according to some implementation schemes.

[0019] Figure 5 This is a schematic diagram of a detection system based on some implementation schemes.

[0020] Figures 6A to 6C The diagram illustrates a detector block according to the implementation scheme.

[0021] Figure 7 It is a flowchart illustrating a process according to some implementation schemes.

[0022] Figure 8A and Figure 8B The diagram illustrates the microstrip line field and current according to some implementation schemes.

[0023] Figure 9 The illustration shows a detection system, such as a terahertz camera, according to an implementation scheme. Detailed Implementation

[0024] Sensing microwave, millimeter, and / or submillimeter signals from objects or scenes may require extremely sensitive detectors. For example, the power level of the received signal may be in the nanowatt range.

[0025] In one example, such as at certain microwave frequencies, a low-noise amplifier can be used to increase the power level of a signal by several orders of magnitude (e.g., 100 to 1000 times), allowing the signal to be processed to generate a DC voltage. This DC voltage can then be further amplified until it is strong enough to be converted into a digital value, which can then be used to create image data. Other detection schemes can be used, such as a calorimeter, which is an efficient and highly sensitive thermometer used to generate a voltage proportional to the power level of the scene. At relatively low power levels, the calorimeter may need to be cooled to very low temperatures, typically less than 20 Kelvin, which amplifies the weak received signal against the inherent noise of the calorimeter itself (caused by the random movement of electrons due to thermal vibrations of atoms / molecules in the material used for the calorimeter). This cooling requirement may require sophisticated cryogenic techniques, which not only significantly increase cost, size, and weight but may also require a significant power level. Therefore, applications of calorimeter-based imaging may be limited. For example, many safety and materials testing applications require the system to be highly portable, which in turn requires low mass, size and power.

[0026] At higher frequencies (such as millimeter and submillimeter wavelengths), high-gain, low-noise amplifiers may struggle to operate at sufficiently high performance at room temperature for real-time passive imaging. Furthermore, as frequency increases, the path length of amplifier gates also increases, necessitating increasingly smaller devices. This, in turn, leads to higher resistance and increased signal loss and noise, as well as reduced gain. If the operating frequency doubles, the circuit area typically decreases by a factor of four, and the volume by an factor of eight. Therefore, even a modest increase in frequency can present fabrication and assembly challenges, which in turn reduces reproducibility and yield, thereby increasing costs. Such frequency increases may also reduce the practicality of conventional assembly tools for machining high-frequency components.

[0027] By way of example, a quartz filter used to separate the RF, LO, and IF signals can become extremely small and difficult to handle at frequencies exceeding 250 GHz. Furthermore, if bonding wires are required to "tune" the three signals of the heterodyne mixer, these wires and connections are difficult to implement in a conventional manner, and the bonding wires need to be properly sized to optimize all three signals. Additionally, if a filter, such as an IF filter, is formed by high and low quarter-wave impedance sections implemented on the IF output pin, it can complicate assembly, increasing cost and assembly time.

[0028] According to the implementation scheme, some problems with existing systems are addressed by using a mixer to downconvert the detected signal to a lower frequency (e.g., a lower microwave frequency) so that the signal can then be amplified and processed. According to the implementation scheme, the mixer can achieve high downconversion efficiency from the RF signal to the IF signal while using a minimal amount of LO signal power. In some aspects, the disclosed design can minimize the amount of signal reflected at the IF output (i.e., good IF matching exists). In some aspects, good IF matching may mean that the mixer circuitry is at approximately 50 ohms under LO pump conditions (i.e., during operation). In some instances, this may be the same impedance as one or more IF amplifiers.

[0029] According to the implementation scheme, designs at higher frequencies can be routinely manufactured and assembled using circuits that isolate the influence of circuit elements on each other, while simultaneously providing an increased range for circuit optimization and improved performance. By increasing the available space on the filter substrate, the ohmic resistance of the filter metallization can be reduced. This, in turn, reduces the amount of signal lost in smaller circuits if not done in this way.

[0030] In some implementations, broadband lateral waveguides are used at both the LO and RF microstrip junctions to provide a simplified circuit layout and topology. Odd-mode and lateral-mode suppression slots can be used in conjunction with air-suspended microstrip line filter topologies that have low-impedance sections with one or more filter circuits. In some respects, this allows for the use of wide filter channels, thereby relaxing machining tolerances, increasing fabrication yield, and reducing assembly complexity.

[0031] Quartz filter circuits can be implemented using microstrip line circuit configurations. According to one embodiment, the signal propagates in the longitudinal direction in the fundamental transverse electromagnetic mode (TEM-00), where there is no electromagnetic field component even though all power transfer occurs in the longitudinal direction. To propagate the TEM-00 mode, and in some embodiments, the microstrip line configuration consists of two conductors small enough to prevent the propagation of higher-order modes. These conductors may comprise the outer wall of the filter channel and the inner filter metallization. In this geometry, the field can be calculated using finite element analysis for each cross-section and their combinations. As the size of the outer conductor increases relative to the signal wavelength, which is likely desirable for reasons highlighted herein, higher-order TEM-nn modes, such as odd modes (e.g., TEM-01 and TEM-10), can be generated. As the signal propagates downwards along the filter channel, such higher-order odd modes can create blocking resonances between the filter cross-sections, which degrade broadband performance. Wave propagation in the transverse direction can also lead to power transfer losses between mixer circuit elements. Furthermore, using the widest possible cross-section increases the likelihood of odd-order modes and transverse wave propagation. However, for odd-order TEM modes and transverse wave propagation to occur, a lateral surface current is required across the geometry (e.g., the filter conductor geometry). Therefore, unwanted modes and propagation can be suppressed, for example, by incorporating a longitudinal slot in the first filter element.

[0032] According to some implementation schemes, using a wide longitudinal filter with a common center line feed can minimize ohmic losses for all three signals (LO, RF, IF). Additionally, using a capacitively inductively tuned short-circuit pad in conjunction with a physical DC ground can lock all three signal paths to ground in the shortest possible length, thereby increasing the inherent bandwidth of the entire circuit. For example, this eliminates the need for separate tuning connectors / wires for each frequency, further minimizing ohmic losses.

