Single-Conversion DVB-H Tuner

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Unlike the tracking filter, it is not necessary to interpolate

notch filter settings for various operating frequencies.

When receiving channels below 725MHz in the presence

of cellular blockers, the TF_NTCH[3:0] bits should be pro-

grammed to the lower notch frequency that is stored in

the ROM table. When receiving channels above 725MHz

in the presence of cellular blockers the TF_NTCH[3:0]

bits can be programmed to the upper notch frequency

that is stored in the ROM table.

Baseband Filter and Tracking Filter

The MAX2165 includes programmable baseband and

tracking filters. The baseband filter bandwidth is con-

trolled through the BB_BW[3:0] bits in the Baseband

Control register (Table 12). The tracking filter’s balun fre-

quency can be programmed through the TF_BAL[3:0] in

the Tracking Filter register (Table 6).

Reading the ROM Table

To accommodate process variations, each part is factory

calibrated. During calibration, the best notch filter settings

for two different notch frequencies, the best balun set-

tings for 470MHz and 780MHz, and the best baseband

filter settings for 6MHz to 8MHz channels are determined.

These settings are stored in an on-chip ROM table that

must be read upon power-up and stored in the micro-

processor local memory (3 bytes total). Table 21 shows

the address and bits for each ROM table entry.

Each ROM table entry must be read using a two-step

process. First, the address of the bits to be read must be

programmed into the TFA[3:0] bits in the ROM Table

Address register (Table 15).

Once the address has been programmed, the data

stored in that address is transferred to the TRF[7:0] bits in

the ROM Table Data Readback register (Table 17). The

ROM data at the specified address can then be read

from the TRF[7:0] bits and stored in the microprocessor’s

local memory.

Interpolating Balun Coefficients

The TF_BAL[3:0] bits must be reprogrammed for each

channel frequency to optimize performance over the

band. The values given for 780MHz and 470MHz in the

ROM table can be used to interpolate the optimal coeffi-

cients for any other frequency using the equation:

where:

Value = decimal value of the optimal TF_BAL[3:0] set-

ting for desired channel frequency, f

BAL_L = decimal value of the optimal TF_BAL[3:0] set-

ting for 470MHz as read from the ROM table

BAL_H = decimal value of the optimal TF_BAL[3:0] set-

ting for 780MHz as read from the ROM table

f = desired channel frequency in MHz

Example: Assume the TF_BAL[3:0] values read from

the ROM table for 780MHz and 470MHz are 14 and 2,

respectively, and we wish to program the balun for

operation at an RF frequency of 620MHz.

Using the previous equation, we can calculate:

Rounding to the nearest integer value gives us 8; there-

fore, when operating at 620MHz, the TF_BAL[3:0] bits in

the Tracking Filter register must be programmed to 1000.

Setting the Baseband Filter

The MAX2165 baseband filter is freely programmable

over a wide range of 3dB cutoff frequencies from

approximately 3.0MHz to 4.3MHz, but the exact cutoff

frequency varies from part-to-part due to manufactur-

ing process variations. To avoid requiring the user to

find the correct setting, the best setting for a 3.9MHz

cutoff frequency (i.e., 8MHz wide DVB-T/-H channels)

is determined by Maxim and stored on a ROM table on

every chip. The user needs to read this value from the

ROM table entry 0x3 (see Table 21) and write it back

into register 0xA bits BB_BW[3:0] (see Table 12) upon

powering up the MAX2165.

Baseband Filter Setting for RF Channels Other than

8MHz or Modulation Types Other than DVB-T

If a different cutoff frequency than 3.9MHz is desired, a

fixed value per Table 22 can be added or subtracted

from the number read-out of the ROM table, before

writing it back into the corresponding MAX2165 register.

This way the factory calibration is still utilized and the

resulting cutoff frequency is still reasonably accurate.

Value at 620MHz 2 (14 - 2) x

620MHz 470MHz

780MHz 470MHz

=+

−

−

= 78

.

Value BAL_L (BAL_H BAL_L) x

f

470MHz

780MHz 470MHz

=+

−

−

−