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24 Threads found on Image Rejection Receiver
Few words about image rejection mixers can be found here: These mixers remove image frequencies but not the carrier or sideband frequencies. Removing carrier from IF will require it's restitution when demodulating signal. Using mixers with other concepts than superheterodyne is different thing
I think the statement in the pdf is wrong. The title of the article mentioned that the receiver is an SSB receiver. A direct conversion receiver will receive both sidebands ONLY IF both side bands are transmitted (AM case). But this is not the case of SSB, when only one of the side bands is transmitted. So, even if you want to receive the (...)
Hi ALL, in a low if receiver, if complex band pass filter is already implemented in analog BB, can the IQ imbalance calibration be adopted in digital domain to reject the image interference again? in my opinion, the IQ operation in CPF correlate the IQ signal, so it seems making a obstackle for the following IQ imbalance calibration in digital d
Dear All, Alternatively to image rejection mixers (IRM) or image filter, many wide band radios working in HF (0 to 30 MHz) band adopt the use of a 2nd or even 3rd conversion (double or triple heterodyne conversion) claimed by some folks to supress the image frequency and adjacent interferences. May be someone could (...)
To design this image filter, very important is the frequency spacing between RF and LO signal, which is the IF frequency. If the IF frequency is very low compared to RF frequency, would be a challenge to design an image reject filter with 40dB rejection.
A high first IF makes it easier to get good image rejection but is more difficult to get narrow bandwidth. A dual conversion receiver starts with a high first IF then converts it down to a lower frequency where it's bandwidth can be more easily tailored. Brian.
The big problem with Low IF receivers it the 1st image problem. You're relying on the I/Q matching of the mixers to cancel out the image, and it's tough to get more than 30 dB of image rejection. As the image for Low IF is pretty close in, you'll get hammerred with Adjacent/Alternate (...)
Do not confuse Sideband Suppression with image rejection. Direct Conversion receivers doesn't have an image frequency. In an IQ receiver, ideally the I and Q channels of the radio signal carry orthogonal, non-interfering, channels of information. Mismatch (imbalance) in the Gain or Phase of the I and Q (...)
I am not sure these arguments are entirely correct. The image is 2xIF from the desired frequency for one thing. For the FM band of 88-108MHz the image is not even in the band (which may be why an IF >10MHz was chosen). Also, there is some front end selectivity to provide image rejection. Keith
Usually, the first IF in a double heterodyne receiver is selected according to image rejection requirements and available input filter specifications. ADC parameters may matter in a digital receiver. All in all, there's too little information.
Hi, I'm in the system level design stage of a very low IF receiver (VLIF). Simulating the chain in ADS I get a SSB noise figure that is 3 dB higher than the corresponding Direct Conversion receiver (DCR). This is due to the noise at the image frequency. (f_IM = f_RF + 2*f_IF) I guess I should recover this 3 dB loss somewhere in the (...)
For calculating the image rejection ratio in ADS, we give two signals as system input, "original signal" and the "image signal + 10Khz ". In my receiver I am down converting my signal to 20Mhz. So for calculating IRR, What i have to do ? Shall i take peek difference of "20Mhz" and "20Mhz +10Khz" or 0Hz and 10Khz? 20
High-IF receiver needs High-Q filter for image rejection, so it isn't integratible. image rejection function of Low-IF and Zero-IF receiver is done in baseband, so no High-Q filters needed. So Low-IF and Zero-IF architecture is suit for integration with CMOS technology. For same application, (...)
Thanks for all the helpful replies. I have some more questions: I couldn't find any single-chip direct conversoin tuner for my frequency of interest. From your suggestions I decided to use Low-IF(Quadrature Demodulation) with the same setup as mentioned in the first post. I can use an IF of 6MHz for 2Mhz channel bandwidths. I don't want to go ov
the image rejection ratio : ratio between the gain of the desired channel to the gain of the image signal is ur IQ paths after the 1st mixer , then calculate the power before the I and Q spliting , of both desried and image signals check the image khouly
In low-IF, I/Q mismatch causes the degradation of the image rejection. Since the adjacent channel is the image frequency in low-if receiver if 1/2 bandwidth is choosen as low-if frequency, if I/Q mismatch(SSB, gain/phase imbalance in quadrature mixer) is -30dB and the adjacent channel is +30dB higher than the desired (...)
Brief answer e.g. Channel1 freq. = 900MHz Channel2 freq. = 900.025MHz Channel step = 25Khz IF = 21.4MHz Therefore VCO = 878.6MHz ( low side injection ) or VCO = 921.4MHz ( high side injection ) ACR : The ability of receiver to avoid the influrence of adjacent channel interference. e.g. Rx rece
You are avoiding two problems. image response has two aspects. One is the selectivity of the system before the mixer. The second is the presence of high power signals that may be at the image frequency. The usual advice for image rejection is to have the IF at least 10-20% of the RF. The more complex problem to (...)
What is the best image rejection currently available for a Low IF architecture receiver?
For the image-reject receiver, I've tried to calculate the IRR due to a departure in phase ΔΦ from the quadrature. It is assumed that the gain of each block is perfectly matched so only imperfect 90 phase shift has to be considered. The formula is expressed as IRR = 1+4cot(ΔΦ)^2 ≈ 4/(ΔΦ)^2 This formula is st