[0033] Now for reference Figure 1 This document provides a cross-sectional view of a mixer 100 according to some embodiments. The mixer 100 may be, for example, a heterodyne mixer, including a superheterodyne mixer, a harmonic mixer, and / or a subharmonic mixer. In some embodiments, a balanced mixer design may be used.

[0034] Mixer 100 may include a first input 102, such as a LO input, a second input 104, such as an RF input, and a signal output 106, such as an output for an IF signal. According to embodiments, the first input 102 may be a portion of mixer 100 configured to couple a signal from a local oscillator via a LO waveguide 114, which delivers the LO signal to mixer 100. In some embodiments, waveguide height reduction and matching elements may be used to impedance match the LO signal to the mixer. Additionally, the second input 104 may be a portion of mixer 100 configured to couple a signal from an radio frequency source via an RF waveguide 116. In some aspects, the RF waveguide 116 delivers the RF signal as part of a detection system, for example, via one or more horn feeds of a high-frequency camera. In some aspects, inputs 102 and 104 may be antennas. Figure 6A An example of a mechanically engineered signal path coupled to the mixer input and output is provided. Although illustrated with a waveguide input and antenna, other transmission elements such as coaxial lines or coplanar lines can be used to deliver one or more of the LO and RF signals to mixer 100. Figure 1 As shown in the example, the mixer is equipped with an RF input at one end, an IF output at the opposite end, and an LO input between the two ends (e.g., in the central part of the mixer).

[0035] Signal output 106 provides an output signal from a mixer circuit such as diode circuit 110. In some embodiments, diode circuit 110 includes two Schottky diodes configured in anti-parallel. However, other circuitry may be used. In some embodiments, the IF signal from diode circuit 110 is output from mixer 100 via a coaxial connection (e.g., connection element 118 in the output channel). Alternatively, the IF signal may be output using one or more of a frequency-dependent waveguide or other wired connection. The IF signal may be transmitted from diode circuit 110 to output 106 along the length of suspended transmission line element 108, as illustrated by directional arrow 134. In this arrangement, LO input 102 is interposed between RF input 104 and IF signal output 106. According to the implementation scheme, RF input 104 is located at the first far end of mixer 100 and waveguide element 108, IF output 106 is located at the second far end of mixer 100 and waveguide element 108, and LO input 102 is located in the central region of mixer 100 and waveguide element 102.

[0036] According to one embodiment, mixer 100 includes a suspended element 108, which is a waveguide and is mounted in a cavity of mixer housing 132 via substrate mounts 120a and 120b. In this manner, an air gap 130 is provided on at least two sides (e.g., top and bottom) of the suspended waveguide element 108. As another example, and as... Figure 2A As illustrated, the suspended waveguide element 108 may have air gaps 130 on all four sides. One or more of the substrate mounts may be flat (such as mount 120a) or stepped (such as mount 120b). The waveguide element 108 may include a substrate portion and a patterned metal surface portion. For example, the substrate may be quartz (or another suitable dielectric, such as aluminum nitride) having a patterned gold layer for forming microstrip line transmission lines. Other suitable transmission line materials may include other metallic materials or materials that are otherwise conductive. A diode circuit 110 may be mounted on the patterned metal surface of the waveguide element 108, for example, at least partially within the RF input 104. In some embodiments, the suspended waveguide element 108 includes a suppression groove configured to suppress unwanted transmission modes and resonant modes. In some embodiments, the housing 132 may include a block or portion of a block, such as a detection array block. For example, blocks 514, 600, 620, and 650 may include... Figure 1 To the shell shown in Figure 3.

[0037] According to the implementation, a signal can propagate along the transmission line on the surface of the suspended waveguide element 108 through one or more filters. For example, the suspended waveguide element 108 may include an LO filter / suppression section 124, an RF filter / suppression section 126, and an RF receiving element (e.g., an antenna) 128, which may be part of the RF input 104. The LO filter / suppression section 124 can filter the LO signal arriving at the IF output 106. In some implementations, this can eliminate the need for separately machined LO and / or IF coaxial filter pins. The RF filter / suppression section 126 can filter the RF signal arriving at the IF output 106 and / or filter spurious signals arriving at the diode circuit 110. Additionally, the RF receiving element 128 may be configured with multiple slots (e.g., suppression slots). In some implementations, the suppression slots used along the surface of the suspended waveguide element 108 extend in the longitudinal direction and suppress odd-mode propagation. For example, the slotting feature within the stripline can suppress current flow across the width of the suspended waveguide element 108, thereby preventing unwanted odd modes from propagating along the stripline toward the IF output 106. According to the embodiment, the desired even mode propagation of the IF signal is unaffected by the suppression slot.

[0038] In some implementations, the slot has a width less than λ / 10 and a length of at least 1 / 4λ.

[0039] According to the implementation scheme, the slotting feature within the microstrip line circuit suppresses current flow across the width of the microstrip line metal and prevents unwanted odd modes from propagating along the microstrip line circuit. However, the desired even mode propagation can be unaffected by the slot.

[0040] like Figure 1 As illustrated, mixer 100 includes one or more mounting structures 120a, 120b for the suspended waveguide element 108. Therefore, and according to certain embodiments, the mixer's filter is suspended at the end of the stripline rather than on the side. Consequently, less dielectric substrate can be present within the cavity, allowing higher modes to move above the mixer's operating frequency. Furthermore, and in some embodiments, the sides of the channel cavity are flat and less likely to disrupt filter characteristics.

[0041] According to embodiments, one or more filters of mixer 100 are coupled to the top and / or bottom of a housing cavity in which the mixer is mounted. For example, a suspended stripline filter can be designed such that filter sections are primarily coupled to the top or bottom of the cavity, rather than the sides of the cavity. This improves the manufacturability of the mixer because the filter characteristics depend more on the dimensions of the filter features than on the dimensions of the machined channels (or the assembly position within the channels). Filter features can be more easily and precisely controlled because they are defined by, for example, photolithography. In some embodiments, the width of the suspended waveguide comprises 90% or more of the width of the cavity of housing 132. In some aspects, the presence of a dielectric below the edge of the metallization can cause the filter sections to be primarily coupled to the sides of the cavity. According to embodiments, the cavity walls are moved further away from the filter elements by suspending the substrate. However, the dielectric attracts field lines to the sidewalls at the edge of the metallization. Therefore, the associated current density is higher at the edge without slots, thereby minimizing ohmic losses that would otherwise result from such a method. For example, filter segment 124 has a wide center strip 204, which has slots spaced apart from the edges of the suspended transmission line 108, such as... Figure 2A As illustrated in the example.

