PL247402B1 - Wide-tuning planar bandpass filter microwave cell circuit with increased steepness of edges - Google Patents

Abstract

A microwave cell circuit of a planar band-pass filter with a wide tuning range and increased steepness of edges constructed from four capacitive diodes and eleven sections of microstrip transmission lines with advantageously selected characteristic impedances and lengths, made on a dielectric substrate with a metallized mass layer, characterized in that the input gate (WWE) of the filter constitutes the first end (KL1-1) of the first line (L1) bent at a right angle at a advantageously selected point, the second end (KL1-2) of the first line (L1) is connected to the first end (KL2-1) of the second line (L2) and to the first end (KL3-1) of the third line (L3), while the second end (KL2-2) of the second line (L2) is connected to the anode of the first capacitive diode (D1), the cathode of the first capacitive diode (D1) is connected simultaneously to the cathode of the second capacitive diode (D2) and to the first lead (KR1-1) of the first a resistor (R1), and the anode of the second diode (D2) is connected to the first end (KL4-1) of the fourth line (L4), the second end (KL4-2) of the fourth line (L4) is connected simultaneously to the first end (KL7-1) of the seventh line (L7) and to the first end (KL10-1) of the tenth line (L10) and to the second end (KL6-2) of the sixth line (L6), the second end (KL7-2) of the seventh line (L7) is connected by means of the second via (V2) to the mass of the system, the first end (KL6-1) of the sixth line (L6) is connected simultaneously to the second end (KL3-2) of the third line (L3) and to the second end (KL5-2) of the fifth line (L5) and to the first end (KL8-1) of the eighth line (L8), wherein the first end (KL5-1) of the fifth line (L5) is connected to the mass of the system by means of the first via (V1), the second end (KL8-2) of the eighth line (L8) is connected to the anode of the third capacitive diode (D3), the cathode of the third capacitive diode (D3) is connected simultaneously to the cathode of the fourth capacitive diode (D4) and to the first lead (KR2-1) of the second resistor (R2), the anode of the fourth diode (D4) is connected to the first end (KL9-1) of the ninth line (L9), the second end (KL9-2) of the ninth line (L9) is connected simultaneously to the second end (KL10-2) of the tenth line (L10) and to the first end (KL11-1) of the eleventh line (L11), the eleventh line (L11) is bent at a right angle at a favorably selected point, the second end (KL11-2) of the eleventh line (L11) is connected to the output gate (WWY) of the circuit, the second end (KR1-2) of the first resistor (R1) and the second end (KR2-2) of the second resistor (R2) are connected to the control voltage (VD).

Description

Description of the invention

The subject of the invention is a microwave cell system of a planar band-pass filter with a wide tuning range and increased steepness of the edges.

Known methods of implementing planar electrically tunable bandpass filters for microwave ranges are based on the use of capacitive diodes or MEMS condensates as variable reactances for their tuning. These filters are built from resonators tunable by means of variable reactances, mutually coupled. In practice, galvanic coupling or coupling through an electromagnetic field is used. Filter resonators are made of microstrip, strip or coplanar lines, the electrical length of which changes during tuning.

An important property of bandpass filters, apart from passband attenuation and stopband attenuation, is the steepness of their characteristics in transition bands. The steepness of the bandpass filter slopes is improved by introducing additional attenuation poles into the filter characteristics. Additional attenuation poles can be obtained by adding shorted or open transmission line sections to the filter structure, jointly adding high-pass and low-pass sections, jointly adding bandpass and bandstop sections, and by using multiple couplings between its resonators.

The technical issue that requires a solution is the development of a new planar band-pass filter microwave cell circuit with a wide tuning range and increased steepness of the slopes in the transition band of the transfer characteristic.

This goal was achieved thanks to the filter structure with triple inductive coupling between the resonators, which allows to obtain two damping poles located below the lower cut-off frequency and above the upper cut-off frequency of the filter, which improves the steepness of the characteristics in the transition bands.

