RF Utilities
Combine transmitter leakage and receiver selectivity into the ACIR, work out the carrier-to-interference ratio at a victim receiver, and find the ACIR or guard band a protection ratio needs.
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When two radio systems sit on adjacent channels, whether two operators at a shared site or two carriers in a tight channel plan, they interfere even though they are on different frequencies. Two imperfections combine to cause it. The transmitter leaks some power into the adjacent channel, measured by its Adjacent Channel Leakage Ratio (ACLR). The receiver cannot perfectly reject the adjacent channel, measured by its Adjacent Channel Selectivity (ACS). Together they set the Adjacent Channel Interference Ratio (ACIR), the single figure that governs how much an adjacent transmitter degrades a victim receiver.
The two combine as reciprocals, the way parallel resistances do: 1/ACIR = 1/ACLR + 1/ACS. Because of that, the ACIR is always a little worse than the poorer of the two, and once one is more than about 10 dB better than the other, the poorer one sets the result almost entirely. Cleaning up a transmitter buys nothing if the receiver is the limit, and vice versa. Getting this right is the difference between a coordination that works and one that does not.
The noIM3 Adjacent Channel Interference Ratio Calculator is built for the systems integrator doing that coordination, not the chipset designer. Combine an ACLR and an ACS into the ACIR and see which term limits it. Take the wanted and interferer levels at a victim receiver and get the carrier-to-interference ratio and the margin against a protection ratio. Or start from the protection ratio the victim needs and get the ACIR required, with the shortfall against the ACLR and ACS you actually have, so you know how much filtering or guard band to add.
Enter the transmitter leakage ratio and the receiver selectivity and get the combined ACIR, with the term that limits it called out and the penalty it pays below that term. Solve for any of the three given the other two.
Enter the wanted signal and the adjacent interferer levels at the victim receiver, plus the ACIR, and get the interference power after ACIR, the resulting carrier-to-interference ratio, and a pass or fail margin against a protection ratio.
Start from the protection ratio the victim needs and get the ACIR required to meet it, along with the shortfall against your available ACLR and ACS, so you know how many dB of extra filtering or guard band to find.
Because ACLR and ACS add as reciprocals, one usually dominates. The tool identifies the limiting term and shows how little improving the other one would buy, so effort goes where it actually helps.
Every mode plots the relationship with the operating point marked: ACIR against ACLR saturating at the ACS ceiling, carrier-to-interference against ACIR with the protection line, and the required ACIR against the protection ratio with the available ACIR overlaid.
Runs entirely in your browser. No coordination data is submitted to a server. Useful for commercially confidential work or any environment where information security policy prohibits sending engineering data to third party services.
Reach for the Adjacent Channel Interference Ratio Calculator in any of the following situations.
ACIR is the ratio of the power transmitted on one channel to the interference it causes in an adjacent channel, taking both the transmitter and the receiver into account. It combines the transmitter Adjacent Channel Leakage Ratio (ACLR) and the receiver Adjacent Channel Selectivity (ACS). All three are wanted-to-leakage ratios in dB, so a higher number is better.
They add as reciprocals of the linear ratios: 1/ACIR = 1/ACLR + 1/ACS. Convert each dB figure to a linear ratio, add the reciprocals, invert, and convert back to dB. Because of the reciprocal sum, the ACIR is always a little worse than the poorer of the two, and when they are equal the ACIR is exactly 3.01 dB below both.
ACLR is a transmitter property, how much power it leaks into the adjacent channel. ACS is a receiver property, how well it rejects the adjacent channel. ACIR is the combination of the two and is what actually governs the interference between a specific transmitter and receiver on adjacent channels. You improve ACLR by cleaning up the transmitter and ACS by making the receiver more selective, but only the poorer of the two moves the ACIR much.
The interference reaching the victim in its own channel is the adjacent interferer power minus the ACIR. The carrier-to-interference ratio is then the wanted signal minus that interference, which works out to wanted minus interferer plus ACIR. Comparing the C/I against the protection ratio the victim needs gives the margin, and a negative margin means the adjacent system interferes.
Enough that the carrier-to-interference ratio meets the protection ratio the victim needs. Rearranging, the ACIR required is the protection ratio plus the interferer level minus the wanted level. The tool returns this directly and compares it against the ACIR you can achieve from your ACLR and ACS, so the shortfall becomes the filtering or guard band to add.
Systems integrators, spectrum coordinators and site engineers who coordinate adjacent-channel systems, rather than chipset or radio designers. Everything here is about applying ACLR, ACS and ACIR to a coordination problem: the combined figure, the resulting C/I and the protection it needs. It does not model the transmitter or receiver internals that set ACLR and ACS.
No. The calculator runs entirely in your browser. No coordination data is submitted to a server, which suits commercially confidential work and any environment where information security policy prohibits sending engineering data to third party services.
Free forever on a Standard account. No credit card.
