An intermediate frequency signal generating circuit for portable communication and navigation tester

Abstract

The present invention relates to an intermediate frequency signal generating circuit for a portable communication and navigation tester in the field of electronic measuring instruments. The circuit includes: a radio frequency signal conditioning circuit, a radio frequency channel preselection filter circuit, and a mixing circuit; the radio frequency signal conditioning circuit converts a wide-band radio frequency signal input from the outside into a low-band signal or a high-band signal; the radio frequency channel preselection filter circuit performs preselection filtering and segmentation on the low-band signal and the high-band signal; the mixing circuit includes a first mixing circuit and a second mixing circuit, which performs mixing processing on the signal output by the radio frequency channel preselection filter circuit and outputs an intermediate frequency signal. The present invention can provide an intermediate frequency signal generating circuit for a portable communication and navigation tester, which generates the required two-stage intermediate frequency signal through frequency band preselection and mixing of two-stage local oscillator signals, and the generated intermediate frequency signal is stable and meets the requirements of the design indicators.

Description

Technical Field

[0001] The invention relates to the field of electronic measuring instruments, in particular to an intermediate frequency signal generating circuit for a portable communication and navigation tester. Background Art

[0002] On airplanes and ships, due to limited space, conventional communication signal testing and maintenance equipment cannot be used, and portable equipment is usually used to reduce the size of the detection equipment for practical use. However, under the premise of achieving the same technical indicators, the reduction of equipment size means that the indicators of the signal processing and acquisition components must be adjusted, and the implemented circuits need to be improved for portable applications.

[0003] Portable communication and navigation tester, to be used for communication and maintenance of aircraft, ships, etc., can measure VHF / UHF transmitter frequency, output power, modulation (AM and FM) and receiver sensitivity, measure HF transmitter frequency, output power, modulation (AM and SSB) and receiver sensitivity, generate ARINC 596 selective call signal, measure HF / VHF / UHF antenna and / or feeder standing wave ratio (SWR), and can set DDM to simulate localizer and glide path signals, scan positioning, for coupled automatic guidance test (simulate localizer, glide path and marker beacon signals at the same time). It can simulate VOR beacons in different directions, simulate marker beacon, outer marker and middle marker signals, and measure the frequency, output power and modulation (AM) of 121.5 / 243 MHz emergency beacon transmitter. Audio output is used to monitor the scan audio signal and measure the frequency and output power of 406MHz COSPAS / SARSAT emergency beacon transmitter. It can decode and display all positions and user protocols.

[0004] Figure 2 This is the overall design principle block diagram of the portable communication and navigation tester. The RF front-end unit needs to generate an intermediate frequency signal for signal processing. How to extract multiple intermediate frequency signals from the input RF signal is a difficult point in the design of the portable communication and navigation tester. Summary of the invention

[0005] Aiming at the demand for intermediate frequency signal generation in a portable communication and navigation tester, the present invention proposes an intermediate frequency signal generating circuit for the portable communication and navigation tester.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] An intermediate frequency signal generating circuit for a portable communication and navigation tester includes: a radio frequency signal conditioning circuit, a radio frequency channel preselection filtering circuit, and a mixing circuit.

[0008] The RF signal conditioning circuit receives a wide-band RF signal input from the outside, performs attenuation processing on the wide-band RF signal, and converts the wide-band RF signal into a low-band signal or a high-band signal, and the low-band signal or the high-band signal is output to the RF channel preselection filter circuit;

[0009] The RF channel pre-selection filter circuit receives the low frequency band signal or the high frequency band signal output by the RF signal conditioning circuit, performs pre-selection filtering on the low frequency band signal and the high frequency band signal, and outputs a first pre-selection filtering low frequency band signal, a second pre-selection filtering low frequency band signal and a pre-selection filtering high frequency band signal to the mixing circuit respectively;

[0010] The mixing circuit includes a first mixing circuit and a second mixing circuit. The mixing circuit receives the first pre-selected filtered low-frequency band signal, the second pre-selected filtered low-frequency band signal and the pre-selected filtered high-frequency band signal output by the RF channel pre-selected filtering circuit, and performs mixing processing through the first mixing circuit and the second mixing circuit in sequence to output an intermediate frequency signal.

