L-band receiving frequency conversion circuit

Abstract

The utility model discloses an L-band receiving frequency conversion circuit, which mainly solves the problems of poor filtering effect and clutter suppression effect of the conventional L-band receiving circuit. The circuit comprises a receiving antenna, a two-stage filtering and amplifying circuit connected with the receiving antenna, a frequency mixing circuit connected with the two-stage filtering and amplifying circuit, a local oscillation generating circuit connected with a local oscillation input end of the frequency mixing circuit, and an output amplifying and filtering circuit connected with the frequency mixing circuit. The L wave band receiving frequency conversion circuit mainly aims at capturing certain mobile phone signals in a certain special area, two times of filtering are adopted, a good cavity filter is adopted for input, a unique LC filter is adopted for output for filtering, and therefore the output intermediate frequency filtering effect is good, and the frequency conversion efficiency is high. And the signal is provided for a collector in a relatively small band, so that the collected signal has higher reliable value.

Description

Technical Field

[0001] The utility model belongs to the technical field of wireless communication, and in particular relates to an L-band receiving frequency conversion circuit. Background Art

[0002] With the rapid advancement of technology, the transmission of information has shown a trend of significant improvement. Data transmission over short distances can be accomplished through wired networks, but due to the problem of signal attenuation, wired transmission is easily limited by distance. Therefore, the application occasions of wireless transmission are increasing day by day. Since wireless transmission has a wide radiation area, it has good mobility. Among them, satellite communication systems are a widely used data transmission method.

[0003] In the communication system, due to the division of spectrum and the needs of various application scenarios, there will be various frequency designs. Therefore, at the receiving end, there will be different frequency receiving frequency conversion links. The commonly used design is to design the corresponding receiving frequency conversion link according to the specific application frequency band. However, when the frequency changes, this receiving frequency conversion link is not applicable, and there are problems such as poor intermediate frequency filtering effect and poor clutter suppression effect during frequency conversion reception. Utility Model Content

[0004] The utility model aims to provide an L-band receiving frequency conversion circuit, which mainly solves the problems of poor frequency filtering effect and poor clutter suppression effect of the existing L-band receiving circuit.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0006] An L-band receiving frequency conversion circuit comprises a receiving antenna, a two-stage filtering and amplifying circuit connected to the receiving antenna, a mixing circuit connected to the two-stage filtering and amplifying circuit, a local oscillator generating circuit connected to a local oscillator input end of the mixing circuit, and an output amplifying and filtering circuit connected to the mixing circuit.

[0007] Furthermore, in the utility model, the two-stage filtering and amplifying circuit includes a capacitor C1, a filter N1, a capacitor C2, an amplifier N12, a capacitor C3, an amplifier N13, a capacitor C4, a resistor R1 and a capacitor C5 which are sequentially connected to the receiving antenna, a resistor R2 having one end connected between the capacitor C4 and the resistor R1 and the other end grounded, and a resistor R3 having one end connected between the resistor R1 and the capacitor C5 and the other end grounded; wherein the other end of the capacitor C5 is connected to the mixing circuit.

[0008] Furthermore, in the present invention, the mixing circuit includes a mixer N5 whose RF input is connected to the other end of the capacitor C5, a capacitor C28, a resistor R5 and a capacitor C29 connected in sequence to the intermediate frequency output end of the mixer N5, a resistor R8 connected between the capacitor C28 and the resistor R5 and the other end of which is grounded, and a resistor R6 connected between the capacitor C29 and the resistor R5 and the other end of which is grounded; wherein the other end of the capacitor C29 is connected to the output amplification and filtering circuit.

[0009] Furthermore, in the utility model, the local oscillator generating circuit includes a reference source N7, a capacitor C9 connected to the output end of the reference source N7, an amplifier N8 having an input end connected to the other end of the capacitor C9, a capacitor C8 connected to the output end of the amplifier N8, a local oscillator generator U1 connected to the other end of the capacitor C8, a capacitor C7 connected to the local oscillator generator U1, an amplifier N2 connected to the other end of the capacitor C7, and a capacitor C6 having one end connected to the output end of the amplifier N2 and the other end connected to the local oscillator input end of the mixer N5.