[0042] According to the implementation, suppression of higher-order transverse electromagnetic (TEM) modes that can propagate longitudinally downwards along the microstrip line circuit is provided by using one or more slotted features near the transition section between the microstrip line quartz circuit and the waveguide (e.g., where the diode crosses the gap). According to the implementation, this is achieved by introducing a gap to interrupt the transverse surface current path across the center conductor. However, the longitudinal propagation of the desired fundamental mode is unaffected because there is no transverse current in the fundamental mode. Aspects of this feature in… Figure 8A and Figure 8B The diagram is shown in the figure. In some implementations, without these features, higher-order modes can introduce resonance into the low-impedance section of the filter's passband, which may limit the bandwidth, thereby limiting the filter's operating bandwidth and thus the bandwidth of the entire mixer.

[0043] In some embodiments, mixer 100 further includes ground connections 112a and 112b. This can be, for example, via a wired connection. Mixer 100 may further include a tuning shorting pad 122. In some embodiments, ground connection 112b is formed from pad 122 to housing 132. Additionally, one side of diode circuit 110 may be mounted to pad 122.

[0044] Regarding the tuning short-circuit pad 122, and according to some embodiments, one end of the stripline circuit is capacitively coupled to ground via a rectangular metal pad, across the stripline substrate, and to its metal frame. This capacitive coupling connects the circuit to ground as an effective short circuit at the detected signal (RF) and LO millimeter-wave frequencies. This capacitive coupling can reduce the impact of bonding wire assembly variations on the grounding point used for LO and RF signals. The bonding wire from this pad to the metal step connects the circuit to ground at lower frequencies (low microwaves) and DC. This allows for much shorter line lengths, thus providing a wider bandwidth that can be achieved with minimal bonding length and number.

[0045] According to the implementation plan, the LO and / or IF coaxial filter pins do not need to be machined separately.

[0046] In some aspects, to achieve the widest possible bandwidth, a ground connection with a minimum length is provided for all signals, close to the ground side of diode circuit 110. Such a connection is conventionally achieved using a “virtual” reactive connection, involving the use of a tuned stub of the bonding pad that is a multiple of 1 / 4λ at both the LO and signal frequencies. However, and depending on the implementation, the IF signal also has a short ground length to achieve broadband matching, which may be incompatible with conventional techniques. To achieve ideal grounding at all frequencies (including sufficiently high LO and signal frequencies), in some implementations, a virtual broadband short circuit is achieved at both frequencies by using a combination of the capacitance of the bonding pad and the inductance of the short bonding pad. In this implementation, the frequency of the IF signal is too low to be affected by the capacitance of the bonding pad or the inductance of the bonding pad, and because the physical length is very short compared to the IF wavelength (e.g., less than λ / 10), a broadband physical short circuit is achieved.

[0047] Figure 2A and Figure 2B The upper surface of a suspended waveguide 108 within the housing 132 of the mixer 100 is shown. For example, these figures illustrate a patterned metal layer on a substrate for forming waveguide paths for signals within the mixer. Figure 2B In the diagram, diode circuit 110 is omitted to show the pad structure.

[0048] like Figure 2A As shown, the upper surface of the suspended waveguide 108 may include a microstrip line transmission line 202, which includes a wide center stripline 204. In this example, air gaps 130 in the housing 132 are disposed around the suspended waveguide 108 on four sides to form cavities. The sides of the cavities are shown as, for example, cavity sidewalls 206a to 206d. Figure 2B The top view of the mixer 100 shown further illustrates the coupling of waveguides 114 and 116 and the coaxial connection 118. While the coaxial connection is shown as an example, other output channels can be used. According to embodiments, the input channel may extend along a first direction, while the output extends along a vertical direction, such as in… Figure 6A As shown, waveguides 114 and 116 can be in a first plane, while the output channel (e.g., with coaxial connection 118) is in a second orthogonal plane. In this example, the LO input waveguide 114 bisects the mixer. In some embodiments, Figure 2A and Figure 2B The slotted features illustrated herein may correspond to the LO filter / suppression section 124, the RF filter / suppression section 126, and the RF receiving element (e.g., antenna) 128.

[0049] Figure 3A and Figure 3BFurther details of the surface of the waveguide element 108 according to the embodiment are illustrated.

[0050] Figure 3A The illustration shows an example of an LO filter section 124 and an RF filter section 126 on both sides of the LO waveguide input 114 according to some embodiments. Figure 3A As shown in the example, the patterned transmission lines on the surface of the suspended waveguide 108 include multiple slots that can provide one or more of suppression, filtering, and matching of unwanted modes. For example, a suppression slot can provide both suppression and filtering simultaneously. In some embodiments, a hammerhead filter 302 can be used and extended longitudinally to filter the LO signal arriving at the IF output 106. Similarly, a half-hammerhead structure 304 provides filtering for spurious RF. In some aspects, the hammerhead (or half-hammerhead) structure can be a combination of inductive capacitors that act as an effective virtual short circuit with a spacing of λ / 2, blocking the signal from passing through, thereby providing filtering.

[0051] According to the implementation scheme, the slot suppression feature enables a wide center path through the transmission line, which in turn reduces ohmic losses along the length of the suspended waveguide element as the IF signal is transmitted from diode circuit 110 to IF signal output 106. According to the implementation scheme, the thickness of the metallization layer is at least three times the skin depth.

[0052] Figure 3B The illustration shows an enlarged view of an RF receiving element (e.g., an antenna) 128 according to some embodiments, which may be part of an RF input 104. In this example, the receiving element 128 includes a first set of slots and a second set of slots, wherein a first set 306 is provided to filter spurious RF, and a second set 308 helps suppress unwanted transmission modes by providing current interruption for higher-order signals. According to embodiments, the first slot 306 is wider than the second slot 308. Further, and in some embodiments, both the first set 306 and the second set 308 are narrow enough that the receiving element 128 can provide broadband coupling to the RF input waveguide 116. Figure 3B In the view, diode circuit 110 is not shown, which makes various metallization layers (e.g., pads) such as pad 122 visible.

