Av to digital rf converter

The audio modulator includes a pre-emphasis filter , a multi stage audio interpolator , and a complex frequency modulator The pre-emphasis filter has a high-pass filter like response. The pre-emphasis filter results in increased signal-to-noise ratio SNR. The multi stage audio interpolator is connected to the pre-emphasis filter to increase the sampling rate of the pre-emphasized audio signals. The complex frequency modulator is connected to the multi-stage audio interpolator to modulate the exponential carrier with the interpolated audio signal.

The frequency of the exponential carrier is programmable. The value to be programmed depends on the TV system targeted. Typical values of the audio carrier frequency are 4. The output frequency spectrum of the complex frequency modulator is shown in FIG. The video modulator includes a digital circuit , a group delay compensation filter , an IRE level adjustor , and a complex VSB filter Generally, the digital encoders take incoming video data at The digital circuit is used for up-sampling the incoming CVBS signal by a factor of 2, if the sampling rate of the incoming signal is The upsampling can be achieved by using a simple interpolation filter.

The group delay compensation filter is connected with the digital circuit for pre-correcting the non-linear phase characteristics of a receiver.

The group delay compensation filter is an all-pass filter with the group delay characteristics as defined in the ITU-R BT. The IRE level adjustor is connected with the group delay compensation filter for scaling and adding the output of the group delay compensation filter with pre-calculated values which are programmable. This operation is required to adjust the amplitude levels of the CVBS signal. The addition factor also contains the value that is required to be added to represent carrier addition at baseband.

The complex VSB filter is connected to the IRE level adjustor for generating a vestige of one of the sidebands and limiting the bandwidth of the other sideband in order to avoid video interference into the audio spectrum. Since the filter is complex in nature complex valued coefficients , the magnitude response is asymmetric across 0 Hz. The RF converter includes a complex adder , a complex frequency shifter , and a RF interpolator The complex adder includes two simple adders, which adds the frequency modulated audio signals from the audio modulator with the filtered output video signal from the video modulator The complex adder works at 27 MHz to form the base band TV signal.

The complex frequency shifter is connected to the complex adder for multiplying the base band TV signal with an exponential carrier value to shift the base band TV signal uni-directionally by the frequency of the exponential carrier. The complex frequency shifter works at 27 MHz sampling rate. The frequency of the exponential carrier determines the required channel frequency. Assume that a required channel carrier frequency is 62 MHz.

In order to bring the image at 54 MHz to 62 MHz, there is a need to shift the image by 8 MHz towards right, so in this case exponential carrier frequency of 8 MHz should be chosen. Now, assume that a required channel carrier frequency is 70 MHz. So, an exponential carrier frequency of 16 MHz will be chosen to shift the image at 54 MHz to 70 MHz, but this carrier can not be generated at a sampling rate of 27 MHz. After a complex multiplication, the video carrier also gets inserted automatically due to an initial DC addition in a video processor block.

The RF interpolator is connected to the complex frequency shifter for generating a modulator output at a higher sampling rate. The output samples after complex multiplication are passed through a zero-padder block The zero padder block inserts a sufficient number of logical 0s between two input samples.

These samples are then provided as input to a quadrature band pass filter to select the spectrum replica of interest containing the desired channel frequency. After the quadrature band pass filter, the resultant spectrum for a channel frequency of 64 MHz is shown in the FIG. The zero-padding block and the BPF can be merged together as a poly-phase structure in which each poly-phase structure effectively operates at 27 MHz only.

The output data rate of the BPF is the desired sample rate. The sample rate must be increased from 27 MHz to a higher value for generating an RF modulated output. The increased sample rate is a multiple of 27 MHz for simplicity in interpolation interpolation factor becomes an integer. For generating a VHF band output with channel carrier frequency less than MHz, the desired sample rate should be greater than MHz after allowing some guard band in the spectrum , which results in a large interpolation factor.

Both the band pass filters can be optimized to implement in a polyphase structure because of the zero-padder logic preceding them. For supporting UHF band up to 1. At step , input audio signals are processed to generate frequency modulated FM audio signals through an audio modulator. At step , input composite video base-band CVBS signals are processed to generate a filtered output video signal through a video modulator.

At step , the frequency modulated FM audio signals and the filtered output video signals are mixed to form the base band TV signals through a RF converter. Free shipping Free shipping Free shipping. Last one Last one Last one. Similar sponsored items. Seller assumes all responsibility for this listing. Item specifics. New: A brand-new, unused, unopened, undamaged item in its original packaging where packaging is Read more about the condition New: A brand-new, unused, unopened, undamaged item in its original packaging where packaging is applicable.

Packaging should be the same as what is found in a retail store, unless the item is handmade or was packaged by the manufacturer in non-retail packaging, such as an unprinted box or plastic bag. See the seller's listing for full details. See all condition definitions opens in a new window or tab. Does not apply. Does Not Apply.

Back to home page Return to top. Mouse over to Zoom - Click to enlarge. Have one to sell? Sell now - Have one to sell? Shop with confidence. Get the item you ordered or get your money back. Learn more - eBay Money Back Guarantee - opens in a new window or tab. Seller information. Contact seller Contact seller. Visit store Visit store. See other items See other items. Item Information Condition:. Bulk savings:. Buy 1. Sign in to check out Check out as guest. The item you've selected was not added to your cart.

Best Offer:. Make Offer. Add to Watchlist Unwatch. Watch list is full. Shipping help - opens a layer International Shipping - items may be subject to customs processing depending on the item's customs value.

Your country's customs office can offer more details, or visit eBay's page on international trade. Located in:. This amount is subject to change until you make payment. For additional information, see the Global Shipping Program terms and conditions - opens in a new window or tab This amount includes applicable customs duties, taxes, brokerage and other fees.

For additional information, see the Global Shipping Program terms and conditions - opens in a new window or tab. Estimated between Mon. This item has an extended handling time and a delivery estimate greater than 31 business days.

Please allow additional time if international delivery is subject to customs processing. Special financing available. See terms and apply now See terms and apply now for PayPal Credit - opens in a new window or tab. Any international shipping and import charges are paid in part to Pitney Bowes Inc.

Learn More - opens in a new window or tab International shipping and import charges paid to Pitney Bowes Inc. Learn More - opens in a new window or tab Any international shipping and import charges are paid in part to Pitney Bowes Inc. Learn More - opens in a new window or tab Any international shipping is paid in part to Pitney Bowes Inc.

Learn More - opens in a new window or tab. Sponsored items from this seller. Showing Slide 1 of 3.