[0010] Furthermore, in the present invention, the output filter amplifier circuit includes an amplifier N4 whose input end is connected to the other end of the capacitor C29, a filter N3 connected to the output end of the amplifier N4 via a capacitor C30, and an isolator N6 connected to the other end of the filter N3 via a capacitor C31.

[0011] Compared with the prior art, the utility model has the following beneficial effects:

[0012] The L-band receiving frequency conversion circuit of the utility model is mainly aimed at capturing certain mobile phone signals in a certain special area. It adopts two filterings, a better cavity filter is used for input, and a relatively unique LC filter is used for output. In this way, the output intermediate frequency filtering effect is better and provided to the collector in a relatively small band, so that the collected signal has a higher reliability value. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a circuit schematic diagram of the utility model. DETAILED DESCRIPTION

[0014] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The present invention includes but is not limited to the following embodiments.

[0015] Example

[0016] like Figure 1As shown, the utility model discloses an L-band receiving frequency conversion circuit, including a receiving antenna, a two-stage filtering and amplifying circuit connected to the receiving antenna, a mixing circuit connected to the two-stage filtering and amplifying circuit, a local oscillator generating circuit connected to the local oscillator input end of the mixing circuit, and an output amplifying and filtering circuit connected to the mixing circuit. The circuit uses the two-stage filtering and amplifying circuit to perform two-stage filtering and amplifying on the weak signal received by the receiving antenna, and after the amplified signal enters the mixing circuit, it is mixed with the local oscillator signal generated by the local oscillator generating circuit and then outputs an intermediate frequency signal; after the intermediate frequency signal is filtered, amplified and clutter suppressed, the signal is output to the collector, which meets the practical requirements of modulation and demodulation.

[0017] In this embodiment, the two-stage filtering and amplifying circuit includes a capacitor C1, a filter N1, a capacitor C2, an amplifier N12, a capacitor C3, an amplifier N13, a capacitor C4, a resistor R1 and a capacitor C5 which are sequentially connected to the receiving antenna, a resistor R2 having one end connected between the capacitor C4 and the resistor R1 and the other end grounded, and a resistor R3 having one end connected between the resistor R1 and the capacitor C5 and the other end grounded; wherein the other end of the capacitor C5 is connected to the mixing circuit.

[0018] In this embodiment, the mixing circuit includes a mixer N5 whose RF input is connected to the other end of the capacitor C5, a capacitor C28, a resistor R5 and a capacitor C29 connected to the intermediate frequency output end of the mixer N5 in sequence, a resistor R8 connected between the capacitor C28 and the resistor R5 and the other end of which is grounded, and a resistor R6 connected between the capacitor C29 and the resistor R5 and the other end of which is grounded; wherein the other end of the capacitor C29 is connected to the output amplification and filtering circuit.

[0019] In this embodiment, the local oscillator generating circuit includes a reference source N7, a capacitor C9 connected to the output end of the reference source N7, an amplifier N8 having an input end connected to the other end of the capacitor C9, a capacitor C8 connected to the output end of the amplifier N8, a local oscillator generator U1 connected to the other end of the capacitor C8, a capacitor C7 connected to the local oscillator generator U1, an amplifier N2 connected to the other end of the capacitor C7, and a capacitor C6 having one end connected to the output end of the amplifier N2 and the other end connected to the local oscillator input end of the mixer N5.

[0020] In this embodiment, the output filter amplifier circuit includes an amplifier N4 whose input end is connected to the other end of the capacitor C29, a filter N3 connected to the output end of the amplifier N4 via a capacitor C30, and an isolator N6 connected to the other end of the filter N3 via a capacitor C31.