[0053] According to the implementation, mixer 100 can be optimized for a specific frequency range. For example, the width of the patterned metallic feature on the surface of waveguide element 108 (e.g., filter width) can be set to approximately 0.3λ to 0.4λ, where λ is the free-space wavelength. For example, for operation at 375 GHz, the filter channel width could be approximately 0.3 mm. In some implementations, the mixer is optimized at one of 125 GHz, 250 GHz, and 375 GHz. While a specific frequency / wavelength is provided in this example, the design and fabrication of the disclosed mixer can be optimized across a wide frequency / wavelength band. For example, mixer 100 can be adapted as a mixer in the microwave, millimeter, and submillimeter ranges.

[0054] According to the implementation scheme, the central portion of the LO and RF filter arrangement is designed to be as wide as possible to minimize ohmic losses. In some implementations, the width of the center line is 30% to 50% of the width of the cavity in which the mixer is mounted. In some implementations, the width of the center line is 50% or more of the width of the waveguide substrate. In some implementations, the line width is between 0.1λ and 0.2λ at the operating frequency. For example, for optimization at 375 GHz, the width of the center line traveling from the signal end to the IF output end can be approximately 100 micrometers.

[0055] In some embodiments, the patterned metal microstrip line transmission line includes a central line extending from the diode circuit to the output and through one or more filter elements, the width of which is equal to or greater than 0.1λ and less than or equal to 0.2λ, the width of the suspended waveguide element is approximately 0.2λ, and the thickness of the substrate is 0.04λ. The housing cavity may have a width of approximately 0.35λ (e.g., between 0.3λ and 0.4λ) (e.g., in the lateral direction), and the patterned microstrip line transmission line is arranged in the cavity to couple the transmitted dipole mode to the sidewalls of the housing 132 cavity.

[0056] According to the implementation scheme, mixer 100 can be implemented without separate tuning stubs (e.g., wires) or machined LO filter pins. This can be contrasted, for example, with the WO2007 / 125326 design, which requires one or more stub tuners in the form of additional wires and an orthogonal coaxial filter at the IF output to handle LO signal filtering.

[0057] According to the implementation scheme, and in order to achieve the highest bandwidth in the RF and LO input circuits, open-circuit waveguide probes are used. This can provide an improvement because short-circuit waveguides are inherently narrow-band, which typically leads to poor power coupling across the desired frequency band.

[0058] Now for reference Figure 4 A method 400 for operating a mixer according to some embodiments is provided. The mixer may be, for example, mixer 100 or any other mixer having, regarding Figure 1 , Figure 2A , Figure 2B , Figure 3A , Figure 3B and Figure 6A The features shown.

[0059] Method 400 may begin at step s410, which includes receiving an RF signal at a first input of a mixer device having a suspended waveguide element, multiple suppression elements, and diode circuitry. In step s420, a local oscillator signal is provided to the mixer. In step s430, an intermediate frequency (IF) signal generated by the diode circuitry is output. According to some embodiments, outputting the IF signal includes propagating the signal along the longitudinal direction of the mixer (e.g., mixer 100) through multiple filters. The filters may be, for example, part of the multiple suppression elements. According to some embodiments, the RF signal and the LO signal are received and provided along a first axis relative to the mixer, while the IF is output along a different vertical axis.

[0060] Now for reference Figure 5 A detection system 500 is provided according to some embodiments. In this example, an array of horn feeders 502 provides an RF signal to one or more mixers 504 (such as mixer 100 described above). The RF signal can be mixed with an LO signal 512 from a source 508, such as one or more Gunn oscillator sources. The resulting IF can then be fed to processing circuitry 506 for further processing, including amplification, filtering, analog-to-digital conversion, and image generation, or one or more of these. In some embodiments, the output IF is provided from the mixer to one or more of the processing circuitry 506 via a coaxial line. In some embodiments, the horn feeders 502, mixers 504, and signal paths (e.g., 512) can be housed in a block 514. For example, regarding... Figures 6A to 6C The diagram illustrates a block for use with one or more mixers described herein.

[0061] According to the implementation scheme, the group of mixers 504 includes at least three types of mixers, wherein the first mixer is optimized at a first frequency, the second mixer is optimized at a second frequency, and the third mixer is optimized at a third frequency. In this example, all types of mixers follow the following... Figure 1The design and configuration of mixer 100 are shown in Figure 3. In some embodiments, the frequencies are 125 GHz, 250 GHz, and 375 GHz. In some embodiments, a fourth type of mixer is included, using a design and configuration of mixer 100 optimized at 500 GHz.

[0062] Now for reference Figure 6A The illustration shows two machined halves of a detector block 600 according to some embodiments. In this example, a first machined portion 602 may be combined with a second machined portion 604 to form the detector block. The block may include, for example, the housing 132 and block 514 of a mixer 100. Figure 6A As shown, each of the halves may include one or more horn-shaped feeder portions 606, which can serve as channels for delivering RF signals to the mixer 100. Each of the halves may also include an input signal (e.g., LO) delivery portion 608 and includes a mixer cavity shown in detail 610. Additionally, and in some embodiments, the mixer may couple its output to a signal output 612 (e.g., containing a coaxial or other transmission line), which may be formed in the respective block half such that a coaxial cable can travel through the mixer housing 132. For example, output 612 may carry an IF signal generated by the mixer. According to embodiments, the horn-shaped feeder 606 and LO input 608 may be machined along the same axis (e.g., the x-axis) or in the same plane (e.g., the plane formed by the x-axis and z-axis). Additionally, in some embodiments, the mixer output 612 may be machined in a perpendicular / orthogonal manner (e.g., along the y-axis). In this respect, the output signal from the mixer can be delivered in a direction different from the direction of the received input signal. For example, the signal can be output in a direction perpendicular to the plane of the received signal.

[0063] Now for reference Figure 6B and Figure 6C One or more detector array blocks are illustrated according to some embodiments. These detector array blocks may correspond to, for example, array 502 and block 514. Detector elements (such as block 514 with horn-shaped feeder array 502) may be formed as a single block (e.g., as shown in the figure). Figure 6A and Figure 6B (As shown in the diagram). Furthermore, it can consist of multiple blocks (e.g., having, as shown in the diagram). Figure 6C The two sub-blocks shown are formed to create a combined detection block with multiple rows of horn feeders and multiple columns of horn feeders. Additionally, and according to the embodiment, each sub-block can be composed of, as shown regarding... Figure 6A The two parts shown in the diagram form a structure. Figure 6AThis illustrates attaching half block 602 to another half block 604 to form block 600.