A planar microwave cell circuit of a bandpass filter with a wide tuning range and increased steepness of edges constructed of four capacitive diodes and eleven sections of microstrip transmission lines with advantageously selected characteristic impedances and lengths, made on a dielectric substrate with a metallized ground layer, characterized in that the filter input gates constitute the first end of the first line bent at a right angle, at a advantageously selected point, the second end of the first line is connected to the first end of the second line and to the first end of the third line, while the second end of the second line is connected to the anode of the first capacitive diode, the cathode of the first capacitive diode is connected simultaneously to the cathode of the second capacitive diode and to the first lead of the first resistor, and the anode of the expensive diode is connected to the first end of the fourth line, the second end of the fourth line is connected simultaneously to the first end of the seventh line and to the first end of the tenth line and to the second end of the sixth line, the second end of the seventh line is connected by means of a second via to the ground of the system, the first end of the sixth line is connected simultaneously to the second end of the third line and to the second end of the fifth line and to the first end of the eighth line, wherein the first end of the fifth line is connected to the mass of the system by means of the first via, the second end of the eighth line is connected to the anode of the third capacitive diode, the cathode of the third capacitive diode is connected simultaneously to the cathode of the fourth capacitive diode and to the first lead of the second resistor, the anode of the fourth diode is connected to the first end of the ninth line, the second end of the ninth line is connected simultaneously to the second end of the tenth line and to the first end of the eleventh line, the eleventh line is bent at a right angle at a preferably selected point, the second end of the eleventh line is connected to the output gate of the system, the second end of the first resistor and the second end of the second resistor are connected to the control voltage.

The advantage of the solution according to the invention is the possibility of obtaining a filter cell with a large tuning range having two damping poles occurring in the upper and lower transition bands, the occurrence of which improves the steepness of the filter characteristic slopes. The damping pole frequencies are tuned concurrently with the filter center frequency, and the ratio of the damping pole frequencies to the filter center frequency is constant over the entire tuning range.

Obtaining additional damping poles in the filter characteristic is achieved by using triple inductive coupling between the resonators constituting it.

The use of a series connection of capacitive diodes and transmission lines in the circuit, thanks to the absorption of the diodes' own inductance, allows the construction of filters operating in the frequency range close to the diodes' self-resonance frequency and facilitates obtaining a wide tuning range.

The subject of the invention is explained in an example embodiment in the drawing, which shows a diagram of a microwave cell circuit of a planar band-pass filter with a wide tuning range and increased steepness of the edges.

The circuit is a bandpass two-circuit filter implemented on a dielectric substrate using microstrip technology. The signal is supplied from the input gate (WWE), which is the first end (KL1-1) of the line (L1). The line (L1) acts as a transformer raising the load impedance of the first filter resonator. The first filter resonator consists of cascade-connected lines (L2), (L3), (L4), two capacitive diodes (D1), (D2) and a P1-type circuit consisting of lines (L5), (L6), (L7) with vias (V1) and (V2). The line (L3) of an advantageously selected length together with the line (L1) allow for optimal matching of the impedance of the signal source connected to the input gate (WWE). The lines (L5), (L6), (L7) forming the P1-type circuit together with vias (V1), (V2) are elements of the coupling circuit of both filter resonators. This solution of the coupling circuit allows to obtain in the frequency characteristic of the filter two attenuation poles occurring in its upper and lower transition band. The signal from the first resonator (R1) is fed through the mentioned coupling circuit to the second resonator (R2). The second filter resonator is made of cascade-connected lines (L8), (L9), (L10), two series-connected capacitive diodes (D3), (D4) and a P1-type coupling circuit made of lines (L5), (L6), (L7) together with vias (V1) and (V2). The signal from the expensive resonator (R2) is fed by means of a transmission line (L11) of an advantageously selected length to the output gate (WWY) of the filter. Line (L11) is an impedance transformer that increases the load impedance of the second resonator and together with line (L10) allows for optimal matching of the load impedance connected to the gate (WWY). The lines (L1) and (L11) are bent at right angles at advantageously selected points in order to reduce the area occupied by the filter circuit. The tunable filter is a voltage (VD) supplied to the interconnected cathodes of both pairs of capacitive diodes through resistors (R1) and (R2). The input gate (WWE) of the filter is the first end (KL1 -1) of the first line (L1) bent at right angles at a advantageously selected point. The second end (KL1 - 2) of the first line (L1) is connected to the first end (KL2-1) of the second line (L2) and to the first end (KL3-1) of the third line (L3), while the second end (KL2-2) of the second line (L2) is connected to the anode of the first capacitive diode (D1). The cathode of the first capacitive diode (D1) is connected simultaneously to the cathode of the second capacitive diode (D2) and to the first lead (KR1-1) of the first resistor (R1), and the anode of the second diode (D2) is connected to the first end (KL4-1) of the fourth line (L4). The other end (KL4-2) of the fourth line (L4) is connected simultaneously to the first end (KL7-1) of the seventh line (L7) and to the first end (KL10-1) of the tenth line (L10) and to the second end (KL6-2) of the sixth line (L6). The other end (KL7-2) of the seventh line (L7) is connected by means of the second via (V2) to the mass of the system. The first end (KL6-1) of the sixth line (L3) is connected simultaneously to the second end (KL3-2) of the third line (L3) and to the second end (KL5-2) of the fifth line (L5) and to the first end (KL8-1) of the eighth line (L8), the first end (KL5-1) of the fifth line (L5) being connected to the ground of the system by means of the first via (V1). The second end (KL8-2) of the eighth line (L8) is connected to the anode of the third capacitive diode (D3), the cathode of the third capacitive diode (D3) is connected simultaneously to the cathode of the fourth capacitive diode (D4) and to the first lead (KR2-1) of the second resistor (R2). The anode of the fourth diode (D4) is connected to the first end (KL9-1) of the ninth line (L9), and the second end (KL9-2) of the ninth line (L9) is connected simultaneously to the second end (KL10-2) of the tenth line (L10) and to the first end (KL11-1) of the eleventh line (L11). The eleventh line (L11) is bent at a right angle at a favorably selected point, while the second end (KL11-2) of the eleventh line (L11) is connected to the output gate (WWY) of the circuit. The second end (KR1-2) of the first resistor (R1) and the second end (KR2-2) of the second resistor (R2) are connected to the control voltage (VD).