[0011] As a preferred solution, the center frequency of the intermediate frequency signal is 76.8 MHz or 70 MHz.

[0012] As a preferred solution, the first frequency mixing circuit includes a first local oscillator signal generating circuit, a segmented frequency mixing circuit, and a three-way intermediate frequency signal generating circuit.

[0013] The first local oscillator signal generating circuit includes a first local oscillator signal synthesis chip and its peripheral circuits, which are used to synthesize the crystal oscillator reference signal input from the outside into the first local oscillator signal and the second local oscillator signal. The first local oscillator signal is input into the segmented mixing circuit to mix the first pre-selected filtered low-frequency band signal and the pre-selected filtered high-frequency band signal. The second local oscillator signal is input into the segmented mixing circuit to mix the second pre-selected filtered low-frequency band signal.

[0014] The segmented mixing circuit includes a first mixer, a second mixer and a first radio frequency switch.

[0015] The first mixer receives the first pre-selected filtered low frequency band, the pre-selected filtered high frequency band signal and the first local oscillator signal, and is used to mix the first pre-selected filtered low frequency band and the pre-selected filtered high frequency band signal, and output a first mixed signal to the first RF switch;

[0016] The second mixer receives a second pre-selected filtered low frequency band and the second local oscillator signal, and is used to perform mixing processing on the pre-selected second pre-selected filtered low frequency band, and output a second mixed signal to the first RF switch;

[0017] The first RF switch inputs the first mixing signal and the second mixing signal, and outputs the first mixing signal or the second mixing signal to the three-channel intermediate frequency signal generating circuit;

[0018] The three-way intermediate frequency signal generating circuit inputs the first mixing signal or the second mixing signal output by the radio frequency switch to generate a first intermediate frequency filter signal, a second intermediate frequency filter signal and a third intermediate frequency filter signal. The first intermediate frequency filter signal, the second intermediate frequency filter signal and the third intermediate frequency filter signal are switched by the second radio frequency switch, and one of them is output to the second mixing circuit.

[0019] As a preferred solution, the frequency range of the second mixing signal is 20 MHz to 2100 MHz, and the frequency range of the first mixing signal is 2.1 GHz to 8 GHz.

[0020] As a preferred solution, the frequency of the crystal oscillator reference signal is 102.4 MHz, and correspondingly, the frequency of the first local oscillator signal is 1635 MHz, and the frequency of the second local oscillator signal is 5345 MHz.

[0021] As a preferred solution, the frequency of the first intermediate frequency filter signal is 2655 MHz, the frequency of the second intermediate frequency filter signal is 2140 MHz, and the frequency of the third intermediate frequency filter signal is 1583 MHz.

[0022] As a preferred solution, the second mixer circuit includes a signal attenuation circuit, a second local oscillator signal generating circuit, a third mixer and a peripheral circuit of the third mixer.

[0023] The signal attenuation circuit inputs the intermediate frequency filter signal output by the first mixer circuit, performs frequency response conditioning on the intermediate frequency filter signal output by the first mixer circuit, and outputs the conditioned intermediate frequency conditioned filter signal to the third mixer;

[0024] The second local oscillator signal generating circuit includes a second local oscillator signal synthesis chip and its peripheral circuits, which are used to convert an externally input crystal oscillator reference signal into a third local oscillator signal, and the third local oscillator signal is input into the third mixer to mix the intermediate frequency conditioning and filtering signal;

[0025] The third mixer inputs the intermediate frequency conditioned and filtered signal and the third local oscillator signal, performs mixing processing on the intermediate frequency conditioned and filtered signal, and outputs the intermediate frequency signal.

[0026] As a preferred solution, the radio frequency channel preselection filter circuit includes a radio frequency switching input circuit, a low frequency band preselection circuit and a high frequency band preselection circuit;

[0027] The RF switching input circuit receives the low frequency band signal or the high frequency band signal output by the RF signal conditioning circuit, outputs the low frequency band signal to the low frequency band preselection circuit, and outputs the high frequency band signal to the high frequency band preselection circuit;

[0028] The high frequency band preselection circuit comprises a preselection first RF switch, a preselection second RF switch and a preselection third RF switch, and the high frequency band signal input into the high frequency band preselection circuit passes through the preselection first RF switch, the preselection second RF switch and the preselection third RF switch in sequence, and outputs the preselection filtered high frequency band signal;

[0029] The low-frequency band preselection circuit includes a preselection radio frequency switch group. The high-frequency band signal input into the high-frequency band preselection circuit passes through the preselection radio frequency switch group to output the preselection filtered low-frequency band signal.

