Image Rejection Ratio Calculator

Image Rejection Ratio Formula:

\[ \rho = \frac{f_{img}}{F_{RF}} - \frac{F_{RF}}{f_{img}} \]

Image Rejection Ratio (ρ):

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1. What is Image Rejection Ratio?

Image Rejection Ratio is the ratio of the intermediate-frequency (IF) signal level produced by the desired input frequency to that produced by the image frequency. It measures a receiver's ability to reject unwanted image frequencies.

2. How Does the Calculator Work?

The calculator uses the Image Rejection Ratio formula:

\[ \rho = \frac{f_{img}}{F_{RF}} - \frac{F_{RF}}{f_{img}} \]

Where:

\( \rho \) — Image Rejection Ratio
\( f_{img} \) — Image Frequency (Hertz)
\( F_{RF} \) — Received Signal Frequency (Hertz)

Explanation: The formula calculates the ratio by comparing the image frequency to the received signal frequency in both direct and reciprocal forms.

3. Importance of Image Rejection Ratio

Details: A higher image rejection ratio indicates better receiver performance in rejecting unwanted image frequencies, which is crucial for clear signal reception and reducing interference in communication systems.

4. Using the Calculator

Tips: Enter both Image Frequency and Received Signal Frequency in Hertz. Both values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is considered a good Image Rejection Ratio?
A: Higher values indicate better performance. Typically, receivers aim for ratios above 40-60 dB for effective image rejection.

Q2: How does Image Frequency relate to Intermediate Frequency?
A: Image frequency is defined as the sum of received signal frequency and twice the intermediate frequency (fimg = FRF + 2×IF).

Q3: Why is image rejection important in receivers?
A: Effective image rejection prevents interference from unwanted signals that could distort or overwhelm the desired signal reception.

Q4: What factors affect Image Rejection Ratio?
A: Receiver design, filter quality, mixer performance, and local oscillator stability all contribute to the image rejection capability.

Q5: Can this ratio be negative?
A: Yes, the ratio can be negative when the received signal frequency is greater than the image frequency, though the absolute value is typically considered for performance measurement.