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Maxi/4R Series

The MAXI/4R Series of tunable filters provides 4-poles of filtering, for even better rejection than our standard MAXI-POLE filters. The chassis has been ruggedized to better handle the vibration and shock environments often encountered in customer applications (e.g. ground-mobile, airborne). The product line includes several standard designs in various frequencies to support almost any application.

  • Specifications
  • Performance
  • Numbering Table
  • Interface and Control Notes
  • Package Outline
  • Pinout and Ratings
Frequency Coverage (8 bands): 1.5 MHz to 1 GHz
Input/Output Impedance: 50 Ω
Inband RF Power Handling: 1 Watt (input)
Inband Third Order Intercept Point: +40 dBm (input)
Inband Second Order Intercept Point: +100 dBm (input)
Tuning Control: 8 bit parallel
Tuning Speed: 50 µS
DC Power: +5 VDC @ 10 to 1000 mA +100 VDC @ 2 mA
Operating Temperature Range: -40 to + 85°C
Center Frequency Drift: 80 PPM/°C

The following plots illustrate approximate performance (not representative of all frequency ranges):

Series    Frequency(MHz)    Insertion Loss    Connector Type   Options 
MAXI/4R 225-400 5 SMA AF
    1.5-4   1.5   SMA (Female)   A
    4-10   3  
    10-30         C
    30-90   7       F
    90-200   9        

 Available Options:
A. Internal DC-DC Converter (Eliminates need for high voltage supply. Requires additional 500 mA of 5 VDC current)
B. Serial Interface
C. Custom Frequency Bands (Specify START and STOP frequencies in MHz)
F. Filtered D-connector


1) Options may be limited to particular frequency bands and/or performance levels.
Consult factory for your application.
2) Filters are aligned and tested using a High Bias of +100 VDC unless otherwise
specified by the customer.
Frequency Tuning Address

Maxi-Pole Series filters utilize an eight-bit scheme for tune words to digitally control tuning of the center frequency. For further information on how to calculate tune words, please see the Frequency Tuning Address Application Note. There are 250 equally spaced tuning increments across each standard filter band, resulting in 251 tune words from 00000000 to 11111010. The last 5 tune words are reserved for housekeeping functions:

Bia Voltage Requirement

A bias voltage is required to reverse bias the PIN diodes used to tune the filter. Very little static current (less than 1 mA) is needed. A minimum of 30 Volts is recommended for proper filter operation, although in some instances voltages as low as 12 Volts will provide acceptable performance. As this voltage is increased, the power handling capability and intermodulation are improved as shown below. A bias voltage of +100 VDC is recommended for best results, and all filters are tuned and aligned this way from the factory unless otherwise specified by the customer. An internal low EMI supply, powered from the +5 VDC input, is available as an option.
Interface Options

The filter comes standard with an 8-bit parallel interface, although a serial interface can be specified as an option.

DC Control Interface Characteristics

Symbol  Parameter  Condition  Min  Max  Units 
VIL  Input Low Voltage  Control Signals except A0 - A7  0.0  0.2 Vcc 
VIH  Input High Voltage  Control Signals except A0 - A7  0.7 Vcc  Vcc 
VIL1  Input Low Voltage  A0 - A7  0.0  0.15Vcc 
VIH1  Input High Voltage  A0 - A7  0.7 Vcc  Vcc 

Switching Characteristics

Vcc = +5VDC, ± 10%; T= -40 to +85°C







Setup Time, A0-A7 to STB





Hold Time, A0-A7 from STB





STB High Time





STB Pulse Width





Strobe D well Time (From STB Falling edge to next STB Falling edge)





Access time from STB to f0




The filter is tuned within 50 µS to the frequency designated by the tuneword existing on the eight control bit lines when the STB line is brought low. Once strobed, data existing on the tune control lines is ignored until strobed again. Maximum strobe rate for frequencies above 10 MHz is 2 kHz, and below 10 MHz is typically 1 kHz. Consult the MaxiPole Selection Guide for the maximum strobe rate in each frequency band.

RF Power Handling Capability

The filters are designed to operate with RF input power levels up to 1 Watt (+30 dBm) inband (see curves above under Bias Voltage Requirement). Signals in the filter stopband up to 5 Watts at the input will not cause damage to the filter.

Temperature Effects

Over the –40 to +85°C temperature range, filters will exhibit a temperature drift of less than 80 PPM/°C, or a total of less than ±0.5% of the center frequency.

Parallel Interface

PIN#  REF DES  Description  Max Ratings 
A2 Tune Bit 2
+6 VDC 

A3 Tune Bit 3
A4 Tune Bit 4
A5 Tune Bit 5 
5 A6 Tune Bit 6
A7  Tune Bit 7 (MSB)
GND Ground  
Vcc +5VDC, ±10% +6 VDC 
GND Ground  
10  Vbb High Bias +125 VDC 
11  GND Ground  
12  GND  Ground   
13  STB Strobe +6 VDC
14  A0 Tune Bit 0 (LSB)
15  A1 Tune Bit 1

Serial Interface

PIN#  REF DES  Description  Max Ratings 
DO  Serial Data Out +6 VDC 
- No Connect
- No Connect
- No Connect
- No Connect
- No Connect
GND  Ground   
Vcc  +5 VCD, +-10%  +6 VDC 
GND  Ground   
10  Vbb High Bias +125 VDC 
11  GND  Ground   
12  GND  Ground   
13  STB  Strobe  +6 VDC 
14  SER CLK Serial Clock
15  DI  Serial Data In
Data is believed to be accurate. All data is subject to change without notice.