[0030] As a preferred solution, the pre-selection filtering high-frequency band signal includes two pre-selection filtering segments; the pre-selection filtering low-frequency band signal includes eight pre-selection filtering segments.

[0031] As a preferred solution, the preselected RF switch group consists of the preselected third RF switch, the preselected fourth RF switch, the preselected fifth RF switch, the preselected sixth RF switch, the preselected seventh RF switch, and the preselected eighth RF switch.

[0032] The preselected fourth RF switch inputs the low frequency band signal output by the RF switching input circuit, outputs the first branch low frequency signal to the preselected fifth RF switch, and outputs the second branch low frequency signal to the preselected sixth RF switch;

[0033] The preselected fifth RF switch receives the first branch low-frequency signal output by the preselected fourth RF switch, outputs the third branch low-frequency signal and the fourth branch low-frequency signal to the preselected third RF switch, and outputs the fifth branch low-frequency signal and the sixth branch low-frequency signal to the preselected eighth RF switch;

[0034] The preselected sixth RF switch receives the second branch low-frequency signal output by the preselected fourth RF switch, and outputs the seventh branch low-frequency signal, the eighth branch low-frequency signal, the ninth branch low-frequency signal, and the tenth branch low-frequency signal to the preselected seventh RF switch; the seventh branch low-frequency signal, the eighth branch low-frequency signal, the ninth branch low-frequency signal, and the tenth branch low-frequency signal are switched by the preselected seventh RF switch, and one of them is output to the preselected eighth RF switch.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention can provide an intermediate frequency signal generating circuit for a portable communication and navigation tester, which generates required two-level intermediate frequency signals through frequency band preselection and mixing of two-level local oscillator signals. The generated intermediate frequency signals are stable and meet the requirements of design indicators. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a block diagram of the principle of an intermediate frequency signal generating circuit for a portable communication and navigation tester;

[0038] Figure 2 This is the overall design principle block diagram of the portable communication and navigation tester;

[0039] Figure 3 is a principle block diagram of the first frequency mixing circuit in Embodiment 1 of the present invention;

[0040] Figure 4 is a principle block diagram of the second frequency mixing circuit in Embodiment 1 of the present invention;

[0041] Figure 5 This is a principle block diagram of a radio frequency channel preselection filter circuit in Embodiment 1 of the present invention;

[0042] Figure 6 is a circuit schematic diagram of a radio frequency signal conditioning circuit in Embodiment 2 of the present invention;

[0043] Figure 7 This is a schematic diagram of a radio frequency switching input circuit of a radio frequency channel preselection filter circuit in Embodiment 2 of the present invention;

[0044] Figure 8 It is a schematic diagram of a low frequency band preselection circuit of a radio frequency channel preselection filter circuit in Embodiment 2 of the present invention;

[0045] Fig. 9 It is a high frequency band preselection circuit of the radio frequency channel preselection filter circuit in embodiment 2 of the present invention;

[0046] Fig.10 is a schematic diagram of a segmented frequency mixing circuit of the first frequency mixing circuit in Embodiment 2 of the present invention;

[0047] Fig.11 4 is a schematic diagram of a three-way intermediate frequency signal generating circuit of the first mixing circuit in Embodiment 2 of the present invention;

[0048] Fig.12 4 is a schematic diagram of a first local oscillation signal generating circuit of a first frequency mixing circuit in Embodiment 2 of the present invention;

[0049] Fig.13 is a schematic diagram of a second frequency mixing circuit in Embodiment 2 of the present invention;

[0050] Fig.14This is a schematic diagram of a second local oscillation signal generating circuit in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0051] The present invention is further described in detail below in conjunction with test examples and specific implementation methods. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0052] Example 1

[0053] An intermediate frequency signal generating circuit for a portable communication and navigation tester mainly includes: a radio frequency signal conditioning circuit, a radio frequency channel preselection filter circuit and a mixing circuit, wherein the mixing circuit includes a first mixing circuit and a second mixing circuit. The circuit principle block diagram is shown in FIG. Figure 1 shown.

