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EP-4078806-B1 - A COMPACT OSCILLATOR DEVICE WITH A CAVITY RESONATOR ON A CIRCUIT BOARD

EP4078806B1EP 4078806 B1EP4078806 B1EP 4078806B1EP-4078806-B1

Inventors

  • HÖRBERG, Mikael
  • SANDBERG, JAN
  • SJÖBERG, Daniel
  • LIDSTRÖM, Niklas

Dates

Publication Date
20260506
Application Date
20191216

Claims (15)

  1. An oscillator device (1, 1', 1", 1"') comprising an active circuit device (2), a circuit board (3) and a cavity resonator (4, 4'), where the active circuit device (2) comprises an amplifier unit (5), and where the circuit board (3) comprises a first main side (6) and a second main side (7), where the active circuit device (2) is mounted to the first main side (6), wherein the cavity resonator (4, 4') is positioned on the second main side (7), where the oscillator device (1) further comprises at least one excitation via connection (8) that runs through the circuit board (3) and electrically connects the active circuit device (2) to an excitation structure (9) inside the cavity resonator (4), the oscillator device being characterized in that the excitation via connection (8) is positioned between the active circuit device (2) and the cavity resonator (4, 4').
  2. The oscillator device (1, 1', 1", 1‴) according to claim 1, wherein the cavity resonator (4, 4') comprises electrically conducting inner walls (10a, 10b, 10c, 10d, 10e, 10f).
  3. The oscillator device (1, 1', 1", 1‴) according to any one of the claims 1 or 2, wherein the circuit board (3) comprises a first main side metallization (12), a second main side metallization (18), and at least one dielectric layer (20) positioned between the first main side metallization (12) and the second main side metallization (18).
  4. The oscillator device (1, 1', 1", 1‴) according to claim 3, wherein the active circuit device (2) is electrically connected to mounting pads (11a, 11b, 11c, 11d, 11e) comprised in the first main side metallization (12), where at least one mounting pad (11c) is connected to the excitation via connection (8).
  5. The oscillator device (1, 1', 1", 1‴) according to any one of the claims 3-4, wherein a closing wall (10a) of the cavity resonator is comprised in a first metallization part (17a) on the second main side (7).
  6. The oscillator device (1, 1', 1", 1"') according to claim 5, wherein the excitation structure (9) comprises a second metallization part (17b) on the second main side (7), electrically separated from the first metallization part (17a) on the second main side (7), where the first metallization part (17a) and the second metallization part (17b) are comprised in the second main side metallization (18).
  7. The oscillator device (1, 1', 1", 1‴) according to any one of the claims 5 or 6, wherein the cavity resonator (4, 4') is formed by an electrically conducting first lid (21, 21'; 22), and the closing wall (10a), where the electrically conducting first lid (21, 21'; 22) comprises an opening (23, 24) that is facing the closing wall (10a).
  8. The oscillator device (1") according to claim 7, wherein the electrically conducting first lid (22) is adapted to cover at least a major part of the second main side (7).
  9. The oscillator device (1") according to claim 8, wherein the electrically conducting first lid (22) is from a piece of metal and comprises a circumferentially running protruding edge (25) that surrounds the opening (24).
  10. The oscillator device (1"') according to any one of the previous claims, wherein the active circuit device (2‴) comprises an active layer (30), where the active circuit device (2‴) further comprises an internal via signal connection (31) that connects the excitation via connection (8) to the active layer (30).
  11. The oscillator device (1') according to any one of the previous claims, wherein the oscillator device (1') comprises a tuning element (13) positioned within the cavity resonator (4').
  12. The oscillator device (1') according to claim 11, wherein the tuning element (13) is constituted by an electrically conducting body (14) and a holding rod (15a, 15b), where the holding rod (15a, 15b) is attached to the electrically conducting body (14) and is movable from the outside of the cavity resonator (4') via openings (16a, 16b) in the cavity resonator (4') such that the electrically conducting body (14) can be moved between a plurality of positions within the cavity resonator (4') by means of the holding rod (15a, 15b).
  13. The oscillator device (1") according to any one of the previous claims, wherein the excitation structure (9) comprises a sub-structure (26) that protrudes into the cavity resonator (4).
  14. The oscillator device (1) according to any one of the previous claims, wherein the oscillator device (1) comprises at least one ground via connection (27a, 27b) that runs through the circuit board (3) and electrically connects the active circuit device (2) to the first metallization part (17) on the second main side (7).
  15. A method of configuring an oscillator device (1, 1', 1", 1‴) comprising an active circuit device (2, 2‴), a circuit board (3) and a cavity resonator (4, 4'), where the active circuit device (2, 2‴) comprises an amplifier unit (5) and the circuit board (3) comprises a first main side (6) and a second main side (7), where the method comprises providing (S1) a partial metallization on each main side (6, 7); and mounting (S2) the active circuit device (2, 2‴) to the first main side (6); wherein the method further comprises: positioning (S3) the cavity resonator (4, 4') on the second main side (7); and providing (S4) at least one excitation via connection (8) that runs through the circuit board (3) and electrically connects the active circuit device (2, 2‴) to an excitation structure (9) inside the cavity resonator (4, 4'), the method being characterized in that the excitation via connection (8) is positioned between the active circuit device (2) and the cavity resonator (4, 4').

