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diff --git a/fpga/usrp3/top/x400/rf/common/PkgRf.vhd b/fpga/usrp3/top/x400/rf/common/PkgRf.vhd
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+--
+-- Copyright 2021 Ettus Research, a National Instruments Brand
+--
+-- SPDX-License-Identifier: LGPL-3.0-or-later
+--
+-- Module: PkgRf
+--
+-- Description:
+--
+--   This package has some type definition and functions used in the RF data
+--   chain.
+--
+
+library IEEE;
+  use IEEE.std_logic_1164.all;
+  use IEEE.numeric_std.all;
+
+package PkgRf is
+
+  -- DDC sample data out width.
+  constant kDdcDataOutWidth  : natural := 17;
+  -- Each sample is padded in MSB with 7 extra bits of zero to byte align.
+  constant kDdcDataWordWidth : natural := kDdcDataOutWidth+7;
+  -- DUC sample data out width.
+  constant kDucDataOutWidth  : natural := 18;
+  -- Each sample is padded in MSB with 6 extra bits of zero to byte align.
+  constant kDucDataWordWidth : natural := kDucDataOutWidth+6;
+  -- Saturated data output width.
+  constant kSatDataWidth     : natural := 16;
+  -- ADC sample resolution.
+  constant kAdcSampleRes     : natural := 16;
+
+  subtype Sample18_t is    signed(17 downto 0);
+  subtype Sample17_t is    signed(16 downto 0);
+  subtype Sample16_t is    signed(15 downto 0);
+  subtype Sample16slv_t is std_logic_vector(15 downto 0);
+
+  type Samples16_t is array(natural range<>) of Sample16_t;
+  type Samples17_t is array(natural range<>) of Sample17_t;
+  type Samples18_t is array(natural range<>) of Sample18_t;
+
+  -- These constants have the largest and smallest 18-bit, 17-bit, and 16-bit
+  -- signed values.
+  constant kLargest18  : Sample18_t := to_signed(2**17 - 1, 18);
+  constant kSmallest18 : Sample18_t := to_signed(-2**17, 18);
+  constant kLargest17  : Sample17_t := to_signed(2**16 - 1, 17);
+  constant kSmallest17 : Sample17_t := to_signed(-2**16, 17);
+  constant kLargest16  : Sample16_t := to_signed(2**15 - 1, 16);
+  constant kSmallest16 : Sample16_t := to_signed(-2**15, 16);
+
+  function Saturate(s : signed ) return Sample16_t;
+  function to_stdlogicvector(d : Samples16_t) return std_logic_vector;
+  function to_Samples16(d : std_logic_vector) return Samples16_t;
+  function to_Samples17(d : std_logic_vector) return Samples17_t;
+  function to_Samples18(d : std_logic_vector) return Samples18_t;
+  -- Shift the ADC sample to the left by 1 bit.
+  function Gain2x(d : std_logic_vector) return std_logic_vector;
+  function Gain2x(s : Samples16_t) return Samples16_t;
+  --synopsys translate_off
+  function tb_saturate(s: std_logic_vector) return Sample16slv_t;
+  --synopsys translate_on
+
+end package PkgRf;
+
+
+package body PkgRf is
+
+  -- Function to saturate any signed number greater then 16 bits.
+  -- A saturated 16-bit data is returned.
+  function Saturate ( s : signed) return Sample16_t is
+  begin
+    if s > kLargest16 then
+      return kLargest16;
+    elsif s < kSmallest16 then
+      return kSmallest16;
+    else
+      return resize(s, 16);
+    end if;
+  end function Saturate;
+
+  -- This function will convert 16 bit signed array into a single
+  -- std_logic_vector.
+  function to_stdlogicvector(d : Samples16_t) return std_logic_vector is
+    -- This alias is used to normalize the input vector to [d'length-1 downto 0]
+    alias normalD : Samples16_t(d'length-1 downto 0) is d;
+    variable rval : std_logic_vector(d'length * 16 - 1 downto 0);
+    constant dataWidth : natural := Sample16_t'length;
+  begin
+    for i in normalD'range loop
+      rval(i*dataWidth + dataWidth-1 downto i*dataWidth)
+        := std_logic_vector(normalD(i));
+    end loop;
+    return rval;
+  end function to_stdlogicvector;
+
+  -- This function will convert a std_logic_vector into an array of 18 bit
+  -- signed array.  The input std_logic_vector has data packed in 24 bits. But
+  -- only 18 bits has valid data and remaining 6 MSB bits are padded with
+  -- zeros.
+  function to_Samples18(d : std_logic_vector) return Samples18_t is
+    -- This alias is used to normalize the input vector to [d'length-1 downto 0]
+    alias normalD : std_logic_vector(d'length-1 downto 0) is d;
+    variable rval : Samples18_t(d'length / kDucDataWordWidth - 1 downto 0);
+  begin
+    --synopsys translate_off
+    assert (((d'length) mod kDucDataWordWidth) = 0)
+      report "Input to the function to_Samples18 must be a multiple of kDucDataWordWidth"
+      severity error;
+    --synopsys translate_on
+    for i in rval'range loop
+      rval(i) := Sample18_t(normalD(i*kDucDataWordWidth + Sample18_t'length-1
+                                    downto i*kDucDataWordWidth));
+    end loop;
+    return rval;
+  end function to_Samples18;
+
+  -- This function will convert a std_logic_vector into an array of 16 bit
+  -- signed array. The input std_logic_vector has data packed in 16 bits. But
+  -- only 15 bits has valid data and the uper two bits only have the signed
+  -- bit.
