DIGITAL PHASE SHIFTER & ANALOG PHASE SHIFTER

Both Series, 77 and 78, comprise a family of eight solid-state PIN diode phase shifters covering the frequency range from 0.5 to 18 GHz in four bands: 0.5 to 2 GHz, 2 to 6 GHz, 4 to 12 GHz and 6 to 18 GHz. All models provide a full 360° range of phase shift and may also be used for frequency translation applications.

Each unit is an integrated assembly of an RF vector modulator and a driver circuit, consisting of a 10-bit D/A converter and a voltage buffer in the Series 77 digital units (see Fig. 1A) and a voltage converter and buffer in the Series 78 analog configuration (see Fig. 1 B).

The phase in the Series 77 is digitally controlled over a full 360° in 0.35° discrete steps. The voltage converter in the Series 78 consists of a 8 bit A/D converter followed by D/A converter, and converts a continuous analog input voltage into discrete steps of 1.41°.

• 0.5 to 18 GHz in four bands:
  1. 0.5 to 2 GHz
  2. 2 to 6 GHz
  3. 4 to 12 GHz
  4. 6 to 18 GHz
• 10 Bit digitally programmable (Series 77)
• Analog control (Series 78)
• High speed
• Guaranteed monotonicity

Phase Shift

Phase shift is achieved utilizing the RF vector modulator approach shown in Fig. 2. The 3 dB hybrid coupler divides the RF signal into two quadrature components which are then modulated in proportion to the sine and cosine of the desired phase shift. The signals are then combined in-phase to yield the phase-shifted output.

Frequency Translation (Serrodyning)

Special attention in the design of the units has been paid to those characteristics which affect their performance as frequency translators. These include minimizing PM-to-AM conversion, use of high slew rate drivers, and optimizing phase shift linearity with applied signal. As a result, carrier and sideband suppression levels of over 25 and 20 dB, respectively, are obtained in the main bands. The same carrier and sideband performance can be realized over the full stretch band when the internal frequency correction circuit is employed.

See Fig. 3 for input voltage control requirements for Series 77 and 78 when used as a frequency translator.

On special order, frequency translators can be provided for operation over reduced bandwidths with suppression levels of up to 35 dB. Consult the factory for special requirements.