[0064] Now for reference Figure 6B A block 620 is provided according to some embodiments. In one example, one or more of detector array 502 and block 514 may include block 620. Block 620 includes one or more signal inputs 622, one or more secondary inputs 624, and one or more outputs 626. For example, signal input 622 may correspond to Figure 2, Figure 5 , Figure 6A and Figure 9 The diagram illustrates multiple detector horn-shaped feeders. Similarly, the secondary input 624 can be, as shown in Figure 2, Figure 5 , Figure 6A and Figure 9 The described LO signal input. For example, output 626 could be a detected signal output, such as one or more IF signals from mixer 100, as combined with... Figure 9 As described. According to the implementation scheme, the inputs are arranged in a single plane, while the outputs are arranged in a horizontal plane. Figure 6B In the example, inputs 622 and 624 are positioned along the x-axis, while output 626 is positioned along the y-axis. According to the implementation, processing circuitry can be connected to output 626. For example, multiple processing circuitry units can be stacked in the z-axis direction to process the signal output from block 620. Similarly, additional blocks can be stacked in the z-axis direction to extend the detector. A similar arrangement is described. Figure 6C The circuit is shown as having elements 660a to 660n. Such a circuit may include, for example, one or more LNAs, broadband power detectors, and / or ADCs, as described above. Figure 9 As illustrated. In some embodiments, a power detector is used to convert broadband microwave power into a baseband signal via a thermal component (e.g., a radiative thermal meter) or by using an amplitude modulation (AM) detector. Additionally, the processing circuitry may include one or more filters, for example, on either side of an LNA or ADC. According to embodiments, power detectors such as 921a, 921b, and 921c detect power across the entire frequency band and output a voltage related to said power.

[0065] Now for reference Figure 6CFurthermore, according to the implementation, the first block (e.g., block 620) can be combined with the second block (e.g., 650) to form a single detection array block, such as block 514 having array 502. In this example, inputs 652 and 654 of block 650 are arranged in a single plane along the x-axis, and output 656 is arranged to extend along the y-axis in the vertical direction. Given the arrangement of the inputs and outputs, processing circuits 660a to 660n can be stacked in the z-axis direction on the outer surfaces of blocks 620 and 650 without interfering with signal capture from the source by input 652 or preventing delivery of LO to input 654. Although circuits 660a to 660n are shown on the side of block 620 of the array, the stack can also be arranged on the other side of the array (e.g., the side of block 650). In this regard, the first stack of processing circuitry 660a to 660n can be disposed on one side of the array, the second stack of processing circuitry 660a to 660n can be disposed on a second side of the array, the input signal (e.g., RF input) can be disposed on a third side of the array, and in some embodiments, another input signal (e.g., LO) can be disposed on a fourth side of the array. The circuitry 660a to 660n may include, for example, one or more LNAs, AM (envelope) power detectors, and / or ADCs, and in some cases, filters.

[0066] although Figure 6CThe array is depicted as having two connected blocks, but the implementation is not so limited. For example, according to an implementation, the detector array can be formed from blocks that are not directly connected and can have more than two blocks. For example, processing circuits 660a to 660n can be inserted between two sub-blocks of the array (e.g., between block 620 and block 650). In some examples, three sub-blocks can be used, with circuitry inserted between the first and second blocks and between the second and third blocks. In such an arrangement, the circuitry located between the first and second blocks can process signals from one or both of the first and second blocks, while the circuitry located between the second and third blocks can process signals from one or both of the second and third blocks. Alternatively, another circuit stack can be disposed on one or more of the outer sides of the array, for example, to process signals from the first or third block. Although described using three blocks, according to an implementation, this arrangement can be repeated to extend the width of the array beyond three blocks. The detection array can also be extended in the z-direction, for example, by stacking additional blocks 620, 650. According to the implementation, there are no inputs or outputs on the upper and lower surfaces of array blocks 620, 650, and therefore, the array blocks can be stacked with another block without interference. Some implementations include blocks 620, 650 with six primary sides, wherein the inputs and / or outputs are exposed on the outer sides (e.g., the inputs and / or outputs pass through the block in the x and y directions), rather than on the top or bottom (e.g., in the z direction).

[0067] According to the implementation scheme, the detection system can be optimized for up to four detection frequency bands. According to the implementation scheme, the bandwidth can be set by a combination of a mixer, an IF amplifier, and / or an envelope detector. In some implementation schemes, the bandwidth is + / - 20% of the center frequency of the waveguide.

[0068] Now for reference Figure 7 A method 700 for manufacturing a mixer device is provided according to some embodiments. This method can be used, for example, to manufacture a mixer device as described above. Figure 1 The mixer 100 shown in Figure 3, and the mixer used to form Figure 6A The machining parts 602 and 604 shown are illustrated.

[0069] Method 700 may begin with step s710, which includes machining a first housing component (e.g., 602) comprising a first RF channel portion, a first local oscillator portion, a first IF channel portion, a first cavity portion, a first mounting bracket portion, and a second mounting bracket portion. In step s720, a second housing component (e.g., 604) comprising a second RF channel portion, a second local oscillator portion, a second IF channel portion, a second cavity portion, a third mounting bracket portion, and a fourth mounting bracket portion is machined. The method may further include suspending (s730) the waveguide element in the first cavity portion and / or the second cavity portion by mounting the waveguide element on the first and second mounting bracket portions and / or the third and fourth mounting bracket portions. This could be, for example, waveguide element 108. Method 700 may further include attaching (s740) the first housing component to the second housing component to form a block. For example, this method can be used to form a block such as... Figure 6B and Figure 6C The block (or multiple blocks) shown in the diagram.

[0070] According to the implementation, two halves of the complete horn feeder are machined in each half of the block using an outer fillet cutter and a five-axis machine. This allows for flexibility in using horn geometry, such as horn shapes with elliptical cross-sections. This allows for adjusting the horn feeder beam pattern to achieve optimal optical coupling. For example, a circular horn shape provides an elliptical beam that must be corrected in the optics, otherwise the image may have inappropriate astigmatism. However, an elliptical horn feeder can achieve a circular beam that does not require correction. Therefore, and according to some implementations, the horn feeder (e.g., for delivering received RF to mixer 100) can have an elliptical shape.

