EP-4736328-A1 - RADIO SYSTEM INCLUDING ONE OR MORE TUNABLE LOW PASS FILTERS FOR SUPPRESSING HARMONICS AND AN ASSOCIATED METHOD

Abstract

A radio system comprises: a wide-band transmitter configured to generate one or more radio transmission signals; and one or more tunable low pass filters (LPFs), coupled between the wide-band transmitter and a transmission antenna, each of the tunable LPFs being configured to filter one or more given transmission signals of the radio transmission signals. Each of the tunable LPFs includes a printed part consisting of printed components, and a discrete part consisting of discrete components. The radio system further comprises a controller configured to tune a given tunable LPF of the tunable LPFs for filtering a given transmission signal of the given transmission signals that are filtered by the given tunable LPF, by manipulating the printed part and the discrete part of the given tunable LPF.

Inventors

• HAGAY, Avraham
• WAISBLAY, Mark

Assignees

• Elbit Systems C4I and Cyber Ltd.

Dates

Publication Date

20260506

Application Date

20240624

Claims (17)

1. 1. A radio system, comprising: a wide-band transmitter configured to generate one or more radio transmission signals; one or more tunable low pass filters (LPFs), coupled between the wide-band transmitter and a transmission antenna, each tunable LPF of the tunable LPFs being configured to filter one or more given transmission signals of the radio transmission signals, and including: a printed part consisting of printed components; and a discrete part consisting of discrete components; and a controller configured to tune a given tunable LPF of the tunable LPFs for filtering a given transmission signal of the given transmission signals that are filtered by the given tunable LPF, by manipulating the printed part and the discrete part of the given tunable LPF.
2. 2. The radio system of claim 1, wherein a lowest cutoff frequency at which the given tunable LPF is capable of operating is less than 65% of a highest cutoff frequency at which the given tunable LPF is capable of operating.
3. 3. The radio system of claim 1 , wherein the discrete components in the given tunable LPF include PIN diodes that are connected to the printed part of the given tunable LPF, and wherein the manipulating of both the discrete part and the printed part of the given tunable LPF is achieved by changing a state of one or more of the PIN diodes in the given tunable LPF.
4. 4. The radio system of claim 1, wherein the printed components in the printed part of the given tunable LPF include filtering printed components, and wherein the manipulating of the printed part of the given tunable LPF includes manipulating electrical values of the filtering printed components.
5. 5. The radio system of claim 3, wherein a lowest cutoff frequency at which the given tunable LPF is capable of operating is less than 65% of a highest cutoff frequency at which the given tunable LPF is capable of operating; and wherein parasitic characteristics of the PIN diodes enable the given tunable LPF to operate at the lowest cutoff frequency.
6. 6. The radio system of claim 5, wherein the parasitic characteristics include: (a) a series resistance at 10 milliamperes (mA) that is less than one Ohm (Q) to form a short circuit, and (b) a capacitance at 50-400 Volts (V) that is between 0.33 and 0.37 picofarads (pF) to form an open circuit.
7. 7. A tunable low-pass filter (LPF), comprising: a printed part consisting of printed components; and a discrete part consisting of discrete components; wherein the tunable LPF is tunable by manipulating the printed part and the discrete part; and wherein a lowest cutoff frequency at which the tunable LPF is capable of operating is less than 65% of a highest cutoff frequency at which the tunable LPF is capable of operating.
8. 8. The tunable LPF of claim 7, wherein the discrete components include PIN diodes that are connected to the printed part of the tunable LPF, and wherein the manipulating of both the discrete part and the printed part of the tunable LPF is achieved by changing a state of one or more of the PIN diodes in the tunable LPF.
9. 9. The tunable LPF of claim 7, wherein the printed components in the printed part of the given tunable LPF include filtering printed components, and wherein the manipulating of the printed part includes manipulating electrical values of the filtering printed components.
10. 10. The tunable LPF of claim 8, wherein parasitic characteristics of the PIN diodes enable the tunable LPF to operate at the lowest cutoff frequency.
11. 11. The tunable LPF of claim 10, wherein the parasitic characteristics include: (a) a series resistance at 10 milliamperes (mA) that is less than one Ohm (Q) to form a short circuit, and (b) a capacitance at 50-400 Volts (V) that is between 0.33 and 0.37 picofarads (pF) to form an open circuit.
12. 12. A method for processing a radio transmission signal, the method comprising: tuning a tunable low pass filter (LPF), by a controller, for filtering the radio transmission signal; generating, by a wide-band transmitter, the radio transmission signal; and filtering, by the tunable LPF, the radio transmission signal; wherein the tunable LPF includes: a printed part consisting of printed components, and a discrete part consisting of discrete components; and wherein the tunable LPF is tuned by manipulating the printed part and the discrete part.
13. 13. The method of claim 12, wherein a lowest cutoff frequency at which the tunable LPF is capable of operating is less than 65% of a highest cutoff frequency at which the tunable LPF is capable of operating.
14. 14. The method of claim 12, wherein the discrete components include PEST diodes that are connected to the printed part, and wherein the manipulating of both the discrete part and the printed part is achieved by changing a state of one or more of the PEST diodes.
15. 15. The method of claim 12, wherein the printed components in the printed part include filtering printed components, and wherein the manipulating of the printed part includes manipulating electrical values of the filtering printed components.
16. 16. The method of claim 14, wherein a lowest cutoff frequency at which the tunable LPF is capable of operating is less than 65% of a highest cutoff frequency at which the tunable LPF is capable of operating; and wherein parasitic characteristics of the PEST diodes enable the tunable LPF to operate at the lowest cutoff frequency.
17. 17. The method of claim 16, wherein the parasitic characteristics include: (a) a series resistance at 10 milliamperes (mA) that is less than one Ohm (Q) to form a short circuit, and (b) a capacitance at 50-400 Volts (V) that is between 0.33 and 0.37 picofarads (pF) to form an open circuit.