Description

TECHNICAL FIELD The present disclosure relates to an oscillator device comprising an active circuit device with an amplifier unit, where the oscillator device further comprises a cavity resonator. BACKGROUND Oscillators are used for delivering a signal with a predetermined frequency, which may be adjustable. However, all oscillators that are set to a certain frequency tend to vary slightly around said frequency. This variation is known as phase noise. In order to achieve low phase noise in an oscillator, it is well known that one of the main contributing parameters is the losses of the resonator, measured by its so-called Q factor, where a high Q means low losses and low phase noise. Especially for a Voltage Controlled Oscillator (VCO) where an electrical tuning element is coupled to the resonator, it is very difficult to acquire a low phase noise. Millimeter-wave (mmW) beyond 100 GHz is becoming popular as telecommunication systems, vehicle radars and imaging sensors are to be made in frequencies of hundreds GHz, where demands on low phase noise for the frequency generation is increasing. The phase noise limitations in the oscillators are often the bottleneck for more complex modulation in a communication system and for the resolution and range in radar systems. There exist a vast number of different technologies for realizing an oscillator. Basically, an oscillator is formed by an amplifier that is coupled to a resonator, where the resonator normally incorporates the tuning element. A resonator can be built from microstrip or stripline structures on a substrate. It can also be built from discrete LC components, dielectric resonators, waveguide cavities or variants of these. The tuning element can be a varactor diode, ferroelectric material or some other variable reactance structure. The total Q of a resonator structure depends on the combined resistive losses of the respective components. The difficulties to generate a high oscillation frequency leads to the usage of a fundamental oscillator at a lower frequency, which is multiplied several times to serve the desired frequency. Therefore, an increase in phase noise level is inevitably in the frequency multiplication. The remedy can be to use a very low phase noise oscillator with high performance at lower frequency realized as a metal cavity oscillator or as a dielectric resonator oscillator (DRO). For tunability, the latter one is more difficult as most of the electromagnetic field are bounded internally in the dielectric and cannot easily be externally affected which is needed for tuning. Therefore, metal cavities are preferred, where a tuning mechanism can be placed inside the cavity, where examples of metal cavity oscillators are disclosed in for example WO 2016066227 and EP 2724415. US2018/183130 A1 describes an oscillator or amplifier module including a substrate carrying an active circuit chip and a resonant cavity or filter structure formed by a metallic housing or lid attached over the substrate. The resonator can be implemented as a dielectric-loaded or air cavity. Electrical connection between the active die and the resonator structure is made via bond wires or microstrip lines on the substrate. Vias are used internally for grounding and for RF feed-throughs between layers of the substrate. However, an implementation of a cavity oscillator requires large effort and the connection for the active device to the cavity can be bulky and unfriendly for volume production. There might be assembly difficulties due to the large size of the cavity compared to the small size of the active device implementation which normally is on packaged or bare die. Furthermore, the coupling structure to the resonator for RF-excitation often entails a distance to the active device which is critical for the phase condition. This distance can limit the tuning bandwidth to fulfil the phase condition for optimal oscillation. The coupling impedance to the resonator is also critical, and sensitive for variations. The remedy is to use a minimum number of physical interfaces and a higher integration. Furthermore, tunability of the cavity are often today made by quite complex and bulky arrangements, e.g. by screws, trombones for phase adjusting, There is thus a need for an enhanced oscillator device that comprises a cavity resonator, such as a metal cavity resonator or metalized cavity resonator, where the above drawbacks are alleviated. SUMMARY The object of the present disclosure is to provide an enhanced oscillator device that comprises an active circuit device with an amplifier unit, where the oscillator device further comprises a cavity resonator. This object is achieved by means of an oscillator device comprising an active circuit device, a circuit board and a cavity resonator. The active circuit device comprises an amplifier unit, and the circuit board comprises a first main side and a second main side. The active circuit device is mounted to the first main side, and the