Method and system for reducing radiated emissions from a communications channel
A communications channel may radiate energy undesirably, for example in the form of electromagnetic radiation, when a communication signal transmits over the communications channel. Processing the signal before and after transmission on the communications channel can reduce the level of radiated energy. Signal processing in advance of transmission over the communications channel can transform the communication signal into a waveform that has a reduced propensity to emit radiated energy during transmission over the communications channel. Exemplary signal transformations can involve applying either frequency-selective or broadband attenuation to the communication signal. Following transmission of the waveform over the communications channel, the original communication signal can be restored via reversing the signal transformation. The reverse transformation can comprise applying frequency-selective gain or broadband gain to the transmitted waveform.
1. A communication method comprising:
at a first end of a communication channel, receiving a data signal that has been distorted in shape and exhibits an intersymbol interference from the output of a low-pass filter at a second end of the communication channel, wherein a cutoff frequency of the low-pass filter is set to distort a shape of the data signal in comparison to an original signal at an input of the low-pass filter and to introduce the intersymbol interference, wherein the low-pass filter suppresses a frequency content above a threshold prior to transmission over the communication channel;
at the first end of the communication channel, processing the received data signal with an equalizer to restore the suppressed frequency content and a shape of the original signal, and to remove the intersymbol interference;
at the first end of the communication channel, applying amplification to the processed and received data signal; and
at the first end of the communication channel, detecting the amplified, processed, and received data signal with a receiver.
2. The communication method of claim 1 , wherein applying amplification comprises applying limiting amplification.
3. The communication method of claim 2 , wherein the processed and received data signal comprises noise, and wherein applying limiting amplification comprises reducing the noise.
4. The communication method of claim 1 , wherein the equalizer comprises a high-pass filter.
5. The communication method of claim 4 , wherein the high-pass filter attenuates frequencies that are below a threshold frequency and amplifies frequencies that are above the threshold frequency.
6. The communication method of claim 4 , wherein filtering the data signal with the low-pass filter and processing the received data signal with the equalizer collectively comprises providing an all-pass function over the frequency band of the data signal.
7. The communication method of claim 4 , wherein a transmitter disposed at the second end of the communication channel outputs the original signal to the low-pass filter, and wherein the processing of the received data signal with the equalizer transforms the received data signal back into the original signal.
8. A communication method comprising:
at a first end of a communication channel, receiving a data signal that has been distorted in shape and exhibits an intersymbol interference from the output of a low-pass filter at a second end of the communication channel, wherein a cutoff frequency of the low-pass filter is set to distort a shape of the data signal in comparison to an original signal at an input of the low-pass filter and to introduce the intersymbol interference, wherein the low-pass filter suppresses a frequency content above a threshold prior to transmission over the communication channel;
at the first end of the communication channel, processing the received data signal with a high-pass filter by restoring a shape of the original signal and removing the intersymbol interference;
at the first end of the communication channel, applying amplification to the processed and received data signal; and
at the first end of the communication channel, detecting the amplified, processed, and received data signal with a receiver.
9. The communication method of claim 8 , wherein applying amplification comprises applying limiting amplification.
10. The communication method of claim 9 , wherein the processed and received data signal comprises noise, and wherein applying limiting amplification comprises reducing the noise.
11. The communication method of claim 8 , wherein processing the received data signal with the high-pass filter comprises attenuating frequencies that are below a threshold frequency and amplifying frequencies that are above the threshold frequency.
12. The communication method of claim 8 , wherein the high-pass filter provides frequency selective gain that increases as a function of frequency.