[0054] The RF signal conditioning circuit receives wide-band RF signals input from the outside. The frequency range of wide-band RF signals used in portable communication and navigation testers is usually 20~8000MHz. The RF signal conditioning circuit performs signal attenuation processing on the input 20~8000MHz wide-band RF signals, and divides the input signals into a low frequency band of 20~3800MHz and a high frequency band of 3.8GHz~8GHz through a high-frequency electronic switch.

[0055] The RF channel pre-selection filter circuit receives low-frequency signals of 20 to 3800MHz and high-frequency signals of 3.8GHz to 8GHz, performs pre-selection filtering on the low-frequency signals of 20 to 3800MHz and divides them into eight pre-selection frequency segments, and performs pre-selection filtering on the high-frequency signals of 3.8GHz to 8GHz and divides them into two pre-selection filtering segments, and outputs the first pre-selection filtering low-frequency band signal, the second pre-selection filtering low-frequency band signal and the pre-selection filtering high-frequency band signal to the mixing circuit respectively. The principle block diagram of the RF channel pre-selection filter circuit is shown in the figure. Figure 5 shown.

[0056] The mixing circuit includes a first mixing circuit and a second mixing circuit. The mixing circuit receives the first pre-selection filtering low frequency band signal, the second pre-selection filtering low frequency band signal and the pre-selection filtering high frequency band signal output by the RF channel pre-selection filtering circuit, and performs mixing processing through the first mixing circuit and the second mixing circuit in sequence to output an intermediate frequency signal. The center frequency of the output intermediate frequency signal is 76.8MHz or 70MHz.

[0057] As a preferred solution, the first frequency mixing circuit includes a first local oscillator signal generating circuit, a segmented frequency mixing circuit, and a three-way intermediate frequency signal generating circuit. The principle block diagram of the first frequency mixing circuit is shown in FIG. Figure 3 shown.

[0058] The first local oscillator signal generating circuit includes a first local oscillator signal synthesis chip and its peripheral circuits, which are used to synthesize the crystal oscillator reference signal input from the outside into a first local oscillator signal (with a center frequency value of 5345MHz) and a second local oscillator signal (with a center frequency value of 1635MHz). The first local oscillator signal is input into the segmented mixing circuit to mix the first pre-selected filtered low-frequency band signal and the pre-selected filtered high-frequency band signal. The second local oscillator signal is input into the segmented mixing circuit to mix the second pre-selected filtered low-frequency band signal.

[0059] After the first pre-selection filter low frequency band signal, the second pre-selection filter low frequency band signal and the pre-selection filter high frequency band signal output by the RF channel pre-selection filter circuit are input into the segmented mixing circuit, the first pre-selection filter low frequency band signal, the pre-selection filter high frequency band signal and the first local oscillator signal are mixed to output the first mixed signal. The second pre-selection filter low frequency band signal is mixed with the second local oscillator signal to output the second mixed signal.

[0060] The three-way intermediate frequency signal generating circuit inputs the first mixing signal or the second mixing signal to generate a first intermediate frequency filter signal (with a center frequency value of 2655MHz), a second intermediate frequency filter signal (with a center frequency value of 2140MHz) and a third intermediate frequency filter signal (with a center frequency value of 1583MHz). The first intermediate frequency filter signal, the second intermediate frequency filter signal and the third intermediate frequency filter signal are switched by the second radio frequency switch, and one of them is output to the second mixing circuit.

[0061] The second frequency mixing circuit includes a signal attenuation circuit, a second local oscillation signal generating circuit, a third frequency mixer and a peripheral circuit of the third frequency mixer. The principle block diagram of the second frequency mixing circuit is shown in FIG. Figure 4 shown.

[0062] The signal attenuation circuit inputs the intermediate frequency filter signal output by the first mixer circuit, performs frequency response conditioning on the intermediate frequency filter signal output by the first mixer circuit, and outputs the conditioned intermediate frequency conditioned filter signal to the third mixer.

[0063] The second local oscillator signal generating circuit includes a second local oscillator signal synthesis chip and its peripheral circuits, which are used to convert the externally input crystal oscillator reference signal into a third local oscillator signal. The third local oscillator signal is input into a third mixer for mixing the intermediate frequency conditioning and filtering signal.

