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The filter of microwave-high frequency PCB manufacturer is one of the essential key components in the radio frequency system. It is mainly used for high-frequency selection ---- to let the required frequency signal pass through and reflect the unnecessary interference frequency signal.A practical example of a classic filter application is the front end of a confiscator or transmitter, as shown in Figure 1 :
As can be seen from Figure 1, filters are widely used in the rf, IF, and baseband parts of the capture machine. Although it is considered appropriate to use digital filters to replace the baseband local or even if local analog filters, but the rf local filters still can not be replaced. Because of this, the filter is one of the essential key components in the rf system. Filters can be classified in some ways. Such as: Special properties selected by high-frequency PCB can be divided into the low pass, high pass, bandpass, bandstop filter, etc. According to the successful implementation form, it can be divided into LC filter, acoustic surface wave/volume induced hearing vibration wave filter, spiral filter, media filter, body cavity filter, high-temperature superconducting filter, the simplest surface structure filter. The following first describes the special properties and effects of the high, low pass, bandpass, and bandstop frequency responses classified by specific properties selected by frequency.
Butterworth Chebyshev high pass filter
The most commonly used filters are low pass and bandpass. Low pass is widely used in local image restriction of the mixer and local harmonic restriction of high-frequency PCB source. Bandpass is widely used in the front-end signal selection of confiscator, spurious restriction after transmitter amplifier, and spurious restriction of frequency source. Order (series): For high-pass and low-pass filters, the order is the total number of capacitance and inductance of the filter. For a bandpass filter, the order is the total number of parallel resonators; For a band-stop filter, the order is the total number of serial and parallel resonators. Full bandwidth/relative bandwidth: This index is generally used in bandpass filters to represent the frequency range of signals that can pass through the filter and show the frequency selection of the filter. Relative bandwidth is the percentage of full bandwidth to core frequency.
Fifth order high pass filter
Cutoff frequency: The cutoff frequency is generally used for high-pass and low-pass filters. For the low-pass filter, the cut-off represents the frequency range through which the filter cannot pass; For a high-pass filter, the cutoff frequency represents the frequency range over which the filter's lowest capability passes. Standing wave: the S11 measured by the vector network, which expresses the matching degree of the filter port impedance to the desired impedance of the system. Some of the input signals expressed do not enter the filter and are reflected in the input.
Phase identical: the difference of transmission signal phase between the same index and different filters in the same batch. Characterizes the difference between batch filters (identical).
Amplitude identical: the difference of transmission signal loss between the same index and the same batch of different filters. Characterizes the difference between batch filters (identical).
Phase linearity: the phase difference between the phase in the high-frequency PCB range of the filter's passband and a transmission line with the same core frequency delay. Characterizes the special properties of the dispersion light of the filter.
Complete group delay: the time it takes for the signal to travel from the input port to the output port within the filter passband.
Phase identical: the difference of transmission signal phase between the same index and different filters in the same batch. Characterizes the difference between batch filters (identical).
Amplitude identical: the difference of microwave-high frequency PCB transmission signal loss between the same index and the same batch of different filters. Characterizes the difference between batch filters (identical).