[0071] Now for reference Figure 8A and Figure 8B The diagram illustrates electric and magnetic fields. For example, Figure 8A The transverse electromagnetic mode 802 is illustrated. When the outer channel of the microstrip line is less than half the waveguide wavelength, typically only the fundamental transverse electromagnetic mode (TEM-00) can exist. In this example, the electric and magnetic field lines are transverse and propagate in the same direction from the inner conductor to the outside of the metal channel or wrap around the filter metallization in the same direction, as shown in 802 (in this example, the conductor is in air). Operation in the fundamental TEM-00 mode can produce a very smooth impedance and frequency response, for example, as shown in 804 depicting the transmission passband. This arrangement is further illustrated in 808, where circuit lines (e.g., gold) 810 are located on a quartz substrate 812.

[0072] The effective microstrip line filter metallization width and outer channel width scale inversely with frequency, and therefore at higher frequencies, the width of the filter metallization pattern and the channel it resides in becomes very small, making the fabrication of both the filter metallization pattern and the channel challenging. This increases cost when the dimensional condition of keeping the outer channel width below half the waveguide wavelength is met. If this condition cannot be met (e.g., either exceeds half the waveguide wavelength), higher-order transverse and longitudinal modes may be excited (e.g., by discontinuities in the channel or filter) and propagate. This scenario is illustrated in 814. The electric and magnetic field lines then become non-uniform and can create resonant conditions, resulting in non-uniform behavior that varies with frequency and leading to reflected power, as illustrated in 806, where resonance occurs in the passband. These resonances can reduce the smooth broadband operation of the mixer.

[0073] Typically, microstrip line filters cascade a quarter-wavelength low-impedance section and a high-impedance section. The filter achieves the best precision when the ratio of high-impedance to low-impedance sections is maximized; this is achieved using the narrowest and widest possible lines. This is determined by… Figure 8B The figures 822 and 824 are shown in the diagram. The performance of such filters is therefore fundamentally limited when considering the generation of higher-order modes, because there is a finite width before the higher-order modes are excited and resonant reflections are introduced into the filter's frequency response. Aspects of this disclosure can provide the benefits of a wider line (e.g., lower impedance and improved filtering) without the negative impact of higher-order mode propagation. This can be achieved, for example, by including current breaks or slots along the length of the filter segment, such as... Figure 8B As shown in 830. This contrasts with 826, in which the current flows uninterruptedly and produces non-ideal passband performance as illustrated in 828. When higher-order modes are formed, the current flow no longer occurs solely in the longitudinal direction as in the case of the fundamental mode, but also travels through the lateral directions of the filter metallization. In the case of introducing a current interruption, these lateral currents are interrupted and the excitation of higher-order modes is suppressed, even if the width of both the filter segment and the channel would otherwise allow for this. A much lower impedance filter segment and smoother filter frequency behavior, as shown in 832, are achieved.

[0074] Now for reference Figure 9 A schematic depiction of a detection system 900 according to some embodiments is provided. In some embodiments, system 500 can use Figure 9 The arrangement will be implemented accordingly.

[0075] Radiation can be received at inputs 902, 904, and 906, which can be horn-shaped feeders of blocks 908, 910, and 912, respectively. In some embodiments, blocks 908, 910, and 912 can each form part of detector arrays 502, 514, 600, 620, and / or 650. The radiated signals received at inputs 902, 904, and 906 are respectively passed to mixer elements depicted as elements 914a, 914b, and 914c. This can be, for example, mixer 100. In some embodiments, one or more of the received signals can be rotated, for example, by an optional polarization rotation element 916, before being processed by the mixer. The processed signal, such as one or more intermediate frequency (IF) signals from the mixer, is passed to the output of each block (918a, 918b, 918c) for further processing by low-noise amplifiers (LNAs) (920a, 920b, 920c), power detectors (921a, 921b, 921c), and analog-to-digital converters (ADCs) (922a, 922b, 922c). Additional processing may include filtering. The digital signal can then be passed to an image generator 924 to form an image based on detected radiation, such as by forming a composite image of an object or scene using radiation received at 902, 904, and 906. Image processing 924 may be coupled to, or be part of, a viewing system 936 such as a computer or monitor. In some embodiments, a coaxial cable is used within each block to output the IF signal.

[0076] Although this system is described as having three mixer elements or inputs, it can be implemented with more or fewer mixer elements or inputs. For example, system 900 can be expanded to include a fourth set of input horn feeders, each input horn feeder having a corresponding set of mixers and processing circuitry. Additionally, each of blocks 908, 910, and 912 may include an input array and multiple mixers 100. Information can be obtained from, for example... Figure 6C The circuits shown in the diagram are stacked to handle this.

[0077] In some implementations, fewer LO sources than the mixer are used to provide the local oscillator (LO) signal to the mixer of system 900. For example, in Figure 9In the example illustrated, a single LO source 926 provides the LO signal to each of mixers 914a to 914c. According to embodiments, this is accomplished by using one or more power dividers 928a, 928b, and in some examples by using one or more frequency multipliers 990a to 990c (such as doublers or triplers). For example, the original LO signal from source 926 can be provided to divider 928a, which in turn provides signals to divider 928b and optional multiplier 990a. Multiplier 930 can be used to provide a higher frequency LO signal to mixer 914a than that provided by source 926. Similarly, divider 928b can provide signals to optional multipliers 930b and 930c used for mixers 914b and 914c. In this respect, each of blocks 908, 910, and 912 can be configured to operate at different frequencies / wavelengths. Such configurations can include, for example, the mixer design and the shape and size of the input horn feeder. Therefore, radiation signals of different wavelengths can be detected, processed, and used by processing circuitry 924 to form a synthetic image using data from multiple wavelengths. One or more amplifiers, such as amplifier 992, can be used to enhance the signal between the source, distributor, multiplier, and / or mixer. Figure 9 Other amplifiers are illustrated in the examples.

[0078] Depending on the application, the size of the horn feeder should be selected to provide optimal coupling with the selected optics, and the spacing should be selected to provide optimal coverage.