[0064] The third mixer inputs the intermediate frequency conditioning and filtering signal and the third local oscillator signal, mixes the intermediate frequency conditioning and filtering signal, and outputs an intermediate frequency signal. After mixing, the intermediate frequency signal frequency is 76.8MHz (wideband) or 70MHz (narrowband).

[0065] Example 2

[0066] Embodiment 2 is based on Embodiment 1 and provides a specific circuit schematic diagram of each block diagram.

[0067] The RF signal is input to the RF signal conditioning circuit, and first passes through a 30dB adjustable RF attenuator (D3) to attenuate the signal (the attenuator step is 1dB), and then outputs the low-frequency band signal and the high-frequency band signal to the RF channel pre-selection filter circuit through two high-frequency electronic switches D1 and D2. The circuit schematic diagram of the RF signal conditioning circuit is shown in the figure. Figure 6 shown.

[0068] The RF channel preselection filter circuit switches the input low-frequency band signal and high-frequency band signal into three-way mode selection (low distortion, normal and low noise mode) through the RF switching input circuit. The RF switching input circuit is as follows Figure 7 shown.

[0069] The high-frequency band signal is divided into two pre-selection filter segments (the first branch high-frequency signal and the second branch high-frequency signal) through D9 (HMC349AMS8G), D4 (RF switch PE42553), and D7 in turn; the low-frequency band signal is output through the pre-selection RF switch group to 8 pre-selection filter segments. The schematic diagram of the high-frequency band pre-selection circuit is as follows Fig. 9 shown.

[0070] The preselected RF switch group consists of a first low-frequency preselected channel and a second low-frequency preselected channel. The schematic diagram of the low-frequency band preselected circuit is shown in Figure 8 As shown. The low-frequency band signal passes through D12, D10 and D7 in the first low-frequency preselection channel in turn to output the third branch low-frequency signal and the fourth branch low-frequency signal; the low-frequency band signal passes through D12, D10 and D11 in the second low-frequency preselection channel in turn to output two low-frequency signals (the fifth branch low-frequency signal and the sixth branch low-frequency signal); the low-frequency band signal passes through D12 and D5 in the second low-frequency preselection channel in turn to output four low-frequency signals (the seventh branch low-frequency signal, the eighth branch low-frequency signal, the ninth branch low-frequency signal and the tenth branch low-frequency signal), and these four low-frequency signals are output in turn through D6 and D11. The preselection filter group includes 180MHz low pass, 120~360MHz, 300~620MHz, 520~1220MHz, 1180~1720MHz, 1680~2120MHz, 2080~3300MHz, 3000~3830MHz and 3700~6030MHz.

[0071] The ten pre-selected frequencies are output to the segmented mixer circuit of the first mixer circuit through two channels. The schematic diagram of the segmented mixer circuit of the first mixer circuit is as follows: Fig.10As shown in the figure, the 20-2100MHz signal is mixed with the second local oscillator signal (center frequency value is 1635MHz) through the mixer N9; the 2.1GHz-8GHz signal is mixed with the first local oscillator signal (center frequency value is 5345MHz) through the mixer N8.

[0072] The first local oscillator signal and the second local oscillator signal are generated by a first local oscillator signal generating circuit. The schematic diagram of the first local oscillator signal generating circuit is shown in FIG. Fig.12 The 102.4MHz crystal oscillator reference signal passes through the N25 (lmx2572) synthesis chip and D23 in turn, outputting the first local oscillator signal (center frequency value is 5345MHz) and the second local oscillator signal (center frequency value is 1635MHz).

[0073] The mixed signal is output to the input end of the three-way intermediate frequency signal generating circuit. The schematic diagram of the three-way intermediate frequency signal generating circuit is as follows Fig.11 As shown. The three-way intermediate frequency signal generating circuit generates three-way intermediate frequency filter signals, which are the first intermediate frequency filter signal frequency (2655MHz), the second intermediate frequency filter signal frequency (2140MHz), and the third intermediate frequency filter signal frequency (1583MHz). These three signals are output to the input end of the second mixer circuit through D16.