Claims (1)

Patent Claim 1. A microwave cell circuit of a planar bandpass filter with a wide tuning range and increased steepness of edges, constructed of four capacitive diodes and eleven sections of microstrip transmission lines with advantageously selected characteristic impedances and lengths, made on a dielectric substrate with a metallized mass layer, characterized in that the input gate (WWE) of the filter is the first end (KL1-1) of the first line (L1) bent at a right angle at a advantageously selected point, the second end (KL1-2) of the first line (L1) is connected to the first end (KL2-1) of the second line (L2) and to the first end (KL3-1) of the third line (L3), while the second end (KL2-2) of the second line (L2) is connected to the anode of the first capacitive diode (D1), the cathode of the first capacitive diode (D1) is connected simultaneously to the cathode of the second capacitive diode (D2) and to the first lead (KR1-1) of the first resistor (R1), and the anode of the expensive diode (D2) is connected to the first end (KL4-1) of the fourth line (L4), the second end (KL4-2) of the fourth line (L4) is connected simultaneously to the first end (KL71) of the seventh line (L7) and to the first end (KL10-1) of the tenth line (L10) and to the second end (KL6-2) of the sixth line (L6), the second end (KL7-2) of the seventh line (L7) is connected by means of the second via (V2) to the mass of the system, the first end (KL6-1) of the sixth line (L6) is connected simultaneously to the second end (KL3-2) of the third line (L3) and to the second end (KL5-2) of the fifth line (L5) and to the first end (KL8-1) of the eighth line (L8), wherein the first end (KL5-1) of the fifth line (L5) is connected to the mass of the system by means of the first via (V2) vias (V1), the second end (KL8-2) of the eighth line (L8) is connected to the anode of the third capacitive diode (D3), the cathode of the third capacitive diode (D3) is connected simultaneously to the cathode of the fourth capacitive diode (D4) and to the first lead (KR2-1) of the second resistor (R2), the anode of the fourth diode (D4) is connected to the first end (KL9-1) of the ninth line (L9), the second end (KL9-2) of the ninth line (L9) is connected simultaneously to the second end (KL10-2) of the tenth line (L10) and to the first end (KL11-1) of the eleventh line (L11), the eleventh line (L11) is bent at a right angle at a favorably selected point, the second end (KL11-2) of the eleventh line (L11) is connected to the output gate (WWY) of the circuit, the second end (KR1-2) of the first resistor (R1) and the other end (KR2-2) of the second resistor (R2) are connected to the control voltage (VD).