[0079] In some aspects, components are optimized to minimize the amount of LO power reflected from the RF coupling circuitry over the widest possible range of circuit operating conditions. This limits the propagation of reflected LO signals back into one or more LO power splitters, thus limiting interference between channels. To further reduce reflection issues, a 90-degree 3dB hybrid power splitter, such as a Magic-T or a 3dB hybrid branch waveguide coupler, can be implemented. Although illustrated with a single LO926, multiple LOs can be used depending on the implementation.

[0080] According to some embodiments, one or more of distributors 928a and 928b are unequal distributors. According to some embodiments, multipliers 930a and 930b are double multipliers, while multiplier 930c is a triple multiplier. In some embodiments, one or more of the multipliers are not required. For example, in some embodiments, multiplier 930a may be omitted.

[0081] According to some implementations, a common local oscillator source 926 is provided, using frequency multipliers of different orders (e.g., doublers and triplers) to multiply the frequency and implement a subharmonic mixer. For example, mixers 914a to 914c can operate in frequency bands centered at 125 GHz, 250 GHz, and 375 GHz, respectively, and the mixers can use local oscillator frequencies of 62.5 GHz, 125 GHz, and 187.5 GHz. In this example, the base local oscillator source 926 can be a Gunn oscillator providing approximately 100 mW operating at 62.5 GHz. This is split into two equal signals using a splitter such as splitter 928a. This can be an equal-power splitter such as a standard magic-T splitter, or an unequal-power splitter. Half of the splitter output pumps the 125 GHz array (block 908 in this example), and the other half is fed into a power amplifier (e.g., amplifier 992 in this example) to provide a signal of approximately 400 mW, which is then used to pump frequency multipliers 930b and 930c. Given the use of subharmonic mixers at the exemplary frequencies, multiplier 930a is not required in this example. In some implementations, the system is optimized by using a configurable unequal power splitter to provide optimal power to the 125 GHz array and the power amplifier. Each frequency mixer array requires similar local oscillator power, 30 mW to 40 mW in this example. However, the typical efficiency of a doubler is 40%, and that of a tripler is 15%. This means that using an equal power splitter such as a Magic T could result in too much power (80 mW) being generated for the 250 GHz array (e.g., block 910 in this example) and marginal power for the 375 GHz array (e.g., block 912 in this example). Traditional power splitters, such as the Magic T, rely on the input power being divided into two equal halves. However, if such a method is used in this implementation, it may result in too much power being supplied to the 125GHz doubler (e.g., multiplier 930b) and insufficient power being supplied to the 187.5GHz tripler (e.g., multiplier 930c). Therefore, in order to supply sufficient power to the tripler, which is typically less efficient than the doubler, the power amplifier would need to be over-specified, and the power going to the doubler would be unnecessarily attenuated (or it might be damaged). Therefore, and according to the implementation, a configurable power divider is used, which can arbitrarily split the local oscillator pump power into two or more paths, thereby distributing power to the multiplier of each local oscillator arm according to their respective power requirements. According to the implementation, dividers 928a and / or 928b are configurable.Therefore, a system can be provided in which the overall system LO power requirement (and thus the cost) is minimized by matching the power shunt to each frequency arm such that the delivered power matches the peak efficiency input power requirement of each corresponding multiplier.

[0082] According to some implementations, one or more blocks configured to receive and process radiation at a fourth frequency can be provided. For example, one or more blocks can be configured at 500 GHz. The mixer for such a block can similarly operate using the same LO source, for example, said LO source at... Figure 9 One or more of the LO paths shown have additional allocators and / or doublers. In some embodiments, the block may be a sub-block or array 514, 620 and / or 650.

[0083] According to some implementations, the LO source 926 may have multiple outputs at one or more frequencies and may not require the initial distributor 928a and / or multiplier 930a. In some implementations, one or more of the distributor 928a and multiplier 930a are integrated into the local oscillator source 926, such that the source 926 provides multiple frequency signals at configurable power. Although two outputs are used in the example manner, this implementation can be extended by using additional unequal power splitters and / or multipliers.

[0084] The Earth's atmosphere provides unique illumination characteristics based on observed frequency transmissions across the atmosphere, which are determined by the amount of water vapor present above the scene and the wavelength used for detection. Two phenomena dominate this effect. First, water molecules have rotational resonances in the millimeter to terahertz domain, causing them to absorb photons at specific frequencies. At frequencies further away from these lines, they allow photons to pass through, which can be understood as water windows. Additionally, as the wavelength shortens, the effective path length across the atmosphere increases, thus increasing attenuation. At the highest transmission frequencies, the Earth's atmosphere is transparent, and therefore the cold background of space provides very high contrast during millimeter-wave detection. Thus, the observed outdoor scene is dominated by "cold" sky illumination. At lower frequencies of transmission through the Earth's atmosphere, the scene is dominated by "warm" illumination from the air column above the scene. Depending on the implementation, and to provide a colored scene in which different contrast types are achieved, a mixture of high, medium, and low transmission wavelengths can be used. Through experimental studies, these have been identified as a bandwidth of approximately 35 GHz centered at 125 GHz, 250 GHz, and 375 GHz.

[0085] Although the implementation scheme uses 125 GHz, 250 GHz, 375 GHz, and 500 GHz as examples, other frequency groups can be used. For example, 60 GHz, 120 GHz, 240 GHz, 360 GHz, and 480 GHz can be used. This frequency group is related to the oxygen absorption properties in the atmosphere.

[0086] While various embodiments of this disclosure are described herein, it should be understood that they are presented by way of example only and not by way of limitation. Therefore, the breadth and scope of this disclosure should not be limited to any embodiment of the exemplary embodiments described above. In general, all terms used herein should be interpreted according to their common meaning in the relevant art, unless a different meaning is clearly given and / or implied from the context of their use. Unless otherwise expressly stated, all references to a / an / said element, device, component, element, step, etc., should be interpreted as referring to at least one example of said element, device, component, element, step, etc. Unless otherwise indicated herein or otherwise clearly contradicted by the context, this disclosure covers any combination of the elements described above in all their possible variations.

[0087] Furthermore, although the processes described above and illustrated in the accompanying drawings are shown as a sequence of steps, this is done solely for illustrative purposes. Therefore, it is contemplated that steps may be added, steps may be omitted, the order of the steps may be rearranged, and steps may be performed in parallel. That is, the steps of any method disclosed herein need not be performed in the exact order disclosed, unless a step is explicitly described as occurring after or before another step, and / or it is implied that a step must occur after or before another step.