[0074] The schematic diagram of the second mixer circuit is as follows: Fig.13 The three signals are adjusted in frequency response by D18 electronic attenuator, and then mixed for the second time by N21 (IDT-F1792 mixer) (mixer gain is about 10dB) to output intermediate frequency signal 76.8MHz (wideband) or 70MHz (narrowband).

[0075] When the IDT-F1792 mixer performs a second mixing on the input intermediate frequency filter signal, a third local oscillator signal is used. The third local oscillator signal is output by the second local oscillator signal generating circuit. The schematic diagram of the second local oscillator signal generating circuit is shown in FIG. Fig.14 The second local oscillator signal is obtained by converting the input 102.4 MHz crystal oscillator reference signal by the second local oscillator signal generating circuit.

Claims

1. An intermediate frequency signal generating circuit for a portable communication and navigation tester, characterized in that: include: RF signal conditioning circuit, RF channel pre-selection filter circuit, mixing circuit, The RF signal conditioning circuit receives a wide-band RF signal input from the outside, performs attenuation processing on the wide-band RF signal, and converts the wide-band RF signal into a low-band signal or a high-band signal, and the low-band signal or the high-band signal is output to the RF channel preselection filter circuit; The RF channel pre-selection filter circuit receives the low frequency band signal or the high frequency band signal output by the RF signal conditioning circuit, performs pre-selection filtering on the low frequency band signal and the high frequency band signal, and outputs a first pre-selection filtering low frequency band signal, a second pre-selection filtering low frequency band signal and a pre-selection filtering high frequency band signal to the mixing circuit respectively; The mixing circuit comprises a first mixing circuit and a second mixing circuit, wherein the mixing circuit receives the first pre-selection filtering low-frequency band signal, the second pre-selection filtering low-frequency band signal and the pre-selection filtering high-frequency band signal output by the RF channel pre-selection filtering circuit, and performs mixing processing through the first mixing circuit and the second mixing circuit in sequence, and outputs an intermediate frequency signal; The first frequency mixing circuit includes a first local oscillator signal generating circuit, a segmented frequency mixing circuit, and a three-way intermediate frequency signal generating circuit. The first local oscillator signal generating circuit includes a first local oscillator signal synthesis chip and its peripheral circuits, which are used to synthesize the crystal oscillator reference signal input from the outside into the first local oscillator signal and the second local oscillator signal. The first local oscillator signal is input into the segmented mixing circuit to mix the first pre-selected filtered low-frequency band signal and the pre-selected filtered high-frequency band signal. The second local oscillator signal is input into the segmented mixing circuit to mix the second pre-selected filtered low-frequency band signal. The segmented mixing circuit includes a first mixer, a second mixer and a first radio frequency switch. The first mixer receives the first pre-selected filtered low frequency band, the pre-selected filtered high frequency band signal and the first local oscillator signal, and is used to mix the first pre-selected filtered low frequency band and the pre-selected filtered high frequency band signal, and output a first mixed signal to the first RF switch; The second mixer receives a second pre-selected filtered low frequency band and the second local oscillator signal, and is used to perform mixing processing on the pre-selected second pre-selected filtered low frequency band, and output a second mixed signal to the first RF switch; The first RF switch inputs the first mixing signal and the second mixing signal, and outputs the first mixing signal or the second mixing signal to the three-channel intermediate frequency signal generating circuit; The three-way intermediate frequency signal generating circuit inputs the first mixing signal or the second mixing signal output by the radio frequency switch to generate a first intermediate frequency filter signal, a second intermediate frequency filter signal and a third intermediate frequency filter signal. The first intermediate frequency filter signal, the second intermediate frequency filter signal and the third intermediate frequency filter signal are switched by the second radio frequency switch, and one of them is output to the second mixing circuit.

2. The intermediate frequency signal generating circuit for a portable communication and navigation tester as claimed in claim 1, characterized in that: The center frequency of the intermediate frequency signal is 76.8 MHz or 70 MHz.

3. The intermediate frequency signal generating circuit for a portable communication and navigation tester as claimed in claim 1, characterized in that: The frequency range of the second mixing signal is 20 MHz to 2100 MHz, and the frequency range of the first mixing signal is 2.1 GHz to 8 GHz.