Description

RADIO SYSTEM INCLUDING ONE OR MORE TUNABLE LOW PASS FILTERS FOR SUPPRESSING HARMONICS AND AN ASSOCIATED METHOD TECHNICAL FIELD The invention relates to a radio system including one or more tunable low pass filters for suppressing harmonics and an associated method. BACKGROUND Conventionally, a radio system having a high-power wide-band transmitter includes a large number of low pass filters (LPFs) for filtering out harmonics that are generated by the transmitter. The use of a large number of LPFs in a radio system has deficiencies. For each additional LPF that is included in the radio system, a transmission power of transmission signals at the transmission antenna is reduced. Specifically, for each additional LPF, there is a greater attenuation of transmission signals by the Radio Frequency (RF) switch that routes the transmission signals to the LPFs and by the RF switch that routes the transmission signals from the LPFs to the transmission antenna. Moreover, each additional LPF includes energy consuming components, such as capacitors and induction coils, thereby further attenuating transmission signals. The attenuation of the transmission signals results in the reduced transmission power of the transmission signals at the transmission antenna. Another deficiency resulting from each additional LPF that is included in the radio system is that the size of the radio system increases with each LPF that is included in the radio system. The present disclosure addresses the aforementioned deficiencies by including one or more tunable LPFs in the radio system. References considered to be relevant as background to the presently disclosed subject matter are listed below. Acknowledgement of the references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter. U.S. Patent Application Publication No. 2015/0235971, published on August 20, 2015, discloses an apparatus and method for a frequency based integrated circuit that selectively filters out unwanted bands or regions of interfering frequencies utilizing one or more tunable notch or bandpass filters or tunable low or high pass filters capable of operating across multiple frequencies and multiple bands in noisy RF environments. The tunable filters are fabricated within the same integrated circuit package as the associated frequency-based circuitry, thus minimizing R, L, and C parasitic values, and also allowing residual and other parasitic impedance in the associated circuitry and IC package to be absorbed and compensated. U.S. Patent No. 7,567,782, published on July 28, 2009, provides methods and apparatus to enable a transceiver or transmitter including a single PA line-up to transmit signals having frequencies in two or more different frequency bands, and/or having two or more different modulation types, and/or having two or more different RF power levels. The single PA line-up includes at least one variable matching circuit and a variable harmonic filter to tune match and tune filter communication signals prior to transmission. The variable matching circuit and the variable harmonic filter each include at least one variable capacitive element that switches ON/OFF depending on whether a low frequency signal or a high frequency signal is being transmitted. Each variable capacitive element includes separate direct current and radio frequency terminals to enable the single PA line-up to change signal modulation and/or RF power levels in addition to frequencies. Singhal, H.K. and Rawat, K., “Digitally Assisted Harmonic Cancellation for MultiOctave Filter-Less Transmitter,” IEEE Access, Volume 8, 7 April 2020, DOI: 10.1109/ ACCESS.2020.2986264, presents and demonstrates the design of a filter-less transmitter architecture with digitally assisted harmonic cancellation. A neural network is used to model the harmonics as well as intermodulation distortion (IMD) for digital predistortion applications. This neural network-based harmonic modeling does not require any reference signal to be injected at the input of Power Amplifier (PA), which is an in-house 10 Watts PA operating from Very High Frequency (VHF) to L-band. This PA is used along with an agile Radio Frequency (RF) transceiver. The receiver of the transceiver captures the nonlinearity of the PA in terms of harmonics as well as IMD components for modeling and predistortion. The architecture can handle all types of distortions due to hardware as well as PA nonlinearity. Besides, it is also able to cancel the harmonics using a harmonic injection in the feed-forward configuration. The scheme is demonstrated to transmit 5 MHz LTE signal at different frequencies over the range of 100 MHz to 400 MHz. In such a case, the second and third harmonics appear over the frequency range from 200 MHz to 1.2 GHz, which are within the amplification range of PA, yet they are suppressed without using any filter at the output. More than -40 dBc harmonic