[0021] In this embodiment, the weak signal coming in through the receiving antenna is filtered out of the useful signal through the filter N1. The filter retains the useful signal very well and effectively suppresses the out-of-band signal. The small signal is effectively amplified by the high-frequency low-noise tube N12. N12 captures the weak effective signal from the effective band and amplifies it. It has a certain suppression on the white noise signal. The signal is relatively weak and is effectively amplified again by N13. In this way, the amplified signal is convenient for collection. The overall gain of the two-stage amplifier is about 35, so the amplitude of the signal meets the requirements. N6 is the signal local oscillator source, and N7 generates a 100M reference signal for N6 makes N6 generate a local oscillator signal of 2062.5M. The amplitude of this signal is not enough, so it is effectively amplified to 13dBm through amplifier N2. In this way, the amplitude provided to mixer N5 is sufficient, so that N5 works smoothly and the mixer output is linearized. The signal output by amplifier N13 enters the mixer to output a 70M intermediate frequency signal. Mixer N5 has an attenuation of about 10dB on the useful signal. The signal is effectively amplified through N4, so that the 70M intermediate frequency signal is effectively amplified, and the clutter signal next to it is also effectively amplified and effectively filtered out through filter N3, so that the output signal is clean and meets the use of modulation and demodulation.

[0022] The above embodiment is only one of the preferred implementation modes of the present utility model and should not be used to limit the protection scope of the present utility model. Any changes or modifications that are made to the main design concept and spirit of the present utility model without any substantive significance, as long as the technical problems solved are still consistent with the present utility model, should be included in the protection scope of the present utility model.

Claims

1. An L-band receiving frequency conversion circuit, characterized in that: It includes a receiving antenna, a two-stage filter amplifier circuit connected to the receiving antenna, a mixing circuit connected to the two-stage filter amplifier circuit, a local oscillator generating circuit connected to the local oscillator input end of the mixing circuit, and an output amplifier filter circuit connected to the mixing circuit.

2. The L-band receiving frequency conversion circuit according to claim 1, characterized in that: The two-stage filtering and amplifying circuit includes a capacitor C1, a filter N1, a capacitor C2, an amplifier N12, a capacitor C3, an amplifier N13, a capacitor C4, a resistor R1 and a capacitor C5 which are sequentially connected to a receiving antenna, a resistor R2 having one end connected between the capacitor C4 and the resistor R1 and the other end connected to ground, and a resistor R3 having one end connected between the resistor R1 and the capacitor C5 and the other end connected to ground; wherein the other end of the capacitor C5 is connected to a mixing circuit.

3. The L-band receiving frequency conversion circuit according to claim 2, characterized in that: The mixing circuit includes a mixer N5 whose RF input is connected to the other end of the capacitor C5, a capacitor C28, a resistor R5 and a capacitor C29 which are connected to the intermediate frequency output end of the mixer N5 in sequence, a resistor R8 which is connected between the capacitor C28 and the resistor R5 and whose other end is grounded, and a resistor R6 which is connected between the capacitor C29 and the resistor R5 and whose other end is grounded; wherein the other end of the capacitor C29 is connected to the output amplification and filtering circuit.

4. The L-band receiving frequency conversion circuit according to claim 3, characterized in that: The local oscillator generating circuit includes a reference source N7, a capacitor C9 connected to the output end of the reference source N7, an amplifier N8 having an input end connected to the other end of the capacitor C9, a capacitor C8 connected to the output end of the amplifier N8, a local oscillator generator U1 connected to the other end of the capacitor C8, a capacitor C7 connected to the local oscillator generator U1, an amplifier N2 connected to the other end of the capacitor C7, and a capacitor C6 having one end connected to the output end of the amplifier N2 and the other end connected to the local oscillator input end of the mixer N5.

5. The L-band receiving frequency conversion circuit according to claim 4, characterized in that: The output filter amplifier circuit includes an amplifier N4 whose input end is connected to the other end of the capacitor C29, a filter N3 connected to the output end of the amplifier N4 via a capacitor C30, and an isolator N6 connected to the other end of the filter N3 via a capacitor C31.

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