4. The intermediate frequency signal generating circuit for a portable communication and navigation tester as claimed in claim 1, characterized in that: The frequency of the crystal oscillator reference signal is 102.4 MHz, and correspondingly, the frequency of the first local oscillator signal is 1635 MHz, and the frequency of the second local oscillator signal is 5345 MHz.

5. The intermediate frequency signal generating circuit for a portable communication and navigation tester as claimed in claim 1, characterized in that: The frequency of the first intermediate frequency filter signal is 2655 MHz, the frequency of the second intermediate frequency filter signal is 2140 MHz, and the frequency of the third intermediate frequency filter signal is 1583 MHz.

6. The intermediate frequency signal generating circuit for a portable communication and navigation tester as claimed in claim 1, characterized in that: The second frequency mixing circuit includes a signal attenuation circuit, a second local oscillation signal generating circuit, a third frequency mixer and a peripheral circuit of the third frequency mixer. The signal attenuation circuit inputs the intermediate frequency filter signal output by the first mixer circuit, performs frequency response conditioning on the intermediate frequency filter signal output by the first mixer circuit, and outputs the conditioned intermediate frequency conditioned filter signal to the third mixer; The second local oscillator signal generating circuit includes a second local oscillator signal synthesis chip and its peripheral circuits, which are used to convert an externally input crystal oscillator reference signal into a third local oscillator signal, and the third local oscillator signal is input into the third mixer to mix the intermediate frequency conditioning and filtering signal; The third mixer inputs the intermediate frequency conditioned and filtered signal and the third local oscillator signal, performs mixing processing on the intermediate frequency conditioned and filtered signal, and outputs the intermediate frequency signal.

7. The intermediate frequency signal generating circuit for a portable communication and navigation tester as claimed in claim 1, characterized in that: The radio frequency channel preselection filter circuit includes a radio frequency switching input circuit, a low frequency band preselection circuit and a high frequency band preselection circuit; The RF switching input circuit receives the low frequency band signal or the high frequency band signal output by the RF signal conditioning circuit, outputs the low frequency band signal to the low frequency band preselection circuit, and outputs the high frequency band signal to the high frequency band preselection circuit; The high-frequency band preselection circuit comprises a preselected first RF switch, a preselected second RF switch and a preselected third RF switch, and the high-frequency band signal input into the high-frequency band preselection circuit passes through the preselected first RF switch, the preselected second RF switch and the preselected third RF switch in sequence, and outputs the preselected filtered high-frequency band signal; The low frequency band preselection circuit includes a preselection RF switch group. The high frequency band signal input into the high frequency band preselection circuit passes through the preselection RF switch group to output the preselection filtered low frequency band signal.

8. The intermediate frequency signal generating circuit for a portable communication and navigation tester as claimed in claim 7, characterized in that: The pre-selected and filtered high-frequency band signal includes two pre-selected and filtered segments; the pre-selected and filtered low-frequency band signal includes eight pre-selected and filtered segments.

9. The intermediate frequency signal generating circuit for a portable communication and navigation tester as claimed in claim 8, characterized in that: The preselected RF switch group is composed of the preselected third RF switch, the preselected fourth RF switch, the preselected fifth RF switch, the preselected sixth RF switch, the preselected seventh RF switch, and the preselected eighth RF switch. The preselected fourth RF switch inputs the low frequency band signal output by the RF switching input circuit, outputs the first branch low frequency signal to the preselected fifth RF switch, and outputs the second branch low frequency signal to the preselected sixth RF switch; The preselected fifth RF switch receives the first branch low-frequency signal output by the preselected fourth RF switch, outputs the third branch low-frequency signal and the fourth branch low-frequency signal to the preselected third RF switch, and outputs the fifth branch low-frequency signal and the sixth branch low-frequency signal to the preselected eighth RF switch; The preselected sixth RF switch receives the second branch low-frequency signal output by the preselected fourth RF switch, and outputs the seventh branch low-frequency signal, the eighth branch low-frequency signal, the ninth branch low-frequency signal, and the tenth branch low-frequency signal to the preselected seventh RF switch; the seventh branch low-frequency signal, the eighth branch low-frequency signal, the ninth branch low-frequency signal, and the tenth branch low-frequency signal are switched by the preselected seventh RF switch, and one of them is output to the preselected eighth RF switch.

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