C-Band Cavity Filter
Of all the cavity filters that AWG Tech supplies, the C-Band cavity filter is probably the most prolific filters as they are widely used in satellite communications.
The C-band cavity filter is used to reject the transmitted signal in a C-band VSAT (Very Small Aperture Terminal). VSATs operate in a full duplex mode using frequency diversity. This means that the power amplifier and the LNA of the VSAT equipment is turned on at all times, and the terminal is receiving signals and transmitting signals to the same antenna at the same time. In order to do that, the transmit signal and the receive signals are operating at different frequencies.
For example, in a typical C-Band Satellite transceiver, the receiver is operating at 3.625 – 4.2 GHz whereas the transmitter is operating at 5.85-6.425 GHz. In such a system, the C-Band cavity filter play a very important role in ensuring that the transmitted signal do not couple into the receiver and saturate the receiver. This kind of filter is also known as a Tx reject filter. Since the power amplifier would be transmitting at very high power levels like 4W, a Tx reject filter needs to have a rejection of about 90dB at the Tx frequency typically. Because the filter is required to be able to handle how power levels, and need to be as low loss as possible, cavity filters or waveguide filters are always used in Tx-reject filter.
A typical specification for a C-Band Tx-Reject Cavity Filter
The ABPF-3912M3BW573M-01 is a C-Band cavity filter that is specially designed as a C-Band Tx-reject filter. It has a passband frequency of 3.625GHz to 4.2 GHz. The insertion loss in the passband is less than 0.5dB. It has an 70 dB stopband attenuation at 5.85-6.425 GHz.
C-Band Cavity Filter for other applications
The use of C-Band Cavity Filter is not restricted to satellite communication systems alone. C-Band Cavity Filter is also used in many other communication systems. AWG Tech supplies a wide variety of C-band Cavity filters that are used in other C-Band applications like digital radio transceivers or C-band radar.
Contact us to get a full catalog of our standard products. Alternatively, fill in the enquiry form below to get a custom designed C-band filter that is tailored to your requirements. There are no NRE charges or ITAR control for our filters.
| Part Number | Center Frequency | Passband Frequency | Insertion Loss | Rejection |
|---|---|---|---|---|
| ABF-3912M5BW575-01 | 3912.5 MHz | 3625 – 4200 MHz | 0.5 dB | >70 dB @5.850 – 6.425 GHz |
| ABPF-6137M5BW575-01 | 6137.5 MHz | 5850 – 6425 MHz | 0.5 dB | >70dB @3.625 – 4.200 GHz |
| ABPF-3800MBW800-01 | 3800 MHz | 3400 – 4200 MHz | 0.5 dB | >70dB @ 5.15 – 8GHz |
| ABPF-3950MBW500-01 | 3950 MHz | 3700 – 4200 MHz | 0.5 dB | > 60 dB @ dc – 3.2GHz >60 dB @ 4.8 GHz |
| ABPF-5650MBW500-01 | 5650 MHz | 5400 – 5900 MHz | 1.5 dB | > 60 dB @ dc – 4.8GHz >60 dB @ 6.5 – 18GHz |
C-Band Cavity Filter: Why They’re Tough, & Effective
If you read about communications or frequencies, do you hear stuff like the L, K, W or C (or whatever) bands? According to the IEEE, or Institute of Electronics & Electrical Engineers, the L, K, W or C-bands are a few of many bands in the radio, or electromagnetic spectrum. The C-band has frequencies ranging from 4.0 to 8.0 gigahertz (GHz) and it was the first frequency band to be allocated for use by telecommunications satellites, using the frequencies 3.7–4.2 GHz for downlinks, and 5.8–6.4 GHz for uplinks. Here’s a peek at the capabilities of C-band cavity filters, which are hailed as tough workhorses in the busy, and bustling C-band range.
Do Filters Have Cavities?
When the term C-Band “cavity filters” is mentioned in books, or online, perhaps many those who barely know electronics and communications, will think that filters have crooked, or broken teeth!
Well, cavity filters are not exactly like the cavities on human teeth, but they’re hailed as the basic forms of circuitry behind a Duplexer, and are described as “sharply-tuned resonant circuits which allow only certain frequencies to pass”.
The Main Functions Of Cavity Filters
Cavity filters perform two main sets of functions. For starters, these are built to pass the desired frequency, and second they reject as much of the undesired or unwanted frequencies as possible.
In terms of construction, cavities are also grouped or lumped in series with each other, in order to increase or enhance filter effectiveness, by making the pass band deeper, with regard to the surrounding frequencies.
This development has proven to be useful in ham repeaters, especially when they are located very close to each other, or to other spectrum users whose unwanted signals or frequencies often interfere with the ham equipment.
C-Band Cavity Filters Provide High Performance
Cavity filters for the busy, and highly profitable, are known for offering low insertion loss and higher power-handling capabilities. Some C-band cavity filters are also designed with a reduced number of sections, thus making them smaller, but have a lower passband, and lower overall costs.
Some filters provide pass-band delay equalization, or increased attenuation over a specific stopband region. Overall, C-band filters with a cavity provide optimum Q performance, which makes them ideal for military and commercial applications where narrow bandwidth and ruggedness are considered very crucial parameters.
Uses of C-Band Cavity Filter
The C-band is essentially utilized for satellite communications, most especially for applications that don’t require high “throughput” or data rates. They’re valuable in locations where it rains a lot, of where humidity levels are high, because atmospheric attenuation is a major headache as one moves higher to much higher frequency bands like the Ku or Ka.
However, the C-band is also a mainstay in banks, especially in automated teller machines (ATM) that use VSAT’s to communicate or relay data with the bank’s network, so that depositors and other customers will get their money safely, and securely. Thank god for C-Band cavity filters!