Claims

1. A heterodyne mixer device (100), comprising: First input (102); Second input (104); Output (106); A suspended signal transmission element (108) includes multiple suppression slots and at least one filter element; as well as A diode circuit (110) is mounted on the suspended signal transmission element. The suspended signal transmission element includes: A substrate having a first surface and a second surface; as well as A transmission line (202) is located on the first surface, wherein the transmission line is a patterned metal microstrip transmission line including one or more of the suppression groove and the filter element.

2. The apparatus of claim 1, wherein the first input is a local oscillator (LO) input, the second input is a radio frequency (RF) input, the output is an intermediate frequency (IF) signal output, and the suspended signal transmission element is a waveguide element.

3. The apparatus according to claim 1, wherein the substrate is a quartz substrate.

4. The apparatus according to claim 1, Wherein the first input is located between the second input and the output, and The suspended signal transmission element is configured to transmit the signal generated in the diode circuit from the diode circuit to the output along the longitudinal axis of the suspended signal transmission element.

5. The apparatus of claim 4, wherein the signal generated in the diode circuit is an IF signal.

6. The apparatus of claim 1, wherein the apparatus further comprises: The housing (132) has a first mounting bracket (120a), a second mounting bracket (120b), and a cavity. The suspended signal transmission element is mounted in the cavity and on the first and second mounting brackets to form an air gap between the suspended signal transmission element and the housing on at least two sides of the suspended signal transmission element.

7. The device of claim 6, wherein the housing is made of machined metal and the air gaps are formed on the four sides of the suspended signal transmission element.

8. The apparatus of claim 6, wherein the suspended signal transmission element extends between the first mounting bracket and the second mounting bracket along the longitudinal direction of the heterodyne mixer apparatus.

9. The apparatus of claim 1, wherein the apparatus further comprises: Housing, wherein the housing comprises: The first channel is coupled to the first input; The second channel is coupled to the second input; and The third channel is coupled to the output. The second channel includes one or more horn-shaped feeders for the radiation detector, and The first channel and the second channel are arranged along the same plane of the housing, and the third channel is arranged along a direction perpendicular to the plane.

10. The apparatus of claim 9, wherein the radiation detector is a terahertz camera.

11. The apparatus of claim 1, wherein the diode circuit comprises two Schottky diodes configured in anti-parallel.

12. The apparatus according to claim 2, The suspended signal transmission element includes a first filter element for the LO signal and a second filter element for the RF signal, and Each of the first filter element and the second filter element includes one or more of the plurality of suppression slots.

13. The apparatus according to claim 12, Each of the first filter element and the second filter element includes one or more hammer-shaped or semi-hammer-shaped filter components.

14. The apparatus according to claim 1, The patterned metal microstrip line transmission line includes a central line extending from the diode circuit to the output and passing through one or more filter elements. The width of the center line is equal to or greater than 0.1λ, the width of the suspended signal transmission element is 0.3λ, and the thickness of the substrate is less than or equal to 0.1λ. Where λ is the wavelength of the signal received at the second input.

15. The apparatus of claim 14, wherein the signal received at the second input is a detected RF signal.

16. The apparatus of claim 1, wherein the apparatus further comprises: A shell with cavities, The patterned metal microstrip line transmission lines are arranged in the cavity to couple the transmission dipole mode to the sidewall of the housing cavity.

17. The apparatus of claim 1, wherein the signal received at the second input is one of a 125 GHz, 250 GHz, 375 GHz, and 500 GHz signal.

18. The apparatus of claim 1, wherein the apparatus further comprises: A shell with cavities; The first wire is connected to the output; as well as The second wire connects to the inductively tuned capacitor pad and the surface of the housing. The diode circuit is at least partially mounted to the inductively tuned capacitor pad.

19. The apparatus of claim 1, wherein the suspended signal transmission element comprises a single waveguide element suspended between the RF input and the IF output.

20. The apparatus of claim 1, wherein the diode circuit is located at the second input, and wherein the second input is an RF input.

21. The apparatus of claim 1, wherein the suspended signal transmission element includes an RF antenna on the surface of the suspended signal transmission element.

22. The apparatus according to claim 1, The plurality of suppression slots include a plurality of gaps on the surface of the suspended signal transmission element, and Each of the plurality of gaps is elongated along the longitudinal direction of the suspended signal transmission element.

23. A detector device, comprising: One or more mixers; One or more horn-shaped feeders are coupled to the RF input of at least one of the mixers; A local oscillator (508) is coupled to the LO input of at least one of the mixers; An output channel coupled to the IF output of at least one of the mixers; as well as One or more of a low-noise amplifier, a power detector, and an analog-to-digital converter are connected to the output channel and configured to process the output IF signal from at least one of the mixers. The one or more mixers mentioned above include: A suspended signal transmission element, comprising multiple suppression slots and one or more filter elements; as well as The diode circuit mounted on the suspended signal transmission element, The detector device mentioned above is a terahertz camera, and The one or more mixers mentioned above include multiple mixers optimized at 250 GHz and multiple mixers optimized at 375 GHz.

24. The detector apparatus of claim 23, wherein the diode circuit is configured to generate the IF output signal based on radiation received on one or more of the horn-shaped feeders and a power signal from the local oscillator.

25. The detector device according to claim 23, The one or more mixers mentioned above also include multiple mixers optimized at 125 GHz.

26. A heterodyne mixer device, comprising: First input; Second input; Output; A suspended signal transmission element, comprising multiple suppression slots and at least one filter element; A diode circuit mounted on the suspended signal transmission element; as well as The housing has a first mounting bracket, a second mounting bracket, and a cavity. The suspended signal transmission element is mounted in the cavity and on the first and second mounting brackets to form an air gap between the suspended element and the housing on at least two sides of the suspended waveguide.

27. A heterodyne mixer device, comprising: First input; Second input; Output; A suspended signal transmission element, comprising multiple suppression slots and at least one filter element; A diode circuit mounted on the suspended signal transmission element; A diode circuit is mounted on the suspended signal transmission element; The shell has a cavity. The first wire is connected to the output; as well as The second wire connects to the inductively tuned capacitor pad and the surface of the housing. The diode circuit is at least partially mounted to the inductively tuned capacitor pad.

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