+  function to_Samples16(d : std_logic_vector) return Samples16_t is
+    -- This alias is used to normalize the input vector to [d'length-1 downto 0]
+    alias normalD : std_logic_vector(d'length-1 downto 0) is d;
+    variable rval : Samples16_t(d'length / kAdcSampleRes - 1 downto 0);
+  begin
+    --synopsys translate_off
+    assert (((d'length) mod kAdcSampleRes) = 0)
+      report "Input to the function to_Samples16 must be a multiple of kAdcSampleRes"
+      severity error;
+    --synopsys translate_on
+    for i in rval'range loop
+      rval(i) := Sample16_t(normalD(i*kAdcSampleRes + Sample16_t'length-1
+                                    downto i*kAdcSampleRes));
+    end loop;
+    return rval;
+  end function to_Samples16;
+
+  -- This function will convert a std_logic_vector into an array of 19 bit
+  -- signed array. The input std_logic_vector has data packed in 24 bits. But
+  -- only 17 bits has valid data and remaining 7 MSB bits are padded with
+  -- zeros.
+  function to_Samples17(d : std_logic_vector) return Samples17_t is
+    -- This alias is used to normalize the input vector to [d'length-1 downto 0]
+    alias normalD : std_logic_vector(d'length-1 downto 0) is d;
+    variable rval : Samples17_t(d'length / kDdcDataWordWidth - 1 downto 0);
+  begin
+    --synopsys translate_off
+    assert (((d'length) mod kDdcDataWordWidth) = 0)
+      report "Input to the function to_Samples17 must be a multiple of kDdcDataWordWidth"
+      severity error;
+    --synopsys translate_on
+    for i in rval'range loop
+      rval(i) := Sample17_t(normalD(i*kDdcDataWordWidth + Sample17_t'length-1
+                                    downto i*kDdcDataWordWidth));
+    end loop;
+    return rval;
+  end function to_Samples17;
+
+  -- Function to shift the sample to the left by one bit and effectively
+  -- multiply by 2.
+  function Gain2x(s : Samples16_t) return Samples16_t is
+    variable rval : Samples16_t(s'range);
+  begin
+    for i in rval'range loop
+      rval(i) := s(i)(kAdcSampleRes-2 downto 0) & '0';
+    end loop;
+    return rval;
+  end function Gain2x;
+
+  function Gain2x (d : std_logic_vector) return std_logic_vector is
+  begin
+    return to_stdlogicvector(Gain2x(to_Samples16(d)));
+  end function;
+
+  --synopsys translate_off
+  ---------------------------------------------------------------
+  -- Function below this comment is used only for testbench.
+  ---------------------------------------------------------------
+  -- This function does saturation of a signed number in std_logic_vector data
+  -- type. The current implementation supports only 17 or 18 bit signed
+  -- number.
+  function tb_saturate(s: std_logic_vector) return Sample16slv_t is
+    -- This alias is used to normalize the input vector to [s'length-1 downto 0]
+    alias normalS : std_logic_vector(s'length-1 downto 0) is s;
+    variable rval : Sample16slv_t;
+    constant len  : integer := s'length;
+  begin
+
+    -- If 2 MSBs = 00, output <= input without MSB, e.g. positive number < 1
+    -- If 2 MSBs = 01, output <= 0.111111111111111, e.g. positive number >= 1
+    -- If 2 MSBs = 10, output <= 1.000000000000000, e.g. negative number < -1
+    -- If 2 MSBs = 11, output <= input without MSB, e.g. negative number >= -1
+    if len = kDdcDataOutWidth then
+      if normalS(len-1 downto len-2) = "01" then
+        rval := "0111111111111111";
+      elsif normalS(len-1 downto len-2) = "10" then
+        rval := "1000000000000000";
+      else
+        rval := normalS(len-2 downto 0);
+      end if;
+
+    -- If 3 MSBs = 000, output <= input without MSB, e.g. positive number < 1
+    -- If 3 MSBs = 0x1/01x, output <= 0.111111111111111, e.g. positive number >= 1
+    -- If 3 MSBs = 1x0/10x, output <= 1.000000000000000, e.g. negative number < -1
+    -- If 3 MSBs = 111, output <= input without MSB, e.g. negative number >= -1
+    else -- len = kDucDataOutWidth
+      if normalS(len-1) = '0' and normalS(len-2 downto len-3) /= "00" then
+        rval := "0111111111111111";
+      elsif (normalS(len-1 downto len-3) = "000") or
+            (normalS(len-1 downto len-3) = "111") then
+        rval := normalS(len-3 downto 0);
+      else
+        rval := "1000000000000000";
+      end if;
+    end if;
+    return rval;
+  end function tb_saturate;
+  --synopsys translate_on
+
+end package body;